Aluminium Casting Alloy LM31
This alloy conforms to BS 1490:1988 LM31. Castings are standardised in the as cast (M) condition and in the precipitation treated (TE) condition.
Chemical Composition
| % | % | % | |||
|---|---|---|---|---|---|
| Copper | 0.1 max | Magnesium | 0.5-0.75 | Silicon | 0.25 max |
| Iron | 0.5 max | Manganese | 0.1 max | Nickel | 0.1 max |
| Zinc | 4.8-5.7 | Lead | 0.05 max | Tin | 0.05 max |
| Titanium | 0.25 | Chromium | 0.4-0.6 | Aluminium | Remainder |
| Others total | 0.05 max | Others total | 0.15 max |
Mechanical Properties
Castings in the as cast (M) condition must be naturally aged for 3 weeks to determine the mechanical properties.
|
|
M Sand Cast |
TE Sand Cast |
|
0.2% Proof Stress (N/mm2) |
170 |
- |
|
Tensile Strength (N/mm2) |
215 |
215 |
|
Elongation (%) |
4 |
4 |
|
Impact resistance Charpy (Nm) |
2.7-4.0 |
- |
|
Brinell Hardness |
70 |
- |
|
Modulus of Elasticity (x103 N/mm2) |
71 |
- |
|
Shear Strength (N/mm2) |
180 |
- |
Strength at elevated temperatures
In comparison with the other Aluminium casting alloys, the strength of LM31 at elevated temperatures is good.
Physical Properties
|
|
|
|
Coefficient of Thermal Expansion (per °C @ 20-100°C) |
0.000025 |
|
Thermal conductivity (cal/cm2/cm/°C @ 25°C) |
0.35 |
|
Electrical conductivity (% copper standard @ 20°C) |
35 |
|
Density (g/cm3) |
2.81 |
|
Freezing range (°C) approx. |
615-570 |
Machinability
LM31 has good machinability characteristics.
Corrosion Resistance
This alloy has very good corrosion resistance.
Anodising
This alloy is suitable for clear or colour (decorative) anodising.
Heat Treatment
Good Strength and toughness can be produced by natural or artificial ageing after casting. Castings in the as cast (M) condition must be naturally aged for 3 weeks before testing to determine the mechanical properties.
The TE heat treatment condition provides artificial ageing. Using this alloy avoids the risks of distortion and cracking on quenching after solution heat treatment.
Applications and General Notes
LM31 has very good shock resistance and is suitable for shock resisting components. It is used for general engineering castings, particularly large sand casting.
Notes for Designers of Non-Ferrous Castings
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