Coalescing Mechanism:
- Fusion via high-density energy
- Process plan to determine the rate at which Welding can be performed, the size of the region and power density for fusion welding
- PD = P/A
- P = power entering the surface, W (Btu/sec); and
- A = the surface area, mm2 (in2)
- With too low power density, no melting due to the heat conducted into work
- With too high power density, metal vaporizes in affected regions
- Must find a practical range of values for heat density
- In reality, pre & post-heating and non-uniform
- For metallurgical reason, less energy and high heat density are desired.
- Um= KTm2
- where K=3.33x10-6
Heat waste:
- Heat transfer efficiency, f1, between heat source and surface
- Oxyfuel gas welding is inefficient while Arc Welding is relatively efficient.
- Melting efficiency, f2, due to the conduction of a work material
- Al and Cu have low f2
- Hw = f1f2H
- Hw= UmV
Rate Balance:
- HRw = UmWVR
- Where WVR = Volume rate of Metal Welded
Approximate Power Densities and Efficiency
Welding process | W/mm2 | (Btu/sec-in2) |
Oxyfuel | 10 | (6) |
Arc | 50 | (30) |
Resistance | 1,000 | (600) |
Laser beam | 9,000 | (5,000) |
Electron beam | 10,000 | (6,000) |
Arc Welding Process | f1 |
Shield Metal Arc Welding | 0.9 |
Gas Metal Arc Welding | 0.9 |
Flux-cored Arc Welding | 0.9 |
Submerged Arc Welding | 0.95 |
Gas Tungsten Arc Welding | 0.7 |
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