Welding as the main technology for making and connecting dust collector steel structures has been widely used in the manufacture and installation of steel structures. The so-called welding deformation refers to the deformation of the steel structure during the welding process due to the high temperature of the welding arc, and the residual deformation phenomenon in the component after welding. In these two types of deformation, the welding residual deformation is the main factor affecting the welding quality, and it is also the most destructive deformation type. The effect of welding residual deformation on the different levels of the structure is divided into overall deformation and local deformation; according to the different characteristics of deformation, it can be divided into: angular deformation, bending deformation, shrinkage deformation, distortion, wave deformation and edge deformation. Among these deformation types, the angular deformation and the wave deformation belong to the local deformation, while other types of deformation belong to the overall deformation. The more deformation type of steel structure is the overall deformation.
Precipitator welding deformation prevention and control
Welding node structure design
1 Control the number and size of welds. The number of welds in steel structures is large and the size is large. The amount of heat input during welding is also greater, resulting in greater welding distortion. Therefore, in the structural design of steel welded joints, we should try to control the number and size of welds to minimize welding distortion.
2 According to the welding process, choose the suitable weld groove shape and size. The choice of groove formation and reasonable size of the weld should ensure that the overall load carrying capacity of the steel structure is adequate. The proper shape and size of the groove can reduce the amount of welding deformation of the structure by reducing the cross-sectional area.
3 The location of the welding joint should be symmetrical to the section of the member. The position of the welded joint of the neutral axis of the structure should be as far as possible in the neutral axis symmetrical position of the structural section, or as close as possible to the neutral axis, and should be avoided in high stress areas.
4 For the choice of node form, the small rigid node form should be used. Nodes should be avoided in bi-directional and three-way intersections. This avoids high temperatures and weld stress concentration due to concentrated welds, thus reducing welding distortion.
Technological measures
1 dust collector assembly and welding sequence. The construction and assembly of the dust collector steel structure should be carried out on a standard horizontal surface. The platform should ensure that the degree of pressure on the self-weight received by the platform is large enough to prevent the steel components from destabilizing and sinking to meet the basic requirements for component assembly. In the welding of small components can be completed at once, that is, after the welding fixed position, with the appropriate welding sequence assembled. The assembly and welding of large steel structures require that the small pieces be welded first, and then the final assembly and welding. During component assembly, in order to prevent excessive stress and deformation during the assembly process, different types of parts and components should be made to meet the specification, shape and size requirements of the components, and no external forces must be used to assemble during assembly. Prevent over-welding of parts and deformation caused by large binding forces. In addition, the welding joints should be made uniform in the assembly and welding process to eliminate stress and reduce deformation; the weld joints should be of correct size for butt gap, groove angle, lap length and T-shape angle, and the form and size should be the same The design of the components is consistent with the welding specifications.
2 anti-deformation. Due to the shrinkage reaction of the weld during cooling, the result is a reduction in the size of the workpiece after welding. To solve this problem, in order to compensate for the deformation caused by thermal expansion and contraction, anti-deformation methods are commonly used in the welding of large components. The method of anti-deformation is to deform the components in advance before welding, so that the direction of deformation and the direction of welding deformation are reversed, and the magnitude of deformation is basically the same. For example, in order to prevent the welding angle deformation of the upper and lower cover plates of the I-beam, it is possible to pre-bend the plates in the opposite direction with a hydraulic press or a hemming machine before welding.
3 Weldment fixtures. It is more difficult for large pieces of bag filter structural parts to fix the position of the workpieces and parts under the action of their own weight and welding stress. Therefore, in addition to the fixed position of the welding platform for each welding workpiece and part, the welding fixture needs to be effectively clamped so as to prevent the workpiece from being deformed.