The potential adaptation of stationary shoulder friction stir welding technology to steel

Abstract

Stationary shoulder friction stir welding is a newly developed technique currently used for joining plates of relatively soft metals at different angular planes. Although the process is not currently applicable to steel, a study to investigate the theoretical and technical viability of stationary shoulder technology in DH36 steel has been undertaken. Aluminium welds were produced using both conventional rotating shoulder and stationary shoulder friction stir welding techniques, whereas steel welds were produced using only conventional friction stir welding techniques. The effects of stationary shoulder technology on both the microstructural evolution and resultant mechanical properties of aluminium have been evaluated so that the likely effects on steel could be predicted. In the aluminium welds, the stationary shoulder technique results in a distinct transition between stirred and unstirred material, in contrast to the gradual change typically seen in conventional friction stir welds produced with a rotating shoulder. An investigation of weld properties produced in DH36 steel has demonstrated that the microstructure likely to be formed, if the stationary shoulder weld technique was used, would be dominated by a bainitic ferrite phase and so would exhibit hardness and tensile properties in excess of the parent material. It is predicted that if the same abrupt transition between unstirred and stirred material, as seen in aluminium, occurred in steel this would lead to crack initiation followed by rapid propagation through the relatively brittle weld microstructure. Hence the findings demonstrate that stationary shoulder friction stir welding is unlikely to be applicable to steel without further design and process developments

Investigation and development of friction stir welding process for unreinforced polyphenylene sulfide and reinforced polyetheretherketone

“…The shoulder and the pin may have relative movement between them. Depending upon the relative movement of the shoulder, two types of shoulder can be designed: stationary shoulder and rotating shoulder [30]. The tool's pin outer surface is normally threaded which is used to generate sufficient friction and stir the material [26].…”

“…Different tool designs allow stationary or corotation of the shoulder with the tool pin. 27 Additionally, the tool pin’s outer surface is normally threaded which is used actively to generate sufficient friction and stir the material. 28…”

Stabilization of austenite in low carbon Cr–Mo steel by high speed deformation during friction stir welding

“…Friction Stir Welding (FSW) is a solid state welding technique patented by The Welding Institute (TWI) in 1991 in the United Kingdom [1]. With the development of the tools and the studies of the appropriate process conditions, the applications of FSW to various steels have become possible [2][3][4][5][6][7][8][9]. FSW is a solid state joining process with both frictional heat and plastic deformation so that it can be regarded as one of the thermomechanical processes like the hot working process for steel.…”

Microstructural control and mechanical properties in friction stir welding of medium carbon low alloy S45C steel

“…In addition, the absence of ultraviolet or electromagnetic hazards, reduced energy requirements, elimination of consumables such as rods and grinding pastes are cited as some of the additional key benefits of this process [3][4][5]. These advantages make FSW more attractive for joining steels in many industrial applications such as shipbuilding, bridge decking, pipe seam welding, or the applications which were interrupted due to the weldability [6].…”