Effect of sulphur content on precipitates and properties of DH36 structural steel

Abstract

In the current research, the influences of sulphur content on precipitates and properties were investigated through thermodynamic calculation and microstructural analysis. The results show that the precipitates of DH36 structural steel are mainly (Nb, Ti)C and Ti(C,N), the size of which ranged from 7 to 220 nm. Plenty of nanoscale MnS was observed by transmission electron microscopy using carbon film replicas with 0.002% S. This is because the temperatures of maximum nucleation rate and fastest precipitation of MnS are much less than soaking temperature when S content is 0.002%, which is the main reason for the formation of nanoscale MnS. What is more, the pinning effect of nanoscale MnS can also refine the grain size. Consequently, ultra-low content of sulphur can be used to optimise the properties of DH36 structural steel.

Effect of plasma preheating on weld quality and tool life during friction stir welding of DH36 steel

“…37 The base elements like Nb, Ti, V, etc., have limited solubility for ferrite and austenite phases, and dispersed precipitate contribute to high strength due to precipitation hardening. 50 The fracture of tensile specimens corresponds to the transition of the ferrite carbide aggregate region of subcritical HAZ and the base material, as shown in Figure 10(b). Figure 10(c) shows that the elongation of the welded samples is increasing with an increase in the intensity of plasma current.…”