The values shown are typical for sand and chill cast test bars produced to the requirement of B.S. 1490. There are no minimum specification values.
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PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000024 Coefficient of Thermal Expansion (per°C at 20-600°C) 0.0000285 Thermal Conductivity (cal/cm2/cm/°C at 0°C) 0.50 Thermal Conductivity (cal/cm2/cm/°C at 100°C) 0.51 ElectrIcal Conductivity (% copper standard at 20°C)* 57 Density (g/cm3) 2.70 Freezing Range (°C) approx 657-643
* Value is approximate and will vary with the soundness of the casting.
MACHINABILITY
Pure Aluminium, because of its softness and ductility, is more difficult to machine than aluminium alloys and more care is required to obtain a good finish and to overcome “gumminess”. Aluminium tends to build up on the edge of the cutting tool but this can be reduced by the use of cutting compounds and the maintenance of keen cutting surfaces free from grinding marks. Turnings tend to be long and continuous, and must be directed away from the work by generous side and top rake angles.
CORROSION RESISTANCE
Castings of pure Aluminium have excellent resistanceto corrosion in a very wide range of conditions and media.
ANODIZING
Colourless transparent films of adequate thickness can readily be produced on LM0, The anodic coatings are particularly suitable for dyeing to give a coloured finish. Anodizing may also be employed to produce an electrically insulating surface.
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CASTING CHARACTERISTICS
FLUIDITY - Fair, but not recommended for very thin castings.
PRESSURE TIGHTNESS - Fair, it may be difficult to produce leak tight castings.
HOT-TEARING - Fair, there is a tendency to hottearing depending on the casting configuration, and feeding arrangements, LM0 has a very short solidification range and a high solidification shrinkage; therefore special attention must be given to providing optimum temperature gradients for directional solidification.
TYPICAL POURING TEMPERATURE - 730-760°C for sand and permanent mould castings. Higher temperatures may result in coarse grained castings and an increase in hot tearing. Die casting optimum temperatures are machine dependent.
PATTERNMAKERS’ SHRINKAGE - 1.6% or 1/62,
This is high.
HEAT TREATMENT
This alloy is not heat treated.
APPLICATIONS
The use of pure Aluminium castings is comparatively small. The main fields are electrical applications, food and chemical plant, including slush cast spouts, and to a lesser degree, jewellery and light trim. The greatest use is undoubtedly electrical, where the high conductivity of the unalloyed metal offers obvious advantages; in addition, ductility enables it to be readily deformed under pressure and use is made of this, for example, in cable clamps. It is widely used for cast rotors for electric motors but a composition having a higher Iron content than is allowed in LM0, would have better castability and is generally preferred.
The values shown are typical ranges for chill cast test bars produced to the requirement of B.S. 1490. Die cast values obtained on 6mm test bars. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
The reduction in strength of the alloy at elevated temperatures depends upon composition. If the amounts of the elements present, particularly Copper, Nickel and Manganese, are low, the strength is greatly reduced at temperatures of the order of 250°C but, if the maximum permissible amounts of these elements are present, the alloy retains moderate strength at this temperature.
It should be noted that other factors may restrict the use of die castings at elevated temperatures.
The maximum service temperature is 150°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) Thermal Conductivity (cal/cm2/cm/°C at 25°C) Electrical Conductivity (% copper standard at 20°C) Density (g/cm3) Freezing Range (°C) approx
0.000020 0.24 26 2.74 570-525
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 the 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 atmospheres fairly good. It is inferior in this respect to LM6 but can be improved by anodic treatment.
ANODIZING
LM2 can be anodically treated to give a protective surface of a dark grey colour. The surfaces of die castings, however, are not generally suitable for decorative anodizing.
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CASTING CHARACTERISTICS
FLUIDITY -Good, can be cast easily into thin and intricate sections.
PRESSURE TIGHTNESS -Excellent for leak tight castings,
HOT-TEARING -Excellent, this alloy is virtually free from hot tearing.
TYPICAL POURING TEMPERATURE - 615-700°C
Temperatures for die castings are machine dependent,
Melts should not be allowed to stand at temperatures just above thefreezing range or the bottom of the melt will become enriched in alloyingelements such as Iron and Manganese.
PATTERNMAKERS’ SHRINKAGE -1.3% or 1/75
Solidification shrinkage is approximately 3.7%.
HEAT TREATMENT
Castings in this alloy are not normally heat treated, Castings may beannealed at temperatures between 260-370°C, held at temperature between 4-6 hours and furnace cooled.
APPLICATIONS
Essentially a die casting 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 die cast, unless the service conditions demand a higher resistance to corrosion or slightly greater ductility, in which case LM6 or LM20 may be preferred.
For most applications LM2 and LM24 are interchangeable, but LM2 has a slightly lower density, LM6 and LM20 would be betterthan LM2 in a corrosive environment, unless it can be protected by anodizing. LM2 has poor weldability and poor brazeability.
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LM4 (EN 1706 AC-45200)
ALUMINIUM CASTING ALLOY
(Al-Si5Cu3Mn0.5)
Colour Code - RED
This alloy conforms to BS 1490:1988 LM4. Castings are standardized in the as cast (M) condition or fully heat treated (TF) condition.
The values shown are typical ranges for sand and chill cast test bars produced to the
requirement of B.S. 1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Room temperature tensile strength of LM4-M is largely retained up to 200°C and falls to about half at 300°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0. 000021
Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.29
Electrical Conductivity (% copper standard at 20°C) 32
Density (g/cm3) 2.75
Freezing Range (°C) approx 625-525
MACHINABILITY
This alloy has fairly good machining properties, being intermediate between the rather difficult Aluminium-Silicon alloys and the easily machinable Aluminium-Copper group. Liberal cutting lubricant and coolantshould be employed. Castings show improved machinability after heat-treatment.
CORROSION RESISTANCE
Resistance to attack under normal atmospheric conditions is fairly good.Considerable improvement in resistance to corrosion is effected by anodic treatment; a small increase in resistance is obtained when the alloy is solution heat-treated.
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ANODIZING
Treatment by the chromic acid process will give a resistant but generally greyish coloured surface, but a lighter film suitable for dyeing can be obtained with the sulphuric acid method. The colour and quality of the coating depend to some extent upon the condition of the castings, i.e. whether sand or chill cast and whether heat-treated, and also on the thickness of the film.
CASTING CHARACTERISTICS
FLUIDITY - Good,
PRESSURE TIGHTNESS - Excellent, suitable for leak tight castings.
HOT-TEARING - Good, but the placing of feeders or chills at heavy sections of the casting is essential.
TYPICAL POURING TEMPERATURE - 720°C
Temperatures above or below this value may be used depending on the mould configuration. Too high a temperature must be avoided. This alloy may be grain refined.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENT
This alloy’s response to heat treatment is dependent on the presence of Magnesium; therefore for such treatment, the Magnesium content should be near the maximum.
A very considerable increase in mechanical properties is obtained by Solution heat treatment and artificial ageing.
LM4-TF (fully heat treated) - Heat for 6-16 hours at 505-520°C, quench in hot water and heat for 6-18 hours at 150-170°C and air cool.
If bending or straightening of castings is necessary, this should be carried out after the solution heat treatment, since in this state the castings exhibit greatly increased ductility.
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APPLICATIONS
This alloy is widely used and is suitable for most general engineering purposes including cylinder-heads, crank-cases, junction boxes, gearboxes, clutch-cases, switch gear covers, instrument cases, tool-handles and household fittings, office equipment and electrical tools etc., where moderate mechanical properties are desirable. Its casting characteristics permit it to be used forthe production of thick and moderately thin forms and also for castings required to be pressure tight. In the heat treated state, it may be used for castings required to maintain a relatively high static loading. It has good weldability.
LM4 is equally suitable for the production of sand and permanent mould castings but the higher Silicon alloys such as LM2 and LM24 are generally to be preferred.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S.
1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Room temperature properties are largely maintained up to 200°C, but fall rapidly above 300°C.
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PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) Thermal Conductivity (cal/cm2/cm/°C at 25°C)
0.000023 0.33
Electrical Conductivity (% copper standard at 20°C) Density (g/cm3)
31 2.65
Freezing Range (°C) approx 642-580
MACHINABILITY
LM5 machines very well and takes an excellent polish.
CORROSION RESISTANCE
This alloy is highly resistant to corrosion under most conditions and is superior to all other Aluminium alloys for marine use.
ANODIZING
LM5 may be anodized by any of the more common processes.
A transparent colourless-to-whitish film is obtained according to the process used, and is suitable for decorative finishing.
CASTING CHARACTERISTICS
FLUIDITY - Fair, not recommended for very thin castings.
PRESSURE TIGHTNESS - Poor, it may be difficult to obtain pressuretightness in castings other than those of a simple shape.
HOT-TEARING - Fair, the alloy shows a pronounced tendency towards hot-tearing and precautions should be taken to minimise constraint tocontraction in the mould.
TYPICAL POURING TEMPERATURE - 700°C
This temperature should not be greatly exceeded.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
NOTE - This alloy is rather more difficult than most others to melt andcast satisfactorily. Special care must be taken to avoid oxidation duringmelting and during the actual pouring operation. The alloy must bethoroughly de-gassed and, for sand castings of heavy section, theincorporation of Boric acid as an inhibitor in the sand is advocated toprevent the reaction of the alloy with the moisture of the mould whichcan lead to gas porosity and dross inclusions.
HEAT TREATMENT
LM5 alloy is not heat-treated.
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APPLICATION
The alloy is used where very high resistance to corrosion from sea water or marine atmospheres is required, for equipment used for the manufacture of foodstuffs, cooking utensils and chemical plant, and for castings required to exhibit and maintain a surface of high polish. Applications include, for example, door furniture, car fittings and trim, and similar castings where a colourless anodic film is required.
It is mainly used for sand castings and, to a lesser extent, for permanent mould castings but die castings of a relatively simple shape have been made.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Die cast values are obtained from 6mm diameter test bars. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Tensile strength and hardness decrease fairly regularly with increasing temperature and become relatively poor at 250°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000020 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.34 Electrical Conductivity (% copper standard at 20°C) 37 Density (g/cm3) 2.65 Freezing Range (°C) approx 575-565
MACHINABILITY
Alloys of this and similar compositions are rather difficult to machine. This is due to their tendency to drag and to the rapid tool wear caused by the high Silicon content. Carbide-tipped tools with large rake angles and relativelylow 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.
ANODIZING
LM6 can be anodized by any of the common processes, the resulting film ranging in colour from grey to dark brown.
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CASTING CHARACTERISTICS
FLUIDITY - Excellent, can be cast into thinner and more intricate sections than other casting alloys, which makes it useful for producing complex castings of large surface area and thin walls. PRESSURE TIGHTNESS - Excellent, especially suitable for leak tight castings.HOT-TEARING - Excellent, castings in sand or chill moulds arecompletely free from hot tearing.TYPICAL POURING TEMPERATURE - 725°CSand and permanent mould pouring temperatures may be varied inpractice. Die casting pouring temperatures are machine dependent Themolten metal should not be allowed to stand at temperatures just abovethe solidification temperature, as the base of the melt will becomeenriched in alloying elements such as Iron and Manganese.PATTERNMAKERS’ SHRINKAGE -1.3% or 1/75.Die casting shrinkage may be considerably less in some instances.Solidification shrinkage is approximately 3.7%
HEAT TREATMENT
Ductility can be improved slightly by heating at 250-300°C, but, apart from stress relieving, the heat treatment of LM6 is of little industrial interest.
APPLICATIONS
This alloy, having high resistance to corrosion and excellent castability, ismost suitable for marine ‘on deck’ castings, watercooled manifolds andjackets, motor car and road transport fittings, thin section and intricatecastings such as motor housings, meter cases and switch boxes, for verylarge castings, e.g., cast doors and panels where ease of casting isessential, for chemical and dye industry castings, e.g., pump parts, forpaint industry and food and domestic castings. It is especially suitable forcastings that are to be welded.
The ductility of LM6 alloy enables castings to be rectified easily or evenmodified in shape, e.g., simple components may be cast straight and laterbent to the required contour.
It is equally adaptable for sand and permanent mould castings and for diecastings.
This alloy has excellent resistance to corrosion in marine environments,possesses excellent ductility, but is of medium strength and is not heattreated. Its strength falls off rapidly at high temperatures. Its elastic limit islow and there is difficulty with machining.
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LM9 (EN 1706 AC-43100)
ALUMINIUM CASTING ALLOY
(Al –Si12Mg0.5Mn0.5)
Colour Code - YELLOW/BROWN
This alloy conforms to BS 1490:1988 LM9. Castings are standardized in the as cast (M) condition, in the precipitation treated (TE) condition or in the fully heat treated (TF) condition.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S.
1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Tensile properties are unaffected by temperatures up to 150°C but prolonged heating at temperatures significantly higher reduces the strength. For example, the tensile strength of chill cast LM9-TF at 200°C (after heating for 500 h) is approximately half that at room temperature, and only 25% of the original value at 250°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000022 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.35 Electrical Conductivity (% copper standard at 20°C) 38 Density (g/cm3) 2.68 Freezing Range (°C) approx 575-550
MACHINABILITY
Very considerable tool wear occurs in machining this alloy, but there is not the same tendency to drag that occurs with high Silicon alloys containing no other alloying elements, e.g. LM6. Carbide-tipped tools with large rake angles and relatively low cutting speeds give good results. A cutting lubricant and coolant should be employed.
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CORROSION RESISTANCE
LM9 exhibits excellent resistance to corrosion under both ordinary atmospheric and marine conditions.
ANODIZING
LM9 can be anodized by any of the common processes, the resulting protective film ranging in colour from grey to dark brown, depending on the method employed.
CASTING CHARACTERISTICS
FLUIDITY - Good, suitable for thin and intricate castings.
PRESSURE TIGHTNESS - Good, suitable for leak tight castings.
HOT-TEARING - Excellent, castings are completely free from hot tears
in sand and chill moulds.
TYPICAL POURING TEMPERATURE -710°C
The mould design will influence the actual pouring temperature. Thepresence of Magnesium , which will oxidize if the melt is at too high atemperature or kept too long at temperature, requires more care to beexercised in the melting and casting of this alloy. Oxide could beintroduced into the casting by accident
For sand castings and medium and heavy chill castings, the normalpractice is to modify the melt with Sodium.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENTHeat treatment produces high strength and hardness.LM9-TE ( precipitation heat treated ) - Heat for 16 hours at 150-170°C.LM9-TF (fully heat treated ) - Heat for 2-8 hours at 520-535°C, and quenchin water and heat for 16 hours at 150-170°C.
APPLICATIONS
LM9 alloy is used where the fluidity and corrosion resistance of LM6 arerequired with high strength and hardness. It is equally suitable for sand andpermanent mould casting and is extensively used for low pressurecastings, for cover plates and instrument cases. It is useful forelectroplated components. LM9 has poor weldability and brazeability.
The values shown are typical ranges for chill cast test bars produced to the requirement of B.S. 1490. Those in heaviertype are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Tensile strength and a high proof stress/ultimate tensile stress ratio are well maintained at elevated temperatures.
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PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000022 Coefficient of Thermal Expansion (per°C at 20-300°C)Thermal Conductivity (cal/cm2/cm/°C at 25°C)
0.000024 0.32
Electrical Conductivity (% copper standard at 20°C)Density (g/cm3)
33 2.94
Freezing Range (°C) approx 625-525
MACHINABILITY
This machines very well and takes a high polish. Ordinary machining methods, as applied for example to gun metal, give very satisfactory results, But high cutting speeds may be used to advantage.
CORROSION RESISTANCE
Resistance to seawater and atmospheric conditions is rather lower than that of the Copper-free Aluminium alloys. This does not detract from the value of LM12 for many applications; for most engineering purposes the resistance is satisfactory. Resistance to corrosion by oils and fatty acids is very good.
ANODIZING
This alloy is not recommended for anodic treatment, although a non-protective film may be obtained by the sulphuric acid process.
CASTING CHARACTERISTICS FLUIDITY - Fair, not recommended for very thin castings. PRESSURE TIGHTNESS - Good, produces very sound castings,
especially when chill cast. HOT-TEARING - Good, exhibits moderate resistance to hot tearing. TYPICAL POURING TEMPERATURE - 710°C The mould configuration will influence the optimum temperature. PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENT
This alloy will respond to heat treatment to give increased strength and hardness. BS 1490 does not specify heat treated properties for this alloy.
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APPLICATIONS
In the past, the main uses for LM12 were for pistons in intemal combustion engines, but in this field it has been superseded by LM1 3 and LM26 which have the advantage of a lower thermal expansion.
The alloy now finds its main applications where castings are required to withstand high hydraulic pressures or to possess maximum hardness, and where machinability is of first importance. Typical applications are castings for hydraulic brake and similar systems and electric iron sole plates.
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LM13 (EN 1706 AC-43100)
ALUMINIUM CASTING ALLOY (Al-Si12CulMgl)
Colour Code - YELLOW/BLACK
This alloy conforms to BS 1490:1988 LM13. Castings are standardized in the precipitation treated (TE) condition, solution treated, artificially aged and stabilized (TF7) condition and the fully heat treated (TF) condition.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
Strength and hardness, at temperatures met in internal combustion engine pistons, are high enough to allow the alloy to be used satisfactorily for such applications, but strength is halved at 250°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000019 Coefficient of Thermal Expansion (per°C at 20-300°C) 0.000021 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.28 Electrical Conductivity (% copper standard at 25°C) 29 Density (g/cm3) 2.70 Freezing Range (°C) approx 560-525
MACHINABILITY
In machining this alloy, there is less tendency to drag than with high Silicon alloys containing no other alloying elements, for example LM6. Ordinary steel tools tend to wear rather quickly and should not be used. Carbide-tipped tools with large rake angles and relatively low cutting speeds give good results. A cutting lubricant and coolant should be employed. Diamond tools are commonly used for finish machining.
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CORROSION RESISTANCE
This alloy shows high resistance to corrosion under atmospheric conditions.
ANODIZING
LMI3 may be anodized satisfactorily by the sulphuric acid process. The anodic coating is dark grey. Anodizing, which produces an oil absorbing surface, is sometimes used to give improved bearing qualities to pistons made of LM13.
CASTING CHARACTERISTICS FLUIDITY - Good, this alloy can be cast into thin sections. PRESSURE TIGHTNESS - Fair, suitable for leak tight castings. HOT-TEARING - Excellent, resistance to hot tearing is high. TYPICAL POURING TEMPERATURE -700°C
The actual temperatures may range between 670-780°C and will depend on the mould configuration. This alloy may form internal shrinkage pipes in heavy sections. PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENT
LM13-TF (fully heat treated)- heat for 8 hours at 515-525°C, quench in hot water, and heat for 4-16 hours at 160-180°C.
For large castings it may be necessary to increase the solution heat treatment time.
A stabilizing treatment is commonly employed for pistons.
LM13-TF7 (solution heat treat, quench and stabilize)- Solution heat treat and quench as described for LM13-TF then - heat for 4-16 hours at 200250°C or for such time as will give the desired hardness.
LM13-TE (precipitation hardened)- heat for4-16 hours at 160-180°C, or for such duration as is required to reach the specified Brinell hardness.
APPLICATIONS
LM13 alloy is used for pulleys (sheaves), for pistons for all types of diesel and petrol engines, and for other engine parts operating at elevated temperatures. It has the advantage of good resistance to wear, good bearing properties and a low coefficient of thermal expansion.
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LM16 (EN 1706 AC-45300)
ALUMINIUM CASTING ALLOY (Al -Si5CulMg0.5)
Colour Code - RED/BLACK
This alloy conforms to BS 1490:1988 LM16. Castings are standardized in the solution treated and naturally aged (TB) condition and in the fully heat treated (TF) condition.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES LM16 retains its strength well, up to 200°C.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20 -100°C) 0.000023 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.34 Electrical Conductivity (% copper standard at 20°C) 39 Density (g/cm3) 2.70 Freezing Range (°C) approx 620-550
MACHINABILITY
The heat-treated alloy has fairly good machining properties, but tools, which should preferably be of high speed steel, must be kept sharp. A moderately high rate of tool wear may be expected. Liberal cutting lubricant should be employed.
CORROSION RESISTANCE
The alloy has fairly good resistance to corrosion under atmospheric conditions.
ANODIZING
A protective film, usually grayish in colour, may be obtained by either the sulphuric or chromic acid process.
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CASTING CHARACTERISTICS
FLUIDITY - Good, suitable for fairly thin castings. PRESSURE TIGHTNESS - Good, suitable for leak tight castings. HOTTEARING - Good, hot tears are seldom encountered with this alloy.
TYPICAL POURING TEMPERATURE -710°C
The actual temperature may range between 675-790°C dependent on the mould configuration. Care needs to be taken to avoid oxide inclusions in the casting due to the presence of 0.5% Magnesium in this alloy.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENT
Full heat treatment gives high strength and hardness:
LM16-TB ( solution heat treated ) - 12 hours at 520-530°C and quenched in hot water.
LM16-TF ( precipitation heat treated ) - 12 hours at 520-530°C and quenched in hot water followed by 8-10 hours at 160-170°C.
APPLICATIONS
LM16 alloy is used for water-cooled cylinder heads, valve bodies, water jackets, cylinder blocks, fire hose couplings, air compressor pistons, fuel pump bodies, aircraft supercharger covers and similar applications where leak-proof castings having the high strength produced by heat-treatment are required. It is equally suitable for sand casting and for permanent mould casting. LM16 has good weldability.
The values shown are typical ranges for Chill and Die cast test bars produced to the requirement of B.S. 1490. The die cast test bars were of 6mm diameter. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
Tensile strength and hardness decrease fairly regularly with increasing temperature and become relatively poor at temperatures of the order of 200°C, with a corresponding increase in elongation.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000020 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.37 Electrical Conductivity (% copper standard at 20°C) 37 Density (g/cm3) 2.68 Freezing Range (°C) approx 575-565
MACHINABILITY
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 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.
CORROSION RESISTANCE
LM20 exhibits high resistance to corrosion under both ordinary atmospheric and marine conditions, being only slightly inferior in this respect to LM6. Resistance may be considerably increased by anodic treatment.
ANODIZING
LM20 can be anodized by any of the common processes. The resulting protective film ranges in colour from grey to dark brown. The surfaces of die castings are not generally suitable for decorative anodizing.
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CASTING CHARACTERISTICS
FLUIDITY - Excellent, this alloy can be cast into thin and intricatecastings.
PRESSURE TIGHTNESS - Excellent, especially suitable for leaktight castings.
HOT-TEARING - Excellent, castings are free from hot tearing.
TYPICAL POURING TEMPERATURE - The practical pouring temperatures are dependent on the die casting machine and thecasting dimensions.
The melt should not be allowed to stand at temperatures justabove the freezing range as the bottom of the melt will becomeenriched in Iron and Manganese.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75
The solidification shrinkage for this alloy is 3.7%.
HEAT TREATMENT
Castings in this alloy are not heat treated.
APPLICATIONS
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 LM24 only when the castings are used in aggressive media, requiring the rather higher corrosion resistance of LM20. Where the very highest resistance to chemical attack is required, LM6 alloy may be superior to LM20.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
Room temperature strength is largely retained up to 200°C and falls to about half at 300°C. The creep resistance of the alloy at 200°C is not significantly different from that of LM4.
PHYSICAL PROPERTIES Coefficient of Thermal Expansion (per°C at 20-100°C) Thermal Conductivity (cal/cm2/cm/°C at 25°C)
0.000021 0.29
Electrical Conductivity (% copper standard at 20°C) Density (g/cm3)
32 2.81
Freezing Range (°C) approx 615-520
MACHINABILITY
LM21 has fairly good machining properties and is rather superior in this respect to LM4-M. For the best results, tungsten carbide tools are recommended. Liberal applications of cutting lubricant and coolant should be used.
CORROSION RESISTANCE
The alloy shows fairly good resistance to attack under normal atmospheric conditions. Atmospheric exposure tests carried out by the British NonFerrous Metals Research Association indicate that the weathering behaviour of LM21 is similar to that of LM4 alloy.
ANODIZING
Treatment by either the sulphuric or chromic acid process will give a resistant but slightly greyish coloured surface, the colour and quality of the coating depending to some extent upon the condition of the castings, i.e. whether sand or chill cast
CASTING CHARACTERISTICS
FLUIDITY - Good.
PRESSURE TIGHTNESS - Good, suitable for leak tight castings.
HOT-TEARING - Good.
TYPICAL POURING TEMPERATURE - 720°C
The practical pouring temperatures will depend on the mould configuration and may range from 675-790°C.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
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HEAT TREATMENT
The mechanical strength of LM21 can be increased by heat treatment, but the behaviour of castings that have been heat treated may vary considerably due to variations in composition within the specified range. For this reason, where high mechanical strength and hardness are required, the use of a recognised heat treatable alloy e.g., LM4-TF is recommended.
LM21 can be successfully stress relieved.
Age hardening which occurs spontaneously at room temperature is rather greater than with LM4 castings. If bending or straightening of castings is necessary, it should be done soon after casting, as at this stage the alloy has the greatest ductility.
APPLICATIONS
LM21 is suitable for many of the applications for which LM4 may be used, i.e., for general engineering purposes. It is mainly used where a high proof stress and rigidity are required without the need for heat-treatment.
Its casting characteristics permit it to be used for the production of moderately thin forms and also for castings required to be pressure tight
LM21 is equally suitable for sand and permanent mould castings. It is used for crank cases for diesel engines, clutch cases, gear boxes, tool handles, household fittings, electrical tools and office equipment.
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LM22 (EN 1706 AC-45000)
ALUMINIUM CASTING ALLOY (Al -Si5Cu3Mn0.4)
Colour Code - RED/BROWN
This alloy conforms to BS 1490:1988 LM22. Castings are standardized in the solution treated and naturally aged (TB) condition.
The values shown are typical ranges for chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
Room temperature strength is largely retained up to 200°C.
PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000021 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.29 Electrical Conductivity (% copper standard at 20°C) 32 Density (g/cm3) 2.77 Freezing Range (°C) approx 625-525
MACHINABILITY
Chill castings in LM22-TB alloy have good machining properties. Moderately high tool wear must, however, be expected as with other Silicon containing alloys. Liberal cutting lubricant and coolant should be employed.
CORROSION RESISTANCE
Resistance to attack under commonly encountered atmospheric conditions is fairly good. Solution treatment makes this alloy slightly superior to LM4 in its resistance to corrosion.
ANODIZING
Treatment by the chromic acid process produces a resistant but greyish coloured surface. A lighter film suitable for dyeing is obtainable with the sulphuric acid method.
CASTING CHARACTERISTICS FLUIDITY - Good.
PRESSURE TIGHTNESS - Good, suitable for leak tight castings.
HOT-TEARING -Good.
TYPICAL POURING TEMPERATURE - 720°C
In practice the optimum pouring temperature will depend on the mould configuration.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
HEAT TREATMENT
Castings are normally used in the solution heat treated condition.
LM22-TB (solution treated) - heat for 6-9 hours at 515-530°C and quench in hot water.
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APPLICATIONS
The main characteristics of this alloy, in addition to ease of founding, are excellent shock resistance and tensile strength. Limitation of Magnesium to a very small content prevents serious age-hardening and so ensures that a high order of resistance to impact loading is maintained.
Castings, normally produced in chill moulds and solution treated, are mainly used for heavy duty service in road transport vehicles, e.g., as cross bearers and other structural components.
The values shown are typical ranges for Chill and Die cast test bars produced to the requirement of B.S. 1490. Die cast test bars were 6mm diameter. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
Room temperature tensile strength is largely retained up to temperatures in the order of 150°C, and approximately halved at 250°C.
It should be noted that other factors may restrict the use of die castings at elevated temperatures.
PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) Thermal Conductivity (cal/cm2/cm/°C at 25°C)
0.000021 0.23
Electrical Conductivity (% copper standard at 20°C) Density (g/cm3)
24 2.79
Freezing Range (°C) approx 580-520
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 reground 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, i.e. fairly good. In marine atmospheres, or under other severe conditions, castings of this alloy should be protected by painting.
ANODIZING
Anodizing treatment by either the chromic or sulphuric acid process produces an anodic film of a grey colour. The surfaces of die castings are not generally suitable for decorative anodizing. Anodizing would be necessary if this alloy is for use in a corrosive environment.
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CASTING CHARACTERISTICS
FLUIDITY - Good, this alloy is used successfully for thin sections.
PRESSURE TIGHTNESS - Excellent, suitable for leak tight castings.
HOT-TEARING - Excellent, castings can be produced without hot
tears.
TYPICAL POURING TEMPERATURE - 700°C
Pouring temperatures for die castings depend on the machine and casting dimensions; pouring temperatures may vary between 630710°C. The melt should not be allowed to stand at temperatures just above the freezing range as the bottom of the melt will become enriched in Iron and Manganese.
PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75
HEAT TREATMENT
Castings in this alloy are not heat treated.
APPLICATIONS
LM24 is essentially a pressure die casting alloy, for which it has excellent casting characteristics and is generally a little simpler to die cast 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 die castings 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 die casting alloy in the United States of America, and a similar alloy has recently been adopted by the European Die Casting Committee.
It is used for vacuum cleaners, floor polishers, motor frames and housings.
LM24 has poor weldability and brazeability. For the vast majority of die castings, the alloys LM2 and LM24 are equally suitable.
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LM25 (EN 1706 AC-42000)
ALUMINIUM CASTING ALLOY (Al-Si7Mg0.5)
Colour Code - YELLOW/BLUE
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.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
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°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°C. At 200°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°C,for extended periods of time.
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PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000022 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.36 Electrical Conductivity (% copper standard at 20°C) 39 Density (g/cm3) 2.68 Freezing Range (°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.
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°C
Practical pouring temperatures will depend on the mould configuration. Care must be taken not to overheat 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
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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°C and air cool.
LM25-TB7 ( solution treated and stabilized ) - heat for 4-12 hours at 525545°C and quench in hot water, then stabilize at 250°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°C and quench in hot water, then precipitation treat of 8-12 hours at 155-175°C.
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 an 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.
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 mechanical properties than LM6.
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LM26
ALUMINIUM CASTING ALLOY (A1-Si10Cu3Mgl)
Colour Code - BROWN/BLUE
This alloy conforms to BS 1490:1988 LM26. Castings are standardized in the precipitation treated and artificially aged (TE) condition.
The values shown are typical ranges for chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
STRENGTH AT ELEVATED TEMPERATURES
The strength and hardness of LM26 at temperatures met in internal combustion engines are high enough for use in such applications. Tensile strength is halved at 270°C and is reduced to 55 N/mm2 at 370°C.
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PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000021 Coefficient of Thermal Expansion (per°C at 100-300°C) Thermal Conductivity (caI/cm2/cm/°C at 25°C)
0.000023 0.25
Electrical Conductivity (% copper standard at 20°C) Density (g/cm3)
26 2.76
Freezing Range (°C) approx 580-520
MACHINABILITY
In machining this alloy there is less tendency to drag than with high Silicon alloys containing no other alloying elements, for example LM6. The machinability of LM26 is slightly superior to that of LM13. Ordinary steel tools tend to wear rather quickly and should not be used, but carbide-tipped tools with large rake angles and relatively low cutting speeds give good results. A cutting lubricant and coolant should be employed. Diamond tools are commonly used for finish machining.
CORROSION RESISTANCE
Resistance to atmospheric corrosion is fairly good but is of little practical significance for an alloy which is used almost solely for pistons for internal combustion engines.
ANODIZING
LM26 may be anodized satisfactorily by the sulphuric acid process. The anodic coating is dark grey. Anodizing, which produces an oil absorbing surface, is sometimes used to give improved bearing qualities to pistons.
CASTING CHARACTERISTICS
FLUIDITY - Good, can be cast into relatively thin sections.PRESSURE TIGHTNESS - Fair, suitable for leak tight castings.HOT-TEARING - Excellent. Hot tearing is rarely encountered withthis alloy.TYPICAL POURING TEMPERATURE-700°CIn practice, the actual temperatures may range above or below thisvalue and will depend on the mould configuration.PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
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HEAT TREATMENT
For cast pistons, the heat treatment usually consists of heating the castings at 200-210°C for 7-9 hours and air cooling in still air.
APPLICATIONS
The particular characteristics which determine the applications of this alloy are its low coefficient of thermal expansion, its retention of strength and hardness at elevated temperatures and its high resistance to wear. Its main use is in petrol and diesel engine pistons. The alloy is widely employed for such purposes in the USA under the designation SAE 332. It is an alternative to LM13.
The values shown are typical ranges for sand and chill cast test bars produced to the requirement of B.S. 1490. Those in heavier type are minimum specification values.
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STRENGTH AT ELEVATED TEMPERATURES
LM27 alloy retains a high proportion of its original room temperature strength at moderately elevated temperatures. For short period exposure, the tensile strength of chill castings is reduced by only 20% at 200°C and by 40% at 250° C. The reduction in proof stress is considerably less.
PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per°C at 20-100°C) 0.0000215 Thermal Conductivity (cal/cm2/cm/°C at 25°C) 0.37 Electrical Conductivity (% copper standard at 20°C) 27 Density (g/cm3) 2.75 Freezing Range (°C) approx 605-525
MACHINABILITY
LM27 has fairly good machining characteristics and is similar in this respect to LM4-M. For the best results, tungsten carbide tools are recommended. Liberal use of cutting lubricant and coolant is advised.
CORROSION RESISTANCE
Resistance to attack under normal atmospheric conditions is fairly good.
ANODIZING
Treatment by the more common processes produces a protective surface with a greyish opaque film. Anodizing for decorative purposes is generally impracticable for the depth of anodic coating required to ensure adequate durability.
CASTING CHARACTERISTICS
FLUIDITY - Good, suitable for thin castings.PRESSURE TIGHTNESS - Excellent, particularly suitable for castings required to be leak tight.HOT-TEARING - Excellent, hot tearing problems are seldom encountered with this alloy.TYPICAL POURING TEMPERATURE - 710°CPractical temperatures will vary above or below this valuedependent on the mould configuration.PATTERNMAKERS’ SHRINKAGE - 1.3% or 1/75.
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HEAT TREATMENT
This alloy is standardized in the as cast condition, but it has been shown that the tensile properties may be substantially increased by an appropriate heat treatment. The response to heat treatment is dependent on the presence of Magnesium so it is important that castings for heat treating should have a Magnesium content at the top of the range, (0.35% max).
LM27 -TB7 ( Solution heat treated and stabilized ) heat for 6-16 hours at 505-525°C then quench in hot water, and heat for 6-16 hours at 160170°C.
The mechanical properties obtained from this treatment depend on the Magnesium content, and are of the following order:
LM27 is a very versatile alloy and, with its excellent castability, it is suitable for most general purpose castings where moderate mechanical properties are desirable, such as general engineering components, domestic and office equipment, household fittings, electrical tools and switch gear, automobile engine and transmission components.
It is equally suitable for sand and permanent mould castings of thick or thin sections, and for castings required to be pressure tight. In short, it can be used with the advantage of slightly superior castability for all the kinds of applications for which LM4 is used.
