高速度工具に關する研究 (XV)

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The effect of austempering on the subsequent tempering behavior in a high speed steel containing 0.65% C, 15.92% W, 4.30% Cr, 0.76% V and 2.64% Co was investigated by means of the microscopic examination and the hardness test. In the austempering, each specimen was quenched into a hot salt bath of a given temperature between 200℃ and 600℃ from the austenitizing temperature of 1300℃ or 1330℃, soaked there for a given period less than 5 hours, and then cooled in atmosphere. The results obtained were summarized as follows : (1) The isothermal transformation of austenite did not accur in any austempering except at the temperature range between about 250℃ and 350℃, where acicular lower-bainite was formed. (2) In general, those following austempering had different influence on the change in hardness by the subsequent tempering from the normal oil-quenching ; (i) After austempering at 600℃, the initial softening on tempering at 300°∿400℃ scarcely occured, while it was a common phenomenon after oil-quenching. (ii) After austempering at the bainiterang, which decreased the hardness at room temperature, a large amount of secondary hardening took place and consequently the maximum tempering hardness became the same with that after oil-quenching.
社団法人日本鉄鋼協会の論文
1953-06-25