Provided is a method for manufacturing an electric resistance welded metal pipe by butting side ends of a metal strip against each other and then welding the side ends by high frequency heating to manufacture an electric resistance welded metal pipe, each side end being provided with an inner surface side corner portion located on an inner surface side of the electric resistance welded metal pipe, wherein the method comprises a step of forming an inclined surface at the inner surface side corner portion before butting the side ends of the metal strip; and wherein the side ends are butted and welded to each other such that the inclined surface remains on an excess metal of the metal pipe after electric resistance welding and a discharged metal is not welded to the excess metal.

A high-strength high-toughness electric-resistance-welded steel pipe having high resistance to post-weld heat treatment is provided. The steel pipe having a composition including C: 0.01% to 0.12%, Si: 0.05% to 0.50%, Mn: 1.0% to 2.2%, P: 0.03% or less, S: 0.005% or less, Al: 0.001% to 0.10%, N: 0.006% or less, Nb: 0.010% to 0.100%, and Ti: 0.001% to 0.050%. The steel pipe having a structure composed of a 90% or more by volume of a bainitic ferrite phase as a main phase and 10% or less (including 0%) by volume of a second phase. The bainitic ferrite phase having an average grain size of 10 m or less, and the structure containing fine Nb precipitates having a particle size of less than 20 nm dispersed in a base material portion. The steel pipe having high strength, toughness, and high resistance that is maintained through post-weld heat treatment.

What is provided is an electric resistance welded steel pipe manufacturing device that is configured to perform welding while forming a strip-shaped steel sheet in a tubular shape and supplying a plasma flow to a pair of abutment end surfaces to perform shielding. The electric resistance welded steel pipe manufacturing device includes a mandrel; and a plasma flow feeder that is provided in the mandrel to supply the plasma flow.

A high frequency power supply system provides highly regulated power and frequency to a workpiece load where the highly regulated power and frequency can be independent of the workpiece load characteristics by inverter switching control and an inverter output impedance adjusting and frequency control network that can include precision variable reactors with a geometrically-shaped moveable insert core section and a stationary split-bus section with a complementary geometrically-shaped split bus section and split electric terminal bus section where the insert core section can be moved relative to the stationary split-bus section to vary the inductance of the variable reactors.

An electric-resistance-welded stainless clad steel pipe or tube that is excellent in both the fracture property of the weld and the corrosion resistance of the pipe or tube inner surface as electric resistance welded without additional welding treatment such as weld overlaying after electric resistance welding is provided. An electric-resistance-welded stainless clad steel pipe or tube comprises: an outer layer of carbon steel or low-alloy steel; and an inner layer of austenitic stainless steel having a predetermined chemical composition, wherein a flatness value h/D in a 90 flattening test in accordance with JIS G 3445 is less than 0.3, and a pipe or tube inner surface has no crack in a sulfuric acid-copper sulfate corrosion test in accordance with ASTM A262-10, Practice E, where h is a flattening crack height (mm), and D is a pipe or tube outer diameter (mm).

An Al plated electric resistance welded steel pipe for hardening use suppressing the formation of scale to the inside of the plating layer while performing hot forming and an Al plated hollow member using that Al plated electric resistance welded steel pipe, wherein the Al plated electric resistance welded steel pipe for hardening use is comprised of a base material made of a tubular steel plate and having a predetermined chemical composition and an electric resistance welded zone provided at a seam portion of the steel plate and extending in a longitudinal direction of the steel plate, the base material is further provided with an intermetallic compound layer positioned on the surface of the steel plate and including an Al-Fe-Si-based intermetallic compound and an Al plating layer positioned on the surface of the intermetallic compound layer and containing Al and Si, and 70X/DY/t30 is satisfied, wherein X (m) is a thickness of the intermetallic compound layer, Y (m) is a thickness of the Al plating layer, t (mm) is a pipe thickness of the steel pipe, and D (mm) is an outside diameter of the steel pipe.

Provided is an electric resistance welded steel pipe or tube having excellent fatigue durability after rapid and short-time heating quenching treatment. An electric resistance welded steel pipe or tube comprises: a base metal being a steel sheet having a specific chemical composition and an electric resistance weld portion having a bond width of 4010.sup.6 m or more and 12010.sup.6 m or less, wherein C.sub.0-C.sub.1 is 0.05 mass % or less, where C.sub.0-C.sub.1 is a difference between C.sub.1 in mass % which is a minimum C content of the electric resistance weld portion and C.sub.0 in mass % which is a C content of the steel sheet, and a depth of a total decarburized layer in each of an inner surface layer and an outer surface layer of the electric resistance welded steel pipe or tube is 5010.sup.6 m or less.

A method of monitoring a manufacturing status of an electric resistance welded pipe manufactured by shaping a steel strip into a pipe and butt welding both end parts of the steel strip in a width direction along a lengthwise direction includes: arranging an imaging unit in a gas shield nozzle having an opening opposing a region in which both of the end parts of the steel strip in the width direction are butt welded and shielding the region with inert gas by ejecting the inert gas onto the region through the opening, the imaging unit having a visual filed including the region; and determining quality of a butt-welded part based on an image shot by the imaging unit.

A sheet metal bearing cage segment includes first and second ring sections, bridges connecting the ring sections to form pockets for rolling elements and a circumferentially facing joint edge configured to be connected to another circumferentially facing joint edge. The joint edge is disposed such that it will be located in one of the bridges after the joint edge is connected to the another circumferentially facing joint edge.

A sheet metal bearing cage segment includes a first ring section, at least one second ring section, and a plurality of bridges connecting the first and second ring sections to each other and defining a plurality of pockets between the bridges. The bearing cage segment includes first and second circumferentially directed joint edges, the first joint edge is configured to connect to the second joint edge of the bearing cage segment or to a second joint edge of another sheet metal bearing cage segment, and the first joint edge includes at least one body of welding material projecting from the joint edge. The body of welding material may be pressed against the second joint edge while leaving a gap between the joint edges, and the welding material can be liquified by a resistance welding process to connect the joint edges.