Structure and properties of Kh16N6 (ÉP288) steel

Summary

• 1. The properties of Kh16N6 steel after heat treatment depend on the initial magnetizability, which characterizes the relationship between the austenite and martensite in cast steel and which determines the position of the temperature region of martensitic transformation.

• 2. After quenching in air from 1050\dgC, the steel contains about 40% martensite; steels with a high magnetizability have an ultimate strength 20\2-30 kg/mm² above that of the steel with a low magnetizability.

  The mechanical properties of quenched steel depend on the rate of elongation of samples during the test because of the formation of different amounts of martensite at different elongation rates.

• 3. The strengthening of the steel as the result of treatment at subzero temperature, leading to the formation of about 90% manensite. Increases the yield strength to 105\2-115 kg/mm², depending on the initial magnetizability.

  One of the factors determining the mechanical properties at high temperatures is the initial magnetizability. The highest mechanical characteristics are found in the steel with a magnetizability of 15 mV.

• 4. To obtain the highest mechanical characteristics in Kh16N6 steel, the steel must be treated after quenching at temperatures no higher than \t-50\dgC; this ensures complete transformation of austenite into martensite.

Quenching from a lower temperature decreases the mechanical characteristics because of the greater amount of undissolved carbides.