Welding method of Q690 high-strength steel pipe for truss jib of large-scale marine crane

Abstract

The present invention discloses a welding method of a Q690 high-strength steel pipe for a truss jib of a large-scale marine crane. Due to the fact that a liner of an integrated structure which is thin in two ends and fat in the middle and is approximately spinning cone shaped, and a ultralow hydrogen electrode are utilized, series of technological parameters such as backing weld and welding are reasonably selected and controlled, and technological means such as insulation treatment are carried out on the welding position after all welding is completed, welding quality of the Q690 high-strength steel pipe is largely improved, and the technical problem that during a steel pipe assembling process, fatigue-resistant performance of a welded joint is influenced due to misalignment, cold crack of the welding line, and softening and structural embrittlement of a welding heat affected zone is well solved. According to the welding method, the welding technology is simple and easy to control, welding quality is good, and the welding method is suitable for welding a Q690 high-strength steel pipe having an internal diameter of 350-800 mm for the truss jib of the large-scale marine crane.

Description

technical field [0001] The invention relates to a welding method of structural steel pipes, in particular to a welding method of Q690 high-strength steel pipes used for truss arm frames of large marine engineering cranes. Background technique [0002] The truss arms of large offshore cranes are generally welded by high-strength steel pipes, and the welding quality is very critical. In the actual use process, the truss boom is broken and damaged, often because the welding quality of the joints of the steel pipes is not good enough and there are defects. [0003] We believe that in the prior art, there are three main reasons affecting the welding quality of steel pipes for truss jib structures: [0004] One is that the out-of-roundness deviation of the main chord steel pipe is too large, which leads to a large amount of misalignment in the assembly, thereby reducing the effective structural force-bearing cross-sectional area of ​​the weld area. [0005] The second is that th...

AI Technical Summary

Problems solved by technology

[0004] First, the out-of-roundness deviation of the main chord steel pipe is too large, resulting in a large amount of misalignment in assembly, thereby reducing the effective structural force-bearing cross-sectional area of ​​the weld area

[0005] The second is that the selection of welding rods is unreasonable, resulting in excessive hydrogen content in the joints, resulting in cold cracks

[0006] The third is that there are problems in the welding method, for example, the softening zone and brittle structure are formed at the welding place, which will lead to a decrease in the strength and toughness of the material at the joint, and then make the fatigue damage resistance of the welded joint worse

The most fatal thing is that this kind of anti-fatigue damage performance is difficult to be detected by ultrasonic or ray non-destructive testing of the inside of the weld

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