THE INFLUENCE OF THERMAL PROCESSING ON THE STRUCTURE AND WEAR-RESISTANCE OF PERLITE-CLASS STEELS
From the ecological point of view, high-manganese austenitic steels of 110G13L type are undesirable in the production because of the high emission of manganese oxides to the atmosphere while melting in the electric arc furnaces, gas-oxygen cutting, and welding operations. Another disadvantage of steels of this class is their low initial hardness, which causes the revet closing capacity of the working parts of castings under the conditions of dynamic loads. Moreover, these steels are poorly machinable. The paper presents the results of the comparative study of the relationship between the structure formed in the process of heat treatment and the abrasive wear resistance of steels of two structural classes - high-manganese austenitic 110G13L steel and the 70H2GSML perlite-class steel. The wide use of 110G13L steel for the production of parts operating under the impact-abrasive wear and the repetitive contact-impact force is caused by the ability for high friction hardening of stable manganese austenite with low energy of packaging defects combined with the good impact strength. The disadvantages of 110G13L steel are the high quenching temperature, poor environmental performance and economic reasons that make it necessary in some cases to replace it with the perlite steels. The study of wear resistance of 70H2GSML perlite-class steel depending on the tempering temperature after normalization showed that this steel could be used for the casting of replaceable cast parts for crushing-milling equipment operating under the abrasive action without significant impact loads after normalization and high tempering. The wear resistance of samples made of 70H2GSML steel with the secondary sorbite structure, when testing steady abrasive, makes 55-60 % of level provided by samples of 110G13L steel, however, the lower cost, manufacturability and the environmental problems in some cases can settle the issue in favor of the application of perlite steel. The additional reserves to increase the wear resistance of 70H2GSML steel involve the quenching at high temperatures due to the formation of the structure of retained austenite that, in the process of abrasive wear, transforms into deformation martensite on the working surface increasing the steel's friction hardening ability.