In the paper superstrengthening phenomenon is discussed which is based on self- regulated thermal process taking place during transient nucleate boiling mode. Superstrengthening means additional strengthening of a material when cooling rate within the martensite range is high enough and compressive stresses are formed at the surface of steel parts. The main attention is paid to self -regulated thermal process because it allows metallurgists to optimize superstrengthening phenomenon by maximizing density of dislocations in material and making optimal condition for precipitation of fine carbides in steels and irons. The paper also discusses what kind of problem should be solved in the nearest future for applying new technologies into the practice. As a rule, the problems to be solved are connected with the cooling capacity of quenchants which should be determined correctly and standardized. For high carbon alloy steels with the low martensite start temperature Ms it is better to use two step quenching. At the first step martensite transformation is delayed and then at the second step of cooling within the martensite range process is accelerated. For low and medium carbon steels IQ-3 technology is used. The formation of compressive residual stresses can be realized by interruption process of cooling at the moment when core temperature approaches 450oC. For calculating cooling rate within the martensite range, a generalized equation is used. Mechanical properties of different steels showing superstrengthening effect are compared with the mechanical properties of materials after conventional quenching. The superstrengthening phenomenon was used in practice.
展开▼
