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 Ac.sub.3 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.

The invention relates to a method for producing a composite sheet metal part having at least one metallic region from a composite sheet metal blank which has two outer cover sheets of metal and at least one layer which is arranged between the cover sheets and consists of plastics material. The invention provides an apparatus and method by which complex formed composite sheet metal parts can easily be produced in a few steps and which still have metallic regions which can be used for joining to further parts.

A press-formed product includes a body having a transverse cross section including a bottom portion and a shoulder portion contiguous to the bottom portion through an R end. In the transverse cross section, a first region from the R end to a position a distance away in a bottom portion extending direction, and a second region which is part of the bottom portion and is contiguous to the first region have a work-hardening distribution introduced by press-forming. The work-hardening distribution has an average hardness Hv1 of an area of the first region from a steel sheet surface to a depth obtained by multiplying a steel sheet thickness by 0.2 and an average hardness Hv2 of an area of the second region from the steel sheet surface to a position obtained by multiplying the steel sheet thickness by 0.2 to satisfy a relationship of Hv1>1.05×Hv2.

A press-formed product includes a body having a transverse cross section including a bottom portion and a shoulder portion contiguous to the bottom portion through an R end. In the transverse cross section, a first region from the R end to a position a distance away in a bottom portion extending direction, and a second region which is part of the bottom portion and is contiguous to the first region have a work-hardening distribution introduced by press-forming. The work-hardening distribution has an average hardness Hv1 of an area of the first region from a steel sheet surface to a depth obtained by multiplying a steel sheet thickness by 0.2 and an average hardness Hv2 of an area of the second region from the steel sheet surface to a position obtained by multiplying the steel sheet thickness by 0.2 to satisfy a relationship of Hv1>1.05×Hv2.

The top plate section of the metal stock is pressed and clamped against a punch by a pad, a portion that will be at the outside of the L shaped curve is pressed and camped against a die by a blank holder, a bender is moved, and a vertical wall portion at the inside of the L shaped curved of the metal stock sheet and the flange portion joined to the vertical wall at the inside of the L shaped curve are molded. The metal stock sheet is moved in the direction toward the blank holder while the metal stock sheet being pressed and clamped, and a vertical wall portion at the outside of the L shaped curve of the L shaped hat shaped cross-section and the flange portion joined to the vertical wall at the outside of the L shaped curve are molded.

The top plate section of the metal stock is pressed and clamped against a punch by a pad, a portion that will be at the outside of the L shaped curve is pressed and camped against a die by a blank holder, a bender is moved, and a vertical wall portion at the inside of the L shaped curved of the metal stock sheet and the flange portion joined to the vertical wall at the inside of the L shaped curve are molded. The metal stock sheet is moved in the direction toward the blank holder while the metal stock sheet being pressed and clamped, and a vertical wall portion at the outside of the L shaped curve of the L shaped hat shaped cross-section and the flange portion joined to the vertical wall at the outside of the L shaped curve are molded.

A method and forming tool for hot forming and press hardening plate-shaped or preformed workpieces of sheet steel, wherein the workpiece is heated to a temperature above the austenitisation temperature and is then formed and quenched in a cooled forming tool having a punch and a female mold, wherein the female mold is coated in its drawing edge region with material in a material-uniting manner and/or is provided there with at least one insert part having a thermal conductivity at least 10 W/(m*K) lower than the thermal conductivity of the portion of the female mold adjacent to the drawing edge region and comes into contact with the workpiece when said workpiece is being hot formed and press hardened, the surface of the material having a transverse dimension within the range of 1.6 times to 10 times the positive radius of the female mold.

The present invention suppresses deterioration in the corrosion resistance of a worked portion resulting from working cracks in a Zn-based plated layer (3) in a workpiece (2) formed into a predetermined shape by performing plastic working on a Zn-based plated steel sheet (1) coated with a Zn-containing metal as a raw material. That is, plastic working is performed on a raw material that is a Zn-based plated steel sheet (1) to obtain a workpiece (2) having a predetermined shape, and thereafter, pressurization processing is performed on a worked portion in a sheet thickness direction to deform the plated metal, thus decreasing the width of working cracks in the plated metal. Accordingly, it is possible to reduce the deterioration in the corrosion resistance of the worked portion of the Zn-based plated workpiece.

The present invention suppresses deterioration in the corrosion resistance of a worked portion resulting from working cracks in a Zn-based plated layer (3) in a workpiece (2) formed into a predetermined shape by performing plastic working on a Zn-based plated steel sheet (1) coated with a Zn-containing metal as a raw material. That is, plastic working is performed on a raw material that is a Zn-based plated steel sheet (1) to obtain a workpiece (2) having a predetermined shape, and thereafter, pressurization processing is performed on a worked portion in a sheet thickness direction to deform the plated metal, thus decreasing the width of working cracks in the plated metal. Accordingly, it is possible to reduce the deterioration in the corrosion resistance of the worked portion of the Zn-based plated workpiece.

A press forming method for producing a saddle type final product comprises a first process of producing an intermediate product having a processing adjustment section, by cold press working against an ultrahigh tensile strength steel plate, to deform the side wall portions and flange portions at the both sides in the predetermined area, with the cross section of the top plate portion being maintained in a predetermined shape, and a second process of pressing at least the processing adjustment section, by cold press working against the intermediate product, with the cross section of the top plate portion being maintained in the predetermined shape. In at least one of the first process and second process, a processing target of the at least one process is bent in the direction opposite to the opening of the hat-shaped cross section, to produce the saddle type final product