Weldability of CCS Grade B Shipbuilding Steel Plates

1. Overview of Welding Characteristics

Weldability is a key performance indicator for marine steel plates, directly affecting ship assembly efficiency and structural safety. CCS Class B shipbuilding steel plates are characterised by low carbon equivalent (≤0.38%), low sulphur and phosphorus impurity content, and a uniform grain structure, resulting in excellent overall welding performance. These steel plates are suitable for a variety of mainstream welding processes in the shipbuilding industry and are not prone to cold cracking or hot brittleness during welding. This paper systematically analyses the welding mechanisms, applicable processes and standardised guidelines for on-site construction.

2. Key Technical Advantages

Low carbon content: Reduces the tendency for welding hardening; for thin to medium plates with a thickness of ≤50 mm, no preheating is required under ambient conditions.

Optimal Manganese-to-Silicon Ratio: Optimises the fluidity of the weld metal, reducing defects such as slag inclusions.

Stable Mechanical Properties: Ensures that the tensile strength and toughness of the welded joint match those of the base material, thereby avoiding stress concentration in the weld zone.

Strict Impurity Control: Effectively prevents hydrogen-induced cracking in marine humid environments.

3. Suitable Welding Processes

CCS B shipbuilding steel plates are compatible with welding techniques commonly used in the shipbuilding industry, including:

Manual arc welding (SMAW)

Gas metal arc welding (GMAW)

Flux-cored arc welding (FCAW)

Submerged arc welding (SAW)

Process recommendations:

Thick plates >50 mm: Submerged arc welding is recommended to improve welding efficiency and weld bead quality.

Complex structural areas such as hull corners and deck edges: Use Shielded Metal Arc Welding (SMAW) to facilitate flexible operation.

Material requirements: All welding consumables must be CCS-certified to ensure joints comply with maritime safety regulations.

4. On-site Construction Specifications and Precautions

4.1 Pre-welding Preparation

Remove surface rust, oil and scale, and keep the welding area clean and dry.

The ambient temperature during construction should not be lower than -5°C.

4.2 Preheating Requirements

Plates with a thickness exceeding 80 mm must undergo localised preheating to a temperature of 60°C to 100°C to relieve welding stresses.

4.3 Post-welding Treatment

Implement measures for gradual cooling to prevent internal micro-cracks caused by excessive cooling rates.

4.4 Quality Inspection

Critical welds must undergo non-destructive testing (e.g. ultrasonic testing) to comply with CCS hull inspection standards.