Abstract: Provided are a seamless bent pipe constituted by a bent section and straight pipe sections on both ends of the bent section, with the inside diameter at each pipe end portion being larger than the inside diameter of the bent section, and a welded component comprising a seamless bent pipe and a seamless straight pipe at one or each end of the seamless bent pipe, with the end of the seamless straight pipe to be welded to one or each end of the seamless bent pipe having the same inside diameter as the inside diameter of the seamless bent pipe, as well as methods of manufacturing them. As a result, elements suited for use in pipelines can be obtained, without unnecessarily increasing the wall thickness of the seamless bent pipe and without internal machining of the pipe end portions of the seamless bent pipe after the manufacturing thereof.

Abstract: Provided are a seamless bent pipe constituted by a bent section and straight pipe sections on both ends of the bent section, with the inside diameter at each pipe end portion being larger than the inside diameter of the bent section, and a welded component comprising a seamless bent pipe and a seamless straight pipe at one or each end of the seamless bent pipe, with the end of the seamless straight pipe to be welded to one or each end of the seamless bent pipe having the same inside diameter as the inside diameter of the seamless bent pipe, as well as methods of manufacturing them. As a result, elements suited for use in pipelines can be obtained, without unnecessarily increasing the wall thickness of the seamless bent pipe and without internal machining of the pipe end portions of the seamless bent pipe after the manufacturing thereof.

Abstract: Provided are a seamless bent pipe constituted by a bent section and straight pipe sections on both ends of the bent section, with the inside diameter at each pipe end portion being larger than the inside diameter of the bent section, and a welded component comprising a seamless bent pipe and a seamless straight pipe at one or each end of the seamless bent pipe, with the end of the seamless straight pipe to be welded to one or each end of the seamless bent pipe having the same inside diameter as the inside diameter of the seamless bent pipe, as well as methods of manufacturing them. As a result, elements suited for use in pipelines can be obtained, without unnecessarily increasing the wall thickness of the seamless bent pipe and without internal machining of the pipe end portions of the seamless bent pipe after the manufacturing thereof.

Abstract: The present invention provides a mechanical pipe-end expander comprising a cone and a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end, wherein a pipe-end zone is expanded by a wedge effect of the die, which results from a procedure that the cone and the die are inserted together into the pipe-end zone to be expanded, and that then only the cone is axially drawn outwards leaving the die within the pipe-end zone. A seamless steel pipe with an expanded pipe-end zone is manufactured by applying a mechanical pipe-end expander comprising a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end. The resulting seamless steel pipe has satisfactory pipe-end dimensional accuracy, and exhibits characteristics with excellent field welding workability.

Abstract: The present invention provides a lubricant comprising an alkali soap and a cold working method, in which the lubricant layer can be easily formed on the surface of a steel pipe prior to cold working the reduces the work load during cold working of the steel pipe, and whose layer can be easily removed by washing the surface of the steel pipe after cold working. After that, an alkali soap aqueous solution or aqueous pasty alkali soap is applied to the working surface of the steel pipe, cold working of the steel pipe is performed, and thereafter the alkali soap layer is removed by washing with water. The alkali soap aqueous solution or aqueous pasty alkali soap is preferably prepared within a vessel having an inner surface consisting of a non-metal material.

Abstract: Provided are a seamless bent pipe constituted by a bent section and straight pipe sections on both ends of the bent section, with the inside diameter at each pipe end portion being larger than the inside diameter of the bent section, and a welded component comprising a seamless bent pipe and a seamless straight pipe at one or each end of the seamless bent pipe, with the end of the seamless straight pipe to be welded to one or each end of the seamless bent pipe having the same inside diameter as the inside diameter of the seamless bent pipe, as well as methods of manufacturing them. As a result, elements suited for use in pipelines can be obtained, without unnecessarily increasing the wall thickness of the seamless bent pipe and without internal machining of the pipe end portions of the seamless bent pipe after the manufacturing thereof.

Abstract: The present invention provides a lubricant comprising an alkali soap and a cold working method, in which the lubricant layer can be easily formed on the surface of a steel pipe prior to cold working the reduces the work load during cold working of the steel pipe, and whose layer can be easily removed by washing the surface of the steel pipe after cold working. After that, an alkali soap aqueous solution or aqueous pasty alkali soap is applied to the working surface of the steel pipe, cold working of the steel pipe is performed, and thereafter the alkali soap layer is removed by washing with water. The alkali soap aqueous solution or aqueous pasty alkali soap is preferably prepared within a vessel having an inner surface consisting of a non-metal material.

Abstract: The present invention provides a mechanical pipe-end expander comprising a cone and a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end, wherein a pipe-end zone is expanded by a wedge effect of the die, which results from a procedure that the cone and the die are inserted together into the pipe-end zone to be expanded, and that then only the cone is axially drawn outwards leaving the die within the pipe-end zone. A seamless steel pipe with an expanded pipe-end zone is manufactured by applying a mechanical pipe-end expander comprising a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end. The resulting seamless steel pipe has satisfactory pipe-end dimensional accuracy, and exhibits characteristics with excellent field welding workability.

Abstract: A steel with excellent-strength and excellent-toughness comprises, by weight percent, C: 0.02 to less than 0.15%; Si: not greater than 1%; Mn: 0.3 to 2.5%; P: not greater than 0.05%; S: less than 0.004%; sol. Al: 0.001 to 0.1%; Ti: not greater than 0.02%; N: not greater than 0.009%; wherein, the metal structure of the steel contains either or both of martensite and bainite, or the tempered structure thereof; an aspect ratio of prior austenite grains is not greater than 1.5, the average short diameter of the prior austenite grains is within a range of 60 to 700 ?m; and the contents of Ti, N, S and the short diameter dr of the prior austenite grains satisfy the following expression (1) and (2): when Ti/N<3.4, Ti + 8.1 ? S ? 0.315 d ? ? ? ? - 30 - 0.011 ( 1 ) when Ti/N?3.4, 3.4 ? N + 8.1 ? S ? 0.315 d ? ? ? ? - 30 - 0.