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Heat treatment process capable of improving low temperature impact toughness of 9Ni steel

A low-temperature impact toughness and process technology, which is applied in the field of heat treatment process to improve the low-temperature impact toughness of 9Ni steel, can solve the problems of small impact toughness margin and affect the safety of 9Ni steel, achieve uniform distribution, reduce strength, and improve thermal stability. sexual effect

Inactive Publication Date: 2015-07-01
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] With the rapid development of the oil and gas industry, the utilization rate of 9Ni steel has been significantly increased. Through the above-mentioned heat treatment process, the use requirements can be met, but the mechanical performance requirements of 9Ni steel, especially the low-temperature impact toughness margin is not large, which greatly affects The safety of 9Ni steel used at low temperature

Method used

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  • Heat treatment process capable of improving low temperature impact toughness of 9Ni steel
  • Heat treatment process capable of improving low temperature impact toughness of 9Ni steel
  • Heat treatment process capable of improving low temperature impact toughness of 9Ni steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] This embodiment is a manufacturing method of a heat treatment process for improving the low-temperature impact toughness of 9Ni steel. It adopts a quenching-two-phase zone quenching-tempering (QLT) process, quenching at 830-850°C, sub-temperature quenching at 635-655°C, and quenching at 560- Tempering at 600°C; Quenching heating is carried out in the normalizing furnace, completed in the process of water cooling, and tempering heating is carried out in the tempering furnace, completed in the process of air cooling. The yield strength of the 9Ni steel manufactured in this embodiment is 590-630MPa, the tensile strength is 680-720MPa, the elongation is 26.0-30.0%, and the impact energy is 200-230J. The specific process comparison is shown in Table 1:

[0020] Table 1 Mechanical properties after enlarging the QL temperature difference

[0021]

Embodiment 2

[0023] This embodiment is a manufacturing method of heat treatment process for improving the low temperature impact toughness of 9Ni steel. It adopts the quenching-quenching-tempering (QQT) process, quenching at 830-850°C, secondary quenching at 735-755°C, and tempering at 560-600°C. Fire; quenching heating is carried out in the normalizing furnace, completed in the water cooling process, and tempering heating is carried out in the tempering furnace, completed in the air cooling process. The yield strength of the 9Ni steel manufactured in this embodiment is 670-710MPa, the tensile strength is 700-740MPa, the elongation is 21.0-25.0%, and the impact energy is 180-210J. The specific process comparison is shown in Table 2:

[0024] Table 2 Mechanical properties after enlarging the QQ temperature difference

[0025]

[0026]

Embodiment 3

[0028] This example is a manufacturing method of a heat treatment process for improving the low-temperature impact toughness of 9Ni steel. It adopts the normalizing-normalizing-tempering (NNT) process, normalizing at 830-850°C, secondary normalizing at 735-755°C, and 560°C. Tempering at -600°C; normalizing heating is carried out in the normalizing furnace and completed during the air cooling process, and tempering heating is carried out in the tempering furnace and completed during the air cooling process. The yield strength of the 9Ni steel manufactured in this embodiment is 640-680MPa, the tensile strength is 670-710MPa, the elongation is 20.0-24.0%, and the impact energy is 150-180J. The specific process comparison is shown in Table 3:

[0029] Table 3 Mechanical properties after enlarging the temperature difference of NN

[0030]

[0031] Due to the adoption of the above-mentioned technical scheme, the 9Ni steel manufactured in this specific embodiment, by expanding th...

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Abstract

The invention discloses a heat treatment process capable of improving low temperature impact toughness of 9Ni steel. The heat treatment process are as follows: (a) quenching-dual-phase intercritical quenching-tempering (OLT) heat treatment process, wherein the quenching temperature is 830-850 DEG C, the intercritical quenching temperature is 635-655 DEG C and the tempering temperature is 560-600 DEG C; or (b) quenching-quenching-secondary tempering (QQT) heat treatment process, wherein the quenching temperature is 830-850 DEG C, the secondary tempering temperature is 735-755 DEG C, and the tempering temperature is 560-600 DEG C; or (c) normalizing-secondary normalizing-tempering (NNT) heat treatment process, wherein the normalizing temperature is 830-850 DEG C, the secondary normalizing temperature is 735-755 DEG C, and the tempering temperature is 560-600 DEG C; therefore, 9Ni steel with excellent low temperature impact toughness is obtained. The heat treatment process has the advantages that the low temperature impact toughness is improved greatly and the mechanical property of 9Ni steel is optimized while the strength of the 9Ni steel is reduced slightly, so that the 9Ni steel can completely meet the property requirement of large LNG storage cylinders.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of low-temperature alloy structural steel, in particular to a heat treatment process for improving the low-temperature impact toughness of 9Ni steel. Background technique [0002] 9Ni steel was first successfully developed by the product research laboratory of the American International Nickel Corporation. The alloy element Ni content is between 8.50-10.00wt%. It is a low-carbon quenched and tempered steel. 9Ni steel is the only ferritic steel that can be used under the low temperature condition of -196°C. It has high yield strength and tensile strength, excellent low temperature toughness, and good weldability. 9Ni steel is a key material used in the construction of large LNG storage tanks and related industries, and has a huge market advantage. [0003] 9Ni steel must adopt appropriate heat treatment process to improve its low temperature toughness at -196°C to a great extent. In-depth ...

Claims

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Application Information

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IPC IPC(8): C21D1/18C21D1/28C21D6/00
Inventor 胡锋尹雨群檀传淼孙超高江
Owner NANJING IRON & STEEL CO LTD
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