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A Process for Reducing Sensitivity to Cold Cracking of X80 Pipeline Steel Welding

A cold cracking sensitivity, pipeline steel technology, applied in welding equipment, piping systems, manufacturing tools, etc., can solve the problems of cold cracks, etc., to reduce the degree of hardening, reduce the welding strain rate, and improve the effect of crack resistance

Inactive Publication Date: 2015-12-02
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, with a groove angle of 55°, a blunt edge height of 1.2mm, and a gap of 2.5mm. The preheating temperature is set at 120℃, 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 electrode is used for root welding, and self-shielded flux-cored wire is used for filling 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, perform a partial post-weld heat treatment on the weld, first heat it to 600°C at a high temperature, and then slowly cool it to 200°C for 4 hours.

Embodiment 2

[0020] Choose to use a V-shaped groove, with a groove angle of 60°, a blunt edge height of 1.5mm, and a gap of 3mm. The preheating temperature is set at 140℃, 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 electrode is used for root welding, and self-shielded flux-cored wire is used for filling 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, perform a partial post-weld heat treatment on the weld, first heat it to 600°C at a high temperature, and then slowly cool it to 200°C for 4 hours.

Embodiment 3

[0022] Choose to use a V-shaped groove, with a groove angle of 65°, a blunt edge height of 1.5mm, and a gap of 3mm. The preheating temperature is set at 150℃, 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 electrode is used for root welding, and self-shielded flux-cored wire is used for filling 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, perform a partial post-weld heat treatment on the weld, first heat it to 600°C at a high temperature, and then slowly cool it to 200°C for 4 hours.

[0023] Refer to the GB4675.1 oblique Y-groove welding crack test method to test the crack rate of the above three cases. The...

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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 welding cold crack sensitivity of X80 pipeline steel. 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 efficiency. With the increase of natural gas transmission pressure, the steel grade of pipeline steel has also increased. X80 pipeline steel has been successfully applied on a small scale in the test section of the West-East Gas Pipeline Project, and the next step is to be widely used in the natural gas long-distance pipeline project. X80 is a kind of ultra-low carbon, microalloyed high-strength steel. It is a pipeline steel material with excellent performance and has good application prospects. However, due to the large difference in composition design and microstructure of high-grade pipeline steel compared to low-grade pipeli...

Claims

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Application Information

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Patent Type & Authority Patents(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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