Uddeholms Aktiebolag

Lars Anders Eriksson

Karl-Erik Oberg

Mans Klas Johnsson

Mans K Johnsson

The carbon content in iron, cobalt, or nickel based alloys containing at least about 16% chromium is substantially eliminated without significant loss of chromium by blowing the alloy with oxygen to oxidize the carbon and simultaneously introducing steam or ammonia in amounts such that the partial pressure of carbon monoxide (formed by oxidation of carbon) is lower than that which corresponds to the equilibrium pressure for the carbon/chromium oxidation e.g. below 0.95 and preferably below 0.5 atmospheres.

Metallurgical process

In a process for reducing the carbon content of an iron, cobalt or nickel based alloy containing carbon and at least 10% by weight chromium by introducing into the molten alloy, through at least one inner section of a tuyere which comprises at least two concentric tubes, essentially pure steam or steam and any inert gas belonging to the group consisting of nitrogen, argon, helium, neon and xenon, blockage of gas inlet is avoided by passing a gas mixture containing between 5 and 30% by volume of gaseous oxygen through an outermost section of the tuyere.

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Hagfors, Sweden

Lars Anders Eriksson