Alloy Specification Charts

LM2LM6LM20LM24LM25ZL3ZL5ZL27

LM2

L M 2 is essentially a pressure diecasting alloy conforming to BS1490 1988, this alloy is often specified as an alternative LM 24 in pressure diecasting applications.

Application

LM 2 is a general-purpose alloy suitable for the manufacture of almost any diecast part. It is often specified on large volume diecast applications in preference to LM 24 because of its lower density. By implication this means that applications for this alloy are quite wide and varied. Service conditions which dictate high corrosion resistance or higher than usual ductility would normally require an alternative alloy. The chemistry present has a marked effect on the mechanical properties achieved; low levels of copper, nickel and manganese reduce the strength at temperatures above 250°C. For this reason it is advisable to restrict the service conditions to a maximum of 150°C. Corrosion resistance is inferior to LM 6 but use in normal atmospheric conditions is acceptable. Anodising of LM 2 castings is possible, but only on decorative finishes, as a grey film will result.

LM 2 castings are not normally heat-treated but annealing is possible to improve ductility.

The high silicon levels present in this alloy mean that machining can be marginally difficult and result in excessive tool wear. The copper element does mean that drag during machining is reduced making this alloy easier to machine than LM 6 or 20. Castings made from LM are not suitable for welding or brazing.

The composition of this alloy is typical of that used throughout Europe and the United States of America.

lm2
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LM6

L M 6 can be used as a pressure diecasting alloy but is also suitable for both gravity and low pressure casting techniques. The alloy in this designation conforms to BS 1490 and similar alloy chemistries are used worldwide, see below for guidance.

Application

LM 6 is a high purity alloy, which is used in castings where thinner more intricate sections are required. Particularly, complex castings with large surface areas. The alloy is of medium  strength with excellent ductility but suffers a rapid loss of properties at elevated service
temperatures. At around 2500 C the properties of this alloy become very poor.

This alloy possesses high corrosion resistance and excellent castability making it suitable for marine fittings, water manifolds and road transport applications. This corrosion resistance can be further enhanced by anodising, which may result in a variable grey to brown coloured film on the castings surface.

LM 6 is a high Silicon Aluminium alloy which can be rather difficult to machine. Alloys of this type tend to drag when machined, causing rapid tool wear and therefore carbide tools with large rake angles should be employed with adequate cutting fluids.

This alloy is particularly suitable for castings that are to be welded.

This alloy is similar to the following national specifications:

lm6
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LM20

LM20 alloy is rather difficult to machine because of the rapid tool wear caused by the high silicon content and because of its tendency to drag. The small amount of copper present results however in a slight superiority in this latter respect over 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.

LM20 exhibits high resistance to corrosion under both ordinary atmospheric and marine conditions being only slightly inferior in respect to LM6; resistance may be considerably increased by anodic treatment.

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 die castings, however, are not generally  suitable for decorative anodising.

Application

LM20 is suitable for marine castings, water jackets, meter cases, domestic and office equipment, street lighting and other castings subjected to atmospheric exposure.

In general LM20 alloy is preferred to the more common die casting alloys LM2 and 24 only when the castings are used in aggressive media requiring the rather higher corrosion resistance of the copper-free alloy. Where the very highest resistance to chemical attack is required LM6 alloy may be superior to LM20.

lm20
Content supplied by Brock Metal

LM24

L M 24 is essentially a pressure diecasting alloy which conforms to BS 1490 1988 and is the most widely used of the sconary aluminium casting alloys manufactured by Brock Metal.

Application

LM 24 is a general-purpose alloy suitable for high volume precision diecastings. This alloy offers excellent casting characteristics and good mechanical properties that make it ideal for engineering and functional parts, being ideally suited for the manufacture of thin wall sectioned castings. LM 24 offers excellent pressure retention properties and similar machining characteristics to other pressure diecasting alloys, but should not be specified where high resistance to corrosion is a critical requirement. The surfaces of LM 24
castings are not generally suitable for decorative anodising but other decorative finishes can be achieved easily.

It should be noted that pressure castings are not normally suitable for heat treatment. LM 24 retains its ambient temperature tensile strength up to approximately 150°C but a 50% loss in these figures should be anticipated at around 250°C.

The composition of this alloy is typical of that used throughout Europe and the United States of America.

lm24
Content supplied by Brock Metal

LM25

LM25 is an aluminium alloy that conforms to BS 1490 and is particularly suitable for use in high quality castings where strength, definition and good corrosion resistance is important. Alloys with similar chemical composition are used throughout the world, see below for details.

Application

LM25 is a high purity aluminium alloy, which can be gravity diecast in permanent moulds or sand. It has excellent castability and good mechanical properties that can be varied by heat treatment. The alloy is mostly used for high specification castings in industries where shape and complex form is required and casting soundness is important. Its use is widespread in the automotive industries for alloy wheels, cylinder heads and blocks and in many other industries such as chemical, marine and electrical.

Castings made from this alloy can be supplied in the as cast form or in one of three other heat treated conditions.

It should be noted that there is no significant advantage to be gained from heat treatment if the service conditions envisaged are likely to include extended periods at temperatures above 130°C. However, hardness, tensile strength and elongation can be significantly improved by heat treatment. Castings in this can be supplied in the M, TE, TB 7 and TF conditions.

This alloy has excellent resistance to seawater attack and can be anodised to improve its corrosion resistance. Anodising will give a grey / opaque finish suitable for dark decorative finishes only. LM 25 also has good machining characteristics and can be welded if required.

This alloy is similar to the following international specifications:

lm25
Content supplied by Brock Metal

ZL3

ZL3 is a pressure die casting zinc base alloy which conforms to BS EN 1774 and is one of a family of versatile high grade zinc alloys manufactured by Brock Metal.

Application

ZL3 is a general-purpose alloy and is primarily used for producing castings for a variety of applications on a hot chamber pressure die casting machine. The alloy’s mechanical and physical properties make it ideal for use in castings for the engineering and automotive industry, household equipment and utensils, office equipment, builder’s hardware, locks, toys, giftware etc. ZL3 is easily machined, buffed, polished, lacquered and electroplated for decorative or functional purposes.

When designing a stressed component using ZL3 further reference should be made to the alloys properties, at elevated temperatures, after natural or artificial ageing and the alloys creep properties.

zl3
Content supplied by Brock Metal

ZL5

ZL5 is a pressure die casting zinc base alloy which conforms to BS EN 1774 and is one of a family of versatile high grade zinc alloys manufactured by Brock Metal.

Application

ZL5 is generally used for castings that require moderately higher strength and hardness and where dimensional stability is not an important criterion in the product application. ZL5 is often specified for automotive applications in Europe. The alloy contains Copper as specified element, this promotes marginally better casting properties than the ZL3 alloy and improves mechanical properties. The nominal 1% makes the alloy more expensive and therefore its use should be restricted to applications requiring its higher properties. ZL5 will accept any finish specified for ZL3.

When designing a stressed component using ZL5 further reference should be made to the alloys properties, at elevated temperatures, after natural or artificial ageing and the alloys creep properties.

zl5
Content supplied by Brock Metal

ZL27

ZL27 is a high aluminium content zinc alloy that conforms to BS EN 1774 and is one of a family of versatile high grade zinc alloys.

Application

ZL27 is a zinc alloy containing 27% aluminium. It has exceptionally high strength and excellent bearing properties. Originally this alloy was envisaged for use in the sand and gravity diecasting industries but, has subsequently found a niche market as a pressure diecasting alloy using cold chamber diecasting machines. ZL27 offers the extended tool life applicable to zinc alloys which, when combined with its higher strength and hardness makes the alloy an automatic choice when aluminium alloys are unable to meet the service conditions anticipated.

When designing a stressed component using ZL27 further reference should be made to the alloys properties, at elevated temperatures, after natural or artificial ageing and the alloys creep properties.

zl27
Content supplied by Brock Metal