Method of manufacturing metallic member, press tool, and metallic member

Abstract

A method of manufacturing a metallic member having a cut edge surface with improved corrosion resistance is provided. The method of manufacturing a metallic member uses a press tool to stamp a metal sheet having front and back faces covered with a coating layer, thus producing a metallic member. The press tool includes a punch, a counter-pad, a sheet holder, and a die. The sheet holder includes a projecting portion at an inner circumferential edge of the face facing the metal sheet, the projecting portion of the sheet holder including a corner at its inner circumference, the corner having a radius of curvature R 1, the radius of curvature R 1 being not smaller than 0.10 times the thickness of the metal sheet. The manufacturing method includes: pushing the projecting portion into the metal sheet; and moving the punch and the die closer to each other to stamp the metal sheet.

1 . A method of manufacturing a metallic member by using a press tool to stamp a metal sheet having front and back faces covered with a coating layer,
 the press tool including:   a punch;   a counter-pad located opposite to the punch, the metal sheet being positioned between the punch and the counter-pad;   a sheet holder located adjacent to the same side of the metal sheet as the punch as determined along a thickness direction of the sheet and positioned to surround the punch along in-plane directions of the metal sheet; and   a die located adjacent to the same side of the metal sheet as the counter-pad as determined along the thickness direction of the sheet and positioned to surround the counter-pad along in-plane directions of the metal sheet,   the press tool further including the following construction A) or B):   A) the sheet holder including a projecting portion at an inner circumferential edge of a face facing the metal sheet,   the projecting portion of the sheet holder including a corner at an inner circumference, the corner having a radius of curvature R 1 ,   the radius of curvature R 1  being not smaller than 0.10 times a thickness of the metal sheet, or   B) the punch including a projecting portion at a circumferential edge of a face facing the metal sheet,   the projecting portion of the punch including a corner at an outer circumference, the corner having a radius of curvature R 3 ,   the radius of curvature R 3  being not smaller than 0.10 times a thickness of the metal sheet,   the manufacturing method comprising:   pushing the projecting portion of the sheet holder or punch into the metal sheet; and   moving the punch and the die closer to each other to stamp the metal sheet.   
     
     
         2 . The method of manufacturing a metallic member according to  claim 1 , wherein:
 the press tool includes the construction A),   the die includes a projecting portion at an inner circumferential edge of a face facing the metal sheet;   the projecting portion of the die includes a corner at an inner circumference, the corner having a radius of curvature R 2 ; and   the radius of curvature R 2  is not smaller than 0.10 times the thickness of the metal sheet,   the manufacturing method further comprising:   during the pushing of the projecting portion of the sheet holder into the metal sheet, pushing the projecting portion of the die into the metal sheet.   
     
     
         3 . The method of manufacturing a metallic member according to  claim 1 , wherein:
 the press tool includes the construction A),   the die includes a double corner at an inner circumference;   the double corner includes:   a first sub-corner; and   a second sub-corner located farther from the metal sheet than the first sub-corner is as measured in the thickness direction of the metal sheet, and located closer to the counter-pad than the first sub-corner is as measured in in-plane directions of the metal sheet; and   the second sub-corner has a radius of curvature Rp 2  not smaller than 0.10 times the thickness of the metal sheet.   
     
     
         4 . (canceled) 
     
     
         5 . The method of manufacturing a metallic member according to claim  41 , wherein:
 the press tool includes the construction B),   the counter-pad includes a projecting portion at a circumferential edge of a face facing the metal sheet;   the projecting portion of the counter-pad includes a corner at an outer circumference, the corner having a radius of curvature R 4 ;   the radius of curvature R 4  is not smaller than 0.10 times the thickness of the metal sheet,   the manufacturing method further comprising:   during the pushing of the projecting portion of the punch into the metal sheet, pushing the projecting portion of the counter-pad into the metal sheet.   
     
     
         6 . The method of manufacturing a metallic member according to claim  41 , wherein:
 the press tool includes the construction B),   the counter-pad includes a double corner at a circumferential edge of a face facing the metal sheet;   the double corner includes:   a first sub-corner;   a second sub-corner located farther from the metal sheet than the first sub-corner is as measured in the thickness direction of the metal sheet, and located closer to die than the first sub-corner is as measured in in-plane directions of the metal sheet; and   the second sub-corner has a the radius of curvature Rp 4  not smaller than 0.10 times the thickness of the metal sheet.   
     
     
         7 . A press tool comprising:
 a punch;   a counter-pad located opposite to the punch, a metal sheet representing a workpiece being positioned between the punch and the counter-pad;   a sheet holder located adjacent to the same side of the metal sheet as the punch as determined along a thickness direction of the sheet and positioned to surround the punch along in-plane directions of the metal sheet; and   a die located adjacent to the same side of the metal sheet as the counter-pad as determined along the thickness direction of the sheet and positioned to surround the counter-pad along in-plane directions of the metal sheet,   the press tool further including the following construction A) or B):   A) the sheet holder including a projecting portion at an inner circumferential edge of a face facing the metal sheet,   the projecting portion of the sheet holder including a corner at an inner circumference, the corner having a radius of curvature R 1 ,   the radius of curvature R 1  being not smaller than 0.2 mm, or   B) the punch including a projecting portion at a circumferential edge of a face facing the metal sheet,   the projecting portion of the punch including a corner at an outer circumference, the corner having a radius of curvature R 3 ,   the radius of curvature R 3  being not smaller than 0.2 mm.   
     
     
         8 . The press tool according to  claim 7 , wherein:
 the press tool includes the construction A),   the die includes a projecting portion at an inner circumferential edge of a face facing the metal sheet;   the projecting portion of the die includes a corner at an inner circumference, the corner having a radius of curvature R 2 ; and   the radius of curvature R 2  is not smaller than 0.2 mm.   
     
     
         9 . The press tool according to  claim 7 , wherein:
 the press tool includes the construction A),   the die includes a double corner at an inner circumference;   the double corner includes:   a first sub-corner;   a second sub-corner located farther from the metal sheet than the first sub-corner is as measured in the thickness direction of the metal sheet, and located closer to the counter-pad than the first sub-corner is as measured in in-plane directions of the metal sheet; and   the second sub-corner has a radius of curvature Rp 2  not smaller than 0.1 mm.   
     
     
         10 . (canceled) 
     
     
         11 . The press tool according to claim  10 , wherein:
 the press tool includes the construction B),   the counter-pad includes a projecting portion at a circumferential edge of a face facing the metal sheet;   the projecting portion of the counter-pad includes a corner at an outer circumference, the corner having a radius of curvature R 4 ; and   the radius of curvature R 4  is not smaller than 0.2 mm.   
     
     
         12 . The press tool according to  claim 7 , wherein:
 the press tool includes the construction B),   the counter-pad includes a double corner at a circumferential edge of a face facing the metal sheet;   the double corner includes:   a first sub-corner;   a second sub-corner located farther from the metal sheet than the first sub-corner is as measured in the thickness direction of the metal sheet, and located closer to the die than the first sub-corner is as measured in in-plane directions of the metal sheet; and   the second sub-corner has a radius of curvature Rp 4  not smaller than 0.1 mm.   
     
     
         13 . A metallic member formed by stamping a metal sheet having front and back faces covered with a coating layer, including a cut edge surface formed by the stamping,
 the cut edge surface including:   a sheared surface; and   a recessed surface represented by a curved surface having a shape protruding inwardly with respect to the member,   at least a portion of the recessed surface being covered with the coating layer.   
     
     
         14 . The metallic member according to  claim 13 , wherein:
 the cut edge surface further includes an undercut contiguous to the recessed surface; and   not less than 50% of a total area of the recessed surface and the undercut is covered with the coating layer.   
     
     
         15 . The metallic member according to  claim 13 , wherein:
 the cut edge surface further includes a second undercut contiguous to the sheared surface; and   the sheared surface is located between the recessed surface and the second undercut as determined along a thickness direction of the metallic member.   
     
     
         16 . The metallic member according to  claim 13 , wherein:
 the cut edge surface further includes a second recessed surface represented by a curved surface having a shape protruding inwardly with respect to the member, and a second undercut contiguous to the second recessed surface; and   the sheared surface is located between the recessed surface and the second recessed surface as determined along a thickness direction of the metallic member.   
     
     
         17 . The metallic member according to  claim 13 , wherein an amount of sinking represented by a distance between a tangent to the sheared surface and an inwardmost point on the recessed surface is 0.01 to 0.10 times a thickness of the metallic member.