P. Edwards, D. G. Sanders, G. L. Ramsey, The Boeing Company, Seattle, WA; G. Coleman, Boeing Commercial Aircraft Group, Seattle, WA; J. Bernath, EWI, Columbus, OH; T. Trapp, Edison Welding Institute, Columbus, OH
The use of Titanium by the aerospace industry has recently been driven to unprecedented levels, which has resulted in price escalations and temporary supply shortages. Most titanium parts are machined out of plate, blocks, forgings or extrusions, which all result in wasted scrap material and unnecessarily high fabrication costs. In order to reduce the buy-to-fly ratio of titanium parts, more efficient manufacturing techniques must be implemented. Laser Welding of titanium 6Al-4V has been developed for producing near net shape structural components. Process parameters have been identified for producing very repeatable, high quality welds on a variety of material thicknesses and joint configurations. Extensive metallurgical examinations and preliminary mechanical property evaluations have been performed to qualify this process for fabricating structural parts. It has been found that the mechanical properties of automated Laser Welded titanium joints are very close to being the same as the parent metal and that equivalent performance can be achieved with a minimal weight increase to the overall part. Furthermore, the statistical variance in the mechanical test data is very low which is extremely important for efficiently designing any performance critical part as a welded structure. In addition to Laser Welding, Friction Stir Welding of titanium 6Al-4V is being developed for a variety of thicknesses and joint configurations. Friction Stir Welding is a solid state welding process capable of retaining the microstructural integrity of the parent material. This makes Friction Stir Welding very attractive for welding fatigue critical and damage tolerant primary air frame structure. Preliminary mechanical test data has shown that the fatigue properties of Friction Stir Welded titanium butt joints are comparable to parent material. The primary difficulty in the development of heavy gage titanium Friction Stir Welding was to identify the tooling designs and process parameters for producing defect free joints.
Finally, by combining one of these advanced welding techniques with Hot Forming, near net shape parts can be produced with aerospace quality dimensional tolerances at a dramatically improved material utilization level. The main considerations for developing Hot Forming of welded titanium structures include tooling designs and processing techniques.
Summary: The use of Titanium by the aerospace industry has recently been driven to unprecedented levels, which has resulted in price escalations and temporary supply shortages. Most titanium parts are machined out of plate, blocks, forgings or extrusions, which all result in wasted scrap material and unnecessarily high fabrication costs. In order to reduce the buy-to-fly ratio of titanium parts, more efficient manufacturing techniques must be implemented. Laser Welding of titanium 6Al-4V has been developed for producing near net shape structural components. Process parameters have been identified for producing very repeatable, high quality welds on a variety of material thicknesses and joint configurations. Extensive metallurgical examinations and preliminary mechanical property evaluations have been performed to qualify this process for fabricating structural parts. It has been found that the mechanical properties of automated Laser Welded titanium joints are very close to being the same as the parent metal and that equivalent performance can be achieved with a minimal weight increase to the overall part. Furthermore, the statistical variance in the mechanical test data is very low which is extremely important for efficiently designing any performance critical part as a welded structure.
In addition to Laser Welding, Friction Stir Welding of titanium 6Al-4V is being developed for a variety of thicknesses and joint configurations. Friction Stir Welding is a solid state welding process capable of retaining the microstructural integrity of the parent material. This makes Friction Stir Welding very attractive for welding fatigue critical and damage tolerant primary air frame structure. Preliminary mechanical test data has shown that the fatigue properties of Friction Stir Welded titanium butt joints are comparable to parent material. The primary difficulty in the development of heavy gage titanium Friction Stir Welding was to identify the tooling designs and process parameters for producing defect free joints.
Finally, by combining one of these advanced welding techniques with Hot Forming, near net shape parts can be produced with aerospace quality dimensional tolerances at a dramatically improved material utilization level. The main considerations for developing Hot Forming of welded titanium structures include tooling designs and processing techniques.
