On the estimation of the rupture strength of highly tempered nonmartensitic transfomation products of austenitic medium alloy steels

The possibility was studied for estimating the fracture resistence of steels by the hardness tests made in a quenched and high-tempered condition. The temperature curves were obtained of hardness and notched-specimen impact bend specific energy after an isothermal hardening and high tempering. It is shown that although the general pattern of the hardness curves agrees with that of the fatigue notch specimen bend specific energy, the level of the impact bend specific energy does not agree with that of the hardness level. The comparison between steels with different hardenabilities according to quenched hardness and brittle fracture criteria in the high-tempered condition has shown that the estimate of the embrittlement effect of high-tempered products of non-martensitic austenite decomposition in middle-alloyed steels according to hardness tested in quenched or high-tempered condition is not a representative characteristic from the standpoint of cracking resistence