A method of friction-stir welding, FSW, ajoint J, for example a T joint and/or a lap joint, between a first workpiece W1 and a second workpiece W2, is described. The method comprises: performing a first pass P1 of FSW of the joint J by moving therealong a first tool (10), comprising a first probe (100) rotating in a first rotational direction RD1, in a first movement direction MD1 defining a first line L1, on a first side S1 of the joint J, comprising: inserting the first probe (100) to a first depth D1, thereby providing a first welded region WR1; withdrawing at least partially the first probe (100), thereby providing a first partially welded and/or unwelded region PWUR1; and fully withdrawing the first probe (100), thereby resulting in a first exit hole EXH1; performing a second pass P2 of FSW of the joint J by moving therealong a second tool (20), comprising a second probe (200) rotating in a second rotational direction RD2, in a second movement direction MD2 defining a second line L2, on the first side S1 of the joint J, comprising: inserting the second probe (200) to a second depth D2, thereby providing a second welded region WR2; optionally withdrawing at least partially the second probe (200); and fully withdrawing the second probe 200, thereby resulting in a second exit hole EXH2; wherein the second welded region WR2 includes the first exit hole EXH1; and wherein the second exit hole EXH2 is included in the first welded region WR1.

A method of friction-stir welding, FSW, a joint J, for example a T joint J, between a first workpiece W1 and a second workpiece W2 is described. The method comprises: arranging the first workpiece W1 and the second workpiece W2; performing a first pass P1 of FSW of the joint J by moving therealong a first tool 10, comprising a first probe 100 rotating in a first rotational direction RD1 and at least partially inserted into the first workpiece W1 and/or into the second workpiece W2 to a first depth D1, in a first movement direction MD1 defining a first line L1, on a first side S1 of the joint J, thereby providing a first welded region WR1; and performing a second pass P2 of FSW of the joint J by moving therealong a second tool 20, comprising a second probe 200 rotating in a second rotational direction RD2 and at least partially inserted into the first workpiece W1 and/or into the second workpiece W2 to a second depth D2, in a second movement direction MD2 defining a second line L2, on a second side S2 of the joint J, thereby providing a second welded region WR2; wherein the first tool 10 and the second tool 20 are mutually opposed; and wherein performing the first pass P1 of FSW and performing the second pass P2 of FSW are at least partially concurrent.

The disclosed wall includes several narrow aluminum sheets and posts that are Friction Stir Welded (FSW) into a sidewall. The length of the wall is the summation of the narrow sheets' width, and the walls width is the narrow sheets' length. Several aluminum posts are spaced along the wall's length direction in order to improve the stiffness and strength of the wall. When welding the aluminum sheets and posts together, the sheets are placed under the posts and jointed tightly together through FSW. With the high-speed spinning of the stirring pin, the post and sheet melt and form into a compact solid phase weld seam under the extrusion of the welding head. When welding two aluminum sheets and one post together, the two sheets are placed edge-to-edge or slightly overlapped. The post is then placed over the sheet joint and the stir-welding head melts portions of the post and the two sheets simultaneously.

A bonding device for joining together a first member (3), an intermediate member (4), and a second member (3) which are layered as a laminated assembly includes a probe (12, 41, 52), an anvil (111, 121), an electric conductor configured to come into contact with the second surface of the laminated assembly, the electric conductor being either the probe or a shoulder member (13, 13a, 61, 64, 68) provided with a through hole for receiving the probe, and a shoulder contact surface configured to abut against the second surface, a drive mechanism (14) configured to rotate the probe around the central axial line and move the probe toward and away from the second member along the central axial line, and an electric power supply (15) electrically connected to the anvil and the probe to conduct electric power through the laminated assembly via the anvil and the probe.

A bonding device for joining together a first member (3), an intermediate member (4), and a second member (3) which are layered as a laminated assembly includes a probe (12, 41), an anvil (11, 11b, 11c, 11d), a shoulder member (13,13a, 61,64,68), a drive mechanism (14) configured to rotate the probe around the central axial line and move the probe toward and away from the second member along the central axial line, and an electric power supply (15) electrically connected to the anvil and the shoulder member to conduct electric current through the laminated assembly via the anvil and the shoulder member.

A bonding device for joining together a first member (3), an intermediate member (4), and a second member (3) which are layered as a laminated assembly includes a probe (12, 41, 52), an anvil (11), a drive mechanism (14) configured to rotate the probe around the central axial line and move the probe toward and away from the second member along the central axial line, and an electric power supply (15) electrically connected to the anvil and the probe to conduct electric current through the laminated assembly via the anvil and the probe.

A friction stir spot welding apparatus includes a pin member formed in a solid cylindrical shape, a shoulder member formed in a hollow cylindrical shape, the pin member being inserted in the shoulder member, a rotary actuator that rotates the pin member and the shoulder member on an axis that is in agreement with an axial center of the pin member, and a linear actuator that linearly moves each of the pin member and the shoulder member along the axis. A tip-end part of the shoulder member is formed in a tapered shape.

A friction stir spot welding apparatus including a controller that (A) operates a rotary driver and a tool driver such that a pin and a shoulder are brought into contact with a welded workpiece; (B) operates, after the step (A), the rotary driver and the tool driver such that the pin separates from the welded workpiece; and (C) operates, after the step (B), the rotary driver and the tool driver such that the pin advances toward the welded workpiece. The controller controls the tool driver such that pressing force applied to the welded workpiece from the pin and the shoulder in the step (C) is smaller than that in the step (B) and/or controls the rotary driver such that rotational frequencies of the pin and the shoulder in the step (C) are lower than those in the step (B).

A cold-rolled and heat-treated steel sheet having a microstructure of, in surface fraction: between 10% and 30% of retained austenite, said retained austenite being present as films having an aspect ratio of at least 3 and as Martensite Austenite islands, less than 8% of such Martensite Austenite islands having a size above 0.5 μm, at most 10% of fresh martensite and
recovered martensite containing precipitates of at least one element chosen among niobium, titanium and vanadium. A manufacturing method thereof is also provided.

A head piece and a welding tool, in particular an FSW tool, equipped therewith, and a welding method. The head piece has a through-opening for a plasticizing welding means, in particular a rotating welding pin. The head piece also has a profiled end face which faces the workpiece during welding and has end face regions of different heights and a sloping shoulder, which conducts the plasticized material of the workpiece and connects the end face regions.