Determination of the Sensitivity of Mechanical Properties and Impact Strength of Cast and Forged Steel Billets 20gml to Change the Heat Treatment Regime

The paper presents the results of research on the effect of heat treatment modes on the mechanical properties of 20GML steel blanks. The results of tests of yield strength, tensile strength and toughness at a temperature of minus 40 °C of cast and forged samples that have undergone single and double normalization with a temperature variation of exposure in the range from 870 to 960 °C. The results of studies of the microstructures of these samples are presented. It was found that repeated normalization increases the values of the impact strength of cast and forged samples over the entire range of the studied heat treatment temperatures. A coefficient is proposed showing the sensitivity of the mechanical properties of the samples to changes in the heat treatment regime and the holding temperature. It was found that double normalization makes it possible to reduce the sensitivity of cast samples to changes in the temperature of heat treatment and leads to more stable results in mechanical properties.