Technical Data - Alloys and Composition

Alloy Compositions +
Chemical Composition LM2 LM6 LM20 LM24 Pyral
Copper
0.7 - 2.5
0.1 Max
0.4 Max
3.0 - 4.0
0.2 Max
Magnesium
0.3 Max
0.1 Max
0.2 Max
0.3 Max
0.1 Max
Silicon
9.0 - 11.5
10.0 - 13.0
10.0 - 13.0
7.5 - 9.5
0.5 Max
Iron
1.0 Max
0.6 Max
1.0 Max
1.2 Max
0.5 - 0.8
Manganese
0.5 Max
0.5 Max
0.5 Max
0.5 Max
2.25 - 2.75
Nickel
0.5 Max
0.1 Max
0.1 Max
0.5 Max
2.25 - 2.75
Zinc
2.0 Max
0.1 Max
0.2 Max
3.0 Max
0.1 Max
Lead
0.3 Max
0.1 Max
0.1 Max
0.3 Max
0.1 Max
Tin
0.2 Max
0.05 Max
0.1 Max
0.2 Max
0.05 Max
Titanium
0.2 Max
0.2 Max
0.2 Max
0.2 Max
0.1 - 0.2
Aluminium Remainder Remainder Remainder Remainder Remainder

Alloy Equivalents +

Standard LM2 LM6 LM20 LM24
ISO
AlSi10Cu2Fe
AlSi12
AlSi12Fe
AlSi12Cu
AlSi12CuFe
AlSi12Cu3Fe
EN 1706 AC
46100
44100
47000
46500
France
A-S9U3-Y4
AS 13
A-S12-Y4
A-S9U3A-Y4
Germany
G-AlSi12
DIN 230
G-AlSi12(Cu)
DIN 231
G-AlSi8Cu3
DIN 226
Italy
UNI 5076
UNI 4514
UNI 5079
UNI 5075
UNI 3601
USA AA/ASTM
A 384
A 413
A 413
A 380
USA SAE
383
305
306
Japan
ADC 12
AC 3A
AC 4strong
ADC 10
RSA
SA 46
SA 22
SA 24
SA 44
Australia
BB401 CC401
EA401
DA401
CA313
BA323 AA325

LM2 +

LM2

Aluminium Casting Alloy (AL - Si10Cu2Fe)
Colour Code - Red / White

 

Machinability

This alloy is a little difficult to machine since the high silicon content causes rapid tool wear. It is, however, far easier than the LM6 and LM20 alloys as the tendency to drag is practically eliminated by the presence of copper and other elements.

Carbide-tipped tools are advocated but high speed steel tools give good results. A cutting lubricant and coolant should be employed.

Corrosion Resistance

Resistance to corrosion by ordinary atmospheric conditions is good and by marine atmosphere fairly good. it is inferior in this respect to LM6 but can be improved by anodic treatment.

Anodising

LM2 can be anodically treated to give a protective surface of a darkish grey colour The surfaces of die-castings. however, are not generally suitable for decorative anodising.

Casting Characteristics

FLUIDITY- Can be cast into thin and intricate sections with ease. PRESSURE TIGHTNESS - Suitable for leak-tight castings. HOT-TEARING - Castings exhibit virtual freedom from hot-tearing. TYPICAL POURING TEMPERATURE - Pouring temperatures for diecastings depend very largely on the particular casting and the machine and vary too widely for a typical temperature to provide useful guidance. The melt should not, however, be allowed to stand at temperatures only little above the freezing range or the bottom of the melt may become enriched in such elements as iron and manganese.

Heat Treatment

Castings in this alloy are not heat-treated.

Applications and General Notes

Essentially a diecasting alloy, LM2 is not normally used for other types of casting. As a general purpose alloy its applications are extremely varied and widespread and it may be used for almost any component which can be diecast, unless the service conditions demand a higher resistance to corrosion or slightly greater ductility, in which case LM6 or LM20 maybe preferred.

For the vast majority of diecastings, the alloys LM2 and LM24 are equally suitable.

LM6 +

LM6

Aluminium Casting Alloy (AL - Si12)
Colour Code - Yellow

Machinability

Alloys of this and similar compositions are rather difficult to machine. This is due firstly to their tendency to drag and secondly to the rapid tool wear caused by the high silicon content. Carbide-tipped tools with large rake angles and relatively low cutting speeds give comparatively good results. A cutting lubricant and coolant should be employed.

Corrosion Resistance

LM6 exhibits excellent resistance to corrosion under both ordinary atmospheric and marine conditions. For the severest conditions this property can be further enhanced by anodic treatment.

Anodising

LM6 can be anodised by any of the common processes. The resulting protective film ranging in colour from grey to dark brown.

Casting Characteristics

FLUIDITY - Can be cast into thinner and more intricate sections than any of the other types of casting alloys. PRESSURE TIGHTNESS - Especially suitable for teak-tight castings. HOT-TEARING - Castings in sand or chill moulds exhibit complete freedom from hot-tearing. TYPICAL POURING TEMPERATURE - A typical temperature for sand and chill castings is 725 ºC but in practice it may range considerably above or below this value according to the dimensions of the casting.

Pouring temperatures for diecastings depend very largely on the particular casting and the machine and vary too widely for a typical temperature to provide useful guidance~ The melt should not, however, be allowed to stand at temperatures only a little above the freezing range or the bottom of the melt may become enriched in such elements as iron and manganese

PATTERNMAKERS' SHRINKAGE - 1.3% or 1/75 NB For diecastings the shrinkage may be expected to be considerably less. NOTES -for sand castings and medium and heavy section chill castings the alloy must be modified before pouring (by treatment with sodium or sodium salts ~ see booklet 'Melting Practice for the Production of Aluminium Alloy castings'), if the maximum mechanical properties are to be realised. An alternative modifying process is the treatment of the melt with strontium as an aluminium-silicon-strontium hardener- A more persistent state of modification is achieved by this method.

Heat Treatment

Ductility can be improved slightly by heating at 250-300 ºC but apart from stress relieving, the heat-treatment of LM6 is of little industrial interest.

Applications and General Notes

Suitable for marine 'on deck' castings. water-cooled manifolds and jackets, motor-car and road transport fittings; thin sections and intricate castings such as motor housings, meter cases and switch-boxes; for very large castings, e.g., cast doors and panels where ease of casting is essential; for chemical and dye industry castings, e.g. pump parts: for paint industry and-food and domestic castings. In general use where marine atmospheres or service conditions make corrosion resistance a matter of major importance. Especially suitable for castings that are to be welded. The ductility of LM6 alloy enables castings easily to be rectified or even modified in shape, e.g., simple components maybe cast straight and later bent to the required contour-Equally adaptable for sand and permanent mould castings and for diecastings

The aluminium-silicon alloys possess exceptional casting characteristics, which enable them to be used to produce intricate castings of thick and thin sections. Fluidity and freedom from hot-tearing increase with silicon content and are excellent throughout the range Their resistance to corrosion is very good, but special care is required in machining. In general, the binary alloys are not heat-treated: at elevated temperatures their strength falls rapidly. Although of medium strength their hardness and elastic limit are low but they possess excellent ductility.

LM20 +

LM20

Aluminium Casting Alloy (AL - Si12Cu)
Colour Code - Yellow/Green

Machinability

Castings made in LM20 are rather difficult to machine. This is due to their tendency to drag and rapid tool wear caused by the high silicon content. The higher copper content does reduce the problem of drag compared to LM6. Carbide-tipped tools with large rake angles and relatively low cutting speeds give comparatively good results. A cutting lubricant and coolant should be employed.

Corrosion Resistance

LM20 exhibits high resistance to corrosion under both ordinary atmospheric and marine conditions. For the severest conditions this property can be further enhanced by anodic treatment. LM20 is only marginally worse than LM6 with respect to corrosion resistance.

Anodising

LM20 can be anodised by any of the common processes. The resulting protective film ranging in colour from grey to dark brown. The surfaces of diecastings are generally not suitable for decorative anodising.

Casting Characteristics

FLUIDITY - Can be cast into thinner and more intricate sections than many other types of casting alloys. PRESSURE TIGHTNESS - Especially suitable for teak-tight castings. HOT-TEARING - Castings tend to exhibit complete freedom from hot-tearing. TYPICAL POURING TEMPERATURE - Pouring temperatures for diecastings depend very largely on the particular casting and the machine and vary too widely for a typical temperature to provide useful guidance. The melt should not, however, be allowed to stand at temperatures only a little above the freezing range or the bottom of the melt may become enriched in such elements as iron and manganese

PATTERNMAKERS' SHRINKAGE - 1.3% or 1/75.

NOTES -for sand castings and medium and heavy section chill castings the alloy must be modified before pouring (by treatment with sodium or sodium salts ~ see booklet 'Melting Practice for the Production of Aluminium Alloy castings'), if the maximum mechanical properties are to be realised. An alternative modifying process is the treatment of the melt with strontium as an aluminium-silicon-strontium hardener- A more persistent state of modification is achieved by this method.

Heat Treatment

Castings in LM20 tend not to be heat treated.

Applications and General Notes

Suitable for marine 'on deck' castings. water-cooled manifolds and jackets, motor-car and road transport fittings; thin sections and intricate castings such as motor housings, meter cases and switch-boxes; for very large castings, e.g., cast doors and panels where ease of casting is essential; for chemical and dye industry castings, e.g. pump parts: for paint industry and-food and domestic castings. In general use where marine atmospheres or service conditions make corrosion resistance a matter of major importance. LM20 is generally only preferred to LM2 or LM24 when the castings are used in aggressive media, requiring the higher resistance LM20 offers. Where the very highest resistance is required, then LM6 may be found superior to LM20.

LM20 has slightly better castability than LM6.

LM24 +

LM24

Aluminium Casting Alloy (AL - Si8Cu3Fe)
Colour Code - Red / Blue

Machinability

Machining practice is similar to that for other Aluminium casting alloys containing silicon. whilst there is not the tendency to drag associated with high silicon alloys such as LM6, tool wear is more rapid than in the case of alloys containing relatively small amounts of silicon. The use of carbide-tipped tools is recommended but a good finish can be obtained with high speed steels. Lower alloy steel tools may be used provided they are frequently re-ground to maintain a sharp cutting edge. A cutting lubricant and coolant should be employed.

Corrosion Resistance

Resistance to attack under normal atmospheric conditions is similar to that of alloy LM4 - fairly good. In marine atmospheres, or under other severe conditions, castings in this alloy should be protected by painting.

Anodising

Anodising treatment by either the chromic or sulphuric acid process produces an anodic film of a grey colour. The surfaces of diecastings, however, are not generally suitable for decoratrve anodising.

Casting Characteristics

FLUIDITY - Although slightly less fluid than LM6 and LM2, the alloy is used successfully for castings of thin sections. PRESSURE TIGHTNESS- suitable for leak-tight castings. HOT-TEARING - Most castings may be produced in this alloy with complete absence of hot-tears. TYPICAL POURING TEMPERATURE - Pouring temperatures for diecastings depend very largely on the particular casting and the machine, and vary too widely for a typical temperature to provide useful guidance. The melt should not, however, be allowed to stand at temperatures only a little above the freezing range or the bottom of the melt may become enriched in such elements as iron and manganese.

Heat Treatment

Castings in this alloy are not heat-treated.

Applications and General Notes

LM24 is essentially a diecasting alloy. It has excellent casting characteristics and is generally a little simpler to diecast than the higher silicon-containing alloys. Die-castings in LM24 are suitable for most engineering applications and have an advantage over an alloy such as LM6 when maximum mechanical properties are required. In practice LM6 is preferred to LM24 only for diecastings in which a high resistance to corrosion is the primary requirement. An alloy of composition similar to LM24 is by far the most widely used diecasting alloy in the United States and a similar alloy has recently been adopted by the European Diecasting Committee.

For the vast majority of diecastings, the alloys LM2 and LM24 are equally suitable.

Zinc Alloys +
CEN Specification ZA2 ZA3 ZA5 ZA8
Alloy Symbol ZnAl4Cu3-P Zn Al4-P ZnAl4Cu1-P ZnAl8Cu1-P
Alloy Number ZP0430 ZP0400 ZP0410 ZP0810
CEN Short ZP2 ZP3 ZP5 ZP8
Designation Colour White/Green White/Yellow White/Black White/Blue
Chemical Composition ZA2 ZA3 ZA5 ZA8 ACuZinc
Aluminium 3.7 - 4.3 3.7 - 4.3 3.7 - 4.3 8.0 - 8.8 2.8 - 3.3
Copper 2.7 - 3.3 0.1 Max 0.7 - 1.2 0.8 - 1.3 5.0 - 6.0
Magnesium 0.025 - 0.06 0.025 - 0.06 0.025 - 0.06 0.015 - 0.03 0.025 - 0.05
Iron 0.05 Max 0.05 Max 0.05 Max 0.06 Max 0.075 Max
Silicon 0.03 Max 0.03 Max 0.03 Max 0.045 Max -
Nickel 0.02 Max 0.02 Max 0.02 Max 0.02 Max -
Lead 0.005  Max 0.005  Max 0.005  Max 0.006  Max 0.005  Max
Cadmium 0.005  Max 0.005  Max 0.005  Max 0.006  Max 0.004  Max
Tin 0.002  Max 0.002  Max 0.002  Max 0.003  Max 0.003  Max
Zinc Remainder Remainder Remainder Remainder Remainder
Physical Properties ZA2 ZA3 ZA5 ZA8 ACuZinc
Melting Range Deg' C 379 - 388 381 - 387 380 - 386 375 - 404 402 - 502
Density g/cm3 6.7 6.7 6.7 6.3 6.85
Coef Thermal expansion 27.4 27.4 27.4 23.3 24
Thermal Conductivity W/m C 105 113 109 115 106
Electrical Conductivity 25 27 26 27.7 26.9
Mechanical Properties ZA2 ZA3 ZA5 ZA8 ACuZinc
Tensile Strength 359 283 328 374 407
Yield Strength (0.2%) 270 221 228 290 338
Impact Strength 47 58 65 42 -
Elongation % 7 10 7 8 6
Shear Strength MPa 315 214 262 276 280
Brinell Hardness (500Kg) Up To 100 Up To 82 Up To 91 Up To 103 Up To 118
Fatigue 5x108 cycles MPa 58 48 56 103  
Young's Modulus MPa >85,500 >85,500 >85,500 >85,500  
Poisson's Ratio 0.27 0.27 0.27 0.29 - 0.30  
Shear Modulus MPa 34,000 34,000 34,000 34,000