A new FSW technology makes improved welding joints that have no heat affected zone and keep the hardness of the base material

Key Word : Welding, friction stir welding, FSW, friction welding, no heat affected zone (no HAZ)

Background / Context / Abstract:

Friction stir welding (FSW) is one of the advanced joint technologies to make structures of vehicles, trains, ships and air planes. However the joint is not always perfect and may lose its hardness since the welding tool rotating with very high speed heats the jointing area and leads to the formation of a heat affected zone (HAZ) whose strength is lower than that of base materials. For example, welded high-tensile steels break at their joints due to the loss of hardness at the HAZ.
This new technology provides a cutting-edge FSW method with no formation of HAZ and no loss of strength at welds.

Technology Overview:

This new FSW technology makes improved welding joints that have no HAZ and keep their hardness as much as the base material. The strong joint is made with a very-slow rotation speed (about 30 rpm) of the welding tool and very high pressure (ten tons for steel or a few tons for aluminium alloy). In these specified condition, the welding joint does not become hot to form HAZ and keeps the strength as much as that of base materials.

Benefits:

1. This FSW method does not lose joint strength as much as that of the base materials since this method does not make HAZ in the welding joint.
2. Steel plates can be welded using a steel tool.
3. Osaka University researchers confirmed that these complete joints can be made of the following materials.
・Medium or high carbon steel, high-tensile steel, ultra-high-tensile steel and high-speed steel
・Aluminium alloys (duralumin, extra super duralumin, 6000-family Al alloys)
・Magnesium alloys
・Dissimilar material welding; e.g. steel and high-speed steel, Al alloy and steel, Al alloy and Mg alloy

Potential Applications / Potential Markets:

New FSW machine that provides complete joints in parts of vehicles, trains, air planes and structures such as bridges and buildings. This technology can be used to weld workpieces made of steel, Al alloy, Mg alloy and dissimilar material welding.
In addition we have confirmed this technology can also be applied to friction welding methods (a solid-state welding process that generates heat through mechanical friction between workpieces).

State of Development / Opportunity / Seeking:

●Opportunity
・Available for exclusive and non-exclusive licensing
・Exclusive/non-exclusive evaluation for defined period (set up for options)
・Collaborative/supportive research
●Seeking
・Licensing
・Development partner

IP Status:

WO2017/154658 (PCT applied in Japanese)

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