Titanium Welding Code Creeps Ahead at AWS

A much-anticipated welding code expected to aid designers and spur the use of titanium in industrial and military applications outside of the aerospace sector continues to make steady progress towards final approval.

Now in its eighth draft, the D1.9 Structural Welding Code--Titanium was submitted in late May to the American Welding Society’s (AWS), Structural Welding Committee. From there it will go to the Miami-based AWS’s Technical Activities Committee (TAC), composed of 40 members representing a broad cross section of the U.S. welding industry.John Gayler, AWS senior staff engineer, described the code as a document whose publication will follow the rigorous approval guidelines of the American National Standards Institute (ANSI), Washington. It’s expected that AWS approval of the code will come in late 2006 or early 2007--possibly sooner. Once finalized by AWS, the code will be submitted to ANSI for publication.The code 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 mandatory ballistic annex, providing specific data offering weld specifications for titanium vehicle structures subject to potential ballistic threats during combat operations.John Lawmon, principal engineer at Edison Welding Institute (EWI), Columbus, OH, said new business opportunities to design and develop titanium parts for structural/architectural and military vehicular applications are spurring the effort to draft the code.The Army's requirements to produce lighter, more deployable systems is a key factor in its use of titanium and the development of a structural welding code, explained Stephen Luckowski, chief, prototype manufacturing team for the Army Armament Research, Development and Engineering Center (ARDEC), Picatinny Arsenal, NJ. Luckowski serves as the chairman of the AWS’s D1N subcommittee on titanium structures.Lawmon, the vice chairman of the D1N subcommittee, said that, once finalized, the code will define critical areas of concern to design engineers, like weld fatigue. Lawmon said 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 construction applications like roofs and facades or structural parts for military ground vehicles.John Monsees, president of Hi-Tech Welding & Forming Inc., El Chajon, CA (near San Diego), said that “what’s needed is a definitive document specifically written for titanium welding to build structural components,” noting that aerospace specifications are difficult to translate for these applications. “There (currently) isn’t a good book to go to teach best practices for welding titanium in structural applications.”Monsees, also a member of the AWS committee, said that, given its light weight, high strength and corrosion resistance, titanium is a “natural choice” for military ground-based vehicles as well as Navy programs like the DDX destroyer and the CVN-21 aircraft carrier. “But (engineers and manufacturers) need welding specifications to design and build titanium systems for these projects,” he said.

For designers, the code will provide a consistent engineering language for utilizing titanium in structural applications. It would accelerate the development process and help inspire improved manufacturing techniques and part designs, which could more fully exploit the high strength-to-weight ratio of titanium.For titanium suppliers and fabricators, the code could help move the metal into new, lucrative industrial programs. It has long been the dream of titanium producers--who historically have sought to minimize titanium’s cost penalty when compared with steel or aluminum--to diversify from aerospace programs into higher volume applications.Perhaps the most revealing and useful section of the code is the final commentaries, according to Lawmon. 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, he said.“These are areas that design engineers will need to think about twice when specifying titanium,” he said. The commentaries also will help designers “read in between the lines” of the code.“Don’t assume the code will solve all application problems,” Lawmon cautioned. “Designers need to think about weld joint details, but they also will need to think about the overall manufacturing process.”It’s expected 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, making 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.

Welding Wisdom: Keep It Shielded, Keep It CleanMonsees, who leads Hi-Tech Welding & Forming, an 80,000-square-foot manufacturing facility with 55 workers, has been contracted by the International Titanium Associations (ITA), Broomfield, CO, to teach a titanium welding seminar at the ITA’s annual conference, which will be held at the Marriott Camelback Inn, Scottsdale, AZ, Sept. 25 to 27.Welding is widely considered to be the key skill set among titanium fabricators, enabling a manufacturer to distinguish itself from competitors. Titanium, highly reactive compared with most metals, must be shielded with inert gases at all times during welding as it readily oxidizes. This protection must be extended to include the hot base metal, the cooling weld bead and the molten puddle. Without this shielding, the result can be cracking and diminished mechanical properties of the part.Offering advice to engineers and manufacturers, Monsees said that, in addition to inert-gas shielding, cleanliness is the watchword when it comes to welding titanium. Using the example of TIG welding, he said this focus on cleanliness includes frequent wire brushing of the base metal using a stainless steel brush designated for titanium only, the use of ultra-high purity argon gas, and the use of high-purity acetone for cleaning the titanium surfaces to be welded and welding filler wire.Maintaining such a clean regimen enables manufacturers to avoid problems such as porosity and a loss of toughness typically associated with improper titanium welding, he said.