日本金属学会誌

J. Japan Inst. Metals, Vol. 21, No. 4 (1957),
pp. 203-206

Hot-Bath Quenching at Low Temperatures in Eutectoid Carbon Steel (2nd Report). On the Relation between Toughness and Structural Constituents

Itsurô Tatsukawa


Abstract:

In this article, slow bending test, hardness test and dilatometric examination as well as magnetic analysis were carried out on 0.8%C steel wires variously hot-bath quenched at temperatures both above and below the Ms temperature, through which the relationship between the toughness and the structural constituents were discussed. The shapes of the curves of the absorbed energy for fracture in bending test against the holding time in isothermal treatment at every temperature are similar in general whether the soaking temperature is above or below the Ms point ; that is, every curve has a maximum value at the soaking time when the structure of the specimen consists of lower-bainite, tempered martensite and a lot of retained austenite, the last one causing improved toughness. Furthermore, from these results, it is found that retained austenite decreases yielding stress, and also superior toughness with high hardness is obtained even by certain hot-bath quenching in martensitizing range similarly as by austempering in lower-bainitizing range compared with the case by ordinary oil-quenching and tempering.


(Received 1956/9/27)

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