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.

Relationship between Microstructure and Mechanical Properties in Q&P-Steels

2016 ◽  
Vol 879 ◽  
pp. 1933-1938 ◽  
Author(s):  
Richard G. Thiessen ◽  
Georg Paul ◽  
Roland Sebald
Keyword(s):  
Mechanical Properties ◽  
Dual Phase Steel ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Back Scattering ◽  
Body In White ◽  
Expected Increase

Third-Generation advanced high strength steels are being developed with the goal of reducing the body-in-white weight while simultaneously increasing passenger safety. This requires not only the expected increase in strength and elongation, but also improved local formability. Optimizing elongation and formability were often contradictory goals in dual-phase steel developments. Recent results have shown that so-called "quench and partitioning" (Q&P) concepts can satisfy both requirements [1]. Many Q&P-concepts have been studied at thyssenkrupp Steel Europe. Thorough investigation of the microstructure has revealed relationships between features such as the amount, morphology and chemical stability of the retained austenite and the obtained mechanical properties. An evaluation of the lattice strain by means of electron-back-scattering-diffraction has also yielded a correlation to the obtained formability. The aim of this work is to present the interconnection between these microstructural features and propose hypotheses for the explanation of how these features influence the macroscopically observed properties.

Prediction of Post Weld Hardness of Advanced High Strength Steels for Automotive Application using a Dedicated Carbon Equivalent Number

2008 ◽  
Vol 52 (11-12) ◽  
pp. 18-29 ◽  
Author(s):  
N. J. den Uijl ◽  
H. Nishibata ◽  
S. Smith ◽  
T. Okada ◽  
T. van der Veldt ◽  
...  
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Automotive Application ◽  
Carbon Equivalent ◽  
Advanced High Strength Steels ◽  
Equivalent Number

scholarly journals A New Approach to Implement High Strength 7075 Aluminum for Automotive Application

2020 ◽  
Vol 326 ◽  
pp. 03004
Author(s):  
Cedric Wu ◽  
Yudie Yuan ◽  
Rajeev Kamat
Keyword(s):  
Aging Time ◽  
Artificial Aging ◽  
High Strength Steels ◽  
High Strength ◽  
Automotive Application ◽  
New Approach ◽  
Specific Strength ◽  
Advanced High Strength Steels ◽  
Depth Analysis ◽  
Structural Applications

Aluminum alloys offer high specific strength than advanced high strength steels, making them preferred candidates for automotive light weighting. Among them, AA7075 aluminum alloy offers significantly higher strength than 5xxx and 6xxx alloys and is considered an attractive candidate by automotive OEMs for structural applications such as door intrusion beams, B pillars etc. There are several challenges in implementing AA7075, such as long artificial aging time to reach peak strength, joining method and corrosion resistance. In this study, an artificial aging practice that significantly reduces aging time was explored and its influence on mechanical properties of AA7075 was investigated in comparison with conventional peak age practice. In addition, this practice offers a potential solution for joining through self-piercing riveting. Moreover, the effect of artificial aging on corrosion, specifically intergranular corrosion (IGC) and stress corrosion cracking (SCC) was evaluated. The results are discussed with in depth analysis and correlation with microstructure.

Design of Modern Steels for Automotive Application

2010 ◽  
Vol 638-642 ◽  
pp. 3111-3116 ◽  
Author(s):  
Harald Hofmann ◽  
Thomas Heller ◽  
Sascha Sikora
Keyword(s):  
High Strength Steels ◽  
Superplastic Forming ◽  
High Strength ◽  
Hot Forming ◽  
Automotive Application ◽  
Advanced High Strength Steels ◽  
Automobile Components ◽  
Multi Phase ◽  
Further Development ◽  
Complex Parts

Advanced high-strength steels offer a great potential for the further development of automobile bodies-in-white due to their combined mechanical properties of high formability and strength. New types of grades – multi-phase steels, superductile steels and density reduced steels – are under development at ThyssenKrupp Steel with tensile strength levels of up to 1000 MPa in combination with excellent formability for the high demands of cold formed structural automobile components. New forming technologies at increased temperatures – hot forming, semi-hot forming and superplastic forming - enable the processing of complex parts with extreme high strength. ThyssenKrupp Steel identifies potential future steels and technology concepts by technology monitoring and evaluates their potential for future applications in pre-development projects. University research institutions are significantly involved in this essential future oriented challenge. Seminal concepts are being implemented together with automotive manufactures by simultaneous engineering processes with coordinated phases of production and testing.

Latest Developments in Sheet Metal Forming Technologies and Materials for Automotive Application: the Use of Ultra High Strength Steels at Fiat to Reach Weight Reduction at Sustainable Costs

2007 ◽  
Vol 344 ◽  
pp. 1-8 ◽  
Author(s):  
Manuel Lai ◽  
R Brun
Keyword(s):  
Weight Reduction ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Automotive Application ◽  
Recent Experience ◽  
New Methodologies ◽  
Ultra High Strength Steels ◽  
Set Up ◽  
The Body Shop

In new vehicles development weight reduction is one of the most important driving force often conflicting with other missions which would require additional mass (crashworthiness, comfort, etc). The use of HSS, especially new grades with very high strength and good formability is the most competitive way to reduce weight. Nevertheless some limitations come from manufacturing HSS: springback, residual stresses, weldability should be taken into account in product development in order to avoid an expensive set up phase in the press shop and in the body shop. This paper focus on the recent experience achieved by Fiat in introducing HSS up to reach a share higher than 60% in weight applying and developing new methodologies to solve in the design phase any criticality arising from the use of this material.

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 Investigation in Roll Forming of a V-Section

2014 ◽  
Vol 553 ◽  
pp. 643-648 ◽  
Author(s):  
Akbar Abvabi ◽  
Joseba Mendiguren ◽  
Bernard F. Rolfe ◽  
Matthias Weiss
Keyword(s):  
Elastic Modulus ◽  
Continuous Process ◽  
High Strength Steels ◽  
Shell Element ◽  
High Strength ◽  
Material Model ◽  
The Body ◽  
Roll Forming ◽  
Forming Process ◽  
Advanced High Strength Steels

To have fuel efficient vehicles with a lightweight structure, the use of High Strength Steels (HSS) and Advanced High Strength Steels (AHSS) in the body of automobiles is increasing. Roll forming is used widely to form AHSS materials. Roll forming is a continuous process in which a flat strip is shaped to the desired profile by passing through numerous sets of rolls. Formability and springback are two major concerns in the roll forming of AHSS materials. Previous studies have shown that the elastic modulus (Young’s modulus) of AHSS materials can change when the material undergoes plastic deformation and the main goal of this study is to numerically investigate the effect of a change in elastic modulus during forming on springback in roll forming. Experimental loading-unloading tests have been performed to obtain the material properties of TRIP 700 steel and incorporate those in the material model used in the numerical simulation of the roll forming process. The finite element simulations were carried out using MSC-Marc and two different element types, a shell element and a solid-shell element, were investigated. The results show that the elastic modulus diminution due to plastic strain increases the springback angle by about 60% in the simple V-section roll forming analyzed in this study.

scholarly journals Microstructural characterization of a double pulse resistance spot welded 1200 MPa TBF steel

2019 ◽  
Vol 64 (2) ◽  
pp. 335-343
Author(s):  
Manfred Stadler ◽  
Martin Gruber ◽  
Ronald Schnitzer ◽  
Christina Hofer
Keyword(s):  
Mechanical Performance ◽  
Bainitic Ferrite ◽  
High Strength Steels ◽  
Quality Criterion ◽  
High Strength ◽  
Microstructural Characterization ◽  
Double Pulse ◽  
Resistance Spot ◽  
Advanced High Strength Steels ◽  
Pulse Welding

AbstractIn the automotive industry resistance, spot welding is the dominant technology in sheet metal joining of advanced high strength steels (AHSS). In order to improve the mechanical performance of AHSS welds, in-process tempering via a second pulse is a possible approach. In this work, two different double pulse welding schemes were applied to a 1200 MPa transformation-induced plasticity (TRIP)-aided bainitic ferrite (TBF) steel. The different microstructures in the welds were characterized via light optical and scanning electron microscopy. Additionally, hardness mappings with several hundred indents were performed. It is shown that the second pulse, following a low first pulse which is high enough to produce a weld nugget that fulfills the quality criterion of a minimum spot weld diameter of 4*√t, leads to partial reaustenitization and consequently to a ferritic/martensitic microstructure after final quenching. Hardness mappings revealed that this inner FZ is harder than the surrounding FZ consisting of tempered martensite. In contrast, if the highest current without splashing is chosen for the first pulse, the same second pulse does not reaustenitize the FZ but only temper the martensite.

Modeling and Simulation of Q&P Steels

2016 ◽  
Vol 879 ◽  
pp. 1454-1458
Author(s):  
Georg Paul ◽  
Richard G. Thiessen
Keyword(s):  
Automotive Industry ◽  
High Strength Steels ◽  
High Strength ◽  
The Body ◽  
Special Focus ◽  
High Tensile Strength ◽  
Advanced High Strength Steels ◽  
Passenger Safety ◽  
Steel Grades ◽  
Body In White

Two important objectives of the automotive industry are the decrease of the body-in-white weight and the improvement of the passenger safety. High strength steels (HSS) are widely used to achieve these objectives. Quenching and partitioning (Q&P) has recently been proposed to achieve high strength steel grades for the third generation of advanced high strength steels (AHSS), which contain a considerable amount of retained austenite. Due to their microstructure these new steel grades combine a high tensile strength with good elongation values, as long as cementite precipitation is avoided. A model describing the involved phase transformations is presented. Special focus is put on the cementite precipitation and how it is influenced by silicon and aluminum additions.

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