Abstract: A method for producing a forged crankshaft includes: a preforming step of forming a preformed blank with no flash, the preformed blank including a shape of the crankshaft, wherein the crank arm have excess projecting portions at an outer peripheries of side portions of the crank arm near the crank pin; a die forging step of forming a forged blank with flash by pressing the preformed blank with a pair of first dies; and a trimming step of removing the flash from the forged blank. In the die forging step, while a second die is abutted against a journal-side surface of the crank arm and holds the surface, the excess projecting portions of the crank arm are deformed by the first dies so as to increase the side portions of the crank arm in thickness.

Abstract: In a high strength hot-dip galvannealed hot-rolled steel sheet that has an excellent hole expansibility suitable for a stretch flanging and preferably has a high yield ratio and a tensile strength of at least 650 MPa, a hot-rolled steel sheet used as a base material for plating has a chemical composition comprising: in mass %, C: from at least 0.01 and at most 0.20%; Si: at most 0.50%; Mn: from at least 0.01% to at most 1.30%; P: at most 0.05%; S: at most 0.01%; N: at most 0.01%; Al: at most 0.50%; and Ti: from at least 0.05% to at most 0.50%, and a steel structure consisting of a polygonal ferrite having at least 80 area % and the remainder containing one kind or two or more kinds selected from bainitic ferrite, bainite, pearlite, and cementite.

Abstract: A hot-rolled steel sheet is cooled by jetting cooling water from spray nozzles to a steel sheet conveyance region in a width direction of the steel sheet conveyance region. The steel sheet conveyance region is a region that the hot-rolled steel sheet occupies on conveyor rolls, a pair of spray nozzles is arranged on both lateral sides in the width direction of the steel sheet conveyance region, and a plurality of spray nozzle pairs are aligned in a conveyance direction of the hot-rolled steel sheet. In regard to a collision region of cooling water jetted from the spray nozzle at the steel sheet conveyance region, a far end in a jet direction is positioned at an end of the steel sheet conveyance region, and a near end is positioned on an inner side of the steel sheet conveyance region. In the spray nozzle pair, the near ends of two collision regions coincide in the width direction to form a meeting.

Abstract: A hot-dip galvanized steel sheet includes a steel sheet and a hot-dip galvanized layer arranged on the steel sheet, in which the Si content and the Al content by mass % of components of the steel sheet satisfy a relationship 0.5<Si+Al<1.0, and a metallographic structure of the steel sheet satisfies a relationship of {(n2)2/3×d2}/{(n1)2/3×d1}×ln(H2/H1)<0.3 when the n1 is the number of a MnS of a surface portion of the steel sheet, the d1 ?m is an average equivalent circle diameter of the MnS in the surface portion of the steel sheet, the H1 GPa is a hardness of a martensite of the surface portion of the steel sheet, the n2 is the number of the MnS of a center portion of the steel sheet, the d2 ?m is an average equivalent circle diameter of the MnS in the center portion of the steel sheet, and the H2 GPa is the hardness of the martensite of the center portion of the steel sheet.

Abstract: A surface treated steel strip according to the present invention includes: a base steel sheet; a zinc phosphate coating film layer made of needle zinc phosphate crystals which are formed in an island shape on a surface of the base steel sheet; and a lubricating coating film layer covering the surface of the base steel sheet and a part of the zinc phosphate coating film layer, and containing at least a lubricating component, in which an area ratio of the zinc phosphate crystals exposed from a surface of the lubricating coating film layer is 25% to 90%.

Abstract: A method of manufacturing a welded structure of a ferritic heat-resistant steel is provided that prevents Type IV damage and that has good on-site operability without adding a high B concentration. The method includes: the step of preparing a base material including 1.0 to 7.0% Cr, less than 0.005% B and other elements; the step of forming an edge on the base material; a pre-weld heat treatment step in which a region located between a surface of the edge and a position distant from the surface of the edge by a pre-weld heat treatment depth of 10 to 50 mm is heated to a temperature of 950 to 1050° C. and is held at this temperature for 10 to 30 minutes; a welding step in which the edge is welded to form the weld metal; and a post-weld heat treatment step in which a region located between the surface of the edge and a position distant therefrom by a distance not smaller than the pre-weld heat treatment depth and not greater than 100 mm is heated to a temperature of 680 to 750° C.

Abstract: Provided is a cooling device, where a hot-finish-rolling mill includes a plurality of nozzles which spray cooling water toward one of or both of upper and lower surfaces of a hot-rolled steel sheet just after rolled by rolling stands, the nozzles are provided on the inside of the upper and lower guides or adjoining to the guides on a downstream side, and a nozzle spray distance changes depending on a position of the nozzle in a rolling direction, wherein a spray angle of the nozzle at a position whose nozzle spray distance is the largest is smaller than a spray angle of the nozzle at a position whose nozzle spray distance is the smallest, and the spray angle of the nozzle becomes the same or smaller as the nozzle spray distance becomes large.

Abstract: A steel sheet according to an aspect of the present invention includes a predetermined chemical composition; in which a metallographic structure in a ¼ t portion contains residual austenite of 4 volume % to 70 volume %; [Mn]?/[Mn]ave>1.5 is satisfied in the ¼ t portion; f?s/f??0.30 and [C]×[Mn]?0.15 are satisfied in the ¼ t portion.

Abstract: A fracture determination device is provided which can predict fracture in an ultra-hard steel material.

Abstract: The present invention has as its object the provision of steel sheet for hot stamping use which is excellent in part strength after hot stamping and delayed fracture resistance comprised of large C content high strength steel sheet in which effective hydrogen traps are formed in the steel material. The steel sheet of the present invention solves this problem by forming Fe—Mn-based composite oxides in the steel sheet and trapping hydrogen at the interfaces of the composite oxides and matrix steel and in the voids around the composite oxides. Specifically, it provides steel sheet for hot stamping use which is comprised of chemical ingredients which contain, by mass %, C: 0.05 to 0.40%, Si: 0.02% or less, Mn: 0.1 to 3%, S: 0.02% or less, P: 0.03% or less, Al: 0.005% or less, Ti: 0.01% or less, N: 0.01% or less, one or both of Cr and Mo in a total of 0.005 to 1%, and O: 0.003 to 0.03% and which have a balance of Fe and unavoidable impurities and which contains average diameter 0.

Abstract: Provided is a steel sheet for soft-nitriding treatment which has a chemical composition consisting of, in mass %, C: more than or equal to 0.02% and less than 0.07%, Si: less than or equal to 0.10%, Mn: 1.1 to 1.8%, P: less than or equal to 0.05%, S: less than or equal to 0.01%, Al: 0.10 to 0.45%, N: less than or equal to 0.01%, Ti: 0.01 to 0.10%, Nb: 0 to 0.1%, Mo: 0 to 0.1%, V: 0 to 0.1%, Cr: 0 to 0.2%, and the balance: Fe and impurities, satisfies [Mn+Al?1.5], and has a total content of Ti, Nb, Mo, V, and Cr present as precipitates in the steel sheet of less than 0.03% in mass %. The steel sheet for soft-nitriding treatment has a metal structure in which a ferrite area ratio is more than or equal to 80%, and a ferrite dislocation density at a position of 50 ?m from a surface of the steel sheet is 1×1014 to 1×1016 m?2.

Abstract: A hot-pressed steel sheet member includes: a specific chemical composition; and a steel microstructure represented by, in area %, ferrite: 10% to 70%, martensite: 30% to 90%, and a total area ratio of ferrite and martensite: 90% to 100%. 90% or more of all Ti in steel precipitates, and a tensile strength of the hot-pressed steel sheet member is 980 MPa or more.

Abstract: A main body (2) has door attaching portions respectively formed on both end sides of a long longitudinal direction thereof and a bending deformation generation portion (3) disposed between the door attaching portions, and the bending deformation generation portion (3) has a groove bottom portion (4), two edge line portions (5a, 5b), two vertical wall portions (6a, 6b), two curved portions (7a, 7b), and two flanges (8a, 8b). There is provided a bead (13) which is formed toward the longitudinal direction of the main body (2) in a part of the groove bottom portion (4) in a manner to project in a shape having a curved surface toward the outside of a cross-sectional shape of the bending deformation generation portion (3) so as to oppose an impact load acting on a door impact beam (1).

Abstract: There is a hot-rolled steel according to one aspect of the invention including predetermined chemical compositions including 0.0001 to 0.0050 mass % of Bi, in which 90 area % or more of a metallographic structure is configured with a ferrite and a pearlite, and an average number density of Mn sulfides extending along a rolling direction and having an aspect ratio exceeding 10 and equal to or smaller than 30, which is measured on a cross section parallel to the rolling direction, is 50 to 200 number/mm2.

Abstract: A hot press device according to the present disclosure includes a first press, a second press, a conveyance device linking the first press and the second press together, and a heating furnace provided within a conveyance range of the conveyance device.

Abstract: Provided is a welding monitoring apparatus that monitors a welding state of a V-convergence region in which a strip-shaped metal sheet is converged in a V-shape, when the metal sheet is cylindrically formed while being conveyed, and both side edges of the metal sheet are heated and melted in a manner of being butted each other while being converged in the V-shape, such that an electric resistance welded steel pipe is manufactured. This welding monitoring apparatus includes an image capturing unit that captures images of a region including the V-convergence region in time series; and an image processing unit that extracts a welding point based on the images captured in time series and detects the presence or absence and a position of irregular arcing at the welding point or on an upstream side of the welding point.

Abstract: This H section includes, as a chemical composition, C, Si, Mn, Nb, V, Ti, and N; in which the H section includes, as a metallographic structure, ferrite of 60 area % to less than 100 area %, an average grain size of this ferrite is 1 ?m to 30 ?m, a thickness of a flange is 20 mm to 140 mm, tensile yield stress is 385 MPa to 530 MPa, and Charpy absorbed energy at ?20° C. is 100 J or more.

Abstract: In a hot pressing method in which a press-formed product (8 or 9) is manufactured by performing hot pressing on a blank material (7) by using a metal mold (2 or 3) having a punch (21 or 31), a die (22 or 31), and an inner pad (23 or 33) which is biased in a state of projecting toward the die (22 or 32), by making a refrigerant flow through a refrigerant path (233 or 333), a surface temperature T of the inner pad (23 or 33) is cooled to a temperature satisfying the following mathematical expression in which an upper limit is set to 100° C., during a period from when removal of the press-formed product (8 or 9) from the metal mold (2 or 3) is completed to when the next blank material (7) is set in the metal mold (2 or 3), T?100×(2.3/t)×(h/100)×(?/30)×(W/2)×S, wherein T: surface temperature of inner pad (23 or 33) (° C.

Abstract: To provide a panel whose surface rigidity can be improved appropriately in accordance with a load. Provided is a panel including: a load point to which a load is applied from the outside; and a protrusion that protrudes from a surface of the panel and is formed continuously or discontinuously around the load point. The protrusion intersects, at a plurality of positions, each of a plurality of virtual straight lines extending radially from the load point.

Abstract: A galvanized steel sheet according to the present invention includes a steel sheet and a galvanizing layer which is formed on a surface of the steel sheet. The steel sheet includes as a chemical component, by mass %, C: more than 0.100% to 0.500%, Si: 0.0001% to less than 0.20%, Mn: more than 0.20% to 3.00%, Al: 3.0% to 10.0%, N: 0.0030% to 0.0100%, Ti: more than 0.100% to 1.000%, P: 0.00001% to 0.0200%, S: 0.00001% to 0.0100% and a remainder including Fe and impurities. The galvanizing layer includes as a chemical composition, by mass %, Fe: 0.01% to 15% and a remainder including Zn and impurities. The galvanized steel sheet has a specific gravity of 5.5 to less than 7.5.