1. The position of the welding port of the rack should avoid the stress concentration area and facilitate welding processing.

2. The beveling of the steel structure should be processed in accordance with the provisions of the processing drawings.When the drawings are not specified, the style and size of the bevel should be selected according to these principles: to ensure the welding quality, the amount of metal filled is small, easy to operate, and the welding stress and deformation are reduced.

3. Before assembling the welded parts of the rack, the oil, paint, dirt, rust, burrs and galvanized layers on and near the welding port should be removed to reveal the metallic luster.

4. When the local gap between the welding ports of the rack is too large, efforts should be made to trim it to the specified size, and it is strictly forbidden to add fillers to the gap.

5. The welding rods, welding wires and flux used in the welding of large racks should be stored in a dry, well-ventilated place with a temperature greater than 5℃ and a relative air humidity of less than 60%.Welding electrodes for welding important parts should be stored in a special insulation tube with a temperature of 100~150℃, and can be taken as needed.

6. When the frame is welded in the group, the workpiece should be firmly padded to prevent deformation and additional stress during welding and heat treatment.

7. Except for the cold drawing ports specified in the design of the rack, the use of strong pairs is prohibited for the remaining welding ports, and the thermal expansion method is not allowed to be used to prevent additional stress from being caused.

8. In order to ensure the quality of rack welding, the welding site should be windproof, rainproof, snowproof, cold-proof, etc.

9. For welded parts that require preheating and post-welding heat treatment, tooling equipment, temperature measuring instruments and thermal insulation protective equipment for preheating and post-heating should be prepared before welding processing.

10. When welding welds on the plane, it is necessary to ensure that the longitudinal and transverse welds (especially the transverse) can shrink freely.If welding butt welds, the welding direction should point to the free end.

11. When welding the frame, first weld the welds with a large shrinkage. If there are butt welds and corner welds on the structure, the butt welds with a large shrinkage should be welded first.

12. When the frame is welded, the transverse short welds should be welded first.

13. During the welding process of the frame, the welds with greater stress are welded first to make the internal stress distribution reasonable.

14. For welded parts of the frame with large deformation, welding reinforcement bars can be used rationally according to the actual situation during welding.

15. For combined welded parts composed of multiple components, step-by-step assembly and welding should be taken, and the total combined welding processing should be carried out after correcting the deformation.

16. After the welding process of the rack is completed, the entire inner and outer surface or part of the surface of the rack should be corrected and cleaned.

17. The surface cleaning of the rack after the welding is completed should be shot peening treatment, which can better improve the fatigue strength of the rack.