Please Note:
UK Racing Castings makes no warranty whatsoever, as to the correctness of the information provided herein and accepts no risks or liability for any person(s) relying on the content.

LM25 ALUMINIUM CASTING ALLOY
(A1-Si7Mg0.5)
Colour Code - Yellow/Blue
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Alloy Data Page

Chemical Composition

Mechanical Properties: LM25-M - LM25-TE - LM25-TB7 - LM25-TF

Strength at elevated temperatures   -   Physical Properties   -   Machinability  -   Corrosion Resistance

Anodizing  -   Casting Characteristics  -   Heat Treatments  -   Applications

This alloy conforms to BS 1490:1988 LM25. Castings are standardized in the as cast (M) condition, the precipitation treated (TE) condition, the solution treated and stabilized (TB7) condition and the fully heat treated (TF) condition.

*If Titanium alone is used for grain refining, the amount present shall be not less than 0.05%

STRENGTH AT ELEVATED TEMPERATURES
The tensile properties of LM25 alloy at elevated temperatures are influenced by the condition (heat treatment) of the castings and the duration at the elevated temperature. On short term testing e.g. 30 minutes at temperature, the properties fall only slowly and uniformly up to about 200 deg.C., at which temperature the strength of LM25-TF is reduced by about 20%. Very prolonged heating e.g., 10,000 hours, results in a sharp loss of strength at about 135 deg. C. At 200 deg. C the strength of LM25-TF is less than half of that at room temperature. There is therefore no advantage to be gained by heat treatment, if the component is to be used at temperatures above about 130 deg C. for extended periods of time.

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PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per deg.C at 20-100 deg.C.)……… 0.000022
Thermal Conductivity (cal/cm2/cm/deg.C. at 25 deg.C)……………….. 0.36
Electrical Conductivity (% copper standard at 20 deg.C.)………………39
Density (g/ cm2)………………………………………………………….2.68

Freezing Range (deg.C.) approx…………………………………………615-550

MACHINABILITY
The heat-treated alloy has fairly good machining properties, but tools should preferably be of high speed steel and must be kept sharp. A moderately high rate of tool wear may be expected. Liberal cutting lubricant should be employed.

CORROSION RESISTANCE
Resistance to corrosive attack by sea water and marine atmospheres is high.

ANODIZING
A protective anodic film can be obtained by either the sulphuric or chromic acid process, but the grey opaque character of coatings of normal thickness precludes their colouring in light shades for decorative purposes.
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CASTING CHARACTERISTICS
FLUIDITY - Good, suitable for fairly thin castings
PRESSURE TIGHTNESS - Excellent, suitable for castings required to be leak tight.
HOT-TEARING - Excellent, problems due to hot tearing are rarely seen.
TYPICAL POURING TEMPERATURE - 710 deg. C.
Practical pouring temperatures will depend on the mould configuration . Care must be taken not to overhead the melt or Magnesium may be lost, resulting in poor properties. Care with Chlorination must also be taken to avoid removing Magnesium.
PATTERN MAKERS SHRINKAGE - 1.3% or 1/75 BACK TO TOP OF PAGE

HEAT TREATMENT
There are three heat treated conditions commonly used for this alloy:

LM25-TE (precipitation treated) - heat for 8-12 hours at 155-175 deg.C. and air cool.

LM25-TB7 (solution treated and stabilised) - heat for 4-12 hours at 525-545 deg.C.and quench in hot water, then stabilise at 250 deg.C. for 2-4 hours.
The time at temperature must be enough to ensure a reasonable stability of the properties, prior to mechanical testing.

LM25-TF (fully heat treated) - heat for 4-12 hours at 525-545 deg.C. and quench in hot water, then precipitation treat of 8-12 hours at 155-175 deg.C. BACK TO TOP OF PAGE

APPLICATIONS
LM25 alloy is mainly used where good mechanical properties are required in castings of a shape or dimensions requiring an alloy of excellent castability in order to achieve the desired standard of soundness. The alloy is also used where resistance to corrosion is and important consideration particularly where high strength is also required. It has good weldability.

Consequently, LM25 finds application in the food, chemical, marine, electrical and many other industries and, above all, in road transport vehicles where it is used for wheels, cylinder blocks, and heads, and other engine and body castings. Its potential uses are increased by its availability in four conditions of heat-treatment in both sand and chill castings. It is, in practice, the general-purpose high strength casting alloy, whose range of uses is increased by its availability in the as-cast and partially heat-treated condition as well. BACK TO TOP OF PAGE

It is used in nuclear energy installations and for aircraft pump parts.

LM25 may be superior for castings, particularly in chill moulds, which are difficult to make to the required standard of soundness. It offers better machinability and mechancial properties than LM6

Please Note:
UK Racing Castings makes no warranty whatsoever, as to the correctness of the information provided herein and accepts no risks or liability for any person(s) relying on the content.