Blank steel plate, production method and production device therefor, and production method for press-formed product using blank steel plate

A method for producing a planar blank steel plate comprising:

• a preparing step of preparing, as a starting material, a steel plate having a thickness that is constant;
• and
• a forming process of forming the starting material into the blank steel plate by press working, wherein
• the forming process includes:
• a first step of segmenting the starting material into a belt-shaped first area that has a width, and second areas that are adjacent to both side portions of the first area, and displacing the second areas to different planes parallel to each other while causing the first area to incline with respect to the second areas;
• and
• a second step of displacing the second areas to be flush with each other while restraining the second areas in terms of movement in a width direction so as to compress the width of the first area into a width of a thick area and increase a thickness of the first area to a thickness of the thick area to make the blank steel plate, wherein
• the blank steel plate is homogeneous across its entirety,
• the blank steel plate includes a belt-shaped thick area with an increased thickness, and thin areas that are adjacent to both sides of the thick area and have a thickness smaller than the thickness of the thick area,
• on one of a front surface and a back face of the blank steel plate, a step height in thickness is formed along one of both side portions of the thick area, and
• on another of the front surface and the back face of the blank steel plate, a step height in thickness is formed along another of both side portions of the thick area.