Influence of Si and Ni on Surface Hot-shortness of Cu-Sn Containing Steel Heated in Water Vapor Containing Atmosphere

摘要

This paper describes the influence of Si and Ni on surface hot-shortness of 0.3 percent Cu-0.04 percent Sn containing steel heated in water vapor containing atmosphere, where the atmosphere was changed in a manner of x percent H_2O-1 percent O_2-bal.N_2 (x=0, 10, 20, 30). Surface hot-shortness was assessed by measuring the surface cracking depth occurring in the 1100 deg C hot-deformed specimens after 1250 percent C heating in the water vapor atmosphere. The microstructure at the scale/steel interface was closely observed and the effect of the mass gain on surface cracking depth was investigated. For lower than 0.01% Si steel, the surface cracking depth increased largely with the mass gain, while an addition of 0.1 percent Si seems to suppress the surface cracking, especially at increased mass gains and the change with the mass gain was small. Steels with 0.14 percent Ni-Si<0.01 percent and 0.14 percent Ni-0.02 percent Si contained showed unexpectedly a marked surface cracking even in as low as 0.6 kg/m~2 mass gain of 0 percent H_2O-1 percent O_2-bal.N_2 and the surface cracking decreased considerably with an increase in the mass gain. Si and Ni were found to be favorable alloying elements for suppression of the surface hot-shortness at increased mass gains in water vapor containing atmosphere. The mechanism of the suppression was discussed in terms of the unevenness of scale/steel interface and occlusion of Cu-Sn-Ni or Cu-Sn enriched liquid alloy into the scale.