scholarly journals Review of Shearing Processes of High Strength Steel Sheets

2020 ◽  
Vol 4 (2) ◽  
pp. 54 ◽  
Author(s):  
Ken-ichiro Mori
Keyword(s):  
Fatigue Strength ◽  
High Strength Steel ◽  
High Strength ◽  
Steel Sheets ◽  
Sheared Edge ◽  
Ultra High Strength Steel ◽  
Edge Quality ◽  
Automobile Parts

Shearing processes of high strength steel sheets increasingly applied to lightweight automobile parts were reviewed. With the increase in strength of the high strength steel sheets, shearing operations become hard. First, the sheared edge quality in shearing of high strength steel sheets and the effects on the formability and fatigue strength were shown. Next, ironing processes with a taper punch and a punched slug, a slight clearance punching with a punch having a small round corner and a thickening process of the sheared edge were explained as processes for improving the sheared edge quality. Finally, hydrogen-induced delayed fractures of cold-sheared ultra-high strength steel sheets and of hot-trimmed parts were evaluated.

Direct Punching in Inclined Ultra-High Strength Steel Sheets

2014 ◽  
Vol 622-623 ◽  
pp. 1051-1057 ◽  
Author(s):  
Yohei Abe ◽  
Ken Ichiro Mori ◽  
Shigehiro Nakanoshita ◽  
Purwo Kadarno
Keyword(s):  
High Strength Steel ◽  
Steel Sheet ◽  
High Strength ◽  
Bottom Edge ◽  
Steel Sheets ◽  
Sheared Edge ◽  
Ultra High Strength Steel ◽  
Grade Steel ◽  
Inclined Sheet

A direct punching of inclined ultra-high strength steel sheets having low ductility was carried out to improve the quality of the sheared edge. In the direct punching of an inclined sheet, the contact between the sheet and punch became gradual because of touch from the bottom edge of the punch, and thus the sheared portion tended to bend in the latter half of punching. As the strength of the sheet increased, defects such as burr and secondary burnished surface were occurred around the sheared edge due to the low ductility. The range of direct punching for sheared edge without defects was shown for the high strength steel sheets. To prevent the occurrence of defects, a punch having inclined bottom was used. In this punch, the contact with the sheet was changed, the uniform contact with the inclined bottom was given. In the punch having the inclined bottom, the secondary burnished surface in the edge of 980 MPa grade steel sheet was prevented.

scholarly journals Hemming with Pre-Bent Inner Sheet for Joining Ultra-High Strength Steel Sheets of Automobile Parts

2020 ◽  
Vol 4 (3) ◽  
pp. 77
Author(s):  
Yohei Abe ◽  
Wataru Ijichi ◽  
Ken-ichiro Mori ◽  
Kazuma Nakagawa
Keyword(s):  
High Strength Steel ◽  
Joint Strength ◽  
Welded Joint ◽  
High Strength ◽  
Peel Strength ◽  
Joint Work ◽  
Steel Sheets ◽  
Ultra High Strength Steel ◽  
Automobile Parts ◽  
Joining Process

In order to join two ultra-high strength steel sheets with low ductility for automobile parts, a joining process by hemming with a pre-bent inner sheet was developed. In this joining, the pre-bent inner sheet instead of the conventional flat inner sheet was used to relax the deformation concentration of the outer sheet. Although 780 MPa steel sheets were joined without the pre-bent inner sheet, a fracture in the outer sheet occurred in joining the 980 MPa sheets due to the low ductility of the sheets. The 980 MPa and 1180 MPa sheets were successfully joined by hemming with the pre-bent inner sheet. In this process, the deformation of the upper sheet was relaxed by contacting with the inner sheet, and then the strain on the outer surface reduced. Although softening around a weld nugget occurred by heating in the conventional welded joint, work-hardening occurred in the hemmed joint. The joint strength was investigated and then the peel strength of the hemmed sheets was about a half of the welded one. It was found that the hemming process with the pre-bent inner sheet was effective for joining ultra-high strength steel sheets with low ductility.

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