A method for manufacturing a clad steel pipe is provided, wherein the clad steel pipe is manufactured by using a clad steel plate as a raw material. The clad steel plate comprises a base layer (1) and a clad layer (2) roll-bonded with the base layer (1). The method for manufacturing a clad steel pipe comprises the steps of forming, welding, and deburring; both sides of the clad steel plate are bent towards the base layer (1) side of the clad steel plate, then the forming step is carried out, and after the forming step, the opening faces of the resultant pipe blank are all in a form of the clad layer (2). According to the method for manufacturing a clad steel pipe, a clad steel pipe is manufactured by using a clad steel plate as a raw material. Thus, continuance and high efficiency of a high-frequency longitudinal welding pipe unit is fully utilized, subsequent non-continuous processes are not necessary, and the corrosion resistance at the weld of the clad steel pipe is ensured.

A method for manufacturing a clad steel pipe is provided, wherein the clad steel pipe is manufactured by using a clad steel plate as a raw material. The clad steel plate comprises a base layer (1) and a clad layer (2) roll-bonded with the base layer (1). The method for manufacturing a clad steel pipe comprises the steps of forming, welding, and deburring; both sides of the clad steel plate are bent towards the base layer (1) side of the clad steel plate, then the forming step is carried out, and after the forming step, the opening faces of the resultant pipe blank are all in a form of the clad layer (2). According to the method for manufacturing a clad steel pipe, a clad steel pipe is manufactured by using a clad steel plate as a raw material. Thus, continuance and high efficiency of a high-frequency longitudinal welding pipe unit is fully utilized, subsequent non-continuous processes are not necessary, and the corrosion resistance at the weld of the clad steel pipe is ensured.

An electric resistance welded steel pipe, and a method for manufacturing the same are provided. An electric resistance welded steel pipe has a welded portion that includes a heat-affected zone having a steel microstructure principally including a bainitic ferrite phase and/or a bainite phase. The steel microstructure at half the wall thickness includes a bainitic ferrite phase and/or a bainite phase in a total area ratio of 90% or more. In the steel microstructure located 1 mm in the wall thickness direction, the bainitic ferrite phase and/or the bainite phase has an average grain size of 20 μm or less. The average grain size of the bainitic ferrite phase and/or the bainite phase located 1 mm in the wall thickness direction is 0.5 times or more and 2 times or less the average grain size of the bainitic ferrite phase and/or the bainite phase at half the wall thickness.

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.

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.

In a method for manufacturing a metal pipe from a metal plate using a forming tool, the position of the tool is optimized simply and correctly by incorporating individuality of the raw material plate into setting of the tool position.

As a preparatory stage, a forming process is analyzed by simulation for each plate. Based on result of the analysis, correlation between a deformed shape value of a raw pipe and tool position information is acquired. Then, the forming process for each plate is stored as correlation between the deformed shape value of the raw pipe and the tool position information. During pipe manufacturing, a deformed shape value of the raw pipe is measured actually while a plate is passed. On the basis of the actually measured deformed shape value, a forming process for the raw pipe is expected and assumed (by using the correlation). Tool position information necessary for implementing the expected and assumed forming process is retrieved from the stored correlation. The retrieved tool position information is realized at a stand array.

In a method for manufacturing a metal pipe from a metal plate using a forming tool, the position of the tool is optimized simply and correctly by incorporating individuality of the raw material plate into setting of the tool position.

As a preparatory stage, a forming process is analyzed by simulation for each plate. Based on result of the analysis, correlation between a deformed shape value of a raw pipe and tool position information is acquired. Then, the forming process for each plate is stored as correlation between the deformed shape value of the raw pipe and the tool position information. During pipe manufacturing, a deformed shape value of the raw pipe is measured actually while a plate is passed. On the basis of the actually measured deformed shape value, a forming process for the raw pipe is expected and assumed (by using the correlation). Tool position information necessary for implementing the expected and assumed forming process is retrieved from the stored correlation. The retrieved tool position information is realized at a stand array.

A combined skiver and a smooth rolling tool with a skiver head and behind this a smooth rolling head, wherein between the skiver head and the rolling head an exclusive torque transmitting coupling is located which restricts the allowable axis shaft offset and/or the angular position of the axes of the rolling head and skiver head, to which the rolling head is connected, characterized in that the skiver head (2) is guided through a workpiece bore via a hydrostatic guideway.

A combined skiver and a smooth rolling tool with a skiver head and behind this a smooth rolling head, wherein between the skiver head and the rolling head an exclusive torque transmitting coupling is located which restricts the allowable axis shaft offset and/or the angular position of the axes of the rolling head and skiver head, to which the rolling head is connected, characterized in that the skiver head (2) is guided through a workpiece bore via a hydrostatic guideway.

An overlapping and progressive forming method for a high-performance multi-element NiAl-based alloy tubular part, including: winding continuously flexible substrates of Ni and Al, and alloying coating continuously or selectively along a width direction or a rolling direction to obtain coated flexible substrates; winding continuously the coated flexible substrates on an outer surface of a core roller according to a sequence of Ni above and Al below to form a Ni/Al laminated structure having a plurality of layers with an outermost layer being a Ni layer, and consolidating with ultrasonic with assistance of a pulse current to combine the continuously wound flexible substrates into a laminated tube blank; and placing the laminated tube blank into a mold, applying a pulse current to both ends of the laminated tube blank for hot fluid high-pressure forming, and synthesizing in-situ to prepare the tubular part with assistance of the pulse current.