A Stduy on the Heat Treatment of Cr-Mo Steel (Second Report)

Rectangular specimens and chain link plate specimens were taken from a cold rolled Cr-Mo steel plate. Various factors that affect the elongation of these specimens were investigated. These factors are as follows:1) Quenching temperature, 2) Holding time at quenching temperature, 3) Tempering temperature, 4) Coloring temperature and time.The elongation of specimen was measured by means of a jig boring machine having the precision of 10-3mm. The obtained results are summarized as follows:(1) Quenched rectangular specimen without annealing pretreatment scarcely shows any bending.(2) Quenching temperature and the holding time have the greatest effect on the change of elongation of the rectangular specimen.(3) The effect of tempering and coloring treatment on the elongation of the rectangular specimen is quite similar to that in the case of the annealed specimen, which was shown in the previous report.(4) The average value of the contraction of the rectangular specimen given by the whole tratment is 2.8×10-3mm/cm.(5) Quenching temperature has the greatest effect on the change of the elongation of the chain like plate specimen.(6) Tempering temperature is more sensitive to the elongation in this case than in the case of the rectangular specimen, and, therefore, the variation of tempering temperature must be kept as small as possible.(7) The change of the condition of coloring treatment does not show any significant effect on the elongation of the specimen.(8) Chain link plate specimen is deformed irregularly by the whole treatment.(9) The average value of the contraction of chain like plate specimen given by the whole treatment is 2×10-3mm/cm in the direction of the longest axis.