Practical Guide to Welding ABS DH32 Shipbuilding Steel Plates: Electrode Selection and Preheating

1. Weldability of ABS DH32 shipbuilding steel plates

ABS DH32 shipbuilding steel plates exhibit good weldability, although attention must be paid to the influence of thickness.

The carbon equivalent (CEV) is calculated using the International Institute of Welding (IIW) formula: CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

The carbon equivalent of ABS DH32 shipbuilding steel plate is typically below 0.38%, indicating good weldability and low susceptibility to hydrogen-induced cold cracking. However, as plate thickness increases, cooling rates accelerate and residual stresses rise, leading to a corresponding increase in the risk of cracking.

2. Selection of Welding Consumables: Matching Strength and Toughness

When welding ABS DH32 shipbuilding steel plate, the filler metal must meet the following requirements:

Minimum yield strength: 315 MPa

Impact toughness: Must satisfy impact resistance at -20°C (or lower)

Low hydrogen content: H4 or H5 grade

Recommended welding consumables are as follows:

E7018 is the most commonly used electrode for manual welding of ABS DH32 shipbuilding steel plates, due to its low-hydrogen properties and excellent mechanical properties.

3. Preheating and Interpass Temperature Control

Preheating slows the post-weld cooling rate, allowing hydrogen to diffuse out of the weld metal and heat-affected zone (HAZ) before it causes cracking. Preheating requirements depend on: plate thickness, ambient temperature, hydrogen content of the welding consumables, and joint restraint.

Recommended preheating values for ABS DH32 shipbuilding steel plates:

Interpass temperature control:

The interpass temperature should generally not exceed 200°C, as this will reduce the toughness of the HAZ.

4. Heat Input Control

Heat input calculation formula: Heat input (kJ/mm) = (voltage × current × 60) / (travel speed × 1000)

For ABS DH32 shipbuilding steel plates, the recommended heat input range is 1.5–3.5 kJ/mm:

Too low: Rapid cooling leads to martensite formation and increased hardness.

Too high: Grain coarsening in the HAZ and reduced impact toughness.

5. Post-Weld Heat Treatment (PWHT)

Most welds on ABS DH32 shipbuilding steel plates do not require post-weld heat treatment. However, for thick, large-section sections (typically >50 mm) or highly constrained joints, stress-relief annealing at 550–650°C may be performed. PWHT can reduce residual stresses, but must be carefully controlled to avoid compromising the mechanical properties of the base metal.

6. Common Welding Defects and Prevention

Summary

The key to welding ABS DH32 shipbuilding steel plates lies in: evaluating the welding process in accordance with ABS specifications, and strictly controlling preheating, interpass temperatures and heat input to ensure that the performance of the welded joint matches the excellent properties of the base material.