Heat treatment process used after rolling of 12Cr1MoVG high-pressure steel pipe

Abstract

The invention discloses a heat treatment process used after rolling of a 12Cr1MoVG high-pressure steel pipe. The heat treatment process comprises the steps that (1), the 12Cr1MoVG high-pressure steel pipe obtained after hot rolling is subjected to heat preservation at the austenitizing temperature of 970-1020 DEG C for 60 minutes or more; (2), the steel pipe is taken out and subjected to air cooling, and the temperature is dropped to 920-980 DEG C from the initial temperature; (3), quenching is performed at the temperature of 820-850 DEG C; (4), high-temperature tempering is performed at the temperature of 720-760 DEG C, and the heat preservation time is larger than or equal to 120 minutes. The heat treatment process has the advantages that an aerial slowing-cooling process is performed before quenching and water entering, after a sufficient amount of ferrite F tissues are precipitated, water entering for rapid cooling is performed, and the problem of excessively high hardness is avoided, so that the steel type has good room-temperature machining performance, high-temperature mechanical performance and low crack sensitivity, and the pipe suitable for a high-pressure boiler is suitable for a high-temperature, high-pressure and corrosion environment.

Description

technical field [0001] The invention relates to a steam pipe used in high-pressure boiler equipment, in particular to a heat treatment process for hardness control of thick-walled 12Cr1MoVG high-pressure steel pipes. Background technique [0002] At present, my country's energy is mainly coal-fired thermal power generation. In order to improve power generation efficiency, save primary energy, and reduce carbon dioxide emissions, it will be an inevitable trend to develop units with large capacity and high parameters. There is a huge market demand for heat-resistant steel pipes, among which 12Cr1MoVG steel occupies a dominant position in unit construction and is mainly used in water-cooled walls and main steam pipes. [0003] With the improvement of boiler manufacturing technology, the safety of boiler power generation equipment depends on the ability to produce 12Cr1MoVG steel pipes that meet the hardness value required by the process. [0004] Chinese Patent Publication No...

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Problems solved by technology

[0004] Chinese Patent Publication No. CN 104017976A, the title of the invention is a heat treatment process for 12Cr1MoVG high-pressure pipe after forging, which only provides a method of heat treatment after forging, and is not suitable for the heat treatment process of quenching + tempering after rolling

[0005] According to the national standard, the quenching + tempering process is required for the wall thickness of 30mm and above. Its hardness is relatively high, and there are many problems exceeding the upper limit of hardness. At this time, if the secondary tempering process is used to reduce the hardness of the product, its production The cost will increase significantly, and if the hardness is reduced by adjusting the chemical composition, the hardness value of the pipe with a wall thickness less than 30mm will be low, which will have an adverse effect on the production organization

[0006] The steel type 12Cr1MoVG thick-walled pipe is produced by quenching + tempering heat treatment. Since the steel is low-alloy steel containing Cr, it has high hardness and high crack sensitivity after quenching, which is not conducive to room temperature processing. At the same time, it has great corrosion resistance at high temperature. big impact

Using long-time tempering heat treatment process can achieve the purpose of reducing hardness, but long-time high-temperature tempering has the problems of low production efficiency and high product cost

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