Abstract: A method for manufacturing a hot press formed part, includes: preparing a hot press forming object comprising a single-ply portion and a two-ply portion; heating the hot press forming object to a temperature range from an Ac3 transformation temperature of a base steel sheet of the first coated steel sheet to 1000° C.; press forming the hot press forming object to obtain a formed body, the press forming being started upon temperatures of the single-ply portion and of the two-ply portion being no higher than solidification points of Zn—Ni coating layers of the first and second coated steel sheets and no lower than an Ar3 transformation temperature of the base steel sheet of the first coated steel sheet; and quenching the formed body to thereby obtain a hot press formed part, in which the hot press forming object has a thickness ratio from 1.4 to 5.0.

Abstract: A method of manufacturing a hot press formed part by hot pressing a coated steel sheet that is obtained by forming a Zn-based coating layer on a surface of a steel sheet includes: heating the coated steel sheet to a temperature range of 750° C. or more and 1000° C. or less; cooling a surface of the coated steel sheet; and hot press forming the coated steel sheet under a condition that a surface temperature of the coated steel sheet is 400° C. or less and an average temperature of the coated steel sheet is 500° C. or more or a temperature of a center position of the coated steel sheet in a thickness direction is 530° C. or more.

Abstract: A method of analyzing press-forming of a press-forming material including analyzing press-forming, analyzing springback and analyzing a change in shape of the press-forming material. The analyzing press-forming may include setting an initial temperature distribution for the heated press-forming material and performing a press-forming analysis by combining temperature analysis and structural analysis to obtain shape information, temperature distribution, stress distribution, and strain distribution. The analyzing springback may occur with and without consideration of contact heat transfer between a press-forming tool and the press-forming material. The method may further include modifying the temperature distribution obtained in the analyzing springback and then re-analyzing the change in shape of the press-forming material. The analyzing the change in shape may be performed until a temperature distribution in the press-forming material is within the range of ±5° C.

Abstract: A method for manufacturing a hot press formed part, includes: preparing a hot press forming object comprising a single-ply portion and a two-ply portion; heating the hot press forming object to a temperature range from an Ac3 transformation temperature of a base steel sheet of the first coated steel sheet to 1000° C.; press forming the hot press forming object to obtain a formed body, the press forming being started upon temperatures of the single-ply portion and of the two-ply portion being no higher than solidification points of Zn—Ni coating layers of the first and second coated steel sheets and no lower than an Ar3 transformation temperature of the base steel sheet of the first coated steel sheet; and quenching the formed body to thereby obtain a hot press formed part, in which the hot press forming object has a thickness ratio from 1.4 to 5.0.

Abstract: A method of evaluating a hot stamped part manufactured by hot stamping a coated steel sheet having a Zn—Ni coating layer on a surface of a base steel sheet includes an analysis model setting step, a forming condition setting step, a forming analysis step, and an evaluation step which are performed using a computer, wherein in the evaluation step, a maximum micro-crack depth in the hot stamped part manufactured under a forming condition set in the forming condition setting step is evaluated using a correlation, obtained beforehand, between an equivalent plastic strain in a surface layer of the hot stamped part and the maximum micro-crack depth in the hot stamped part.

Abstract: A method of manufacturing a hot press-formed part by hot pressing a coated steel sheet formed with a Zn—Ni plating layer on a surface of a steel sheet includes: heating the coated steel sheet to a temperature range of Ac3 transformation temperature to 1000° C.; cooling the coated steel sheet to 550-410° C. at a cooling rate of 100° C./s or higher by squeezing the coated steel sheet with a press tool for cooling having flat surfaces configured to contact the coated steel sheet; press forming the coated steel sheet with a tool of press forming to obtain a formed body, the press forming being initiated within 5 seconds after the cooling while the temperature of the coated steel sheet is 550-400° C.; and quenching the formed body, while squeezing the formed body with the tool of press forming and holding at its press bottom dead center, to obtain a hot press-formed part.

Abstract: In manufacturing a hot press forming part by hot pressing, using a tool of press forming, a coated steel sheet, the tool of press forming having a die, a blank holder, and a punch, edges of the coated steel sheet heated to a temperature range of Ac3 transformation temperature to 1000° C. are cooled with the edges squeezed between the die and the blank holder to a temperature of 550° C. or lower and 400° C. or higher at a cooling rate of 100° C./s or higher, press forming is performed so that the press forming is started when the edges reach a temperature of 550° C. or lower and 400° C. or higher, and after the press forming, a formed body is quenched with the formed body held at the press bottom dead center while being squeezed by the tool of press forming.

Abstract: A method of manufacturing a hot press formed part by hot pressing a coated steel sheet that is obtained by forming a Zn-based coating layer on a surface of a steel sheet includes: heating the coated steel sheet to a temperature range of 750° C. or more and 1000° C. or less; cooling a surface of the coated steel sheet; and hot press forming the coated steel sheet under a condition that a surface temperature of the coated steel sheet is 400° C. or less and an average temperature of the coated steel sheet is 500° C. or more or a temperature of a center position of the coated steel sheet in a thickness direction is 530° C. or more.

Abstract: A method of analyzing press-forming of a press-forming material including analyzing press-forming, analyzing springback and analyzing a change in shape of the press-forming material. The analyzing press-forming may include setting an initial temperature distribution for the heated press-forming material and performing a press-forming analysis by combining temperature analysis and structural analysis to obtain shape information, temperature distribution, stress distribution, and strain distribution. The analyzing springback may occur with and without consideration of contact heat transfer between a press-forming tool and the press-forming material. The method may further include modifying the temperature distribution obtained in the analyzing springback and then re-analyzing the change in shape of the press-forming material. The analyzing the change in shape may be performed until a temperature distribution in the press-forming material is within the range of ±5° C.

Abstract: A method forms a steel sheet having a tensile strength of 440 MPa or more into a press-formed part including a flange portion and other portions by press forming. The method includes: heating the steel sheet to a temperature of 400° C. to 700° C.; and press-forming the heated steel sheet by crash forming to obtain a press-formed part such that an average temperature difference among a flange portion and other portions of the press-formed part immediately after the formation is kept within 100° C. Geometric changes such as springback that occur in a panel can thus be suppressed, dimensional accuracy of the panel can be enhanced accordingly, and the desired mechanical properties can easily be obtained in the press-formed part.

Abstract: A method of forming a steel sheet having a tensile strength of 440 MPa or more into a press-formed part including a flange portion and other portions by press forming includes: heating the steel sheet to a temperature of 400° C. to 700° C.; and press-forming the heated steel sheet using draw forming to obtain a press-formed part, with the steel sheet being held at a press bottom dead point in the die for one second to five seconds. Geometric changes such as springback that occur in a panel can thus be suppressed, the dimensional accuracy of the panel can be enhanced, and the desired mechanical properties can easily be obtained in the press-formed part.

Abstract: A press-forming analysis method includes a step of analyzing press forming including setting an initial temperature distribution to a heated press-forming metallic sheet, and acquiring shape information, a temperature distribution, a stress distribution, and a strain distribution before mold release, in which a temperature analysis and a structural analysis are coupled; a step of analyzing springback including conducting a springback analysis based on the shape information, the temperature distribution, the stress distribution, and the acquired strain distribution, and acquiring shape information, a temperature distribution, a stress distribution, and a strain distribution after springback; and a step of analyzing cooling stress including restraining particular nodes based on the shape information, the temperature distribution, the stress distribution, and the acquired strain distribution, and analyzing stress distributions during cooling and after the cooling by coupling a temperature analysis and a structur

Abstract: A method for cooling a hot rolled steel strip including transferring a hot rolled steel strip while ejecting cooling water from a cooling means at a specified ejecting condition; pinching a top end of the hot rolled steel strip by a pinching roll, at the inlet of the cooling means and/or just behind the cooling means and/or at a position on the way of the cooling means; and releasing the hot rolled steel strip sequentially from a pinch roll arranged at an upstream side, concurrently with the arrival of a top end of the steel strip to a tension adding means arranged at a downstream side.

Abstract: An apparatus for cooling a hot rolled steel strip including a transfer means comprising transfer rolls to feed a steel strip which has been hot rolled by a finishing mill; a cooling means for cooling the steel strip; and accompanying rolls arranged with a clearance over the thickness of the steel strip at a position where the accompanying rolls face the transfer rolls through the steel strip to be transferred. The accompanying rolls rotate at nearly an equal peripheral speed as the transfer rolls or at a peripheral speed greater than the transfer speed of the steel strip.

Abstract: A method for cooling a hot rolled steel strip including transferring a hot rolled steel strip while ejecting cooling water from a cooling means at a specified ejecting condition; pinching a top end of the hot rolled steel strip by a pinching roll, at the inlet of the cooling means and/or just behind the cooling means and/or at a position on the way of the cooling means; and releasing the hot rolled steel strip sequentially from a pinch roll arranged at an upstream side, concurrently with the arrival of a top end of the steel strip to a tension adding means arranged at a downstream side.

Abstract: An apparatus for cooling a hot rolled steel strip including a transfer means comprising transfer rolls to feed a steel strip which has been hot rolled by a finishing mill; a cooling means for cooling the steel strip; and accompanying rolls arranged with a clearance over the thickness of the steel strip at a position where the accompanying rolls face the transfer rolls through the steel strip to be transferred. The accompanying rolls rotate at nearly an equal peripheral speed as the transfer rolls or at a peripheral speed greater than the transfer speed of the steel strip.

Abstract: An apparatus for cooling a hot rolled steel strip comprising a transfer means arranged behind a final finishing mill, the transfer means comprising a plurality of transfer rolls for transferring the steel strip; at least one upper surface cooling means arranged at an upper surface side of the transfer means for cooling the steel strip by ejecting cooling water to an upper surface of the steel strip, the upper surface cooling means being capable of moving freely up and down and having a water breaking means at least at an outlet side of the cooling apparatus and at a position corresponding to the transfer rolls; and at least one lower surface cooling means arranged at a lower surface side of the transfer means relative to the upper surface cooling means and the steel strip to be transferred, for cooling the hot strip by ejecting cooling water at a lower surface of the steel strip.

Abstract: An apparatus for cooling a hot rolled steel strip comprising a transfer means arranged behind a final finishing mill, the transfer means comprising a plurality of transfer rolls for transferring the steel strip; at least one upper surface cooling means arranged at an upper surface side of the transfer means for cooling the steel strip by ejecting cooling water to an upper surface of the steel strip, the upper surface cooling means being capable of moving freely up and down and having a water breaking means at least at an outlet side of the cooling apparatus and at a position corresponding to the transfer rolls; and at least one lower surface cooling means arranged at a lower surface side of the transfer means relative to the upper surface cooling means and the steel strip to be transferred, for cooling the hot strip by ejecting cooling water at a lower surface of the steel strip.

Abstract: A lower surface cooling box 12 is arranged between transfer rolls 11 on a runout table 3 and an upper cooling box 14 moving freely is arranged at a position corresponding to the cooling box 12 to eject cooling water to the steel strip symmetrically in the vertical direction. The steel strip passes the center of converge of cooling water from upper and lower surfaces of the steel strip. A water breaking roll 16 is provided elevating freely at least at the outlet side rotating at the same peripheral speed as the transfer rolls and is rotated to lower concurrently with passing of the steel strip top at the cooling apparatus. The upper cooling box is also lowered concurrently to cool the steel strip.

Abstract: A high-quality hot rolled steel sheet is manufactured with a high production efficiency and a low cost, from a long, hot slab, using a combination of continuous casting facilities and a plate reduction press machine.