Temper-Brittleness: Part II- Alloy Steels

Abstract

In the case of alloy steels the modus operandi of minor elements and of phases such as nitrides.carbides, etc., in causing temper-brittleness has been experimented upon, discussed and speculated over probably more than any other alloy steels subject.The most interesting problem in this field is the suppression of temper-brittleness in nickel-chromium steels by means of molybdenum. The underlying phenomena still remain largely unresolved and no clear picture has been developed by what other elements act in the same way as molybdenum.From the discussion it emerges that temper-brittleness must be considered in terms of brittle transition temper-atures. The effects of aluminium and molybdenum, in lowering the ductile to brittle frac-ture range in alloy steels, have been outlined.It has been shown that the susceptibility ratio depends on grain size and an etchant based on solution of picric acid in ether can furnish metallograpliic evidence of temper-rittleness. Hypotheses put forward to explain temper-brittleness are stated and suggestions made for further research.