Flow Curves Prediction of Heat Treated Boron Alloy Steels for Hot Stamping Process

2015 ◽  
Vol 658 ◽  
pp. 81-85
Author(s):  
Prapatsorn Srithananan ◽  
Pongpan Kaewtatip ◽  
Vitoon Uthaisangsuk
Keyword(s):  
Alloy Steel ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Optical Microscope ◽  
Stress Strain ◽  
Flow Curves ◽  
Press Hardening ◽  
Heat Treated ◽  
Alloy Steels

Automotive parts made of ultra-high strength steels (UHSS) have been increasingly produced by hot stamping or press hardening of boron alloy steel. In case of novel hot formed components with tailored properties, different heating cycles needed to be applied for different zones, in which varying microstructure characteristics were generated. Mechanical properties of these parts were thus precisely controlled by the microstructure constituents. In this work, stress-strain behaviors of a boron alloy steel undergoing different heat treatment conditions with respect to that modified hot stamping procedure were predicted. Firstly, boron alloy steel sheet specimens were heated up to the austenitization temperature. Afterwards, they were abruptly cooled down to the bainitic temperature range, held for different holding times and finally cooled to room temperature. The microstructures obtained from each condition were characterized by optical microscope (OM) using color tint etching. The stress-strain responses of all generated microstructures were determined by tensile test. By the modeling, flow curves of the individual single phases were described taking into account a dislocation theory based model and their chemical composition. Subsequently, effective flow curves of the heat treated boron alloy steels were calculated by means of the isostrain and non-isostrain method and were finally compared with the experimentally determined curves.

Cold Rolling Technique for Eliminating Cutting Process in Manufacturing Precise Product Using Non-Heat-Treated Micro Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 3235-3238 ◽  
Author(s):  
Seo Gou Choi ◽  
Duk Jae Yoon ◽  
Geun An Lee ◽  
Hee Woong Lee ◽  
Kyoung Hoan Na
Keyword(s):  
Alloy Steel ◽  
High Strength ◽  
Paper Analysis ◽  
Work Piece ◽  
Cross Wedge Rolling ◽  
Forming Process ◽  
Cold Forming ◽  
Heat Treated ◽  
Plastic Forming ◽  
Alloy Steels

In general micro alloy steel have the higher strength relative to conventional steels, which limits the utilization of conventional plastic forming processes. Incremental forming processes are more suitable for cold forming of such a high strength material. In particular, cold cross wedge rolling (CWR) can be a potential tool to fabricate axi-symmetric components with multi steps using high strength micro alloy steel. Obviously, optimization of die shape design is a crucial factor to apply cold cross wedge rolling to micro alloy steels. In this regards, a simulation-based process design using an elasto-plastic FEM has been carried out in order to obtain an optimum die shape for cold cross wedge rolling in this paper. Analysis results provided that the stretching angle and the shoulder angle at knifing and guiding zones were significant parameters for the stable forming process. It was demonstrated that proper stretching and shoulder angles reduced an excessive slip between a work piece and die in CWR process despite the condition of the low friction coefficient.

Numerical modeling of stress-strain relationships for advanced high strength steels

2021 ◽  
Vol 182 ◽  
pp. 106687
Author(s):  
Yu Xia ◽  
Chu Ding ◽  
Zhanjie Li ◽  
Benjamin W. Schafer ◽  
Hannah B. Blum
Keyword(s):  
Numerical Modeling ◽  
High Strength Steels ◽  
High Strength ◽  
Stress Strain ◽  
Advanced High Strength Steels

scholarly journals Forming a Flanged Hole When Quenching Press-Hardened Steel for Mechanical Fastening

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 721
Author(s):  
Yongjun Jeon ◽  
Hyunseok Choi ◽  
Dongearn Kim
Keyword(s):  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Expansion Ratio ◽  
Hardened Steel ◽  
Continuous Increase ◽  
Pilot Hole ◽  
Experimental Apparatus ◽  
Mechanical Fastening ◽  
Hole Flanging

The recent stringent regulations on vehicle safety and reducing CO2 emissions have led to a continuous increase in the application of press-hardened steel (PHS) in automobiles. Similar to other high-strength steels, assembling PHS components using the common welding techniques employed in automotive production lines is significantly difficult because of the surface coating layers and the additives within. This difficulty in post-processing, attributed to its high strength, also limits the mechanical fastening of PHS components. Therefore, this study aims to develop a process for forming a structure enabling mechanical fastening by sequentially applying piercing and hole-flanging operations during the hot stamping process. Our experimental apparatus was designed to perform the hole-flanging operation after the piercing operation within a single stroke at a specific temperature during the quenching process of PHS. At high temperatures of 440 °C or higher, the hole-flanging process was conducted in a direction opposite to that of the piercing operation for creating the pilot hole. An extruded collar with a height of 8.0 mm and a diameter of 17.5 mm was achieved, which is hole expansion ratio(HER) of 82.5%.

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.

Residual Stress at Fatigue Fracture Surface of Heat Treated High Strength Steels

1979 ◽  
pp. 227-232 ◽  
Author(s):  
Atsutomo Komine ◽  
Hideo Ueda ◽  
Eisuke Nakanishi ◽  
Shotaro Araki ◽  
Kazuo Taguchi
Keyword(s):  
Residual Stress ◽  
Fracture Surface ◽  
Fatigue Fracture ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Fracture Surface ◽  
Heat Treated

scholarly journals USE OF MULTI-PHASE TRIP STEEL FOR PRESS-HARDENING TECHNOLOGY

2019 ◽  
Vol 25 (2) ◽  
pp. 101 ◽  
Author(s):  
Hana Jirková ◽  
Kateřina Opatová ◽  
Štěpán Jeníček ◽  
Jiří Vrtáček ◽  
Ludmila Kučerová ◽  
...  
Keyword(s):  
Trip Steel ◽  
Physical Simulation ◽  
Isothermal Holding ◽  
High Strength Steels ◽  
High Strength ◽  
Press Hardening ◽  
Passenger Safety ◽  
Ultra High Strength Steels ◽  
New Treatments ◽  
Multi Phase

<p class="AMSmaintext">Development of high strength or even ultra-high strength steels is mainly driven by the automotive industry which strives to reduce the weight of individual parts, fuel consumption, and CO<sub>2</sub> emissions. Another important factor is to improve passenger safety. In order to achieve the required mechanical properties, it is necessary to use suitable heat treatment in addition to an appropriate alloying strategy. The main problem of these types of treatments is the isothermal holding step. For TRIP steels, the holding temperature lies in the field of bainitic transformation. These isothermal holds are economically demanding to perform in industrial conditions. Therefore new treatments without isothermal holds, which are possible to integrate directly into the production process, are searched. One way to produce high-strength sheet is the press-hardening technology. Physical simulation based on data from a real-world press-hardening process was tested on CMnSi TRIP steel. Mixed martensitic-bainitic structures with ferrite and retained austenite (RA) were obtained, having tensile strengths in excess of 1000 MPa.</p>

scholarly journals Microstructural Characterization Of Laser Heat Treated AISI 4140 Steel With Improved Fatigue Behavior

2015 ◽  
Vol 60 (2) ◽  
pp. 1331-1334 ◽  
Author(s):  
M.C. Oh ◽  
H. Yeom ◽  
Y. Jeon ◽  
B. Ahn
Keyword(s):  
Fatigue Strength ◽  
Alloy Steel ◽  
Microstructural Evolution ◽  
Fatigue Behavior ◽  
Microstructural Characterization ◽  
Optical Microscope ◽  
Heat Treated ◽  
Aisi 4140 ◽  
Ultrasonic Fatigue

Abstract The influence of surface heat treatment using laser radiation on the fatigue strength and corresponding microstructural evolution of AISI 4140 alloy steel was investigated in this research. The AISI 4140 alloy steel was radiated by a diode laser to give surface temperatures in the range between 600 and 800°C, and subsequently underwent vibration peening. The fatigue behavior of surface-treated specimens was examined using a giga-cycle ultrasonic fatigue test, and it was compared with that of non-treated and only-peened specimens. Fatigue fractured surfaces and microstructural evolution with respect to the laser treatment temperatures were investigated using an optical microscope. Hardness distribution was measured using Vickers micro-hardness. Higher laser temperature resulted in higher fatigue strength, attributed to the phase transformation.

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．

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