Babbitt (metal)

Bearing metal or lead - bearing metal is an alloy of lead, tin, antimony and copper, which is used for plain bearings in particular the car bearing on the railroad. It belongs to the group of alloys of white metals.

The bearing metals have a relatively low hardness and compressive strength. Therefore, it is, if possible, interconnected in a thin layer with a supporting shell of steel or bronze.

Bearing metals are standardized in 1728 in the (old) DIN, the alloy abbreviations are led by the abbreviation Lg. So LgPbSn9Cd called an alloy with 9 % tin and 1% cadmium.

A high tin bearing metals

80 white metal (WM 80) with about 80 % tin, 5-7 % copper, 11 to 13 % antimony and 1 to 3 % of lead is low on the mechanical properties, but contains a lot of tin and is therefore expensive.

Lead- bearing metals

The lead - bearing metal has been developed to replace the much more expensive tin. In the base material lead-tin -antimony alloy harder crystals are embedded from tin-antimony caused by targeted cooling. The supporting crystals tend to separate what is to be prevented by alloying with copper.

A common bearing metal for medium load is 10 percent white metal ( WM10 ) with melting range 240 ° C to 440 ° C. It was often used in the railway, as it is easily assembled and is also easy to recycle again. In order to better inhibit the segregation, and about 1% of arsenic is added, 1% cadmium leads to higher hardness of the base material.

An addition of alkali and alkaline earth metals to a tin-free lead- matrix results eg in the case of calcium crystals from supporting Pb3Ca. The so-called Bn metal contains lead about 0.7 % of calcium, 0.6% sodium, 0.04% lithium and 0.02 % of aluminum and has a melting range from 320 ° C to 450 ° C.

Hard lead alloys

Bearing hard lead, for example, LgPbSb16 is suitable for lower hardness only for low stress.

Alloys of 5 % tin and 15 % of antimony, bismuth, graphite, and small amounts of lead, and the remainder (79%) was called Magnoliametall.