Steel with control austenitic transformation during operation

Abstract

The intermediate class of steels, which at room temperature belong to the ferritic state, and at operating temperature pass into the austenitic region, are called steels with control of austenitic transformation during operation. The possibility of increasing the service life of such intermediate steels at high temperatures (above the critical point A3) is shown. For the first time, the cast structure and phase-structural state of steel (grade 4Kh3N5М3F) obtained by electroslag remelting were studied. An improved composition of steel (4Kh4N5М3F) for the production of stamping tools for hot pressing of copper, copper and aluminum alloys is proposed. When setting the critical points (A1 and A3) of the investigated steel, which was confirmed by the results of high-temperature X-ray phase analysis, it was possible to optimize the heat treatment (annealing) of steel 4Kh3N5M3F and 4Kh4N5M4F2 in cast and forged condition, which facilitated processing tool. The results of researches on optimization of modes of heat treatment (hardening, tempering) of steel are given. The mechanical properties (strength, toughness, heat resistance) of steel in cast and forged state depending on the tempering and tempering temperature are determined. The tempering brittleness of the experimental steel is determined. An experimental-industrial test of a stamping tool (die dies, extruder parts) made of the investigated steel was carried out. The possibility of using stamped steel with adjustable austenitic transformation for a wide range of operating temperatures of hot deformation of aluminum alloy AK7h (450-500 ºC), copper M1 (600-630 ºC) and copper-nickel alloy MNZh 5-1 (900-950 ºC) with increased service life in comparison with steels of ferrite class 4Kh5МF1S and 3Kh3М3F. Keywords: die steel, composition, thermal treatment, structure, mechanical properties.