Abstract: A cooling method for a workpiece includes placing entirety of the workpiece in an inner space of a recess provided on a molding surface of a lower mold, pressing or restraining the workpiece by a mold including the lower mold and an upper mold in which a protrusion corresponding to the recess of the lower mold is provided on a molding surface, supplying a liquid coolant to the inner space of the recess through a coolant supply passage provided in at least one of the lower mold and the upper mold by a pump, and discharging air in the inner space of the recess upward through an air escape passage, and cooling the workpiece by immersing the entirety of the workpiece, which has been heated, in the liquid coolant that fills the recess.

Abstract: A structural member 10 includes a hat member 1 and a closing plate 2. The length LY of the tubular portion formed by the hat member 1 and the closing plate 2 is 6 or more times the height H of a pair of side walls 11 and 12. Each of the side walls 11 and 12 includes a high-strength portion 11A or 12A and low-strength portions 11B or 12B. The high-strength portion has a yield strength not less than 500 MPa. The low-strength portions have a yield strength of 60 to 85% of that of the high-strength portion. Each high-strength portion extends a distance not less than (?)H and not more than 3H as measured in the direction in which the ridges extend, and is provided such that the high-strength portions of the pair of side walls face each other. A pair of low-strength portions sandwich the associated high-strength portion.

Abstract: In a mold, at least one of a lower mold and an upper mold includes a coolant supply passage through which a liquid coolant is supplied to an inner space of a recess, and the mold includes an air escape passage through which air in the inner space of the recess is discharged upward.

Abstract: This steel sheet has a base steel sheet, a coated portion, and an exposed portion, the shape of the end edge side of the steel sheet and the end portion on the outer side of the base steel sheet is a protruded curve represented by a curvature radius R1 and R1 is 5 ?m or more.

Abstract: A cooling method for a workpiece includes placing entirety of the workpiece in an inner space of a recess provided on a molding surface of a lower mold, pressing or restraining the workpiece by a mold including the lower mold and an upper mold in which a protrusion corresponding to the recess of the lower mold is provided on a molding surface, supplying a liquid coolant to the inner space of the recess through a coolant supply passage provided in at least one of the lower mold and the upper mold by a pump, and discharging air in the inner space of the recess upward through an air escape passage, and cooling the workpiece by immersing the entirety of the workpiece, which has been heated, in the liquid coolant that fills the recess.

Abstract: This steel sheet includes a first coated portion in which an intermetallic compound layer and an aluminum coating layer are provided on a surface of a base steel sheet in order from the base steel sheet side, a first exposed portion in which the base steel sheet is exposed, and a second coated portion in which the intermetallic compound layer and the aluminum coating layer are provided on the surface of the base steel sheet in order from the base steel sheet side, in which in a first direction which is perpendicular to a thickness direction of the steel sheet and is directed from the first coated portion to one end edge of the steel sheet, the first coated portion, the first exposed portion, the second coated portion, and the end edge of the steel sheet are disposed in this order on one surface of the base steel sheet, at least the first coated portion, the first exposed portion, and the end edge of the steel sheet are disposed in this order on the other surface of the base steel sheet in the first direction,

Abstract: A structural member (10) includes: a hat member (1); and a closing plate (2). The hat member (1) includes: a top-surface portion (1a); a pair of side walls (1b) extending from both edges of the top-surface portion (1a); and flanges (1c). The closing plate (2) is in contact with the flanges (1c). Each of the side walls (1b) includes a low-strength portion (1s) extending from one edge of the side wall (1b) to a position at a distance Sh. The distance Sh is 20 to 40% of the height H of the side wall (1b). The yield strength of the low-strength portion (1s) is 60 to 85% of the yield strength of the side wall (1b) as measured at a position (1mid) of one-half of the height of the side wall (1b).

Abstract: This steel sheet includes a first coated portion in which an intermetallic compound layer and an aluminum coating layer are provided on a surface of a base steel sheet in order from the base steel sheet, the first exposed portion in which the base steel sheet is exposed, and a second coated portion in which the intermetallic compound layer and the aluminum coating layer are provided on the surface of the base steel sheet in order from the base steel sheet, in which in a first direction which is perpendicular to a thickness direction of the steel sheet and is directed from the first coated portion to one end edge of the steel sheet, the first coated portion, the first exposed portion, the second coated portion, and the end edge of the steel sheet are disposed in this order on at least one surface of the base steel sheet, and wherein at least the first coated portion, the first exposed portion, and the end edge of the steel sheet are disposed in this order on the other surface of the base steel sheet in the fir

Abstract: A structural member 10 includes a hat member 1 and a closing plate 2. The length LY of the tubular portion formed by the hat member 1 and the closing plate 2 is 6 or more times the height H of a pair of side walls 11 and 12. Each of the side walls 11 and 12 includes a high-strength portion 11A or 12A and low-strength portions 11B or 12B. The high-strength portion has a yield strength not less than 500 MPa. The low-strength portions have a yield strength of 60 to 85% of that of the high-strength portion. Each high-strength portion extends a distance not less than (?)H and not more than 3H as measured in the direction in which the ridges extend, and is provided such that the high-strength portions of the pair of side walls face each other. A pair of low-strength portions sandwich the associated high-strength portion.

Abstract: A metal pipe includes a pair of side walls facing each other and having a height H, a top portion connected to an upper edge of each of the pair of side walls, and a bottom portion connected to a lower edge of each of the pair of side walls. The metal pipe has a length six times the height H of the side walls or more. Each side wall pair includes a high-strength portion and a pair of low-strength portions, the low strength portions sandwiching the high strength portion. A high-strength portion dimension is not less than ?H and not more than 3H as measured longitudinally of the metal pipe, the high-strength portions forming opposite portions of the side wall pairs. The low-strength portion yield strength is 60 to 85% of that of the high-strength portion, whose yield strength is not less than 500 MPa.

Abstract: A steel sheet heating method that heats a steel sheet (K) to be pressed before hot press molding includes: bringing the steel sheet into a heating furnace (10) including a heater (15) on an inside surface of the heating furnace in a state where the steel sheet is supported in a vertical direction while an unnecessary portion of the steel sheet that becomes unnecessary after molding is fixedly supported by a support member (30); and performing heating at a prescribed temperature in the heating furnace, then taking the steel sheet out of the heating furnace, and after that cutting and removing the unnecessary portion before hot press molding or during hot press molding.

Abstract: A metal pipe 1 has a quadrangular cross section. The metal pipe 1 includes a pair of side walls 11 and 12 facing each other and having a height H, a top portion 13 connected to an upper edge of each of the pair of side walls 11 and 12, and a bottom portion 14 connected to a lower edge of each of the pair of side walls 11 and 12. The metal pipe 1 has a length six times the height H of the side walls 11 and 12 or more. Each of the pair of side walls 11 and 12 includes a high-strength portion 11A or 12A and a pair of low-strength portions 11B or 12B. Each high-strength portion 11A or 12A has a dimension not less than (?) H and not more than 3 H as measured in the longitudinal direction of the metal pipe, the high-strength portions forming opposite portions of the pair of side walls 11 and 12, each high-strength portion having a yield strength not less than 500 MPa.

Abstract: In a mold, at least one of a lower mold and an upper mold includes a coolant supply passage through which a liquid coolant is supplied to an inner space of a recess, and the mold includes an air escape passage through which air in the inner space of the recess is discharged upward.

Abstract: In hot press forming a thin steel sheet K, when cooling the thin steel sheet K by supplying a refrigerant to an ejection hole (27) communicated from a supply path (28) inside a lower mold (12), precooling in which an ejection amount per unit time period of the refrigerant from the ejection hole (27) is suppressed is carried out, and thereafter, main cooling is carried out by increasing the ejection amount per unit time period.

Abstract: A structural member (10) includes: a hat member (1); and a closing plate (2). The hat member (1) includes: a top-surface portion (1a); a pair of side walls (1b) extending from both edges of the top-surface portion (1a); and flanges (1c). The closing plate (2) is in contact with the flanges (1c). Each of the side walls (1b) includes a low-strength portion (1s) extending from one edge of the side wall (1b) to a position at a distance Sh. The distance Sh is 20 to 40% of the height H of the side wall (1b). The yield strength of the low-strength portion (1s) is 60 to 85% of the yield strength of the side wall (1b) as measured at a position (1mid) of one-half of the height of the side wall (1b).

Abstract: This welding method is a flash butt welding method of a pair of track rail steel pieces, having: a preheating process in which electric current is made to flow for a predetermined time in a state in which the welding surfaces of a pair of track rail steel pieces are forcibly brought into contact with each other, and vicinities of the welding surfaces are heated by resistance heating; a former flashing process in which flashing is partially caused in the welding surfaces, and the welding surfaces are heated by the resistance heating and arc heating of the flashing; and a latter flashing process in which the flashing is furthermore caused throughout the entire welding surfaces, and the entire welding surfaces are uniformly heated by the resistance heating and arc heating of the flashing, in which a latter flashing velocity is 2.1 mm/sec to 2.8 mm/sec in the latter flashing process.

Abstract: A steel sheet heating method that heats a steel sheet (K) to be pressed before hot press molding includes: bringing the steel sheet into a heating furnace (10) including a heater (15) on an inside surface of the heating furnace in a state where the steel sheet is supported in a vertical direction while an unnecessary portion of the steel sheet that becomes unnecessary after molding is fixedly supported by a support member (30); and performing heating at a prescribed temperature in the heating furnace, then taking the steel sheet out of the heating furnace, and after that cutting and removing the unnecessary portion before hot press molding or during hot press molding.

Abstract: The present invention provides a hot press molding method for molding a heated metallic plate (K) using a molding die (20, 60) comprising an upper die (21) and a lower die (20). According to the method, the heated metallic plate is arranged between the upper die and the lower die, the upper die and the lower die are brought together, and the metallic plate held between the dies is pressed. After the metallic plate is pressed, a refrigerant in the form of a liquid or mist is supplied via a plurality of supply holes provided to the lower die to a surface of the metallic plate held between the dies, and once the refrigerant has finished being supplied, a gas is sprayed onto the surface of the metallic plate via the plurality of supply holes. It is thereby possible to remove, with maximum speed, liquid refrigerant adhering to the metallic plate when the supply of liquid refrigerant is stopped.

Abstract: In hot press forming a thin steel sheet K, when cooling the thin steel sheet K by supplying a refrigerant to an ejection hole (27) communicated from a supply path (28) inside a lower mold (12), precooling in which an ejection amount per unit time period of the refrigerant from the ejection hole (27) is suppressed is carried out, and thereafter, main cooling is carried out by increasing the ejection amount per unit time period.

Abstract: The present invention provides a hot press molding method for molding a heated metallic plate (K) using a molding die (20, 60) comprising an upper die (21) and a lower die (20). According to the method, the heated metallic plate is arranged between the upper die and the lower die, the upper die and the lower die are brought together, and the metallic plate held between the dies is pressed. After the metallic plate is pressed, a refrigerant in the form of a liquid or mist is supplied via a plurality of supply holes provided to the lower die to a surface of the metallic plate held between the dies, and once the refrigerant has finished being supplied, a gas is sprayed onto the surface of the metallic plate via the plurality of supply holes. It is thereby possible to remove, with maximum speed, liquid refrigerant adhering to the metallic plate when the supply of liquid refrigerant is stopped.