scholarly journals Research on the Re-Deformation Characteristics of Hot Stamping of Boron Steel Parts with Tailored Properties

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1136 ◽  
Author(s):  
Ling Kong ◽  
Yan Peng ◽  
Caiyi Liu
Keyword(s):  
Grain Boundaries ◽  
Initial Phase ◽  
Hot Stamping ◽  
High Strength ◽  
Boron Steel ◽  
Deformation Characteristics ◽  
Maximum Strain ◽  
Soft Zone ◽  
Local Misorientation

Traditional hot-stamping products have super-high strength, but their plasticity is usually low and their integrated mechanical properties are not excellent. Functionally graded property structures, a relatively novel configuration with a higher material utilization rate, have increasingly captured the attention of researchers. Hot stamping parts with tailored properties display the characteristics of local high strength and high plasticity, which can make up for the limitations of conventional hot stamping and optimize the crash safety performance of vehicles. This new idea provides a means of personalized control in the hot-stamping process. In this paper, a new strategy of local induction heating and press hardening was used for the hot stamping of boron steel parts with tailored properties, of which the microstructure from the hard zone to the soft zone shows a gradient distribution consisting of a martensite phase, multiphase and initial phase, with the hardness ranging from 550 HV to 180 HV. The re-deformation characteristics of hot stamping parts with tailored properties have been studied through the uniaxial tensile test, in cooperation with digital image correlation (DIC) and electron backscattered diffraction (EBSD) techniques. The experiments show that there are easily observable strain distribution characteristics in the re-deformation of hot stamping parts with tailored properties. In the process of tensile deformation, the initial phase zone takes the role of deformation and energy absorption, with the maximum strain before necking reaching 0.32. The local misorientation of this zone was high, and a large number of low angle grain boundaries were formed, while the proportion of small angle grain boundaries increased from 13.5% to 63.3%, and the average grain size decreased from 8.15 μm to 3.43 μm. Meanwhile, the martensite zone takes on the role of anti-collision protection, with a maximum strain of only 0.006, and its local misorientation is mostly unchanged. The re-deformation experimental results show that the hot stamping of boron steel parts with tailored properties meets the functional requirements of a hard zone for anti-collision and a soft zone for energy absorption, suitable for automobile safety parts.

Hot Stamping Processing Experiments of Quenchable Boron Steel

2008 ◽  
Vol 575-578 ◽  
pp. 299-304 ◽  
Author(s):  
Jun Bao ◽  
Zhong Wen Xing ◽  
Yu Ying Yang
Keyword(s):  
Heating Temperature ◽  
Hot Stamping ◽  
Cooling Water ◽  
High Strength ◽  
Processing Parameters ◽  
Boron Steel ◽  
Complicated Shape ◽  
Water Flow Velocity ◽  
Ultra High Strength Steel ◽  
Automotive Parts

The quenchable boron steel is a novel type of ultra high strength steel used for automotive parts so as to reduce the weight of the whole automobile. The hot stamping processing experiments for bending parts were studied. The influence of the hot stamping processing parameters, such as the heating temperature, the heat holding time and the cooling water flow velocity, on the mechanics properties and microstructure of the hot stamping parts is obtained. And then the optimal ranges of these parameters are determined, which provides a basis for the control of the hot stamping process applied in complicated shape parts’ production.

Numerical Simulation and Optimization of Cooling Ducts Layout in Hot Stamping Die

2012 ◽  
Vol 184-185 ◽  
pp. 333-336 ◽  
Author(s):  
Hui Xie ◽  
Ya Ke Chen
Keyword(s):  
Heat Transfer ◽  
Hot Stamping ◽  
Cooling Water ◽  
High Strength ◽  
Bulk Flow ◽  
Boron Steel ◽  
Press Hardening ◽  
Simulation And Optimization ◽  
Stamping Die ◽  
Cooling Ducts

Abstract. As an innovative process of manufacturing ultra high strength steel (UHSS), hot stamping or press hardening is a multi-physical coupling process with complex changes in thermal, mechanical and phase transformation. In this work, in order to study heat transfer from workpiece to upper & lower die and cooling water, a new approach, named Bulk Flow, is adopted to model the cooling ducts and to simulate heat transfer in hot stamping die. Not only can tool design, cooling duct layout and process parameters be studied and optimized to increase the cooling rate and to homogenize temperature distribution in workpiece, but also, the precision of hot stamping simulation be improved. The experimental results of boron steel components formed by the designed die show that the martensite is homogenous. It indicates the feasibility of the bulk flow method．

High Temperature Heat Transfer During Hot Forming Die Quenching of Boron Steel

2013 ◽  
Author(s):  
Etienne Caron ◽  
Kyle J. Daun ◽  
Mary A. Wells
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cooling Rate ◽  
Hot Stamping ◽  
High Strength ◽  
Hot Forming ◽  
Boron Steel ◽  
Steel Blank ◽  
Die Quenching

Distributed mechanical properties can be obtained in ultra high strength steel parts formed via hot forming die quenching (HFDQ) by controlling the cooling rate and microstructure evolution during the quenching step. HFDQ experiments with variable cooling rates were conducted by quenching Usibor® 1500P boron steel blanks between dies pre-heated up to 600°C. The heat transfer coefficient (HTC) at the blank / die interface, which is used to determine the blank cooling rate, was evaluated via inverse heat conduction analysis. The HTC was found to increase with die temperature and stamping pressure. This heat transfer coefficient increase was attributed to macroscopic flattening of the boron steel blank as well as microscopic deformation of surface roughness peaks. At the end of the hot stamping process, the HTC reached a pressure-dependent steady-state value between 4320 and 7860 W/m2·K when the blank and die temperatures equalize.

Flow Behavior of Ultra-High Strength Boron Steel at Elevated Temperature

2011 ◽  
Vol 704-705 ◽  
pp. 191-195
Author(s):  
Jun Bao ◽  
Hong Sheng Liu ◽  
Zhong Wen Xing ◽  
Bao Yu Song ◽  
Yu Ying Yang
Keyword(s):  
Elevated Temperature ◽  
Strain Rate ◽  
Flow Behavior ◽  
Hot Stamping ◽  
Testing Machine ◽  
High Strength ◽  
Mathematic Model ◽  
Boron Steel ◽  
Stress Strain ◽  
Simulation Testing

Ultra-high strength boron steel is widely used in a new hot stamping technology which is hot formed and die quenched simultaneously in order to obtain stamping parts with 1500MPa tensile strength or higher. Tensile experiments were carried out with ultra-high strength boron steel in a range of temperature 500°C~860°Cand strain rate 0.01/s~1/s with the thermal simulation testing machine Gleeble 3800, and the stress-strain curves were obtained. The influences of the deformation temperature and strain rate on the stress-strain curves were analyzed. The results show that hot behavior at elevated temperature of ultra-high strength boron steel consists of strain hardening and dynamic recovery mechanism, which can be accurately described by the mathematic model. Keywords: Ultra-high strength boron steel, hot stamping, hot flow behavior

Wear Behaviour of Al-Si and Zn Coated 22MnB5 in Hot Stamping

2014 ◽  
Vol 966-967 ◽  
pp. 209-218
Author(s):  
Paolo F. Bariani ◽  
Stefania Bruschi ◽  
Andrea Ghiotti ◽  
Francesco Medea
Keyword(s):  
Hot Stamping ◽  
Testing Machine ◽  
High Strength Steels ◽  
Thermal Conditions ◽  
High Strength ◽  
Normal Pressure ◽  
Positive Influence ◽  
Wear Behaviour ◽  
Boron Steel ◽  
Process Step

Hot stamping of quenchenable high strength steels represents the most promising forming technology for the manufacturing of safety and crash relevant car parts. In such process, the manganese-boron steel 22MnB5 is homogeneously austenitized, formed and subsequently quenched in one process step, so that complex geometric structural components can be formed with an ultimate tensile strength up to 1500 MPa. Due to the high temperature, no lubrication is used during the process with consequent high wear and reduced service-life of the dies. Commercial available steel blanks usually present an Al-Si coating that has been specifically developed as a protection from oxidation and decarburization and, at the same time, has proved positive influence also on the decreasing the friction at interface between the blank and the dies during the forming. Although such coating is generally accepted as the only lubrication medium in hot stamping, its performances are considered not appropriate for a good lubrication. The paper presents the comparison of the standard Al-Si coating and a new Zn coating when applied to metal sheets in hot stamping. A novel apparatus to investigate the tribological conditions during sheet metal working processes is presented. In addition to the control of mechanical (i.e. normal pressure) and kinematic parameters (i.e. sliding speed, sliding length), the developed testing machine permits to reproduce the thermal fields and monitor the thermal conditions of the sheet and tool materials. Experiments were carried out on Zn coated 22MnB5 sheets in the range between 700° and 950°C and compared with the performances of the commercial Al-Si coating. The coating performances are investigated for different heating temperatures and soaking times.

Investigation on tribological characteristics of boron steel 22MnB5–tool steel H13 tribopair at high temperature

2016 ◽  
Vol 231 (2) ◽  
pp. 165-175 ◽  
Author(s):  
Yanhong Mu ◽  
Baoyu Wang ◽  
Mingdong Huang ◽  
Jing Zhou ◽  
Xuetao Li
Keyword(s):  
High Temperature ◽  
Friction Coefficient ◽  
Tool Steel ◽  
Laser Scanning ◽  
Hot Stamping ◽  
High Strength ◽  
Tribological Characteristics ◽  
Confocal Laser ◽  
Boron Steel ◽  
Boron Steels

In the background that the quenchable boron steels have been widely used to manufacture body-in-white by hot stamping because of its ultra-high strength, the understanding of frictional characteristics of the boron steel–tool steel tribopair at high temperature should be deepened. In this work, the friction behaviors of the tool steel H13 against the boron steel 22MnB5 were investigated at different temperatures, sliding velocities, contact pressures, and lubrication conditions by ring-on-disc sliding testing. The tribological characteristics were analyzed through scanning electron microscope and confocal laser scanning. The results show the relationship between the friction coefficient and the hot stamping parameters well. The friction coefficient decreases remarkably with the increasing temperature and contact pressure, but sliding velocity has no noticeable influence on the friction coefficient. The wear mechanism also changes with different process parameters and the main mechanism is a combination of adhesive and abrasive wear. Furthermore, MoS2 lubricant can reduce the friction coefficient effectively and protect the die from severe wear.

scholarly journals Effect of the Die Temperature and Blank Thickness on the Formability of a Laser-Welded Blank of a Boron Steel Sheet with Removing Al-Si Coating Layer

2014 ◽  
Vol 6 ◽  
pp. 925493 ◽  
Author(s):  
M. S. Lee ◽  
J. H. Moon ◽  
C. G. Kang
Keyword(s):  
Automobile Industry ◽  
Steel Sheet ◽  
Coating Layer ◽  
Hot Stamping ◽  
Thin Sheet ◽  
Welding Process ◽  
High Strength ◽  
Absorption Capacity ◽  
Boron Steel ◽  
Thick Sheet

Reducing carbon emissions has been a major focus in the automobile industry to address various environmental issues. In particular, studies on parts comprised of high strength sheets and light car bodies are ongoing. Accordingly, this study examined the use of boron steel, which is commonly used in high strength sheets. Boron steel is a type of sheet used for hot stamping parts. Although it has high strength, the elongation is inferior, which reduces its crash energy absorption capacity. To solve this problem, two sheets of different thickness were welded so the thin sheet would absorb crash energy and the thick sheet would work as a support. Boron steel, however, may show weakening at the welding spot due to the Al-Si coating layer used to prevent oxidation from occurring during the welding process. Therefore, a certain part of the coating layer of a double-thickness boron steel sheet that is welded in the hot stamping process is removed through laser ablation, and the formability of the hot-work was examined.

High Toughness Alumina/Aluminate: The Role Of Hetero-Interfaces

1995 ◽  
Vol 409 ◽  
Author(s):  
M. E. Brito ◽  
M. Yasuoka ◽  
S. Kanzaki
Keyword(s):  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Fracture Mode ◽  
Auger Electron ◽  
High Strength ◽  
Interfacial Debonding ◽  
Amorphous Phases ◽  
High Toughness ◽  
Interface Structures

AbstractSilica doped alumina/aluminate materials present a combination of high strength and high toughness not achieved before in other alumina systems, except for transformation toughened alumina. We have associated the increase in toughness to crack bridging by anisotropically grown alumina grains with concurrent interfacial debonding of these grains. A HREM study of grain boundaries and hetero-interface structures in this material shows the absence of amorphous phases at grain boundaries. Local Auger electron analysis of fractured surfaces revealed the coexistence of Si and La at the grain facets exposed by the noticeable intergranular fracture mode of this material. It is concluded that a certain and important degree of boundaries weakness is related to both, presence of Si at the interfaces and existence of alumina/aluminate hetero-interfaces.

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