• Very- to ultra-fine grain size
  • Low matrix dislocation density – high ductility
  • Consolidation of materials with high porosity, such as machining swarf
  • Larger sizes than other severe plastic deformation processes
  • Can produce solid rods or tubular products
  • Ability to disperse hard particles in a matrix without segregation

Tool choice is critical for friction stir welding. Joint design and welding machine capabilities dictate the best style to use.

The most common tool types are conventional tools and self-reacting tools.

Conventional welding tools have a rotating pin – called a probe – and shoulder. They are used for butt or lap joints

Key components of this tool type include:

  • Pin that stirs the joint and is slightly shorter than the thickness of the workpiece for butt joints and slightly longer for lap joints
  • Shoulder that rides on the surface of the workpiece and prevents escape of the softened material
  • Rigid anvil that supports the workpiece along the joint line

These tools may be monolithic or multi-component.

Self-reacting (bobbin) welding tools eliminate the need for a rigid anvil to react the forces of welding. Two shoulders, one on each side of the workpiece, are connected by a pin.

  • Fixed-gap tools maintain a fixed spacing between the shoulders
  • Variable-gap tools require a mechanism to actuate the pin and change the spacing between the shoulders

Workpiece material determines tool materials

FSW operates just below the melting point of the workpiece material. That’s why it’s important to choose welding tool materials specifically designed for the workpiece material.

Aluminum welds at low temperature, so H13 tool steel is a good choice. Other materials used for aluminum include MP159 (not to be used for 5XXX aluminum alloys), tungsten carbide and other hot-work tool steels.

Steel welds call for either refractory or super-abrasive metal tools. Refractory metal tools, made from tungsten or tantalum, can be alloyed with rhenium, lanthanum, or other elements to increase strength. Polycrystalline cubic boron nitride (PCBN) tools can be made with different binders to tailor properties to different applications.

Titanium welds require tools made from the same materials as for steel. However, not all tools for steel work in titanium.

Bond produces all types of friction stir welding tools. Our welding specialists can help guide the right selection, based on customer design or designs we produce. Learn more

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