Optimal hardenability steel for any size and form of machine components to increase their service life and decrease alloy elements in material

In the paper an alloyed low hardenability steel to be used for any size and form of steel components is considered which is patented in Ukraine and can be used for providing an optimal hardened layer in product after its intensive quenching. This steel is often called as an optimal hardenability steel which provides high surface compressive residual stresses smoothly passing into smaller tensile stresses at the core of steel components. A fundamental correlation is proposed to compose chemical composition of optimal hardenability steel depending on size and form of product and grains of material’s micro – structure. By painstaking experiments, it was established that during quenching often cracks occur if chemical composition of steel is not tolerant to size and form of a product. The paper also discusses the nature of extra surface hardness (3 – 6 HRC extra units) generated by compressive residual stresses on the surface of steel parts. It is underlined the importance of establishing correlation between compressive residual stresses and extra surface hardness that can be used in the future for controlling the correctness of designed chemical composition of steel which depends on size and configuration of quenched product. A method for simulation quenching processes of large steel components in lab condition is proposed that allows correct composing chemical composition of steel depending on dimension of product, form and grain size of material’s micro – structure.