Wormhole
Piping are tubular voids in the weld metal that form from gas evolution during solidification. They can lead to corrosion problems and reduced strength.
Physicochemical Mechanism of Action
During welding, gases like carbon dioxide and hydrogen form in the metal. These gases are created under pressure and try to escape. If the gas pressure gets too high, the gases can push through the weld metal and form wormholes.
Metallurgical Relevance & Risks in Welding
Wormholes can lead to corrosion issues because they act as anchor points for corrosion. They also reduce the strength of the material and can lead to cracks or hot cracking. Additionally, they weaken the weld under mechanical stress.
Workshop Practice & Action Guidelines
To avoid wormholes, it's important to keep the weld pool and weld zone clean. Use suitable shielding gases like argon or helium to control gas pressure. Also watch the temperature control and proper cooling of the weld. In heavily loaded applications, post-weld heat treatment (PWHT) might be needed to drive out gases.