Abstract: 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, the method includes 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.

Abstract: 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.

Abstract: 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, the method includes 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.

Abstract: 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.

Abstract: A cold-rolled steel plate having favorable heat spot resistance and favorable antiwear performance is provided. The cold-rolled steel plate has a chemical composition containing C from 0.03 to 0.12%, Si from 0 to 1.0% (including a case where Si is not added), Mn from 0.2 to 0.8%, P at 0.03% or less (excluding a case where P is not added), S at 0.03% or less (excluding a case where S is not added), Ti from 0.04 to 0.3%, and Al at 0.05% or less (excluding a case where Al is not added). A residue is formed of Fe and unavoidable impurities. Each element satisfies a relationship of 5*C %?Si %+Mn %?1.5*Al %<1 within the aforementioned range of the corresponding content. An average diameter of particles of a Ti-based carbide is from 20 to 100 nm. In this way, the Ti-based carbide is dispersed finely and uniformly, thereby enhancing heat spot resistance and antiwear performance.

Abstract: Manufacturing a cold-rolled steel plate by smelting a steel slab having the chemical composition containing on the basis of percent by mass, C from 0.03 to 0.12%, Si from 0 to 1.0%, Mn from 0.2 to 0.8%, P at 0.03% or less, S at 0.03% or less, Ti from 0.04 to 0.3%, and Al at 0.05% or less, with a residue being formed of Fe and unavoidable impurities, the chemical composition satisfying 5*C %?Si %+Mn %?1.5 *Al %<1, and an average diameter of particles of a Ti-based carbide as a precipitate is from 20 to 100 nm; heating the slab to 1200° C. or more and hot rolling, forming a hot-rolled steel plate; winding the hot-rolled steel plate from 500 to 700° C. to form a hot-rolled coil; and cold rolling or annealing and cold rolling the coil obtaining cross-sectional hardness from 200 to 400 HV.

Abstract: Manufacturing a cold-rolled steel plate by smelting a steel slab having the chemical composition containing on the basis of percent by mass, C from 0.03 to 0.12%, Si from 0 to 1.0%, Mn from 0.2 to 0.8%, P at 0.03% or less, S at 0.03% or less, Ti from 0.04 to 0.3%, and Al at 0.05% or less, with a residue being formed of Fe and unavoidable impurities, the chemical composition satisfying 5*C%-Si %+Mn %?1.5 *Al %<1, and an average diameter of particles of a Ti-based carbide as a precipitate is from 20 to 100 nm; heating the slab to 1200° C. or more and hot rolling, forming a hot-rolled steel plate; winding the hot-rolled steel plate from 500 to 700° C. to form a hot-rolled coil; and cold rolling or annealing and cold rolling the coil obtaining cross-sectional hardness from 200 to 400 HV.

Abstract: A cold-rolled steel plate having favorable heat spot resistance and favorable antiwear performance is provided. The cold-rolled steel plate has a chemical composition containing C from 0.03 to 0.12%, Si from 0 to 1.0% (including a case where Si is not added), Mn from 0.2 to 0.8%, P at 0.03% or less (excluding a case where P is not added), S at 0.03% or less (excluding a case where S is not added), Ti from 0.04 to 0.3%, and Al at 0.05% or less (excluding a case where Al is not added). A residue is formed of Fe and unavoidable impurities. Each element satisfies a relationship of 5*C %?Si %+Mn %?1.5*Al %<1 within the aforementioned range of the corresponding content. An average diameter of particles of a Ti-based carbide is from 20 to 100 nm. In this way, the Ti-based carbide is dispersed finely and uniformly, thereby enhancing heat spot resistance and antiwear performance.

Abstract: A lubricant for use in hot rolling of high chromium stainless steel, the lubricant being continuously supplied to surfaces of hot rolling rolls in contact with the steel being rolled at least during hot rolling of the stainless steel, which lubricant comprises a viscous aqueous solution of water soluble high molecular weight thickener and from 10 to 40% by weight of iron hydroxide powder dispersed in the aqueous solution, said iron hydroxide powder having a median particle size of from not less than 0.1 .mu.m to less than 1 .mu.m and said lubricant having an apparent viscosity within the range of from 1,000 to 50,000 cP.