1. Basic Material Properties

ABS Grade B is a standard-strength marine structural steel certified by the American Bureau of Shipping (ABS), suitable for non-high-strength load-bearing structures such as hulls, decks and ship’s sides. Its carbon equivalent is ≤0.36%; it has low susceptibility to cold cracking and good weldability. Preheating is generally not required, but the classification society’s welding specifications must be strictly adhered to.

1.1 Chemical Composition of ABS Grade B Shipbuilding Steel Plates (heat analysis, wt %)

1.2 Mechanical Properties of ABS Grade B Shipbuilding Steel Plates

1.3 Assessment of weldability

Carbon equivalent (CEV) (IIW): ≤0.36%

Low susceptibility to cold cracking: thin plates (≤20 mm) can be welded at room temperature; preheating is recommended for thick plates and in low-temperature environments.

2. Recommended Welding Methods and Consumables

2.1 Recommended Welding Methods

Manual arc welding (SMAW): Repair, positioning, confined spaces.

Submerged arc welding (SAW): Flat butt joints, long straight seams (high efficiency, high quality).

CO₂ gas shielded arc welding (GMAW/FCAW): Hull structures, fillet joints / butt joints (mainstream).

Tungsten inert gas welding (GTAW): Root passes, thin-walled sections, applications requiring high-quality bead formation.

2.2 Welding consumables

(1) Manual Arc Welding (Electrodes)

Type: E43 series (AWS E6015/E6016)

Grades: J426, J427, CHE427 and other low-hydrogen electrodes

Drying: 300–350°C × 1h, hold at 100–150°C; use as required

(2) Gas Shielded Arc Welding (Solid / Flux-Cored)

Solid wire (GMAW): ER50-6 (AWS ER70S-6), φ1.0/1.2 mm

Shielding gas: CO₂ (≥99.5%) or 80% Ar + 20% CO₂

Flux-cored wire (FCAW): E501T-1/E501T-5 (commonly used in shipbuilding)

(3) Submerged arc welding (SAW)

Welding wire: H08A/H08MnA

Flux: HJ431/SJ101 (neutral / basic)

3. Pre-welding Preparation

3.1 Groove Design

t < 12 mm: I-groove, gap 0–2 mm

t ≥ 12 mm: V-groove, angle 60°±5°, fillet 1–2 mm, gap 2–3 mm

t > 25 mm: X-groove (double-sided welding to minimise welding distortion)

3.2 Surface Preparation

Rust, oil, paint, scale and moisture must be thoroughly removed from the groove and the area extending ≥20mm on either side; the surface must be ground to a metallic sheen. In low-temperature, high-humidity environments, preheating and dehumidification (50–80°C) are required.

3.3 Preheating and Interpass Temperature

Special operating conditions: In environments where humidity exceeds 80% or temperatures fall below 0°C, the unit must be preheated to above 50°C and moisture must be removed.

3.4 Tack Welding

Tack weld length 30–50 mm, spacing 200–300 mm, tack welds ≤ 2/3 of the design tack welds; No defects such as porosity, cracks or inclusions are permitted; any defects must be ground out and the weld re-welded.

4. Welding Process Parameters

4.1 Shielded Metal Arc Welding (SMAW)

4.2 CO₂ Gas Shielded Arc Welding (GMAW, ER50-6, φ1.2mm)

4.3 Submerged Arc Welding (SAW, H08MnA, φ4.0)

5. Key Welding Procedures

5.1 Short Arc, Multi-pass Welding

Single-pass weld thickness ≤ 4 mm; single-pass width ≤ 5 times the wire diameter; thick plates must be welded using multi-pass welding, with scale removed and defects inspected after each pass.

5.2 Stick Movement and Angle

Flat welding: Use straight or slight oscillating stick movement; travel angle 70–80°

Vertical-up welding: Weld from bottom to top using low current and short-arc technique

Fillet welding: Tilt the torch at 45° towards the base metal to ensure good fusion

5.3 Arc striking and extinguishing

The arc must be struck within the groove; striking the arc on the non-welded area of the base metal is strictly prohibited. When extinguishing the arc, the crater must be filled to prevent crater cracking; the extinguishing point must overlap the previous weld bead by 10–20 mm.

5.4 Deformation Control

Deformation shall be controlled by means of reverse bevel (1–3°), rigid clamping, symmetrical welding and segmented back-welding; for long welds, segmented skip welding shall be used, with each segment measuring 300–500 mm in length.

6. Post-welding Treatment and Inspection

6.1 Post-weld Heat Treatment (PWHT)

ABS Grade B generally does not require post-weld heat treatment; however, stress-relief annealing at 600–650°C with a holding time of 1–2 hours per millimetre is recommended in the following cases:

Thick plates (>30 mm) in highly constrained structures

Structures intended for service in low-temperature or corrosive environments

Areas sensitive to welding residual stresses

6.2 Visual Inspection (100%)

The weld bead shall be uniform in shape, free from defects such as cracks, porosity, inclusions and lack of fusion; undercut >0.5 mm shall be ground; weld height 0–3 mm; fillet dimension tolerance ±1 mm.

6.3 Non-Destructive Testing (NDT, in accordance with ABS Rules)

Critical structures: 100% ultrasonic testing (UT) or magnetic particle testing (MT)

Fillet welds and non-critical structures: Sampling for MT/PT testing

Acceptance criteria: ABS Rules for Materials and Welding Part 2

7. Common Defects and Prevention

8. Scope of Application and Regulatory Basis

Scope of Application: Hull structures, decks, bulkheads, slipways, etc., of ABS-certified ships and offshore structures

Applicable Standards: ABS Rules for Materials and Welding (Part 2); AWS A5.1/A5.18 Specification for Carbon Steel Electrodes for Shielded Metal Arc Welding

9. Reference Standards and Documents

9.1 ABS 2 PART 2-2021: Rules for Materials and Welding

9.2 AWS D1.1 / D1.6: Structural Welding Code - Steel

9.3 AWS A5.1/A5.18: Specification for Carbon Steel Electrodes for Shielded Metal Arc Welding