GB986061A - Alloys having improved machinability - Google Patents

Abstract

Iron, nickel and cobalt alloys have dispersed throughout them 0.1-1% of boron mononitride to confer improved machinability. The nitride may be added as a preformed solid to the molten alloy or boron and nitrogen may be added separately, e.g. as master alloys such as ferro-boron and nitrogenous ferro-chromium. In the latter case, the cast alloys must be heated at 1700-2300 DEG F., e.g. for 8 hours, to precipitate the nitride; it may also be necessary to carry out the melting under an atmosphere of nitrogen. Particular ranges of composition which may be treated are given as: (a) austenitic stainless steels containing .C.- 0.25% .Mn.- 8% .Si.- 3% .Cr.-26% .Ni.6-46% .Fe.balance .Nb, Ti, Mo, Cu, S, P, Se. .and excess N may also be present.. (b) Tool and die steels containing .C.- 2.5% .Mn.0.10- 3% .Si.0.10- 3% .Cr.-18% .V.- 8% .W.-20% .Mo.-10% .Co.-12% .Ni.- 3.5% .Cu.- 5% .S.- 0.25% .Fe.balance As exemplified these alloys were heated at 2050-2100 DEG F. for 8 hours, hot worked, annealed at 1550 DEG F., and cooled in the furnace at 20 DEG F./hour to 1000 DEG F. (c) ferritic stainless steels containing .C.- 0.35% .Cr.10-30% .Si.- 3% .Mn.- 1% .Al.- 4.5% .Ti.- 0.5% .Mo.- 5% .Cu.- 1.5% .Fe.balance .S, Se may also be present.. (d) martensitic stainless steels containing .C.0.03- 1.5% .Cr.4 -18% .Si.- 3% .Mn.- 2% .Ni.- 2.5% .Fe.balance .Mo, Zr, P, S, and Se. ..may also be present (e) heat resisting alloys containing .C.- 0.3% .Mn.- 3% .Si.- 2% .Cr.-30% .Mo, W.-15% in total .Ti, Al.-10% each, but not ..exceeding 15% in total .Ni,Co,Fe.balance