Friction stir welding: a lower-cost method for welding steel plate and other high-melting-point materials

2025-06-11　·　Wuhan Kaiming High Tech Co., Ltd.

Published:

2025-06-11

Honda developed volume-production friction stir joining of steel and aluminium. Tohoku University and Hitachi developed a cobalt alloy tool for high-melting-point metals such as steel and titanium. The source describes friction stir welding expanding beyond aluminium, copper and magnesium alloys; see footnote *1.Pending confirmation

*1 At standard atmospheric pressure, aluminium melts at 660°C, copper at 1083°C and magnesium at 651°C, compared with 1539°C for iron and 1727°C for titanium.Pending confirmation

Frictional heat softens the metal into a viscous state

Friction stir welding uses a rotating cylindrical tool with a protruding pin. The tool is pressed onto the joint between butt-joined or overlapping plates, joining the two pieces as it rotates.

Friction between the rotating pin and plate softens surrounding metal. The pin enters the material and stirs the softened regions through plastic flow, joining the plates or forming metallic bonds at their interface.

Previously, high-temperature-resistant stirring tools were lacking

The source lists four friction stir welding advantages: solid-state joining without melting, reducing distortion and defects; lower energy use than fusion welding; no shielding gas requirement; and low noise without dust. It also describes joining dissimilar materials to support lightweight construction, while noting that earlier mass-production applications were limited to lower-melting-point metals.Pending confirmation

*2 Compared with fusion welding, which melts the base material, friction stir welding operates at lower temperatures and permits easier control of heat input. This can limit intermetallic compounds that reduce joint strength; a thinner intermetallic layer can improve strength. Excessive stirring can still produce substantial intermetallic compounds.Pending confirmation

Earlier limitations arose from a lack of affordable, heat-resistant tools suitable for volume production. Tool steel tools can weld aluminium alloys but soften and wear at the temperatures required for steel or titanium. Ceramic and tungsten-rhenium tools had been developed, but the source describes them as too expensive for mass production.

Expose fresh steel without stirring

Honda's method joins overlapping steel and aluminium base materials. Its distinguishing feature is stirring only the aluminium, without stirring the steel, to prevent excessive tool temperature.Pending confirmation

Steel and aluminium alloy can be joined without stirring the steel because metallic bonds form at the interface. The process removes steel surface coatings and oxides, exposing a fresh surface that bonds with the activated aluminium alloy during stirring. The source refers to this mechanism in footnote *3.Pending confirmation

*3 Water between steel and aluminium alloy can cause galvanic corrosion. A silicon film inserted between them prevents this in the described technology.Pending confirmation

Honda used this technology for the front subframe of the new Accord for North America. The source reports 25% lower weight than the previous steel subframe, approximately 50% lower welding electricity consumption and 20% greater rigidity at the suspension mounting points, supporting vehicle handling.Pending confirmation

Expand applications through new materials

Tohoku University, Hitachi and Hitachi Metals Precision developed a lower-cost, high-temperature-resistant friction stir welding tool, broadening applications. Tohoku University and Hitachi developed the material; Hitachi and Hitachi Metals Precision developed its mass production and casting technology. The source describes use on steel, titanium and zirconium alloys and a planned launch in autumn 2013. Pricing was still under discussion, with an intended range suitable for mass production.Pending confirmation

Tohoku University and other researchers developed cobalt alloy friction stir welding tools containing intermetallic compounds that retain strength at high temperature. Co3(Al,W) is distributed within the cobalt alloy. Appropriate composition and heat treatment produce a fine, uniform distribution, desired volume fraction and grain boundary structure.Pending confirmation

The source identifies carbon steel, high-strength steel, titanium alloys such as Ti-6Al-4V, pure titanium and copper alloys as prospective materials for the welding tool. Some strengths and thicknesses present difficulties; target applications generally involve tool joining temperatures up to approximately 1000°C.Pending confirmation

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