抄録
The behavior of carbides in the tungsten steel containing 1.45%C 4.86%W during annealing and its effect on subsequent hardening were investigated by means of electrolitic isolation, and chemical and X-ray analyses of carbides. It was found that the carbide phases present in the annealed conditions varied with annealing temperature; M23C6 occured alone in the isothermally annealed specimens at 700°C, which changed partially into M6C and WC after annealing between 800° and 900°C and completely into Fe3C and WC between 1000° and 1200°C. In the commercially hardened condition, the concentration of carbon in the matrix increased progressively with increase of the annealing temperature prior to hardening, but that of tungsten decreased remarkably by the annealing between 900° and 1100°C and oil quenched hardness decreased consequently. It may be concluded that the spoiling of tungsten steel results from a lowering of hardenability due to the decrease of tungsten in the matrix by the carbide changes during annealing.
