Effects of Quenching and Tempering upon the Stress Corrosion Cracking of Ferritic Steels

Abstract

It is shown that the apparent disagreements in the literature between the results of various workers who have studied the effects of quenching and tempering treatments upon the stress corrosion of C steels in a nitrate environment is due to their use of steels of different C contents. Very low C steels are made more resistant to cracking by quenching, whilst in higher C steels (> 0·1%) the opposite effect is observed as compared with the cracking responses in the annealed states. Subsequent tempering at sufficiently high temperatures increases the resistance of higher C steels but decreases the resistance of very low C materials. Whilst these effects of the C content and structure may be partly due to their effects upon mechanical and macroscopic electrochemical properties, the various trends are most readily rationalised in relation to the effects upon the nature and distribution of sites for localised corrosion.