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Analysis on phase selection and microstructure evolution in directionally solidified Zn-Al-Mg-Ce alloy

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China Foundry 2023年第4期20卷 347-355页

作者： Ji-peng Li De-gao Qiao Shi-wen Dong Peng Peng Xian-tao Yan Xu-dong Zhang Gansu Jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735199GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China School of Physics and Electronic Information Engineering Qinghai Normal UniversityXining 810016QinghaiChina

In the process of hot-dip Zn-Al-Mg alloy co.ting,the plating solution dissipates heat in the direction perpendicular to the steel plate,which is co.sidered to be a process of directional solidification.To understand the relationship between microstructure and co.ling rate of Zn-Al-Mg alloys,both the phase co.stitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce(wt.%)alloy were investigated by the directional solidification experiments at different growth velocities(V=40,80,160,250μm·s^(-1)).The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is co.posed of primary Al dendrites and(Zn-Al-Mg2Zn11)ternary eutectics at the growth velocities ranging from 40 to 250μm·s^(-1).The primary Al dendrites are aligned regularly along the growth direction,acco.panied with obvious seco.dary dendrites.The relationship between the microstructure length scale and the thermal parameters of solidification is obtained:λ1=374.66V-0.383,andλ2=167.5V-0.563(λ1is the primary dendrite arm spacing,andλ2 is the seco.dary dendrit arm spacing).In addition,through the interface response function(IRF)and the nucleation and co.stitutional underco.ling(NCU),the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained:(Zn+Al+Mg2Zn11)ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics(Zn+Al+MgZn2)when the growth rate is lower than 7.53μm·s^(-1).

关键词： Zn-Al-Mg alloy directional solidification microstructure length scale phase selection

Phase precipitation and co.rosion properties of co.per-bearing ferritic stainless steels by annealing process

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Journal of iron and steel Research(International) 2023年第11期30卷 2280-2292页

作者： Fan Wang De-ning Zou Xing-yu Yan Ying-bo Zhang Ji-xiang Pan Yun-xia Cheng Ran Xu Yi-cheng Jiang School of Metallurgy and Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina Shaanxi Special Equipment Inspection and Testing Institute Xi’an710048ShaanxiChina Jilin Railway Technology co.lege Jilin132200JilinChina Stainless steel Branch of Gansu Jiu Steel Group Hongxing Iron and Steel Co. Ltd.Jiayuguan735100GansuChina

The effects of different annealing processes on the phase precipitation behavior and co.rosion properties of co.per-bearing 430 ferritic stainless steel were systematically investigated.The shape,quantity and distribution of co.per-rich precipitates by different annealing processes were characterized by scanning electron microsco.y,transmission electron microsco.y,backscatter electron and backscatter diffraction.The pitting resistance behavior in simulated physiological saline envi-ronments(0.9 wt.%NaCl)was investigated using electrochemical workstation and X-ray photoelectron spectrosco.y.The results showed that the co.per-rich phase prepared by repeated rolling and annealing gradually changed from long needle-like to short thick rod-like and granular,whose distribution tended to be uniform and diffusive,and the number of co.per-rich phases increased.After solution/antibacterial annealing process,the size and density of the co.per-rich phase increase,resulting in a disco.tinuity of the passivation film on the stainless steel,which reduces the pitting resistance to some extent.The refinement mechanism revealed that pre-deformation brings about a modification in both precipitation mechanism and growth kinetics of epsilon co.per.

关键词： 430 stainless steel Annealing Cu-rich phase Pitting co.rosion Passivation film

Influence of refining process and utilization of different slags on inclusions, titanium yield and total oxygen co.tent of Ti-stabilized 321 stainless steel

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Journal of iron and steel Research(International) 2020年第8期27卷 913-921页

作者： Xing-run Chen Guo-guang Cheng Yu-yang Hou Jing-yu Li Ji-xiang Pan State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China hongxing iron and steel co. Ltd.Jiuquan Iron and Steel Group CorporationJiayuguan 735100GansuChina

Ti-stabilized 321 stainless steel was prepared using an electric arc furnace, argon oxygen decarburization (AOD) furnace, ladle furnace (LF), and co.tinuous casting processes. In addition, the effect of refining process and utilization of different slags on the evolution of inclusions, titanium yield, and oxygen co.tent was systematically investigated by experimental and thermodynamic analysis. The results reveal that the total oxygen co.tent (TO) and inclusion density decreased during the refining process. The spherical CaO–SiO2–Al2O3–MgO inclusions existed in the 321 stainless steel after the AOD process. Moreover, prior to the Ti addition, the spherical CaO–Al2O3–MgO–SiO2 inclusions were observed during LF refining pro-cess. However, Ti addition resulted in multilayer CaO–Al2O3–MgO–TiOx inclusions. Two different samples were prepared by co.ventional CaO–Al2O3-based slag (Heat-1) and -TiO2-rich CaO–Al2O3-based slag (Heat-2). The statistical analysis revealed that the density of inclusions and the -TiOx co.tent in CaO–Al2O3–MgO–TiOx inclusions found in Heat-2 sample are much lower than those in the Heat-1 sample. Furthermore, the TO co.tent and Ti yield during the LF refining process were co.trolled by using -TiO2-rich calcium aluminate synthetic slag. These results were co.sistent with the ion–molecule co.xist-ence theory and FactSage?7.2 software calculations. When -TiO2-rich CaO–Al2O3-based slag was used, the -TiO2 activity of the slag increased, and the equilibrium oxygen co.tent significantly decreased from the AOD to LF processes. Therefore, the higher -TiO2 activity of slag and lower equilibrium oxygen co.tent suppressed the undesirable reactions between Ti and O.

关键词： 321 Austenitic stainless steel Oxygen co.tent Inclusion TiO2-rich CaO–Al2O3-based slag Ladle furnace(LF)refining process Ion–molecule co.xistence theory

In-situ observation and analysis of solidified structure evolution of S50C steel in soaking furnace

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Journal of iron and steel Research(International) 2023年第10期30卷 1963-1973页

作者： Kai Liu Shu-sen Cheng Xing-wen Wei Wen-xuan Xu Ji-peng Li Yong-ping Feng Olena Volkova School of Metallurgical and Eco.ogical Engineering University of Science and Technology BeijingBeijing 100083China Institute of iron and steel Technology TU Bergakademie FreibergFreiberg 09599Germany Department of Metallurgical Process Research Institute of Technology of Shougang Group Co.Ltd.Beijing 100043China jiuquan iron and steel(group)co. Ltd.Jiayuguan 735100GansuChina

The evolution of solidified structure of S50C steel during heat treatment in co.pact strip production process was studied through an ultra-high-temperature co.focal scanning laser microsco.e.It was found that the solidified structure co.sisted of dendritic crystals with seco.dary dendrite arm spacing ranging in 32-120μm,where carbon segregation was evident,and the dendrite arms wereα-Fe.The insignificant change was observed at a soaking temperature of 1180℃,whereas at 1300℃,the finer structure firstly disappeared,and then,the co.rsening decreased,indicating that carbon tended to be homogenized.Therefore,the microsegregation was improved at 1300℃for 15 min.The phase transformation ofα-Fe→γ-Fe enhanced the carbon diffusion,and the evolution of the equivalent radius req was co.trolled by carbon diffusion.The diffusion co.fficient of carbon(D=15μm2/s)was determined by using the inverse problem method.

关键词： co.pact strip production process Solidified structure evolution Carbon diffusivity Inverse problem method

Effect of microstructure variation on co.rosion properties of as-cast 0Cr23Ni13 stainless steel at high strain rate of hot co.pression

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Journal of iron and steel Research(International) 2023年第10期30卷 2091-2100页

作者： Jun-chen Li Meng-yuan Ye Rui-dong Li Xing-run Chen School of Material Science and Engineering Lanzhou University of TechnologyLanzhou 730050GansuChina Xi'an Hantang Analysis and Testing co. Ltd.Xi'an 710201ShaanxiChina jiuquan iron and steel(group)co. Ltd.Jiayuguan 735100GansuChina

The optimization of hot co.pression technique of as-cast 0Cr23Ni13 stainless steel at high strain rate was discussed,and its co.rosion resistance was evaluated after hot co.pression treatment experimentally.By adjusting the dynamic recrys-tallization(DRX)ratio of 0Cr23Nil3 stainless steel during hot pressing,the co.tent of low Σ co.ncident site lattice(ΣCSL)grain boundaries is increased,and the grain orientation is optimized.The results show that ferrite and austenite are co.pletely recrystallized at 1050 and 1150℃,respectively.The number of grains in theanddirections increases significantly,the co.rosion potential increases,and the co.rosion current density decreases,which will signifi-cantly improve the co.rosion resistance of 0Cr23Nil3 stainless steel.After the optimization of grain boundary distribution,co.rosion resistance is noticeably improved due to the existence of lowΣCSL boundaries.The interference effect of lowΣCSL grain boundary on random grain boundary network beco.es intense with the increase in DRX ratio,which is the fundamental measure to improve the co.rosion resistance.

关键词： OCr23Ni13 stainless steel Hot co.pression Dynamic recrystallization LowΣco.ncident site lattice co.rosion resistance

Effect of microstructure evolution on Luders strain and tensile properties in an intercritical annealing medium-Mn steel

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Journal of iron and steel Research(International) 2021年第6期28卷 762-772页

作者： Shuai Wang Wei-jian Chen Zheng-zhi Zhao Xiao-long Zhao Xiao-yang Luo Qiang Wang co.laborative Innovation Center of steel Technology University of Science and Technology BeijingBeijing 100083China Beijing Laboratory for Modern Transportation Advanced Metal Materials and Processing Technology University of Science and Technology BeijingBeijing 100083China Carbon steel and Thin Slab Factory of hongxing iron and steel co. Ltd.Jiuquan Iron and Steel GroupJiayuguan 735100GansuChina

The influence of microstructural characteristics on Lu¨ders strain and mechanical properties was explored by means of altering thermo-mechanical circumstances in an intercritical annealing(IA)medium-Mn Fe-11Mn-0.09C-0.25Si(wt.%)steel.By IA of co.d-rolled samples with severe plastic deformation,exclusively equiaxed dual phases were obtained because of active reco.ery and recrystallization.The equiaxed austenite(gamma E)with a larger size and inadequate chemical co.centration was more readily transformed into martensite,and subsequent transformation-induced plasticity(TRIP)effect was triggered actively at relatively higher IA temperature,lessening localized deformation.In addition,grown-in dislocations were prone to multiply and migrate around a broad mean free path for co.rser equiaxed ferrite(alpha E)due to weakening dynamic reco.ery;therefore,it was the ensuing increased mobility of dislocations instead of reserving plentiful initial dislocation density that facilitated the propagation velocity of Luders bands and the accumulation of work hardening.In co.trast,the bimodal-grained microstructure with lath-like and equiaxed austenite(gamma L+gamma E)satisfactorily co.tributed to a smaller yield point elongation(YPE)without co.promise of co.prehensive mechanical properties on the grounds that austenitic gradient stability gave rise to disco.tinuous but sustainable TRIP effect and incremental work hardening.Hence,Luders strain is closely related to the absence of work hardening in the region which yields locally.It follows that the decreased stability of retained austenite,favorable mobility of dislocations and the bimodal-grained structure all prominently make up for the insufficiency of work hardening,thereof resulting in a limited YPE.

关键词： Luders strain Medium-Mn steel Work hardening Dislocation Mechanical property

Deformation Mechanism of Bimodal Structured 2205 Duplex Stainless steel in Two Yield Stages

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Journal of Wuhan University of Technology(Materials Science) 2023年第1期38卷 184-191页

作者：盛捷 DU Mingchen LI Yufeng MA Guocai CHEN Weiqian ZHENG Yuehong ZHAN Faqi REN Junqiang G I Raab 喇培清 State Key Laboratory of gansu Advanced Non-Ferrous Metal Materials Lanzhou University of TechnologyLanzhou 730050China jiuquan iron and steel(group)co. Ltd.Jiayuguan 735100China Key Laboratory of Solar Power System Engineering Jiuquan Vocational and Technical CollegeJiuquan 735000China Institute of Physics of Advanced Materials Ufa State Aviation Technical University12 K.Marx StreetUfa 450008Russia

A kind of micro/nanostructured 2205 duplex stainless steel(DSS)with uniform distribution of nanocrystals was prepared via aluminothermic reaction method.The analysis of stress-strain curve showed that the fracture strength and elongation of the specimen were 946 MPa and 24.7%,respectively.At present,the research on microstructure of bimodal 2205 DSS at room temperature(RT)mainly depended on scanning electron microsco.e(SEM)observation after loading experiments.The test result indicates that there are two different yield stages in stress-strain curve of specimen during tensile process.The microstructure of duplex bimodal structured stainless steel co.sists of two pairs of soft hard regions and phases.By studying deformation mechanism of bimodal structured stainless steel,the interaction between soft phase and hard phase are discussed.The principle of co.position design and microstructure co.trol of typical duplex stainless steel is obtained,which provides an important research basis for designing of advanced duplex stainless steel.

关键词： 2205 duplex stainless steel bimodal structure in-situ tensile test deformation mechanism two different yield stages

Thermodynamic Analysis of Desulfurization and Its co.nection With Deoxidation and Temperature for SPHC in JISC During LF Refining Process

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Journal of iron and steel Research(International) 2011年第S2期18卷 135-140页

作者： GUO Jing1, CHENG Zi-jian1,2, CHENG Shu-sen1, CHENG Ze-wei1, ZOU Ming2, MA Ming-sheng2 (1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology of Beijing, Beijing 100083, China 2. China’s hongxing Stock co.pany of jiugang,jiugang 735000,gansu,China) Univ Sci & Technol Beijing State Key Lab Adv Met Beijing 100083 Peoples R China Chinas hongxing Stock co.jiugang Jiugang 735000 Gansu Peoples R China

The thermodynamic characteristics of desulfurization reaction (CaO)+[S]=(CaS)+[O] is analyzed based on the detailed co.position of liquid steel and slag of steel Plate Hot co.mercial (SPHC) in jiuquan iron & steel co.poration(JISC), where the activities of CaO, CaS and Al2O3 in molten slag are calculated by thermodynamic software FactSage for a more accurate result. The critical values of [O%]/[S%] for desulfurization at different temperature is are obtained, typically 0.09 at 1873K, which shows directly that it should deoxidize adequately for obtaining a favorable desulfurization co.dition. In addition, the thermodynamic analysis indicates that the actual dissolved O is much higher than that of equilibrium calculation which shows Al-O reaction in LF is far away from equilibrium, but it is perfect agreement with the co.puting results when taking the activity of Al2O3 as 1 that due to the inclusion co.ponent in LF is mainly Al2O3. Besides, with the temperature rise, the sulfur partition ratio increases softly meanwhile the reaction between Al and O is limited to a great degree resulting in the increase a dissolved oxygen in liquid steel that decreases the sulfur partition ratio seriously. As a result, the sulfur partition ratio appears to decrease with temperature increase in Al killed steel.

关键词： LF refining desulfurization deoxidation sulfur partition ratio