Typical uses. Simple, highly stressed castings of uniformDensity. 1.83 g/cm (0.066 lb/in. ) at 20 pdf

Tin is structurally a weak metal; therefore, when it is used in bearing applications it is alloyed with copper and antimony for increased hardness, tensile strength, and fatigue resistan

Typical uses. Simple, highly stressed castings of uniform

cross section High in cost Intricate castings subject to

microporosity and cracking due to shrinkage Not

readily welded Sometimes used in the artificially aged

condition (T5 temper) but usually in the solution-heat

treated and artificially aged condition (T6 temper) to

develop properties fully

Mechanical Properties

Tensile properties. T6 temper: tensile strength, 310 MPa

(45 ksi); yield strength, 195 MPa (28 ksi); elongation in

Coefficient of linear thermal expansion. 27.0 μm/m · K (15.0 μin./in · °F) at 20 to 200 °C (68 to 390 °F)

Tin and Tin Alloys

Revised by William B Hampshire, Tin Research Institute, Inc

Introduction

TIN was one of the first metals known to man Throughout ancient history, various cultures recognized the virtues of tin

in coatings, alloys, and compounds, and the use of the metal increased with advancing technology Today, tin is an important metal in industry even though the annual tonnage used is much smaller than those of many other metals One reason for the small tonnage is that, in most applications, only very small amounts of tin are used at a time

Tin Production and Consumption

Tin is produced from both primary and secondary sources Secondary tin is produced from recycled materials (see the article "Recycling of Nonferrous Alloys" in this Volume) Figure 1 shows the consumption of primary and secondary tin

in the United States during recent years Figure 2 shows 1988 data for the relative consumption of tin in the United States

by application

Fig 1 U.S consumption of primary and secondary tin in recent years

Fig 2 Relative consumption of tin in the United States by application 1988 data Source: U.S Bureau of Mines

Primary Production. Tin ore generally is centered in areas far distant from centers of consumption The leading producing countries (excluding the USSR and China) are, in descending order, Brazil, Indonesia, Malaysia, Thailand, Bolivia, and Australia (1988 totals) These countries supply over 85% of total world production

tin-Cassiterite, a naturally occurring oxide of tin, is by far the most economically important tin mineral The bulk of the world's tin ore is obtained from low-grade placer deposits of cassiterite derived from primary ore bodies or from veins associated with granites or rocks of granitic composition

Primary ore deposits can contain very low percentages of tin (0.01%, for example), and thus large amounts of soil or rock must be worked to provide recoverable amounts of tin minerals Unlike ores of other metals, cassiterite is very resistant to chemical and mechanical weathering, but extended erosion of primary lodes by air and water has resulted in deposition of the ore as eluvial and alluvial deposits

Underground lode deposits of tin ores are worked by sinking shafts and driving adits, and the rock is broken from the working face by drilling and blasting Cassiterite is recovered from eluvial and alluvial deposits by dredging, gravel pumping, and hydraulicking In open-pit mining, a much less widely employed mining method, mechanical and manual methods are used to move tin-bearing materials After ball mill concentration of the ore, a final culling is provided at dressing stations

The final concentrates, which contain 70 to 77% tin, are then sent to the smelter, where they are mixed with anthracite and limestone This charge is heated in a reverberatory furnace to about 1400 °C (2550 °F) to reduce the tin oxide to impure tin metal, which is again heated in huge cast iron melting pots to refine the metal Steam or compressed air is introduced into the molten metal, and this treatment, plus addition of controlled amounts of other elements that combine with the impurities, results in tin of high purity (99.75 to 99.85%) This high-purity tin often is treated again by liquating

or electrolytic refining, which provides tin with a purity level approaching 99.99%

After the tin is refined, it is cast into ingots weighing 12 to 25 kg (26 to 56 lb) or bars in weights of 1 kg (2 lb) and upwards Tin normally is sold by brand name, and the choice of brand is determined largely by the amounts of impurities that can be tolerated in each end product High-purity brands of tin may contain small amounts of lead, antimony, copper, arsenic, iron, bismuth, nickel, cobalt, and silver Total impurities in commercially pure tin rarely exceed 0.25%

Tin in Coatings

Tinplate. The largest single application of tin worldwide is in the manufacture of tinplate (steel sheet coated with tin), which accounts for about 40% of total world tin consumption Since 1940, the traditional hot dip method of making tinplate has been largely replaced by electrodeposition of tin on continuous strips of rolled steel Electrolytic tinplate can

be produced with either equal or unequal amounts of tin on the two surfaces of the steel base metal Nominal coating thicknesses for equally coated tinplate range from 0.38 to 1.5 μm (15 to 60 μin.) on each surface The thicker coating on tinplate with unequal coatings (differential tinplate) rarely exceeds 2.0 μm (80 μin.) Tinplate is produced in thicknesses from 0.15 to 0.60 mm (0.006 to 0.024 in.)

Over 90% of world production of tinplate is used for containers (tin cans) Traditional tinplate cans are made of three pieces of tin-coated steel: two ends and a body with a soldered side seam Innovations in can manufacture have produced two-piece cans made by drawing and ironing Tinplate cans find their most important use in the packaging of food

products, beer, and soft drinks, but they are also used for holding paint, motor oil, disinfectants, detergents, and polishes Other applications of tinplate include signs, filters, batteries, toys, and gaskets, and containers for pharmaceuticals, cosmetics, fuels, tobacco, and numerous other commodities

Electroplating accounts for one of the major uses of tin and tin chemicals Tin is used in anodes, and tin chemicals are used in formulating various electrolytes and for coating a variety of substrates Tin electroplating can be performed in either acid or alkaline solutions Sodium or potassium stannates form the bases of alkaline tinplating electrolytes that are very efficient and capable of producing high-quality deposits Advantages of these alkaline stannate baths are that they are not corrosive to steel and that they do not require additional agents Acid electrotinning solutions operate at higher current densities and higher plating rates and require additions of organic compounds

A number of alloy coatings can be electroplated from mixed stannate-cyanide baths, including coatings of tin-zinc and tin-cadmium alloys and a wide range of tin-copper alloys (bronzes) The bronzes range in tin content from 7 to 98% Red bronze deposits contain up to 20% tin; high-tin bronzes, called speculum, usually contain about 40% tin

Tin-nickel and tin-lead electrodeposits are plated from acid electrolytes and are important coatings for printed circuits and electronic components Tin-cobalt plate is used in applications requiring an attractive finish and good corrosion

Hot dip tin coatings are used both on wire for component leads and on food-handling and food-processing equipment In addition, hot dip tin coatings are used to provide the bonding layer for the babbitting of bearing shells

• U.S government specification QQT-371, Grade A (99.75% Sn)

• British specification BS 3252, Grade T (99.8% Sn)

• German specification DIN 1704, Grade A2 (99.75% Sn)

Table 1 summarizes selected physical, thermal, electrical, and optical properties of pure tin Further information is contained in the article "Properties of Pure Metals" in this Volume General applications of Grade A tin include tinplate foil, collapsible tubes, block tin products, and pewter

Table 1 Physical, thermal, electrical, and optical properties of commercially pure tin

Volume change on phase transformation, % ~27%

Thermal properties

Melting point, °C ( °F) 231.9 (449.4)

Phase transformation temperature on cooling (β phase to α phase), °C (°F) 13.2 (55.8)

Latent heat of phase transformation, J/g (Btu/lb) 17.6 (7.57)

Latent heat of vaporization, kJ/g (Btu/lb) 2.4 (1.03 × 103)

(a) T, temperature in degrees Kelvin

Mechanical Properties. Typical tensile properties of commercially pure tin are given in Table 2 Hardness and elasticity values are given in Table 1

Table 2 Tensile properties of commercially pure tin

Temperature Yield strength

°C °F MPa ksi

Elongation

in 25 mm (1 in.), %

Reduction in area, %

Strained at 0.2 mm/m · min (0.0002 in/in · min)

-160 -256 90.3 13.10 15 10

Note: It is uncertain if the inconsistencies among these data are due to differences in purity or the difference in straining rate

Creep Characteristics Like lead, tin is subject to creep deformation and rupture even at room temperature

Consequently, tensile strength may not be an important design criterion because creep rupture can occur at stresses even below the yield strengths in Table 2 For example, one series of tests on a commercially pure tin resulted in the following creep characteristics at room temperature:

Initial stress

MPa psi

Time, days

2.772 402.1 79 132

3.227 468.1 21* 119

4.214 611.2 4.6 105

7.069 1025.2 0.5* 78

Fatigue Strength Rotating-cantilever fatigue tests on a commercially pure tin resulted in fatigue strength levels of 2.9

MPa (430 psi) for 107 cycles at 15 °C (59 °F) and 2.6 MPa (380 psi) for 108 cycles at 100 °C (212 °F) Because creep deformation of tin occurs at room temperature, fatigue strengths may be influenced by creep-fatigue interaction and thus may depend on the frequency and/or waveform of stress cycling

Impact Strength Charpy V-notch tests on commercially pure tin at various temperatures resulted in the following

Temperature Logarithmic decrement

°C °F Polycrystalline Single crystals

corrosion of tin is given in Corrosion, Volume 13 of ASM Handbook, formerly 9th Edition Metals Handbook

Table 3 Resistance of tin to specific corroding agents

Corrosive agent Resistance Remarks

Acid, acetic Slight attack Increased by air

Acid, butyric Resistant

Acid, citric Moderate attack At water line

Acids, fatty Moderate attack

Acid, hydrochloric Severe attack In presence of air

Acid, hydrofluoric Severe attack In presence of air

Acid, lactic Moderate attack Increased by air

Acid, nitric Severe attack

Acid, oxalic Moderate attack

Acid, phosphoric Resistant

Acid, salts Severe attack Air present

Acid, sulfuric Severe attack (b)

Acid, tartaric Slight attack

Bromine Severe attack

Carbon tetrachloride Resistant

Chlorine Severe attack

Iodine Severe attack

Motor fuel Resistant

Petroleum products Resistant

Potassium hydroxide Severe attack Increased by air

Sodium carbonate Slight attack

Sodium hydroxide Severe attack Increased by air

Water, distilled Resistant

Water, sea Slight attack

(a) Most corrosive of common organic acids

(b) Increased with concentration and in the presence of air

Applications of Unalloyed Tin. There are only a few applications where tin is used unalloyed with other metals Unalloyed tin is the most practical lining material for handling-purity water in distillation plants because it is chemically inert to pure water and will not contaminate the water in any way

In the manufacture of plate glass, the molten glass is fed from the furnace onto the surface of a molten tin bath, which is protected from oxidation by an atmosphere that contains nitrogen and some hydrogen The natural forces of surface tension and gravity within the bath ordinarily produce plate glass about 6 mm (1

8 in.) thick, but the thickness of the glass can be varied by adjusting the speed at which the molten glass is drawn from the float bath and the temperature of the tin With this process, glass ribbons are formed with flat and parallel surfaces The surfaces of the glass are so smooth that surface polishing is not required

Powder Applications. Much of the supply of tin powders is used in making sintered bronze or sintered iron parts However, tin powders are also increasingly employed in making paste solders and creams used in the plumbing and electronic manufacturing industries Tin and tin alloy powders find minor uses in sprayed coatings for food-handling equipment, metallizing of nonconductors, and bearing repairs Tin particles can also be used in food can lacquers to decrease the dissolution of iron and any exposed lead-base solder by the food product

Additions of 2% tin powder and 3% copper powder aid the sintering of iron compacts The tin provides a point phase, which in turn provides diffusion paths for the iron Iron-tin-copper compacts sintered at 950 °C (1740 °F) have mechanical properties comparable to those of iron-copper powder metallurgy parts containing 7 to 10% Cu sintered

low-melting-at 1150 °C (2100 °F) In addition, closer control of finished dimensions is afforded by the iron-tin-copper mixture, and this control results in improved quality and cost effectiveness

Sintered compacts made from mixtures of iron and tin-lead solder powders are suitable for certain low-stress engineering applications Warm compressing of these compacts (at 450 °C, or 840 °F) provides cohesion of the iron solder mixtures but does not recrystallize the iron powder; therefore, any work hardening obtained during compaction is retained Different properties can be obtained in the pressed-and-sintered compacts by varying the pressing conditions and the relative amounts of the iron and solder powders

Tin in Chemicals

The manufacture of inorganic and organic chemicals containing tin constitutes one of the major uses of metallic tin The use of tin compounds has grown so rapidly over the past quarter century that the tin chemicals industry has been transformed from one based mainly on recovered secondary tin to one that consumes significant amounts of primary ingot tin

Tin chemicals are used for such widely diversified applications as electrolyte solutions for depositing tin and its alloys; pigments and opacifiers for ceramics and glazes; catalysts and stabilizers for plastics; pesticides, fungicides, and antifouling agents in agricultural products, paints, and adhesives; and corrosion-inhibiting additives for lubricating oils

Solders

Solders account for the largest use of tin in the United States (Fig 2) Tin is an important constituent in solders because it wets and adheres to many common base metals at temperatures considerably below their melting points Tin is alloyed with lead to produce solders with melting points lower than those of either tin or lead (see the article "Lead and Lead Alloys" in this Volume) Small amounts of various metals, notably antimony and silver, are added to tin-lead solders to increase their strength These solders can be used for joints subjected to high or even subzero service temperatures

Solder compositions and the applications of joining by soldering are many and varied (Table 4) Commercially pure tin is used for soldering side seams of cans for special food products and aerosol sprays The electronics and electrical industries employ solders containing 40 to 70% Sn that provide strong and reliable joints under a variety of environmental conditions High-tin solders are used for joining parts of electrical apparatuses because their electrical conductivity is higher than that of high-lead solders High-tin solders are also used where lead may be a hazard, for example, in contact with food-stuffs or in potable-water plumbing applications

Table 4 Applications, specifications, and nominal compositions of selected tin-base solder materials

temperature

Solidus temperature

Common

name

ASTM Government British German

Nominal composition,

%

°C °F °C °F

Typical applications

Commercially

pure tin

B 339, Grade

A

QQ-T-371, Grade A

BS

3252, Grade

T

DIN

1704, Grade A2

(a) Soldering

sideseams of cans for foods or aerosols

Antimonial-tin

solder

B 32, Grade S65

95 Sn, 5 Sb 240 464 234 452 Soldering of

electrical equipment, joints

in copper tubing, and cooling coils for refrigerators Resistant to SO2

Tin-silver

solder

B 32, Grade Sn95

95 Sn, 5 Ag 245 473 221 430 Soldering of

components for electrical and high-temperature service

Tin-silver

eutectic alloy

B 32, Grade Sn96

QQ-S-571, Grade Sn96

96 Sn, 3.5

Ag

221 430 221 430 Popular choice

with properties similar to those of ASTM B 32, Grade Sn95

Soft solder

(70-30 solder)

B 32, Grade Sn70

QQ-S-571, Grade Sn70

QQ-S-571, Grade Sn63

DIN

1707, LSn 63Pb

63 Sn, 37 Pb 183 361 183 361 Lowest-melting

(eutectic) solder for electronics

Soft solder

(60-40 solder)

B 32, Grade Sn60

QQ-S-571, Grade Sn60

BS 219, Grade

K

DIN

1707, LSn 60Pb(Sb)

60 Sn, 40 Pb 190 374 183 361 Solder for

electronic and electrical work, especially mass soldering of printed circuits

(a) See the section "Pure Tin" in this article for minimum tin contents

General-purpose solders (50Sn-50Pb and 40Sn-60Pb) are used for light engineering applications, plumbing, and sheet metal work Lower-tin solders (20 to 35% Sn, balance Pb) are used in joining cable and in the production of automobile radiators and heat exchangers Some solders are used to fill crevices at seams and welds in automotive bodies, thereby providing smooth joints and contours

Tin-zinc solders are used to join aluminum Tin-antimony and tin-silver solders are employed in applications requiring joints with high creep resistance, and in applications requiring a lead-free solder composition, such as potable-water plumbing Also, tin solders that contain 5% Sb (or 5% Ag) are suitable for use at higher temperatures than are the tin-lead

solders Further information on solders is provided in Ref 1 and in Welding, Brazing, and Soldering, Volume 6 of the ASM Handbook

Impurities in solders can affect wetting properties, flow within the joint, melting temperature of the solder, strength capabilities of joints, and oxidation characteristics of the solder alloys The most common impurity elements and their principal levels and effects are discussed below

Aluminum Traces of aluminum in a tin-lead solder bath can seriously affect soldering qualities More than 0.005% Al

can cause grittiness, lack of adhesion, and surface oxidation of the solder alloy A deterioration in the surface brightness

of a molten bath sometimes is an indication of the presence of aluminum

Antimony is slightly detrimental to wetting properties, but it can be used as an intentional additional for strengthening

As an impurity, antimony tends to reduce the effective spread of a solder alloy High-lead solder specifications usually require a maximum limit of 0.5% Sb The general rule is that antimony should not exceed 6% of the tin content, although

in some applications this rule can be invalid In various high-lead solders (such as Sn40B, Sn30B, Sn35B, Sn25B, and Sn20B in ASTM B 32), the presence of antimony is used to ensure that a transformation from βtin to α tin does not take place Such a transformation would result in a volume change and a drastic loss in solder strength

Arsenic A progressive deterioration in the quality of the solder is observed with increases in arsenic content As little as

0.005% As induces some dewetting, and dewetting becomes more severe as the percentage of arsenic is increased to 0.02% Arsenic levels should be kept within this range At the maximum allowable level of 0.03%, arsenic can cause dewetting problems when soldering brass

Bismuth Low levels of bismuth in the solder alloy generally do not cause any difficulties, although some discoloration

of soldered surfaces occurs at levels above 0.5%

Cadmium A progressive decrease in wetting capability occurs with additions of cadmium to tin-lead solders While

there is no significant change in the molten appearance, small amounts of cadmium can increase the risk of bridging and icicle formation in printed circuits For this reason, and for health reasons, cadmium levels should be kept to a minimum

Copper Although copper levels above about 0.25% can cause grittiness of solder, for the most part, the role of copper as

a solder contaminant appears to be variable and related to the particular product A molten tin-lead solder bath is capable

of dissolving copper at a high rate, and the level of copper in the bath can easily reach 0.3% Copper in liquid solder does not appear to have any deleterious effect upon the wetting rate or joint formation Excess copper settles to the bottom of a solder bath as an intermetallic compound sludge New solder alloy allows a maximum copper content of 0.08%

Iron and nickel are not naturally present in solder alloy The presence of iron-tin compounds in tin-lead solders can be

identified as a grittiness Generally, iron is limited to a maximum of 0.02% in new solder There are no specification limits for nickel, but levels as low as 0.02% can produce some reduction in wetting characteristics Iron levels above about 0.1% cause grittiness of solder

Phosphorous and Sulfur Phosphorous at a level of 0.01% is capable or producing dewetting and some grittiness At

higher levels, surface oxidation occurs, and some identifiable problems such as grittiness and dewetting become readily discernible Sulfur causes grittiness in solders at a very low level and should be held to 0.001% Discrete particles of tin-sulfide can be formed Both of these elements are detrimental to good soldering

Zinc The ASTM new solder alloy specification states that zinc content must be kept to a maximum of 0.005% in tin-lead

solders At this maximum limit, even with new solders in a molten bath, some surface oxidation can be observed, and oxide skins may form, encouraging icicles and bridging Up to 0.01% Zn has been identified as the cause of dewetting on copper surfaces Excessive zinc causes oxidation of solder to be more noticeable

The combined effects of the above impurity elements can be significant Excessive contamination in solder baths or

dip pots generally can be identified through surface oxidation, changes in the product quality, and the appearance of grittiness or frostiness in joints made in this bath A general sluggishness of the solder also may indicate excessive impurities In addition to analysis, experience with solder bath operation is helpful in determining the point at which the material should be renewed for good solder joint production The ASTM solder specifications, which specify maximum allowable impurity concentrations, are useful when purchasing solder for general use (Table 5) In particular applications, specific contaminants or a combination of elements may be detrimental to a particular soldered product On occasion, determining a revised or limited specification for solder materials is required

Table 5 Impurity limits in ASTM specifications for the tin-base solders listed in Table 4

Impurity limits, % (a)

Tin-silver solder 95 Sn, 5 Ag 0.12

4.4-4.8 0.005 0.01 0.15 0.005 0.08 0.02 0.10 0.005

Tin-silver eutectic

alloy

96 Sn, 3.5 Ag 0.12

3.4-3.8 0.005 0.01 0.15 0.005 0.08 0.02 0.10 0.005

70-30 solder 70 Sn, 30 Pb 0.50 0.015 0.005 0.03 0.25 0.001 0.08 0.02 30

nom 0.005

Eutectic solder

(63-37 solder)

63 Sn, 37 Pb 0.50 0.015 0.005 0.03 0.25 0.001 0.08 0.02 37

nom 0.005

60-40 solder 60 Sn, 40 Pb 0.50 0.015 0.005 0.03 0.25 0.001 0.08 0.02 40

nom 0.005

(a) Maximum unless a range or nominal (nom) is specified

(b) Ni + Co, 0.01% max

Impurities of a metallic and nonmetallic nature can be found in raw materials and in the scrap solder that is sometimes used by reclaimers Reclaimed solder is used in many industrial applications where impurities may not be detrimental However, correct selection of solder grade is important for economical production Manufacturing problems can result from inappropriate solder selection, from the use of solder baths for longer periods than contamination build-up will

tolerate, or from processing methods that rapidly contaminate a solder bath Determination of suitable specifications, of allowable impurities in new materials, and of allowable impurities in the solder bath through its deterioration to the point

at which it is discarded should be included in any soldering quality control program

Electrical and mechanical property data for selected tin-base solders are given in Table 6 The effects of elevated temperatures on the tensile strength and elongation of 60-40 solder are listed in Table 7

Table 6 Electrical and mechanical properties of selected tin-base solders

Antimonial-tin solder (95Sn-5Sb)

Tensile properties Cast: typical tensile strength, 40.7 MPa (5.9 ksi); elongation in 100 mm (4 in.), 38% Soldered copper joint: typical

tensile strength, 97.9 MPa (14.2 ksi)

Shear strength Cast, 41.4 MPa (6.0 ksi) Soldered copper joint, 76.5 MPa (11.1 ksi)

Impact strength Cast (Izod test), 27 J (20 ft · lbf)

Electrical conductivity Volumetric, 11.9% IACS at 20 °C (68 °F)

Electrical resistivity 145 nΩ · m at 25 °C (77 °F)

Tin-silver solder (95Sn-5Ag)

Tensile properties Sheet, 1.02 mm (0.040 in.) thick, aged 14 days at room temperature: typical tensile strength, 31.7 MPa (4.6 ksi); yield

strength, 24.8 MPa (3.6 ksi); elongation in 50 mm (2 in.), 49% Soldered copper joint: typical tensile strength, 96.5 MPa (14 ksi)

Shear strength Soldered copper joint, 73.1 MPa (10.6 ksi)

Electrical conductivity Volumetric, 16.6% IACS at 20 °C (68 °F)

Eutectic solder (63Sn-37Pb)

Tensile properties Cast: typical tensile strength, 51.7 MPa (7.5 ksi); elongation in 100 mm (4 in.), 32% Soldered copper joint: typical

tensile strength, 200 MPa (2g ksi)

Shear strength Cast, 42.7 MPa (6.2 ksi); soldered copper joint, 55.2 MPa (8 ksi)

Hardness Cast, 14 HB

Impact strength Cast (Izod test), 20 J (15 ft · lbf)

Creep characteristics Minimum creep rate: at room temperature and 2.3 MPa (335 psi), 0.1 mm/m (100 μin./in.) per day; at 80 °C (176

°F) and 467 MPa (68 psi), 0.1 mm/m (100 μin./in.) per day

Dynamic viscosity 1.33 mPa · s (0.0133 poise) at 280 °C (536 °F)

Liquid surface tension 0.490 N/m at 280 °C (536 °F)

Electrical conductivity Volumetric, 11.9% IACS

Electrical resistivity 145 nΩ · m

60-40 soft solder (60Sn-40Pb)

Tensile properties Bulk solder at room temperature (measurements depend greatly on conditions of casting and testing): mean tensile

strength, 52.5 MPa (7.61 ksi); elongation, 30-60%

Shear strength Mean, 37.1 MPa (5.38 ksi) (depends greatly on conditions of casting and testing)

Hardness 16 HV (depends on casting conditions)

Elastic modulus Tension (bulk solder), 30.0 GPa (4.35 × 106 psi)

Rupture life: 1000 h under stress of 4.5 MPa (650 psi) at 26 °C (79 °F); 1000 h under stress of 1.4 MPa (200 psi) at 80 °C (176 °F)

Dynamic liquid viscosity Estimated, 2.0 mPa · s (0.020 poise) at the liquidus temperature

Liquid surface tension Estimated: 468 mN/m at 330 °C (626 °F), 461 mN/m at 430 °C (806 °F)

Electrical conductivity Volumetric, 11.5% IACS

Electrical resistivity 149.9 nΩ · m

Thermoelectric potential Same as pure tin when measured against copper

Temperature of superconductivity 7.05 K Critical field, 83.2 mT at 1.3 K

Table 7 Effect of temperature on properties of 60-40 solder cast at 300 °C (570 °F) in steel molds (specimens not machined)

Temperature Tensile strength

Thermal Properties. Solidus and liquidus points of various solder compositions are given in Table 4 and in the article

"Lead and Lead Alloys" in this Volume Other thermal properties include:

Solder Linear thermal expansion

at 15-110 °C (60-230 °F), 10 -6 /K

Thermal conductivity at 0-180 °C (32-355 °F), W/m · K

Reference cited in this section

1 R.J Klein Wassink, Soldering in Electronics, 2nd ed., Electrochemical Publications, 1989

Pewter

Pewter is a tin-base white metal containing antimony and copper Originally, pewter was defined as an alloy of tin and lead, but to avoid toxicity and dullness of finish, lead is excluded from modern pewter These modern compositions contain 1 to 8% Sb and 0.25 to 3.0% Cu Pewter casting alloys usually are lower in copper than pewters used for spinning hollowware and thus have greater fluidity at casting temperatures

Modern pewter consists of a cored solid solution of antimony in tin within which are distributed fine crystals of (Cu6Sn5) phase Pewter is malleable and ductile, and it is easily spun or formed into intricate designs and shapes Pewter parts do not require annealing during fabrication Much of the costume jewelry produced today is made of pewter alloys centrifugally cast in rubber or silicone molds Typical pewter products include coffee and tea services, trays, steins, mugs, candy dishes, jewelry, bowls, plates, vases, candlesticks, compotes, decanters, and cordial cups

Chemical Composition. Although a wide range of compositions has been called pewter, the usual modern alloys contain 90 to 95% Sn and 1 to 3% Cu, with the balance consisting of antimony Some pewterlike materials are sand cast

or spun aluminum alloys, which are traditionally not considered to be pewter Although some pewter contains lead as an

alloying constituent, a considerable portion of lead is undesirable for applications in which the material may be in contact with food or beverages In addition, lead may impart a dullness to the ware

Composition limits of modern pewter are shown in Table 8

Table 8 Chemical composition limits for modern pewter

Composition, % Specification

Sn Sb Cu Pb max As max Fe max Zn max Cd max

3.1-7.0 1-2 0.5

(a) Casting alloy, nominal composition 92Sn-7.5Sb-0.5Cu

(b) Sheet alloy, nominal composition 91Sn-7Sb-2Cu

(c) Special-purpose alloy

Physical Properties. Typical tensile properties and hardnesses of pewter are given in Table 9 The effect of processing variables on the mechanical properties of pewter is covered in Table 10 In addition to those properties given in Table 9, pewter has:

Section thickness Tensile strength Form and condition

Elongation in

50 mm (2 in.), %

Hardness,

HB

Sheet, annealed 1 h at 205 °C (400 °F), air cooled 6.12 0.241 59 8.6 40 9.5

Sheet, cold rolled, 32% reduction 6.12 0.241 52 7.6 50 8.0

(a) Modulus of elasticity, 53 GPa (7.7 × 106 psi)

Table 10 Effect of processing variables on the mechanical properties of pewter sheet and on the amount of earing during drawing

Properties are mean values of three determinations each on 1 mm (0.04 in.) thick sheets of Sn-6Sb-2Cu alloy that were cold rolled from 25 mm (1.00 in.) thick cast stabs

Tensile strength at angle to rolling direction of

Elongation, % at angle to

rolling direction

of

between processing and testing

MPa ksi MPa ksi MPa ksi 0° 55° 90°

intermediate thickness

24 h 48 7.0 48 7.0 50 7.3 92 136 122 13

41

2

Unidirectional rolling, with

heat treatment(a) at

Fabrication Characteristics. Pewter has good solderability Casting temperatures of pewter range from 315 to 330 °C (600 to 625 °F)

Pewter can be formed by rolling, hammering, spinning, or drawing The earing of pewter sheet can be reduced by an intermediate cross-rolling operation or heat treatment; rolling can then be continued down to final thickness

Reference cited in this section

2 R Duckett and P.A Ainsworth, Sheet Met Ind., Vol 50 (No 7), 1973, p 412

Bearing Alloys

The primary consideration in the selection of a bearing alloy is that the material must have a low coefficient of friction Bearing alloys also must maintain a balance between softness and strength Aluminum-tin bearing alloys, for example, provide an excellent compromise between the requirement for high fatigue strength and the need for good surface properties such as softness, seizure resistance, and embeddability Tin-base bearing alloys are specified in ASTM B 23, AMS 4800, and U.S Government specification QQ-M-161

Compositions. Table 11 lists the chemical compositions of various tin-base bearing alloys specified in ASTM and SAE standards Tin has a low coefficient of friction and thus meets the primary requirement of a bearing material Tin is structurally a weak metal; therefore, when it is used in bearing applications it is alloyed with copper and antimony for increased hardness, tensile strength, and fatigue resistance Normally, the quantity of lead in these alloys, called tin-base babbitts, is limited to 0.35 to 0.5% to avoid formation of the tin-lead eutectic, which would significantly reduce strength properties at operating temperatures

Table 11 Compositions of tin-base bearing alloys

Nominal composition, % Designation

Bi max

Zn max

Al max

Total other max

(a) Desired minimum in ASTM alloys; specified minimum in SAE alloys

(b) Maximum unless a range is specified

(c) Total named elements, 99.80%

The presence of zinc in tin-base bearing metals generally is not favored Arsenic increases resistance to deformation at all temperatures; zinc has a similar effect at 38 °C (100 °F), but causes little or no change at room temperature Zinc has a marked effect on the microstructures of some of these alloys Small quantities of aluminum (even less than 1%) will modify their microstructures Bismuth is objectionable because, in combination with tin, it forms a eutectic that melts at

137 °C (279 °F) At temperatures above this eutectic, alloy strength is appreciably decreased

In high-tin alloys, such as ASTM grades 1, 2, and 3, and SAE 11 and 12, lead content is limited to 0.50% or less because

of the deleterious effect of higher percentages on the strength of these alloys at temperatures of 150 °C (300 °F) and above Lead and tin form a eutectic that melts at 183 °C (361 °F) At higher temperatures, bearings become fragile as a result of the formation of a liquid phase within them

Lead-base bearing alloys, called lead-base babbitts, contain up to 10% Sn and 12 to 18% Sb In general, these alloys

are inferior in strength to tin-base babbitts, and this must be equated with their lower cost Segregation of the constituents

of these alloys may provide some difficulties during centrifugal casting of linings During casting, careful selection of rotational speed in relation to bearing size is necessary Additions of cerium, arsenic, or nickel also assist in controlling segregation of these alloys Lead-base babbitt alloys are discussed in more detail in the article "Lead and Lead Alloys" in this Volume

Intermediate Lead-Tin Babbitt Alloys In addition to the tin-base and lead-base babbitts, there is a series of

intermediate lead-tin bearing alloys These alloys have tin and lead contents between 20 and 65%; in addition, they contain various amounts of antimony and copper Increasing the tin content of these alloys provides higher hardness and greater ease of casting These alloys are less prone to segregation during melting than lead-base babbitts Cast intermediate bearing alloys, however, exhibit lower strength values than either tin-base or lead-base babbitts

Aluminum-tin bearing alloys represent an excellent compromise between the requirement for high fatigue strength

and the need for good surface properties such as softness, seizure resistance, and embeddability Aluminum-tin bearing alloys are usually employed in conjunction with hardened-steel or ductile-iron crankshafts, and they allow significantly higher loading than tin- or lead-base bearing alloys

Low-tin aluminum-base alloys (5 to 7% Sn) containing small amounts of strengthening elements, such as copper

and nickel, are often used for connecting-rod and thrust bearings in high-duty engines Strict dimensional tolerances must

be adhered to, and oil contamination should be avoided Alloys containing 20 to 40% Sn and a balance of aluminum show excellent resistance to corrosion by products of oil breakdown; they also exhibit good embeddability, particularly in dusty environments The higher-tin alloys have adequate strength and better surface properties, which make them useful for crosshead bearings in high-power marine diesel engines

Properties of Tin-Base Bearing Alloys. The mechanical properties of selected tin-base bearing alloys are shown in Tables 12 and 13 The mechanical-property values obtained from massive cast specimens are dependent on temperature Also, hardness and compression tests are sensitive to the duration of the load because of the plastic nature of these materials Bulk properties may be of some value in initial screening of materials, but they do not accurately predict the behavior that the material will exhibit when it is in the form of a thin layer bonded to a strong backing, which is the manner in which the babbitts are normally used The relationship that exists between bearing life and the thickness of the babbitt is shown in Fig 3, which also shows the marked influence of operating temperature

Table 12 Physical properties and compressive strengths of selected tin-base bearing alloys

Compressive yield strength (a)(b)

Compressive ultimate strength (a)(c)

At 20 °C (68 °F)

At 100 °C (212 °F)

At 20 °C (68 °F)

At 100 °C (212 °F)

Hardness, HB (d) Solidus

temperature

Liquidus temperature

Pouring temperature

ASTM B 23, Alloy 1 7.34 30.3 4.40 18.3 2.65 88.6 12.85 47.9 6.95 17.0 8.0 223 433 371 700 440 825

ASTM B 23, Alloy 2 7.39 42.1 6.10 20.7 3.00 102.7 14.90 60.0 8.70 24.5 12.0 241 466 354 669 425 795

ASTM B 23, Alloy 3 7.46 45.5 6.60 21.7 3.15 121.3 17.60 68.3 9.90 27.0 14.5 240 464 422 792 490 915

Lead-tin babbitt from Table II 7.53 38.3 5.55 14.8 2.15 111.4 16.15 47.6 6.9 24(e) 12 184 363 306 583

ASTM B 102, Alloy PY1815A (die cast) 7.75 34 5 14 2.1 103 15 46 6.7 23 10 181 358 296 565

(a)

The compression test specimens were cylinders 38 mm (1 1

2 in.) long and 13 mm (

1

2 in.) in diameter, machined from chill castings 50 mm (2 in.) long and 20 mm (

3

4 in.) in diameter

(b) Values for yield point were taken from stress-strain curves at a deformation of 0.125% reduction of gage length

(c) Values for ultimate strength were taken as the unit load necessary to produce a deformation of 25% of the length of the specimen

(d)

Tests were made on the bottom face of parallel machined specimens cast at room temperature in a steel mold 50 mm (2 in.) in diameter by 16 mm (5

8in.) deep The Brinell hardness values listed are the

averages of three impressions on each alloy, using a 10 mm ball and applying a 500 kg load for 30 s

(e) Chill cast hardness of 27 HB

Table 13 Mechanical properties of selected tin-base babbitt alloys

See Table 12 for compressive strengths

Typical tensile strength

Elastic modulus

strength

Fatigue strength

GPa 10 6 psi J ft · lbf MPa ksi

Chill cast 64 9.3 2(a) 50 7.3 3.4(b) 2.5(b) 26(c) 3.8(c) Alloy 1

Die cast 62 9 2(a)

Chill cast 77(d) 11.2(d) 18(e) 33(c) 4.8(c) Alloy 2

Die cast 87(f) 12.6(f) 52(g) 7.6(g)

(a) Elongation in 50 mm (2 in.)

(b) Izod impact energy of 0.9 J (0.7 ft · lbf) at 200 °C (390 °F)

(c) Fatigue strength for 2 × 107 cycles, R.R Moore-type test

(d) Tensile strength of 45 MPa (6.5 ksi) at 100 °C (212 °F) and 20 MPa (2.9 ksi) at 175 °C (345 °F)

(e) Gage length equals 4 Area

(f) Cast from 315 °C (600 °F) into mold at 150 °C (300 °F)

(g) Cast from 400 °C (750 °F) into a mold at 100 °C (212 °F)

Fig 3 Variation of bearing life with temperature for SAE 12 bimetal bearings Thickness of alloy lining, 0.05 to

0.13 mm (0.002 to 0.005 in.); bearing load, 14 MPa (2000 psi)

Compared with other bearing materials, tin alloys have low resistance to fatigue, but their strength is sufficient to warrant their use under low-load conditions These alloys are easy to bond and handle, and they have excellent antiseizure qualities In addition, they are much more resistant to corrosion than lead-base bearing alloys

Microstructures. Tin-base bearing alloys vary in microstructure in accordance with their composition Alloys that contain about 0.5 to 8% Cu and less than about 8% Sb are characterized by a solid-solution matrix in which needles of a copper-rich constituent and fine, rounded particles of precipitated SbSn are distributed The proportion of the copper-rich constituent increases with copper content SAE 12 (ASTM Grade 2) has a structure of this type in which the needles often assume a characteristic hexagonal starlike pattern Alloys that contain about 0.5 to 8% Cu and more than about 8% Sb exhibit primary cuboids of SbSn and needles of the copper-rich constituent in the solid-solution matrix In alloys with about 8% Sb and about 0.5 to 8% Cu, rapid cooling suppresses formation of the SbSn cuboids; this is particularly true of alloys containing lower percentages of copper

Other Tin-Base Alloys

Alloys for Organ Pipes. Tin-lead alloys are used in the manufacture of organ pipes These materials are commonly called spotted metal because they develop large nucleated crystals, or spots, when solidified as strip on casting tables The

pipes that produce the diapason tones of organs generally are made of alloys with tin contents varying from 20 to 90% according to the tone required Broad tones generally are produced by alloys rich in lead; as tin content increases, the tone becomes brighter Cold-rolled tin-copper-antimony alloys (95% Sn) also have been used successfully in the manufacture

of pipes, and the adoption of these alloys has improved the efficiency and speed of fabrication of finished pipes This composition provides for a bright appearance that is more tarnish resistant than the tin-lead alloys

Type metals are cast alloys containing various proportions of lead, antimony, and tin They do not readily segregate on solidification from the melt, buy they are subject to porosity in the central regions of type characters and slugs because air

in molds escapes with difficulty When these alloys are used, good fill of the mold should be ensured by rapid injection, and the temperature of the metal should be high enough to avoid premature solidification and entrapment of gases Further information on type metals is given in the article "Lead and Lead Alloys" in this Volume

Tin-base casting alloys are included in ASTM specification B 102, Alloy CY44A in this specification is similar to Alloy 1 in ASTM B 23 for sleeve bearings (Tables 11 and 12) Composition limits of the die casting version (Alloy CY44A in ASTM B 102) are 90 to 92% Sn, 4 to 5% Sb, 4 to 5% Cu, 0.35% Pb max, 0.08% Fe max, 0.08% As max, 0.01% Zn max, and 0.01% Al max

Alloy PY1815A in ASTM B 102 is another alloy used for die castings and sleeve bearings This alloy which has nominal contents of 82% Sn, 13% Sb, and 5% Cu, is included in Tables 11 and 12 with the other tin-base bearing alloys

Alloy YC135A in ASTM B 102 has nominal composition contents of 65% Sn, 18% Pb, 15% Sb, and 2% Cu and is typically used for die castings This alloy has a typical tensile strength of 69 MPa (10 ksi), an elongation value of 1% in

50 mm (2 in.), and a hardness of 29 HB Alloy YC135A has creep-rupture strengths of about 17 MPa (2.5 ksi) for 1 year and 13 MPa (1.875 ksi) for a 10-year life

White metal (92Sn-8Sb) is a tin-base alloy used for jewelry Typical mechanical properties of white metal are listed

in Tables 14 and 15 During cold rolling, the alloy hardens at first, and maximum hardness is reached at a reduction of about 40 to 45% Further working causes progressive softening until, at about 80% reduction, the hardness approaches that of the cast alloy; annealing at 200 to 225 °C (392 to 437 °F) causes the severely worked alloy to harden slightly

Table 14 Mechanical properties of white metal

Section size Tensile strength Form and condition

Elongation,

%

Chill cast, tested 2 months after casting(a) 50 × 13

2 × 12

50 7.2

Chill cast, annealed at 225 °C (437 °F)(b) 50 × 13

2 × 12

Wire, extruded 3.5 0.14 59 8.5 63

Wire, extruded and annealed 24 h at 225 °C (437 °F) 3.5 0.14 54 7.8 10

(a) Brinell hardness, 20

(b) Brinell hardness, 17

(c) Izod impact value, 30 J (22 ft · lbf); shear strength, 46 MPa (6.7 ksi)

(d) In 50 mm (2 in.)

Table 15 Creep-rupture characteristics of white metal

Tests conducted at room temperature (9 to 27 °C, or 48 to 81 °F) on rolled material 2.5 mm (0.1 in.) thick

(a) Specimen did not fracture

The solidus temperature of white metal is 246 °C (475 °F) White metal has a volumetric electrical conductivity of about 11.1% IACS and an electrical resistivity of about 155 nΩ · m at 25 °C (77 °F)

Fusible alloys are any of the more than 100 white metal alloys that melt at relatively low temperatures Most commercial fusible alloys contain bismuth, lead, tin, cadmium, indium, and antimony, and special alloys of this class may

also contain significant amounts of zinc, silver, thallium, or gallium Further information on fusible alloys is contained in the article "Indium and Bismuth" in this Volume

Many of the fusible alloys used in industrial applications are based on eutectic compositions These alloys find important uses in automatic safety devices such as fire sprinklers, boiler plugs, and furnace controls Under ambient temperature, these alloys have sufficient strength to hold parts together, but at a specific elevated temperature the fusible-alloy link will melt, thus disconnecting the parts Examples of tin-base eutectic fusible alloys are:

Melting temperature Alloy composition, %

Hard tin (99.6Sn-0.4Cu) is used for collapsible tubes and foils Hard tin is resistant to attack by foodstuffs, medicinal products, cosmetics, and artist's colors The luquidus temperature of hard tin is 230 °C (446 °F); the solidus temperature is

227 °C (441 °F)

Typical tensile strengths of 2.5 mm (0.1 in.) thick strip hard tin in various conditions are:

• 23 MPa (3.3 ksi) for strip annealed for 3 h at 100 °C (212 °F)

• 21 MPa (3.1 ksi) for strip annealed for 3 h at 200 °C (390 °F)

• 28 MPa (4.0 ksi) for cold-rolled strip (80% reduction)

Bursting of a tube 25 mm (1 in.) in diameter and 0.1 mm (0.004 in.) in wall thickness occurred with an internal pressure

of 320 kPa (46 psi) In a bend test, a flattened impact-extruded collapsible tube 0.1 mm (0.004 in.) in wall thickness survived 21 bends over 90° jaws (1 kg load)

Tin foil (92Sn-8Zn) is used for food packaging Its suitability for this application is indicated by, for example, immersion and bottle-capping tests with milk that showed that this alloy is only slightly soluble and has no effect on the milk (Ref 3)

Typical tensile properties of tin foil include a tensile strength of 60 MPa (8.7 ksi), a yield strength of 41 MPa (6.0 ksi), and an elongation of 40% The solidus temperature is about 200 °C (390 °F)

Reference cited in this section

3 R Kerr, The Behavior of Some Metal Foils in Contact with Milk, J Soc Chem Ind., Vol 61, 1942, p 128

Other Alloys Containing Tin

Battery Grid Alloys. Lead-calcium-tin alloys have been developed for storage-battery grids, largely as replacements for antimonial-lead alloys The use of ternary lead-base alloys containing up to 1.3% Sn has substantially reduced gassing, and thus batteries with grids made of these alloys do not require periodic water additions during their working life Two chief methods of grid manufacture are casting and fabrication of wrought alloys; fabrication of wrought alloys includes punching, roll forging, and expanded-metal processes

Copper Alloys. Copper-tin bronzes were some of the first alloys used by man, and these alloys continue to be used for structural and decorative purposes True bronzes contain tin in amounts up to 10% as well as very small amounts of phosphorus Quaternary bronzes containing 5% Sn, 5% Zn, 5% Pb, and a balance of copper are used for general-purpose castings for applications requiring reasonable strength and soundness, such as gears, pumps, and automotive fittings Special copper-base alloys with 20 to 24% Sn have historically been used for cast bells of excellent tonal quality Spinodal copper-nickel-tin alloys containing 2 to 8.5% Sn have excellent elastic properties and have replaced tin-free copper-nickel alloys in some spring and electrical-contact applications In addition to these uses in copper-base alloys, small quantities of tin (0.75 to 1.0%) are added to copper-zinc alloys (brasses) for increased corrosion resistance Cast leaded brasses may contain up to 4% Sn

Dental alloys for making amalgams contain silver, tin, mercury, and some copper and zinc The copper increases hardness and strength, and the zinc acts as a scavenger during alloy manufacture, protecting major constituents from oxidation Most of the dental alloys presently available contain 25 to 27% Sn and consist mainly of the intermetallic compound Ag3Sn When porcelain veneers are added to gold alloys for high-grade dental restoration, 1% Sn is added to the gold alloy to ensure bonding with the porcelain

Cast Irons. The presence of about 0.1% Sn in flake or ductile iron castings ensures a completely pearlitic structure, and this pearlite is retained even at elevated temperatures Commercially pure tin is added to the cast iron in the form of shot, bars, or cast pieces; in cupola melting, the tin is commonly added to the ladle or to the cupola spout during tapping Tin is also added to special mixing chambers along with suitable inoculant materials in the production of ductile iron castings Because the mixing chambers are an integral part of the mold, this technique allows one-step treatment of the molten metal as it enters the mold, and it prevents fading (that is, the loss of effectiveness of inoculating additions before the metal is cast) In addition, the mixing chamber provides immediate dissolution of the tin in the iron and ensures uniform distribution in the casting

Titanium Alloys. Tin strengthens titanium alloys by forming solid solutions Titanium can exist in the low-temperature α-phase or the higher temperature β phase, which remains stable up to the melting point In titanium alloys, relative amounts of α-and β phases present at the service temperature have profound effects on properties Aluminum additions raise the transformation temperature and stabilize the α-phase, but they can cause embrittlement in amounts greater than 7% However, with tin additions, increased strength without embrittlement can be obtained in aluminum-stabilized α-titanium alloys Optimum strength and workability can be obtained with 5% Al and 2.5% Sn; in addition, this alloy has the advantage of being weldable Alpha-beta titanium alloys contain aluminum as an α-stabilizer and combinations of β stabilizers (such as chromium, iron, molybdenum, manganese, or vanadium), as well as tin and zirconium as substitutional solid-solution strengthening elements Such alloys have good strength and creep resistance at elevated temperatures Strength and forming properties of many of these alloys can be optimized by various heat treatments

Zirconium alloys are similar to titanium alloys in that the elements they contain can be divided into two classes: stabilizers, which raise the transformation temperature, and β-stabilizers, which lower it Tin and aluminum are α-stabilizers in zirconium alloys and enhance high-temperature strength A commercial series of corrosion-resistant zirconium alloys containing 0.15 to 2.5% Sn has been developed for nuclear service

α-Zinc and α-Zinc Alloys

Robert J Barnhurst, Noranda Technology Centre

Introduction

ZINC AND ZINC ALLOYS for decorative and functional applications are described in this article Zinc and zinc alloys are used in the form of coatings, castings, rolled sheets, drawn wire, forgings, and extrusions Other uses of zinc are as a major constituent in brasses (see the articles on copper-base alloys in this Volume) and as a sacrificial anode for marine environments

In its purer form, zinc is available as slabs, ingots, shot, powder, and dust; combined with oxygen, it is available as zinc oxide powder Slab zinc is produced in three grades (Table 1) Impurity limits are very important when zinc is used for alloying purposes Exceeding impurity limits can result in poor mechanical and corrosion properties Pure zinc shot is used primarily for additions to electrogalvanizing baths, and zinc powder and dust are used in batteries and in enhanced corrosion-resistant paints Zinc oxide is used as a pigment in primers and finish paint, as a reducing agent in chemical processes, and as a common additive in the production of rubber products

Table 1 Grades and compositions of slab zinc (ASTM B 6)

Al max

Cu max

Sn max

Total nonzinc max

Zn min by difference

Special high grade Z13001 0.003 max 0.003 0.003 0.002 0.002 0.001 0.010 99.990

High grade Z15001 0.03 max 0.02 0.02 0.01 0.10 99.90

Zinc Products

Coating of steel constitutes the largest single use of zinc, but it is used in large tonnages in zinc alloy castings, as zinc dust and oxide (for zinc-rick organic and inorganic coatings), and in wrought zinc products This section will review the

various zinc product forms as well as provide references to articles in other ASM Handbook volumes that contain more

detailed information The mechanical and physical properties of both wrought and cast alloys are described in the section

"Properties of Zinc Alloys" in this article

Zinc Coatings

The use of zinc as a coating to protect steel and iron from corrosion is the largest single application for the metal worldwide Metallic zinc coatings are applied to steels:

• From a molten metal bath (hot dip galvanizing)

• By electrochemical means (electrogalvanizing)

• From a spray of molten metal (metallizing)

• In the form of zinc powder by chemical/mechanical means (mechanical galvanizing)

Zinc coatings are applied to many different types of products, ranging in size from small fasteners to continuous strip to large structural shapes and assemblies

Hot Dip Galvanizing. The hot dip galvanizing industry is currently the largest consumer of zinc in the coatings field It

is divided into two segments:

• Production of continuously galvanized steel strip

• Galvanizing of structural shapes and products after fabrication

Galvanized products can be joined by conventional techniques such as welding and bolting

Conventional strip galvanizing makes use of an alloy with a nominal content of 0.20% Al and a balance of zinc

The coating thickness is generally less than 25 μm (0.001 in.), or approximately 175 g/m2 (0.573 oz/ft2) of steel surface (one-side total) The coating is characterized by excellent adhesion and formability These attributes, along with good weldability by conventional welding techniques, make strip galvanizing particularly attractive for automobile manufacturing Galvanized strip is also used in the building industry, where significant tonnages are used in prepainted condition The appliance industry is also a large consumer of both painted and unpainted galvanized strip Some galvanized strip is subjected to a heat treatment known as galvannealing that converts the coating to an iron-zinc alloy Galvannealing has been used for building products for a number of years and, more recently, for automotive parts In recent years, new strip coatings with improved corrosion resistance, namely Galfan (5% Al) and Galvalume (55% Al), have been introduced Galfan has been incorporated into ASTM B 750 (Table 2) and Galvalume into ASTM A 792

Additional information on strip galvanizing is available in the article "Precoated Steel Sheet" in Properties and Selection: Irons, Steels, and High-Performance Alloys, Volume 1 of ASM Handbook, formerly 10th Edition Metals Handbook and

in the articles "Hot Dip Coatings," "Organic Coatings and Linings," and "Corrosion of Zinc" in Corrosion, Volume 13 of ASM Handbook, formerly 9th Edition Metals Handbook

Table 2 Zn-5Al-MM alloy ingot chemical requirements for hot dip coatings (Galfan, or UNS Z38510) per ASTM B 750

Other max each(c) 0.02

Other max total(c) 0.04

Zinc bal

Note: For purposes of acceptance and rejection, the observed value or calculated value obtained from analysis should be rounded to the nearest unit in the last right-hand place of figures used in expressing the specified limit, in accordance with the rounding procedure prescribed in Section 3 of ASTM E 29 By agreement between purchaser and supplier, analysis may be required and limits established for elements or compounds not specified in the table of chemical composition Zn-5Al-MM alloy ingot for hot dip coatings may contain antimony, copper, and magnesium in amounts of up to 0.002, 0.1, and 0.05%, respectively No harmful effects have ever been noted from the presence of these elements up to these concentrations; therefore, analyses are not required for these elements Magnesium may be specified by the buyer up to 0.1% max Zirconium and titanium may each be specified by the buyer up

to 0.02% max

(a) Aluminum may be specified by the buyer up to 7.2% max

(b) Lead and cadmium and to a lesser extent, tin and antimony are known to cause intergranular corrosion in zinc-aluminum alloys Therefore, it is important to maintain the levels of these elements below the limits specified

(c) Except antimony, copper, magnesium, zirconium, and titanium

After-Fabrication Galvanizing An aluminum-free grade of zinc that contains up to 1 wt% Pb and a balance of zinc

is used for after-fabrication galvanizing Most specifications cell for a minimum coating thickness in the range of 85 to

100 μm (0.0034 to 0.004 in.), or 500 to 600 g/m2 (1.6 to 2.0 oz/ft2) Coating thickness is controlled by immersion time, which in turn is governed by the substrate thickness; it can be much higher with some reactive grades of steel containing even small amounts of silicon (silicon-killed steels) Proprietary galvanizing processes that use small additions of aluminum (Polygalva) or nickel (Technigalva) in concentrations of 0.04 and 0.08 wt%, respectively, have been developed

in attempts to control coating thickness

Traditional markets for after-fabrication coatings include electric utility and microwave transmission towers; related products such as guard rails, signs, and lighting standards; structural applications in the industrial sector (for example, chemical, petrochemical, agricultural, and pulp and paper industries); drainage products; pipe for potable drinking water; heat exchangers; and reinforcing bar for concrete structures

highway-Electrogalvanizing. Strip-applied electrogalvanized coatings are becoming increasingly important for automotive applications These coatings are applied at high-speed, high-current-density electroplating lines Pure zinc as well as zinc-nickel and zinc-iron coatings are produced The coatings are generally more uniform, smoother, and thinner than hot dip coatings Corrosion resistance, coating-to-steel adhesion, formability, weldability, and paintability are critical properties for automotive applications of electrogalvanized steel

Metallizing, also known as thermal spraying, is used in applications where heavy coatings are specified for corrosion protection The process is amenable to field applications and is used in refurbishing existing structures Very long service lives are possible with composite systems, often with the use of thinner coatings (plus suitable organic paint coats) than those that are required with conventional metallizing alloys

In a typical metallizing procedure, either pure zinc (special high grade) or Zn-15Al is sprayed onto the steel surface to be protected The zinc alloy is provided either in dust form or as rods that are atomized by a flame or electric arc and then propelled onto the substrate by a high-speed gas jet Additional information is available in the article "Thermal Spray

Coatings" in Surface Engineering, Volume 5 of ASM Handbook

Mechanical galvanizing is a batch process that is carried out in rotating drums During processing, the workpiece is tumbled in a mixture of zinc dust, chemicals, and glass beads, and the coating is impacted onto the surface of the workpiece by the tumbling action It is used for coating fasteners fabricated from specialty spring or case-hardened steels,

or both materials, because the properties of such fasteners might be adversely affected by the high temperature of a hot dip bath Mechanical galvanizing is also used for applications where relatively heavy coating weights are specified

Zinc Alloy Castings

Zinc alloys are used extensively in both gravity and pressure die castings When used as general casting alloys, zinc alloys can be cast using such processes as high-pressure die casting, low-pressure die casting, sand casting, permanent mold casting (iron, graphite, or plaster molds), spin casting (silicone rubber molds), investment (lost-wax) casting, continuous

or semicontinuous casting, and centrifugal casting A newer process involves semisolid casting, of which several techniques can be employed A detailed treatment of casting processes for zinc alloys is included in the article "Zinc and

Zinc Alloys" in Casting, Volume 15 of ASM Handbook, formerly 9th Edition Metals Handbook Corrosion is of no

concern for most applications However, for castings under moderate-to-severe corrosive attack, some loss of properties is

to be expected Long-term aging also may cause some small loss of properties; the effects will vary from alloy to alloy and depend upon the casting method used

Pressure Die Castings. Zinc alloys have been used for die casting for over 60 years Until recently, all zinc alloys were based on a hypoeutectic composition, that is, they contained less aluminum (close to 4.0% Al) than the eutectic chemistry of 5.0% Al Recently, a family of hypereutectic zinc-aluminum alloys with higher aluminum contents (>5.0% Al), have become widely used as die casting alloys These alloys were originally designed as gravity casting alloys (see the section "Gravity Castings" in this article) They possess higher strength than the hypoeutectic zinc alloys The compositions of current die casting alloys are included in Tables 3 and 4

Table 3 Nominal compositions of common zinc alloy die castings and zinc alloy ingot for die casting

max

Pb max

Cd max

Sn max

3.5- 0.05(e)

0.020-0.100 0.005 0.004 0.003 bal

Z33523(b) AG40B No 7 0.25 max

3.5-4.3

0.020

3.5-0.03-0.08(e) 0.100 0.005 0.004 0.003 bal

Z35541 AC43A No 2 2.5-3.0

3.5-4.3

0.050

0.020-0.100 0.005 0.004 0.003 bal

Ingot form (ASTM B 240)

Z33521(c) AG40A No 3 0.10 max

4.3

Note: For purposes of acceptance and rejection, the observed value or calculated value obtained from analysis should be rounded to the nearest unit in the last right-hand place of figures used in expressing the specified limit, in accordance with the rounding procedure prescribed in ASTM E 29

(a) ASTM alloy designations were established in accordance with ASTM B 275 UNS designations were established in accordance with ASTM E

527 The last digit of a UNS number differentiates between alloys of similar composition UNS designations for ingot and casting versions of

an alloy were not assigned in the same sequence for all alloys

(b) Zinc alloy die castings may contain nickel, chromium, silicon, and manganese in amounts of 0.02, 0.02, 0.035, and 0.06%, respectively No harmful effects have ever been noted from the presence of these elements in these concentrations; therefore, analyses are not required for these elements

(c) Zinc alloy ingot for die casting may contain nickel, chromium, silicon, and manganese in amounts of up to 0.02, 0.02, 0.035 and 0.05%, respectively No harmful effects have ever been noted from the presence of these elements up to these concentrations; therefore, analyses are not required for these elements, except that nickel analysis is required for Z33522

(d) For the majority of commercial applications, a copper content in the range of 0.25-0.75% will not adversely affect the serviceability of die castings and should not serve as a basis for rejection

(e) Magnesium may be as low as 0.015% provided that the lead, cadmium, and tin do not exceed 0.003, 0.003, and 0.002% respectively

Table 4 Nominal compositions of zinc-aluminum foundry and die casting alloys directly poured to produce castings and in ingot form for remelting to produce castings

Al Cu Mg Zn (b) Fe max Pb max Cd max Sn max

ZA-27 Z35840 25.5-28.0 2.0-2.5 0.012-0.020 bal 0.072 0.005 0.005 0.002

(a) UNS alloy designations have been established in accordance with ASTM E 527

(b) Determined arithmetically by difference

(c) Zinc-aluminum ingot for foundry and pressure die casting may contain chromium, manganese, or nickel in amounts of up to 0.01% each or 0.03% total No harmful effects have ever been noted from the presence of these elements in these concentrations; therefore, analyses are not required for these elements

Zinc casting alloys have dendritic/eutectic microstructures The hypoeutectic alloys solidify with zinc-rich (η) dendrites, whereas the hypereutectic alloys solidify with aluminum-rich dendrites The ZA-8 and ZA-12 alloys solidify with cored β dendrites, whereas ZA-27 solidifies with α-dendrites The microstructure of zinc alloys are discussed in detail in the

article "Zinc and Zinc Alloys" in Metallography and Microstructures, Volume 9 of ASM Handbook, formerly 9th Edition Metals Handbook

It is critically important that all zinc-aluminum casting alloys be carefully handled to prevent excessive pickup of harmful impurity elements such as lead, cadmium, tin, and iron, among others Cross contamination caused by melting the alloys

in furnaces used for casting copper and aluminum alloys or iron is particularly troublesome because these alloys contain elements harmful to zinc alloys Purity concerns have led producers in many countries (those belonging to the European Economic Community, for example) to require that only 100% virgin material be used in the production of zinc foundry alloys This requirement does not apply in North America, but alloyed ingots obtained from external suppliers are expected to meet strict impurity limits A maximum 50% remelt of foundry returns to the melting furnace is acceptable during the making of castings

Zinc alloys have low melting points, require relatively low heat input, do not require fluxing or protective atmospheres, and are nonpolluting; the last is a particularly important advantage The rapid chilling rate inherent in zinc die castings results in minor property and dimensional changes with time, particularly if the casting is quenched from the die rather than air cooled Although this is rarely a problem, a stabilizing heat treatment can be applied prior to service if rigid dimensional tolerances are to be met The higher the heat treatment temperature, the shorter the stabilizing time required;

100 °C (212 °F) is a practical limit to prevent blistering of the casting or other problems A common treatment consists of

3 to 6 h at 100 °C (212 °F), followed by air cooling The time extends to 10 to 20 h for a treatment temperature of 70 °C (158 °F)

Because of their high fluidity, zinc alloys can be cast in much thinner walls than other die castings alloys, and they can be die cast to tighter dimensional tolerances Zinc alloys allow the use of very low draft angles; in some cases, a zero draft angle is possible

Alloy No 2 has the highest tensile strength, creep strength, and hardness of all alloys in the hypoeutectic Zamak series

of die casting alloys The high copper content (3.0% Cu) causes some dimensional instability and leads to a net expansion

of approximately 0.0014% after 20 years It also causes some loss of impact strength and ductility Alloy No 2 has good bearing properties

Alloy No 3 is the most widely used zinc die casting alloy in the United States It provides the best overall combination

of strength, castability, dimensional stability, ease of finishing, and cost

Alloy No 5 produces castings that are both harder and stronger than those made from alloy No 3 However, these

properties improvements come at the expense of ductility, and postforming operations such as riveting, swaging, or crimping must be done with additional care The creep resistance of alloy No 5 is second only to that of alloy No 2 among the hypoeutectic zinc-aluminum alloys

Alloy No 7 is essentially a high-purity version of alloy No 3 Because of its lower magnesium content, alloy No 7 has

even better castability than alloy No 3, enabling excellent reproduction of surface detail in castings Alloy No 7 has the highest ductility among the hypoeutectic alloys

Alloy ZA-8 is the only member of the hypereutectic alloys that can be hot chamber die cast along with the hypoeutectic

alloys It is equivalent to alloy No 2 in many respects, but ZA-8 has higher tensile, fatigue, and creep strengths, is more dimensionally stable, and has lower density Alloy ZA-8 castings can be readily finished, thereby combining their high structural strength with excellent appearance

Alloy ZA-12 has very good castability in cold chamber die casting machines It is lower in density than all other zinc

alloys except ZA-27, and it is frequently specified for castings that must combine casting quality with optimum performance The plating quality of ZA-12 is lower than that of ZA-8, but it has excellent bearing and wear properties

Alloy ZA-27 is the lightest, hardest, and strongest of all the zinc alloys, but it has relatively low ductility and impact

strength when pressure die cast Because of the wide freezing range of ZA-27, casting quality can suffer unless care is taken The secondary creep strength of ZA-27 is better than that of all other zinc alloys except for the now rarely used ILZRO (International Lead-Zinc Research Organization) 16; however, ZA-8 has better primary creep strength Alloy ZA-

27 demonstrate the highest sound and vibration damping properties of all the zinc casting alloys; as a group, zinc alloys have a damping resistance equal to that of cast irons at elevated temperatures

Alloy ILZRO 16 was developed specifically for optimum creep resistance, particularly at elevated temperatures It does

have the highest creep resistance of all zinc alloys, but it is difficult to manufacture and suffers from melt instability; for these reasons, ZA-8 often is used in its place

It should be noted that the strength performance of zinc alloys drops significantly with increases in temperature At 100

°C (212 °F), tensile and yield strengths are typically 65 to 75% of those at room temperature, and creep strength is similarly reduced

Gravity Castings. With the exceptions of forming die alloys, slush casting alloys, and specialty alloys developed and used for bearings, no general-purpose gravity casting zinc alloys existed until the 1960s In the 1960s and 1970s, a new family of hypereutectic zinc-aluminum alloys was developed Alloy ILZRO-12 (now ZA-12) was the first to appear, beginning in 1962; ZA-8 and ZA-27 were quickly added Alloy ZA-12 was developed first as a prototyping alloy for alloy No 3 pressure die castings Alloy ZA-27 was developed specifically as a sand casting alloy, and ZA-8 was turned into a permanent mold casting alloy All three alloys are now used more extensively in pressure die castings

The performance of the ZA alloys when they are gravity cast varies markedly from that of the same alloys when they are pressure die cast The compositions of the gravity casting alloys are given in Table 4 The same requirements concerning impurities, melt cross contamination, and general handling described for the die casting alloys apply equally to the gravity casting alloys As with the die casting alloys, microstructural changes with time can alter the properties and dimensions of cast parts However, property changes are normally very small over the normal life span of a component, and dimensional changes, except in ZA-27, are negligible A stabilizing heat treatment of 12 h at 250 °C (482 °F), followed by furnace cooling, effectively eliminates three-fourths of the dimensional changes that occur upon long-term aging

Alloy ZA-8 is used mostly with ferrous permanent molds casting, but it is also used with graphite molds Alloy ZA-8 can

also be sand cast if needed, although sand casting is not used extensively for this alloy With the exception of creep resistance, the strength of a permanent mold casting is lower than that of a pressure die casting due to the coarser microstructure of the former The plating quality of ZA-8 is excellent, and its surface detail reproducibility is better than that of all other ZA alloys

Alloy ZA-12 is more versatile than ZA-8 because it can be either sand cast or permanent mold cast Its strength

properties are high, and its ductility and impact strength properties are acceptable It is clearly the alloy of choice for graphite mold casting The bearing and damping properties of ZA-12 are both very high Alloy ZA-12 can be readily semicontinuous cast in solid and hollow rounds for machining bushings and industrial bearings

Alloy ZA-27 develops its optimum properties when it is sand cast However, care should be taken when producing

heavy-section castings to ensure maximum soundness and minimal underside shrinkage Underside shrinkage, caused by gravity segregation of the aluminum-rich phase during solidification, causes a roughening on the drag surface of the casting as zinc liquid is drawn up into the casting Both a reduction in underside shrinkage and a sound casting can be

ensured when chills are used to promote directional solidification and to increase the solidification rate The addition of rare earth elements has also been reported to reduce underside shrinkage

In a sound gravity casting, ZA-27 produces ductility and impact strength properties much higher than those found in many die castings Alloy ZA-27 has excellent bearing and wear properties, and it demonstrates the best damping resistance of any zinc alloy Although it is very rarely required, a simple heat treatment of 3 h at 320 °C (608 °F), followed by furnace cooling, can increase the ductility and impact strength of ZA-27 castings Dimensional stability is enhanced by a stabilizing heat treatment of 12 h at 250 °C (482 °F), followed by furnace cooling

Kirksite alloy is used as a forming die alloy, and is capable of being sand cast to shape rapidly It has an almost

identical composition to the No 2 die casting alloy It is mainly used in the construction of cast two-piece dies for forming sheet metal parts such as components for use in the transportation and aerospace industries Kayem 1 and Kayem

2 are similar alloys used extensively in Europe Cast-to-size molds made of Kirksite are being used for plastic injection molding for both short-run prototyping and production operations Two die forming die alloys are included in ASTM B

Alloy B Z30500 5.25-5.75 0.005 0.1 max 0.100 0.007 0.005 bal

Slush casting alloys are used extensively for the production of hollow castings such as table lamp bases The molten

alloy is poured into the mold until it is full or nearly full, and then the mold is inverted, allowing the unsolidified metal (slush) to run out The solidified shell that is left is then removed The thickness of the shell depends on the time interval between pouring and inverting the mold, the melt and mold temperatures, and the mold material Two slush casting alloys are currently available (Table 5)

Specialty Alloys Main Metal alloy and Alzen alloy are still used in Europe for the production of continuously cast

bearing stock They are also used for sliding elements, hydraulic components, worm wheels, roller bearing cages, and several other products A series of Cosmal alloys, specifically formulated for applications requiring high damping, have been developed in Japan

Cast Product Applications. Zinc is used extensively in the transportation industry for parts such as carburetors, fuel pump bodies, wiper parts, speedometer frames, grilles, horns, shift levers, load-bearing transmission cases, heater components, brake parts, radio bodies, electronic heat sinks, lamp and instrument bezels, steering wheel hubs, alternator brackets, exterior and interior hardware, instrument panels, and body moldings Zinc castings are also extensively used in general hardware and electronic and electrical fittings of all kinds, including parts for domestic appliances (for example,

washing machines, vacuum cleaners, mixers, and so on), oil burners, motor housings, locks, and clocks Zinc castings are frequently and increasingly being specified for hardware used in the computer industry, in business machines (photocopiers, facsimile machines, cash registers, and typewriters), and in such items as recording machines, projectors, vending machines, cameras, gasoline pumps, many hand tools, and machinery such as larger drill presses and lathes The

ZA alloys are increasingly being specified for bearings and bushings in low-speed high-load applications

Finishing and Secondary Operations for Zinc Alloy Castings. Many of the finishes applied to other types of metal products can be applied to zinc die castings and gravity castings Suitable finishing treatments include:

• Mechanical buffing, polishing, brushing, and tumbling

• Plating with materials such as copper, nickel, silver and black nickel, chromium, electroless nickel, and brass

• Chemical finishing such as chromating, enameling, lacquering, painting, varnishing, anodizing, and vacuum aluminizing

• Plastic (powder coat) finishing

Phosphating of the cast surface is generally recommended to provide good adhesion for subsequent paint or powder coatings Additional information on surface preparation techniques and coatings for zinc is available in the article

"Surface Engineering of Zinc Alloys" in Surface Engineering, Volume 5 of ASM Handbook

Although zinc alloys have good natural corrosion resistance (provided that impurity limits are not exceeded), chromating and anodizing provide added corrosion protection in moderate-to-severe corrosive environments The white rust that can form on zinc castings stored in damp environments is effectively prevented or delayed by chromating the surface

Detailed information is available in the article "Corrosion of Zinc" in Corrosion, Volume 13 of ASM Handbook, formerly 9th Edition Metals Handbook

All zinc casting alloys have excellent machining properties, with long tool life, low cutting forces, good surface finish, low tool wear, and small chip formation Common machining operations performed on these alloys include drilling, tapping, reaming, broaching, routing, turning, milling, die threading, and sawing Detailed information is available in the

article "Machining of Zinc Alloy Die Castings" in Machining, Volume 16 of ASM Handbook, formerly 9th Edition Metals Handbook

Zinc alloy castings can be conveniently joined by soldering or brazing, or by certain welding techniques using zinc-base fillers Cadmium-, tin-, or lead-base solders are not recommended because they can promote intergranular corrosion problems unless the castings are plated with heavy coatings of nickel or copper prior to soldering Newer zinc-base

solders are becoming available Detailed information about these joining techniques is available in Welding, Brazing, and Soldering, Volume 6 of the ASM Handbook

Adhesive bonding or mechanical fasteners are also excellent methods for joining castings Zinc castings can be riveted, staked, and crimped Threaded fasteners, including self-tapping screws, should not be overtightened but rather tightened

to recommended torques Up to 40% loss of torque should be incorporated into the design for parts operating at elevated temperatures of 50 °C (122 °F) or higher Significant torque loss can be avoided by using special fasteners, including cone (spring or Belleville) or star washers of the correct size Joining two or more parts can be accomplished by die casting a joint to properly align and join the parts

Additional Properties of Zinc Castings. In addition to their excellent physical and mechanical properties, zinc alloys offer:

• Good corrosion resistance

• Excellent vibration- and sound-damping properties that increase exponentially with temperature (because of these damping characteristics, zinc alloys can be designated HIDAMETS, or high-damping metals

• Excellent bearing and wear properties

• Spark (incendivity) resistance (with the exception of the high-aluminum ZA-27 alloy)

Wrought Zinc and Zinc Alloys

Zinc in pure form or with small alloying additions is used in three main types of wrought products: flat-rolled products, wire-drawn products, and extruded and forged products Wrought zinc is readily machined, joined, and finished

Flat-Rolled Products. Zinc is usually cast into 25 to 100 mm (1.0 to 4.0 in.) thick flat slabs that are suitable for rolling; these slabs are preheated and then rough and finish rolled Schedules for finish rolling of zinc strip vary and depend on the product required Strip is produced in various widths up to 2 m (79 in.) and in thicknesses down to 0.1 mm (0.004 in.) Foil in thicknesses of 0.025 mm (0.001 in.) or less is produced in special mills For a bright surface combined with high ductility, finish rolling is performed at 120 to 150 °C (250 to 300 °F)

Rolled zinc can be readily formed into many different shapes by bending, spinning, deep drawing, roll forming, coining, and impact extrusion Joining is easily achieved by soldering and resistance welding When alloyed with copper and titanium, zinc sheet is very creep resistant and can be used in functional applications; examples include architectural applications such as in roofing and siding Rolled zinc is produced in seven basic alloys and also as pure zinc (Table 6) Variations in chemistry and rolling conditions produce a variety of properties

Table 6 Nominal compositions of rolled zinc alloys per ASTM B 69

Common

designation

UNS number

Zn-0.08Pb Z21210 0.001 max 0.10 max 0.005 max 0.012 0.001 0.001 Sn bal

Zn-0.06Pb-0.06Cd Z21220 0.005 max 0.05-0.10 0.05-0.08 0.012 0.001 0.001 Sn bal

Zn-0.3Pb-0.3Cd Z21540 0.005 max 0.25-0.50 0.25-0.45 0.002 0.001 0.001 Sn bal

Zn-1Cu Z44330 0.85-1.25 0.10 max 0.005 max 0.012 0.001 0.001 Sn bal

Zn-1Cu-0.010Mg Z45330 0.85-1.25 0.15 max 0.04 max 0.015 0.001 0.006-0.016 Mg

Zn-0.8Cu Z40330 0.70-0.90 0.02 max 0.02 max 0.01 0.005 0.02 Ti bal

Superplastic zinc, which contains 21 to 23% Al and a small amount of copper (0.4 to 0.6%), can be easily formed into

complex shapes and displays the characteristics of plastics or molten glass at temperatures of 250 to 270 °C (480 to 520

°F) The very fine grain size produced by processing at 275 to 375 °C (525 to 705 °F) followed by quenching and aging gives superplastic zinc its unique properties Different grades of superplastic zinc, such as air-cooled or surface-cooled varieties, have different levels of strength When superplastic zinc is reheated to above 275 °C (527 °F) and slowly cooled

to room temperature, the superplastic properties disappear Detailed information about superplasticity is available in the

article "Sheet Formability Testing" in Mechanical Testing, Volume 8 of ASM Handbook, formerly 9th Edition Metals Handbook