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Heat treatment process capable of improving NDT performance of steel for F-grade ultrahigh-strength ocean platform

An offshore platform, ultra-high-strength technology, applied in the field of heat treatment technology, can solve the problems that have not been mentioned about the impact of NDT performance, and achieve the effects of avoiding coarse lath martensite structure, improving NDT performance, and suppressing stress concentration

Active Publication Date: 2016-04-20
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] The Q+L+T (quenching + two-phase zone quenching + tempering) process can effectively improve the low-temperature impact toughness of ultra-high-strength marine engineering steel, but its impact on NDT performance has not been mentioned yet

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] In this embodiment, a heat treatment process for improving the NDT performance of F-grade ultra-high-strength offshore platform steel adopts F-grade offshore platform steel with a plate thickness of 115 mm, which is rolled from a 420 mm thick cast slab.

[0026] This embodiment adopts the online quenching + high temperature sub-temperature quenching + tempering heat treatment process, that is, the online quenching temperature is Ac3+(80~100)°C, the final cooling temperature is ≤300°C, online ultra-fast cooling is adopted, and the average cooling rate is 20~50°C / s; high temperature sub-temperature quenching temperature is Ac3? (5~10) ℃, holding time is 1.4~1.8min / mm, using high-pressure water cooling, final cooling temperature ≤ 100 ℃, average cooling rate ≥ 20 ℃ / s; The tempering temperature is Ac1?(50~80)℃, and the holding time is 2.0~3.5min / mm. On-line quenching is carried out in the ultra-fast cooling device after rolling and completed in water cooling; high-temperat...

Embodiment 2

[0028] This embodiment is a heat treatment process for improving the NDT performance of F-grade ultra-high-strength offshore platform steel. The F-grade offshore platform steel used has a plate thickness of 115mm and is rolled from a 420mm thick cast slab.

[0029]On-line quenching + high temperature sub-temperature quenching + tempering heat treatment process is adopted, that is, the on-line quenching temperature is Ac3+(50~70) ℃, the final cooling temperature is ≤100 ℃, online ultra-fast cooling is adopted, and the average cooling rate is 15~40 ℃ / s; The high-temperature sub-temperature quenching temperature is Ac3?(10~20)℃, the holding time is 1.4-1.8min / mm, high-pressure water cooling is used, the final cooling temperature is ≤100℃, and the average cooling rate is ≥20℃ / s; the tempering temperature is Ac1?(100~150)℃, the holding time is 2.5-4.0min / mm. On-line quenching is carried out in the ultra-fast cooling device after rolling and completed in water cooling; high-temperat...

Embodiment 3

[0031] This embodiment is a heat treatment process for improving the NDT performance of F-grade ultra-high-strength offshore platform steel. The F-grade offshore platform steel used has a plate thickness of 115mm and is rolled from a 420mm thick cast slab.

[0032] Adopt online quenching + high temperature sub-temperature quenching + tempering heat treatment process, that is, the online quenching temperature is Ac3+(60~90)℃, the final cooling temperature is ≤300℃, online ultra-fast cooling is adopted, and the average cooling rate is 15~30℃ / s; The high-temperature sub-temperature quenching temperature is Ac3?(5~15)℃, the holding time is 1.5~2.0min / mm, high-pressure water cooling is used, the final cooling temperature is ≤50℃, and the average cooling rate is ≥25℃ / s; the tempering temperature is Ac1?(50~120)℃, holding time is 2.5~4.0min / mm. Quenching heating is carried out in the normalizing furnace, completed in the process of water cooling, and tempering heating is carried out ...

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Abstract

The invention discloses a heat treatment process capable of improving NDT performance of steel for an F-grade ultrahigh-strength ocean platform. The heat treatment process comprises an online quenching step, a high-temperature subcritical quenching step and a tempering heat treatment step, wherein in the online quenching step, a temperature is Ac3+(50-100) DEG C, and uniform and fine lath martensite structures are obtained; Ac3 is a temperature for completely converting ferrites to austenites during hypoeutectoid steel heating; with regard to the lath martensite structures formed by the online quenching in the invention, a small amount of undissolved ferrites is left at austenite crystals during the high-temperature subcritical quenching, and due to the existence of the ferrites, the growth of the austenite crystal grains can be effectively inhibited and a role of refining the austenite crystal grains is played; after quenching, close lath martensites, a small amount of fine ferrite structures distributed along the crystal boundaries of the austenites, and trace amounts of austenite structures left among the lamella of the martensites are obtained; during tempering, the martensite laths are softened, supersaturated carbon atoms are separated out, and the ferrite matrixes are recovered and recrystallized; and the fine lath martensite structures can still ensure a high strength after the tempering.

Description

technical field [0001] The invention relates to a heat treatment process for improving the NDT performance of F-class ultra-high-strength marine platform steel and the technical field of ultra-high-strength marine steel heat treatment. Background technique [0002] With the continuous increase of human demand for energy and the continuous consumption of onshore oil and gas resources, the importance of offshore resource development has become increasingly prominent. In order to implement the development strategy of building a powerful marine country, our country must improve the ability to develop marine resources, and will definitely speed up the development of marine oil and gas resources. [0003] The offshore platform is an important super-large welded steel structure used by humans to develop marine resources. It is responsible for carrying various oil and gas extraction equipment and providing production and living facilities for drilling, oil production, transportation...

Claims

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Application Information

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IPC IPC(8): C21D6/00C21D1/19
CPCC21D1/19C21D6/00
Inventor 张晓雪胡锋车马俊崔强
Owner NANJING IRON & STEEL CO LTD
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