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Multi-scale Simulation on Bonding Mechanism of Solid-Liquid Cast-rolling of Cu/Al Cladding strip based on FEM and MD

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Journal of Wuhan University of Technology(Materials Science) 2019年第4期34卷 830-839页

作者： YAN Meng HUANG Huagui National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University

To explore the complex thermal-mechanical-chemical behavior in the solid-liquid cast-roll bonding(SLCRB) of Cu/Al cladding strip, numerical simulations were conducted from both macro and micro scales. In macro-scale, with birth and death element method, a thermo-mechanical coupled finite element model(FEM) was set up to explore the temperature and contact pressure distribution at the Cu/Al bonding interface in the SLCRB process. Taking these macro-scale simulation results as boundary conditions, we simulated the atom diffusion law of the bonding interface by molecular dynamics(MD) in micro-scale. The results indicate that the temperature in Cu/Al bonding interface deceases from 700 to 320 ℃ from the entrance to the exit of caster, and the peak of contact pressure reaches up to 140 MPa. The interfacial diffusion thickness depends on temperature and rolling reduction, higher temperature results in larger thickness, and the rolling reduction below kiss point leads to significant elongation deformation of cladding strip which yields more newborn interface with fresh metal and make the diffusion layer thinner. The surface roughness of Cu strip was found to be benefit to atoms diffusion in the Cu/Al bonding interface. Meanwhile, combined with the SEM-EDS observation on the microstructure and composition in the bonding interface of the experimental samples acquired from the castrolling bite, it is revealed that the rolling reduction and severe elongation deformation in the solid-solid contact zone below kiss point guarantee the satisfactory metallurgical bonding with thin and smooth diffusion layer. The bonding mechanisms of reactive diffusion, mechanical interlocking and crack bonding are proved to coexist in the SLCRB process.

关键词： Cu/Al cladding strip solid-liquid cast-roll bonding (SLCRB) bonding mechanism finite element method (FEM) molecular dynamics (MD)

Void Closure Behavior in Large Diameter Steel Rod during H-V rolling Process

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Journal of Iron and Steel research International 2014年第3期21卷 287-294页

作者： Hua-gui HUANG Yong LIU Feng-shan DU Lei CHEN National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University

In order to reveal the mechanism and condition of void closure in large diameter steel rod during horizontal- vertical （H-V） groove rolling process, a three-dimensional thermomechanicaily coupled finite element model was es- tablished for 9-stand H-V groove rolling process aiming at a 4150 mm steel rod production line. A spherical hole with diameter from 2 to 10 mm was preset into the center of continuous casting billet with a rectangle cross section of 300 mmX 360 mm in this model to simulate the void defect, and then finite element analyses were carried out to observe and quantify the void shape evolution in each pass on the three orthogonal coordinate plane sections. The re- suits showed that the void was formed roughly in the reduction and extension directions, and crushed gradually from spherical shape to an approximate ellipsoid, micro-crack and finally to be closed. A quantitative analysis was carried out by using elliptic radii and closure ratio to describe this evolution process; it indicated that the longest axis of the ellipsoid coincided with the rolling line, and the second and third axes were alternatively ihorizontal and vertical on the exit cross section according to change of the reduction direction in H-V groove. The void closure behavior during H- V rolling was more complicated than that of common horizontal rolling, and the influence of groove type and the ex- tension coefficient on the void closure ratio was presented. Finally, a pilot rolling experiment was performed on a 5- stand H-V experimental mill to verify the numerical simulation results, and the experimental results are in good agree- ment with the numerical simulation results.

关键词： large diameter steel rod continuous casting billet H-V groove rolling~ void closure FEM

A new mathematical model for predicting flow stress of X70HD under hot deformation

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Journal of Central South University 2015年第6期22卷 2052-2059页

作者：王健王小巩杨海涛余超肖宏 National engineering research center for Equipment and Technology of Cold rolling strip (Yanshan University) State Key Laboratory of rolling and Automation (Northeastern University)

To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and strain rates（0.01-10 s-1） on a Gleeble-3500 thermo-simulation machine. A new flow stress model was established. The linear and exponential relationship methods were applied to the parameters with respect to temperature and deformation rates. The rise of curve ends under certain conditions was analyzed. The flow stress of X70 HD steel predicted by the proposed model agrees well with the experimental results. So, it greatly improves the precision of the metal thermoplastic processing through finite element method and practical application of engineering.

关键词： flow stress dynamic recovery dynamic reerystallization Z parameter

Effect of rare earth alloying on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel at 650 ℃

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Journal of Rare Earths 2016年第4期34卷 447-452页

作者：陈雷龙红军刘鑫刚金淼马筱聪 National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University School of Mechanical engineering Yanshan University

The effect of rare earth（RE） on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel was investigated at 650 °C under different stress levels. It was found that RE could increase the time to creep rupture, especially at long-term creep duration. The logarithm of the time to creep rupture（lgtr） was a linear function of the applied stress（σ）. RE addition was favorable to generating a high fraction of low-coincidence site lattice（CSL） boundaries which was a possible cause for improving the creep rupture resistance. The fracture surface of RE-added steel exhibited less intergranular cracks suggesting the alteration on the nature of grain boundaries due to the presence of RE. RE addition changed the morphology of the intergranular chromium carbides from continuous network shape to fragmentary distribution which was another cause for longer creep duration. These results strongly suggested that the effect of RE alloying played a crucial role in improving the creep rupture resistance.

关键词： heat-resistant austenitic steel rare earths alloying creep rupture

Numerical simulation of fluid flow and free surface fluctuations during wheel and belt casting process

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Journal of Iron and Steel research International 2024年第5期31卷 1117-1126页

作者： Kun Gao Yan Peng National engineering research center for Equipment and Technology of Cold strip rolling Yanshan UniversityQinhuangdao066004HebeiChina

The unstable fluid flow and severe free surface fluctuations in the wheel and belt caster can affect the quality of the cast *** lower level height tends to entrap inclusions in the molten *** the other hand,the higher level height makes the production process more dangerous due to the overflow of high temperature fluid from the mold.A computational model of the molten metal pouring process was *** transient fluid flow and free surface fluctuations behavior were calculated using the three-dimensional large eddy simulation model and the volume of fluid *** results show that the flow velocity of the main jet gradually decreases under the influence of the low kinetic energy fluid in the *** is an obvious oscillation in the tail of the jet,while the flow field is asymmetric in *** jet is closer to the inside radius side due to the Coanda effect,and there is a recirculation zone on the inside radius and the outside radius respectively,according to the 10 s time-averaged *** with the industrial observation and simulation results,the shape of the free surface is a wave that varies with *** addition,the free surface height is lowest and the flow velocity is highest in the region near the jet.

关键词： Fluid flow Free surface Wheel and belt caster Large eddy simulation Volume of fluid method

Corrected stress field intensity approach based on averaging superior limit of intrinsic damage dissipation work

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Journal of Iron and Steel research International 2018年第10期25卷 1094-1103页

作者： Hao-ran Li Yan Peng Yang Liu Ming Zhang National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University Qinhuangdao 066004 Hebei China

Corrected stress field intensity obtained by averaging the superior limit of intrinsic damage dissipation work in critical domain, which considers thoroughly thermodynamic consistency within irreversible thermodynamic framework, was proposed for predictions of high-cycle fatigue endurance limits. Simultaneously, the effects of mean stress, additional hardening behavior related to non-proportional loading paths and stress gradients on multiaxial high-cycle fatigue are taken into account in the proposed approach. The approach is an extension of the general stress field intensity. For a better comparison, existing multiaxial high-cycle fatigue criteria were employed to predict the endurance limits of different metallic materials subjected to different multiaxial loading paths, and it is shown that present proposal performs better from statistical value of error indexes, which make the proposed approach of corrected stress field intensity and its associated concepts provide a new conception to predict endurance limits of multiaxial high-cycle fatigue with high accuracy.

关键词： Intrinsic damage dissipation work Irreversible thermodynamic framework Corrected stress field intensity Multiaxial high-cycle fatigue Stress gradient

Evolution of the Rust Layers Formed on Carbon and Weathering Steels in Environment Containing Chloride Ions

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Acta Metallurgica Sinica(English Letters) 2016年第11期29卷 1025-1036页

作者： Xin-Liang Gao Yi Han Gui-Qin Fu Miao-Yong Zhu Xing-Zhong Zhang National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University School of Metallurgy Northeastern University

To clarify the correlation between alloy elements and growth pattern of the rust layers, the rusting evolution of the carbon and weathering steels was investigated by using the gold markers method. The corrosion experiments were carried out in a simulated environment containing chloride ions. The results indicate that Ni, Cu, Cr and Mo elements in the weathering steel suppress the rust crystallization and impede the rust layer growth to an internal development, and the suppression function benefits the formation of a protective rust layer. Moreover, c-FeOOH is mainly located in the outer rust layer, while b-FeOOH is mainly located in the inner rust layer, and the distribution of the rust compounds in the rust layer is closely related to the growth pattern of the rust layer.

关键词： Atmospheric corrosion Steel Rust layer SEM Chloride ions

Continuous bending and straightening technology of Q345c slab based on high-temperature creep deformation

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Journal of Iron and Steel research International 2017年第6期24卷 595-600页

作者： Long Guo Xing-zhong Zhang Chang-xi Feng National engineering research center for Equipment and Technology of Cold strip rolling Yanshan University Qinhuangdao 066004 Hebei China

A new continuous bending and straightening casting curve with the aim of full using of high-temperature creep deformation was proposed. The curvature of bending and straightening segment varies as sine law with arc length. The basic arc segment is shortened significantly so that the length of bending and straightening area can be extended and the time of creep behavior can be increased. The distance from so lidifying front in the slab was calculated at 1200 ℃ by finite element method. The maximum strain rate of new casting curve at different locations inside the slab is 6.39 × 10 ^-5 s ^-1 during the bending segment and it tends to be 3.70 × 10 ^-5 s ^-1 in the straightening segment. The minimum creep strain rate is 7.45× 10 ^-5 s ^-1 when the stress is 14 MPa at 1 200 ℃. The strain rate of new casting machine can be less than the mini mum creep strain rate. Thus, there is only creep deformation and no plastic deformation in the bending and straightening process of steel continuous casting. Deformation of slabs depending on creep behavior only comes true. It is helpful for the design of the new casting machine and improvement of old casting machine depending on high temperature creep property.

关键词： Steel continuous castingCreep strain rateStrain rateHigh-temperaturecreep behaviorContinuous bendingContinuous straightening

Effect of annealing on properties of Al/steel composite plates prepared by surface oxidation treatment before cold roll bonding

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Journal of Iron and Steel research International 2023年第4期30卷 749-759页

作者： Lun Fu Yu-fei Zhu Bin Yang Chao Yu Hong Xiao National engineering research center for Equipment and Technology of Cold strip rolling Yanshan UniversityQinhuangdao 066004HebeiChina

Al/steel composite plate has a wide application prospect,but great differences in properties between Al and steel are *** is difficult to obtain high bonding strength by the traditional cold roll bonding ***/steel composite plate was thus prepared by cold roll bonding at a reduction rate of 60%after oxidation treatment on the surface to be composited on the steel *** heat treatment of holding at 400℃ for 1 h and cooling with the furnace was then *** bonding strength,microstructure,and properties of the Al/steel composite plate before and after annealing were analysed and compared through shear test,bending test,tensile test,and *** show that the shear strengths of the interface before and after annealing are 100 and 80 MPa,*** the shear strength of the annealed Al/steel composite plate decreases,the bending and overall tensile properties of the composite plate are improved,showing better mechanical properties.

关键词： Al/steel composite plate Oxidation treatment Annealing treatment Shear strength Cold roll bonding