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

Patent metadata

Field	Value
Publication number	US-2016288186-A1
Application number	US-201415035287-A
Country	US
Kind code	A1
Filing date	Nov 17, 2014
Priority date	Nov 28, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

A blank steel plate is planar and used for producing a press-formed product that has an open cross-section including a bent portion. The blank steel plate is homogeneous in its entirety and includes a belt-shaped thick area that has an increased thickness, 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 the front surface 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 the back face, a step height a thickness is formed along the other of both side portions of the thick area. By using the blank steel plate in producing the press-formed product, it is possible to optimizing the strength of the press-formed product, and suppress manufacturing costs.

First claim

1 . A blank steel plate that is planar and used for producing a press-formed product having an open cross-section including a bent portion,
the blank steel plate being homogeneous across its entirety, and including a belt-shaped thick area that has 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, wherein on one of a front surface and a back face, 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, a step height in thickness is formed along another of both side portions of the thick area.

2 . The blank steel plate according to claim 1 , wherein
a hardness at a thickness center of the thick area is higher than a hardness at a thickness center of the thin area.

3 . The blank steel plate according to claim 1 , wherein
an increase in the thickness of the thick area to the thickness of the thin area is 20% or more.

4 . A production method for the blank steel plate described in claim 1 , comprising:
a preparing step of preparing, as a starting material, a steel plate having a thickness that is constant and identical to the thickness of the thin area; 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 larger than a width of the thick area, 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 the width of the thick area and increase a thickness of the first area to the thickness of the thick area.

5 . The production method for the blank steel plate according to claim 4 , wherein
in the forming process, a press device is used, the press device including a punch, a blank holder that is disposed adjacent to the punch, a die that is disposed facing the blank holder and facing a part of the punch, and a pad that is disposed adjacent to the die and facing the punch, in the first step, the starting material is pushed by the blank holder with one of the second areas of the starting material sandwiched between the punch and the pad, and the push is continued while another of the second areas of the starting material is sandwiched between the blank holder and the die, so as to form the first area that inclines with respect to the second areas, and in the second step, the one second area is pushed by the punch and the pad until the one second area becomes flush with the other second area, and the first area is compressed by the punch and the die so as to form the thick area a thickness of which is increased from a thickness of the starting material.

6 . The production method for the blank steel plate according to claim 4 , wherein
in the first step, a width L [mm] of the inclined first area, a thickness t [mm] of the starting material, an inclination angle θ [°] of the first area with respect to the second area, and a yield strength YS [MPa] of the starting material satisfy a condition represented by a following Formula (1).
( L/t )×(1/cos θ)×10 −6 ×( YS ) 2 +11.5   (1)

7 . A production device for the blank steel plate according to claim 1 , wherein
the production device for the blank steel plate uses, as a starting material, a steel plate having a thickness that is constant and identical to the thickness of the thin area, and forms the starting material into the blank steel plate by press working, the production device including a punch, a blank holder that is disposed adjacent to the punch, a die that is disposed facing the blank holder and facing a part of the punch, and a pad that is disposed adjacent to the die and facing the punch, and wherein an interval between the blank holder and the pad is identical to a width of the thick area of the blank steel plate.

8 . The production device for the blank steel plate according to claim 7 , wherein
a projecting portion is provided on a surface of the die, the surface facing the blank holder, and the projecting portion has a height identical to or smaller than a thickness of the starting material.

9 . A production method for a press-formed product that has an open cross-section including a bent portion, the production method comprising
using the blank steel plate according to claim 1 to subject the blank steel plate to press working such that the thick area of the blank steel plate forms the bent portion.

10 . The production method for a press-formed product according to claim 9 , wherein
by using a press device having: a punch that includes an impression portion in which a shape of the press-formed product is formed and a shoulder portion corresponding to the bent portion; and a pad and a die that are adjacent to each other and disposed facing the punch, press working is performed with the thick area of the blank steel plate made to coincide with a position of the shoulder portion of the punch.

11 . The production method for a press-formed product according to claim 9 , wherein the press working is performed in a cold or warm manner.

12 . The production method for a press-formed product according to claim 9 , wherein a hardness at a thickness center of the bent portion is higher than a hardness at a thickness center of a flat portion that is adjacent to the bent portion.

13 . The production method for a press-formed product according to claim 12 , wherein the hardness of the bent portion is 1.2 times or more the hardness of the flat portion in terms of Vickers hardness.

14 . The production method for a press-formed product according to claim 9 , wherein a thickness of the bent portion is 1.2 times or more a thickness of a flat portion that is adjacent to the bent portion.

15 . The production method for a press-formed product according to claim 9 , wherein a tensile strength of the blank steel plate is 440 MPa or more.

16 . The production method for a press-formed product according to claim 9 , wherein a shape of an open cross-section of the press-formed product is hat-shaped or groove-shaped.

17 . The production method for a press-formed product according to claim 9 , wherein the press-formed product is a structural member of a car body of an automobile.

18 . The production method for a press-formed product according to claim 17 , wherein the structural member is a bumper reinforcement, a door impact beam, a front side member, a rear side member, a center pillar outer reinforcement, a floor cross member, a bulkhead, or a rocker reinforcement.

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Ito Yasuhiro
• Nakazawa Yoshiaki

Classifications

• B21D53/88

  other parts for vehicles, e.g. cowlings, mudguards · CPC title

• B21D35/006 Primary

  Blanks having varying thickness, e.g. tailored blanks · CPC title

• B21D22/20

  Deep-drawing (special deep-drawing arrangements in, or in connection with, presses B21D24/00) · CPC title

• B21D11/08 Primary

  Bending by altering the thickness of part of the cross-section of the work (B21D11/06 takes precedence) · CPC title

• B21D47/00

  Making rigid structural elements or units, e.g. honeycomb structures · CPC title