2025-07-03    276

(I) Material Quality Requirements

(1) Welding rods, welding wires, fluxes, electroslag welding consumable nozzles, studs, welding ceramic ferrules, and shielding gases used in the construction of Xinguangzheng Steel Structure welding workshops/warehouses must possess factory quality certificates, inspection reports, and other valid quality documentation.

(2) In the construction of Xinguangzheng Steel Structure welding workshops/warehouses, the principle of matching the strength of the weld metal to the base metal is generally adopted when selecting welding materials such as welding rods, wires, and fluxes.

(3) Welding rods, fluxes, flux-cored wires, electroslag welding consumable nozzles, and ceramic ferrules for stud welding must be baked according to the product instructions and relevant welding procedures prior to use.

(II) Construction Process Quality Control

(1) When the ambient temperature for welding operations is below 0°C but not lower than -10°C, the weld joint and the surfaces within an area extending ≥ 2 times the plate thickness in all directions and ≥ 100mm from the joint must be preheated to a temperature ≥ 20°C and ≥ the specified minimum preheat temperature before welding commences. This temperature must be maintained throughout the welding process.

(2) Preheating and interpass temperature control should utilize heating methods such as electric resistance heating, flame heating, or infrared heating, measured with dedicated temperature instruments. The preheating zone should extend ≥ 1.5 times the thickness of the component at the welding point and ≥ 100mm on both sides of the weld groove. Temperature measurement points should be located:
* For non-enclosed space components: On the backside of the heated surface, ≥ 75mm away from the weld groove on each side.
* For enclosed space components: On the front side, ≥ 100mm away from the weld groove on each side.
* If the preheat temperature selected by the procedure is lower than the minimum code requirement, it must be determined through procedure qualification testing.

(3) Striking an arc on the base metal outside the weld zone is strictly prohibited. Any area within the groove where an arc is struck must be fully incorporated into the weld, leaving no arc craters. If run-on/run-off tabs or backing plates are steel, they should have a yield strength ≤ the nominal strength of the base metal being welded and possess similar weldability.

(4) Multi-pass welds must be deposited continuously. Each pass must be cleaned promptly after deposition.

(5) If design documents or contract documents require post-weld stress relief, methods such as local annealing with electric heaters or furnace annealing should be used for stress relief treatment of:
* Butt joints subject to tensile stress in fatigue calculations.
* Joints or components with dense welds.
If the sole purpose is dimensional stability, vibration stress relief may be used.

(6) When using peening to relieve stress in intermediate weld layers, use a round-nose hand peening hammer or small vibratory tools. Peening must not be performed on the root pass, the capping (final) pass, or the base metal at the edges of the weld groove.

(7) Non-destructive testing (NDT) of welds in carbon structural steel must be performed after the weld has cooled to ambient temperature. For low-alloy steel, NDT must be performed ≥ 24 hours after welding completion.

(8) Stud welds must undergo bend test sampling after welding. After bending the stud 30°, the weld and heat-affected zone (HAZ) must show no visible cracks.

(9) Repair welding must be performed continuously. If welding is interrupted, post-heating and insulation measures must be applied to prevent cracking. The number of repair attempts at the same weld location should not exceed two. After repair, the welded joint area must undergo additional magnetic particle or dye penetrant inspection.