SHEARING METHOD

• US 20180333760A1
• Filed: 02/25/2016
• Published: 11/22/2018
• Est. Priority Date: 02/25/2015
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: YASUTOMI, Takashi, MATSUNO, Takashi, YONEMURA, Shigeru, YOSHIDA, Tohru
• Granted Patent: US 10,639,698 B2
• Time in Patent Office: Days
• CPC Class Codes: B21D 28/14 Dies ejecting or stripping-off devices arranged in punching machines or tools B21D45/00
• CPC Class Codes: B21D 28/16 Shoulder or burr prevention , e.g. fine-blanking

Abstract

Provided is a steel material shearing method that enables highly productive and low-cost production of a steel material with a sheared surface having excellent hydrogen embrittlement resistance, fatigue strength, and stretch flangeability. The shearing method comprises making a clearance between a die and a punch 5 to 80% of a sheet thickness of a workpiece, shearing the workpiece using the punch, and, by utilizing a punched material punched out by the punch, pressing an end face of the punched out material against the sheared surface of the worked material on the die to produce a steel sheet with a sheared edge having excellent hydrogen embrittlement resistance and fatigue strength.

Claims

1. A shearing method in which a workpiece having a first surface and a second surface on the opposite side of the first surface is arranged on a die so that the second surface is arranged at the die side and the workpiece is sheared from the first surface toward the second surface in a sheet thickness direction of the workpiece by a punch arranged at the first surface side, wherein the shearing method comprises:

(A) a clearance setting process of making a clearance between the die and the punch in a direction perpendicular to the sheet thickness direction of the workpiece 5% to 80% of the sheet thickness of the workpiece,

(B) a shearing process of using the punch to shear the workpiece to obtain a punched out material and a worked material, wherein the punched out material and the worked material respectively have a first surface and a second surface corresponding to the first surface and the second surface of the workpiece, and

(C) a pushing process of using a pushing punch arranged at the second surface side of the worked material so as to be opposed to the punch, so as to push the punched out material in the state as punched into a punched hole of the worked material to push the end face of the punched out material against the sheared edge of the worked material.

2. The shearing method according to claim 1, wherein, in the process (A), the clearance between the die and the punch is made 10% to 80%.

3. The shearing method according to claim 1, wherein, in the process (A), the clearance between the die and the punch is made 10% to 30%.

4. The shearing method according to claim 1, wherein, in the process (C), the punched out material is pushed in by a range where the second surface of the punched out material does not pass the first surface of the worked material, so as to coin the sheared edge of the worked material.

5. The shearing method according to claim 1, wherein, in the process (C), the punched out material is pushed in by a range where a position of the second surface of the punched out material does not pass a position of half of the sheet thickness from the second surface to the first surface of the worked material, so as to coin the sheared edge of the worked material.

6. The shearing method according to claim 1, wherein, in the process (C), the punched out material is pushed in so that a position of the second surface of the punched out material becomes the same as the position of the second surface of the worked material, so as to coin the sheared edge of the worked material.

7. The shearing method according to claim 1, wherein, in the process (C), the punched out material is pushed in by a range where a position of the second surface of the punched out material does not pass the position of the second surface of the worked material, so as to coin at least part of the sheared edge of the worked material.

8. The shearing method according to claim 1, wherein, in the process (C), the punched out material pushed into the punched hole is punched out by the punch and the punched out material is pushed into the punched hole by the pushing punch repeatedly 1 time or more.

9. The shearing method according to claim 1, wherein

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

at least one surface between a punching surface of the punch and a pushing surface of the pushing punch has a projecting part, and

the shearing and the pushing are conducted while the punch and the pushing punch are gripping and fastening the workpiece between them.

10. The shearing method according to claim 1, wherein

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

an additional punch is arranged linked with the punch at a further outer circumferential side from the punch,

an additional pushing punch is arranged linked with the pushing punch at a further outer circumferential side from the pushing punch so as to be opposed to the additional punch across the workpiece,

at least one surface between a punching surface of the additional punch and a pushing surface of the additional pushing punch has a projecting part, and

the shearing and the pushing are conducted while the punching surfaces of the linked punch and additional punch and the pushing surfaces of the linked pushing punch and additional pushing punch are gripping and fastening the workpiece between them.

11. The shearing method according to claim 1, wherein:

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

an additional holder is arranged at a further outer circumferential side from the punch,

an additional die is arranged at a further outer circumferential side from the pushing punch so as to be opposed to the additional holder across the workpiece,

at least one surface between a fastening surface of the additional holder facing the first surface of the workpiece and a fastening surface of the additional die facing the second surface of the workpiece has a projecting part, and

the shearing and the pushing are conducted while the fastening surface of the additional holder and the fastening surface of the additional die are gripping and fastening the workpiece between them.

12. The shearing method according to claim 1, wherein

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

an additional punch is arranged at a further outer circumferential side from the punch,

the additional punch and the pushing punch are used to shear the workpiece to obtain a burnished surface, and

the clearance is set, the shearing is conducted and the pushing is conducted while the burnished surface is being constrained by a side surface of the additional punch.

13. The shearing method according to claim 1, wherein

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

an additional die is arranged at a further outer circumferential side from the pushing punch,

the punch and the additional die are used to shear the workpiece to obtain a burnished surface, and

the clearance is set, the shearing is conducted and the pushing is conducted while the burnished surface is being constrained by a side surface of the additional die.

14. The shearing method according to claim 1, wherein

the die, the punch, and the pushing punch have an outer trimming configuration wherein the die is arranged at an inner circumferential side of the workpiece, and the punch and the pushing punch are arranged at an outer circumferential side of the workpiece,

an additional holder is arranged at a further outer circumferential side from the punch,

an additional die is arranged at a further outer circumferential side from the pushing punch so as to be opposed to the additional holder across the workpiece,

the punch and the additional die are used to shear the workpiece to obtain a burnished surface, and

the clearance is set, the shearing is conducted and the pushing is conducted while the burnished surface is being constrained by a side surface of the additional die or additional holder.

15. The shearing method according to claim 1, wherein the workpiece is a metal sheet having a 340 MPa class or more tensile strength.

16. The shearing method according to claim 1, wherein the workpiece is a metal sheet having a 980 MPa class or more tensile strength.

17. The shearing method according to claim 15, wherein the workpiece is a steel material.

18. The shearing method according to claim 2, wherein, in the process (C), the punched out material is pushed in by a range where the second surface of the punched out material does not pass the first surface of the worked material, so as to coin the sheared edge of the worked material.

19. The shearing method according to claim 3, wherein, in the process (C), the punched out material is pushed in by a range where the second surface of the punched out material does not pass the first surface of the worked material, so as to coin the sheared edge of the worked material.

20. The shearing method according to claim 2, wherein, in the process (C), the punched out material is pushed in by a range where a position of the second surface of the punched out material does not pass a position of half of the sheet thickness from the second surface to the first surface of the worked material, so as to coin the sheared edge of the worked material.