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

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.

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.

Prediction of Microstructure and Mechanical Properties in Hot Stamping

2014 ◽  
Vol 1063 ◽  
pp. 314-317
Author(s):  
Chao Wang ◽  
Bin Zhu ◽  
Yi Lin Wang ◽  
Yi Sheng Zhang
Keyword(s):  
Phase Transformation ◽  
Hot Stamping ◽  
Fuel Efficiency ◽  
Thin Sheet ◽  
High Strength ◽  
Transformation Model ◽  
Boron Steel ◽  
Stamping Process ◽  
Improved Model ◽  
Acceptable Agreement

Hot stamping process has been increasingly used in producing structural components of automobile to improve crash worthiness and fuel efficiency. Hot stamping process can produce ultimate tensile strength parts as high as 1500MPa. The high strength of hot –stamped components is attributed to the martensitic phase transformation which is transformed from austenite at elevated temperature. An improved model is developed based on Li’s phase transformation model to predict the austenite decomposition into ferrite, pearlite, bainite and martensite during arbitrary cooling paths for thin sheet boron steel. The simulated volume fractions and hardness profiles shows acceptable agreement to the corresponding experimental observations.

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.

scholarly journals Tribological Behavior of Laser Textured Hot Stamping Dies

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Andre Shihomatsu ◽  
Sergio Tonini Button ◽  
Iris Bento da Silva
Keyword(s):  
Surface Topography ◽  
High Pressures ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Tests ◽  
Textured Surface ◽  
Laser Texturing ◽  
Stamping Dies ◽  
Before And After

Hot stamping of high strength steels has been continuously developed in the automotive industry to improve mechanical properties and surface quality of stamped components. One of the main challenges faced by researchers and technicians is to improve stamping dies lifetime by reducing the wear caused by high pressures and temperatures present during the process. This paper analyzes the laser texturing of hot stamping dies and discusses how different surfaces textures influence the lubrication and wear mechanisms. To this purpose, experimental tests and numerical simulation were carried out to define the die region to be texturized and to characterize the textured surface topography before and after hot stamping tests with a 3D surface profilometer and scanning electron microscopy. Results showed that laser texturing influences the lubrication at the interface die-hot sheet and improves die lifetime. In this work, the best texture presented dimples with the highest diameter, depth, and spacing, with the surface topography and dimples morphology practically preserved after the hot stamping tests.

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．

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.

Failure analysis of heat treated HSLA wheel bolt steels

2010 ◽  
Vol 6 (3) ◽  
pp. 373-382
Author(s):  
Ali Nazari ◽  
Shadi Riahi
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Failure Analysis ◽  
Heat Treating ◽  
Boron Steel ◽  
Content Type ◽  
Heat Treated ◽  
Before And After ◽  
Molybdenum Steel ◽  
Optimum Heat

PurposeThe aims of this study is to analyze failure of two types of high‐strength low‐alloy (HSLA) steels which are used in wheel bolts 10.9 grade, boron steel and chromium‐molybdenum steel, before and after heat treatment.Design/methodology/approachThe optimum heat treatment to obtain the best tensile behavior was determined and Charpy impact and Rockwell hardness tests were performed on the two steel types before and after the optimum heat treating.FindingsFractographic studies show a ductile fracture for heat‐treated boron steel while indicate a semi‐brittle fracture for heat‐treated chromium‐molybdenum steel. Formation of a small boron carbide amount during heat treating of boron steel results in increment the bolt's tensile strength while the ductility did not changed significantly. In the other hand, formation of chromium and molybdenum carbides during heat treating of chromium‐molybdenum steel increased the bolt's tensile strength with a considerable reduction in the final ductility.Originality/valueThis paper evaluates failure analysis of HSLA wheel bolt steels and compares their microstructure before and after the loading regime.

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