Heat treatment technique for improving low-temperature toughness of martensite-type heat-resistant steel containing large M23C6 precipitated phases

Abstract

The invention discloses a heat treatment technique for improving the low-temperature toughness of martensite-type heat-resistant steel containing large M23C6 precipitated phases. According to the heat treatment technique, the martensite-type heat-resistant steel 10Cr12Ni3Mo2VN containing the large M23C6 precipitated phases is heated to the temperature of 1070-1100 DEG C and is above the coarsening temperature of austenite grains, heat preservation is conducted for 30-45 minutes, the large M23C6 precipitated phases are eliminated quickly through high temperature heating so as to make the structure homogenized, then oil quenching or air cooling quenching is conducted; the martensite-type heat-resistant steel is heated again to the temperature of 960-990 DEG C after cooling, heat preservation is conducted for 30-45 minutes, the austenite grains are heated and refined at a low temperature, then oil quenching or air cooling quenching is conducted; and the martensite-type heat-resistant steel subjected to secondary quenching is heated again to the temperature of 670-690 DEG C and tempered for 90-120 minutes, quenched martensite is fully recovered through high-temperature quenching, and air cooling is conducted. Through the heat treatment technique secondary quenching and high-temperature tempering, the large M23C6 precipitated phases are eliminated quickly, the austenite grains are refined, and the quenched martensite is fully recovered quickly, so that the low-temperature toughness of the martensite-type heat-resistant steel containing the large M23C6 precipitated phases is improved significantly on the premise of ensuring good strength.

Description

technical field [0001] The present invention relates to heat treatment technology for iron and steel materials, in particular to a heat treatment technology for improving the low-temperature toughness of martensitic heat-resistant steel containing large-size M23C6 precipitates, and in particular to a 10Cr12Ni3Mo2VN martensitic heat-resistant steel containing large-size M23C6 precipitates Heat treatment technology to improve low temperature toughness. Background technique [0002] Martensitic heat-resistant steel has good mechanical properties, heat resistance and corrosion resistance, and has been widely used in the manufacture of steam turbine blades for ultra-supercritical units. With the development of ultra-supercritical technology, the size of steam turbine blades is getting larger and larger. Among them, the length of the last stage blade has exceeded 1 meter, the size of the final stage blade is large and the speed is high, and it is subjected to a huge impact force d...

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Problems solved by technology

In order to obtain fine austenite grains, the conventional quenching heating temperature of steel is generally below the austenite grain coarsening temperature of the steel type, such as the austenite grain coarsening temperature of 10Cr12Ni3Mo2VN steel is about 1050 ° C, so 10Cr12Ni3Mo2VN steel is in Heating and quenching at 980-1010°C to obtain fine austenite grains, but this heat treatment process does not consider the situation when large-sized M23C6 precipitates exist in the structure, and the solid solution rate of large-sized M23C6 precipitates is low. When 10Cr12Ni3Mo2VN steel When there are large-sized M23C6 precipitates, it is difficult to eliminate the large-sized M23C6 precipitates after heat treatment by conventional quenching-tempering process, and the low-temperature toughness is poor, so it is difficult to meet the standard requirements. Body-shaped heat-resistant steel forgings are usually scrapped directly, resulting in great waste. For these forgings, the low-temperature toughness can be improved by optimizing the heat treatment process to avoid scrapping

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