Wormhole
Wormhole porosity is elongated, tube-shaped gas pores in the weld metal that form from escaping gases during solidification. They cause loss of strength and can lead to cracks.
Physical-Chemical Mechanism
Pipes form when gas bubbles are not adequately removed during welding. These gases (e.g., oxygen, hydrogen) escape during solidification and form long, tube-like structures.
Metallurgical Relevance & Welding Risks
Pipes reduce the strength of the weld metal. They can also serve as initiation points for cracks, especially under mechanical load. This increases the likelihood of failure and can shorten the component's service life.
Workshop Practice & Procedures
To avoid pipes, it's crucial to ensure thorough gas removal. This can be achieved by adequate degassing or using shielding gas. After solidification, the weld should be pressure-tested to ensure no gas bubbles escape. For heavily loaded components, additional ultrasonic testing is advisable.