A flat tube for a heat exchanger, with two open ends defining its longitudinal direction, comprising a first wall and a second wall which are flat and parallel to each other, thereby delimiting the inner space of the tube, and further comprising an inner fin located between the first and the second walls, wherein one of the lateral sides of the first wall comprises a main fold running along the longitudinal direction, wherein arms of the main fold form a slit facing the inner space of the tube, and the lateral side of the second wall is bent to cover the main fold.

Methods are disclosed for fabricating heat exchangers and Heat Exchanger (HX) tubes, as are heat exchangers fabricated in accordance with such methods. In embodiments, the method includes the steps or processes of obtaining a Non-Equilibrium Alloy (NEA) feedstock powder comprised of an alloy matrix throughout which at least one minority constituent is dispersed. The first minority constituent precipitates from the alloy matrix when the NEA feedstock powder is exposed to temperatures exceeding a critical temperature threshold (T.sub.CRITICAL) for a predetermined time period. A cold spray process is carried-out to at least partially form the HX tubes from the NEA feedstock powder; and the HX tubes are subsequently installed in the heat exchanger. The HX tubes are exposed to a maximum temperature (T.sub.SPRAY_MAX) during the cold spray process, which is maintained below T.sub.CRITICAL to substantially preserve the non-equilibrium state of the NEA feedstock powder through cold spray deposition.

A method for synchronous and specified-length cutting of continuously-formed materials by multiple lathes connected in series in production lines of continuously-formed materials, such as steel pipes and steel sections. A synchronous and specified-length cutting machine having multiple lathes connected in series is provided with two or more lathes that are separately equipped with a cutting tool. The lathes are installed in series on a rail parallel to a material and are driven by respective driver means to move back and forth according to a set procedure; in the case that the speed of the lathe is synchronous with that of the material, the cutting tool on the lathe cuts the material according to a specified length. The cutting machine can be adapted to high-speed production lines, allows a small minimum specified length, possesses cutting tools having a long service life, and achieves smooth cuts.

An electric resistance welded steel pipe having excellent formability and torsional fatigue resistance and a method for manufacturing the same. The electric resistance welded steel pipe includes a seam region and a base metal region, the seam region having a range of 10 degrees in a pipe circumferential direction with respect to an electric resistance welded seam formed in a pipe longitudinal direction, the base metal region being a region other than the seam region. The electric resistance welded steel pipe has an r-value in the pipe longitudinal direction of 1.0 or greater, H (mm) and W (mm) satisfy a specified formula, and Ts.sub.(MAX) (mm) and Tb.sub.(Ave) (mm) satisfy a specified formula.

A method and device provides for alternately cutting off material by back-and-forth movement of multiple vehicles. Specifically, the device is a cut-off machine for alternately cutting off material by back-and-forth movement of multiple vehicles. The cut-off machine is at least provided with two cutter vehicles, wherein these vehicles are installed on tracks parallel to material. The tracks are arranged around the material side by side. Each vehicle moves back and forth in accordance with a set sequence. Cutters on the vehicles alternately cut off the material in accordance by a set length. The larger the number of vehicles, the longer the possible stroke of each vehicle can be, such that the cutters have more time to cut off the material. Accordingly, the cut-off machine can be adapted to higher material forming speeds in a production line.

A method for joining edges and/or surfaces of a profile in a profiling installation for longitudinally forming a virtually endless material strip into an at least partially closed profile shape. The material strip or profile is formed roll forming tools into a profile which is closed or partially closed, and is fixed in a joining zone, with a longitudinally running joining seam being formed. The profile passes in the joining zone through a joining roller arrangement and/or planar joining arrangement to feed the profile to a joining point and to stabilize the profile there, and/or to ensure that it is dimensionally stable during and after joining. Forces or magnitudes of force components which act on the profile from at least one of the joining rollers and/or a subsection of the planar joining arrangement are detected in the joining zone. A planar joining arrangement and a profiling installation are also provided.