Resistance welding aims to make a strong joint between materials with a good weld nugget of the desired size and shape. However, poor weld results may occur with weld defects and failures due to various causes.
Based on scientific research and experimental studies of numerous weld results with actual materials and process conditions, we have classified resistance weld defects and failures into three types: weld material defects, weld nugget failures, and weld external faults. This classification can help quickly identify the root causes and thus reduce and prevent weld defects and failures.
1. Weld Material Defects
- Porosity / Void
- Hot/Cold crack
- Liquid Metal Embrittlement (LME)
- HAZ softening
- Brittle weld
- Intermetallic compound
These weld defects are mainly related to the properties and interactions of individual materials, including surface coating materials. By selecting more compatible materials, some of these defects may be prevented. In most cases, these defects can be reduced or avoided by optimizing the welding process settings to minimize the exposure of materials in the risky range of sensitive temperatures and excessive stresses. SORPAS® simulations can predict certain defects as well as visualize dynamic temperature developments and stress distributions thus help to achieve optimal process settings to reduce and prevent the weld defects.
2. Weld Nugget Failures
- Undersized weld
- Insufficient weld penetration
- Cold weld / Stick weld / False weld
- Interfacial failure
- Partial plug failure
- Poor joint conductivity
Weld nugget failures directly affect the strength and performance of the joint. For spot welding, an OK weld shall result in a full plug (or a hole in the opposing sheet) after breaking, otherwise, it is NOT OK. Both strength and joint conductivity are critical for electrical joints. Most of these failures are caused by poor process settings and can generally be improved by welding process optimizations. SORPAS® simulations and optimizations with actual production conditions can help achieve better optimized process settings to improve weld quality thus prevent undesired weld failures.
3. Weld External Faults
- Surface indentation
- Weld sheet distortion
- Welded structure distortion
- Surface fusion/spatters
- Weld burn-through hole
- Welded part mismatch
These weld distortions and external faults are mostly caused by excessive heating or overloading during the welding process. With SORPAS® simulations and optimizations, it is possible to predict local distortions around the weld, which can be considered as extra requirements for more advanced process optimizations to reduce the weld external faults. The welded structure distortions of larger components are accumulated from the results of individual welds.
SORPAS® simulations and optimizations can be used to reveal and identify the root causes of weld defects and failures thus help to achieve better optimized welding process settings to reduce and prevent weld defects and failures.