A process of welding fittings to ends of a double wall pipe comprising forming a first welded joint between an inner pipe and an inner receiver of a first fitting; forming a second welded joint between an outer pipe and an outer receiver of the first fitting; forming a third welded joint between the outer pipe and an outer receiver of a second fitting; and forming a fourth welded joint between the inner pipe and an inner receiver of the second fitting.

The present invention relates to a pipe connection assembly of a heat exchanger for connecting a header tank and a pipe of the heat exchanger, in which a means for preventing a welding ring that fixes a manifold and a pipe from entering into a hollow at one end of the manifold before welding is disposed, and a space is formed between the inner surface of the one end of the manifold and the outer surface of the pipe, thereby preventing the molten welding ring from flowing out.

A method for purging air from a structure to be joined by welding by feeding a liquid cryogen to the structure. The liquid cryogen will enter the structure, warm up and enter the gaseous phase very rapidly. The gaseous cryogen will displace the air that is present in the structure out of the structure and reduce the content of oxygen in the structure to about 10 parts per million when welding can begin.

The present invention relates to a process method for conformal processing of a cylindrical shell inner weld seam by a special mobile robot, a laser scanner is used to scan a cylindrical shell inner weld seam to obtain point cloud data of a contour of a weld seam area first. Weld seam feature identification is carried out to each generatrix, and misidentified generatrices are filtered out to obtain weld seam left and right boundaries. An ideal weld seam processing contour is generated conformally according to the appearance of the weld seam area, weld seam coarse grinding is carried out after correction and compensation, and weld seam contour information after coarse grinding is obtained by scanning after the coarse grinding is completed. Process parameters of the grinding are controlled according to an actual weld seam contour, and weld seam fine grinding is carried out to obtain a smooth weld seam contour.

Provided is a method for producing a circumferential weld joint. With this method, when low-carbon martensitic stainless steel pipes used for pipelines for transportation of petroleum and natural gas are subjected to circumferential welding, the circumferential welding can be performed efficiently using a low-cost welding material having a composition similar to the composition of the low-carbon martensitic stainless steel pipes. Pipe ends of low-carbon martensitic stainless steel pipes containing prescribed components are butted against each other and subjected to multi-pass arc welding using a welding material containing prescribed components. In the first pass in the multi-pass arc welding, CMT welding is performed in which the welding material is moved back and forth against a molten pool to generate an arc intermittently. In the second and subsequent passes, one selected from GMA welding, GTA welding, and the CMT welding is performed.

An assembly method of a piston-cylinder group (10), where the piston-cylinder group (10) includes a cylinder (20) at an end of which a head (40) is fixable, provided with seal gaskets (43). The method includes the steps of: mounting the seal gaskets (43) in appropriate seatings in the head (40); coupling the head (40) with the cylinder (20); and a low-temperature welding of the coupling between the head (40) and the cylinder (20).

A process for preparing a multi-thickness welded steel vehicle rail, the process comprises the steps of: (a) forming a first tube having a first outer diameter, an inner diameter and a first wall thickness; (b) forming a second tube having the first outer diameter, a second inner diameter and a second wall thickness different than the first wall thickness; (c) swaging a first end of the first tube to a second outer diameter less than the second inner diameter of the second tube; (d) inserting the swaged first end of the first tube into an end of the second tube to form a joint; (e) welding the first tube and the second tube together to form a weld at the joint to form a tube blank with a heat affected zone of lower metal strength in the area of the weld; (f) preheating the tube blank to create a common crystalline microstructure along a length of the tube blank; (g) introducing the tube blank into a blow molding tool having inner molding walls; (h) molding the tube blank at an elevated temperature by expanding the tube blank against the inner molding walls of the molding tool by injecting a pressurized medium into an interior cavity of the tube blank; and (i) quenching the tube blank by replacing the pressurized medium with a cooling medium through the molding tool and the tube blank to achieve a rapid cooling effect on the tube blank and to create a completed vehicle rail with essentially uniform material strength across the weld. A completed vehicle rail has an overlapped welded structure and uniform microcrystalline structure along the length of the rail.

A decoupling element for an exhaust system (1) of a combustion engine, with an elastic exhaust gas-conducting body (3), with at least one support ring (7) connected to the body (3) in a fixed manner, which encloses an axial end portion (8) of the body (3) on the outside in the circumferential direction (5), and with at least one flange (9), which is fastened to the support ring (7) by means of a weld seam (12), wherein the flange (9) comprises a connecting piece (13), which is inserted in the end portion (8) of the body (3) enclosed by the support ring (7), and wherein the weld seam (12) is configured circumferential on the outside and connects an axial face end (14) of the support ring (7) facing away from the body (3) to the outer circumference (15) of the connecting piece (13) of the flange (9).

A circumferential welded joint of a line pipe is formed by butting against each other end portions of steel pipes having a yield strength according to 5L Specification of API Standards not smaller than 555 N/mm.sup.2 and welding the butted portions in a circumferential direction. A joint strength ratio σ.sub.match=(TS-w/TS-b).Math.(YS-w/YS-b) represented by a product of a ratio between a tensile strength TS-w of a weld metal and a tensile strength TS-b of a base material and a ratio between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material, and a critical equivalent plastic strain ε.sub.p-cri [%] for ductile crack generation in a base material heat affected zone satisfy Equation (1), and the yield strengths YS-w, YS-b of the weld metal and base material satisfy Equation (2).
σ.sub.match>4.85ε.sub.p-cri.sup.−0.31  (1)
YS-w/YS-b≧1.0  (2)

A tube transition fitting is formed having a first end, a second end, a head, a body, a weld area, and a first wall thickness and second wall thickness. A tube seat is formed on a surface connected to the body, the surface being adjacent a transition from the first wall thickness to the second wall thickness. A tube transition assembly includes a header portion, the tube transition fitting, and a heat exchange tube, each being connected using one or more simplified and/or heat-optimized connections.