Formed material manufacturing method and surface treated metal plate used in same
A formed material manufacturing method according to present invention includes the steps of forming a convex formed portion by performing at least one forming process on a surface treated metal plate, and performing ironing on the formed portion using an ironing mold after forming the formed portion. The ironing mold includes a punch that is inserted into the formed portion, and a die having a pushing hole into which the formed portion is pushed together with the punch. An inner peripheral surface of the pushing hole extends non-parallel to an outer peripheral surface of the punch, and the inner peripheral surface is provided with a clearance that corresponds to an uneven plate thickness distribution, in the pushing direction, of the formed portion prior to the ironing relative to the outer peripheral surface to ensure that an amount of ironing applied to the formed portion remains constant in the pushing direction.
1. A formed material manufacturing method, comprising the steps of:
forming a convex formed portion by performing at least one forming process on a surface treated metal plate; and
performing ironing on the formed portion using an ironing mold after forming the formed portion,
wherein the surface treated metal plate includes a surface treated layer provided on a surface of the metal plate, and a lubricating film provided on a surface of the surface treated layer,
wherein the ironing mold includes a punch that is inserted into the formed portion, and a die having a pushing hole into which the formed portion is pushed together with the punch,
wherein the pushing hole includes a shoulder portion disposed on an outer edge of an inlet of the pushing hole and comprising a curved surface having a predetermined curvature radius, and an inner peripheral surface which extends from a radius end of the shoulder portion in a pushing direction of the formed portion, and along which an outer surface of the formed portion slides in response to relative displacement between the punch and the die, and
wherein the inner peripheral surface extends non-parallel to an outer peripheral surface of the punch, and the inner peripheral surface is provided with a clearance that corresponds to an uneven plate thickness distribution, in the pushing direction, of the formed portion prior to the ironing relative to the outer peripheral surface to ensure that an amount of ironing applied to the formed portion remains constant in the pushing direction, and wherein a substantial length of the inner peripheral surface of the pushing hole in the pushing direction faces the outer peripheral surface of the punch when the punch reaches a completion position in the ironing step so that a substantially entire length of the formed portion defined between a base portion of the formed portion and an apex portion of the formed portion is disposed between the inner peripheral surface of the pushing hole and the outer peripheral surface of the punch.
2. The formed material manufacturing method according to claim 1 , wherein a thickness of the lubricating film is set to be thicker than 0.2 μm and thinner than 1.8 μm.
3. The formed material manufacturing method according to claim 2 , wherein the thickness of the lubricating film is set to be no less than 0.5 μm and no more than 1.2 μm.