Effect of Planar Anisotropy on the Hole Expansion Ratio of Cold-Rolled DP 590 Steel

Recently, due to the requirements of lightweight and safety, the grade of 980MPa high-strength steel has the demand of high hole expansibility and high yield strength. Due to the large difference of hardness between the soft ferrite and hard martensite, the traditional DP980Y dual phase steel has poor hole expansibility. In order to improve the hole expansibility of DP980Y dual phase steel, the best way is to modify the microstructure into a single-phase to eliminate the large difference of hardness. In this paper, the steel of nearly full bainite microstructure with small amount of ferrite and M/A constituents was studied. Compared to the DP980Y dual phase steel, it was found that this modified steel with a single-phase microstructure has the same grade of 980MPa of tensile strength, but can achieve the demand of higher yield strength and hole-expansion ratio. This study shows reducing the amount of ferrite can increase the homogeneity of matrix with the single phase to improve the hole expansibility. In addition, the use of lower bainite transformation temperature and lower carbon content has the higher hole-expansion ratio due to the less amount of M/A constituents.

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A numerical and experimental study on the hold-edge conditions and hole-expansion ratio of hole-blanking and hole-expansion tests for ferrite bainite steel (FB590) sheets

Ironmaking & Steelmaking ◽

10.1080/03019233.2020.1849934 ◽

2020 ◽

pp. 1-9

Author(s):

Duc-Toan Nguyen ◽

Van-Canh Tong

Keyword(s):

Experimental Study ◽

Expansion Ratio ◽

Hole Expansion ◽

Bainite Steel ◽

Edge Conditions ◽

Hole Expansion Ratio

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Improving Hole Expansion Ratio by Parameter Adjustment in Abrasive Water Jet Operations for DP800

SAE International Journal of Materials and Manufacturing ◽

10.4271/05-11-03-0023 ◽

2018 ◽

Vol 11 (3) ◽

pp. 241-252

Author(s):

Bernd-Arno Behrens ◽

David Diaz-Infante ◽

Taylan Altan ◽

Deniz Yilkiran ◽

Kai Wölki ◽

...

Keyword(s):

Expansion Ratio ◽

Water Jet ◽

Abrasive Water Jet ◽

Parameter Adjustment ◽

Hole Expansion ◽

Hole Expansion Ratio

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Effects of Piercing Punch Coating on Hole-expansion Ratio and Fatigue Properties

Journal of the Japan Society for Technology of Plasticity ◽

10.9773/sosei.56.133 ◽

2015 ◽

Vol 56 (649) ◽

pp. 133-138

Author(s):

Takashi MATSUNO ◽

Koichi SATO ◽

Akihiro UENISHI ◽

Shigeki HIGUCHI ◽

Tetsuya MASUDA ◽

...

Keyword(s):

Expansion Ratio ◽

Fatigue Properties ◽

Hole Expansion ◽

Hole Expansion Ratio

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Improvement in Punching Properties of High Tensile Strength Steel Sheet by Heat-Treatments for Reduction of Center Segregation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.622-623.1075 ◽

2014 ◽

Vol 622-623 ◽

pp. 1075-1080 ◽

Cited By ~ 3

Author(s):

Kota Sakumoto ◽

Kazuhiko Yamazaki ◽

Takashi Kobayashi ◽

Shinsuke Suzuki

Keyword(s):

Heat Treatment ◽

Tensile Strength ◽

Crack Formation ◽

Expansion Ratio ◽

High Tensile Strength ◽

Burr Height ◽

Hole Expansion ◽

Steel Sheets ◽

Heat Treated ◽

Hole Expansion Ratio

We investigated punching properties (crack in punched surface and hole expansion ratio) of high tensile strength steel sheets with and without center segregation. High strength steel sheets were heat-treated to reduce center segregation. Tensile strength, shear surface ratio, depth of rollover and burr height were measured on heat-treated steel sheets to confirm the effect of heat-treatment on strength. The EPMA analysis showed that the center segregation of Mn was reduced by the diffusion during heat-treatment. Crack-formation frequency and hole expansion ratio were also measured. As a result, the center segregation of Mn in high tensile strength steel sheets decreased by the heat-treatment (600 oC for 100 h) with maintaining the tensile strength, the depth of rollover and the burr height. The crack-formation frequency of the steel sheets decreased through heat-treatments.

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Fundamental aspect of stretch-flangeability of sheet metals

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1177/0954405418815370 ◽

2018 ◽

Vol 233 (10) ◽

pp. 2115-2119 ◽

Cited By ~ 2

Author(s):

Surajit Kumar Paul

Keyword(s):

Tensile Test ◽

Sheet Metal ◽

Expansion Ratio ◽

Uniaxial Tensile ◽

Uniaxial Tensile Test ◽

Hole Expansion ◽

Expansion Test ◽

Localized Necking ◽

Hole Expansion Test ◽

Hole Expansion Ratio

Stretch-flangeability of sheet metal is normally represented by hole expansion ratio. Hole expansion ratio cannot be determined from uniaxial tensile test though uniaxial tensile deformation occurs at the hole’s edge, because of fundamental difference in deformation and damage processes present between hole expansion test and uniaxial tensile test. It is proposed that only localized necking is observed in hole expansion test; however, diffuse necking followed by localized necking is observed in uniaxial tensile test of sheet metal. It is noticed that the hole expansion ratio is marginally higher than maximum diffuse neck strain determined from uniaxial tensile test with local strain measurement by digital image correlation technique. The absence of diffuse neck in hole expansion test with defect-free central hole (i.e. electrical discharge machined hole) results far higher hole expansion ratio than uniform elongation of the material.

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