Forming Performance of 800MPa Grade Advanced High Strength Steels

2013 ◽  
Vol 455 ◽  
pp. 173-178 ◽  
Author(s):  
Mei Zhang ◽  
Yu Xiang Ning ◽  
Jun Zhang ◽  
Zi Wan ◽  
Tao Wang
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Expansion Ratio ◽  
Hole Expansion ◽  
Advanced High Strength Steels ◽  
Hsla Steels ◽  
Blank Holding Force ◽  
Hole Expansion Ratio ◽  
Test Hole ◽  
Springback Behavior

800MPa grade Advanced High Strength Steels (AHSS), including Complex Phase steel CP800 and Ferrite-Bainite steel FB800, were chosen to test the forming performance in different test conditions and compared with the reference traditional high strength low alloy (HSLA) steels HR700LA. Tensile test, hole expansion (HE) test, and HAT shape stamping test were taken to investigate the forming performance of the materials. Test results indicated that the studied 800MPa grade AHSS showed a better strength ductility balance compared with the reference steel. Among all the steels researched, FB800 showed the best hole expansion ratio (HER), and CP800 the worst. Springback angles of AHSS after HAT shape stamping tests were markedly smaller than those of HR700LA steels, though the springback angles of HR700LA decreased continuously with blank holding force (BHF) increasing. Steel FB800, CP800S and CP800B had much better shape stability compared with steels HR700LA. AHSS showed much smaller springback behavior under the same stamping condition, especially for steels CP800-B, FB800-2 and FB800-1. When increasing the BHF to 100KN, AHSS showed the largest springback deformation. Among the three kinds of CP800 steels researched, steel CP800-B indicated outstanding springback restrain trend in BHF further increasing attempt. So, springback behavior could be restricted obviously by using a larger BHF in AHSS CP800B forming operations.

Springback Behavior of Advanced High Strength Steel (AHSS) CP800

2013 ◽  
Vol 820 ◽  
pp. 45-49 ◽  
Author(s):  
Mei Zhang ◽  
Jun Zhang ◽  
Yu Xiang Ning ◽  
Tao Wang ◽  
Zi Wan
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Test Results ◽  
Complex Phase ◽  
Advanced High Strength Steels ◽  
Test Conditions ◽  
Hsla Steels ◽  
Blank Holding Force ◽  
Microalloying Elements ◽  
Springback Behavior

800MPa grade Advanced High Strength Steels (AHSS), Complex Phase steel CP800, containing microalloying elements, are chosen to test the stamping properties in different test conditions and compared with traditional high strength low alloy (HSLA) steels HSLA S700MC. Tensile test, and HAT shape stamping test are taken to investigate the properties of the materials. Test results indicate that the studied 800MPa grade AHSS shows a better strength ductility balance compared with the reference HSLA steels. Under the same HAT shape springback stamping condition, HSLA steels S700MC always show the largest springback deformation among the investigated steels. While springback angles of all the AHSS studied are markedly smaller than that of steel S700MC. Among the 3 kinds of AHSS researched, CP800T always show the largest springback deformation. Domestic steel CP800 and imported CP800S show much smaller springback deformation respectively. In BHF of 100KN condition, springback deformation of 3 kinds of AHSS reaches the top value among all the BHF conditions. However, steel CP800 indicates an outstanding springback restrain trend in blank holding force (BHF) further increasing attempt. Thus, springback behavior can be restricted obviously by using a larger blank holding force (BHF) in steel CP800 stamping cases.

The Study in Improvement of Hole Expansibility for High-Strength Steel of 980MPa Grade

2018 ◽  
Vol 941 ◽  
pp. 492-497
Author(s):  
Kuo Cheng Yang ◽  
J.F. Tu ◽  
L.J. Chiang ◽  
W.J. Cheng ◽  
C.Y. Huang
Keyword(s):  
Yield Strength ◽  
High Strength Steel ◽  
Dual Phase Steel ◽  
Single Phase ◽  
High Strength ◽  
Expansion Ratio ◽  
High Yield ◽  
Dual Phase ◽  
Hole Expansion ◽  
Hole Expansion Ratio

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.

scholarly journals Influence of Ti and Nb on the Strength–Ductility–Hole Expansion Ratio Balance of Hot-rolled Low-carbon High-strength Steel Sheets

2012 ◽  
Vol 52 (1) ◽  
pp. 151-157 ◽  
Author(s):  
Kyohei Kamibayashi ◽  
Yutaka Tanabe ◽  
Yoshito Takemoto ◽  
Ichirou Shimizu ◽  
Takehide Senuma
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Expansion Ratio ◽  
Low Carbon ◽  
Hole Expansion ◽  
Steel Sheets ◽  
Hole Expansion Ratio ◽  
Hot Rolled

Influence of Microstructure on Damage in Advanced High Strength Steels

2012 ◽  
Vol 706-709 ◽  
pp. 925-930 ◽  
Author(s):  
Frank Hisker ◽  
Richard Thiessen ◽  
Thomas Heller
Keyword(s):  
Work Hardening ◽  
Tensile Testing ◽  
Failure Modes ◽  
Tensile Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
Body Parts ◽  
Hole Expansion ◽  
Advanced High Strength Steels ◽  
Dp Steels

AHSS (Advanced High Strength Steels) combine high strength and good ductility. Their outstanding forming and work-hardening behavior predestines these steels for fabrication of strength relevant structural elements and automobile body parts. To characterize a material, not only tensile, but also hole-expansion and bending behavior are important and help predict the stretch-flange-formability. In this study, detailed analyses of the correlation between these three tests and the damage mechanisms during forming have been performed for selected steels. The results show that for AHSS one should differentiate between “local” and “global” failure. Furthermore, not only are certain materials more sensitive to local or global damage, but also various testing methods tend to provoke either local or global damage. Tensile testing provokes global failure whereas hole-expansion tends to induce local failure. A specimen fails during bending with a mixture of local and global modes. These failure modes are strongly attributed to the microstructure. DP-steels yield high elongation during tensile testing and poorer hole-expansion values. High-resolution EBSD has revealed that the microstructure of DP-steels is sensitive to localized damage, which is compensated by work-hardening around damaged regions and thus shifts the loading to un-hardened regions. This makes DP-microstructures well-suited to tensile loading but sensitive to hole-expansion. CP-steels of comparable strength show poorer tensile elongation and higher hole-expansion ratios due to a microstructure which is not sensitive to localized failure (but has limited capacity for work-hardening). The failure mode in TRIP-steels exhibits a similar character as in DP-steels, but only after the martensitic transformation of retained austenite.

scholarly journals Hole Expansion Ratio and Fatigue Properties in Piercing of High-Strength Steel Sheets by PW Punch

2011 ◽  
Vol 52 (606) ◽  
pp. 795-800 ◽  
Author(s):  
Takashi MATSUNO ◽  
Yukihisa KURIYAMA ◽  
Hiroya MURAKAMI ◽  
Shota YONEZAWA ◽  
Naonobu KANAMARU
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Expansion Ratio ◽  
Fatigue Properties ◽  
Hole Expansion ◽  
Steel Sheets ◽  
Hole Expansion Ratio

New Trends in Advanced High Strength Steel Developments for Automotive Application

2010 ◽  
Vol 638-642 ◽  
pp. 136-141 ◽  
Author(s):  
Ohjoon Kwon ◽  
Kyoo Young Lee ◽  
Gyo Sung Kim ◽  
Kwang Geun Chin
Keyword(s):  
Mechanical Performance ◽  
High Strength Steels ◽  
High Strength ◽  
Expansion Ratio ◽  
The Body ◽  
Automotive Application ◽  
Car Industry ◽  
Advanced High Strength Steels ◽  
Conventional Solution ◽  
Strength And Ductility

The body design with light weight and enhanced safety is a key issue in the car industry. Corresponding to this trend, POSCO is developing various automotive steel products with advanced performance. Conventional advanced high strength steels such as DP and TRIP steels are now expanding their application since the steels exhibit higher strength and ductility than those of conventional solution and precipitation strengthened high strength steels. Efforts have been made to enhance the mechanical performance of these steels such as ductility, hole expansion ratio, deep drawability, etc. Current research is focused on development of extra- and ultra-AHSS. Extra-AHSS are designed to utilize nano-scale retained austenite embedded in fine bainite and martensite. Ultra-AHSS are designed to have austenite as the major phase, and the ductility is enhanced primarily by continuous strain hardening generated during forming. These steels including extra- and ultra-AHSS are believed to be the next generation automotive steels which will replace the existing high strength steels due to their extremely high strength and ductility combinations.

Fracture characteristics of advanced high strength steels during hole expansion test

2020 ◽  
Vol 224 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Vivek Kumar Barnwal ◽  
Shin-Yeong Lee ◽  
Seong-Yong Yoon ◽  
Jin-Hwan Kim ◽  
Frédéric Barlat
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Fracture Characteristics ◽  
Hole Expansion ◽  
Expansion Test ◽  
Advanced High Strength Steels ◽  
Hole Expansion Test

Increasing the Hole Expansion Ability of High Strength Steel Sheet by Improving the Pre-Hole Shearing Process

2019 ◽  
Vol 962 ◽  
pp. 167-174
Author(s):  
Prasan Saengkhiao ◽  
Komgrit Lawanwong ◽  
Pakorn Chumrum
Keyword(s):  
High Strength Steel ◽  
Steel Sheet ◽  
High Strength ◽  
Expansion Ratio ◽  
Expansion Process ◽  
Forming Process ◽  
Research Papers ◽  
Hole Expansion ◽  
Hole Edge ◽  
Hole Expansion Ratio

The hole expansion process is a forming process that the fracture easily occurred on the hole edge. Therefore, many research papers presented various processes to make a precision pre-hole shearing to a hole expansion process such as wire cut, EDM, and laser cut. The purpose of this work is to increase a hole expansion ratio on the high strength steel sheet. The conventional piercing by piercing punch and piercing with a counter punch was used to make a pre-hole shearing process in this research paper. The high strength steel grade 590 and 980 MPa of 1.2 mm of thickness were used in the experiments. From experimental results, it was found that the pre-hole shearing by piercing with a counter punch can be increased a shear surface on cutting edge of workpiece. Moreover, the used piercing with counter punch can improve the hole expansion ratio more than the conventional piercing process because sheared surface around the hole edge was increased.

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