ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
The steel girder of the structure usually adopts box-shaped or H-shaped section in the position of high degree and large force, and the upper and lower flanges of the steel girder are butted in situ. The welding position of the neck is usually horizontal while that of the web is vertical. Considering the difficulty of back welding and the filling of weld seam in thick plate welding, if there is no special requirement, the welding position of flat welding should be adopted for both upper and lower ridges. If the steel girder is box-shaped, the butt weld of lower ridges can be welded by opening a heavenly ridge on the top or a manhole on the side of the web. 3. Unilateral V-shaped groove is commonly used for butt-joint position of steel column thick plate in field welding. Because steel column has the requirement of installation verticality, symmetrical welding should be taken into account in the welding process. For H-shaped steel columns with web and Xi Yuanjiao twins, the plate adopts double-sided groove, and the web is welded before the neck is welded. 3. On-site welding quality assurance measures 1. Welder training is closely related to the longitudinal level and the ability to perform welding process.
The raw materials and structural characteristics of each project are different. Before starting construction, even welders with valid welding certificates must carry out targeted welding training to familiarize themselves with the site working environment and the characteristics of the base metal. The quality of raw materials and welding materials for actinium structural components is the basis of on-site welding quality. Because of the large restraint stress in the welded joints of thick plate, especially in the T-shaped and Angle-connected open joints (thick vibration H-shaped open steel columns, beams, BoX box columns, beams), the phenomenon of layer tearing is particularly prominent. In addition to the requirements for steel quality grades AB, C and D, the Z-direction properties of materials are also required (resistance to tearing grade I material section yields Z15, Z25 and E35). Before on-site welding, the construction unit should carry out ultrasonic flaw detection in the range of 100mm on both sides of the weld groove. 3. Providing a better working environment for thick plate welding due to the large amount of cutting, in general, should ensure that a weld can be welded at one time to avoid stopping halfway, so the requirements of on-site welding control platform and protective shed are higher.
Special steel frame or scaffolding steel pipe is required to be installed at the welding site. The bottom of the platform is full of springboards, the upper part of the springboard is covered with fire-proof asbestos net, and the footboards are set around the welding control platform to prevent small objects from falling. In the circumference and top of the welding platform, fire-proof material is used to build protection, which requires that the top of the protective shed is impermeable, the surrounding water is impermeable, and the heat treatment process can withstand certain external loads. For the steel of Q345 grade and above, when the plate enjoys more than 30 mm, the pre-welding and post-welding heat treatment stipulated in]G]81-2002 should be strictly carried out. In the case of permissible conditions, electric heating technology should be preferentially selected for pre-weld and post-weld heat treatment. 5. The welding heat input and welding shrinkage of thick plate are larger than that of white plate with suitable welding sequence. For independent components such as individual steel columns, Xuan District vegetable uses two-person symmetrical welding to carry out post-weld sag exceeding the specification requirements. For complex truss field welding, it is required to start welding after the completion of the whole truss assembly. The overall welding sequence is declared around the truss, so as to avoid the formation of constraints around the welding.
For example, the strip truss around Shanghai Global Financial Center is welded in the welding sequence shown in Figure 3: upper chord pair.