The influence of substitutional elements on the transformability of 3CR12 steel

An investigation has been carried out on a dual-phase 12 % chromium steel, designated 3CR12, with the aim of developing its composition to improve its properties. By the addition of appropriate alloying elements, it was hoped to produce a fully austenitic structure in the rolling temperature range, and at the same time to enhance the kinetics of the decomposition of austenite so that a fully ferritic structure could be obtained after air cooling. The absence of delta ferrite during hot rolling would eliminate the highly anisotropic structure currently found in 3CR12, whilst accelerating the transformation to alpha ferrite might eliminate the need for an annealing treatment. Volume fraction analysis (VF A) of specimens quenched from a soaking temperature of 1000°C showed that Co, Ni and Cu stabilise austenite, whilst Si and Al have the opposite effect. These results were confirmed by finding the equilibrium transformation temperatures of the decomposition of austenite to ferrite using dilatometry, and by investigating the partition of alloying elements between delta ferrite and austenite at I 000°C using the electron microprobe. The effects of the alloying elements on the kinetics of the transformation were investigated by VF A of specimens transformed from 1000°C, and by the use of dilatometry. Dilatometry was used to find the slowest cooling rate at which the alloy was fully untransformed. It was found that Si and Al enhance the kinetics of transformation, whilst Co, Ni and Cu hinder them. The effect of each element is discussed with respect to three factors: the delta ferrite content prior to the transformation, the temperature range of transformation, and the thermodynamic effects of the element.

Grantor dc:publisher.institution

Centre for Materials Engineering

Year dc:date.issued

1996

Author dc:creator

• Jungbacke, Nils Gene

Advisor dc:contributor.advisor

• Knutsen, Robert D

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/9224

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/9224