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Original Date: 07/21/2003
Revision Date: 01/18/2007
Best Practice : Clad Welding with Hot Wire Automatic Gas Tungsten Arc Process
Electric Boat Corporation, Quonset Point Facility achieved a weld wire deposition rate comparable to traditional processes by using the Hot Wire Automatic Gas Tungsten Arc Welding Process. This process produces defective- free parts, eliminating recurrent man-hours of weld repair. Cost savings associated with the Hot Wire Automatic Gas Tungsten Arc Welding Process prompted the company to review all items requiring clad welding to determine if they also could be welded using this process.
Electric Boat Corporation, Quonset Point Facility (EQBP) utilizes clad welding for corrosion resistance, surface hardening, and wear and abrasion resistance. The standard method for clad welding was the use of the submerged and pulse arc processes to achieve a high weld wire deposition rate, reduce actual welding time, and increase productivity. The drawbacks to these processes included the rejectable defects found during the final liquid penetrate Non-Destructive Testing (NDT). Most clad welded surfaces are machined after welding and subject to liquid penetrate NDT. This test is typically performed after final machining and dimensions have been achieved. Repairing these defects is difficult and can distort the part causing an out-of-tolerance condition leading to re- welding. To reduce these occurrences, EBQP explored an alternate process which would result in a defect-free NDT.
The Automatic Gas Tungsten Arc process was examined, but failed to produce the expected result and produced less wire deposition than traditional methods. EBQP found that by incorporating hot wire technology with the automatic gas tungsten arc process, the desired result could be achieved. The hot wire technology heats the wire as it passes through the wire feed system. This requires less amperage to puddle and deposit on the surface resulting in a wire deposition rate similar to traditional methods, but the quality of the weld results in a defect-free final machined part. To help prevent inaccessible welds, designers were given different weld tips (e.g., tungsten tip, wire feed head). This helped the design group produce weld joints with enough accessibility to successfully use the process.
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