A method and a device for improving the quality of the weld seam in friction stir welding is provided. The process of friction stir welding is effected by means of a friction welding tip, in which a spiral conveyor screw is provided in the spindle bearing. The longitudinal axis of the spindle bearing is inclined at an angle to the vertical. The sliding surface of the rotating spindle consists of a flat sliding surface and, for the welding of curved seams, in each case of a sliding surface inclined at an acute angle to the sliding surface, the friction welding tip is designed in the shape of a truncated cone. The lateral surface of the truncated cone is formed by six trapezoidal planar parts, of which three planar parts each uniformly distributed at the circumference lie at an angle of 120 degrees with respect to one another and account for a proportion greater than at the circumference.

A rotary tool includes: a main body, and a rotary shaft for transmitting a rotary force; a stirring pin that is arranged on the main body so as to be rotatable by receiving the rotary force and to be movable relative to an axial direction of the rotary shaft, and that is inserted into a joint member to perform friction stirring on the joint member; a shoulder that is formed separately from the stirring pin, that is arranged on the main body so as not to receive the rotary force from the main body but to be movable separately from the stirring pin relative to the axial direction of the rotary shaft, and that presses the joint member while in contact with the joint member; and a first elastic member that biases the stirring pin toward a distal-end side relative to the axial direction of the rotary shaft.

A friction stir welding apparatus that includes a rotary tool and a heating device. The heating device is placed in front of the rotary tool to heat steel sheets that are used as a workpiece. The rotary tool is moved in the welding direction so that steel sheet is softened by frictional heat. Additionally, the surface temperature, the area, and the position of the heated region during the heating process are strictly controlled. The heating of the steel sheets by the welding apparatus provides sufficient strength and good welding workability by advantageously eliminating plastic flow defects generated due to insufficient heating of workpieces.

A joining method is capable of suitably joining metal members of different kinds. The joining method includes a step of preparing a first metal member having a first upper surface, a first lower surface and a first inclined surface connecting the first upper surface and the first lower surface, and a second metal member having a second upper surface, a second lower surface and a second inclined surface connecting the second upper surface and the second lower surface. The second metal member has a higher melting temperature than the first metal member. A butting interface is formed by butting the first inclined surface and the second inclined surface. The first and second metal members are joined by moving a rotary tool along the butting interface while the rotary tool is inserted from the first upper surface and a stirring pin is in contact with the first metal member.

Additive manufacturing systems and methods are disclosed. A housing includes a passageway having first and second open ends. A material is fed through the passageway and exits its second open end. A friction stir weld (FSW) bobbin pin tool is mounted in the housing with a radial edge of the pin tool's annular volume disposed adjacent to the second open end of the passageway. The annular volume is adapted to receive a substrate. The FSW bobbin pin tool is operable to be rotated so that the substrate and the material exiting the second open end of the passageway are plasticized in the annular volume for deposition onto the substrate.

The invention relates to a work interface accessory, comprising an external body having a wall delimiting a recess for the introduction of a rotating portion of the friction stir welding head, an upper plate comprising fastening portions against the head, a central rotating shaft projecting to carry a work tool, the shaft comprising an internally toothed coupling sleeve to allow the shaft to be driven in rotation, when an externally toothed ring gear of the rotating portion of the head rotates in the sleeve.

A double-sided friction stir welding method, methods for producing a cold-rolled steel strip and a coated steel strip, a double-sided friction stir welding apparatus, and facilities for producing a cold-rolled steel strip and a coated steel strip. The double-sided friction stir welding method includes pressing two rotating tools, which are disposed on a first surface and a second surface of a butt portion or overlap portion of the steel strips, against the butt portion or overlap portion of steel strips and moving the rotating tools in the welding direction while rotating the rotating tools in opposite directions to each other, so that an unwelded portion of the steel strips is softened by frictional heat generated between the rotating tools and the unwelded portion of the steel strips, and the softened portion is stirred with the rotating tools to generate plastic flow so as to weld the steel strips together.

Disclosed are rotating tools for double-sided friction stir welding that are applied to double-sided friction stir welding, which is a technique for welding two metal plates by rotating a pair of rotating tools, which oppose each other, in opposite directions, a double-sided friction stir welding apparatus that uses the rotating tools, and a double-sided friction stir welding method. A pair of rotating tools for double-sided friction stir welding that are used in double-sided friction stir welding, which is a technique for welding metal plates by using a pair of rotating tools that are each disposed on one of first and second surfaces of an unwelded portion of the metal plates such that the rotating tools rotate in opposite directions, include end portions each of which is formed in a circular and planar shape. The end portions are each made of a material harder than the metal plates.

A method for friction pressure welding a top workpiece to a bottom workpiece is provided. The method includes plunging a non-consumable refractory tool into the top workpiece with axial plunge pressure and rotational motion. The friction heat generated by the interaction between the tool and the top workpiece diffuses into the faying joint interface and into the bottom workpiece. Friction heat and applied axial plunge pressure promote diffusion bonding at the faying joint interface, which consolidates as a solid-state weld. This inventive method is suitable for spot welding or continuous linear welding, and each workpiece can be comprised of similar or dissimilar materials. After the workpieces are joined, the refractory tool is retracted from the top workpiece. Control variables can include plunge depth, force, and rate of rotation, which can be readily optimized for different material combinations for sound joint formation.

Disclosed is a method for making polystyrene foam which utilizes one or more atmospheric gases, particularly CO.sub.2, as the blowing agent in combination with a polymer processing aid (PPA), typically an ester that is relatively non-volatile at the extrusion temperature range. The blowing agent and the PPA may both be introduced into the molten thermoplastic polystyrene resin or the PPA may be incorporated in the solid source polystyrene resins. The resulting foam will be substantially free of residual blowing agent and dimensionally stable at ambient temperatures.