Joining Techniques

Improved materials, equipment, and processes have made aluminum joining more effective and reliable. Aluminum is readily bonded, welded, brazed, soldered, mechanically fastened, or joined using a combination of techniques, such as weld bonding or rivet bonding.

This portfolio of widely used joining methods has been extensively tested, refined, and characterized to ensure structural, crash, and in-service operating performance—as well as manufacturing viability.

Automotive industry prototyping and testing of aluminum body structures has verified performance reliability and provided valuable feedback to guide improvement.

The number of aluminum joining options continues to grow in response to specific design and assembly challenges.

• Several automakers have demonstrated that aluminum bodies assembled using adhesives in conjunction with either spot welds or rivets equal or exceed chassis stiffness requirements. There have been significant efforts to develop better adhesives, surface preparations and application systems to give body designers yet another value-based aluminum assembly tool. Considering the amount of sealants and caulks used in current body construction, it would seem value enhancing to place those sealants and adhesives in the joints to gain improved structural performance at essentially no cost.
  
• Non-critical joints, such as hood and deck flanges, can be joined using inexpensive, readily automated clinching methods.
  
• Spot welding is increasingly attractive because of new process, material, and equipment developments that extend tip life, enhance weld quality, and reduce welding power demands.
  
• Arc welding is also enhanced due to advances in equipment, such as solid-state power supplies and better wire-feed devices. GTA welding can be used to seam weld at a rate of 300 ipm to provide tailor-welded aluminum blanks for additional weight savings to certain components.
  
• New high-frequency welders make automation more feasible by reducing transformer size in addition to offering greater process control opportunities.
  
• Self-piercing rivets offer a surface-insensitive fastening technique, with strength comparable to spot welding, and the ability to join a variety of material combinations. Improved coatings allow the use of steel self-piercing rivets in aluminum.
  
• Laser, friction-stir, and magnetic-impelled arc welding are but a few of the newer methods being developed to provide automotive body designers even greater aluminum assembly options in the future.