Cast steel 4Kh4N5M4F2 for hot pressing mold of copper M1 and aluminum alloy AK7ch

 

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Kyiv
sedoroleg@ukr.net
Usp. materialozn. 2021, 2:54-62
https://doi.org/10.15407/materials2021.02.054

Abstract

The mode of quenching and tempering of the investigated 4Kh4N5M4F2 steel with controlled austenitic transformation during operation is developed. The optimal temperature regime of hardening of the investigated steel is 1100 ± 5 °С and with increasing hardening temperature (above 1100 °С) the size of austenitic grain increases and the recrystallization process is intensive, which leads to a decrease in strength. It is recommended to carry out low-temperature tempering at temperatures of 190 ± 10 °C of hardened steel to reduce internal stresses. It has been established that tempering of hardened steel is necessary by cooling in the air. The optimum temperature mode of steel tempering is 590 ± 5 °С. The analysis of the structural state of the investigated steel after hardening and tempering (isothermal holding for two and four hours) is carried out. It was established that the maximum operating temperature of the die for hot pressing of copper (grade M1) can reach up to 650 °C. It is shown that the die of the studied steel is able to work at (extreme) temperature operating conditions of 625– 650 °C. Heat resistance decrease (below 40 HRC) and softening occur in steel above the higher operating temperature (>650 °C). A pilot test was carried out on a die tool made of 4Kh4N5M4F2 steel (non-forging technology) for hot pressing of an aluminum alloy of the AK7ch grade, which showed the same service properties at the level of 4Kh5MF1S steel (grade H13, USA), which was subjected to ingot hot deformation (forging) with working surface nitride hardening to a depth of 300 microns.


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DIE STEEL, HARDNESS, HOT DEFORMATION, IMPACT STRENGTH, THERMAL TREATMENT

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