Heat treatment method after forging of ultra-supercritical high and medium pressure rotor steel

Abstract

The invention discloses a heat treatment method after forging of ultra-supercritical high and medium pressure rotor steel. The heat treatment after forging of ultra-supercritical high and medium pressure unit rotor steel X12CrMoWVNbN10-1-1 and Cr10.5Mo1W1NiVNbN is carried out by the steps of: step 1. austenite homogenization treatment; step 2. carrying out structural transformation when balanced structure transformation temperature is reached by air cooling; step 3. overall structure softening; and step 4. cooling in a speed limit furnace till discharging. Since the rotor steel is directly put into the furnace for austenization after being forged, the invention has the advantages of short time and good austenite effect, not only eliminates the forging stress, but realizes the homogenization of inner and outer structures of forging. The heat treatment method after forging has the advantages of simple operation, low cost and low energy consumption, and can meet the property requirement of workpieces.

Description

technical field [0001] The invention relates to a heat treatment process, in particular to a post-forging heat treatment method for ultra-supercritical high-medium pressure rotor steel. Background technique [0002] For large-section, large-tonnage ultra-supercritical and high-pressure rotor steel, the traditional post-forging heat treatment process, such as figure 1 As shown, when air cooling to 680-780°C after forging, put it into a 690°C waiting furnace, and then keep it at 690°C for 200 hours to transform the structure, and then cool it to 240°C at ≤8°C / h, and keep it fully Transformation, and then raised to 720 ° C for 22 hours to soften the overall structure, and finally furnace cooling to 180 ° C at ≤ 8 ° C / h to complete the post-forging heat treatment. [0003] The forgings processed according to the above process can ensure the machinability and cutting performance, but their grains are coarse, the attenuation coefficient of flaw detection cannot meet the require...

AI Technical Summary

Problems solved by technology

[0003] Forgings processed according to the above process can ensure machining and cutting performance, but their grains are coarse, the attenuation coefficient of flaw detection cannot meet the requirements of flaw detection, and the internal structure of "troostite-like" network or flocculation affects the performance of the workpiece.

Studies have shown that this is due to direct cooling and isothermal transformation without austenite homogenization treatment after forging, resulting in uneven grain size, large differences in internal and external components, and serious mixed crystals

Therefore, the workpiece processed by this process is difficult to pass the inspection

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