Effect of Zirconium on Austenitic Grain Size in Iron and Steel

Abstract

The effect of zirconium compounds on the austenitic grain size refining and grain-coarsening temperature was studied by adding ferrozirconium to the pure irons which had contained oxygen, nitrogen or carbon respectively. It was found that the grain size was refined and its coarsening temperature was enhanced by the presence of zirconium nitride or zirconium carbide; and that the nitride was more effective than the carbide, but zirconium in solid solution or in oxide gave no effect on them. The amount of zirconium nitride required for grain refining was about 0035%, but its effect was not so remarkable as that of aluminum nitride. In order to clarify the behaviour of zirconium nitride as a grain-growth inhibitor, some considerations were made on the experimental results obtained with the specimens which had been heat-treated at various temperatures.