Friction Stir Welding (FSW) is a widely used solid-state joining process, initially adopted to weld aluminum alloys and now successfully applied to other materials, including copper and titanium. The choice of FSW tool material, and tool geometry, significantly impacts both the quality of the weld and the cost per weld – and is therefore an important consideration for manufacturers and industries choosing FSW in their production process.

Unlike traditional welding techniques, FSW doesn’t rely on the fusion of molten metal but on the mixing of frictionally-softened materials to produce a stronger weld. FSW softens the metal by using a spinning tool that produces frictional heat. Sometimes described as more of a forging process than actual welding – FSW is used to join metals not easily fused with traditional welding and is now successfully applied to other materials, including copper, titanium, and other difficult-to-join materials. In general, FSW has been found to produce a low concentration of defects and is very tolerant to variations in parameters and materials.

Choosing the Right FSW Tools

 FSW tools must be sufficiently strong, tough and hard wearing at the welding temperature.  Choosing the right material and tool geometry is key to the success of the weld. For more demanding applications – such as the higher-melting point materials steel or titanium – more advanced tool materials are necessary.

Copper Alloys

Copper alloys offer excellent thermal and electrical conductivity, high corrosion resistance, and good formability. However, welding copper alloys is challenging using conventional welding techniques. FSW is an excellent alternative, producing high-conductivity welds without porosity or other defects. For copper alloys, the suitable welding tools are made of refractory or superalloys such as tungsten carbide or tungsten heavy alloys.

A general rule in FSW tooling is that the pin diameter is roughly the thickness of the material being welded, for thicknesses up to 12mm (0.5”).  The shoulder diameter of the FSW tools should be at least three times larger than the pin diameter, as is the case for all FSW materials.  The choice of tool material and tool geometry plays a key role in optimizing the welding process parameters and achieving high-quality welds.

Stainless Steel

Stainless steel is a widely used material in industrial applications due to its high strength, corrosion resistance, and aesthetic appeal. FSW of stainless steel presents a set of unique challenges due to its low thermal conductivity and high melting point. The tool material should have high thermal conductivity and wear resistance, such as PcBN (polycrystalline cubic boron nitride) or PCD (polycrystalline diamond). The best parameters for FSW of stainless steel should be selected based on the thickness of the material, tooling, and other variables – as is the case for every alloy.

Titanium Alloys

Titanium is a highly desired material in the aerospace, automotive, and medical industries due to its high strength-to-weight ratio, excellent corrosion resistance, and biocompatibility. However, welding titanium alloys using conventional techniques is challenging due to its high melting point and low thermal conductivity. FSW of titanium alloys requires a specialized tool that can withstand high temperatures and resist wear. The preferred FSW tool material for welding titanium alloys is Lanthanated Tungsten. The tool’s shoulder diameter and pin length should be large enough to reduce the amount of load required to form a weld and minimize the heat-affected zone.  However, with the proper tool and parameters many titanium alloys can be welded below the β-transus temperature, improving mechanical properties.

FSW offers a solution for hard-to-weld alloys

Friction stir welding provides an excellent alternative to traditional welding techniques for fusing metals that aren’t easily joined. Copper, stainless steel, and titanium alloys offer innovative opportunities for designing lightweight products with excellent properties. Bond continues pushing FSW technology forward with research and innovation in the development of suitable tools for welding different alloys.

Tools for FSW

With Bond’s advanced FSW solutions, manufacturers can achieve high-quality welds across a variety of materials, enhancing their productivity and product quality. Bond offers a complete line of tools and accessories for all its machine products. All FSW tools are manufactured according to Bond drawings and are inspected to ensure consistent, reliable performance, weld after weld.

Consistent Quality FSW Tools

Clients can be assured that every supply of new tools (of the same part number) will be of the same consistent, high quality that they have come to expect

FSW Tool Types

Bond designs and builds conventional FSW tools, both one-piece and two-piece styles, fixed and variable gap bobbin tools, and stationary shoulder tools.

FSW Tool Kits

Depending on the application, Bond can configure kits of FSW tools to cover different material thicknesses, for short production or research development needs.

FSW Tool Materials

Bond supplies tools made from a variety of materials, such as H13, MP159, W360, W-Re-HfC, W-La, PcBN, and WC.

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