COLD RESISTANT METAL MATERIAL LECTURER

Refrigerant material is one of the very important thermoelectric materials. Thanks to coldresistant materials, we can easily create equipment, machine details and items that can be used when affected at very low temperatures. In the era of industrialization and modernization today, in Vietnam, domestic enterprises and foreign enterprises investing in Vietnam have been developing, industries such as cold industry, metallurgy, chemistry…. has had strong development steps. Cold resistant material is one of the indispensable materials in the industry

HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

REPORT PROJECT SUBJECT: THERMAL MATERIALS TOPIC: COLD RESISTANT METAL MATERIAL

LECTURER:

Student name (Group 4):

HO CHI MINH, OCTOBER, 2020

TABLE OF ASSIGNED WORK

research and presentation chapter 3

and chapter 2

LECTURER FEEDBACK

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SIGNATURE

CHAPTER 1: INTRODUCTION 5

1.1 Reason to choose the topic 5

1.2 Target 5

1.3 Object of study 5

1.4 Evaluation method 5

CHAPTER 2: CONCEPT AND GENERAL PROPERTIES OF COLD RESISTANT METAL MATERIALS 6

2.1 Cold resistant metal material concept 6

2.2 General properties of cold-resistant metal materials 6

2.2.1 Flexibility, impact 6

2.2.2 Permitted Application Temperatures: 9

2.2.3 Elongation of metal 11

2.2.4 Thermal conductivity 12

2.2.5 Specific heat 13

2.2.6 Conductivity 14

CHAPTER 3: CLASIFLICATION OF COLD RESISTANT METAL MATERIALS .16

3.1 Classify base on the common used 16

3.1.1 Carbon steel 16

3.1.2 Stainless steel 17

3.1.3 Aluminium 18

3.1.4 Duralumin 19

3.1.5 Silumin 19

3.1.6 Copper 19

3.2 Classify base on temperature 20

3.2.1 Materials suitable down to -45 °C 21

3.2.2 Materials suitable down to -75 °C 22

3.2.3 Materials suitable down to -100 °C 22

3.2.4 Materials suitable down to -196 °C 23

3.2.5 Materials suitable below -196 °C 24

3.2.6 To sum thing up 25

CHAPTER 4: APPLICATION OF COLD RESISTANT METAL MATERIAL 26

4.1 In the heat and cold technology industry 26

4.2 In other industries 26

CHAPTER 5: THE REAL SYSTEM OF THERMAL METAL MATERIALS 27

REFERENCES 28

CHAPTER 1: INTRODUCTION

1.1 Reason to choose the topic

Refrigerant material is one of the very important thermoelectric materials Thanks

to cold-resistant materials, we can easily create equipment, machine details and itemsthat can be used when affected at very low temperatures

In the era of industrialization and modernization today, in Vietnam, domesticenterprises and foreign enterprises investing in Vietnam have been developing,industries such as cold industry, metallurgy, chemistry… has had strong developmentsteps Cold resistant material is one of the indispensable materials in the industry

Get a better understanding of the structure and properties of cold resistant metals

As well as learn about the application of cold-resistant metals in the thermalengineering industry in particular, in life and production in general

CHAPTER 2: CONCEPT AND GENERAL PROPERTIES OF COLD

RESISTANT METAL MATERIALS

2.1.

Cold-resistant materials are materials that retain enough toughness at lowtemperatures from 0 ÷ -269C (273 ÷ 4K)

2.2 General properties of cold-resistant metal materials

The mechanical properties of materials are always more or less dependent on thetemperature When materials are used at temperatures of -40 ° C or below, specialattention should be paid to the change in mechanical properties, especially themechanical properties

2.2.1 Flexibility, impact

Black and non-ferrous metals have the following general mechanical propertieschanges: when the temperature decreases, the tensile strength and tensile strengthincrease so that they do not cause obstacles and need not be noted When thetemperature decreases, the elongation and the impact plasticity decrease rapidly.Whenusing materials at low temperatures it is necessary to choose suitable materials withimpact ductility at operating temperatures not less than 30 Nm/cm2 (figure 1-2)

Figure 2-1 Dependence of impact ductility and low temperature [3]

a) General variable lines of 3 categories;

b) Impact resistance of some steels

Materials can be classified into three groups:

- Group one (curve 1) has high impact ductility, less dependent on temperature.When the temperature decreases the impact ductility can decrease, stay the same evenslightly increase

- Group two (curve 2) has the most special properties, including three phases:

+ Stage one (part of curve 2) is plastic deformation, impact strength decreasesslightly when temperature decreases

+ Phase two (part b) is the changing phase, the impact strength decreases rapidlyand dramatically

+ Stage 3 (part c) is brittle deformation, impact resistance is still very small

- Group three (curve 3) has properties similar to group one but has low impactductility from the outset

 Figure 2-1a shows the general variation curve of impact plasticity of these threegroups

 Figure 2-1b shows the variation in impact ductility depending on lowtemperature of some carbon steels and alloys

Table 2-1: Introduction of impact ductility of some black metal steels [3]

0,3-1,5Nm/cm2 0,2-0,5

Nm/cm2

Nm/cm2

140- 160Nm/cm2

190

Nm/cm2

195Nm/cm2

115Nm/cm2

110

m2 ở 183°C

-45Nm/cm2

2.2.2 Permitted Application Temperatures

For designers and use of cold materials, the allowable material operatingtemperature for each type of load is a very significant quantity It quickly answerswhat is the application temperature limit of that material The application temperaturelimit depends on many factors such as the type of lattice, the chemical composition,the manufacturing method, the heat treatment method of the material as well as thesubstance and the magnitude of the counterload with material

Table 2-2: Application temperatures for certain materials in a dynamic orstationary state [3]

Table 2-2 gives some literature on the application temperature limits of somematerials under static and dynamic loads.

Through Table 2-2, it is clear that at very low temperatures, especially in cryoengineering, machines and equipment must use aluminum, copper, nickel, their alloys

Material

Application temperature limits, ° C at load type

Cast steel (not alloy) Can not be used -30°c -70°C(*)

Austenitic Cromniken

cast steel

Cast aluminum

Non-welded steel according to

Copper alloys (brass,

nickel iron brass, zinc

(*) Depending on the impact strength

and nickel chromium austenitic alloy steel They have no application temperaturelimitations in both static and dynamic loads.

2.2.3 Elongation of metal

When using materials at very low temperatures, the designers must pay attention tothe thermal expansion of the material, including that under compression and underpressure, which is not covered herein Figure 2-2 shows the thermal expansion ofsome metals

Figure 2-2: a) The expansion depends on the temperature [3]

Figure 2-2: b) The relative length shrinkage ∆L / L in the low mold temperature range

T = 273K [3]

- Figure 2-2a shows that lead has the highest thermal expansion followed byaluminum, copper, nickel and finally construction steel and carbon-impregnated steel(curve 2)

- Figure 2-2b shows the relative length shrinkage in the temperature range from 0

to 273K, taking the point T = 273 K as the landmark Compared with figure 1-3a, thecurves in Figure 2-2b will have the opposite order, starting from bottom up to be lead(not shown here) then aluminum, copper and nickel The number 1 curves represent36% nickel alloy steel, No 2 for general construction steel, No 3 for 'stainless high-alloy' steel 4 for platinum copper (alloy of 60% copper, 25% nickel and 15% zinc)

2.2.4 Thermal conductivity

Figure 2-3 shows the properties of curves of the thermal conductivity coefficients

of very high purity, low purity metal materials and of alloys Very high purity metalsachieve a lower purity metal maximum

Figure 2- 3 General properties of the curves of the thermal conductivity

coefficients of very high purity metal of lower purity and of alloy [3]

The thermal conductivity of pure metals has the highest value, and decreasesrapidly if the metal contains impurities Thermal conductivity coefficient of smallalloys hc «i quite a lot and depends a lot on the composition of the alloy Thermalconductivity coefficients of pure metals, alloys, non-metals, fluids and gases are in thefollowing ranges: X, unit W (m / K);

Figure 2-4: Thermal conductivity A of some materials ~ X of barometric

at easily comparable standard pressure [3]

2.2.5 Specific heat

Express the temperature dependence of the specific heat of some materials over thelow and very low temperature range, at the absolute zero point of the specific heat ofthe materials is zero The specificity of metals and alloys is only equal to, even lessthan, the isotropic specific heat of the gases

Observed in the figure at about 140K or more, aluminum, iron and copper have asofter curve than about 140K or less The specific heat capacity of aluminum is 2times greater than that of copper and iron and that of lead is up to 4 times From thetemperature range of 300K down to 40K, the specific heat of the lead decreasesalmost negligibly, but in the range from 40K to 0K, it decreases very quickly

Figure 2.5: The temperature dependence of the specific heat of some materials in

the low and very low temperature range [3]

Figure 2-6: Resistance of some metals depends on temperature [3]

Figure 2-6 shows the change in resistance of some metals depending on thetemperature The vertical axis is the value of the resistance ratio measured at anytemperature T over the original pointer measured at 273 ° C Figure 1-7 shows a rapiddecrease in resistance when the temperature drops from 1 to 10K, the resistance of amaterial disappears, the material becomes superconducting

In summary, the main metal materials used in refrigeration are iron, copper,aluminum and their alloys Considering the multi-component relationship: metallicmaterials - nonmetals - solvents - lubricating heads - wet and the secondary product, itcan be said that most materials are suitable, only a few materials Caution should beexercised or disposed of for specific refrigerant metals normally used up to -50 ° C,but 50 ° C or less should pay attention to the strength of the material material, specialbrittle deformation and impact plasticity

CHAPTER 3: CLASIFLICATION OF COLD RESISTANT METAL

-No minimum content is specified or required for chromium, cobalt, molybdenum,nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to beadded to obtain a desired alloying effect

-The specified minimum for copper does not exceed 0.40%

- The maximum content specified for any of the following elements does notexceed the percentages noted: manganese 1.65%; silicon 0.60%; copper 0.60%

Figure 3.1 Carbon steel pipe [6]

Type:

a) Low-carbon steel: Low-carbon steels display yield-point run out where the

material has two yield points The yield point is the point on a stress-strain curve thatindicates the limit of elastic behavior and the beginning of plastic behavior Prior tothe yield point, a material will deform elastically and will return to its original shapewhen the applied stress is removed Once the yield point is passed, some fraction ofthe deformation will be permanent and non-reversible and is known as plasticdeformation The first yield point (or upper yield point) is higher than the second andthe yield drops dramatically after the upper yield point If a low-carbon steel is onlystressed to some point between the upper and lower yield point then the surfacedevelops Lüder bands Low-carbon steels contain less carbon than other steels, 0.05 to0.25% carbon, and easier to cold-form, making them easier to handle

b) Mild steel: Mild steel contains approximately 0.05–0.30% carbon making it

malleable and ductile Mild steel has a relatively low tensile strength, but it is cheapand easy to form; surface hardness can be increased through carburizing

c) High-tensile steel: High-tensile steels are low-carbon, or steels at the lower end

of the medium-carbon range, which have additional alloying ingredients in order toincrease their strength, wear properties or specifically tensile strength These alloyingingredients include chromium, molybdenum, silicon, manganese, nickel andvanadium Impurities such as phosphorus or sulphur have their maximum allowablecontent restricted High-carbon steel approximately 0.6 to 1.0% carbon content

d) Higher-carbon steels: Carbon steels which can successfully undergo

heat-treatment have a carbon content in the range of 0.30–1.70% by weight Traceimpurities of various other elements can have a significant effect on the quality of theresulting steel

3.1.2 Stainless steel

Definition:

Stainless steel is a group of iron-based alloys that contain a minimum ofapproximately 11% chromium, a composition that prevents the iron from rusting, as

well as providing heat-resistant properties Different types of stainless steel includethe elements carbon (from 0.03% to greater than 1.00%), nitrogen, aluminium, silicon,sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum Specific types

of stainless steel are often designated by a three-digit number, e.g., 304 stainless.

Stainless steel's resistance to ferric oxide formation results from the presence ofchromium in the alloy, which forms a passive film that protects the underlyingmaterial from corrosion attack, and can self-heal in the presence of oxygen

Type:

1 Austenitic stainless steel: Is the largest family of stainless steels, making up

about two-thirds of all stainless steel production They possess an austenitic microstructure, which is a face-centered cubic crystal structure This micro structure isachieved by alloying steel with sufficient nickel and/or manganese and nitrogen tomaintain an austenitic micro structure at all temperatures, ranging from the cryogenicregion to the melting point Thus, austenitic stainless steels are not hard enable by heattreatment since they possess the same micro structure at all temperatures

2 Ferritic stainless steels: Ferritic stainless steels possess a ferrite micro

structure like carbon steel, which is a body-centered cubic crystal structure, andcontain between 10.5% and 27% chromium with very little or no nickel This microstructure is present at all temperatures due to the chromium addition, so they are nothard enable by heat treatment They cannot be strengthened by cold work to the samedegree as austenitic stainless steels They are magnetic

3 Martensitic stainless steels: Martensitic stainless steels offer a wide range of

properties and are used as stainless engineering steels, stainless tool steels, and resistant steels They are magnetic, and not as corrosion-resistant as ferritic andaustenitic stainless steels due to their low chromium content They fall into fourcategories Replacing some carbon in martensitic stainless steels by nitrogen is arecent development The limited solubility of nitrogen is increased by the pressureelectroslag refining (PESR) process, in which melting is carried out under highnitrogen pressure Steel containing up to 0.4% nitrogen has been achieved, leading to