Solid-State Welding Processes PDF

Solid-state Welding Processes prof. Pasquale Russo Spena  Solid State Welding (SSW)  Coalescence of part surfaces is achieved by:  Pressure alone, or  Heat and pressure  If both heat and pressure are used, heat is not enough...

Solid-state Welding Processes prof. Pasquale Russo Spena  Solid State Welding (SSW)  Coalescence of part surfaces is achieved by:  Pressure alone, or  Heat and pressure  If both heat and pressure are used, heat is not enough to melt work surfaces  For some SSW processes, time is also a factor  No filler metal is added  Each SSW process has its own way of creating a bond at the faying surfaces P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Solid State Welding Processes  Forge welding  Cold welding  Roll welding  Hot pressure welding  Diffusion welding  Explosion welding  Friction welding  Friction Stir Welding  Ultrasonic welding P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Friction Welding (FRW) Friction welding is a form of solid-state welding where the heat is obtained from the mechanically induced sliding motion between the parts to be welded. When certain temperature is reached, the rotational motion is seized and the pressure applied welds the parts together. The two shafts joined by FW process is depicted in Figure. This welding process can be controlled by regulating the time, rotational speed and pressure P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Friction Welding (FRW) SSW process in which coalescence is achieved by frictional heat combined with pressure  When properly carried out, no melting occurs at faying surfaces  No filler metal, flux, or shielding gases normally used  Process yields a narrow HAZ  Can be used to join dissimilar metals  Widely used commercial process, amenable to automation and mass production P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Applications / Limitations of FRW Applications:  Shafts and tubular parts  Industries: automotive, aircraft, farm equipment, petroleum and natural gas Limitations:  At least one of the parts must be rotational  Flash must usually be removed  Upsetting reduces the part lengths (which must be taken into consideration in product design) P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Friction Stir Welding (FSW) Friction stir welding (FSW) is a solid-state joining process that uses a non- consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough. FSW invented by TWI (The Welding Institute, UK) in 1991. P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Friction Stir Welding FSW of aluminium is an established technique. pin shoulder shank P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW weld Source: TWI P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW weld P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW machines Gantry machine Anthropomorphic robot - Versatile - Less expensive - Higher vertical force (also over 100 kN) - Soft metals (i.e. Al alloys) - High rigidity - Low vertical force (usually up to 20 kN) - Strong metals (i.e. 7xxx Al, steels, Ti - Low rigidity alloys, Cu alloys) - Less versatile - More expensiveP. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW FSW can operate with two different configurations: - Tool position control The vertical position of the tool is kept constant during welding. As a result, the vertical force changes during welding. - Vertical force control The vertical force is kept constant during welding. As a result, the vertical position of the tool changes during welding. It generally ensures a better joint quality. P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW tools - Typical FSW tools for soft materials (Al 2xxx, Mg alloys) and/or low thickness parts (e.g. < 10-15 mm for Al 2xxx) - Typical tools for hard materials (e.g. steel, Al 7xxx) and/or high thickness parts (e.g. > 10-15 mm for Al 2xxx) Whorl Triflute P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW tools P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW tools P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW tool wear P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW Applications aluminium extrudates space propellant tank (a) (b) tubes P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW in Automotive Applications wheel rim battery case suspension links for Lincoln rear doors for the Volvo rear car seats stretched limousines Mazda RX-8 P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  FSW keyhole Standard FSW leaves a hole when the tool exits out of the joint end P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Friction Stir Spot Welding (FSSW) In friction stir spot welding, individual spot welds are created by pressing a rotating tool with high force onto the top surface of two sheets that overlap each other in the lap joint. P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Refill FSSW The Refill Friction Stir Spot Welding is a more recent solid-state process befitting of the absence of the keyhole. It can be performed through a proper tool made of different moving parts The absence of the keyhole improves the mechanical strength of the joint. The main disadvantages is related to the cost of the tool head (generally over 50,000 €) P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24  Pinless FSSW Pinless FSSW is a simple operation since it uses a flat shoulder. It allows to avoid the formation of the keyhole and can use cheaper tools. Not suitable when welding thick sheets (about > 2 mm). Source: R.Z. Xu et al. JMST, 2016, 32(1): 76-88 P. Russo Spena - Manufacturing and Assembly Technologies - a.a. 2023-24