Special irons, generally of high carbon content, but with a very low content of residual elements are also available, their main use being for the production of nodular graphite iron.. C
Trang 2Mechanical propefies-dand east-(SI units
Tensile strength (min), MPa (tonf in-')
0.2% proof stress (min), MPa (tonf in-')
Elongation % (min) (5.65JSO)
Mechanical properties-chill cast- (SI units
Tensile strength (min), MPa (tonf in-')
0.2% proof stress (min), MPa (tonf in-2)
Elongation % (min) (5.65&)
t, Imperial units fol
Trang 3Mechanical properties-sand cas-(SI units ti
Tensile strength (min), MPa (tonf in-2)tt
0.2% proof stress (min), MPa (tonf in-')
Elongation % (min) (5.65JS0)
Mechanical properties-chill cas-(SI units fi
Tensile strength (min), MPa (tonf in-')
0.2% proof stress (min), MPa (tonf in-')
I
Trang 4ASTM designation
Tensile strength (min), MPa (tonf in-’)
0.2% proof stress (min), MPa (tonf in-’)
Mechanical properties-sand cas- (SI units
Tensile strength (min), MPa (tonf in-2)
0.2% proof stress (rnin), MPa (tonf in-’)
- ,t, Imperial units following in brackets
TS-Stress relieved only
TE-Precipitation treated only
TB-Solution treated only
TF-Solution and precipitation treated
t C P General purpose alloy
SP Special purpose alloy
? Permanent mould=pravity die casting
Not suitable
Typical high pressure die-cast properties
7 Damping capacity ratings
A=Outstanding; better than grey cast iron
3
210 12s
3
Better foundability than AZ91 with superior elevated temperature properties
C=Not recommended where strength at elev temps is likely to be an important consideration
t t 1 MPa=1 Hmm-’=006475 tonfin-’
5 Ability to fill mould easily A, 8 , C, indicate decreasing castabilily $1 SO, or CO, atmosphere
N
6
Trang 5Table 26.36 MAGNESIUM-ZIRCONIUM ALLOYS
Inherently fine grained (0.015-0.035 mm chill cast)
9
B
Weidability (Ar-Arc Process)
Relative damping capacity**
Strength at elevated temperaturett
Resistance to creep at elevated temperature
-
Good in sand and permanent moulds!
Marked Very appreciable
B
Not recommended BIC
C Poor Moderate 1.81
640
560
- 0.75-1.75
A Moderate BlC
B Moderate Moderate 1.84
640
510
- 2.54.0 0.41.0 0.03 0.005
A Very good
B
A Good up to 250°C Moderate 1.80
640
545
Trang 62
330 ionto precede precipitation treatment
Mechanical properties-sand cast-SI units (Imperial units in brackets)
Tensile strength min, MPa (tonf in-')
0.2% proof stress min, MPa (tonf in-')
230 (14.9)
145 (9.4) Elongation, "/, (5.65$,) min 5
Mechanical properties-chill cast-SI units (Imperial units in brackets)
Tensile strength min, MPa (tonf in-') 245 (15.9)
0.2% proof stress min, MPa (tonf in-2)
10
250 max Air cool
High degree of pressure tightness at room and elevated
Trang 7Table 26.35
Inherently fine grained-continued
Speeifications BS 2970: 1989
BSS L series
Equivalent DTD
MAGITE(SP) 5005A
MAG9TE(SP) 5015A
Weldability (Ar-Arc process)
Relative damping cpacity**
Strength at elevated temperaturett
Resistance to creep at elevated temperature
B
A Good up to 350°C Moderate 1.85
645
550 72&810
16
315 Air cool
5.M.O 0.20 1.5-2.3
0.4-1 .o
0.03 0.005 0.01 0.01 0.15
-
Similar to MAG5 Verry little Low
B Fair
C
B Fair Moderate 1.87
630
520 72&810
2 followed 16
5.5-6.0
- 2.CL3.0 O.&l .o
0.03 0.005 0.01 0.01 0.15
-
Good Negligible Virtually none
A Very good***
B K
C Poor Moderate 1.87
625
516 72CL810
30 for 12 mm sctn
70 for 25 mm sctn 480ttq
Air blast or water spray
48 or 72
Trang 8Time, h
Temperature, “C
2
350 Air cool
Mechanical properties-sand cast-SI units (Imperial units in brackets)
Tensile strength min, MPa (tonf in-’)
0.2% proof stress rnin, MPa (tonf in-’)
185 (12.0)
85 (5.5) Elongation, ”/, (5.65JS0) min 5
Mechanical properties-chill cas-SI units (Imperial units in brackets)
Tensile strength min, MPa (tonf in-’)
0.2% proof stress min, MPa
185 (12.0)
85 (5.5) Elongation, % )5.65&,,) min 5
Pptn treatment affords stress -
ductility and excellent fatigue resistance
Structural parts aircraft, etc
WE54 WE54
WE43 WE43
0 4 1 .o
0.03 0.005 0.01 0.01 0.15
-
0.2 2.0-3.0 2.0-3.0:
0 4 1 .o
0.03 0.005 0.01 0.01 0.15
-
0.2 2.0-3.0 1.8-2.5:
0.41.0 0.03 0.005 0.01 0.01 0.15
-
0.3 0.1 2.54.0
0 4 1 .o
0.03 0.005 0.01 0.01 0.15
-
0.2 1.3-1.7 1.5-3.0:
0.41 .o
- 0.05-0.10 0.005 0.01 0.01 0.15
0.2 2.M.0777 0.4-1.0 0.03 0.005 0.01 0.01 0.15 4.75-5.5
-
-
0.2
- 2.u.4nnii
- 0.41.0 0.03 0.005 0.01 0.01 0.15
3.7-4.3
Trang 9Elektron designation
ASTM designation
Weldability (Ar-Arc process)
Relative damping capacity**
Strength at elevated temperaturett
Resistance to creep at elevated
than MSR types Good
Slight
B Very good BlC
A Good up to 200°C Moderate 1.81
640
550 72k810
Slight
B Very good
A Good up to 200°C B/C
Moderate 1.82
640
550 720-81 0
Slight
B Very good
A Good up to 200°C Moderate 1.81
640
550 72C810
B/C
Neiligible Slight
Very good B/C
A Good up to 350°C Good up to for short time 200°C applications
B Very good BlC
A Very good
up to 250°C Excellent 1.85
640
550 720-810
8 52511:
Air cool
16
250
Good Very little Slight
B Very good BIC
A Very good
up to 250°C Excellent 1.85
640
550 720-8 10
8 52511:
Trang 10Time, h
Temperature, "C
1
510 followed by above quench and age
followed by above followed by above followed by above quench and age aircool and age quench and age
Mechanical properties-sand cast-SI units (Imperial units in brackets)
Tensile strength min, MPa
Mechanical properties-chill cast-SI units (Imperial units in brackets)
Tensile strength min, MPa
0.2% proof stress min, MPa
(tonf in - 2 ) 170 (11.0) 185 (12.1) 175 (11.3) Usually sand 170
(up to 250°C) short time resistance at but less applications
resistance short time
*See footnote to Table 26.34
t See footnote to Table 26.34
1 Neodymium-rich rare rearths (others Ce-rich)
7 See footnote to Table 26.34
**See footnote to Table 26.34
SSee footnote to Table 26.34
tt See footnote to Table 26.34
$1 SOz or CO, atmosphere
WCastings to be loaded into furnace at operating temperature
*** But only before hydriding treatment
ttt In hydrogen at atmospheric pressure
$11 Thorium containing alloys are being repiaced by alternative magnesium based alloys
777 Neodymium and heavy rare earths
Excellent strength
up to 250°C for
long time applications
Excellent corrosion resistance
N
c
Trang 1126.7 Zinc base casting alloys
Table 26.36 ZINC BASE ALLOYS-COMPOSITIONS
Composition % (Single figures indicate maximum d e w s otherwise stated)
0.015-0.030
-
-
- Remainder
25-28 2.0-2.5 0.01-0.02 0.10 0.005
Dimensional changes after casting (mm m-')
After 5 weeks -0.32 - 0.69 Shrinkage 0.03 % after Shrinkage 0.005 % after Shrinkage 0'005 % after
After 6 months - 0.56 - 1.03 100 days 30 days ambient, and 30 days ambient, and
After 5 years -0.73 - 1.36 0.03 % after 1 OOO days 0.015 % after 1 OOO days
followed by growth, i.e
zero change after 1 OOO
days
shrinkage then growth to
+0.1% after 1 OOO days
Dimensional changes after stabilizing heat treatment (mm m-') 16 h at 100°C+5"C-air cool)
Agter 5 weeks -0.20 - 0.22
After 3 months -0.30 - 0.26
After 2 years -0.30 - 0.37
Ageing At RT all the alloys show little decrease in strength
Exposure to elevated temperature (100°C) may result in
decreases of up to 30%
Applications and Extensive use where a large Used for pressure diecastings General purpose sand and
uses number of strong requiring creep resistance gravity casting alloy and a
dimensionally accurate metal Gravity castings requiring higher strength diecasting
components required, e.g
components of cars, domestic quality electroplating bearing properties
appliances, business
machines, record players,
hydraulic and pneumatic
valves, toy models
excellent fluidity or very high alloy Good wear and
3.54.3 2.5-3.2 0.03-0.06 0.075
Strongest of the alloys Used
in the sand, gravity or pressure diecast form for applications where its strength is required Best wear and bearing properties
(comparable to SAE660
bronze)
Pressure die, sand and gravity die cast For applications where hardness
is an advantage Sheet metal forming dies, moulds for plastics$, zip fastener sliders
Trang 12Table
Pressure Pressure Gravitv Pressure Sand Gravitv Pressure
die cast cast die cast cast cast die cast
Sand Gravity Pressure Sand Pressure cast cast die cast cast die cast
6.1
4 W 2 5 27.4
41 8
110
26 6.5
3 24 379-388
6.3 375-404 420-500 23.2
435
115 27.7 6.2
240
210
86 1-2
90
-
Very good
6.3
3 7 5 4 M
4 1 M 3 0 23.2
435
115 21.7 6.2
6.0 377-432 450-550 24.1
448
116 28.3 6.1
300
210
82 1-2
95 2s
Good
6.0
377432 450-550 24.1
448
116 28.3 6.1
330
260
82 1.5-2.5
90
-
Good
6.0 377-432 450-500 24.1
448
116 28.3 6.1
400
320
82 4-7
100
30
Good (cold
375484 372-484 5CG-600 5 W 0 0 26.0 26.0
5.0 375-484 SW550 26.0
534
126 29.7 5.8
425
370
78 2.C-3.5
120
12
Good (cold
6.6 39e379 420-440 27.8
41 8
-
25 6.8
4 W 2 5 21.8
41 8
1 05
25
Trang 13Table 2637 STEEL CASTINGS FOR GENERAL ENGINEERING
composition (maxima unless stated) Grade Description
0.15
0.25 0.1 o/o 18 0.40/0.50 0.50/0.60 0.20 0.20 0.18 0.25 0.20 0.20
0.1 O/O 15
0.60 0.50 0.050 0.60 0.50 0.050 0.60 0.60/1.00 0.050 0.60 1.00 0.050 0.60 1.00 0.050
0.20/ 0.50/1.00 0.050 0.60
0.60 0.50/0.80 0.050 0.60 0.40/0.70 0.050 0.75 0.30/0.70 0.040
0.75 0.40/0.70 0.040 1.00 0.30/0.70 0.040
0.45 0.40/0.70 0.030
0.25' 0.15' 0.402
0.25' 0.15' 0.402 0.25' 0.15' 0.402 0.25' 0.15' 0.402 0.25' 0.15' 0.402 0.25' 0.45/0.65 0.402
1.00/1.50 0.45/0.65 0.40' 2.00/2.75 0.90/1.20 0.40' 2.50/3.50 0.35/0.60 0.40' 4.00/6.00 0.45/0.65 0.40'
Trang 14QUENCHING (OR HARDENING) AND TEMPERING
Heating above the critical range, but not so high as for annealing or normalizing, and rapidly cooling in water, oil or air blast followed by reheating to a temperature below the critical range until the desired properties are achieved followed by air cooling, furnace cooling (if stress relief is also required) oe cooling in water (to minimize temper embrittlement) Gives highest physical properties; high tempering temperatures usually give lower strength but higher elongation and impact values Normally preceded by annealing
SURFACE HARDENING
Heating the surface layers by flame or induction to a temperature above the critical range and quenching by water jets following the heat source or by immersion
Tensile Lower yield E1 % Bend test Impact Limiting
condition MPa MPa JS,, angle radius J HE mm
Trang 1526-64
Table 26.37 STEEL CASTINGS FOR GENERAL ENGINEERING-continued
Casting alloys and foundry data
Composition (maxima unless stated) Grade Description
High alloy for
high temp use
High alloy for
high temp use
0.45/0.55 0.75 0.50/1.00 0.060 0.80/1.20 - - - 0.55/0.65 0.75 0.50/1.00 0.060 0.80/1.50 0.20/0.40 - - 1.00/ 1.00 11.0
0.15 1.00 1.00 0.20 1.00 1.00 0.10 1.00 1.00 0.12 1.50 2.00 0.03 1.50 2.00 0.08 1.50 2.00 0.08 1.50 2.00 0.08 1.50 2.00 0.03 1.50 2.00 0.08 1.50 2.00 0.08 1.50 2.00 0.08 1.50 2.00 0.08 1.50 2.00 1.00 2.00 1.00 0.25 2.00 1.00 0.20/0.40 2.00 2.00 0.50 2.50 2.00 0.50 2.00 2.00 0.50 3.00 2.00 0.50 3.00 2.00 0.75 3.00 2.00 0.75 3.00 2.00 0.75 3.00 2.00 0.20/0.45 1.50 2.50 0.20/0.50 1.50 2.00 0.30/0.50 1.50 2.00 3.35/0.55 1.50 2.00 0.35/0.55 1.50 2.00 1.00/2.00 2.00 1.00
17.0/21.0 3.00/4.00 17.0/21.0 2.00/3.00 25.0/30.0 1.50 25.0/30.0 1.50 12.0/16.0 - 17.0/22.0 1.50 22.0/27.0 1.50 25.0/30.0 1.50 22.0/27.0 1.50 17.0/23.0 1.50 13.0/20.0 1.50 15.0/25.0 1.50 10.0/20.0 1.50 24.0/28.0 1.50 24.0/28.0 1.50 24.0/27.0 1.50 13.0/17.0 1.50 17.0/21.0 1.50
10.0 min 10.0min Nb8x
6.00/10.0 - 10.0/14.0 - 8.00/12.0 - 17.0/22.0 - 23.0/28.0 - 30.0/40.0 - 36.0/46.0 - 55.0/65.0 - 11.0/14.0 N 0.2 11.0/14.0 - 19.0/22.0 - 33.0/37.0 - 37.0/41.0 -
For each 0.01 % carbon below the max an increase of 0.04% Mn is permitted np to a max of 1.10%
Residual elements: total shall not exceed 0.80%
Only mandatory if specified by the purchaser
Either a bend test or an impact test may be specified
Mn/C ratio shall be greater than 3:1
The heat treatment to be applied shall be at the discretion of the manufacturer
Properties in the blank carburised and heat treated condition
Residual elements
The maximum carbon content may be increased to 1.35% by agreement
Not applicable to free machining steels
Trang 16Steel castings 2665
Tensile Lower yield E l % Bend test Impact Limiting
condition MPa MPa JSo angle radius J H B mrn
11 For free machining grades the minimum elongation shall he 12%
12 Gy agreement the Nh may he replaced by Ti in the range 5 x C/0.700,/,
13 If required with specified low temperature impact properties the carbon content shall he 0.06% max and the niobium 0.90% max
14 The minimum value for a free version shall be 460 Nlmm’
15 1 % PS value
16 If a free machining grade is specified the sulphur content may be as high as 0.5 % and/or other suitable elements may he present Free machining grades shall be denoted by the letter F after the grade designation
17 Properties minima unless stated
18 HT-Heat treated, A-annealed, N-normalised C-As cast, T-tempered, H & T-hardened and tempered, WA-water quenched, ST-solution treated
Trang 172666
Table 2638a STEEL CASTINGS FOR PRESSURE PURPOSES
Casring alloys and foundry data
0.20 0.20/ 0.50/1.00 0.040 0.Z4 0.45/0.65 0.404 Cu 0.304 0.60
0.50 0.35/
0.55
1.0 1.0 1.0 1.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0 2.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0
0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.030 0.040 0.040 0.040
11.5/13.5 - 11.5/13.5 0.60 17.0/21.0 - 17.0/21.0 - 17.0/21.0 - 17.0/21.0 1.0/1.75 17.0/21.0 2.0/3.0 17.0/21.0 2.0/3.0 17.0/21.0 2.0/3.0 17.0/21.0 2.0/3.0 17.0/21 .O 3.0/4.0 17.0/21.0 3.0/4.0 20.0/24.0 3.0/6.0 19.0/22.0 2.0/3.0 24.0/27.0 1.506 13.0/17.0 1.506
1 .o Cu 0.306 3.4/4.2 - 8.0min - 8.0min -
8.5 min Nb8 x C/ 8.0min - 10.0 min - 10.0 min - 8.0 min - 10min Nb8xC/ 10.0 min - 10.0min - 20.0/26.0 Cu 2.0 26.5/30.5 Cu 3.0/4.0 19.0/22.0 - 33.0/37.0 -
1,011.1 2
1.012
Nb 0.50
Trang 19Table 26.38b STEEL CASTINGS FOR PRESSURE PURPOSES-ELEMENTAL TEMPERATURE PROPERTIES-E DESIGNATION
Minimum lower yield stress Rel or 0.2% proof stress, Rp0.2, MPa at a temperature in "C of Designation
For each 0.01 % carbon below the maximum an increase of 0.04% manganese will be permitted up to a maximum of 1.10%
For each 0.01 % carbin below the maximum an increase of 0.05% manganese will be permitted up to a maximum of 1.60%
Ni +Cr+ Mo + C a = 0.80% max
Ni +Cr +Cu = 0.80% max
Either a bend test or an impact test may be specified but not both
Residual elements
This value may be increased to 15 % min, subject to agreement a t the time of enquiry and order
When specifically ordered
When used for deoxidation shall not exceed 0.25 kg/t
1 % Proof stress
C content 0.06 max and Nh 0.9 max when low temperatnre properties are specified
Ti 5XC/0.70 may be substituted for Nb by agreement
Values at 20°C and 50°C are included for design purposes only and are not subjected to verification All values except those at 50°C that are obtained by interpolation are based on tests according t o
Bs 3688 and thus values at 20°C difler from the corresponding room temperature values given in this specification
Only apply to sections <32 mm
Properties minima unless stated
A-Annealed, N-normalised, T-tempered, Q & T-quenched and tempered, H & T-hardened and tempered, ST-solution treated
Trang 202&39 WELDABLE CHROMIUM-NICKEL CENTRIFUGALLY CAST
Composition (maxima unless stated)
1 1F'
2 2F'
3 3F'
0.04/0.09
0.04/0.09
0.04/0.09
0.04/0.09 0.25/0.35 0.25/0.40 0.35/0.45 0.15 0.40/0.5@
0.35/0.55 0.15 0.10
1 .OO 1.50
1 00
1.50
1 .00
1.50 0.50/1.50 0.50/1.50 0.50/1.50 0.50/1.50 0.50/1.50 1.50/2.00 0.50/1.50 0.30/1 .OO
2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 1.50
0.030 0.040 0.030
0.040
0.030 0.040 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030
0.030 0.040 0.030
0.040
0.030 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.030
17.0/19.0 0.50 17.0/20.0 - 17.0/19.0 0.50 17.0/20.0 - 16.0118.0 2.00/2.75 17.0j20.0 2.OOj3 .00
18.0/21.0 0.50 23.0/27.0 0.50 23.0/27.0 0.50 23.0/27.0 0.50 17.0/21.0 0.50 17.0/21.0 0.50 17.0/21.0 0.50 19.0/22.0 0.50
11.0/13.5 - 8.0 min - 11.5/14.0 Nb 8xC/1.0 8.0 min
12.5/15.0 - 8.00 min - 9.00/11.5 - 11.5/14.0 - 18.0/22.0 - 19.0/23.0 - 33.0/37.0 - 33.0/37.0 - 33.0/37.0 - 30.0/34.0 -
mm
1 For use where ferrite content is to he within a specified range to facilitate welding
2 By agreement this grade can be supplied to a C range of 0.35/0.45%
3 Above 20 mm wall thickness properties shall be agreed between manufacturer and purchaser
4 Properties minima unless stated
Trang 2126-70 Casting alloys and foundry data
Table 26.40 AEROSPACE SERIES-STEEL CASTINGS- 1973/1974
Compositions (maxima unless stated)
- Cu 0.3
- Cu 0.3 3.5 Cu 0.3 0.4 Cu 0.3
v 0.02
Sn 0.03 0.4 Cu 0.4
0.25 0.75 0.6 0.18 0.6 0.6 0.3 0.75 0.6
0.035 0.25' 0.15' 0.035 0.25' 0.15' 0.35 1.2 0.4 0.035 3.5 0.6 0.035 0.25 0.15 0.020 3.5 0.7
0.08 2.0 2.0
0.08 1.5 2.0
0.08 1.0 1.0
0.025 1.3 0.7 0.025 1.3 0.7 0.025 15.5 2.5 0.025 15.5 2.5 0.04 25.0 - 0.04 21.0 - 0.04 20.0 3.0 0.04 17.5 -
3.0 Cu 0.4 3.0 Cu 0.4 6.0 Cu 3.5
Nb 0.5 6.0 Cu 3.5
Nb 0.5
13.0 W 3.5 12.5 Nb 1.0 12.5 Nb 1.0 5.0 Cu 3.0 Ta+Nb 0.4 17.5 A1 0.15
c o 11.0
Ti 0.6 0.03 0.1 0.1 0.01 0.25 4.9
Table 26.41a INVESTMENT CASTINGS-CARBON AND LOW ALLOY STEELS
0.40/1.00 0.035 0.30' 0.10' 0.40/1.00 0.035 0.30' 0.10' 0.40/1.00 0.035 0.30' 0.10' 1.20/1.70 0.035 0.30' 0.10'
0.30/0.60 0.035 2.50/3.50 0.35/0.60 0.50/0.80 0.035 0.30' 0.10'
0.401
0.40'
0.40' 0.40'
- 0.40"
0.40'
-
Cu 0.304
Cu 0.30'
Trang 22Total residual elements shall not exceed 0.8%
A restricted range of oncomposition may be agreed if welding or brazing is intended Castings in composition range are subject to Patent applications
Hardness values ane for maraged castings
Angle of bend 120" Radius of bend 1 3 , t=teckiness of test piece
Angle of bend 120" Radius of bend 3, t =techiness of test piece
Treatment
Tensile strength
1160
6201770
1953 21fi3
2691321 '
341/388' 1791223'
1521201 2
-
Trang 2326-72
Table 26.41a INVESTMENT CASTINGS-CARBON AND LOW ALLOY STEELS
Casting alloys and foundry data
BS 3146 Description
CLA9 C Steel for case 0.10/0.18 0.20/0.60 0.60/1.00 0.035
CLAlO 3 Ni for case O.lO/O.lX 0.20/0.60 0.30/0.60 0.035
Sn 0.034 0.80/1.20 0.104 0.404 Cu 0.304 0.80/1.50 0.20/0.40 0.404 Cu 0.304
0.304 0.20/0.30 1.50/2.00 Cu 0.304
v 0.024
Noses:
1 Residual elements-total not to exceed 0.80%
2 When specifically requested
3 For information only
4 Residuals
Table 26.41b INVESTMENT CASTINGS-CORROSION AND HEAT RESISTING STEELS
17.0/20.0 2.00/3.00 10.0 min -
17.0/20.0 2.00/3.00 10.0 min Nb 8 xC/
22.0/27.0 - 17.0/22.0 - 15.0/25.0 - 36.0/46.0 - 10.0/20.0 - 55.0/65.0 - 20.0/25.0 - 55.0/65.0 - 20.0/25.0 - lO.O/lS.O W 2.50/
1.10
1.10
3.50 20.0/25.0 - 10.0/18.0 W 2.50/
3.50 12.5/15.5 0.50/2.50 3.00/6.00 Cu 1.00/
3.50
Nb 0.50 25.0/21.0 1.15/2.25 4.75/6.00 Cu 2.75/
3.25
N 0.10 15.5/16.7 - 3.60/4.60 Cu 2.80/
3.50 Nb+Ta 0.15/0.40
N 0.05
ANC 8-19 are specialised high alloy nickel and cobalt base castings- BS 3147 Part 3: 1976 are also very high alloy castings including
Ni and Co base casting-for details see British Investment Casters Technical Association
%
Trang 24Steel castings 26-13
Treatment
Tensile strength
7 Grade B hardness 293 HB min
8 Properties minima unless stated
9 N-Normalised, T-tempered, H&T-hardened & tempered, C-As cast
2 When specifically requested
3 For information only
4 Properties minima unless stated
Trang 252 6 7 4 Casting alIoys and foundry data
26.9 Cast irons
Data Source BCIRA
26.9.1 Classification of cast irons
Cast irons may be divided into two main groups, comprising the general purpose grades which are used for the majority of engineering applications and the special purpose or alloy cast irons which are used where the operating conditions involve extremes of heat, corrosion or abrasion
26.9.2 General purpose cast irons
These materials may be further classified into four groups, depending on the graphite form British Standards specifications exist for each of these materials New metric specifications incorporating SI units are available for malleable, grey and nodular irons The grade number denotes the tensile strength and the %elongation, e.g BS 2789 Grade 400/18 has a minimum tensile strength
of 400 MPa and a minimum elongation of 18% In the case of grey irons, which all fail with an
elongation less than 1 %, the grade number denotes tensile strength only in test specimens of standad dimensions
GREY IRONS
The grade number denotes the minimum tensile strength requirement on a test piece machined
from a 30 mm (1.2 in) diameter as-cast bar and this, rather than analysis, is the basis for
specification of cast irons for engineering purposes
For unalloyed irons the main constituents influencing tensile strength are carbon, silicon and phosphorus Their combined effect may be expressed as a carbon equivalent value (CEV), where
Classi$ication of general purpose cast irons
CEV= total carbon % t phosphorus % +silicon yo
3 Typical analysis and CEVs are given in Table 26.47
Table 26.42 TYPICAL ANALYSES OF GREY IRONS
Total carbon :; 3.1-3.4 3.2-3.5 3.2-3.4 3.0-3.2 2.9-3.1 3.1 rnax 2.9 max Silicon 7; (final) 2.5-2.8 2.2-2.5 2.0-2.5 1.6-1.9 1.5-1.8 1.4-1.6 1.4-1.6 Manganese 0 0.5-0.7 0.5-0.8 0.6-0.8 0.6-0.8 0.5-0.7 0.64.75 0.6-0.75 Phosphorus "/b 0.9-1.2 0.6-0.9 0.1-0.5 0.3 max 0.2 max 0.15 max 0.15 rnax Sulphur 7; (rnax.) 0.15 0.15 0.15 0.15 0.12 0.12 0.12
Trang 26Figure 26.2 Variation of tensile strength with section thickness
Table 26.43 SPECIFIED PROPERTIES OF GREY IRONS
Grade Cross-sectional
casting of as-cast Gauge
mm mm (tonf (tonf (tonf (tonf (tonf (tonf (tonf (in) (in) in-2) i n T 2 ) in-') in-2) in-2) in-2) in-2)
170 (11.0)
162 (10.5)
154 (10.0)
147 (9.5)
139 (9.0)
20 1 (13.0)
193 (12.5)
185
178 (11.5)
170 (12.0)
(11.0)
247 (16.0)
232 (15.0)
216 (14.0)
209 (13.5)
20 1 (1 3.0)
294 (19.0)
278 (18.0)
262 (17.0)
247 (16.0)
232 (15.0)
340 (22.0)
324 (21.0)
309 (20.0)
294 (19.0)
278 (18.0)
386 (25.0)
371 (24.0)
355 (23.0)
340 (22.0)
324 (21.0)
432 (28.0)
417 (27.0)
402 (26.0)
386 (25.0)
371 (24.0) Excessive rates of cooling lead to the formation of free carbides, or chilling This effect is more
severe with the higher strength irons, and occurs first at free edges of castings, wheye the cooling
rate is a maximum, as shown in Table 26.49
Table 26.44 CHILLING TENDENCY IN DIFFERENT GRADES OF IRON
Apprsoximate minimum chill free edge
Trang 2726-76 Casting alloys and data
Inoculation of high duty grey irons, from Grade 260 to 400, is carried out using a technique in which a small amount of inoculant, usually containing silicon, is added to the metal immediately before pouring so as to increase the silicon content by 0.3-0.5% Some commonly used inoculants include ferrosilicon, calcium silicide, SMZ (silicon-manganese-zirconium) Graphite is also a
powerful inoculant Several other proprietary inoculants, most of which are based on one or more
of these substances, are also effective The efficiency of a graphite inoculant depends on high purity, but that of other types depends on the presence of minor constituents such as aluminium, calcium, barium, strontium and cerium
The tensile strength of hypo-eutectic grey irons (Le CEV less than 4.3) can be significantly increased by inoculation, particularly with silicon-containing inoculants When the CEV is in the range 3.9-4.1 maximum strength is obtained when the inoculant adds 0 2 4 3 % silicon, cor-
responding to an increase of approximately 15 MPa (1 tonf in-’) compared with uninoculated
material With CEV below 3.9 the addition of inoculant sufficient to give a 0.5% increase in silicon content can add up to 60 MPa (4 tonf in-’) to the tensile strength, the effect being progressive with increasing additions up to at least this level
The chilling tendency of grey irons is also reduced by inoculation, enabling significantly thinner chill free sections than those in Table 26.50 to be cast The effect is progressive up to at least 0.40/,
The chill reducing effect forms the basis for most control tests for inoculation A sand cast
wedge or a small block cast in sand with one face against a metal plate may be made from the metal before and after inoculation The test pieces are then fractured and the change in depth of chill measured as an assessment of the success of the treatment Typical results are illustrated in Figure 26.3
Trang 28Cast irons 26-77
In castings which are susceptible to shrinkage defects inoculation will accentuate these problems, and its use should be restricted only to those castings where chilling or strength considerations make it necessary
Charge materials for production of grey irons include pig irons, cast iron scrap, steel scrap and ferro alloys
The main purposes served by pig irons is the provision of carbon, silicon, manganese and, where required, phosphorus and alloying elements They also limit the sulphur content of cupola melted iron
Blast furnace pig irons are available in a variety of grades which differ mainly in phosphorus content Each grade is generally available within different ranges of silicon and manganese contents
The carbon content will generally be at the lower end of the above ranges when the silicor, content is at the upper end of the corresponding range The silicon content can be specified in
increments of 0.25 or 0.50% within the ranges given
Refined alloy and special pig irons are produced to the customer's specific requirements in a wide range of compositions They may contain alloying elements if required, within specified ranges of alloy content
Silvery pig iron (l(r12% silicon, 12-14% silicon) provides silicon in a more dilute form than ferrosilicon It is used to minimise variation in silicon content of cupola melted iron when a substantial quantity of silicon is added, and to reduce the risk of aluminium contamination of the metal which may arise if large additions of ferrosilicon are made
Special irons, generally of high carbon content, but with a very low content of residual elements are also available, their main use being for the production of nodular graphite iron
Return scrap is the best source of scrap for re-melting providing this is of known and consistent composition and this should be fully utilised
Purchased scrap is available in several fairly readily identifiable types as given in Table 26.51
In comparison with pig iron and cast iron scrap, steel scrap is low in carbon and silicon
contents, and the phosphorus and sulphur contents are generally below 0.05% It is used to lower carbon and silicon contents, particularly in the production of higher strength irons
Ferro-alloys are used to remedy deficiencies of certain elements, particularly silicon and manganese in the charges
Table 26.46 COMPOSITION OF SCRAP
FERROSILICON
The two most common grades, in lump form, contain 75-80% and 45-50:' of silicon
Ferromanganese in lump form contains 75-80>; manganese
BRIQUETTES
For relatively small additions of silicon, manganese and chromium, briquettes may be used for convenience and consistency They contain a fixed amount of the alloy and avoid the necessity of weighing the addition
Trang 292G78 Casting alloys and foundry data
Table 26.41 LOSSES OF ALLOYING ELEMENTS
Melted in cupola Added to ladle
l0-15% of amount charged
5% of amount added
5-10% of amount added
15% of amount added 10% of amount added
~~
Table 26.48 SUMMARY OF STRUCTURAL EFFECTS OF ALLOYING ELEMENTS O N CAST IRON
Effect on carbides
- 0.3-1.25
0.3-1.0 0.1-0.2 0.5-2.0
Mildly increases About neutral Mildly restrains Strongly restrains Strongly restrains Strongly restrains Restrainst
Restrainst
Restrainst
Strongly Mildly stabilizes refines Strongly Refines stabilizes
Stabilizes Mildly
refines
About Strongly neutral refines About About neutral neutral About About neutral neutral Decreases Coarsens stability
Decreases Coarsens stability
Decreases Coarsens stability
Mildly Mildly decreases refines stability
Decreases Strongly stability refines:
neutral
Eflect on
combined carbon
in pearlite
Increases Increases
- Increases
Mildly increases Increases Mildly decreases Strongly decreases Strongly decreases Strongly decreases Mildly decreases and
Effect
on
matrix
Refines pearlite and hardens
Refines pearlite and hardens Refines pearlite {and strengthens Hardens
Produces ferrite and softens Produces ferrite and softens Produces ferrite and softens Refines pearlite and hardens stabilizes at
eutectoid Decreases Produces
ferrite and softens ferrite and softens
* Chill inducing effect of 1 part.of chromium about balances chill restraining effect of I$ parts silicon or 2* parts nickel
t Chill restraining elfect of nickel about half that of silicon
Strong refining action of titanium takes place when small amounts are added, particularly when oxygen is also present
Trang 30Cas1 26-79 Melting range varies widely with composition, the melting temperature falling with increase of carbon content so that low carbon irons must be cast at considerably higher temperatures than high carbon irons With grey irons containing high phosphorus, melting of the steadite (phosphide eutectic) begins at about 960°C, giving a relatively long melting range
FLUIDITY OF CAST IRON
The fluidity of cast iron depends primarily upon composition and pouring temperature The fluidity, as measured by a special test spiral casting, may be improved by increasing the carbon, silicon or phosphorus contents, or by increasing the pouring temperature Of these variables, carbon content is the most effective from the point of view of composition, but an increase of 1520°C in the pouring temperature improves the fluidity as much as an increase of 0.10% carbon, 0.3076 silicon or 0.20% phosphorus
Table a650 DENSITIES AND LIQUIDIS TEMPERATURES OF SOME TYPICAL GREY CAST
IRONS (BASED ON 3.8 cm (liin) SECTION)
Table 26.51 HARDNESS AND DENSITY OF MICROCONSTITUENTS OF CAST IRON
Iron carbide Fe3C or (FeCr),C
Iron carbide (CrFe),C,
Depending on interlamellar distance
Trang 312680 Casting alloys and foundry data
Heat treatment of grey cast irons may be carried out to eliminate residual stresses, improve machinability or to increase wear resistance
Stress relief heat treatment is carried out by slow heating at 50-100°C per hour to 60O"C+1O0C, holding at 600°C for one hour plus an additional half hour per cm (0.4 in) of maximum section thickness, and cooling at 50-100°C per hour to below 200°C followed by air cooling
Annealing heat treatment is applied when improved machinability is required There are two distinct sets of conditions in which annealing may be carried out
1 To break down free carbide or chill formed as a result of failure to match carbon equivalent value to minimum free edge thickness Annealing must then be carried out at 900°C for 1-5 h
to ensure complete breakdown of carbide, followed by air cooling to ensure a pearlitic matrix This treatment is carried out as an emergency measure to salvage otherwise unmachinable castings
2 To provide castings which can be machined at a very high rate Castings which are fully pearlitic can be annealed to give a mainly ferritic matrix with a hardness of 140-180 HB by holding at 780-820°C for 1-2 h followed by slow cooling
Hardening by quenching and tempering is carried out where high surface hardness is required, with corresponding improvement in wear resistance Hardening temperatures in the range 850- 880°C are used, followed by oil quenching and tempering at 300°C to reduce internal stresses Tensile strength is not increased to the same extent as hardness (Figure 26.4) and because of the risk of cracking during quenching, this process is usually restricted to small castings of simple shape
Figure 26.4 Effect of heat treatment on the strength and hardness of alloy cast iron
Surface hardening, by flame or induction heating, is widely used to improve the wear resistance
of critical surfaces on large castings such as slideways on machine tools For good response to this treatment the as-cast structure must be fully pearlitic, and the phosphorus content must be below
0.2% to avoid pitting Hardness in the range 450-500HV are obtained with depths of 1-3mm (0.040-0.125 in)
MALLEABLE IRONS
Malleable irons are brittle as cast, their structure consisting of iron carbide in a pearlitic matrix
By suitable heat treatment the carbides are broken down resulting in a structure that consists of graphite aggregates (temper carbon) in a matrix which may be ferritic or pearlitic, depending on composition and heat treatment conditions
The British Standards (BS 309, 310 and 3333) specify neither composition (apart from
maximum phosphorus content of 0.12%) nor heat treatment
Trang 32Cast irons 2 6 8 1 Table 2653 MECHANICAL PROPERTIES OF WHITEHEART MALLEABLE IRON
Diameter of Tensile 0.2 Proof Elongation Hardness Grade test bar d strength min stress min min A typical max
* Although all grades of whiteheart malleable are weldable with correct procedure, W38-12 should he selected where strength and
t Test bar diameter should be representative of the important sectional thickness of the casting
Ref British Cast Iron Research Association
avoidance of post weld heat treatment is required
In practice, whiteheart malleable irons have an initial total carbon content of about 3.5 % which is reduced to the range 0.25-2.0% by heat treating the castings at 900°C in an oxidizing environment,
and slowly cooling The required conditions may be produced by packing the castings in an oxidizer (e.g hematite ore) or by use of a controlled atmosphere furnace This results in a carbon gradient within the castings, the outer layer being normally ferritic and graphite-free while the core structure consists of temper carbon aggregates in a pearlitic matrix Small castings of thin section may have a fully decarburized structure throughout, and this is sometimes referred to as a weldable grade of malleable iron
Blackheart and pearlitic malleable irons have a lower initial total carbon content in the range 2-
3 % Heat treatment in a neutral atmosphere a t 85G875"C followed by slow cooling results in a
uniform structure of temper carbon in a ferritic matrix
Malleable irons Pearlitic have a structure consisting of temper carbon in a pearlitic matrix This is produced either by fapid cooling after annealing or by the addition of 0.5 % or more manganese Pearlitic malleable irons have a good response to surface hardening by flame or induction heating, and hardness values of HV 500 can be consistently achieved in production
NODULAR IRONS
In noduIar (spheroidal graphte) irons free graphite is present as spheres or nodules in the as-cast condition Graphite in this form has a much smaller weakening effect on the matrix than the dispersed graphite flakes in grey ions Nodular irons therefore have considerably higher strength, ductility, and impact values than grey irons
Cerium and magnesium additions both produce nodular structures, but the latter has been found to be more adaptable and economical Both elements are desulphurizers and nodule formation is not possible until the sulphur content has been lowered to about 0.02% Very small amounts of trace elements, such as 0.003% bismuth, 0.004% antimony, 0.009% lead and 0.12%
titanium prevent nodule formation The effect of these elements is additive, but it can be
neutralized by the addition of sufficient cerium to give a residual content of O.OOS-O.Ol%
Magnesium may be added directly to the ladle as nickel-magnesium, nickel-silicon-magnesium
or iron-silicon-magnesium alloy Higher magnesium recovery is obtained using a plunging
technique in which lower density, higher magnesium content additions such as magnesium impregnated coke are held below the liquid metal surface by means of a plunging head Maximum recovery results from the addition of pure magnesium to the molten iron in a closed pressure-tight
converter vessel Because of equipment costs the use of this latter method is normally restricted to
large-scale production
Trang 3326-82 Casting alloys and foundry data
In all cases the amount of magnesium to be added is given by:
_ _ 2 (initial sulphur content) + residual magnesium content (usually 0.03-0.05%)
_ _
expected magnesium recovery Nodular irons are inoculated with 0.4-0.8% silicon after nodulizing to refine the structure and minimize chilling
The carbon content of nodular irons is usually kept above 3.5% in the interests of good castability Silicon, manganese and phosphorus should be below 2.3%, 0.4% and 0.06% re-
spectively to give maximum ductility and impact value in the ferritic condition
Nodular irons are slightly more prone to shrinkage defects than grey irons
Adequate feed metal should be provided and moulds of high rigidity are to be preferred Running systems should be designed to minimize turbulence, so as to prevent the entrapment of dross which tends to be formed as a result of the magnesium content
Although nodular irons are much less section sensitive than grey irons, depending on the trace amounts of carbide stablizing elements present, their matrix structures may range from fully
pearlitic to completely ferritic, and chilling may occur in sections thinner than 5 mm (0.2 in)
By close control of analysis and inoculation practice nodular irons can be produced in the as- cast condition over a wide range of section thicknesses with any required matrix structure from fully ferritic to fully pearlitic
Alternatively, the matrix structure of nodular iron castings can be modified by appropriate heat treatments, since the presence of free carbon in the form of graphite enables diffusion of carbon to
or from the graphite particles to take place This is not possible with steels, which contain no free graphite The effect of variation in matrix structure on mechanical properties is much more pronounced with nodular iron than with flake graphite cast iron, and by heat treatment of an iron
of fixed composition foundries can produce castings conforming to the complete range of the
grades of BS 2789: 1985
Practical heat treatments include:
Annealing Heat to 850-900°C where the matrix becomes completely austenitic and slow furnace cool at 20-35°C per hour to below 700°C Alternatively, cool more rapidly to 700-720"C and hold for
4-12 h, followed by air cooling Ferritic iron produced in this way confirm to BS 2789: 1985 grades
350122 to 420112
Normalizing This is carried out by air cooling from 850 to 900"C, and produces a mainly pearlitic matric conforming to grades 700/2 and 80012 in castings of light and medium section The use of alloying elements is often necessary to produce a pearlitic matrix in heavier section castings
Hardened and tempered structures These are produced by oil quenching from 850 to 900°C and tempering at 5 5 M W C Material conforming to BS 2789 Grade 800/2 and 900/2 is sometimes inveriably produced by this method
Austempering is carried out by heating castings to 850-950"C, followed by quenching to an isothermal treatment temperature within the range 230400°C and holding this temperature typically
for 1-2 hours A variety of bainitic structures can be obtained, resulting in combinations of strength,
ductility and toughness which cannot be achieved in ductile irons by other means These austempered ductile irons (ADI) are used for many different engineering applications such as gears, crankshafts, vehicle suspension components and parts of earthmoving equipment Provisional specifications for
Table 2654 MECHANICAL PROPERTIES OF BLACKHEART MALLEABLE IRON
Diameter of Tensile strength 0.2% Proof Elongation Hardness Grade test bar d min R , stress Rp0.2 min min typical
Trang 34Cas0 irons 26-83
Tqble 2655 MECHANICAL PROPERTIES OF PEARLITIC MALLEABLE IRON
Diameter of Tensile strength 0.2 % Proof Elongation Hardness Grade test bar d min R, stress Rp0.2 min min typical
* I f air quenched and subsequently tempered min 0.2% proof stress 530 MPa min
Ref British Cast Iron Research Association
various countries to cover ADIs are summarised in Table 26.57 The various grades can be typically produced from the same ductile iron by adjustment of the austempering time and temperature AD1 exhibits section size sensitivity and test bars are not representative of heavy sections At
- 40°C high toughness grades may show a drop of 15 % in yield strength as well as a drop in tensile strength compared with room temperature values No changes have been found in elevated temperature properties up to 300°C Also of concern is the low temperature toughness and the
ductile-brittle transformation temperature although notched specimen results indicate gradual toughness transition as temperature decreases
Mixed matrix structures Structures intermediate between the annealed and normalized grades have
a range of mechanical properties depending on the ratio of ferrite t o pearlite The corresponding grades of BS 2789 are 400/10, 500/7 and 600/3 In practice these structures are produced by austenitizing at 850-900°C followed by either controlled rapid cooling at lapproximately 100T per hour through the critical temperature range of 720-8OO"C or by rapid air cooling from an appropriate intermediate temperature, e.g 730"C, within the critical range
26.9.3 Compacted graphite irons
Although the existence of compacted graphite containing irons has been known for many years, it is
only relatively recently that they have been commercially exploited Such irons are characterised by the graphite being present in the form of relatively short, thick flakes with rounded extremities and undulating surfaces
In general compacted graphite irons have mechanical and physical properties intermediate between those of conventional flake graphite irons (grey irons) and nodular graphite irons The outstanding characteristics are good thermal conductivity combined with useful ductility and higher tensile and fatigue strengths than for grey irons
At present no British Standard exists for these materials
The presence of certain element combinations in irons which would otherwise solidify with a conventional flake graphite form may promote the formation of the compacted type of graphite At present the production of compacted graphite irons is largely based on additions of magnesium and/or cerium to irons of low sulphur content The magnesium based treatments are similar to those employed for nodular graphite iron production while the cerium methods are usually simple ladle addition processes
In the magnesium process, as the magnesium content is increased, the graphite structure changes
from conventional flake, through compacted flake to fully nodular The range of magnesium contents
to facilitate compacted flake structures is very narrow and it is usually necessary to employ additions
of titanium and cerium to extend the range and provide a practical ladle based process Magnesium and titanium are usually present in the ranges 0.015-0.035 per cent and 0.08-0.15 per cent respectively with a trace of cerium
Trang 35MECHANICAL PROPERTIES OF NODULAR IRONS
Verification of hardness and 0.2% proof stress is optimal
Individual value Value in brackets is mean of 3 tests
t F=ferrite, F/P=brrite/pearlite, P/F=pearlite/ferrite, P=pearlite, TS=tempered structure, TH = tempered martensite
- 14(17) ll(14)
FIP
p/F
P For TS
TM
Trang 36Tensile strength Yield strength Elongation Impact
35.6 45.3 55.0 71.2 84.2 32.4 45.3 61.5 77.7
-
43.4 50.5 60.9 47.3 51.8 64.7
4401442
3451335
* Elongation and impact not specified Grades 1400/1100/1 and 1600/1300/- mainly used for gear and wear resistant applications
Table 26.58 A COMPARISON OF THE MECHANICAL PROPERTIES OF FLAKE, COMPACTED AND NODULAR GRAPHITE CAST IKONS IN 30 mm BAR SECTIONS
Flake Compacted graphite iron* Nodular
* Irons produced by magnesium-titanium-cerium treatment
Fully compacted graphite irons have combinations of properties intermediate between those of conventional flake and nodular irons, as shown in Table 26.58 They behave elastically over a range
of stresses although their limit of proportionality is lower than nodular irons The tensile properties of compacted graphite irons are less sensitive to variations in carbon equivalent than conventional flake
irons (Fig 26.5) but they are section sensitive (Fig 26.6)
Compacted graphite irons have intermediate thermal conductivity values between flake and
nodular iron and comparative figures are given in Table 26.59
The combination of relatively high strength and good thermal conductivity has resulted in compacted graphite irons primarily finding application where containment of stress at high temperature or under thermal cycling conditions are important Applications for ingot moulds, cyhnder heads, brakedrums and discs and manifold castings are typical
Trang 3726-86 Casting alloys and foundry data
Figure 265 Effect of carbon equiualent on the tensile strengths of Jake,
compacted and nodular graphite irons cast into 30mmdiameter bars
Figure 26.6 Variation of tensile strength with cast-section size for ferritic and
pearlitic compacted graphite irons of various carbon equivalents Each curve is
the centre of a band of variation in strength of about f 3 0 MPa ( f 2 tonf/in2)
Table56.59 A COMPARISON OF THE THERMAL CONDUCTIVITIES OF FLAKE, COMPACTED AND
NODULAR GRAPHITE CAST IRONS
Thermal conductivity W/m K
Flake graphite iron
Compacted graphite iron
Nodular graphite iron
Trang 38Table 26.60 AUSTENITIC CAST IRONS
Composition %
Proof strength
0.511.5 0.511.5 0.511.5 0.5jl.5
1.0 max
0.511.5 0.511.5 1.512.5 4.014.5 0.511.5 6.017.0
13.5117.5 18.0/22.0 18.0122.0 18.0/22.0 34.0136.0 28/32 18/22 21/24 21/24 28/32 12/14
1.012.5 1.512.5 1.512.5 1.512.5 1.512.5 2.513.5 2.513.5 0.5 max
0.5 max
2.513.5 0.2 max
0.2 Cu 5.517.5 0.2 Cu 0.5 max
Cu 0.5 max 0.08
0.05 Cu 0.5 max 0.08 max -
0.2 Cu 0.5 max
Cu 0.5 max 0.08
0.08 Cu 0.5 max 0.08 Cu 0.5 max 0.08 Cu 0.5 max
* (FG)=Flake graphite, (SG)=speroidal graphite
** Value in bracket is Charpy V notch strength at 20°C in J
-
-
13.6 13.6 13.6
-
13.6 11.0 13.0 13.6 13.0
Elongation A**
Trang 390.3/0.8 0.3/0.8 1.512.2 1.512.2 1.512.2
1.0 max 1.0 max 1.0 max 1.0 max 1.0 max 1.0 max
1 .O max
0.2/0.8 0.2/0.8 0.210.8
0.210.8 0.210.8 0.210.8 0.210.8 0.210.8
0.511.5 0.511.5 0.511.5 0.5/1.5 0.511.5 0.511.5 0.511.5
~
-
-
3.015.5 3.015.5 4.016.0 4.016.0 4.016.0
2.0 max 2.0 max 2.0 max 2.0 max 2.0 max 2.0 max 2.0 max
2.0 max 2.0 max 2.0 max
1.513.5 1.513.5 S.O/lO.O
S.O/lO.O
8.011 0.0
14/17 14/17 17/22 22/28 11/13 11/13 22/28
0.15 0.5 0.15
0.15 0.15 0.10 0.10 0.10
0.10
0.10
0.10 0.10 0.10 0.10 0.10
Trang 40Cast 2 6 8 9
P e a j l l t i c M a r t e k i t i c High ch!omium F e r r l t i c
white irons whi@e irons irons 117% t o
6Ni-hard typel 33%chromiuml
W e a r Wear Wear,corrosion
resisting resisting &heat resisting
Table 26.62 CORROSION RESISTING HIGH SILICON CAST IRONS
m a t r i x A u s t e n i t i c m a t r i x A c i c u l a r m a t r i x
I
H i g h strength Wear resisting
n 4.0/5.0 Cathodic protection anodes
- Corrosion resistance at expense of strongth -~
Heat treatment: Castings to be stripped from moulds while hot and as soon as possible after solidification, the hot castings to he
charged to a furnace preheated t o approximately 600°C and kept at this during charging Then heat to not less than 750°C and not
more than 850°C Soak for 2 hours for castings of simple form and thickners less than 18 mm and for 9 hours for heavy castings Cool
slowly after soak to 300°C before unloading
5 % ~ i 1 i i o n i r o n H i g h silicon iron
I S i l a l ) I I S % silicon1 Heat resisting Corrosion resisting
Figure 26.7 Classijcation of special purpose cast irons
British Standards are summarised for Austenitic irons BS 3468: 1986 Table 26.60, for alloy cast irons BS 4844: 1986 in Table 26.61 and for corrosion resisting high silicon irons BS 1591: 1975 in