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 40×10.sup.−6 m or more and 120×10.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 50×10.sup.−6 m or less.

A ring forming step includes welding opposite ends of a band saw blade including a body part having a band shape, and a tooth part including a plurality of teeth formed on one side part of the body part, to form a ring shape. A polishing step includes polishing an inner surface, an outer surface, and an end face on a side opposite to the tooth part in the ring-shaped band saw blade subjected to the ring formation. A tip tooth tip forming step includes positioning, after the polishing step, the ring-shaped band saw blade subjected to the ring formation by use of one of the inner surface and the outer surface, and the end face as references, joining a cutting tip to tooth tips of the plurality of teeth by welding, and polishing the joined cutting tip to form a tooth tip shape.

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 40×10.sup.−6 m or more and 120×10.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 Co 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 50×10.sup.−6 m or less.

A manufacturing apparatus of a ring-shaped band saw blade for manufacturing the ring-shaped band saw blade including a tooth tip to which a hard cutting tip is joined. The manufacturing apparatus includes a rotatory moving section that provides rotatory movement of the ring-shaped band saw blade including a body part having a band shape and a tooth part including a plurality of teeth formed on one side part of the body part; a surface polishing section that polishes an inner surface and an outer surface of the body part in the ring-shaped band saw blade in the rotatory movement provided by the rotatory moving section; and an end face polishing section that polishes an end face of the body part on a side opposite to the tooth part in the ring-shaped band saw blade in the rotatory movement provided by the rotatory moving section.

A high-strength thick-walled electric resistance welded steel pipe has excellent low-temperature toughness and excellent HIC resistance and a yield strength of 400 MPa or more. The steel has a chemical composition consisting of C: 0.025% to 0.084%, Si: 0.10% to 0.30%, Mn: 0.70% to 1.80%, controlled amounts of P, S, Al, N, and O, Nb: 0.001% to 0.065%, V: 0.001% to 0.065%, Ti: 0.001% to 0.033%, and Ca: 0.0001% to 0.0035% on a mass percent basis and the remainder being Fe and incidental impurities, and satisfies Pcm of 0.20 or less.

A welding unit for welding together two rails of a track includes two rail clamping assemblies which can be moved towards one another in a longitudinal direction of the rail along unit guides by compression cylinders. Each rail clamping assembly is equipped with clamping jaws which are displaceable in pairs in a pressing plane and each of which has a contact surface provided for application to a rail web. The clamping jaws are each constructed as clamping levers which are pivotable in the pressing plane about a lever pivot axis. The contact surface intended for application to the rail web is disposed at a first lever end spaced apart from the lever pivot axis. The two contact surfaces of each rail clamping assembly are each positioned closer to the oppositely disposed rail clamping assembly than the two lever pivot axes.

A butt-welding device and a method for butt welding workpieces, especially for double-upset resistance-pressure butt-welding of workpieces, particularly wires, strands and profiles, has first and second clamping members for receiving the ends of the workpieces that are to be joined. At least one clamping means can be moved between a starting position and a welding position. At least one deburring tool is provided for deburring the welded workpiece ends. In addition, at least one sensor is provided to determine the geometric dimensions of the workpieces that are to be joined, especially the diameter, the width or the height in the joining plane or substantially parallel thereto, wherein a control unit controls the movement of the clamping members and/or of the deburring tool as a function of the geometric dimension.

A steel sheet that is welded and then cold rolled to a thickness between 0.5 mm and 3 mm, the deformation ratio created by cold rolling in the base metal is equal to ε.sub.MB, for which the deformation ratio created by the cold rolling in the welded joint is equal to ε.sub.S, where:

[00001]$0.4\le \frac{\mathrm{.Math.S}}{\mathrm{.Math.}MB}<0.7.$

A method for the manufacture of a cold-rolled steel sheet of thickness e.sub.f between 0.5 mm and 3 mm is provided. At least two hot-rolled sheets of thickness e.sub.i are supplied and butt welded, so as to create a welded joint (S1) with a direction perpendicular to the direction of hot rolling. The at least two hot-rolled sheets are pickled by continuous passage through a bath, then the assembly is cold rolled, in a step (L1), to an intermediate thickness e.sub.int, the direction of cold rolling (DL.sub.1) coinciding with the direction of hot rolling. The cold rolling is carried out with a reduction ratio ${\mathrm{.Math.}}_1=\mathrm{Ln}\left(\frac{e_i}{e_{\mathrm{int}}}\right)$
such that: $0.35\le \frac{\mathrm{Ln}\left(\frac{\mathrm{ei}}{e\mathrm{int}}\right)}{\mathrm{Ln}\left(\frac{ei}{ef}\right)}\le 0.65,$
then the welded joint (S1) is removed so as to obtain at least two intermediate cold-rolled sheets. Then the two intermediate cold-rolled sheets are butt welded, so as to create a welded joint (S2), the dire

A ring forming step includes welding opposite ends of a band saw blade including a body part having a band shape, and a tooth part including a plurality of teeth formed on one side part of the body part, to form a ring shape. A polishing step includes polishing an inner surface, an outer surface, and an end face on a side opposite to the tooth part in the ring-shaped band saw blade subjected to the ring formation. A tip tooth tip forming step includes positioning, after the polishing step, the ring-shaped band saw blade subjected to the ring formation by use of one of the inner surface and the outer surface, and the end face as references, joining a cutting tip to tooth tips of the plurality of teeth by welding, and polishing the joined cutting tip to form a tooth tip shape.