Modelling of Manganese Sulphide Formation during Solidification, Part II: Correlation of Solidification and MnS Formation

Abstract

The high temperature properties of steels depend on the solidification parameters and the formation parameters of manganese sulphide precipitates. Therefore, the occurrence of MnS precipitations in relation to primary and secondary microstructures was studied for different steel grades with a primary delta-ferritic solidification or a primary austenitic solidification. The liquidus and solidus temperatures as well as the by-transformation temperature were calculated thermodynamically and measured by a DTA analysis in order to describe the solidification and transformation temperature range. The MnS formation temperature was calculated thermodynamically and compared to the results of SEM/EDX investigations on fracture surfaces of hot tensile specimens torn at different temperatures after in situ melting and controlled solidification. A special focus of these investigations was the location of MnS precipitates in relation to the primary and secondary grain boundaries. To explain the results, calculations were carried out taking into account the supersaturation of manganese and sulphur during the solidification in residual melt on the primary grain boundaries.

In situ characterisation of MnS precipitation in high carbon steel

“…Diederichs et al . 11,12 modified the model developed by Schwerdtfeger 9,10 by considering the concentrations of manganese and sulphur, as well as the dendrite arm spacing in medium-carbon steel.…”

Experimental Investigations and Multiscale Modeling to Study the Effect of Sulfur Content on Formability of 16MnCr5 Alloy Steel

“…[6][7][8][9] Depending on the material and post processing techniques employed the MnS inclusions transform into globular or plate like shapes. [10,11] The positive effect of adding Sulfur to steel alloys for improving the machinability, reduction in tool wear rate and improved chips flow was discovered quite early. [12] It was shown that for a constant speed and feed rate the tool life can be increased up to a factor of 10 by adding 0.4% Sulfur.…”

TEM characterization of precipitates in the segregated regions of a low‐carbon, low‐manganese, titanium‐added steel

“…During hot rolling, these manganese sulphide inclusions, which are plastic at elevated temperature, become highly elongated in the rolling direction and drastically reduce ductility and specifically impact strength in the transverse direction of rolled products. The deleterious effect of such inclusions on formability can be minimized or even eliminated by sulphide shape control (Paul & Ray, 1997) but, by contrast, these manganese sulphides can be effectively utilized to control micro‐structural development (Wakoh et al , 1996; Oikawa et al , 1997; Tsunekage & Tsubakino, 2001; Diederichs et al , 2006).…”