Anti-delayed-cracking high-strength B-type sleeve fillet weld welding method

Abstract

The invention discloses an anti-delayed-cracking high-strength B-type sleeve fillet weld welding method. The method comprises the following steps, firstly, selecting a sleeve made of the same materialas a target conveying steel pipe, forming a low-strength deposited metal layer at the end part; surfacing a surfacing layer with the same strength on the surface of the conveying steel pipe, and thenthe high-strength welding material is adopted for welding fillet weld; and finally, cosmetic welding is carried out on the surface of a filling welding layer formed through filling welding, a cosmetic welding layer is formed and covers the filling welding layer. The high-strength welding materials are adopted for carrying out filling welding on fillet welds, the plastic deformation capacity of fillet welding joints is effectively improved through the excellent plasticity and toughness of low-strength welding materials, unfavorable working conditions of large stress at weak part of structure and severe environmental cooling conditions are inhibited, the delayed crack tendency is inhibited, enough joint strength is obtained through the welding materials, and the delayed crack problem of a traditional low-strength and large-wall-thickness sleeve is effectively solved.

Description

technical field [0001] The invention relates to the field of in-service welding of oil and gas pipelines, in particular to a high-strength B-type sleeve fillet weld welding method resistant to delayed cracking. Background technique [0002] Such as figure 1 As shown, the B-type sleeve is the only comprehensive repair scheme used in the local damage repair method of the oil and gas pipeline system, which can not only realize the structural strength reinforcement of the defect, but also realize the sealing of the medium transported in the pipeline. Therefore, it has been used for many years in The field of long-distance pipelines has been widely promoted and applied. According to the survey of pipeline repair cases in operation at home and abroad, tens of thousands of B-type sleeves are used. [0003] During the welding process of B-type sleeve, the pipeline is in a non-stop state, and there is a fast-flowing pressurized gas or liquid medium inside the pipeline, and a large a...

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Problems solved by technology

[0003] During the welding process of B-type sleeve, the pipeline is in a non-stop state, and there is a fast-flowing pressurized gas or liquid medium inside the pipeline, and a large amount of heat in the welding area is taken away. It is difficult to ensure the preheating temperature and interlayer welding during welding. temperature, the possibility of cracks is greatly increased; at the same time, the weld cooling rate is too fast, which will promote the formation of hardened structures sensitive to hydrogen-induced cracks in the welded joints, resulting in an increase in the hardness of the weld and the heat-affected zone (HAZ) , prone to hydrogen-induced cracking

[0004] In addition, for the repair of defects in high-grade steel pipes (X70, X80), the steel grade of the B-type sleeve currently used is relatively low (mainly Q345R steel). In order to achieve equal strength matching, the wall thickness of the sleeve is relatively large. For example, the thickness of the DN1219×18.4mm X80 sleeve is more than 45mm, and the structural stress caused by the convex deformation of the wall thickness is relatively large, such as figure 2 As shown, this has become another main factor inducing the delayed cracking of the fillet welds, which seriously hinders the selection of B-type sleeves for in-service maintenance and repair of X70 / X80 pipelines, resulting in a large amount of delay in the fillet welds after the repair of the sleeves on site. cracks, such as image 3 shown

[0005] Based on the above reasons, the present invention proposes a B-type sleeve fillet weld welding method with nearly equal wall thickness and same strength level to effectively solve the problem of delayed cracking of traditional low-strength, large-wall-thick B-type sleeves

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