In-situ observation of the precipitation of manganese sulfide in low-carbon magnesium-killed steel

Abstract

The in-situ observation of MnS precipitation was made on cooling using a confocal laser microscope. It was found that two types of precipitates appeared at the different temperatures. The first type precipitated at the nucleation sites of MgO or MnO-TiOx inclusions in ␥ -Fe in the temperature range between 1500 and 1200 K. The shape was triangular or rodlike, and the size was between 1 and 5 m. The second type of MnS drastically precipitated in ␣ -Fe at 1100 K just after the Ar 3 transformation. The shape was triangular or polygonal, and the size was between 0.1 and 0.5 m, much smaller than that of the first type. No significant precipitation was observed in the intermediate temperature range between 1200 and 1100 K. The reasons why MnS precipitation took place twice at the different temperature ranges and why no precipitation occurred between the two temperature ranges were discussed from the thermodynamic and kinetic viewpoints. The diffusion coefficients of Mn in ␥ -and ␣ -Fe and the supercooling are the key factors which explain the reason.

Morphology Control of Copper Sulfide in Strip Casting of Low Carbon Steel

“…In the combination of the result obtained from the present study and in the literature, [1][2][3][4][5][6][7][8][14][15][16][17][18][19][31][32][33]39,40) we can summarize the formation sequence of oxide and sulfide (including manganese and copper containing system) during cooling processes in view point of cooling rate and steel chemistry as shown in Fig. 14 and Table 3.…”

“…Recently, Furuhara 31) confirmed this semi-coherent relationship between MnS and g-Fe phase in austenite stainless steel by High Resolution TEM observation. Kimura 32) and Yamamoto 33) observed the precipitation and growth of plate-like MnS in g-Fe over a certain temperature range by the Confocal Scanning Laser Microscope. The crystal structure and lattice parameters 34) of MnS, Cu 2Ϫx S and g-Fe are listed in Table 2.…”

Effect of Phosphorus on Sulfide Precipitation in Strip Casting Low Carbon Steel

“…Although the Mn and S product is higher than the equilibrium solubility product for all the nodes at the transformation temperature, the sulfide precipitation is usually observed only in the last zone during the = transformation even for slow cooling rate case. 8,9) By considering only the MnS precipitation in the last = transformation node, S that precipitated as MnS is 0.00048% at 1688 K and 0.00053% at 1616 K for low and high P steels, respectively. Although the amount of precipitation is similar, the precipitation temperature in the high P steel is much lower than that in the low P steel.…”

“…According to the experiment data 8) for the 0.04%C-0.21%Mn-0.012%S steel, the starting temperature for MnS precipitation from -Fe is about 1500 K. Therefore, a could be determined to be about 170. Then we could estimate the relationship between S precipitated as MnS or Cu 2 S and the cooling rate as shown in Fig.…”

<i>In-situ</i> Observation of <i>δ</i>↔<i>γ</i> Phase Transformations in Duplex Stainless Steel Containing Different Nitrogen Contents

“…8) The Confocal Scanning Laser Microscope (CLSM) has recently provided a convenient possibility of making an "insitu" observation of the phase transformation on the surface of samples at high temperatures. Since the 1990's, Yin,9,10) Kimura, 11) Phelan, 12,13) Liu, 14) Chen, 15) and other researchers [16][17][18][19][20][21][22][23] have applied the CLSM to make in situ observations of the phase transformation of steels or alloys at special heating or cooling rates. For example, Yin 10) found that the incoherent δ/γ interphase boundaries (abbreviated as IBs hereafter) were always unstable with finger-like morphology during δ→γ transformation, which developed along δ/δ grain boundaries (abbreviated as GBs hereafter) at low supercoolings and even into the δ-ferrite matrix at higher supercoolings for the transformation.…”