Abstract
The targeted control of the structure and properties of high-strength alloy steels remains one of the key challenges in modern metallurgy. This study investigates the effect of solidification temperature, vibration treatment time, and the content of the complex modifier INSTEEL-7 on the hardness of 40CrNi3MoV steel. To substantiate the temperature parameters of the process, the modeling of phase transformations was performed using the Thermo-Calc software package. Experimental studies were carried out based on a multifactorial experimental design according to V.P. Malyshev's method, involving 25 experimental melts. Based on the experimental results, partial quadratic dependencies were obtained, and a generalized mathematical model was developed to describe the influence of technological factors on Vickers hardness (HV5). It was established that the steel hardness varies within the range of 356-492 HV depending on the combination of process parameters. The rational range of technological regimes was determined: a solidification temperature of 1520-1540 °C, a vibration treatment time of approximately 30 s, and an INSTEEL-7 modifier content of about 0.03 wt.%. The calculated hardness value (~487 HV) demonstrates good agreement with the experimental data, which confirms the adequacy of the developed model. The proposed approach enables the prediction of steel hardness without conducting additional full-scale experiments and can be used to optimize the technological casting parameters of high-strength alloy steels.