Welding procedure specification for ABS Grade AH32 shipbuilding steel plates

1. Scope

These specifications apply to manual metal arc welding (SMAW), submerged arc welding (SAW) and CO₂ gas shielded arc welding (GMAW) of ABS Grade AH32 (ASTM A131) shipbuilding steel plates, covering butt and fillet welds in hull structures, decks, bulkheads, offshore platforms and other locations.

2. Selection of Welding Materials

AH32 has a yield strength of ≥315 MPa; welding consumables must be of equivalent or slightly higher strength and must be accompanied by certificates of approval from classification societies:

Welding consumable curing requirements: low-hydrogen electrodes 350°C × 1 - 2 h, followed by holding at 100 - 150°C; flux SJ101 250°C × 1 h, to be taken as required.

3. Pre-welding Preparation

3.1 Groove Design and Preparation

Plate thickness ≤ 6 mm: I-type groove, butt joint gap 0 - 2 mm.

Plate thickness 6 - 12 mm: V-groove, single-sided 30° - 45°, gap 2 - 3 mm, fillet 1 - 2 mm.

Plate thickness ≥12 mm: Double V-groove (X-groove), single-sided 30°, gap 2 - 4 mm, fillet 2 - 3 mm.

Groove requirements: Smooth, free from burrs, cracks and scale; misalignment ≤ 1/10 of plate thickness and ≤ 3 mm.

3.2 Surface preparation

Rust, oil, paint and scale must be removed to a metallic finish within a 20 mm radius on either side of the groove to prevent porosity and slag inclusion.

3.3 Preheating and Interpass Temperature

Ambient temperature < 5°C: Preheat the entire plate to ≥80°C.

Plate thickness ≥12 mm: Preheat to 80 - 120°C.

Plate thickness ≥40 mm: Preheat to 100 - 150°C.

Interpass temperature: 80 - 150°C; exceeding 150°C is strictly prohibited (to prevent grain coarsening).

Temperature measurement method: Surface thermocouple or temperature pen, measured 50 mm from the groove edge.

3.4 Tacking

Use E7015 (Φ3.2 mm), weld length 30 - 50 mm, spacing 200 - 300 mm, tack welds ≤ 2/3 of the design value, free from defects such as porosity and cracks.

4. Welding Parameters (Recommended Values)

4.1 Shielded Metal Arc Welding (SMAW)

Welding positions: Flat (F), Vertical (V), Horizontal (H), Overhead (O); reduce current by 10 - 15% for vertical and overhead positions.

4.2 Submerged Arc Welding (SAW)

4.3 CO₂ Gas Metal Arc Welding (GMAW)

5. Key Welding Procedures

Arc striking and extinguishing: Use arc striking and extinguishing plates, dimensions ≥100×100 mm; remove and grind flat after welding.

Welding motion: Flat position  -  straight or slight oscillation; vertical position  -  upward motion, controlling the size of the molten pool; horizontal position  -  short arc with slight oscillation to prevent undercut.

Multi-pass welding: Each weld pass shall be ≤4 mm thick; slag shall be thoroughly removed between passes to prevent slag inclusion; interpass temperature shall be strictly controlled at 80 - 150°C.

Welding sequence: Weld short seams first, then long seams; weld vertical seams first, then horizontal seams; perform symmetrical welding to minimise welding distortion and residual stress.

6. Post-welding inspection and repair

6.1 Visual Inspection

The weld bead shall be uniform in shape, free from defects such as porosity, cracks, undercut, lack of fusion and slag inclusions; the fillet dimensions shall comply with design requirements, with a fillet height of 0 - 3 mm and a width variation of ≤2 mm.

6.2 Non-Destructive Testing (NDT)

Butt welds: 100% UT (ultrasonic testing) + 20% RT (radiographic testing).

Fillet welds: 100% MT (magnetic particle testing) or PT (penetrant testing).

6.3 Repair Requirements

Defect removal: Carbon arc gouging or grinding with a grinding wheel; the removal area shall extend until the defect is completely eliminated and a metallic sheen is exposed.

Repair welding: To be carried out in accordance with the original WPS, with the preheating temperature increased by 20 - 30°C; the repaired area shall undergo NDT testing again.

7. Health and Safety

7.1 Welders must hold valid certification and wear protective face shields, welding gloves and flame-retardant workwear.

7.2 The work area must be well ventilated and equipped with fire-extinguishing equipment to prevent fire and electric shock incidents.

7.3 Welding slag and waste electrodes must be sorted and recycled to prevent environmental pollution.

8. Conclusion

The welding process for ABS Grade AH32 shipbuilding steel plates must strictly adhere to four core principles: the use of low-hydrogen welding consumables, appropriate preheating, control of interpass temperatures, and multi-pass welding. Based on classification society regulations and practical experience, these procedures may be directly applied to the preparation of shipyard WPSs and on-site construction, thereby effectively ensuring weld quality and structural safety.