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

Abstract

The effect of phosphorus addition on sulfide precipitation for strip casting low carbon steel containing copper was investigated and discussed with respect to the morphology, size, and composition of sulfide. Both experimental results and mathematical calculation showed that the addition of phosphorus retards the sulfide precipitation at high temperature, promotes the supersaturation of sulfur, and produces more copper bearings and smaller sulfides at low temperature. Phosphorus also promotes sulfide precipitation in -Fe instead of in -Fe, so that small spherical copper sulfides form at a high cooling rate instead of plate-like shaped copper sulfides.

"In-situ" Observation of the .DELTA./.GAMMA. Phase Transformation on the Surface of Low Carbon Steel Containing Phosphorus at Various Cooling Rates

“…Both the starting and finishing temperatures of the MPS are higher than those of the LPS sample, which are caused by the increase in the T A3 temperature that occurred by the phosphorous addition as analyzed by Yoshida 4,5) and Liu. 7) This becomes more apparent at the rapid cooling rate as shown in Fig. 10. …”

“…Thus, the concentration of phosphorus and sulfur in the dphase may become very high in the final stage of the d /g transformation. Yoshida 4) and Liu 7) presented a detailed discussion on the effects of phosphorus on the d /g transformation and the g /a transformation based on the phase diagram and thermodynamic calculation. In brief, phosphorus could greatly reduce the T A4 temperature and increase the T A3 temperature under the equilibrium condition.…”

“…7,19) The parameters for the calculations are listed in Table 3. [20][21][22][23][24] The solutes concentrations in the d and g phases are assumed to be in equilibrium at the d/g interface.…”

“…Phosphorus, which is usually considered to be an impurity in steel, has been reported to have great effects on phase transformation and to refine the prior-austenite grain size during the solidification process. [4][5][6] Phosphorus also causes some effects on sulfide precipitation in steel, 7) such as promoting the sulfide to precipitate at a smaller size.…”

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

“…In the previous papers, 13,20,21) the authors found that copper sulfides could be formed in strip casting steel. Differently from the formerly reported copper sulfides in steel/iron, [14][15][16][17][18][19] which usually coexisted with MnS, almost pure copper sulfides were found in the present strip casting steels.…”