A method for reducing the content of carbon and nitrogen in ferromagnetic chromium alloys

摘要

In this process, the amt. of carbon and nitrogen in powdered ferro-chromium is reduced by forming an oxide film on the surface of the alloy, followed by heating for 3-20 hrs. in H2 at 1000-1300 degrees C. The initial material pref. contains max. 0.1% C and is either pulverised mechanically to 2 mm max. size and given an oxide film is not 1 mu thick, or a molten bath is atomised to shot 0.05-1 mm size using is not 5% O2 in the atmos. and is not 1.5 ml O2/l in the water, at 20 degrees C., used for shotting and cooling, to obtain an oxide film is not 2 mu thick. The H2 should pref. be used at min. 3 1/minute and contain the lowest possible amt. of N2 with max. 5% H2O, and the final alloy should pref. contain, all maxima, 0.005% C, 0.015% nitrogen and 0.1% oxygen. The powdered alloy is used in the mfr. of stainless steel, the corrosion-resistance and toughness of which is improved by a redn. in the C and N2 content. Process uses a lower temp. and shorter time than similar, known processes which involve heating in vacuo and do not produce very low nitrogen contents.