Effect of Boron on High Temperature Properties of 10M6N Type Alloys

Abstract

The effect of boron on high temperature properties of 10M6N (10%Mn, 6%Ni, 20%Cr, 2%Mo, 2.5%W, 1%Nb, 0.2%C, N>0.6%, and the balance Fe) type alloys and the proper amount of boron in view of the forgeability were examined.
Results obtained are as follows.
1) The rate of age hardening and that of the precipitation with a mode of the grain boundary reaction are delayed by the addition of boron.
The addition of boron is not effective for the improvement of the static and dynamic ductilities at room temperature, but is good for at high temperatures.
2) The improvements of creep rupture strength at 700°C, 1000hr are about 1.5kg/mm², 2kg/mm² and 2.5kg/mm² by the addition of 0.01%, 0.04% and 0.06% of boron respectively in the range of nitrogen content of about 0.5%-0.6%. These effects are mainly due to the fact that the addition of boron delays the beginning of the 3rd stage in creep of this type alloy.
3) The proper amount of boron to be added to this type alloy is about 0.01% in view of the forgeability and the resistance to oxidation.