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Titanium Joining Advances
Welding Code Creeps Ahead at AWS
Michael C. Gabriele, Contributing Editor -- Design News, August 14, 2005
A much-anticipated welding code that promises to aid design engineers and spur the use of titanium in industrial and military applications continues to make steady progress towards final approval.
The D1.9 Structural Welding Code for Titanium will define minimum requirements for welding titanium in structural applications. It is a methodology that includes an introduction, a design section covering static and cyclic loading, details on fabrication, assembly, inspection and welding procedures, and a series of final commentaries. It also will include a ballistic annex with weld specifications for titanium vehicle structures subject to ballistic threats during combat operations.
And ballistic performance is important. The Army's desire to produce lighter, more deployable systems is one of the key drivers in the development of the structural welding code, according to Stephen Luckowski, chief of the prototype manufacturing team for the Army Armament Research Development and Engineering Center. Luckowski also chairs the American Welding Society's D1N subcommittee on titanium structures.
John Lawmon, principal engineer at Edison Welding Institute (EWI) and vice chairman of the AWS's D1N subcommittee, says the code will address critical areas of concern to design engineers. Take weld fatigue, for example. Lawmon explains that while fatigue is well documented for welded titanium components used in the aerospace industry, there is very little information available in the public domain for structural parts such as those used in military ground vehicles or in industrial components.
John Monsees, president of Hi-Tech Welding & Forming Inc. agrees, noting that aerospace specifications are difficult to translate to other applications. "What's needed is a definitive document specifically written for titanium welding to build structural components," he says. "There currently isn't a good book to go to that teaches best practices for welding titanium in structural applications."
But this new code may be just that book. One of the most useful sections of the code for engineers, at least in Lawmon's view, is the final commentaries. This section will provide engineers with insights and background information on issues such as guidance for weld inspection and how to develop data for special part geometries. "These are areas that design engineers will need to think about twice when specifying titanium," he says.
It's expected that the welding code also will promote the use of automated manufacturing systems as a way to further reduce costs and enhance part quality and repeatability. As a parallel effort to support this thrust, EWI has embarked on two research programs. The first program seeks to increase the weld deposition rate and quality of gas metal arc welding (GMAW), also known as metal inert gas (MIG) welding. The goal is to make it at least three times faster than the gas tungsten arc welding (GTAW) process, also known as tungsten inert gas (TIG) welding, by designing pulse-welding parameters for reduced spatter at low current levels.
The second program will look to extend the life of the contact tip in the MIG welding process. Lawmon said the goal is to make MIG more suitable for extended duty cycles in high-volume manufacturing.
Now in its eighth draft, the D1.9 Structural Welding Code for Titanium was submitted in late May to the Structural Welding Committee of the American Welding Society. From there, it will go to the Miami-based society's Technical Activities Committee, whose 40 members represent a broad cross section of the U.S. welding industry. Once finalized by the AWS, the code will be submitted to the American National Standards Institute for publication. John Gayler, a senior staff engineer for the AWS, expects the the final approval will come by late 2006 or early 2007.
Resources Edison Welding Institute Hi-Tech Welding & Forming Army Armament Research Development and Engineering Center
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