Boron-contg. tool steels - produced by rapid solidification process, esp. melt spinning

摘要

The alloy has the general compsn. (by wt) 0.2-1.8 (pref. 0.5-1.6)%C, 0-20 (pref. 0-5)% Cr, 0-20 (pref. 0-6)% V, 0-20 (pref. 0-10)%Mo, 0-30 (pref. 0-20)% W, 0-20 (pref. 0-15)% Co, less than 2% Mn+Si+Ni, balance Fe and impurities, with the addn. of 0.1-1.5 (pref. 0.2-1)%B. The alloy is prepd. by rapid solidification and has a single phase body centred cubic structure. Heat treatment may be carried out to form a uniform dispersion of ultrafine metallic carbides and borides in a fine-grained iron-rich matrix. The alloy is esp. a high speed or lot work tool steel. The boron addn. enhances liq. supercooling and facilitates formation of a chemically homogeneous, metastable crystalline product on rapid solidification. The fine borides, formed on heat treatment, strengthen the alloy and do not dissolve at elevated temps, giving enhanced high temp. strength. Boron addn. also promotes good yield of uniform product from melt spinning which is an economical rapid solidification process. The melt-spun filaments can be readily ground to powder which is an esp. useful form for subsequent consolidation to the transformed (ductile) final product.