Effect of molybdenum, aluminium and boron on the phase transformation in 4 ​wt.–% manganese steels

Abstract

The transformation behavior of medium manganese steels after forging has been characterized using dilatometry in order to investigate the influence of the alloying elements. The alloys contain 4 ​wt.–% manganese, 0.5 ​wt.–% silicon, 0.035 ​wt.–% niobium and varying amounts of carbon (0.15–0.19 ​wt.–%), aluminum (0.025–0.5 ​wt.–%), molybdenum (0.02–0.2 ​wt.–%), titanium (0–0.02 ​wt.–%), and boron (0–0.06 ​wt.–%). The continuous cooling transformation (CCT) diagrams and a multiple linear regression (MLR) formula for calculating the martensite start (Ms) temperature is presented. The results are critically compared to a variety of formulae available in the literature. It is demonstrated within this study that molybdenum increases the Ms-temperature, silicon has no mandatory influence on the Ms-temperature and boron not only decreases the Ms-temperature but also increases the critical cooling rate. The new formula enables the precise setting of annealing parameters.

Keywords

• Ms-Temperature
• Medium mananese steels
• MLR
• CCT-Diagram
• Critical cooling rate