Common welding defects produced during shipyard welding :
- Crack : Most critical and frequent welding defect. There are two types of common cracks.
- Solidification crack : Mostly caused by high current with high speed welding. Proper welding parameters and heat inputs can prevent solidification cracks. Control of proper joint gap is also needed to prevent fillet weld longitudinal crack.
- Hydrogen crack : The most sensitive issue in a welding structure. Accurate root cause analysis is very important for hydrogen cracking. Proper control of preheat, current, welding speed is necessary to prevent hydrogen crack especially for high strength steel.
- Porosity : Critical for pipe welding of special materials such as Duplex, Cu-Ni, or Ti. Enough shielding gas should be maintained with proper wind shield for outdoor welding. Low current low welding speed is desirable to prevent porosity. Surface impurities should be removed before welding.
- Incomplete penetration : Common defects for multi-pass welding of thick plates. Proper welding joint is important, especially with back gouging when necessary. Joint gap should be maintained during pipe welding to create proper back bead.
- Duplex stainless steel welding : DSS or SDSS is one of the most critical metals that may cause many welding defects. Common mistakes for handling of duplex pipe is heat correction during joint preparation of piping. Heating cause sigma phase in the structure which can lead to cracking, corrosion or pitting. Improper welding parameters can also create sigma phase or secondary austenite structures, which can lead to similar defects.
