Casting alloys 

Casting alloys of aluminum-tin

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These aluminum alloys, doped tin, specially developed for bearings. Quality bearings main criteria are the load-bearing capacity, fatigue and corrosion resistance in lubrication conditions in internal combustion engines. Aluminum Alloy Bearings, tin alloyed, unsurpassed among other types of bearing materials.

Aluminum tin phase diagram

fazovaya-diagramma-alyuminiy-olovo
Aluminum tin phase diagram

Aluminum-tin alloys contain about tin 6 %, as well as small amounts of copper and nickel to increase strength. They are used for cast bearings.. It is tin that provides very good glide in these alloys..

American aluminum-tin alloys

American Tin Aluminum Alloys 850.0, 850.1 and 852.0 can be cast as in sand, so in the chill mold. However alloys 850.0 (6,3Sn-1Cu-1Ni) and 852.0 (6,3Sn-2Cu-1,2Ni-0,8Mg) is usually poured only into permanent forms. Sand casting is used for large rolling mill bearings, which are usually made of alloy 851.0 (6,3Sn-2,5Si-1Cu-0,5Ni).

Bearing structure

The “bearing” properties of aluminum-tin alloys are highly dependent on the casting method. Finely dispersed tin distribution is essential for optimum bearing properties.. This requires a small interdendritic distance., and such a distance can only be obtained with fast cooling casting methods.

Long cure interval

In terms of the casting process, the aluminum-tin alloy system is unique. The solidification of the alloy in the mold begins at a temperature of about 650 oC, and the tin remains liquid somewhere up to the temperature 225 oC. Such a too large temperature hardening range presents difficulties for casting. High solidification rates of castings are recommended to avoid excessive macrosegregation..

A casting aluminum alloy 850.0

Alloy formula:

6,2Sn-1Cu-1Ni

Chemical composition:

  • copper: 0,7-1,3 %;
  • magnesium: 0,10 Max.;
  • silicon: 0,7 % Max.;
  • iron: 0,7 % Max.
  • lead: 5,5-7,0 %;
  • nickel: 0,7-1,3 %;
  • titanium: 0,20 % Max.;
  • others: 0,30 % Max.;
  • aluminum: rest.

Influence of impurity content:

  • high iron content, manganese or magnesium reduces plasticity and increases hardness;
  • high silicon improves slip characteristics.

Typical mechanical properties in T5 condition:

  • tensile strength: 160 MPa;
  • yield point: 75 MPa;
  • relative extension: 10 %;
  • hardness: 45 NV;
  • Poisson's ratio: 0,33;
  • elastic modulus: 71,0 GPa.

Physical properties:

  • density: 2,880 g / cm3;
  • liquidus temperature: 650 ºS;
  • solidus temperature: 225 oC.

Technological properties:

  • melting point: from 650 to 730 ºS;
  • temperature spills: from 650 to 705 ºS;
  • aging temperature: 230 oC, excerpt - 8 hours.

Sources:

Aluminum and Aluminum Alloys, ASM International, 1996

Aluminum Alloy Castings: Properties, Processes And Applications – J. Gilbert Kaufman, Elwin L. Rooy