Abstract: A riser section for joining to another riser section to form a drilling riser includes a weld region generated by welding a first riser tube to a second riser tube. The weld region includes a fusion zone in which material of the first riser tube coalesces with material of the second riser tube, and a heat-affected zone adjacent the fusion zone. The riser section also includes a cover positioned over the weld region and welded to the first riser tube and to the second riser tube such that the cover covers the fusion zone and the heat-affected zone to protect the zones. The cover may be a solid piece of material that is welded to the riser tubes, or the cover may be a bead of weld filler material that is welded (melted and deposited) onto the weld region of each of the riser tubes.

Abstract: A method for making a riser component includes: positioning a coupler adjacent and end of a tube such that a region of the coupler forms an interface with the tube's end, wherein the region includes a material (in some embodiments an aluminum alloy), and the tube's end includes a groove and another material (in some embodiments a steel alloy) that is different than the region's material; heating the region of the coupler to increase the region's malleability; and exerting pressure on the region of the coupler to plastically deform the region to insert some of the region's material into the groove in the tube's end. By fixing the coupler to the tube in this manner, the coupler may be strongly secured to the tube, and thus able to withstand high, dynamic loads frequently experienced in service. Also, the material of the coupler may be different than the material of the tube, and thus the material of the coupler may be lighter than the material of the tube.

Abstract: A method for making a riser component includes: positioning a coupler adjacent and end of a tube such that a region of the coupler forms an interface with the tube's end, wherein the region includes a material (in some embodiments an aluminum alloy), and the tube's end includes a groove and another material (in some embodiments a steel alloy) that is different than the region's material; heating the region of the coupler to increase the region's malleability; and exerting pressure on the region of the coupler to plastically deform the region to insert some of the region's material into the groove in the tube's end. By fixing the coupler to the tube in this manner, the coupler may be strongly secured to the tube, and thus able to withstand high, dynamic loads frequently experienced in service. Also, the material of the coupler may be different than the material of the tube, and thus the material of the coupler may be lighter than the material of the tube.

Abstract: An apparatus for forming a workpiece to a desired, non-planar configuration are provided. At least one friction stir forming tool, having a shoulder and a pin, is used to urge the workpiece to the desired configuration and friction stir form the workpiece. The forming tool can urge the workpiece against a contour surface of a die or a shoulder that is opposite the structural member from the tool. Thus, the forming tool plasticizes a portion of the workpiece and urges the workpiece to the desired configuration. In addition, the material properties of the workpiece can be improved by the friction stir processing.

Abstract: The present invention provides a tool for forming a friction stir weld joint in a workpiece. According to one embodiment, the tool includes a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint. The tool includes a rotatable first shoulder defining an aperture therethrough structured to slidably receive the first end of the pin. The tool also includes a second shoulder defining an aperture structured to receive the second end of the pin such that the pin extends between the first and second shoulders and such that the second shoulder is in rotatable communication with the pin. The first shoulder is structured to rotate independently of the pin and the second shoulder.

Abstract: The present invention provides a tool for forming a friction stir weld joint in a workpiece. According to one embodiment, the tool includes a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint. The tool includes a rotatable first shoulder defining an aperture therethrough structured to slidably receive the first end of the pin. The tool also includes a second shoulder defining an aperture structured to receive the second end of the pin such that the pin extends between the first and second shoulders and such that the second shoulder is in rotatable communication with the pin. The first shoulder is structured to rotate independently of the pin and the second shoulder.

Abstract: An apparatus for forming a workpiece to a desired, non-planar configuration are provided. At least one friction stir forming tool, having a shoulder and a pin, is used to urge the workpiece to the desired configuration and friction stir form the workpiece. The forming tool can urge the workpiece against a contour surface of a die or a shoulder that is opposite the structural member from the tool. Thus, the forming tool plasticizes a portion of the workpiece and urges the workpiece to the desired configuration. In addition, the material properties of the workpiece can be improved by the friction stir processing.

Abstract: The present invention provides a tool for forming a friction stir weld joint in a workpiece. According to one embodiment, the tool includes a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint. The tool includes a rotatable first shoulder defining an aperture therethrough structured to slidably receive the first end of the pin. The tool also includes a second shoulder defining an aperture structured to receive the second end of the pin such that the pin extends between the first and second shoulders and such that the second shoulder is in rotatable communication with the pin. The first shoulder is structured to rotate independently of the pin and the second shoulder.

Abstract: An apparatus and method for forming a workpiece to a desired, non-planar configuration are provided. At least one friction stir forming tool, having a shoulder and a pin, is used to urge the workpiece to the desired configuration and friction stir form the workpiece. The forming tool can urge the workpiece against a contour surface of a die or a shoulder that is opposite the structural member from the tool. Thus, the forming tool plasticizes a portion of the workpiece and urges the workpiece to the desired configuration. In addition, the material properties of the workpiece can be improved by the friction stir processing.

Abstract: The present invention relates to methods of making large spin blanks out of pieces of aluminum sheet or plate joined by friction stir welding to provide plate blank sizes greater than 156 inch (396 cm) in diameter. Blank sizes greater than 209 inch diameter enable manufacturing possibilities for large one-piece spun parts instead of constructing large structures from pieces. This also applies to sheet, except that the maximum width obtainable is 139 inches (353 cm). The availability of large blank sizes, particularly for sheet, permits the use of traditional spinning where bending is the predominant method of metal movement rather than stretching and spinning. As the present invention is a very cost effective approach, it provides a method for producing significantly more economical spin blanks between 156 and 209 inches in diameter than are obtainable for a single piece blank.

Abstract: The present invention provides an improved structural assembly constructed of a plurality of structural members secured together. At least one of the plurality of structural members defines a first region characterized by comparatively high operational stress and a second region having a locally refined grain structure positioned such that the second region at least partially encompasses the first region to thereby enhance the strength, toughness and fatigue resistance of the at least one structural member in the first region. The present invention also provides a method for selectively improving the strength, toughness and fatigue resistance of a structural member in a region of high operational stress including the steps of casting the structural member in a pre-selected configuration. Regions of the structural member having comparatively high operational stress are identified. The structural member is secured to prevent movement.

Abstract: The welding apparatus and associated method are provided. The welding apparatus includes a welding tool for forming a weld joint along the surface of at least one workpiece. The welding apparatus also includes a compression tool for selectively inducing a layer of residual compressive stress in at least a portion of the surface of the weld joint and the surface of the at least one workpiece to thereby improve the material properties of the workpiece, including corrosion resistance and fatigue strength.

Abstract: The present invention provides a tool for forming a friction stir weld joint in a workpiece. According to one embodiment, the tool includes a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint. The tool includes a rotatable first shoulder defining an aperture therethrough structured to slidably receive the first end of the pin. The tool also includes a second shoulder defining an aperture structured to receive the second end of the pin such that the pin extends between the first and second shoulders and such that the second shoulder is in rotatable communication with the pin. The first shoulder is structured to rotate independently of the pin and the second shoulder.

Abstract: The method of manufacturing a structural assembly includes positioning a first structural member at least partially adjacent a second structural member to define an interface therebetween and inserting a rotating plug into the first and second structural members at the interface to thereby join the first structural member to the second structural member. The resulting friction plug weld provides a relatively strong joint between the structural members, requires less forming and machining time, and is compatible with single-sided tooling. Additionally, the friction plug weld is compatible with other joining methods, such as friction stir welding.

Abstract: The present invention relates to methods of making large spin blanks out of pieces of aluminum sheet or plate joined by friction stir welding to provide plate blank sizes greater than 156 inch (396 cm) in diameter. Blank sizes greater than 209 inch diameter enable manufacturing possibilities for large one-piece spun parts instead of constructing large structures from pieces. This also applies to sheet, except that the maximum width obtainable is 139 inches (353 cm). The availability of large blank sizes, particularly for sheet, permits the use of traditional spinning where bending is the predominant method of metal movement rather than stretching and spinning. As the present invention is a very cost effective approach, it provides a method for producing significantly more economical spin blanks between 156 and 209 inches in diameter than are obtainable for a single piece blank.

Abstract: The present invention provides an improved structural assembly constructed of a plurality of structural members secured together. At least one of the plurality of structural members defines a first region characterized by comparatively high operational stress and a second region having a locally refined grain structure positioned such that the second region at least partially encompasses the first region to thereby enhance the strength, toughness and fatigue resistance of the at least one structural member in the first region. The present invention also provides a method for selectively improving the strength, toughness and fatigue resistance of a structural member in a region of high operational stress including the steps of casting the structural member in a pre-selected configuration. Regions of the structural member having comparatively high operational stress are identified. The structural member is secured to prevent movement.

Abstract: Large diameter dome tanks made of a plurality of plates friction stir welded together to form a blank and spun and/or stretched into form. The dome tanks may be for holding liquid rocket fuel. Methods of forming include friction stir welding two or more flat blanks together and spinning the combined workpiece into a hemisphere. The blanks may be sufficiently thick to enable stretching as well as spinning. Aluminum alloys may be used, and filler material may be included in thee friction stir welds to reduce grain growth and problems associated therewith in the spinning process.

Abstract: The method of manufacturing a structural assembly includes positioning a first structural member at least partially adjacent a second structural member to define an interface therebetween and inserting a rotating plug into the first and second structural members at the interface to thereby join the first structural member to the second structural member. The resulting friction plug weld provides a relatively strong joint between the structural members, requires less forming and machining time, and is compatible with single-sided tooling. Additionally, the friction plug weld is compatible with other joining methods, such as friction stir welding.

Abstract: The present invention provides a tool for forming a friction stir weld joint in a workpiece. According to one embodiment, the tool includes a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint. The tool includes a rotatable first shoulder defining an aperture therethrough structured to slidably receive the first end of the pin. The tool also includes a second shoulder defining an aperture structured to receive the second end of the pin such that the pin extends between the first and second shoulders and such that the second shoulder is in rotatable communication with the pin. The first shoulder is structured to rotate independently of the pin and the second shoulder.

Abstract: The welding apparatus and associated method are provided. The welding apparatus includes a welding tool for forming a weld joint along the surface of at least one workpiece. The welding apparatus also includes a compression tool for selectively inducing a layer of residual compressive stress in at least a portion of the surface of the weld joint and the surface of the at least one workpiece to thereby improve the material properties of the workpiece, including corrosion resistance and fatigue strength.