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Hot tearing susceptibility of Fe-20.96Cr-2.13Ni-0.15N-4.76Mn-0.01Mo duplex stainless steel

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Journal of Iron and Steel Research International 2017年第4期24卷 421-425页

作者： Zhi-qiang Wei Xiang-ru Chen hong-gang zhong Qi-jie Zhai gang Wang State Key Laboratory of Advanced Special Steel&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering Shanghai UniversityShanghai 200072China

The hot tearing susceptibility of a Fe-20.96Cr-2.13Ni-0.15N-4.76Mn-0.01 Mo duplex stainless steel was investigated using method of constrained solidification shrinkage in one *** apparatus for realtime measuring the contraction stress and temperature during solidification was developed,which can achieve the in-situ observation of melting and solidification and avoid the large temperature gradient of casting under the condition of *** results show that the contraction stress increases significantly when the core temperature of casting reaches the liquidus *** contraction stress is released when the core temperature of casting reaches 1456°*** this temperature,the hot tearing susceptibility of duplex stainless steel is the *** decreasing the core temperature to 1363°C,the slope of contraction stress increases,which is related to the ferrite-to-austenite transformation.

关键词： Duplex stainless steel Hot tearing Solidification Contraction stress Core temperature

Improving ingot homogeneity by modified hot-top pulsed magneto-oscillation

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Journal of Iron and Steel Research International 2022年第12期29卷 1939-1950页

作者： Fan Zhang hong-gang zhong Yu-qian Yang Ming-xu Pan Ren-xing Li Qi-jie Zhai Center for Advanced Solidification Technology Shanghai UniversityShanghai 200444China Daye Special Steel Co. Ltd.Huangshi 214429HubeiChina

Heavy ingots,especially the ingot of more than 10 t,often contain detrimental heterogeneous defects,such as macrosegregation,shrinkage pipes,and ***-top pulsed magneto-oscillation(HPMO)can refine the solidified structure of ingot and improve their ***,it may exacerbate the positive segregation at the upper part of the ingot ***,a round table HPMO riser with a feeding part was designed,and the microstructure and macrosegregation of Al–Si alloy ingots solidified with and without HPMO were *** simulation and experimental results indicated that round table HPMO riser could enable fine and uniform solidified structures in the whole ingot body;in the meantime,feeding part allowed the melt with enriched solute to gather in the upper part of the riser until the last solidification stage of *** provides an effective approach for obtaining highly homogenized ingots.

关键词： Homogeneity Hot-top pulsed magneto-oscillation Heavy ingot Macrosegregation Simulation

Relationship between secondary dendrite arm spacing and local solidification time of 30Cr2Ni4MoV alloy at slow cooling rates

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Journal of Iron and Steel Research International 2018年第8期25卷 821-829页

作者： Jing Zhao hong-gang zhong Ke Han Ren-xing Li Zhi-shuai Xu Qi-jie Zhai Department of Mechanical and Electrical Engineering Tangshan University Tangshan 063000 Hebei China State Key Laboratory of Advanced Special Steel Shanghai University Shanghai 200444 China National High Magnetic Field Laboratory Florida State University Tallahassee 32310 USA

Solidification process of 231 t 30Cr2Ni4MoV ingot manufactured by slow cooling process was studied using experimental and numerical simulations, which tackled the problems of high cost and long period in large ingot studying. Based on the numerical results of large ingot, five characteristic locations under different temperature gradients and cooling rates chosen from the large ingot were simulated. The experiments were performed under the same temperature conditions as in numerical simulations with specialized instrument. The influences of temperature gradient in the solid-liquid interface and solidification rate on the size and morphology of solidification structure were analyzed at cooling rate ranging from 10-3 to 10 2℃ s-1. Solidification macrostructure and microstructure showed that no columnar dendrite was found in any specimen. The grain size and secondary dendrite arm spacing decreased at larger cooling rate, and the relationship between secondary dendrite arm spacing and local solidification time or cooling rate was determined.

关键词： Slow cooling rate - Simulation Secondary dendrite arm spacing Solidification time Grain size

Improving the Solidified Structure by Optimization of Coil Configuration in Pulsed Magneto-Oscillation

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Acta Metallurgica Sinica(English Letters) 2018年第12期31卷 1334-1344页

作者： Jing Zhao Ji-Hao Yu Ke Han hong-gang zhong Ren-Xing Li Qi-Jie Zhai Department of Mechanical and Electrical Engineering Tangshan University State Key Laboratory of Advanced Special Steel Shanghai University National High Magnetic Field Laboratory Florida State University

Using both numerical and experimental methods, we studied the effect of coil configuration of pulsed magneto-oscillation（PMO） on distribution of electromagnetic field, flow field and solidification structure with the same pulse currentparameters in A1 ingots. We designed and constructed three types of coils： surface pulsed magneto-oscillation, hot-toppulsed magneto-oscillation （HPMO） and combined pulsed magneto-oscillation （CPMO）. PMO treatment refined thesolidification structure in all the ingots. The configuration of the PMO, however, introduced differences in magnetic fieldintensity, electromagnetic force, Joule heat, flow field, equiaxed grain zone, grain size and growth direction of columnargrains. The largest equiaxed grain zone was found in CPMO treated ingot, and the smallest grain size was found in bothHPM0 and CPMO treated ingots. Numerical simulation indicated that difference in electromagnetic field and flow fieldresulted in differences in solidification structure. HPMO is more advantageous over others for large ingot production.

关键词： Pulsed magneto-oscillation Coil configuration Electromagnetic field Flow field Solidification structure Optimization

nfluences of superheat and cooling intensity on macrostructure and macrosegregation of duplex stainless steel studied by thermal simulation

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Journal of Iron and Steel Research International 2021年第9期28卷 1125-1132页

作者： hong-gang zhong Xiang-ru Chen Yan-jie Liu Zhi-qiang Wei Hai-feng Yu Qi-jie Zhai Center for Advanced Solidification Technology Shanghai UniversityShanghai200444China Shanghai Institute of Materials Genome Shanghai200444China Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai200431China

The influences of superheat and cooling intensity on macrostructure and macrosegregation of one new kind duplex stainless steel(DSS)were *** simulation equipment was applied to prepare samples,which could reproduce the industrial processes of DSS manufactured by a vertical continuous slab *** and macrosegregation were analyzed using the digital single lens reflex and laser-induced breakdown spectroscope(LIBSOPA-200),*** percentage of both chill zone and center equiaxed zone increases with the superheat decreasing,while that of the columnar zone *** is only equiaxed grain existing as the superheat is 10 and 20℃.The lower the superheat is,the coarser the gain size *** cooling intensity in mold could remarkably decrease the chill zone length and refine the grains in chill zone and center equiaxed *** influences of cooling intensity on macrosegregation are greater than those of *** macrosegregation of Si,Mn and Cr is slightly dependent on superheat,while that of Cu,Mo and Ni changes greatly with superheat increasing.

关键词： Continuous casting Solidification Thermal simulation Duplex stainless steel Macrosegregation

Effect of cooling rate and forced convection on as-cast structure of 2205 duplex stainless steel

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China Foundry 2015年第1期12卷 32-38页

作者： Cheng Zhang hong-gang zhong Cong-sen Wu Jie Ni Qi-jie Zhai Shanghai Key Laboratory of Modern Metallurgy & Materials Processing Shanghai University

To forecast the as-cast structure and ferrite-austenite phase ratio of 2205 duplex stainless steel(DSS), the effects of cooling rate and forced convection were observed in a high-vacuum resistance furnace in which the forced convection was created by the rotation of the crucible. The as-cast structure of all 2205 DSS samples is full equiaxed grains, and the microstructure consists of a great amount of desirable intra-granular austenite inside the continuous ferrite grain matrix, besides Widmanstatten austenite and grain boundary austenite. The ferrite grain size decreases gradually with the increase in the cooling rates(20 to 60 oC·min-1) or the forced convection, while the ferrite grains of the samples solidified with a strong convection are barely changed when the cooling rate is below 50 oC·min-1. Moreover, a small grain size is beneficial for the austenite formation but the influence is not very obvious under the cooling rates in the range of 5 to 50 oC·min-1. Compared with grain size, the cooling rate has a greater influence on the final ferrite content. A model based on the experimental results is established to predict the ferrite content, which could be approximated by δ(%) = 20.5·exp(c/80.0) + 0.34 d +34.1, where cis the cooling rate in oC·min-1 and d is the grain size in mm. By using this model, the dependence of the final ferrite content on cooling rate and grain size is well described.

关键词： duplex stainless steel cooling rate grain size forced convection ferrite content

Effects of pulse magneto-oscillation on GCr15 bearing steel continuous casting billet

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Journal of Iron and Steel Research International 2022年第1期29卷 144-150页

作者： Yan-jie Liu Guo-dong Xu Ying-chun Wang hong-gang zhong Li-juan Li Biao Wang Qi-jie Zhai Materials Genome Institute Shanghai UniversityShanghai 200444China Center for Advanced Solidification Technology Shanghai UniversityShanghai 200444China Research Institute China Baowu Steel Group CorporationShanghai 200431China Steel Plant China Baowu Steel Group CorporationShanghai 200431China

Pulse magneto-oscillation(PMO)added during solidification could affect the solidification structure and macrosegregation.A modified thermal simulation equipment was applied to prepare GCr15 bearing steel continuous casting billets with different PMO peak ***,metallographic analysis,component analysis and numerical simulation were adopted to study the influence of PMO peak current and its *** sample with 150 K_(I)A PMO peak current treatment has little difference with the samples without PMO treatment on solidification structure and *** the peak currents are 250 and 350 K_(I)A,the columnar zone increases and macrosegregation *** 450 K_(I)A peak current is selected,the equiaxed grain ratio is enlarged,and the dendritic grains are refined,and the macrosegregation of C,Cr,Si and Mn is decreased *** analyzing,different convections induced by PMO with various peak currents are the key factor to change the solidification structure and macrosegregation.

关键词： Bearing steel Numerical simulation Thermal simulation Pulse magneto-oscillation

Effect of cooling rate on microstructure and inclusion in non-quenched and tempered steel during horizontal directional solidification

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Journal of Iron and Steel Research International 2019年第9期26卷 973-982页

作者： Hui Liu Zong-ze Huang Da-jiang Yu De-lin Hu hong-gang zhong Qi-jie Zhai Jian-xun Fu State Key Laboratory of Advanced Special Steel School of Materials Science and EngineeringShanghai UniversityShanghai 200072China State Key Laboratory of Development and Application Technology of Automotive Steels (Baosteel Group) Shanghai 201900China

In order to investigate the relationship between microstructure and MnS inclusion in non-quenched and tempered steel, and cooling rate during horizontal directional solidification, 49MnVS steel was used to conduct the experiments with a selfdesigned device. The mathematical effect of cooling rate on dendritic arm spacing and mean diameter of MnS particles (dMnS) were determined by using linear regression method. The results show that the length of dendrite from solid–liquid interface to end-solidification decreased with increasing the withdrawal velocity (#). dMnS has a similar value in the area of the steady directional solidification;the value of dMnS was 4.1, 3.6, 3.3, 2.8 and 2.3 lm at withdrawal velocity of 50, 75, 100, 150 and 200 lm/s, respectively. dMnS increased with reducing # or RC (interface cooling rate). MnS precipitated in the gaps between dendrites and was influenced by secondary dendritic arm spacing. Besides, a new concept of the ‘Precipitation Unit Space’(PUS) was proposed and the relationships between dMnS, VPUS (volume of PUS) and RC were obtained.

关键词： Horizontal directional solidification Dendrite MnS Inclusion Cooling rate

Influence of electromagnetic parameters on solidification structure of pure AI in the case of identical power

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Journal of Iron and Steel Research International 2018年第8期25卷 854-861页

作者： Yong-yong Gong Shu-min Cheng Yu-yi zhong Xiang Wang Yun-hu Zhang Qi-jie Zhai hong-gang zhong Zhi-shuai Xu Rong Yue Ning Pei College of Science Shanghai University Shanghai 200444China Shanghai Key Laboratory of Modern Metallurgy and Materials Processing Shanghai University Shanghai 200444China School of Materials Science and Engineering Shanghai University Shanghai 200444 China Materials Genome Institute Shanghai UniversityShanghai 200444 China

Pulsed magneto-oscillation （PMO） as a new electromagnetic technology to generate the grain refinement in metals and alloys was significantly developed in recent years. The influence of electromagnetic parameters on the grain size reduction in pure AI was investigated under the application of PMO with a constant inputting power. The experimental results show that the grain refinement degree could be improved with the increase in the current intensity in the case of the identical power. Moreover, through analysing the electromagnetic force and resistance force applied on the nucleus, a criterion of the nucleus detached from the mould wall was constructed. Based on the criterion, the detachment of nuclei with finer radius could cause better effect of the grain refinement, when applying a higher current peak. The movement of the detached grains was considered by analysing the influence of electromagnetic force and forced flow.

关键词： Grain refinement Pure Al Solidification Pulsed magneto-oscillation Identical power