GB568573A - Improvements in and relating to the decarburisation of austenitic manganese steel - Google Patents

Abstract

568,573. Decarburizing manganese alloy steels: ROBIETTE, A. G. E., and BIRMINGHAM ELECTRIC FURNACES, Ltd. Feb. 27, 1943, No. 1392/42. [Classes 72 and 82 (i)] Austenitic manganese steels are decarburized by treating them at a temperature of between 700‹ C. and just below its melting point, with a gas containing 0.1-25.0 per cent of hydrogen, 4-9) of carbon dioxide, 0.1-3.0 of water vapour, 6-25 of carbon monoxide and the remainder substantially nitrogen, so as to lower the carbon content of the surface to such an extent as to produce in the regions to be subjected to wear martensite and/or a structure which is easily converted to martensite on working. If the steel contains 1.0-1.8 per cent of carbon, the carbon content of the surface in the regions to be subjected to wear is reduced to 0.05-0.5 per cent. The gas used may be produced by the controlled combustion of predetermined mixtures of air with charcoal producer gas, coal producer gas, or hydrocarbon-containing gas such as town gas or coke oven gas, or hydrocarbons such as methane, propane or butane, any undesirable constituents being removed before use. The gas may be passed into a chamber or furnace containing the steel and may be circulated by a fan, the recirculation system including means for. regenerating the desired atmosphere by adding air or other oxygen-containing gas thereto to restore the proportions of carbon monoxide and dioxide. The steel usually contains 9-20 per cent of manganese and 1.0-1.8 of carbon and part of the manganese may be replaced by nickel and/or copper to such an extent that the alloy contains a total of 10 per cent of nickel and copper and in which the manganese content does not fall below 5 per cent. The alloys may also contain up to 2.5 per cent of one or more. of vanadium, tungsten, molybdenum, chromium and aluminium, but not more than 5.0 per cent in all. Examples of such steels are (a) 8 per cent of manganese, 6 of nickel and 2 of copper, and (b) 12 of manganese and 2 of nickel. Specifications 419,057 and 564,252 are referred to.