Abstract: A cooling device and a cooling method for a hot strip allow uniform and stable cooling of the strip at a high cooling rate when supplying the coolant to the upper surface of the hot strip. The cooling device includes an upper header unit 21 for supplying a rod-like flow to the upper surface of the strip 10. The upper header unit 21 is formed of the first upper header group including plural first upper headers 21a arranged in a conveying direction and a second upper header group including plural second upper headers 21b arranged in the conveying direction. The cooling device is provided with an ON-OFF mechanism 30 to allow each of the upper headers 21a and 21b of the first and the second upper header groups to independently execute the ON-OFF control (start/end injection control) of an injection (feeding) of the rod-like flow.

Abstract: A vaso-occlusive device includes a coil made from coil wire, wherein the coil wire includes a core containing a core material having a first electrical potential covered by a coating containing a coating material having a second electrical potential, wherein the second electrical potential is less than the first electrical potential. A method of manufacturing a vaso-occlusive device includes cladding a core with a magnesium containing coating to form a wire, wrapping the wire around a mandrel to form a coil, and heat-setting the coiled wire. A method of occluding a body cavity with a vaso-occlusive device includes delivering the vaso-occlusive device to a body cavity and inducing a reduction reaction in the body cavity and adjacent the vaso-occlusive device, wherein the reduction reaction reduces infections and promotes cell proliferation in the body cavity.

Abstract: A method of producing a superalloy gun barrel includes providing a tubular workpiece made of a cobalt-based superalloy material, the workpiece having at least about 30% by weight of fcc phase and having an inner diameter and an outer diameter. The method further includes placing the workpiece on a mandrel such that the inner diameter is adjacent to the mandrel and compressing the outer diameter of the workpiece at a temperature below a recrystallization temperature of the workpiece using a combination of axial and radial forces so that the mandrel contacts the inner diameter and imparts a compressive hoop stress to the inner diameter of the workpiece.

Abstract: A hot formed part of high-strength steel includes a body having an opening and formed in one piece with at least one tab in the form of a tongue projecting into the opening for holding a connection piece captive on the body. The tab thus is formed in one piece with the hot formed part and is produced jointly with the openings during manufacture of the hot formed part in the hot forming process.

Abstract: A forging die heating or preheating apparatus comprises a burner head comprising a plurality of flame ports. The burner head is oriented to compliment an orientation of at least a region of a forging surface of a forging die and is configured to receive and combust a supply of an oxidizing gas and a supply of a fuel and produce flames at the flame ports. The plurality of flame ports are configured to impinge the flames onto the forging surface of the forging die to substantially uniformly heat at least the region of the forging surface of the forging die.

Abstract: A hardenable steel sheet is treated with press-forming by means of a die. The method is comprised of: heating the steel sheet to a temperature of an Ac3 point or higher; carrying out a primary press on the heated steel sheet so as to give a local strain to a limited part of the steel sheet; keeping the steel sheet in a state apart from the die shortly after the primary press; and carrying out a press on the steel sheet kept in the state and retain the steel sheet in close contact with the die.

Abstract: In a method of making a tubular structural part for a motor vehicle, a metal plate is contoured and preformed in at least one shaping step into a tubular body. Subsequently, the tubular body is end-formed into the structural part by internal high-pressure application while free contact regions snugly bear upon one another. The structural part is at least partially heated and quenched in a holding tool acted upon with a coolant.

Abstract: A bent member having excellent dimensional accuracy is manufactured by stably forming a high temperature portion uniformly in the circumferential direction of a steel tube and in a narrow region in the axial direction of the steel. The bent member is manufactured by supporting a steel tube at a first position while feeding it, performing induction heating of the steel tube at a second position with an induction heating coil, cooling the steel tube at a third position to form a high temperature portion which moves in the axial direction of the steel tube, and three-dimensionally varying the position of a gripping mechanism for the steel tube in a region to apply a bending moment to the high temperature portion.

Abstract: A hot-pressed member includes a steel sheet, a Ni-diffusion region present in a surface layer of the steel sheet, and an intermetallic compound layer and a ZnO layer which are provided in order on the Ni-diffusion region, the intermetallic compound layer corresponding to a ? phase present in a phase equilibrium diagram of a Zn—Ni alloy, wherein a spontaneous immersion potential indicated in a 0.5 M NaCl aqueous air-saturated solution at 25° C.±5° C. is ?600 to ?360 mV based on a standard hydrogen electrode.

Abstract: A torsion portion extending in a vehicle width direction and having a first cross-sectional area, shoulder portions located at both ends of the torsion portion and having a second cross-sectional area larger than the first cross-sectional area and arm portions extending from the shoulder portions in a front and back direction of a vehicle, respectively and having the first cross-sectional area, so that even when a hollow member is used for weight saving, can be realized by design and manufacturing method facilitating making uniform principal stress as in a solid member.

Abstract: The invention relates to a process for producing sheet steel components having regions of differing ductility, in which either a sheet metal plate composed of a hardenable steel alloy is used to produce a component by deep-drawing and the deep-drawn component is then at least partially austenitized by a heat treatment and subsequently quench hardened in a die or the plate is at least partially austenitized by a heat treatment and shaped in the hot state, and is quench hardened during or after this, with the sheet metal plate having a zinc-based cathodic corrosion protection coating, characterized in that in regions of a desired higher ductility of the component, at least one additional sheet is attached to the plate, situated so that during the heat treatment, the plate is heated to a lesser degree there than in the remaining region.

Abstract: A thermo-mechanical treatment process is disclosed. A nickel-base alloy workpiece is heated in a first heating step to a temperature greater than the M23C6 carbide solvus temperature of the nickel-base alloy. The nickel-base alloy workpiece is worked in a first working step to a reduction in area of 20% to 70%. The nickel-base alloy workpiece is at a temperature greater than the M23C6 carbide solvus temperature when the first working step begins. The nickel-base alloy workpiece is heated in a second working step to a temperature greater than 1700° F. (926° C.) and less than the M23C6 carbide solvus temperature of the nickel-base alloy. The nickel-base alloy workpiece is not permitted to cool to ambient temperature between completion of the first working step and the beginning of the second heating step. The nickel-base alloy workpiece is worked to a second reduction in area of 20% to 70%. The nickel-base alloy workpiece is at a temperature greater than 1700° F. (926° C.

Abstract: Provided are a steel pipe for a linepipe having a heavy wall thickness and excellent fracture toughness in a base material, and methods of producing the same. A welded heat affected zone is achieved by suppressing lowering of yield stress caused by a Bauschinger effect by optimizing the metal microstructure of a steel plate. A steel pipe has a composition which contains by mass % 0.03 to 0.08% C, 0.10% or less Si, 1.00 to 2.00% Mn, 0.010% or less P, 0.0030% or less S, 0.06% or less Al, 0.005 to 0.020% Nb, 0.005 to 0.025% Ti, 0.0010 to 0.0060% N, and Fe and unavoidable impurities as a balance. Ti(%)/N(%) is a value which falls within a range of 2 to 4, and a Ceq value is 0.30 or more.

Abstract: A device and a method for cooling a hot strip capable of uniformly cooling the hot-rolled steel strip from the leading end to the trailing end thereof during cooling of the steel strip using cooling water are provided. A cooling device 10 includes a plurality of tubular nozzles 15 inclined so as to eject rod-like flows of cooling water to a steel strip 12 at an ejecting angle ? in a traveling direction of the steel strip 12 and a pinch roller 11 disposed downstream of the tubular nozzles, the steel strip 12 to be nipped between the pinch roller 11 and a table roller 8.

Abstract: A crucible for growing crystals, the crucible being formed from Molybdenum and Rhenium. A crucible for growing crystals, the crucible being formed from a metal selected from Group V of the Periodic Table of the Elements. A crucible for growing crystals, the crucible comprising a body and a layer formed on at least a portion of the body, the layer being formed out of Molybdenum.

Abstract: Coated steel having a well defined and uniform thickness is useful and advantageous for preparing products by hot stamping. Products prepared by hot stamping such a steel are particularly advantageous when subjected to a subsequent spot welding step.

Abstract: Stamping tool, in particular a cutting rule, for dividing or perforating flat materials, and production of the tool. To create a stamping tool with improved properties, in particular with an automatic leveling in a flat-bed stamping machine and/or in a rotation stamping machine, embodiments provide that from a thermally treated and/or quenched and tempered steel strip, shaped on the narrow sides with, on the one hand, a back part with a convex contour in cross section or a contour composed of several projecting convex regions, which contour has recesses in some places transverse to the longitudinal extension and perpendicular to the lateral surfaces, shaped in a chipless manner by cold forming or embossing with free spreading of the material, wherein the extent of the spreading is smaller than the steel strip thickness and the undeformed regions between the recesses can be plastically deformed with a startup of the tool.

Abstract: The invention relates to a method and a device for producing coils (9) with longitudinal sections (9a) and narrow deflection bends (9b) by winding wires (8) on winding mandrels (4) with complementary cross sections with the supply of heating energy and subsequent fixing by cooling. To attain the object to rule out the spring rebounds of the coils (9) at the points of narrowest radii of curvature as far as possible and to produce coils (9) with high precision with high efficiency, it is proposed according to the invention that the heating energy is brought to act on the coils (9) at least mainly in the region of the narrow deflection bends (9b). This can be carried out by the targeted application of heating gases or hot air, laser radiation, contact heating, plasma radiation and ultrasound.

Abstract: A method of manufacturing a hot press-hardened component comprises the following production steps: a) providing a steel product produced at least in sections from a stainless steel comprising of the following composition (specified in % wt.) C: 0.010-1.200%, P: up to 0.1%, S: up to 0.1%, Si: 0.10-1.5%, Cr: 10.5-20.0% and optionally one or more elements from the group “Mn, Mo, Ni, Cu, N, Ti, Nb, B, V, Al, Ca, As, Sn, Sb, Pb, Bi, H” with the requirement Mn: 0.10-3.0%, Mo: 0.05-2.50%, Ni: 0.05-8.50%, Cu: 0.050-3.00%, N: 0.01-0.2%, Ti: up to 0.02%, Nb: up to 0.1%, B: up to 0.1%, V: up to 0.2%, Al: 0.001-1.50%, Ca: 0.0005-0.003%, As: 0.003-0.015%, Sn: 0.003-0.01%, Sb: 0.002-0.01%, Pb: up to 0.01%, Bi: up to 0.01%, H: up to 0.

Abstract: A method for producing a structural sheet metal component formed from an aluminum alloy for a motor vehicle includes providing an aluminum sheet blank in a state T4 or T5 or T6 or T7, heating the aluminum sheet blank to a heating temperature between 100° C. and 450° C., forming the aluminum sheet blank to a structural sheet metal component, and heat post-treatment of the formed structural sheet metal component.

Abstract: An alloy is provided which consists of Fe100-a-b-c-d-x-y-zCuaNbbMcTdSixByZz and up to 1 at % impurities, M being one or more of the elements Mo, Ta and Zr, T being one or more of the elements V, Mn, Cr, Co and Ni, Z being one or more of the elements C, P and Ge, 0 at %?a<1.5 at %, 0 at %?b<2 at %, 0 at %?(b+c)<2 at %, 0 at %?d<5 at %, 10 at %<x<18 at %, 5 at %<y<11 at % and 0 at %?z<2 at %. The alloy is configured in tape form and has a nanocrystalline structure in which at least 50 vol % of the grains have an average size of less than 100 nm, a hysteresis loop with a central linear region, a remanence ratio Jr/Js of <0.1 and a coercive field strength Hc to anisotropic field strength Ha ratio of <10%.

Abstract: When shaping a metal blank (P), the blank (P) is heated to a predetermined temperature, is then cooled using a cooling device (10), and is subsequently placed in a press and is shaped. According to the invention, at least one plate surface, and particularly both plate surfaces, of the blank (P) is/are brought in direct contact with a cooling element (16, 19) in the cooling device (10), and the blank is clamped especially between said cooling elements (16, 19). A corresponding cooling device for a metal blank (P) comprises a first cooling element (16) and a second cooling element (19) which are adjustable relative to each other and between which the blank (P) can be clamped.

Abstract: UHC lightweight structural steel with improved scaling resistance, comprising the composition in % by weight C: 1 to 1.6, Al: 5 to 10, Cr: 0.5 to 3, Si: 0.1 to 2.8, the remainder iron and customary impurities accompanying steel, and a method for producing components hot-formed from this in air, wherein hot-forming temperatures of from 800 to 1050° C. are used, depending on the Si content.

Abstract: A method of thermal forming of refractory alloy suture needles is disclosed. Needle blanks made from refractory alloys are used to form surgical needles, which are heated to a temperature above the ductile to brittle transition temperature but below the recrystallization temperature of the refractory alloy. The heated needle blanks are then mechanically formed into a surgical needle.

Abstract: A hot-strip cooling device and a cooling method are provided wherein uniform cooling of a hot-rolled steel strip using coolant is possible from the leading end to the trailing end of the steel strip. A cooling device (10) includes a plurality of round nozzles (15) disposed obliquely in such a manner as to eject rod-like flows of coolant at an ejection angle ? toward the upstream side in a direction in which a steel strip (12) travels, and a pinch roll (11) disposed on the upstream side with respect to the round nozzles (15) and configured to pinch the steel strip (12) in combination with a roller table (8).

Abstract: Collector plates made of bulk-solidifying amorphous alloys, the bulk-solidifying amorphous alloys providing ruggedness, lightweight structure, excellent resistance to chemical and environmental effects, and low-cost manufacturing, and methods of making such collector plates from such bulk-solidifying amorphous alloys are provided.

Abstract: The invention provides a method for producing a pearlitic rail by rough hot rolling and finish hot rolling a billet. In the finish hot rolling, the billet is rolled at a rail head surface temperature in a range of not higher than 900° C. to not lower than the Ar3 transformation point or Arcm transformation point to produce a head cumulative reduction of area of not less than 20%, where the reaction force ratio of the finish rolling is not less than 1.25. The finish hot rolled rail head surface is subjected to accelerated cooling or spontaneous cooling to a temperature of 550° C. or less at a cooling rate of 2 to 30° C./seconds, thereby refining the rail head structure to attain a hardness within a predetermined range, and improving rail wear resistance and ductility.

Abstract: A method of correcting the shape of a brittle cast component such as a low pressure turbine blade. The method includes steps of placing the component against a creep mold having a surface defining the desired profile of the component and HIP treating it to creep deform the component to the desired shape whilst consolidating it and removing gas and shrinkage porosity.

Abstract: Novel molds and methods for Bulk Metallic Glass (BMG) molding using carbon templates obtained from pyrolyzed materials are provided. The method employs the Carbon MEMS (C-MEMS) technique to derive molds of different geometries and dimensions. The resultant carbon structures are stable at very high temperatures and have sufficient mechanical strength to be used as master molds for the thermoplastic forming of BMGs.

Abstract: The present invention provides a learning method of rolling load prediction which uses a prediction error of a rolling load at an actual pass of a stock in hot rolling to correct a predicted value of rolling load at a subsequent rolling pass. The method comprises changing a gain for multiplying with the prediction error of the rolling load at the actual pass in accordance with a thickness of the stock to thereby set the learning coefficient of the rolling load prediction and improve the precision of the prediction.

Abstract: A component of an air-hardenable steel composed of (contents in mass %): C<0.20; Al<0.08; Si<1.00; Mn 1.20 to <2.50; P<0.020; S<0.015; N<0.0150; Cr 0.30 to <1.5; Mo 0.10 to <0.80; Ti 0.010 to <0.050; V 0.03 to <0.20; B 0.0015 to <0.0060, with the remainder being iron including the usual elements present in steel, is produced by heating a hot- or cold-rolled steel sheet or steel tube section to a temperature of ?blank=800 to 1050° C. and then forming the sheet or tube into a component in a forming tool. After removal from the tool, the component is cooled down in air while the component still has a temperature above ?removal=200° C. and below 800° C. The component achieves the required mechanical properties during air-cooling.

Abstract: A method for near net shape forging a titanium component includes heating a titanium billet to a temperature in the alpha-beta temperature range and extruding the titanium billet into a first die having a temperature approximately 500° F. below the temperature of the titanium billet. A system for near net shape forging a titanium component includes a titanium billet having a temperature in the alpha-beta temperature range and a punch in contact with the titanium billet. A first die proximate to the titanium billet for receiving the titanium billet has a temperature approximately 500° F. below the temperature of the titanium billet.

Abstract: The invention relates to a method for producing a shaped part from an aluminum sheet comprising an aluminum alloy, in particular an aluminum alloy of the 5000 series, wherein at least one aluminum sheet is introduced in a forming tool and cold-formed by the same, and in a further step, or in further steps, the cold-formed aluminum sheet is heated at least once at least in some regions and at least once further formed. In order to create advantageous conditions for the method, it is proposed for the heated aluminum sheet to be subjected to the further forming step even before a temperature has been reached which the aluminum sheet has during the cold forming thereof.

Abstract: A system and a method of processing an F-temper aluminum alloy. An F-temper aluminum alloy blank may be heated and positioned in the die set such that the blank does not touch the die set. The blank may be formed into a part and quenched when the die set is closed.

Abstract: In a plated steel sheet having an aluminum-plating layer comprising at least Al formed on one side or both sides of the steel sheet, there is provided a plated steel sheet which, owing to the presence of a surface coating layer containing a compound having wurtzite crystal structure on the aluminum-plating layer, has excellent lubricity, prevents the plating thickness from becoming uneven during heating, and can improve formability and productivity in hot stamping, and a method of hot-stamping the plated steel sheet.

Abstract: The invention relates to a method for producing a metal component, wherein a raw material (4, 34, 42, 74) is provided, the raw material (4, 34, 42, 74) is stamped and is further processed following the stamping process to form a component (90, 108, 114). The component (90, 108, 114) has at least partially stamped areas (16, 36, 48, 98), and the raw material (4, 34, 42, 74) is hot-stamped. The invention further relates to the use of a hot-stamped metal component, which is preferably produced using a method according to the invention, in a motor vehicle body, in particular as a reinforcing element in a B-column (114), a sill, or a longitudinal beam.

Abstract: In a method, a blank of unhardened steel sheet is subjected in a press tool to a hot forming and press-hardening process to produce a structural part. After press-hardening, at least one linear zone of the structural part is heat treated in order to increase ductility and reduce strength in the linear zone in relation to adjacent regions of the structural part. After heat treatment, a bending or cutting operation is carried out on the structural part along the linear zone.

Abstract: First, a heat pipe containing a work fluid is provided. The heat pipe is not pressed until the work fluid turns into a vapor phase so as to form a desired shape. The method can be employed to shape a round cross-section of a heat pipe into an oblate one.

Abstract: Metal foil for the catalytic production of hydrogen, having the following chemical composition (in % by weight): C 0.001 to 0.5%; S max. 0.008%; N 0.1 to 0.3%; Cr 24 to 28%; Ni 30 to 33%; Mn 1.0 to 2.0%; Si 0.005 to 0.2%; Mo 6.0 to 7.5%; Ti max. 0.05%; Nb max. 0.05%; Cu 0.8 to 2.0%; P max. 0.025%; AI max. 0.2%; Cer composition metal 0.01 to 0.1%; W max. 0.5%; Co max. 0.5%; B 0.001 to 0.05%; the remainder being Fe and production-related impurities.

Abstract: A blank cut from a strip of hardenable hot-formed steel is heated in a furnace to a temperature which is smaller than an Ac3 transformation point in an iron carbon diagram. A first region of the blank is then heated in a conductive heating station to a temperature above the Ac3 transformation point and subsequently hardened in a hot forming and hardening tool to produce a steel part with at least two microstructured regions of different ductility.

Abstract: A lightweight hollow member having a high strength such as at least 780 MPa, a complicated shape which can be applied to automotive parts, a high stiffness, and excellent impact properties, and a manufacturing apparatus and method which can form the hollow member by simple steps and which use relatively small and inexpensive forming equipment are provided. The manufacturing apparatus 10 has a feed unit 11 which feeds a hollow steel material being worked 20 having a closed transverse cross-sectional shape in its lengthwise direction, a support unit 12 which supports the material being worked 20 while it is being fed at a first position A, a heating unit 13 which heats the material being worked 20 at a second position B, a transverse cross-sectional shape modifying unit 14 which carries out working to modify the transverse cross-sectional shape of the material being worked 20 at a third position C, and a cooling unit 15 which cools the material being worked 20 at a fourth position D.

Abstract: Elastic metal rings are pushed between plural shelf members which have an opening, are provided parallel to each other in a vertical direction and are spaced a predetermined interval from each other, the opening having an inner periphery of which total sides are longer than a periphery of each elastic metal ring. Each of all the metal rings is deformed into an approximately polygonal shape, which allows all the metal rings to pass through the opening, from arrangement condition of the metal rings, and all the metal rings are pressed and held from insides thereof and are extracted from the opening. A heat treatment jig, which has the same opening as that of the shelf member and enables the metal rings to be mounted parallel to each other in a vertical direction and to be spaced the above predetermined interval from each other, is used.

Abstract: Provided are a coated steel sheet, a hot press formed product using the steel sheet, and a producing method thereof. Conditions for hot-dip coating bath are optimized when an aluminum-coated steel sheet is produced using a hot rolled steel sheet or a cold rolled steel sheet, and processes are controlled during production of a hot press formed product from the steel sheet, thereby forming a coating layer having a high ratio of (Fe3Al+FeAl) compound layer on the surface of the steel sheet. In cases where the (Fe3Al+FeAl) compound layer has an appropriate occupancy ratio with respect to the whole thickness of the coating layer, good resistance against crack and corrosion can be achieved to improve a local corrosion resistance of the hot press formed product, particularly, a pitting corrosion resistance. Therefore, high-quality hot press formed products can be produced with high productivity and lower costs.

Abstract: A plug material having a prescribed shape is prepared, the prepared plug material is thermally treated in a heat treatment atmosphere that contains at least 1.0 vol. % oxygen at a heat treatment temperature of at least 950° C. and less than 1050° C. and thus a plug having an oxide scale layer 30 on the surface is manufactured. According to the manufacturing method, pores PO that extend along the surface SF of the plug material are formed under outer scale layer 20 in the oxide scale layer 30, which allows cracks to be more easily propagated in the outer scale layer 20. Therefore, the outer scale layer 20 is more easily peeled off than the conventional one.

Abstract: A feed device for a superplastic press-forming press has a slide that moves vertically and a base between which is held a tool having a cover and a bottom die enclosing a forming tool, which includes at least one heating shuttle to transport the bottom die, equipped with the forming tool and a cover, with the heating shuttle adapted to complete the press and constitute the base of the press during a hot-press forming operation.

Abstract: A method for surface treating a mandrel bar used for hot rolling of high-alloy seamless steel pipe is provided. The method includes heat treating the mandrel bar to develop a scale, and after heat treatment, rolling ordinary steel comprising 8% or less of chromium for at least 50 passes. This achieves a mandrel bar for rolling high-alloy steel possessing both durability and superior resistance to seizure.

Abstract: The invention relates to a process for making a hot stamped coated steel sheet product, comprising the steps of pre-coating a steel strip or sheet with aluminium- or aluminium alloy, cutting said pre-coated steel strip or sheet to obtain a pre-coated steel blank, heating the blank in a furnace preheated to a temperature and during a time defined by diagram according to thickness, at a heating rate Vc between 20 and 700° C. comprised between 4 and 12° C./s and at a heating rate Vc? between 500 and 700° C. comprised between 1.5 and 6° C./s, to obtain a heated blank; then transferring said heated blank to a die, hot stamping the heated blank in the die obtain a hot stamped steel sheet product, cooling at a mean rate Vr between the exit of the heated blank from the furnace, down to 400° C., of at least 30° C./s.

Abstract: Computer-implemented processes for making refractory metal pots, including: cutting an a refractory metal ingot into a first workpiece; subjecting the first workpiece to multiple upset forgings, annealings in a vacuum or inert gas to a temperature sufficiently high to cause at least partial recrystallization, forging-backs, and rollings to form a plate; wherein the forged, annealed workpiece undergoes a reduction in thickness after at least one rolling pass and is turned between at least one pass, to form the plate; and deep drawing the plate to form a pot; wherein dimensions of at least one workpiece or plate suitable for processing into a pot are pre-determined with a computer-implemented finite element modeling assessment method.

Abstract: A steel part with regions of different ductility is made by first loading the part onto a heatable rack and then heating the rack with the part on it in a furnace to a temperature above the AC3 point of the part. The part is then removed from the rack and loaded while still above the AC3 point into a press where it is shaped and hardened. In the press the part is engaged by tools that deform it and that cool it quickly to well below the AC3 point. Finally, before the rack has cooled substantially, the shaped and hardened part is taken out of the press and placed on the rack with predetermined regions of the part in heat-conducting engagement with the rack such that the ductility of the predetermined regions is increased by transfer of the residual heat from the rack to the predetermined regions.

Abstract: A method for manufacturing a high strength hot rolled steel sheet includes heating a slab to a temperature in the range of 1150 to 1300° C.; hot rolling the slab with a finishing rolling temperature being in the range of 800 to 1000° C.; cooling the steel sheet at a mean cooling rate of 30° C./s or higher to a cooling termination temperature in the range of 525 to 625° C.; suspending cooling for a time period in the range of 3 to 10 seconds; cooling the steel sheet in such a manner that cooling of the steel sheet is nucleate boiling; and coiling the steel sheet at a temperature in the range of 400 to 550° C.