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A method for grain refinement of martensitic heat-resistant steel large-diameter thick-walled tube

A grain refining, heat-resistant steel technology, applied in heat treatment furnaces, heat treatment equipment, furnaces, etc., can solve problems such as coarse grains or mixed grains, uneven radial structure and performance of finished pipes, and achieve performance uniformity. Improve, radial grain size uniformity is good, improve the effect of grain uniformity

Active Publication Date: 2020-05-26
CENT IRON & STEEL RES INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0007] G115 steel is a new type of martensitic heat-resistant steel. The heat treatment process not only needs to consider the influence of martensitic transformation, but also because of the thick wall thickness (60-150mm), the influence of size factors must be considered, otherwise coarse grains or Mixed crystals lead to uneven radial structure and performance of the finished tube, which poses great challenges to subsequent manufacturing and welding

Method used

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  • A method for grain refinement of martensitic heat-resistant steel large-diameter thick-walled tube
  • A method for grain refinement of martensitic heat-resistant steel large-diameter thick-walled tube
  • A method for grain refinement of martensitic heat-resistant steel large-diameter thick-walled tube

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Embodiment 1

[0027] In the present invention, the pipe blank after hot extrusion of G115 martensitic heat-resistant steel, with a wall thickness of 150mm, is austenitized at 980°C before normalizing + tempering heat treatment, precooled to 745°C and kept for 75 hours, and then Furnace cools. Reheat to 1040°C, holding time 3 hours, water cooling; then proceed to 780°C, holding time 6 hours, air cooling. It not only refines the coarse grains of the G115 large-diameter thick-walled finished tube, but also improves the uniformity of the grains at different wall thickness positions, thus improving the uniformity of the radial structure and performance of the thick-walled tube.

Embodiment 2

[0029] In the present invention, the pipe blank after hot extrusion of G115 martensitic heat-resistant steel, with a wall thickness of 60mm, is austenitized at 930°C before normalizing + tempering heat treatment, precooled to 730°C for 60 hours, and then Furnace cools. Reheat to 1080°C, holding time 1.5 hours, water cooling; then proceed to 780°C, holding time 3 hours, air cooling. It not only refines the coarse grains of the G115 large-diameter thick-walled finished tube, but also improves the uniformity of the grains at different wall thickness positions, thus improving the uniformity of the radial structure and performance of the thick-walled tube.

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Abstract

The invention provides a grain refining method of a large-caliber thick-walled tube of martensite heat-resistant steel and belongs to the field of steel materials. The method adopts a tube blank and comprises the following steps: keeping the austenitizing temperature of 930-980 DEG C for 1-6h, performing furnace cooling to 740+ / -10 DEG C, keeping the temperature for 60-100h, and then, performing furnace cooling to 200 DEG C or lower; keeping the normalizing temperature of 1030-1080 DEG C for 1.5-5h, and performing water cooling to 200 DEG C or lower; and keeping the tempering temperature of 780+ / -10 DEG C for 3-6h, and performing air cooling to room temperature. The method has the advantages that from the viewpoint of eliminating the structure heredity, before normalizing and tempering heat treatment, the tube blank is firstly subjected to austenitizing treatment and then subjected to isothermal annealing; structure characteristics include ferrites, carbides and a small amount of Lavesphases, so that the structure heredity is eliminated in subsequent normalizing and reheating processes; and grains are refined, and the grains are relatively more uniform in different wall thicknesspositions, thereby improving the radial structure and performance uniformity.

Description

technical field [0001] The invention belongs to the field of iron and steel materials, and relates to a method for refining grains of large-diameter thick-walled pipes of martensitic heat-resistant steel, which is especially suitable for thick-walled pipes related to power station boilers. Background technique [0002] Improving the steam parameters (temperature and pressure) of the unit is the most important measure to improve the thermal efficiency of the unit and realize coal saving and emission reduction. [0003] Heat-resistant materials are the main "bottleneck" problem that restricts the development of thermal power units to higher parameters. Research and practice have shown that P92 martensitic heat-resistant steel can be used in the manufacture of some large-diameter boiler tubes below 628 °C steam temperature. When the steam temperature exceeds 628°C, heat-resistant materials with higher strength must be selected. Patent ZL 201210574445.1 "Steel for ultra-superc...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/28C21D1/18C21D9/08C21D6/00C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/52C22C38/54
CPCC21D1/18C21D1/28C21D6/004C21D6/005C21D6/008C21D9/08C21D2211/004C21D2211/005C21D2211/008C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/52C22C38/54
Inventor 刘正东陈正宗徐松乾包汉生赵海平刘春海李连贵刘震杨钢
Owner CENT IRON & STEEL RES INST
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