A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding
Abstract
A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- August 1994
- Bibcode:
- 1994STIN...9518056M
- Keywords:
-
- Contamination;
- Flow Distribution;
- Flow Velocity;
- Gas Flow;
- Magnetohydrodynamic Flow;
- Plasma Arc Welding;
- Torches;
- Aluminum-Lithium Alloys;
- Cracking (Fracturing);
- Flow Visualization;
- Plasma Control;
- Shadowgraph Photography;
- Weld Strength;
- Mechanical Engineering