FREE-MACHINING BISMUTH-CONTAINING STEELS Russian patent published in 2014 - IPC C22C38/60 

FIELD: metallurgy.

SUBSTANCE: proposed steel contains components in the following ratio in wt %: carbon - not over 0.16; silicon - not over 0.15; manganese - 1.2-1.68; sulfur - 0.2-0.4; phosphorus - 0.06-0.15; aluminium - not over 0.01; bismuth - 0.03-0.05 or 0.06-0.12, oxygen - 0.003-0.015, iron and admixtures making the rest. It features uniformly distributed sulphide inclusions approximating to globular and slightly deformed form and oxygen activity at transfer to casting of 20-70 ppm.

EFFECT: calibrated products feature higher machinability by cutting at required level of mechanical properties.

6 dwg, 2 tbl