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Technical Requirements for Welding Process
2026-05-26
1. Rules for Making Welding Procedure Documents
Workers must finish welding procedure documents before starting welding work. These documents guide on-site welding.
All welding procedure documents must include these key points:
- Welding methods, or combined welding methods
- Type, size, thickness and usage limits of base metal
- Type, size and model of filler metal
- Joint type, groove shape, size and allowed size errors
- Welding position
- Type and polarity of welding power supply
- Root cleaning work
- Welding parameters: current, voltage, travel speed, layers and weld passes
- Preheat temperature and temperature range between weld passes
- Heat treatment to remove stress after welding
- Other required rules
These documents follow official standards or qualified test results. Only approved procedures can make strong and safe welds. Welds will meet structural load needs and keep good quality. Welding without standard documents will bring safety risks to structures. All staff must follow this rule.
2. Size Rules for Single Weld Bead
This rule applies to SMAW, GMAW, FCAW and SAW welding.
For every weld bead, its depth and maximum width cannot be larger than the width of the weld surface.
The shape of weld beads greatly affects crack risks. Molten metal cools and hardens from the edge to the center of the weld. The middle part is the last to turn solid.
If weld depth is bigger than surface width, the surface will harden first. The soft hot metal in the center will shrink and form cracks. These cracks may run along the whole weld. Some cracks can be seen on the surface, and some cannot. This problem also happens to fillet welds.
3. Minimum Size of Fillet Welds
Do not include reinforcing fillet welds for groove joints.
Use the smallest standard fillet weld size if it meets design needs.
The minimum size rule keeps proper heat input during welding. It lowers crack risks on weld metal and heat-affected areas. It also matches the thickness of thin connecting parts. If the standard minimum size is larger than the design size, follow the standard size.
4. Size Limits for Single Weld Pass
This rule covers manual arc welding, semi-automatic solid wire welding, semi-automatic flux-cored wire welding and automatic submerged arc welding.
During operation, the thickness of root passes and filler passes, the size of single-pass fillet welds and the width of each weld layer shall all be kept within the specified limits.
Welding procedures approved by professional qualification are exempt from the above size limits.
These size limits make welding work easy to operate and keep weld quality stable. Welding beyond the limits will damage the inside and outside quality of welds. Workers must follow the rules strictly.
5. Operation Rules for Multi-Layer Welding
Keep working continuously for multi-layer welding.
Clean welding slag and spatter right after finishing each weld layer. Remove all defects before starting the next weld.
If welding stops halfway, use heat preservation measures. When you restart welding, set the preheat temperature higher than the first time.
6. Operation Rules for Plug Welding and Slot Welding
You can use manual arc welding, gas shielded welding or self-shielded welding for plug welding and slot welding.
For flat welding: add weld metal layer by layer. Clean all slag after each layer cools down before continuing work.
For vertical welding and overhead welding: cool and clean slag after each weld pass. Then start the next pass.
7. Forbidden Welding on Special Steel
Do not use plug welding and slot welding on quenched and tempered steel at any time.