Bearing metal
Bearing metals are alloys made from lead , tin , antimony , copper , cadmium and arsenic that are used for plain bearings . Typical applications are the car bearings in railroad vehicles , the bearings of steam engines and other slowly rotating shafts and axles.
Alloys that contain tin and lead belong to the group of alloys of white metals . Alloys that mainly consist of tin and copper are classed as bronzes .
Many bearing metals have a comparatively low hardness , as well as tensile and compressive strength . They are therefore often connected to a support shell made of steel or bronze .
Bearing metals are standardized in the (old) DIN 1728 , the abbreviated alloy names are given by the abbreviation Lg. LgPbSn9Cd called an alloy with 9% tin and 1% cadmium .
High tin content bearing metals
White metal 80 (WM 80) with approx. 80% tin, 5 to 7% copper, 11 to 13% antimony and 1 to 3% lead has favorable mechanical properties, but contains a lot of tin and is therefore expensive.
Lead bearing metals
The lead bearing metal was developed to replace the much more expensive tin. In the base material lead-tin-antimony alloy, harder crystals of tin-antimony are embedded, which are created by targeted cooling. The support crystals tend to segregate , which should be prevented by adding copper.
A common bearing metal for medium stress is the 10 percent white metal (WM10) with a melting range of 240 ° C to 440 ° C. It was widely used on the railroad because it is easy to put together and easy to recycle. In order to better inhibit segregation , about 1% arsenic is also added, 1% cadmium leads to a higher hardness of the base material.
An addition of alkali and alkaline earth metals to a tin-free lead matrix results in z. B. in the case of calcium support crystals made of Pb3Ca. In addition to lead, the so-called Bn metal contains approx. 0.7% calcium, 0.6% sodium, 0.04% lithium and 0.02% aluminum and has a melting range of 320 ° C to 450 ° C.
Hard lead alloys
Bearing hard lead, e.g. B. LgPbSb16, is only suitable for low loads due to its lower hardness.
Alloys of 5% tin, 15% antimony, small amounts of graphite and bismuth and the remainder lead (79%) were called magnolia metal.
Highly resilient bearing metals
Bearing metals with a high load-bearing capacity often contain predominantly tin with often 12% antimony and 6% copper as alloy components, as well as other elements as so-called solid solution strengtheners . So far, bearing metals have also been mixed with lead, cadmium and arsenic for increased stresses, which are questionable due to their toxicity and should be replaced.
Individual evidence
- ↑ a b Kenan Sürül: Development of novel binding layers to improve the binding strength of tin-based plain bearing metals , 2nd technical problem, page 5th dissertation, 1st edition 2009, ISBN 3-86130-740-5 .
- ↑ Kenan Sürül: Development of novel binding layers to improve the binding strength of tin-based plain bearing metals , 2. Technical problem, page 18. Dissertation; 1st edition 2009. ISBN 3-86130-740-5 .
- ↑ Lexicon of the entire technology: bearing metals