I. Overview
The steel framework serves as the skeleton of the entire swimming pool structure; the quality of its welding directly determines the pool's structural safety and service life. Welding the steel frame involves multiple technical stages-such as material selection, process parameter control, and deformation prevention-and requires strict adherence to relevant standards and specifications.
II. Material Preparation
Materials selected for the steel frame must meet design requirements and relevant standards. Hot-dip galvanized steel pipes (grade Q235B) are commonly used for the main framework; their outer diameter and wall thickness are determined by design calculations, with a zinc coating thickness typically no less than 85 μm. Regarding welding consumables, E4303 electrodes are generally used, with a combination of 3.2 mm and 4.0 mm diameters. High-strength bolts of grade 8.8 (friction-type) are utilized, with the torque coefficient controlled between 0.11 and 0.15.
III. Pre-welding Preparation
Technical Preparation: Before construction, a detailed specialized construction plan must be prepared, and construction personnel must be organized to familiarize themselves with the drawings, undergo design briefings, and participate in drawing reviews. A survey control network must be established, permanent reference points set, and closed-traverse surveys conducted using a total station.
Base Material Treatment: Before welding, the surface of the base material must be cleaned to remove impurities such as oil and mill scale. For welds requiring preheating, preheating and post-heating temperatures must comply with the relevant provisions of the *Code for Welding of Steel Structures* (GB 50661-2011).
IV. Welding Procedures
Tack Welding: Tack welding is performed prior to the actual welding process to ensure accurate component positioning and assembly dimensions that meet design requirements.
Welding Sequence: A rational welding sequence is crucial for controlling deformation. The sequence should generally follow the principle of "web members before chord members" and proceed symmetrically from the center outward to both sides. For large steel box girders with complex cross-sections, a composite control method combining rigid fixation and pre-deformation (counter-deformation) techniques should be adopted.
Welding Parameter Control: Taking the welding of galvanized steel plates as an example: for 1.5 mm thick plates, circumferential joints are welded continuously with the welding current controlled between 120–150 A and the welding speed at 8–10 cm/min. For CO₂ gas-shielded welding, the current is generally controlled between 180–220 A. Control of welding deformation: Deformation must be monitored throughout the welding process. A composite deformation control method-combining rigid fixturing, pre-setting (reverse deformation), and the step-back welding technique-may be employed, with constraints applied on the assembly jig to simulate actual loading conditions. For complex projects, real-time welding parameter acquisition systems may also be used for digital monitoring.
V. Post-welding inspection
Weld quality inspection is required upon completion of welding. Inspections cover weld appearance, dimensions, and the presence of defects such as cracks or porosity. Following on-site welding of the steel swimming pool, acceptance verification must be conducted in accordance with relevant standards. Inspection criteria must comply with the requirements of *Code for Welding of Steel Structures* (GB 50661-2011) and *Standard for Acceptance of Construction Quality of Steel Structures* (GB 50205-2020).
