ВИЗНАЧЕННЯ ВПЛИВУ МАТЕРІАЛУ ТА ХІМІКО-ТЕРМІЧНОЇ ОБРОБКИ НА ЗНОСОСТІЙКІСТЬ ЕЛЕМЕНТІВ УНІВЕРСАЛЬНО-ЗБІРНИХ ПЕРЕНАЛАГОДЖУВАНИХ ШТАМПІВ

Abstract

The article presents the results of experimental studies of the wear resistance of metals in order to select the most effective for the manufacture of guide elements of prefabricated universal readjusted stamps. To determine the effect of the material and chemical-heat treatment of them on the wear resistance of the guide elements, the optimal friction pair was selected and tested under conditions similar to the operating conditions of the stamps. Specimens for testing were made in the form of cuts of steel 20, 12ХНЗА (12HNZA), 40Х (40Н) and 38ХМЮА (38HMYUA). Laboratory tests were performed on the machine MИ-1M (МI-1M) under a load of 50, 75 and 100 kgf with a contact area of 243 mm2. The amount of wear was determined by the gravimetric method of I. Kragelsky. Before testing for wear resistance, the specimens were subjected to thermal and heat-chemical treatment: Steel 20 (cementation, normalization, quenching, tempering), 12ХНЗА (12HNZA) (cementation, high tempering, quenching, tempering), 40X (40Н) (quenching, tempering, nitriding) and 38ХМЮА (38HMYUA) (quenching, vacation, nitriding). Studies of the microstructure and microhardness of the test specimens have shown that the nitriding of 38ХМЮА (38HMYUA) and 40X (40H) steel specimen reduces its wear by 1...2 µm and 2...3 µm, and the microhardness of both materials decreases by 50...100 Nm. The analysis of the wear intensity graphs on the number of cycles have shown that for all specimens there are two periods of wear (1 – running-in of rubbing surfaces, 2 – steady wear). Also, studies have shown that the surface layer of nitrated specimens on 38ХМЮА (38HMYUA) steel has a higher wear resistance and a slight tendency to seizing and hardening, providing a high resistance of the part to wear in various friction conditions. The results of testing samples under various loads have shown that the linear wear value is proportional to the change in the specific pressure value established on the basis of the conducted studies that the most effective material for the manufacture of guide elements for PURS is 38ХМЮА (38HMYUA) steel with the following thermal and heat-chemical treatment (quenching – 940 ... 950°C, tempering – 650°C and nitriding – 540°C).