Study of manganese sulfide precipitation in medium sulfur, non-quenched and tempered steel via experiments and thermodynamic calculation

Abstract

In this study, the precipitation behavior of MnS was calculated during the solidification process of the medium sulfur, non-quenched and tempered 49 MnVS steel. And the precipitation process was directly observed by a high-temperature confocal laser scanning microscope (HT-CLSM) equipped with a gold-image furnace. Besides, the precipitated particles were proved to be MnS by using the Scanning Electron Microscope-Energy Dispersive spectroscopy (SEM-EDS) analysis. The modified thermodynamic calculation indicated that the MnS precipitated from the residual liquid steel when the product of manganese and sulfur concentrations exceeded the equilibrium value at 1417.0 °C. Meanwhile, the results calculated by FactSage software shown that the beginning precipitation temperature of MnS is about 1411.0 °C. The observation of HT-CLSM demonstrated that the primary solid on the free surface of the liquid steel was visualized at 1485.0 °C during the solidification process (cooled from 1520.0 °C to room temperature with a rate of −30 °C/min). Then, the MnS particles started to form at 1437.0 °C and rapidly grew up into shape on the solid-liquid boundary. And the precipitation of MnS continued to form in a large amount (90% of the total) in the next 10 degrees. The enrichment of Mn and S near the local melt surface may be conducive the MnS formation, which results a higher actual precipitation temperature than the calculated value.

Revealing the morphology evolution and distribution of manganese sulphide in the 38MnS6 steel during continuous casting

“…With the growth of the matrix, manganese sulphide produced by eutectic reaction is gradually squeezed to the grain boundary, and manganese sulphide with various morphologies is finally formed under the action of crystal growth and solid-state extrusion. This process can also be confirmed in other studies [31][32][33] (Figure 11). 9.…”

Analysis of MnS Inclusions Formation in Resulphurised Steel via Modeling and Experiments

“…Cn(Δt)′=Dfalse(Cn−1(Δt)−Cn(Δt)false)Ln−1+false(Cn+1(Δt)−Cn(Δt)false)LnΔxAn where Cn(Δt)′ is real-time concentration in a time step (wt.%), D is the diffusion coefficient (cm 2 /s), Δ t and Δ x are the time step and the space step, L n is the length of the interface between node n and node n + 1 (m), while A n is the area of node n (m 2 ). In addition, MnS preferentially precipitates in the interdendritic area when the product of Mn and S concentrations exceeds the equilibrium value in remnant liquid [19]. The distribution of temperature is determined by cooling rate and assumed to be uniform.…”

“…In the present research, a new coupled model of MnS inclusions precipitation and growth during solidification was proposed based on previous work [19,20]. Using the current coupled model, the effect of cooling rate on the enrichment of solute elements and growth of MnS inclusions during solidification of a non-quenched and tempered 49MnVS steel were performed.…”

Classification of Sulfides in High‐Sulfur Steel and Establishment of Automatic Sulfide Classification Method

“…[ 5 ] Generally, even type I and type III sulfides may distribute aggregately along grain boundaries when they precipitate in the final stage of solidification. [ 19 ]…”

“…[5] Generally, even type I and type III sulfides may distribute aggregately along grain boundaries when they precipitate in the final stage of solidification. [19] Sulfides with different distribution states can be distinguished artificially, but can hardly be separately counted. All the sulfides in 2D will be considered as undifferentiated single particles by image-processing software.…”