Effect of Heat Treatment on the High Temperature Properties of High Manganese Heat Resisting 10M6N Type Alloys

Abstract

Effect of heat treatment on the high temperature properties of high manganese heat resisting 10M6N alloy and 10M6NB alloy (10M6N type alloy containing a small amount of boron) were examined.
Results obtained are as follows:
1) These two alloys show more intense age hardenability, more excellent creep rupture life and poorer rupture elongation, as solution temperature becomes higher. It is probably considered to be due to the fact that the finer precipitates tend to distribute. Especially, creep rupture strength in 1000 hr at 700°C of 10M6NB alloy solution treated at 1300°C, is improved up to about 30 Kg/mm², which belongs to the strongest group in Ni-Cr austenitic steels. Its rupture elongation is about 20%, and the creep rupture strength of notched specimen is higher than that of smooth specimen. That is, the high temperature strength of the alloy can be improved by this heat treatment, still keeping enough ductility.
2) Creep rupture strength becomes inferior, as the aging process proceeds in pre-aging after solution treatment. This is considered to be due to two functions; the first, carbon and nitrogen dissolved in the matrix precipitate as carbide and nitride, and so, solution strengthening becomes inferior, because of deconcentration of these two elements and the second, precipitates formed in pre-aging treatment more easily grow and coagulate in the process of creep rupture testing. Consequently this type alloys are preferred to be used as solution treatment.