1 groove technology
The butt groove of thick plate generally adopts Y-groove with a slope of 60 degrees. First, pad the two ends of the plate at a certain angle, and the angle of the pad should be determined according to the thickness of the plate, as shown in figure 1.
Accurate selection of appropriate buffer angle is an important measure in welding anti-deformation process. Too large or too small an angle will directly affect the flatness of welded joints. The splicing interface is seamless, the padding angle on the same seam should be consistent, and automatic submerged arc welding is adopted for welding. When the front weld is completely welded, the angular deformation gradually increases with the continuous cooling and contraction of the weld, as shown in Figure 2.
2. Root cleaning and welding of reverse weld
After the front weld is welded, the back is gouged by carbon arc gouging, and the depth and width of gouging depend on the thickness of the plate. In general, the depth of planing should be greater than the depth of front weld. In the welding process of reverse weld, the high temperature of weld pool plays an annealing role, which relieves the stress of front weld. At the same time, with the continuous forming of the reverse weld, the transverse shrinkage increases during the cooling process, and the tensile stress gradually reduces the angular deformation of the front weld, and the joint tends to be straight.
3. Heat treatment after welding
Due to the existence of random factors in construction, such as welding speed, ambient temperature, materials and operation skills, the flatness of a few joints after welding will be unsatisfactory to varying degrees, and the residual deformation can be eliminated by annealing. The method is to heat the back weld center within the range of angular deformation of 20-30mm, and control the temperature at about 600 degrees.