Aluminium Casting Alloy
(Al – Si7Mg)
This alloy conforms to British Standard 1490 LM25. Castings are standardid in the following conditions - as cast, LM25-M precipitation treated LM25 - TE; solution treated and stabilized LM25 - TB7; and fully heat -treated LM25 - TF.
CHEMICAL COMPOSITION
%
Copper0.1 max.
Magnesium0.20-0.60
Silicon 6.5-7.5
Iron0.5 max.按摩项目
Mangane0.3 max.
Nickel0.1 max.
Zinc0.1 max.
Lead0.1 max.
Tin0.05 max.
Titanium*0.2 max.
Aluminium Remainder.
* 0.05% min. if Titanium alone ud for grain refining.
MECHANICAL PROPERTIES
Sand Cast
LM25-M LM25-TE LM25-TB7 LM25-TF
0.2% Proof Stress (N/mm2)*80-100 120-150 80-110 200-250
Tensile Stress (N/mm2)*130-150 150-180 160230-280
Elongation (0%)* 2 1 2.5
Brinell Hardness Number55-6570-7565-75 90-110
Endurance Limit (5 X 108 Cycles + N/mm2) 70-100 556060
Modulas of Elasticity (X 103 N/mm2) 71 71 7171
Chill Cast
LM25-M LM25-TE LM25-TB7 LM25 TF
0.2% Proof Stress N/mm2) *80-100 130-200 90-110220-260
绵绵小雨
Tensile Stress (N/mm2)*160-200190-250 230280-320
Elongation (%)32 5 h2
Brinell Hardness Number 55-65 75-9565-7590-110
Endurance Limit (5 X 108 Cycles + N/mm2 80-11075 95 95
Modulus of Elasticity (x 103 N/mm2) 71 71 7171
* The values shown are typical ranges for test bars produced to the requirements of B.S.1490. Specification minima are in bold type.
Aluminium Casting Alloy
(Al – Si7Mg)
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. For short term 30 minutes at temperature, the properties fall only slowly and uniformly up to about 200o C at which temperature for example, the strength of LM25-TF is reduced by approximately 20%, Very prolonged heating (10,000 hours) results in sharp, loss of strength at about135o C and at 200o C the strength on LM25-TS is less than half of that at room temperature. For prolonged rvice at elevated temperatures (above 130o C) there is, therefore, no practical advantage to be gained by heat treatment.
键PHYSICAL PROPERTIES
Coefficient of Thermal Expansion (per o C at 20 -100 o C) 0.000022
Thermal Conductivity (cal/cm2/cm/o C/s at 25o C * 0.36
Electrical Conductivity (% copper standard at 20o C) *39
Specific Gravity 2.68
有一种力量
Freezing Range (o C) Approx615-550
*Applies to fully heat treated sand castings; values are approximate and for castings in other conditions will depend on their thermal history.
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 a water and marine atmospheres is high.
ANODISING
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 purpos. CASTING CHARACTERISTICS
党章的意义
FLUIDITY Good, suitable for fairly thin castings.
我爱这土地艾青PRESSURE TEST Suitable for castings required to be leak tight.
HOT TEARING The production of castings in this alloy very rarely introduces
problems due to hot tearing.
TYPICAL POURING TEMPERATURE-710o C The actual temperatures employed may range considerably
above or below this value and will depend upon the particular
conditions for each castings.
Aluminium Casting Alloy
(Al – Si7Mg)
NOTE
Achievement of the specified minimum tensile properties is dependent on maintaining the optimum magnesium content. Care must therefore be taken during melting and degassing to avoid loss of magnesium by oxidation resulting from overheating or by excessive chlorination.
HEAT TREATMENT
LM25-TE (Precipitation treated) - Heat for 8-12 hours at 155- 175o C and allow to cool in air
LM25-TB7 (Solution treated and stabilized)-heat for 4-12 hours at 525-545o C and quench in hot water, followed by a stabilizing treatment at 250o C for 2-4 hours.
LM25-TF(Fully heat treated)- heat for 4-12 hours at 525- 545o C and quench in hot water, followed by a precipitation treatment of 8-12 hours at 155-175o C
APPLICATION
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助学金感谢信LM25 alloy is mainly ud 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 ud where resistance to corrosion is an important consideration particularly where high strength is also required.
Conquently LM25 finds application in the food, chemical, marine, electrical and many other industries and above all in road transport vehicles where it is ud for cylinder blocks and heads, and other engine and body castings. Its potential us are incread by it's availability in four conditions of heat treatment in both sand and chill castings. It is, in practice, the general purpo high strength casting alloy.
HADLEIGH CASTINGS LIMITED
Pond Hall Road
Hadleigh
Ipswich
Suffolk
IP7 5PW
England
Tele:44 (0) 1473 827281
Fax:44 (0) 1473 827879
