急熱処理した鋼の靱性におよぼす合金元素の影響

抄録

As reported previously by the authors, the hardness and toughness of steels which were heated rapidly to the optimum austenitizing temperature and quenched after holding at that temperature for a short time (“rapid heating”) were higher than those of steels which were slowly heated and quenched after holding for a longer time (“slow heating”).
In this report, to clarify the effect of alloying elements on the toughness of steels treated by “rapid heating, ” static bending test and metallographic examination in electron microscope were carried out by using low alloy steels containing C, Ni, Cr, Mo, and Si which had been treated by “rapid heating” or “slow heat ing”.
The results are summarized as follows:
1) The statical bending characteristics of the steels without Ni, Cr, and Mo treated by“slow heating” were deteriorated with increasing carbon contents in martensite matrix.
2) The statical bending characteristics of the high-carbon-nickel steels were improved by “rapid heating”, because the dissolved carbon in martensite matrix were decreased by this treatment.
3) Ni had a very small effect on the toughness of high carbon steels treated by “slow heating” but had a large effect on that treated by “rapid heating”.
4) From the above results, it was found that the carbon contents effective for the mechanical properties of steels containing Ni was below about 0.6% in martensite matrix.
5) It was clarified that high hardness and good toughness could be obtained by the combination of “rapid heating” and high carbon steel containing Ni, Cr, and Mo.