Kinetic Model for the Phase Transformation of High-Strength Steel Under Arbitrary Cooling Conditions

2018 ◽  
Vol 25 (2) ◽  
pp. 381-395 ◽  
Author(s):  
Hao Zhao ◽  
Xiuli Hu ◽  
Junjia Cui ◽  
Zhongwen Xing
Keyword(s):  
Phase Transformation ◽  
Kinetic Model ◽  
High Strength Steel ◽  
High Strength ◽  
Cooling Conditions

Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints

2020 ◽  
Vol 62 (9) ◽  
pp. 891-900
Author(s):  
Jonas Hensel ◽  
Arne Kromm ◽  
Thomas Nitschke-Pagel ◽  
Jonny Dixneit ◽  
Klaus Dilger
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
High Strength Steel ◽  
Transformation Temperature ◽  
Fatigue Cracks ◽  
High Strength ◽  
Filler Material ◽  
Phase Transformation Temperature ◽  
Filler Materials

Abstract The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades.

scholarly journals Study on Phase Transformation in Hot Stamping Process of USIBOR® 1500 High-Strength Steel

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1119 ◽  
Author(s):  
Pengyun Zhang ◽  
Le Zhu ◽  
Chenyang Xi ◽  
Junting Luo
Keyword(s):  
Phase Transformation ◽  
High Strength Steel ◽  
Hot Stamping ◽  
High Strength ◽  
Transformation Kinetics ◽  
Martensite Content ◽  
Cct Curve ◽  
Stamping Process ◽  
Quenching Process ◽  
Kinetics Of

Based on the Kirkaldy-Venugopalan model, a theoretical model for the phase transformation of USIBOR® 1500 high strength steel was established, and a graph of the phase transformation kinetics of ferrite, pearlite, and bainite were plotted using the software MATLAB. Meanwhile, with the use of the software DYNAFORM, the thermal stamping process of an automobile collision avoidance beam was simulated. The phase transformation law of USIBOR® 1500 high-strength steel during hot stamping was studied through a simulation of the phase transformation during the pressure holding quenching process. In combination with the continuous cooling transformation (CCT) curve, the cooling rate of quenching must be greater than 27 °C/s to ensure maximum martensite content in the final parts, and the final martensite content increases as the initial temperature of the sheet rises.

scholarly journals Effects of Phase Transformation in Hot Stamping of 22MnB5 High Strength Steel

2017 ◽  
Vol 183 ◽  
pp. 316-321 ◽  
Author(s):  
Giulia Venturato ◽  
Michele Novella ◽  
Stefania Bruschi ◽  
Andrea Ghiotti ◽  
Rajiv Shivpuri
Keyword(s):  
Phase Transformation ◽  
High Strength Steel ◽  
Hot Stamping ◽  
High Strength

Principle and Model of Phase Transformation in Ultra-High Strength Steel for Cone Crusher

2016 ◽  
Vol 850 ◽  
pp. 636-641
Author(s):  
Wei Wang ◽  
Ren Bo Song ◽  
Shi Guang Peng ◽  
Ru Wen Zheng ◽  
Zhi Dong Tan ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Cooling Rate ◽  
High Strength Steel ◽  
High Strength ◽  
Lower Bainite ◽  
Transformation Model ◽  
Expansion Curve ◽  
Ultra High Strength Steel ◽  
Cone Crusher ◽  
High Degree

The principle of phase transformation in ultra-high strength steel for cone crusher was studied by DIL805 thermal mechanical simulate, and the critical temperature was determined. The Austenite continuous cooling transformation (CCT) diagram of the steel was confirmed by thermal expansion curve, dilatometry and metallography. The phase transformation model was established and offered a theory for deciding parameters of heat treatment process. The results proved that: when the cooling rate was under 0.5 °C/s, the structure was mainly Pearlite and Bainite. With the increase of cooling rate, the content of lower Bainite increased. When it came to 1°C/s , Martensite start to transform from Austenite. When the cooling rate is 5°C/s, Pearlite disappears, Bainite and Martensite were in the majority. Meanwhile, the mathematical equations of phase transformation have high degree to fit the experimental results, and the phase transformation model is feasible.

scholarly journals Thermomechanical-Phase Transformation Simulation of High-Strength Steel in Hot Stamping

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Wenhua Wu ◽  
Ping Hu ◽  
Guozhe Shen
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Phase Transformation ◽  
High Strength Steel ◽  
Hot Stamping ◽  
Constitutive Models ◽  
High Strength ◽  
Simulation Software ◽  
Transmission Model ◽  
Stamping Process

The thermomechanical-phase transformation coupled relationship of high-strength steel has important significance in forming the mechanism and numerical simulation of hot stamping. In this study a new numerical simulation module of hot stamping is proposed, which considers thermomechanical-transformation multifield coupled nonlinear and large deformation analysis. In terms of the general shell finite element and 3D tetrahedral finite element analysis methods related to temperature, a coupled heat transmission model for contact interfaces between blank and tools is proposed. Meanwhile, during the hot stamping process, the phase transformation latent heat is introduced into the analysis of temperature field. Next the thermomechanical-transformation coupled constitutive models of the hot stamping are considered. Static explicit finite element formulae are adopted and implemented to perform the full numerical simulations of the hot stamping process. The hot stamping process of typical U-shaped and B-pillar steel is simulated using the KMAS software, and a strong agreement comparison between temperature, equivalent stress, and fraction of martensite simulation and experimental results indicates the validity and efficiency of the hot stamping multifield coupled constitutive models and numerical simulation software KMAS. The temperature simulated results also provide the basic guide for the optimization designs of cooling channels in tools.

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