1. Common Welding Processes
Steel member fabrication commonly uses submerged arc welding, CO2 gas metal arc welding, and flux-cored or manual arc welding. Submerged arc suits long straight welds and thick-plate groove welds; gas metal arc welding is efficient for workshop batch work. The method is determined by plate thickness, groove design and welding procedure qualification (WPS/PQR).
2. Understanding Weld Types
- Full penetration welds: made through the full plate thickness, commonly used at critical butt joints transferring tension or under dynamic loading.
- Partial penetration welds: welded to a specified depth, used where calculation permits or at non-critical locations.
- Fillet welds: designed by leg size, mostly for stiffeners, gusset plates and secondary connections.
3. Weld Quality Grades and Inspection
Quality grades are commonly divided into Grade I, II and III under standards such as GB 50661. Higher grades demand more strict control: Grade I usually requires a high proportion of ultrasonic (UT) or radiographic (RT) testing, Grade II is sampled by ratio, and Grade III is mainly visual inspection; magnetic particle (MT) testing covers surface and near-surface defects.
4. How to Specify on Drawings
State the welding process, groove form, weld size, quality grade and inspection ratio in the welding notes and connection details; also record special requirements such as preheat, interpass temperature and post-weld heat treatment.
5. Controlling Quality in Production
Complete welding procedure qualification first, then produce to the qualified parameters; clean grooves and control fit-up before welding, and inspect with records after welding per the drawings.
For detailing coordination and weld marking, see our steel detailing service; if you need fabrication, send your drawings for review.