Abstract
Phosphorus is undesirable in steel for it greatly decreases ductility and causes embrittlement in most cases. The kinetic behavior of phosphorus transfer was investigated during electroslag remelting (ESR) of G20CrNi2Mo bearing steel. Four heat treatments were carried out using an industrial furnace with a capacity to refine 2400 kg ingot. It was found the P content in the four ingots were all higher than that in the electrodes, indicating rephosphorization occurs during ESR. A kinetic model based on film and penetration theory was developed to elucidate the variation of phosphorus from metal film to droplet and metal pool. The model indicates that the rate-determining step of phosphorus transfer is at the slag side. Rephosphorization mainly occurs in the metal film and falling droplet. In addition, the effect of P in the slag and electrode, as well as the temperature of the slag pool on the P content in the metal pool were discussed. In order to achieve a low-P ingot of no more than 0.015%, the corresponding maximum P content in slag under the condition of a certain P content in the electrode was proposed.
Highlights
G20CrNi2Mo is one of the typical carburized bearing steels, widely used in the bearings of heavy-duty locomotives in China due to its good surface hardness, high contact fatigue strength, and mechanical properties [1]
Carburized bearing steel G20CrNi2Mo with Fe-0.20C-0.32Si-0.60Mn-0.50 Cr-1.80Ni-0.25Mo in Carburized bearing steel G20CrNi2Mo with Fe-0.20C-0.32Si-0.60Mn-0.50 Cr-1.80Ni-0.25Mo in mass percent was produced by the process of 70-ton electric arc furnace (EAF) melting → 70-ton ladle mass percent was produced by the process of 70-ton electric arc furnace (EAF) melting → 70-ton furnace (LF) refining → 70-ton vacuum degassing (VD) refining → continuous casting
With slag increasing from 0.0090% (slag A), the model predicts that the P content increases from 0.011% in the electrode to 0.012% in the metal film
Summary
G20CrNi2Mo is one of the typical carburized bearing steels, widely used in the bearings of heavy-duty locomotives in China due to its good surface hardness, high contact fatigue strength, and mechanical properties [1]. Removal of phosphorus is thermodynamically favored at relatively low temperature, high oxygen potential, and high slag basicity [8]. These conditions are not applicable during electroslag remelting of bearing steel. The various slag-metal interfaces during ESR make the mass transfer behavior during ESR make the mass transfer behavior of phosphorus become more complicated. A kinetic basis of on mass was developed to elucidate thetovariation phosphorus from electrode model thetransfer basis oftheory mass transfer theory was developed elucidateofthe variation of phosphorus tip to droplet and metal pool. This practice is expected to provide some guidance for commercial from electrode tip to droplet and metal pool This practice is expected to provide some guidance ESR for production low-phosphorus steel.
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