Heat treatment technology for improving ageing impact toughness of austenitic heatproof steel for preparing boiler pipes

A technology of austenitic heat-resistant steel and impact toughness is applied in the field of heat treatment process for improving the aging impact toughness of austenitic heat-resistant steel for boiler tubes, which can solve the problem of reducing the life of the tube, reducing the microstructure stability, reducing the impact toughness of the alloy, etc. problems, to achieve the effect of improving impact toughness, simple heat treatment, and maintaining stable tensile properties

Active Publication Date: 2018-01-16
XIAN THERMAL POWER RES INST CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

During the long-term aging process of HR3C alloy at 650°C, the reduction of impact toughness and structural stability of the alloy will significantly reduce the life of the pipe, and in severe cases, the pipe will burst, etc., affecting the operation safety of the power plant.

Method used

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  • Heat treatment technology for improving ageing impact toughness of austenitic heatproof steel for preparing boiler pipes
  • Heat treatment technology for improving ageing impact toughness of austenitic heatproof steel for preparing boiler pipes
  • Heat treatment technology for improving ageing impact toughness of austenitic heatproof steel for preparing boiler pipes

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Embodiment 1

[0023] The supplied HR3C alloy was subjected to high-temperature solution treatment, the solution temperature was 900°C, and the holding time was 2 minutes; then it was slowly cooled from 900°C to 600°C at a rate of 2°C / min, and finally air-cooled to room temperature. After the above heat treatment, the microstructure of the alloy is as follows: figure 2 shown, from figure 2 It can be seen that more carbides are precipitated in the HR3C alloy after optimized heat treatment, and the carbides are uniformly and continuously distributed at the grain boundaries. The room temperature and high temperature tensile properties and impact toughness of the alloy were tested. The impact specimen was a V-notch Charpy impact specimen of 55mm×10mm×2.5mm. The test results are shown in Table 2. The yield strengths at room temperature and 650°C are 425MPa and 253MPa, respectively, which are equivalent to the tensile strength of the as-supplied state; the impact energy of the HR3C alloy after ...

Embodiment 2

[0032] The as-delivered HR3C alloy was kept at 880°C for 1 minute; then slowly cooled from 880°C to 700°C at a rate of 1°C / min, and finally air-cooled to room temperature.

Embodiment 3

[0034] The as-delivered HR3C alloy was kept at 950°C for 3 minutes; then slowly cooled from 950°C to 650°C at a rate of 5°C / min, and finally air-cooled to room temperature.

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Abstract

The invention discloses a heat treatment technology for improving the ageing impact toughness of austenitic heatproof steel for preparing boiler pipes. The technology comprises the following steps: atfirst, subjecting austenitic heatproof steel to a solid solution treatment at a solid solution temperature, cooling the solid solution temperature to 600 to 700 DEG C at a speed of 1-5 DEG C / min, andfinally cooling to the room temperature, wherein the austenitic heatproof steel is HR3C alloy in a delivery state. On the premise that the tensile performance of alloy is not reduced, a simple heat treatment technology is adopted to improve the impact toughness of alloy after long time ageing, and the safety coefficient of HR3C alloy during the operation period of a power station boiler is increased.

Description

technical field [0001] The invention belongs to metal heat treatment, in particular to a heat treatment process for improving aging impact toughness of austenitic heat-resistant steel for boiler pipes. Background technique [0002] In order to improve the thermal efficiency of coal-fired generating units, reduce emissions, and protect the environment, vigorously developing ultra-supercritical power plants is one of the effective and important ways at present. At present, there are nearly a hundred 600℃ ultra-supercritical units in service at home and abroad, and austenitic stainless steel HR3C, TP347HFG, Super304H, etc. are preferred in the high-temperature superheater and high-temperature reheater sections of ultra-supercritical boilers. HR3C alloy is strengthened by multiple alloy elements such as Cr, Ni, Nb and trace elements such as C and N. High Cr can improve the alloy's resistance to high-temperature corrosion and high-temperature steam oxidation, and a large amount o...

Claims

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Application Information

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IPC IPC(8): C21D6/00C22C38/48C22C38/58C22C38/02C22C38/04
Inventor 赵新宝杨征党莹樱张醒兴鲁金涛袁勇严靖博
Owner XIAN THERMAL POWER RES INST CO LTD
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