Cold brittleness of Cr−Mn−Si steels with an unstable austenitic structure

Conclusions

1.Type 80G8Kh3 steel, which is stable in cooling all the way to the temperature of liquid nitrogen, has a wide M_d-M_S temperature range, as the result of which deformation martensite is formed in it during dynamic bend tests in the \t-196 to +150\dgC range. As the result of alloying of 80G8Kh3 steel with up to 3% silicon the temperature of formation of deformation martensite increases to 200\dgC and, in addition, the quantity of it in the fractures of the steels increases. li]2.|Alloying with silicon has no clear influence on the grain size of the steel. Small additions of it (up to 1%) promote grain growth while more significant ones (up to 3%) cause refinement but in alloying with silicon in the investigated limits there is a significant increase in the ductile-to-brittle transition temperature.

In the whole investigated test temperature range, failure of specimens of 80G8Kh3 and 80G8Kh3S3 steels is intragranular. li]3.|The formation of deformation martensite during tests of 80G8Kh3 type unstable high-carbon steels leads to a reduction in impact strength. This appears especially strongly in the formation of the first portion of deformation martensite close to the M_d temperature. li]4.|Alloying of steels of this type with silicon intensifies the formation of \ga-martensite in them in deformation and therefore it is undesirable to add silicon to steels operating under conditions of impact-abrasive wear since this leads to a reduction in their impact strength.