Effects of Alloying Elements on Transformation Behaviour in Synthetic Weld Heat-affected Zone of Steels (V)

Effect of Ni on SH-CCT diagram for welding

Abstract

The effect of Ni on transformation behaviour in synthetic weld heat-affected zone of steel was investigated using simplified steels made of pure metals and graphite.
Ni element displaced the SH-CCT diagram for each transformation region to a longer time and to a lower reaction temperature. Each critical cooling time Cz', Cf', Cp' and Ce' obtained from SH-CCT diagram for welding increased with Ni content.
Morphologies of ferrite, pearlite and Zwischenstufengefuge (Zw) were strongly influenced by Ni. The morphology of ferrite formation was more liable to develop sideplate and needlelike ferrite than massive ferrite by the addition of Ni. The fine colony pearlite and degenerate pearlite precipitated more easily than lamellar pearlite. The volume of pearlite did not decreased with Ni content. It seems that these steel did not contain other elements except C and Ni. Zw precipitated easily in long cooling time.
The effect of Ni on the hardness of martensite was a little. Ni element rasied the hardenability curves in synthetic weld heat-affected zone of steels.