Extra-thick sheet submerged-arc welding technique

Abstract

The present invention discloses an extra-thick sheet submerged-arc welding technique. The technique comprises the following technological parameters and steps: 1) connector preparation: X-type beveled edges are adopted by extra-thick sheets; 2) preheating: first heating a back side of an extra-thick sheet and then a front side of the extra-thick sheet, a preheating temperature being 150 DEG C to 160 DEG C, and a heating rate being not higher than 105 DEG/h; 3) backing welding: after preheating, using flux-cored wire gas shield welding for backing welding for two paths to form two layers, and using submerged-arc welding to fill at least two paths to form one layer, maintaining interlayer temperature to be not higher than 230 DEG C; 4) turning over after an inter-welding deformation is not larger than 6-8 mm; 5) backside welding: after carbon gouging and back chipping, backing welding according to the step 3) after the extra-thick sheet reaches a preheating requirement according to the preheating method described in the step 2); 6) stress relief treatment; and 7) carrying out post heating treatment at 200 DEG C/2h after the welding, then slowly cooling the extra-thick sheet to be at the room temperature. With adoption of the technique provided by the present invention, rooting welding deformation is reduced, welding residual stress for subsequently filling a cover face is also reduced, and thus turn-over times in welding of the extra-thick sheet are reduced.

Description

technical field [0001] The invention belongs to the technical field of welding, in particular to a super-thick plate submerged arc welding process. Background technique [0002] The hinge lug plate of the jib bracket of the crane in the crane ship is made of super thick plate, and its width and length exceed the whole plate manufacturing range of the steel factory. Therefore, the welding of the super thick plate has become an inevitable problem in the construction of the crane ship. As the lifting capacity increases, the plate thickness of this part increases accordingly. For example, in a 3,000-ton crane ship, the plate thickness of this part reaches 180mm, and in a 4,500-ton crane ship, the plate thickness of this part exceeds 200mm, and the steel used is stronger. High, the yield strength is not less than 390Mpa. Therefore, the difficulty of welding such components in engineering lies in: [0003] 1. It is easy to deform when welding near the root, which makes it diffic...

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Problems solved by technology

[0003] 1. It is easy to deform when welding near the root, which makes it difficult to correct the deformation in subsequent welding;

[0004] 2. Due to the weight of the components during reverse welding, the shrinkage of the weld seam is hindered, resulting in cracking of the root weld bead;

[0005] 3. In order to adjust the welding deformation, it is difficult to turn over many times

[0006] At present, the main methods of welding such extra-thick plates are 1) electroslag welding or gas-electric vertical welding, but this kind of weld structure is thick, and it needs to be annealed for a long time above 600°C after welding, which is not only difficult to operate, but also consumes a lot of energy. Joints with poor dynamic load capacity

2) Submerged arc welding with root ceramic liner, although this method avoids the grinding operation after cleaning the back root, it still cannot avoid the above 3 problems

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