A series of piston hypereutectic silumins based on Al – (15 ÷ 20) % Si alloyed with copper, magnesium, nickel, and chromium was studied. The alloys were modified with phosphorus and hydrogen-containing reagents to increase the deformability and mechanical properties. The experimental ingots, cast in the steel mold, had dimensions: diameter 190 mm, height 500-550 mm, weight 32-40 kg. The mechanical properties and temperature coefficient of linear expansion (TCLE) of the experimental ingots and forgings made from them are determined. Temporary tensile strength and relative elongation of deformed ingots from hypereutectic silumins were 227-306 MPa and 5.7-7.5%, respectively. The optimal heat treatment of deformed silumins was determined: quenching with step heating and aging, which allows the strength of forgings to be increased up to 370-470 MPa. Moreover, the ductility indicators remain at a high level, and the average TCLE of the alloys is (18.0 ÷ 19.2) ·10−6 К−1 in the range of 50 ÷ 200 °C.
The results of the influence of preliminary thermal cyclic deformation and subsequent hardening heat treatment on the microstructure and mechanical properties of hot-rolled sheet steel 10 are presented. It is shown that the use of preliminary thermal cyclic deformation of the steel 10 stock material results in a fine-grained structure of a hot-rolled sheet (3 mm thick) produced by an industrial technology. Deformation occurred at a temperature above AC3 (1250 °C), with cooling to 200-300 °C during 10 cycles and the deformation ratio per cycle being 6-8 %. Such a treatment before sheet hot-rolling allows increasing the strength characteristics (tensile strength, yield strength) by almost 30 %. It has been established that the use of subsequent heat treatment (quenching, 900 °C, water and tempering 1 h, 600 °C) leads to a further increase in strength characteristics by 15-20% while maintaining a sufficient level of ductility of sheet steel.
The results of the influence of thermocyclic forging and annealing in the range of 100 ÷ 900 °C on the microstructure, coercive force and linear expansion of steel 10. Hot cyclic forging was carried out on slabs 900×700×500 mm in size on the hydraulic press with a force of 20 MN under industrial conditions of ZSMK OJSC (Novokuznetsk). Subsequently, the billets were rolled on a 3 mm thick sheet at OAO NMZ (Novosibirsk). The use of preliminary thermocyclic deformation increases the coercive force by no more than 8%. The possibility of reducing the coercive force of sheet steel made using thermocyclic forging was shown to be almost 3 times lower than the initial untreated state due to subsequent annealing at 900 °C for 10 hours. In addition, this annealing mode reduces the average linear expansion temperature coefficient of sheet steel by 6% in the temperature range of the test 50-450 °C.
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