1991 Volume 77 Issue 1 Pages 147-154
The purpose of this paper is to develop a non-destructive method for evaluating the cooling-rate (time for cooling from austenitization temperature (T) to 500°C (Ht)) generally in tempered specimens 0.4C-5Cr-Mo-V hot-work tool steel after quenching from a constant austenitization temperature within 1 0151 035°C. For this, the authors tried to employ Barkhausen Noise (BHN) signals which were induced during magnetization process. The BHN signals were measured on the surfaces of specimens, which were quenched with various T and Ht, and were tempered to adjust the hardness (H). The experimental results indicated that the total energy (Vp) of BHN signals was strongly related with microstructure which changed depending on T and Ht. These relationships could be successfully generalized as experimental expressions in the form of Ht=f(H, Vp, T). These results made it clear that non-destructive evaluation of Ht could be achieved generally by using a hybrid method combining the BHN method with an ordinary hardness test when specimens were austenitized at a constant temperature within 1 0151 035°C. The authors also confirmed the possibility of general estimation of Charpy impact values (Ch) through the generalized relationship between Ht, H, T and Ch when austenitization temperature was set at a constant temperature within 1 0151 035°C.
