The Study on Weldability of Boron Steel and Hot-Stamped Steel by Using Laser Heat Source (II) - Laser Weldability of Hot Stamping Steel with Ultra-High Strength -

In the automotive industry, the hot forming of high strength steels offers the possibility to obtain significant reduction of weight without affecting the structural performances of final products. The main reason of its restricted application in the industry lies however in the lack of basic knowledge about mechanical and microstructural characteristics of sheets at elevated temperature, boundary conditions, and other process parameters. To partially overcome this limitation, this paper presents a research on the material properties of the hot stamping steel 22MnB5. Sheets of boron steel 22MnB5 with a thickness of 3.8mm were investigated and the results of experimental hot stamping tests were considered. The yield strength (YS) reached about 1200MPa, tensile strength (TS) reached 1500MPa, microhardness reached over 450HV at heating temperature of 880°C and holding 5 min.

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A Study on Laser Weldability of Al-Si Coated Boron Steel According to Hot-Stamping Heat Treatment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1110.113 ◽

2015 ◽

Vol 1110 ◽

pp. 113-117

Author(s):

Jong Do Kim ◽

So Young Choi ◽

Moo Keun Song

Keyword(s):

Heat Treatment ◽

Coating Layer ◽

Hot Stamping ◽

Fuel Efficiency ◽

High Strength ◽

Boron Steel ◽

Dimensional Precision ◽

Before And After ◽

Hot Stamped Steel ◽

High Level

Numerous studies recently have been conducted to reduce the weight of finished products and increase their fuel efficiency by using hot-stamping processes in the transport industry. Hot-stamping is a method where boron steel is formed and cooled in a press die directly after it is heated to a temperature of 900 °C or higher to obtain a material with a high-strength of 1,500 MPa or more. It is advantageous in that a high level of quality can be ensured because the spring-back phenomenon, a problem associated with high-strength steel materials, can be overcome while the degree of dimensional precision is improved by 90 % or more due to the good formability compared with existing types of steel. In this study, specimens were welded with a laser before and after the hot-stamping process of boron steel, welding characteristics according to heat treatment were elucidated, and mechanical properties were compared. Also, the effect of laser welding on flow from the Al-Si coating layer into the weld was investigated through an analysis of microstructure. The obtained results indicated that, in the case of the boron steel, hardness increased rapidly at the weld. For the hot-stamped steel, there was a sharp reduction of the hardness by tempering in the HAZ. It was found that the Al-Si coating layer flowed into the weld and was segregated when welding was carried out. This resulted in reduced hardness of the weld.

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THERMAL EFFECT IN FSPL HEAT CONDUCTION MODEL IRRADIATED BY LASER HEAT SOURCE

Proceeding of Proceedings of CHT-15. 6th International Symposium on ADVANCES IN COMPUTATIONAL HEAT TRANSFER , May 25-29, 2015, Rutgers University, New Brunswick, NJ, USA ◽

10.1615/ichmt.2015.intsympadvcomputheattransf.50 ◽

2015 ◽

Author(s):

T. N. Mishra ◽

Kabindra Nath Rai

Keyword(s):

Heat Conduction ◽

Heat Source ◽

Thermal Effect ◽

Conduction Model ◽

Heat Conduction Model ◽

Laser Heat ◽

Laser Heat Source

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Hot Stamping Processing Experiments of Quenchable Boron Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.575-578.299 ◽

2008 ◽

Vol 575-578 ◽

pp. 299-304 ◽

Cited By ~ 3

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.

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Development of Multi-Axis Laser-Assisted Milling Device

Volume 1: Processes ◽

10.1115/msec2017-2864 ◽

2017 ◽

Author(s):

Dong-Hyeon Kim ◽

Wan-Sik Woo ◽

Won-Shik Chu ◽

Sung-Hoon Ahn ◽

Choon-Man Lee

Keyword(s):

Heat Source ◽

Tool Path ◽

Cutting Tool ◽

Field Studies ◽

Flat Surfaces ◽

Laser Heat ◽

Complex Shapes ◽

Laser Heat Source ◽

Removal Processes ◽

Machining Productivity

Laser-assisted machining (LAM) process is an effective method to facilitate material removal processes for difficult-to-cut materials. In LAM process, the mechanical strength of various materials is reduced by a laser heat source focused in front of the cutting tool during machining. Since the laser heat source is located ahead of the cutting tool, the workpiece is preheated by the heat source. This enables difficult-to-cut materials to be machined more easily with low cutting energy, increasing the machining productivity and accuracy. It is difficult to apply laser-assisted milling (LAMilling) to workpieces having complex shapes, because it is not easy to control laser preheating and the cutting tool path for three-dimensionally shaped workpieces. LAMilling has only been used in limited fields such as single-direction machining of flat surfaces. To apply this process in the industrial field, studies on workpieces having various shapes are needed. This study aims to develop a laser-assisted milling device having multiple axes and to investigate the machining characteristics of several difficult-to-cut materials.

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Laser Lock-In Thermography for Fatigue Crack Detection

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.558.76 ◽

2013 ◽

Vol 558 ◽

pp. 76-83 ◽

Cited By ~ 1

Author(s):

Yun Kyu An ◽

Ji Min Kim ◽

Hoon Sohn

Keyword(s):

Fatigue Crack ◽

Heat Source ◽

High Power ◽

Crack Detection ◽

Laser Source ◽

Cw Laser ◽

Laser Heat ◽

Laser Heat Source ◽

Fatigue Crack Detection ◽

Lock In

This study proposes a new nondestructive evaluation methodology named laser lock-in thermography (LLT) for fatigue crack detection. LLT utilizes a high power continuous wave (CW) laser as a heat generation source for lock-in thermography instead of commonly used flash and halogen lamps. The advantages of the proposed LLT method are that (1) the laser heat source can be positioned at an extended distance from a target structure thank to the directionality and low energy loss of the laser source, (2) thermal image degradation due to surrounding temperature disturbances can be minimized because of high temperature gradient generated by the laser source and (3) a large target surface can be inspected using a scanning laser heat source. The developed LLT system is composed of a modulated high power CW laser, galvanometer and infrared camera. Then, a holder exponent-based data processing algorithm is proposed for intuitive damage evaluation. The developed LLT is employed to detect a micro fatigue crack in a metal plate. The test result confirms that 5 μm (or smaller) fatigue crack in a dog-bone shape aluminum plate with a dimension of 400 x 140 x 3 mm3 can be detected.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.184-185.333 ◽

2012 ◽

Vol 184-185 ◽

pp. 333-336 ◽

Cited By ~ 2

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．

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

Metals ◽

10.3390/met10091136 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1136 ◽

Cited By ~ 1

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.

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