Study of quench cracking of high carbon and chromium steel bar. 4th report. Repeated quenching.

Abstract

The preceding paper has reported on the numerical evaluation of quench crack susceptibility. The disadvantage of the experimental method has been the assumption of a great number of samples i.e., high cost. This paper deals with a modified method for evaluating quench crack susceptibility. Quenching was repeated n-th times until a crack was generated, using 45 test pieces. The results obtained are discussed and compared with the data presented in the preceding paper. In quench cracking of a high carbon and chromium steel bar, vertical crack value in 1/n crack generation is closely related to the crack percentage, while fin crack value slightly deviates. The residual stresses caused by repeated quench were measured by the X-ray diffraction method. The residual stresses caused by repeated quench were measured by the X-ray diffraction method. The residual stress (tensile stress) on the surface increased with repeat time. It was clarified on the basis of observations using a metallurgical microscope that the repeat of quenching should be less than 34 times.