scholarly journals Study on Bending Beam Delayed Cracking of Ultra High-strength DP Steel for Automotive Use

2021 ◽  
Vol 1906 (1) ◽  
pp. 012003
Author(s):  
Wan Rongchun ◽  
Fang Yimeng ◽  
Fu Liming ◽  
Cao Baoshan ◽  
Ma Qingyan ◽  
...  
Keyword(s):  
High Strength ◽  
Dp Steel ◽  
Delayed Cracking

The Microstructure and Formability Study on DP Steel of Lightweight Automobile

2011 ◽  
Vol 704-705 ◽  
pp. 1465-1472
Author(s):  
Jin Wu ◽  
Da Sen Bi ◽  
Liang Chu ◽  
Jian Zhang ◽  
Yun Tao Li
Keyword(s):  
Mechanical Property ◽  
Work Hardening ◽  
High Strength Steel ◽  
High Strength ◽  
Mathematic Model ◽  
Theoretical Research ◽  
Forming Limit ◽  
Strain Hardening Exponent ◽  
Dp Steel ◽  
Better Than

Dual phase (DP) steel is a high strength steel for auto-panel. In this paper, mechanical property, forming ability, baked-hardening and work hardening properties of high strength steel DP450 are studied by experiments, and compared with those of steel MS6000.And theoretical research on predicting the forming limit of steel DP450 by the NADDRG model. The established mathematic model for relativity is of practical usefulness. Experimental results reveal that the yield strength of steel DP450 is about 7.2% lower than the MS6000,and the break strength increases by 18.9%,while the elongation increases by 19%.The strain hardening exponent of steel DP450 are superior to those of MS6000.The results show that mechanical property of high strength steel DP450 is better than that of MS6000,while forming ability of DP450 is not lower than that of MS6000.And baked-hardening and work hardening properties of steel DP450 are better than those of MS6000.The steel sheet DP450 owned a good forming ability.

Fatigue life performance of multi-material connections hybrid joined by self-piercing rivets and adhesive

2020 ◽  
Vol 62 (10) ◽  
pp. 973-978
Author(s):  
Jan Presse ◽  
Thorsten Michler ◽  
Boris Künkler
Keyword(s):  
Fatigue Life ◽  
Lightweight Design ◽  
Sheet Thickness ◽  
High Strength ◽  
Material Design ◽  
Design Solution ◽  
Cyclic Loads ◽  
Dp Steel ◽  
Joining Technology ◽  
Structural Adhesive

Abstract The multi-material design presented contains EN AW-6016 aluminum and high strength CR330Y590T-DP steel. This dissimilar combination is an example of an affordable lightweight design solution, but it requires an adapted joining technology. Hybrid joining technologies such as selfpiercing riveting (SPR) in combination with a structural adhesive enables an assembly of such dissimilar material combinations. In addition to higher manufacturing costs for mechanical joining the design process still requires a great amount of effort. This study provides a simple approach for assessing hybrid joined multi-material connections. Therefore, tests for several combinations of the most relevant parameters on fatigue life (material properties, sheet thickness, load cases) were performed under quasi-static and cyclic loads. Based on the data acquired, it is shown that the fatigue life of hybrid joined connections can be estimated by superposing the contributing fatigue life of purely SPR and purely adhesive joints.

Microstructural Evolution and Fracture Mechanism for Scar Defect Formation on Advanced High Strength Steel during a Shearing Process

2020 ◽  
pp. 1-22
Author(s):  
Onnjira Diewwanit ◽  
Paranee Keawcha-um ◽  
Thanita Keawcha-um ◽  
Weesuda Petchhan ◽  
Sutasn Thipprakmas
Keyword(s):  
Stress Distribution ◽  
Tensile Test ◽  
Fracture Mechanism ◽  
Defect Formation ◽  
Flow Direction ◽  
High Strength ◽  
Distribution Analysis ◽  
Dp Steel ◽  
Tensile Test Specimen ◽  
Cut Edge

Abstract To form a required shape of the advanced high strength steels especially DP steel sheets, shearing process being one of major processes is commonly used. In general, although the good cut-edge with small fracture could be achieved by setting small shearing clearance, the tearing being a major defect commonly occurred on the cut-edge. Therefore, in the present research, a tearing mechanism on the DP steel sheet, grade SPFC980Y (JIS) during shearing process is investigated and clearly clarified based on the microstructure evolution, fracture mechanism, and stress distribution analysis. The microstructure evolutions on both tensile test specimen and sheared workpiece were performed to clarify the fracture mechanism. The angle between shear band and elongated grain flow direction is examined based on tensile test and it is used to predict an angle of initial fracture and its propagation on the shearing process as well. By associated with stress distribution analysis generated in shearing zone during shearing phase, the results revealed that the fracture propagated out of shearing zone and the fracture could be easily delayed. This resulted in that the tearing could be generated in the case of SPFC980Y. Vice versa, the fracture propagation is all in shearing zone, the fracture could not be delayed and the fracture completely generated on the cut-edge in the case of SPCC. In the present resents, the tearing mechanism on the DP steels in shearing process is clearly characterized.

Development of Laminar Flow Cooling of Ultra-High Strength Ferrite-Bainite Dual Phase Steel

2012 ◽  
Vol 184-185 ◽  
pp. 940-943
Author(s):  
Wei Lv ◽  
Di Wu ◽  
Zhuang Li
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Laminar Flow ◽  
Hot Rolling ◽  
Retained Austenite ◽  
High Strength ◽  
Total Elongation ◽  
Granular Bainite ◽  
Dual Phase ◽  
Dp Steel

In the present paper, controlled cooling in different ways was performed using a laboratory hot rolling mill in ultra-high strength hot rolled ferrite-bainite dual phase (DP) steel. The results have shown that the final microstructures of DP steel comprise ferrite, bainite and a small amount of retained austenite and martensite. DP steel has a tensile strength ranging from 1010 to 1130MPa and yet retains considerable total elongation in the range of 14–17%. The addition of Mn and Nb to DP steel leads to the maximum ultimate tensile strength, yield strength and the product of ultimate tensile strength and total elongation due to the formation of retained austenite and granular bainite structure. Laminar flow cooling after hot rolling results in a significant increase in the quantity of ferrite and bainite due to the suppression of pearlite transformation, and as a result, the present steel possesses high strengths and good toughness.

Computer Simulation of Hot Stamping Process of DP Steel Car Bumper Chain Based on Dynaform

2012 ◽  
Vol 178-181 ◽  
pp. 2877-2880
Author(s):  
Han Wu Liu ◽  
Zhao Hui Liu ◽  
Hui Xiao Li ◽  
Shao Bo Ping
Keyword(s):  
Metal Forming ◽  
Steel Plate ◽  
Hot Stamping ◽  
High Strength ◽  
Spring Back ◽  
Temperature Field Distribution ◽  
Dp Steel ◽  
Performance Requirements ◽  
Stamping Process ◽  
Duplex Steel

Owing to the advantages of weight loss and security, duplex steel plate has been the priority for the saloon car body instead of ordinary one among a majority of engine factories. While there are undesirable phenomena because of its high strength at normal temperature, such as its formability is worsened dramatically, and failure and fracture always occur in the stamping. So hot stamping process must be adopted to make the formability available. Based on the Bumper chain of Beijing Hyundai Reina and taken DP600 high strength steel as research object, this paper analyzes the distributions of stress, strain and thickness changes during the process of sheet metal forming by using eta/DYNAFORM software, simulates the spring-back quantity after hot stamping forming, and the numerical simulation of the temperature field distribution with time during stamping process was done. The result shows that duplex steel plate can meet the performance requirements of automotive chain forming, which offers theory basis for the production of such parts.

Wear Resistance Research of Advanced High Strength Steels

2016 ◽  
Vol 850 ◽  
pp. 197-201
Author(s):  
Chao Zhi ◽  
Yi Fei Gong ◽  
Ai Min Zhao ◽  
Jian Guo He ◽  
Ran Ding
Keyword(s):  
Wear Resistance ◽  
Twip Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Wear Performance ◽  
Dp Steel ◽  
Advanced High Strength Steels ◽  
Wear Mode ◽  
Surface Phase Transformation

The wear performance and wear mechanism under two-body abrasion of five advanced high strength steels, i.e. Nanobainite (NB) steel, Tempered Martensitic (TM) steel, Dual Phase (DP) steel, Transformation Induced Plasticity (TRIP) Steel and Twining Induced Plasticity (TWIP) steel were studied. By using the scanning electron microscopy (SEM), we investigated the wearing surface. Phase transformation strengthening behavior was also be discussed by analyzing the surface and sub-surface after abrasion. The results showed that micro-cutting was the major role of wear mode in the condition of two-body abrasion. In the circumstance of two-body abrasion, hardness was an important factor, the property of wear resistance enhanced while the hardness increased except for TM steel. NB steel possessed the best wear resistance which was 1.71 times higher than that of TWIP steel. The retained austenite transformed into martensite which can improve the hardness so that it enhanced the wear resistance of NB steel.

Thermo-Mechanical Simulation of Ultra-High Strength Ferrite-Bainite Dual Phase Steel

2012 ◽  
Vol 184-185 ◽  
pp. 1367-1370
Author(s):  
Wei Lv ◽  
Di Wu ◽  
Zhuang Li
Keyword(s):  
Cooling Rate ◽  
Dual Phase Steel ◽  
High Strength ◽  
Solute Drag ◽  
Dual Phase ◽  
Drag Effect ◽  
Dp Steel ◽  
Mechanical Simulation ◽  
Austenite Grain ◽  
Fast Cooling

In the present paper, thermo-mechanical simulation of ultra-high strength ferrite-bainite dual phase (DP) steel was performed using a thermomechanical simulator. Continuous cooling transformation (CCT) diagram was constructed for DP steel. The effects of composition and cooling rate on the kinetics and products of phase transformation and the form of the CCT diagram were investigated. The results have shown that the α→γ transformation in DP steel was found to be more sluggish due to the addition of alloying elements. The segregation of manganese and niobium at austenite grain boundaries is expected to cause a solute drag effect, thereby reducing the rate of γ→α transformation in DP steel. The pearlite transformation region disappeared for cooling rates from 0.1 to 20°C/s. The microstructure comprises of bainite and martenite was obtained at fast cooling rate. The present steel is expected to have a higher hardenability.

Formation Mechanism of Hydrogen-Induced Delayed Cracking in Weld Center of High-Strength Steel

2012 ◽  
Vol 557-559 ◽  
pp. 1304-1307 ◽  
Author(s):  
Jing Qiang Zhang ◽  
Jian Guo Yang ◽  
Jia Jie Wang ◽  
Xue Song Liu ◽  
Zhi Bo Dong ◽  
...  
Keyword(s):  
Residual Stress ◽  
Formation Mechanism ◽  
Welded Joints ◽  
High Strength Steel ◽  
Hydrogen Pressure ◽  
High Strength ◽  
Welding Residual Stress ◽  
Cracking Behavior ◽  
Hydrogen Damage ◽  
Delayed Cracking

Based on the estimation of the critical hydrogen pressure and concentrations required for hydrogen-induced delayed cracking in high-strength steel, the conclusion that welded joints are hydrogen pressure microcracks body can be drawn under certain conditions. Through the analysis of the relationship between the microstructure evolution of welded joints, diffusion enrichment of hydrogen and cracking behavior, the formation mechanism of hydrogen-induced delayed cracking in weld center of high-strength steel joints is analyzed and the mechanism that stress induced the residual diffusion hydrogen gathered to promote the hydrogen pressure microcracks propagation is proposed. The research shows that the initation and propogation of hydrogen-induced delayed cracking in weld center can be divided into two stages, i.e. irreversible hydrogen damage stage and reversible hydrogen damage stage. In irreversible stage hydrogen pressure is the main causes of the initation of microcracks, while in reversible stage welding residual stress and residual diffusible hydrogen are necessary conditions for microcracks growth. The microcracks growth can be controlled by regulating welding residual stress.

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