A method for producing a high strength workpiece material, comprising the steps of: (a) placing a metal or alloy starting material into the central space of a cylindrical mold (2, 14), where the upper end of the starting material protrudes upward from the upper end face of the cylindrical mold (2, 14); (b) vertically compressing both end faces of the starting material with a first press member (5, 11, 15) and a support member (3, 13), thereby causing one lengthwise end of the starting material to flow radially outward along an end face of the cylindrical mold (2, 14) to form an expanded part, wherein: - in a first alternative, said first press member (5, 15) is a single press member (5, 15) large enough to press also the expanded part of the material, or - in a second alternative, a second press member for pressing the expanded part of the material is provided separately of the first press member and is separately operable; (c) advancing said single press member (5, 15), respectively integrally advancing said first press member and said second press member, while retracting said cylindrical mold (2, 14) by an amount larger than the advancement amount of said press member/s (5, 15, 11, 12), so as to increase a distance between the press member/s (5, 15, 11, 12) and the end face of the cylindrical mold (2, 14) while decreasing a distance between the press member/s (5, 15, 11, 12) and the support member (3, 13), thereby continuously causing the radially outward flow of the material to gradually increase a thickness of the expanded part; characterised in that: the single press member, respectively the first press member, has a protrusion, so that the method further comprises the step of, before increasing the thickness of the expanded part, vertically compressing only a central region of the starting material to form a recess. (a) placing a metal or alloy starting material into the central space of a cylindrical mold (2, 14), where the upper end of the starting material protrudes upward from the upper end face of the cylindrical mold (2, 14); (b) vertically compressing both end faces of the starting material with a first press member (5, 11, 15) and a support member (3, 13), thereby causing one lengthwise end of the starting material to flow radially outward along an end face of the cylindrical mold (2, 14) to form an expanded part, wherein: - in a first alternative, said first press member (5, 15) is a single press member (5, 15) large enough to press also the expanded part of the material, or - in a second alternative, a second press member for pressing the expanded part of the material is provided separately of the first press member and is separately operable; - in a first alternative, said first press member (5, 15) is a single press member (5, 15) large enough to press also the expanded part of the material, or - in a second alternative, a second press member for pressing the expanded part of the material is provided separately of the first press member and is separately operable; (c) advancing said single press member (5, 15), respectively integrally advancing said first press member and said second press member, while retracting said cylindrical mold (2, 14) by an amount larger than the advancement amount of said press member/s (5, 15, 11, 12), so as to increase a distance between the press member/s (5, 15, 11, 12) and the end face of the cylindrical mold (2, 14) while decreasing a distance between the press member/s (5, 15, 11, 12) and the support member (3, 13), thereby continuously causing the radially outward flow of the material to gradually increase a thickness of the expanded part; the single press member, respectively the first press member, has a protrusion, so that the method further comprises the step of, before increasing the thickness of the expanded part, vertically compressing only a central region of the starting material to form a recess.