GB1440351A - Decarburisation of chromium containing iron cobalt or nickel based alloys - Google Patents

Abstract

1440351 Decarburizing Fe, Co or Ni base alloys UDDEHOLMS AB 5 Oct 1973 [16 Oct 1972] 46645/73 Heading C7D [Also in Division F4] Iron, cobalt or nickel based alloys containing at least 10% chromium (e.g. stainless steel) are decarburized by introducing into the molten alloy a mixture of oxygen, steam and/or ammonia through the innermost section 2 of a tuyere 1 comprising at least two coaxial tubes to produce an endothermic reaction in the melt while introducing a gas which undergoes an exothermic reaction with the melt through the outermost section 3 of the tuyere. The exothermic gas may comprise oxygen, steam, argon and nitrogen and may constitute not more than 20% of the total gas flow through the tuyere which gas flow may enter the melt at a flowrate of 0.5 to 5 standard cubic metres per metric ton per minute. The tuyere may contain 3 or more coaxial tubes such that oxygen and ammonia are injected through the separate inner sections and the exothermic gas mixture is injected through the outer sections. The tuyeres may be made of copper, carbon steel or stainless steel and may have a constriction 7 in its cross-section such that a pressure sensing device on at least one of the gas feed lines will indicate a pressure variation when the tuyere has been corroded as far as the constriction.