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Effects of the width and thickness of slabs on broadening in continuous casting

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 723-728页

作者： jian-xun fu Jing-she Li Hui Zhang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China National Engineering Research Center of Continuous Casting Technology Central Iron and Steel Research Institute Beijing 100081 China

A 3D viscoelastic-plastic thermal-mechanical coupled finite element model was built on the basis of the secondary development of the commercial software ***. Numerical simulations were performed to study slab broadening in the secondary cooling zone. The effects of slab width and thickness on slab broadening were considered. The obtained results reveal that the width broadening is noticeable, and the ratio of ultimate broadening slightly increases with the increase of slab width. This agrees well with the measured data in practice. There is no obvious increase in ultimate broadening when the thickness of slabs increases.

关键词： continuous casting slabs broadening finite element method

Thermomechanical analysis of triangular zone cracks in vertical continuous casting slabs based on viscoelastic-plastic model

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Journal of Iron and Steel Research International 2018年第8期25卷 813-820页

作者： Juan Cheng Yan-xin Wu Yang Wang jian-xun fu Materials Genome Institute and State Key Laboratory of Advanced Special Steel and School of Materials Science andEngineering Shanghai University Shanghai 200444 China

The triangular zone cracks in 2101 duplex stainless steel produced by the vertical continuous caster have troubled company A for a long time. To simulate the temperature and thermal stress distributions in the solidification process of 2101 duplex stainless steel produced by the vertical continuous caster, a two-dimensional viscoelastic-plastic thermomechanically coupled finite element model was established by the secondary development of the commercial nonlinear finite element analysis software MSC Marc. The results show that the thermal stress on the surface reaches a maximum at the exit of the mould, and the highest thermal stresses at the centre of the wide face and the narrow face are 75 and 115 MPa, respectively. Meanwhile, the internal temperature of slab is still higher than the solidus temperature, resulting in no thermal stress. The slab shows different high-temperature strengths and suffers from different stresses at different positions; thus, the risk of cracking also varies. At a location of 6-8 m from the meniscus, the temperature of the triangular zone is 1270-1360℃ and the corresponding permissible high-temperature strength is about 10-30 MPa, while the thermal stress at this time is 60 MPa, which is higher than the high-temperature strength. As a result, triangular zone cracks form easily.

关键词： Vertical continuous caster Triangular zone crack Thermomechanical coupling Viscoelastic-plastic model -Finite element analysis

Analysis of precipitation behavior of MnS in sulfur-bearing steel system with finite-difference segregation model

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Journal of Iron and Steel Research International 2018年第8期25卷 803-812页

作者： De-lin Hu Hui Liu jian-bo Xie Juan Cheng jian Li jian-xun fu State Key Laboratory of Advanced Special Steel and Shanghai Key Laboratory of Advanced Ferrometallurgy and School of Materials Science and Engineering Shanghai University Shanghai 200444 China

To further reveal the influence of micro-segregation on the precipitation behavior of MnS in sulfur-bearing steel system, a coupled model of micro-segregation and MnS precipitation was established by the finite-difference method based on various calculation domains and the solid diffusion degrees, and a new controlled diffusion equation with more stable convergence was also used. 49MnVS3 and 1215 steels were used to analyze the influence of calculation domain, segregation model and S content on the precipitation behavior of MnS. The calculation results were verified by a high- temperature confocal laser scanning microscope （HT-CLSM）. The results show that the domain has little effect on the precipitation temperature, precipitation solid fraction and precipitation amount of MnS, but affects the precipitation location and segregation of the solutes. For low- and medium-sulfur steels, the temperatures calculated by the diffusion control growth （DCG） model and the Lever model were nearly identical, whereas the temperature calculated by the Scheil model was lower. However, for high-sulfur steels, the precipitation temperatures calculated by three segregation models were nearly same. The precipitation solid fraction is more reasonable to describe the precipitation behavior of MnS. The precipitation behavior of MnS, observed by the HT-CLSM, matches well with that in the DCG model.

关键词： MnS precipitation Micro-segregation Mathematical model Solidification In situ observation

A method for observing tridimensional morphology of sulfide inclusions by non-aqueous solution electrolytic etching

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Journal of Iron and Steel Research International 2019年第3期26卷 275-284页

作者： Dong Zhang Ping Shen jian-bo Xie Jin-min An Zong-ze Huang jian-xun fu State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrous Metallurgy School of Materials Science and Engineering Shanghai University Shanghai 200072 China State Key Laboratory of Development and Application Technology of Automotive Steel (Baosteel Group) Shanghai 20190 China

Three-dimensional investigation of sulfides is required in order to improve the mechanical properties of steel by controlling the sulfides in the steel.A method including its principles and device is introduced for the investigation of threedimensional morphology of *** method is suitable for gear steel,free cutting steel,non-quenched steel,tempered steel(ws≥0.02 wt.%),*** influences of current density,time,and temperature on the exposure degree of sulfide inclusions were investigated by using 16MnCrS5 *** best parameters of electrolytic etching of sulfur steel,as found by experimentation,are as follows:current density,37.5-52.5 mA/cm2;time,30-35 min;and temperature,—10 to 0℃.Under these conditions,the three-dimensional morphology of sulfide inclusions in sulfur-bearing steel can be exposed effectively.

关键词： Sulfide Non-aqueous electrolyte Electrolytic etching Three-dimensional morphology

Application of tellurium in free-cutting steels

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Journal of Iron and Steel Research International 2018年第8期25卷 787-795页

作者： Ping Shen Qian-kun Yang Dong Zhang Yan-xin Wu jian-xun fu State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrous Metallurgy School of Materials Science and Engineering Shanghai UniversityShanghai 200444 China Institute of Material Science and Engineering National Taiwan University Taipei 10617 Taiwan China

Te is widely used in iron and steel industry. After adding a certain amount of Te in the steel, many physical and chemical properties can be improved. As a free-cutting element, a small amount of Te can significantly improve the machinability of steel. The existing form of Te in the steel, the modification law of MnS inclusion by Te and the influence rule and mechanism of Te on the machinability of steel are summarized and expounded in detail, providing a reference for further study and development of Te-containing free-cutting steels.

关键词： Tellurium - Inclusion Sulfide modification Free-cutting steel

Analysis on composition and inclusions of ballpoint pen tip steel

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 420-428页

作者： Qian-kun Yang Ping Shen Dong Zhang Yan-xin Wu jian-xun fu State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrometallurgy School of Materials Science and Engineering Shanghai University

Ballpoint pen tip steel, a super free-cutting stainless steel, exhibits excellent corrosion resistance and good machining properties. In this study, inductively coupled plasma spectroscopy, metallographic microscopy, and scanning electron microscopy were used to determine the elemental contents in five ballpoint pen tips and their components, morphologies, and inclusion distributions. The results showed that the steels were all S–Pb–Te super free-cutting ferritic stainless steel. The free-cutting phases in the steels were mainly Mn S, Pb, and small amounts of Pb Te. Mn S inclusions were in the form of chain distributions, and the aspect ratio of each size inclusion in the chain was small. The stress concentration effect could substantially reduce the cutting force when the material was machined. Some of the Pb was distributed evenly in the steel matrix as fine particles（1–2 μm）, and the rest of the Pb was distributed at the middle or at both ends of the Mn S inclusions. The Pb plays a role in lubrication and melting embrittlement, which substantially increases the cutting performance. Pb Te was also usually distributed in the middle and at both ends of the Mn S inclusions, and Te could convert the sulfides into spindles, thereby improving the cutting performance of the steel.

关键词： ballpoint pen tip free-cutting stainless steel inclusions lead tellurium

Influence of on-line tempering parameters on microstructure of medium-carbon steel

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Journal of Iron and Steel Research International 2017年第1期24卷 59-66页

作者： Hua Zhang Yan-xin Wu jian-xun fu Jie Xu Qi-jie Zhai State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200072China

A new process involving ultra-fast cooling（UFC）and on-line tempering（OLT）was proposed to displace austempering process,which usually implements in a salt/lead bath and brings out serious pollution in the industrial *** optimization of the new process,involving the evolution of the microstructure of medium-carbon steel during various cooling paths,was *** results show that the cooling path affected the final microstructure in terms of the fraction of pearlite,grain size and distribution of cementite in *** the cooling rate or decreasing the OLT temperature contributes to restraining the transformation from austenite to ferrite,and simultaneously retains more austenite for the transformation of *** is also noted that bainite was observed in the microstructure at the cooling rate of 45℃/s and the OLT temperature of 500℃.Through either increasing the cooling rate or decreasing the OLT temperature,the distribution of cementite in pearlite is more dispersed and grain is *** the possibility of industrial applications into account,the optimal process of cooling at 45℃/s followed by OLT at 600℃ after hot rolling was determined,which achieves a microstructure containing nearly full pearlite with an average grain size of approximately 7μm and a homogeneously dispersed distribution of cementite in pearlite.

关键词： Medium-carbon steel Ultra-fast cooling On-line tempering Phase transformation kinetics

Dilatometric Analysis of Irreversible Volume Change during Phase Transformation in Pure Iron

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Journal of Iron and Steel Research International 2016年第8期23卷 828-833页

作者： Ren-jie ZHAO jian-xun fu Yu-yuan ZHU Ye-jin YANG Yan-xin WU State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory Advanced Ferrometallurgy &School of Materials Science and Engineering Shanghai University

One assumption underlying the conventional dilatometric analysis based on the lever rule is that the volume of the specimen changes isotropically during phase transformation,which conflicts with the irreversible length change shown in actual *** contribution of this irreversible effect to the dilation data of pure iron upon heating and cooling was respectively quantified via conversion equations based on lattice parameters.A model considering the elastic strain and creep deformation was established for both the interpretation of the irreversible volume change and the discrepancy between the results measured by a dilatometer and a micrometer.

关键词： irreversible Transformation micrometer interpretation specimen lever length creep ferrite shrinkage

Application of fractal theory to study morphology of manganese sulfide inclusion in resulfurized free-cutting steels

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Journal of Iron and Steel Research International 2023年第1期30卷 137-149页

作者： Xiang-yu Xu Zhi-qi Zeng Qian-ren Tian Chen-wei Cao Ping Shen jian-xun fu Center for Advanced Solidification Technology(CAST) State Key Laboratory of Advanced Special SteelSchool of Materials Science and EngineeringShanghai UniversityShanghai 200444China Baosight Software Co. Ltd.Information Service HeadquartersShanghai 201203China

The morphology and distribution of manganese sulfide(MnS)inclusions have a significant influence on the comprehensive performance,which is an important research field for resulfurized *** on the experiments of non-aqueous electrolyte and scanning electron microscope observation,the fractal theory was employed to study the three-dimensional morphologies of MnS *** results showed that the edge fractal dimension of MnS inclusions was between 1.59 and *** addition,similar morphology of MnS inclusions had a close fractal *** MnS edge fractal dimension is highly positively correlated with the morphological *** multifractal spectrums of MnS inclusions on two-dimensional plane of as-cast and as-rolled resulfurized free-cutting steels were *** large-size MnS inclusions belong to large probability subset,while the small-size MnS inclusions belong to small probability *** multifractal spectrum can truly and effectively reflect the difference and non-uniformity of distribution of MnS inclusions on 2D *** the premise of similar content of MnS,with the refinement of MnS inclusions,the multifractal spectrum width and the multifractal spectrum symmetry parameter were *** multifractal spectrum provides a new method for studying the second phase in materials.

关键词： MnS inclusion Morphology Fractal dimension Multifractal Resulfurized steel