On part of a surface of a metal sheet that is to be heated by radiant heat transfer with a near-infrared ray, a region where reflectance for a radiant ray is made lower than that of the original surface of the metal sheet is formed. As reflectance reducing treatment, painting or thermal spraying in a blackish color, plating in a blackish color, treatment for increasing roughness of the surface of the metal sheet, blasting, etching, blackening, surface layer quality changing treatment of the metal sheet, or the like can be adopted. The metal sheet is turned into a heated metal sheet partially having a different temperature by being heated by radiant heat transfer, and thereafter, the heated metal sheet is subjected to thermal processing accompanied by cooling, for example, by hot stamping.

The invention relates to a method for producing partially-hardened components from steel sheets, in which a component that is cold-formed from a hardenable steel sheet material is heated, in a furnace, to a temperature below the austenitization temperature (<AC.sub.3), and a radiating element acts upon the component in sections where said component is to be austenitized (<AC.sub.3), this radiating element having a component-side contour that corresponds to the contour of the component in the section to be austenitized. The invention also relates to a device for carrying out said method.

A high strength member according to the present invention is the high strength member having a bending ridge line portion formed from a steel sheet, the member having a tensile strength of 1470 MPa or higher, a residual stress of 300 MPa or lower in an end surface of the bending ridge line portion, and a Vickers hardness (HV) of 200 or higher and 450 or lower in the end surface of the bending ridge line portion.