This torsion beam manufacturing method is for manufacturing a torsion beam including a central portion of which a cross-section orthogonal to a longitudinal direction is a closed cross-section having a substantial V-shape or a substantial U-shape at any position in the longitudinal direction, and a shape changing portion which has a connection region leading to the central portion and including a closed cross-section having a shape different from the shape of the closed cross-section of the central portion. This torsion beam manufacturing method has a compression step of thickening at least the connection region through application of a compression force in the longitudinal direction to at least the connection region of a torsion beam material to obtain the torsion beam, the torsion beam material being formed with the central portion and the shape changing portion.

A method of producing a hot press-formed product, in which a die includes a hard layer having a skewness (Rsk), as measured in a direction from the outside of a die hole toward the inside of the die hole, of from −5.0 to 1.2, and a hardness Hv_Die of from HV 1,000 to 1,550, over the entirety of a region of a steel sheet contact surface that is adjacent to a die shoulder portion. The steel sheet contact surface is a surface located outside of the die hole and configured to contact a plated steel sheet (a plated steel sheet including at least one kind of plating layer selected from the group consisting of a hot-dip galvanizing layer and a zinc nickel plating layer) that is to be subjected to hot press forming.

A method of producing a hot press-formed product, in which a die includes a hard layer having a skewness (Rsk), as measured in a direction from the outside of a die hole toward the inside of the die hole, of from −5.0 to 1.2, and a hardness Hv_Die of from HV 1,000 to 1,550, over the entirety of a region of a steel sheet contact surface that is adjacent to a die shoulder portion. The steel sheet contact surface is a surface located outside of the die hole and configured to contact a plated steel sheet (a plated steel sheet including at least one kind of plating layer selected from the group consisting of a hot-dip galvanizing layer and a zinc nickel plating layer) that is to be subjected to hot press forming.

A press forming method for controlling a shape change of a press formed part over time after the press formed part springs back at a moment of a release from a press-forming die includes: a press forming step of press forming a metal sheet into the press formed part by using the press-forming die; a die releasing step of releasing the press formed part, which is press-formed, from the press-forming die; and a post-release die holding step of holding the released press formed part in a forming bottom dead center shape for 30 minutes or more by using the press-forming die.

A press forming method for controlling a shape change of a press formed part over time after the press formed part springs back at a moment of a release from a press-forming die includes: a press forming step of press forming a metal sheet into the press formed part by using the press-forming die; a die releasing step of releasing the press formed part, which is press-formed, from the press-forming die; and a post-release die holding step of holding the released press formed part in a forming bottom dead center shape for 30 minutes or more by using the press-forming die.

In this press forming method, a formed product which has a hat-shaped cross section, and which is provided with a top surface portion, an outward corner portion, a vertical wall portion, an inward corner portion, and a flange portion, is formed. In a draw forming step, an intermediate formed product 8 including a protruding portion 81 and a recessed portion 83 is formed. The curvature of the protruding portion 81 and the recessed portion 83 are greater than those of the outward corner portion and the inward corner portion, and the cross-sectional shape of the protruding portion 81 is caused to bulge further toward the top surface portion side in a pressing direction F than the outward corner portion. In a restrike forming step, the outward corner portion and the inward corner portion are formed by pushing the protruding portion 81 down in the pressing direction F.

In this press forming method, a formed product which has a hat-shaped cross section, and which is provided with a top surface portion, an outward corner portion, a vertical wall portion, an inward corner portion, and a flange portion, is formed. In a draw forming step, an intermediate formed product 8 including a protruding portion 81 and a recessed portion 83 is formed. The curvature of the protruding portion 81 and the recessed portion 83 are greater than those of the outward corner portion and the inward corner portion, and the cross-sectional shape of the protruding portion 81 is caused to bulge further toward the top surface portion side in a pressing direction F than the outward corner portion. In a restrike forming step, the outward corner portion and the inward corner portion are formed by pushing the protruding portion 81 down in the pressing direction F.

A manufacturing device manufactures a component having a hat-shaped section as a pad and a punch sandwiching a center portion of a metal plate, and a die and a holder sandwiching both side portions of the metal plate are moved relative to each other in the upper-lower direction. The manufacturing device includes the die, the pad provided inside an opening of the die so that the pad is able to move relative to the die, the punch arranged to face the pad in the upper-lower direction, the holder arranged around the punch so as to face the die in the upper-lower direction and be able to move downwardly, and a locking block provided on the holder. The locking block is moved from a non-facing position to a facing position and inserted between the pad and the holder after mold closing and before mold opening.

A manufacturing device manufactures a component having a hat-shaped section as a pad and a punch sandwiching a center portion of a metal plate, and a die and a holder sandwiching both side portions of the metal plate are moved relative to each other in the upper-lower direction. The manufacturing device includes the die, the pad provided inside an opening of the die so that the pad is able to move relative to the die, the punch arranged to face the pad in the upper-lower direction, the holder arranged around the punch so as to face the die in the upper-lower direction and be able to move downwardly, and a locking block provided on the holder. The locking block is moved from a non-facing position to a facing position and inserted between the pad and the holder after mold closing and before mold opening.

A shape change prediction method for a press formed part for predicting a shape change of the press formed part with a lapse of time units after springback at a moment of a release from a die includes: a shape/residual stress immediately after springback acquisition step of acquiring a shape and a residual stress of the press formed part immediately after the springback by a springback analysis of the press formed part; a residual stress relaxation/reduction setting step of setting a value of a residual stress relaxed and reduced from the acquired residual stress to the press formed part immediately after the springback; and a shape analysis step of determining a shape, in which moments of force are balanced, for the press formed part to which the value of the relaxed and reduced residual stress is set.