Construction plan for steel structure (5)

(Ⅶ) Welding method and welding material requirements

● Temporary wind and rain-proof shelters will be erected on-site if necessary to improve the effects caused by the natural environment such as wind and rain.

● Select the appropriate welding machine, carbon arc gas planers, voltage stabilizer and welding auxiliary devices such as a drying box and heat preservation cylinder to ensure that the equipment required for welding is complete and can meet the needs of quality assurance, and the welding rod must be dried and processed before welding.

●Provide qualified welders and flaw detection engineers, all welders must be licensed to work, all butt welds must be flaw detected, and the weld grade should meet the design requirements.

●Welding method and welding material selection

According to the location of the project structure welding joints, on-site welding construction using a combination of manual welding method, welding materials according to the material of the structural steel, on-site welding using manual arc welding, welding materials: E4303 or E506 welding rod, positioning welding with manual arc welding. Priming welding with φ3.2 welding rod, filling and cover welding with φ4.0 welding rod. (If the weather is wet, electrode baking is required.) Select according to the table.

● Structure welding construction sequence

The welding construction sequence has a great influence on the welding deformation and post-welding residual stress. In order to minimize the deformation and post-welding residual stress after welding the structure, the structure welding should be symmetrically welded as much as possible, so that the structure is symmetrically and evenly distributed in the whole plane by hot spots to avoid distortion and large post-welding residual stress due to uneven heating.

●Welding order requirements

Overall principle: any member welding as far as possible according to the row of a double number of welders for symmetrical welding, in order to minimize the welding stress caused by the deformation of the member, should be applied to the entire structure node priming welding, then welding the entire structure node filler welding, and finally applied to the node cover welding, so that each layer of stress has a free release process.

Before welding, welders are required to check whether the tooling frame is effectively positioned on the structural parts, whether there are conformal devices at both ends of the structure, and to do all the preparatory work before welding such as windproof, rainproof and heat preservation, etc. During the welding process, a welding method is used as much as possible to reduce the additional welding stress caused by different welding energy.

●Welding seam quality inspection requirements:

The butt weld between the beam-column and beam on the second floor of this project is a secondary weld, and 20% ultrasonic nondestructive flaw detection is carried out 24 hours after the weld is completed, and the assessment level is Ⅲ. Other parts of the welds are fillet welds and three-stage welds. No flaw detection test.

●Welding process evaluation requirements

①Welding process evaluation according to the "Code of Construction Quality Acceptance of Steel Structure Engineering", according to the "Construction Steel Structure Welding Regulations", technical requirements of the construction drawings.

② welding process assessment should be based on the node form of the steel structure project before the corresponding welding process assessment guide, used to guide the welding process assessment test (welding process assessment test has been done, after the confirmation of the engineering supervision can be exempted or replaced). After the welding process evaluation test is passed by several tests or test evaluations, the company's testing center will issue a welding process evaluation report according to the test results.

③Before the welding process evaluation, the competent welding engineer shall prepare the welding process evaluation test program according to the content in the "Welding Regulations for Building Steel Structures" and combined with the structural characteristics and node forms of the products.

④Welding process evaluation test program proposed by the competent welding engineer, the owner or the supervisor countersigned the implementation.

⑤ Construction unit according to the welding process evaluation report, the preparation of welding process guidance for guiding the welding of products.