Technology for reducing cold crack sensibility of X80 pipeline steel welding

A technology for cold crack sensitivity and pipeline steel, applied in welding equipment, pipeline systems, manufacturing tools, etc., can solve problems such as cold cracks, achieve the effects of reducing the degree of hardening, improving crack resistance, and promoting diffusion and overflow

Inactive Publication Date: 2014-02-19
HOHAI UNIV CHANGZHOU
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to provide a process for reducing the sensitivity of welding cold cracking of X80 pipeline steel, so as to solve the technical problem of cold cracking caused by poor welding process formulation in the prior art

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Choose to use a V-shaped groove, the groove angle is 55°, the height of the blunt edge is 1.2mm, and the gap between the two sides is 2.5mm. The preheating temperature is set at 120°C, the preheating width is set at 130mm, and the heat preservation time on both sides of the weld is extended to increase the heat preservation thickness. Low-hydrogen type electrodes are used for root welding, and self-shielded flux-cored wires are used for filler welding and cover welding. When performing root welding and filling welding, the current is 100A, the voltage is 18V, and the welding speed is 16cm / min. When performing cover welding, the current is 120A, the voltage is 18V, and the welding speed is 5cm / min. Immediately after the welding is completed, local post-weld heat treatment is carried out on the weld, first heated to 600°C at high temperature, then slowly cooled to 200°C and kept for 4 hours.

Embodiment 2

[0020] Choose to use a V-shaped groove, the groove angle is 60°, the height of the blunt edge is 1.5mm, and the gap between the two holes is 3mm. The preheating temperature is set at 140°C, the preheating width is set at 150mm, and the heat preservation time on both sides of the weld is extended to increase the heat preservation thickness. Low-hydrogen type electrodes are used for root welding, and self-shielded flux-cored wires are used for filler welding and cover welding. When performing root welding and filling welding, the current is 110A, the voltage is 20V, and the welding speed is 18cm / min. When performing cover welding, the current is 130A, the voltage is 20V, and the welding speed is 8cm / min. Immediately after the welding is completed, local post-weld heat treatment is carried out on the weld, first heated to 600°C at high temperature, then slowly cooled to 200°C and kept for 4 hours.

Embodiment 3

[0022] Choose to use a V-shaped groove, the groove angle is 65°, the blunt edge height is 1.5mm, and the gap between the gaps is 3mm. The preheating temperature is set at 150°C, the preheating width is set at 160mm, and the heat preservation time on both sides of the weld is extended to increase the heat preservation thickness. Low-hydrogen type electrodes are used for root welding, and self-shielded flux-cored wires are used for filler welding and cover welding. When performing root welding and filling welding, the current is 120A, the voltage is 22V, and the welding speed is 22cm / min. When performing cover welding, the current is 140A, the voltage is 22V, and the welding speed is 12cm / min. Immediately after the welding is completed, local post-weld heat treatment is carried out on the weld, first heated to 600°C at high temperature, then slowly cooled to 200°C and kept for 4 hours.

[0023] Referring to GB4675.1 oblique Y-groove welding crack test method, the above three c...

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Abstract

The invention relates to the technical field of pipeline welding, in particular to a technology for reducing cold crack sensibility of X80 pipeline steel welding. The technology includes the steps of preheating, welding and heat treatment after the welding. A high preheating temperature is adopted for slowing down cooling speed after the welding, which helps diffusible hydrogen in weld joint metal to escape, meanwhile, the quench hardening degree of weld joints and heat affected areas is reduced, and the crack resistance of a welded splice is improved. The heat treatment is performed at once after the welding, high-temperature heating is performed, then slow cooling is performed, and heat preservation is performed so that residual stress after the welding can be eliminated, and the residual hydrogen is prompted to diffuse and escape. Therefore, cold cracks caused by restraint stress and the quench hardening structure can be reduced.

Description

technical field [0001] The invention relates to the technical field of pipeline welding, in particular to a process for reducing the sensitivity to cold cracking of X80 pipeline steel welding. Background technique [0002] With the development of the petroleum industry, pipeline transportation of oil and gas has developed rapidly due to its safety, economy and high efficiency. As the pressure of natural gas transportation increases, the steel grade of pipeline steel also increases. X80 pipeline steel has been successfully applied on a small scale in the test section of the West-East Gas Transmission Branch Project, and it is planned to be widely used in the long-distance natural gas pipeline project in the next step. X80 is an ultra-low-carbon, micro-alloyed high-strength steel. It is a pipeline steel material with excellent performance and has a good application prospect. However, because high-grade pipeline steel is quite different from low-grade pipeline steel in terms o...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K9/23B23K9/235B23K9/02B23K9/00
CPCB23K9/0282B23K9/23B23K9/235B23K33/006B23K2101/10C21D9/14
Inventor 严春妍祁帅史志丹纪秀林
Owner HOHAI UNIV CHANGZHOU
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