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Prevention of surface cracking due to formation of copper alloys of tin and antimony during reheating of steel.
U S Pat 3 909 251 Sept 30 1975 :
Steels containing < / = 1 pct cu and either < / = 0.31 pct sn or 0.2 pct sb, but with < / = 0.1 pct (Sn + Sb) with 1 pct cu, or < / = 0.2 pct (Sn + Sb) with 0.5 pct Cu, can be prevented from cracking at the surface during hot working by the addition of 0.03-0.15 pct Ni and a final Si content of 0.2-1.0 pct, and the amounts required within these ranges depend on the amounts of cu, sn, and sb. Thus, with Cu 0.6, Sn 0.14, Ni approximately 0.04, and Si 0.4 pct in the steel, bronze is rejected to the grain boundaries on heating and surface cracks are formed on rolling; but this can be prevented by increasing the ni to approximately 1 pct or si to 0.8 pct; and with cu 0.4, Sn 0.28, Si 0.8, and ni 0.09 pct no bronze is separated on heating to cause hot shortness. All the steels with Sb > 0.14, Cu and Si each 0.2-1.0, and Ni 0.04-0.06 pct were subjected to Cu-Sb alloy separation and hot shortness. A theory based on the formation of fayalite in the scale from Si in the steel, and increasing solubility of Cu due to Ni, is proposed to explain the effects of Ni and Si.
U.S. Pat. 3,909,251; Sept. 30, 1975; Chem. Abstr. 84:77,741J
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Content source: National Institute for Occupational Safety and Health Education and Information Division