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Effects of two silicone resin coatings on performance of FeSiAl magnetic powder cores

Journal of Iron and Steel Research(International) 2024年第5期31卷 1279-1288页

作者： jia-qi Liu Zheng-qu Zhu Pu Wang Yi-fan Li Jing Pang jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China Qingdao Yunlu Advanced Materials Technology Co. Ltd.Qingdao266232ShandongChina

Two silicon resins with excellent thermal stability,JH1123 and JH7102,are used as the insulated agents and binders for the gas-atomized FeSiAl powder,and corresponding magnetic powder cores(MPCs)are fabricated.The insulation capability and application prospects of the two silicon resins are evaluated by comparing the magnetic properties of the coated powder and MPCs.The scanning electron microscopy,energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy results show that uniform insulation layers are both formed on the powder surfaces.JH1123 has stronger binding ability,and the JH1123-coated powder exhibits severe agglomeration,with d50(average particle size)approximately twice that of the JH7102-coated powder.Both as-prepared MPCs exhibit outstanding soft magnetic properties.Wherein,the permeability of FeSiAl@JH1123 is up to 74.0,which is 35.5%higher than that of FeSiAl@JH7102 because JH1123 can further improve the density of the MPCs.As for FeSiAl@JH7102,it has better direct current bias and lower core loss of 716.9 mW cm^(−3) at 20 mT and 1000 kHz due to its lower coercivity and greater anti-magnetic saturation ability.A comprehensive comparison shows that FeSiAl@JH1123 is suitable for medium and high frequency applications,while FeSiAl@JH7102 is more suitable for high frequency applications.This indicates that the use of JH1123 and JH7102 silicon resins for binding and insulated coating not only simplifies the preparation process of MPCs,but also enables the controlled production of MPCs for different applications.

关键词： FeSiAl Insulated coating Magnetic powder core Permeability Core loss

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Propagation form of internal cracks induced by continuous casting soft reduction and control strategy for internal quality

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Journal of Iron and Steel Research(International) 2024年第3期31卷 622-633页

作者： Pu Wang Liang Chen Qun-wei Tang Wei-tao Li Shao-xiang Li jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Weifang Special Steel Group Co..Ltd. Weifang 262400ShandongChina School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China

The propagation form of internal cracks induced by continuous casting soft reduction and the control strategy for enhancing the internal quality of 45 steel through industrial trials and a three-dimensional flow-heat transfer-solidification coupling model were investigated.The results showed that the internal cracks induced by soft reduction exhibited a characteristic of being"coarse in the middle and fine at both ends",and displayed an elliptical arc distribution on the loose side of the strand cross section.The cracks originated within the brittle temperature range and propagated inward to the liquid impenetrable temperature and outward to the zero ductility temperature or below.The control strategy for enhancing the internal quality of the 45 steel strand through soft reduction is to adjust the casting speed or the reduction zone appropriately,ensuring that the central solid fraction of the reduction zone falls within the range of 0.33-0.99.At this point,a reasonable reduction amount is allocated to eliminate the center shrinkage cavities and center segregation,even if it results in minor reduction-induced cracks.

关键词： Continuous casting Soft reduction Crack propagation Internal quality Control strategy

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Effect of channel diameter on magneto-thermal conversion ratio and consistency of each strand in a multi-strand induction heating tundish

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1199-1210页

作者： Pu Wang Hong Xiao Xi-qing Chen Hai-yan Tang jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Magnetoelectric Research Institute Hunan Zhongke Electric Co.Ltd.Yueyang 414000HunanChina

The electromagnetic,flow,heat transfer and inclusions motion model of the channel-type induction heating(IH)tundish was established,and the effect of the channel diameter on the metallurgical behavior of the tundish was studied.The results show that the magnetic field in the channel of the IH tundish tends to concentrate on the surface layer and the side near the coil.As the channel diameter is increased from 100 to 180 mm,the maximum value of magnetic flux density in the channel decreases by 0.125 T,and the maximum value of electromagnetic force decreases by 11.83×10^(5) N m^(-3);however,the off-center distance of magnetic field increases by 9.4 mm,and the Joule heat in the channel decreases by 1004 kW,which leads to the reduction in temperature rising rate of the tundish from 1.41 to 0.59 K min^(-1).When the channel diameter is 100,140 and 180 mm,the maximum velocity at the channel exit before heating is 0.59,0.29 and 0.18 m s^(-1),and after heating for 1800 s,it is 1.52,1.12 and 0.92 m s^(-1),respectively.In addition,the total inclusions escape ratio after heating for 1800 s with a channel diameter of 140 mm can be reduced by 12.39% compared to that before heating,and the maximum difference of escape ratios for each strand is only 4.51% and 5.32% before heating and after heating for 1800 s,respectively.Compared with the channel diameters of 100 and 180 mm,the channel diameter of 140 mm is more favorable to improve the metallurgical effect of the IH tundish.

关键词： Induction heating tundish Channel diameter Joule heat Temperature rising rate Inclusion escape ratio

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Simulation and experiment investigations on fabrication of Fe-based amorphous powders by a novel atomization process equipped with assisted gas nozzles

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1142-1155页

作者： jia-qi Liu Yan-nan Dong Pu Wang Huan Zhao Jing Pang Xiao-yu Li jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China Qingdao Yunlu Advanced Materials Technology Co. Ltd.Qingdao 266232ShandongChina

Based on computational fluid dynamics method,the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied,and then a discrete phase model was established and combined with industrial trials to study the effect of a new type of assisted gas nozzles(AGNs)on powder size distribution and amorphous powder yield.The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle;however,it will decrease the aspiration pressure,and the optimal atomization pressure is 2.0 MPa.Compared with this,after the application of AGNs with the inlet velocity of 200 m s^(-1),assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s^(-1) and the maximum cooling rate is increased from 1.9×10^(4) to 2.3×10^(4) K s^(-1).The predicted particle behavior is demonstrated by the industrial trails,that is,after the application of AGNs,the median diameter of powders d50 is decreased from 28.42 to 25.56 lm,the sphericity is increased from 0.874 to 0.927,the fraction of amorphous powders is increased from 90.4% to 99.4%,and only the coercivity is increased slightly due to the accumulation of internal stress.It is illustrated that the AGNs can improve the yield of fine amorphous powders,which is beneficial to providing high-performance raw powders for additive manufacturing technology.

关键词： Computational fluid dynamics Atomization Assisted gas nozzle Discrete phase model Amorphous powder

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Effect of Actual Cooling Rate of Ladle Stream on Persistent Metallurgical Performance of a Given Tundish

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Journal of Iron and Steel Research(International) 2014年第10期21卷 915-922页

作者： Hai-bo SUN jia-quan zhang State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing

To evaluate the effect of actual cooling rate of liquid steel in the ladle on the metallurgical performances of a tundish, a transient and coupled computational model was developed to reveal the flow fields, temperature fields, residence time distribution of the molten steel and the inclusion removal efficiency in a typical single-strand tundish with given geometry and process parameters. The results showed that, with the decrease of the ladle stream cooling rate, the temperature difference of bulk flow at the outlet of tundish over a normal casting period decreased from 11.3 to 2.6 K, and the dead volume fraction of the tundish decreased from 17.58% to 14. 35%, while the inclusion removal efficiency was increased especially for the inclusions with the diameter less than 50 μm, whose removal ratio could be increased by 20.62%. When the cooling rate was less than 0.3 K · min-1 , however, the variation rates of the three evaluation criterions above declined significantly, which suggested that a critical value existed for the effect of the cooling rate of ladle stream on the tundish performances. The establishment of the critical ladle stream cooling rate should be very important to achieve persistent metallurgical properties of tundish over the whole casting stage, together with the reasonable ladle insulation design.

关键词： critical cooling rate ladle stream tundish performance fluid flow thermal buoyancy force, residencetime distribution

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Control of mould level fluctuation through the modification of steel composition

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International Journal of Minerals,Metallurgy and Materials 2013年第2期20卷 138-145页

作者： Yang Li Xiao-huan zhang Peng Lan jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing

Periodic mould level fluctuation （MLF） during slab casting is a bottleneck for upgrading the surface quality and casting speed especially for hypoperitectic （HP） or ultralow carbon steels. The uneven growth of the initially solidified shell is verified to be one of the important inducements to MLF due to related unsteady bulging in the secondary cooling zone. It is shown that the solidification mode of steels and the contraction behavior can be modified through chemical composition optimization within given composition limits, For high strength low alloy （HSLA） steels, the actual peritectic points calculated by Thermo-Calc software may change remarkably with the slight variations of alloying element contents. Accordingly, the narrow limit of chemical composition of HP steels through optimization is proven to be one of the effective factors to control the popular MLF phenomenon during slab casting.

关键词： low carbon steel continuous casting solidification composition optimization

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Inclusion evolution in 50CrVA spring steel by optimization of refining slag

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Journal of Iron and Steel Research(International) 2017年第9期24卷 879-887页

作者： Hai-yan Tang Yong Wang Guang-hui Wu Peng Lan jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China

In order to control the CaO-Al;O;-SiO;-MgO system inclusions in 50 CrVA spring steel in a lower melting temperature region,high temperature equilibrium experiments between steel and slag were performed in the laboratory,under the conditions of the initial slag basicity within 3-7and the content of Al;O;between 18-35mass%,to investigate the formation and evolution of this type of inclusion.The results indicate that the total oxygen content in the steel decreases with the increase of slag basicity and the decrease of Al;O;content in slags,and CaO-Al;O;-SiO2-MgO inclusions tend to deviate from the low melting point region with the increase of Al;O;content in slags.The most favorable composition for the refining slag is composed of 51-56mass% CaO,9-13mass% SiO;,20-25mass% Al;O;and 6mass% MgO.In this case,the inclusions in 50 CrVA spring steel are mostly in the low melting point regions,in which their plasticities are expected to improve during steel rolling.The MgO-based inclusions were observed in the steel matrix and the formation mechanism was theoretically and schematically revealed.It is also found that adding around 11mass% of MgO into the refining slags is beneficial to reducing the refractory corrosion.Further work should be carried out focusing on the evolution rates of MgO-based inclusions.

关键词： 50CrVA spring steel Refining slag optimization Inclusion evolution MgO-based inclusion Formation mechanism

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Thermo-elasto-visco-plastic finite element analysis on formation and propagation of off-corner subsurface cracks in bloom continuous casting

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Journal of Iron and Steel Research(International) 2017年第11期24卷 1159-1168页

作者： Yu-jun Li Huan Li Peng Lan Hai-yan Tang jia-quan zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China

The formation and propagation of the popular off-corner subsurface cracks in bloom continuous casting were investigated through thermo-mechanical analysis using three coupled thermo-mechanical models. A two-dimensional thermo-elasto-visco-plastic finite element model was developed to predict the mould gap evolution, temperature profiles and deformation behavior of the solidified shell in the mould region. Then, a three-dimensional model was adopted to calculate the shell growth, tempera- ture history and the development of stresses and strains of the shell in the following secondary cooling zones. Finally, another three-dimensional model was used to analyze the stress distributions in the straightening region, The results showed that the off-corner cracks in the shell originated from the mould owing to the tensile strain developed in the crack sensitive regions of the solidification front, and they could be driven deeper by the possible severe surface temperature rebound and the extensive tensile stress in the secondary cooling zone, especially upon the straightening operation of the bloom casting. It is revealed that more homogenous shell temperature and thickness can be obtained through optimization of mould corner radius, casting speed and secondary cooling scheme, which help to decrease stress and strain concentration and therefore prevent the initiation of the cracks.

关键词： Thermo elasto-visco-plastic finite element model Off-corner subsurface crack Mould corner radius Temperature rebound Straightening operation Bloom continuous casting

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Rheological Behaviors of Polymers with Nanoparticles Tethered at Each End

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Chinese Journal of Polymer Science 2024年第3期42卷 400-406,I0009页

作者： Song-Qi zhang Wen-Qing Wang jia-Ping Lin Li-quan Wang Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials of Ministry of EducationSchool of Materials Science and EngineeringEast China University of Science and TechnologyShanghai 200237China

The polymer with nanoparticles tethered at each end is a unique model for unraveling the effect of chain ends on the polymer dynamics. We investigated the rheological behavior of this kind of polymer by using nonequilibrium molecular dynamics simulation. The effect of polymer lengths and nanoparticle radii on the complex moduli and viscosity was examined. The dependence of complex moduli on the frequency becomes less pronounced as the polymer is short or the nanoparticle is large. The shear thinning behavior was revealed for these systems, and the scaling exponent of complex viscosity with respect to the frequency was found to change from-1/2 to-3/4 as the polymer shortens or the nanoparticle enlarges. The rheological behavior was further explained by analyzing the mean square distance of nanoparticles. The simulation results were compared with the existing experimental finding, showing an agreement. The work provides information for understanding the chain end effect on polymer rheology.

关键词： Polymer rheology Modulus Viscosity Molecular dynamics

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Application and progress of artificial intelligence technology in the segmentation of hyperreflective foci in OCT images for ophthalmic disease research

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International Journal of Ophthalmology(English edition) 2024年第6期17卷 1138-1143页

作者： jia-Ning Ying Hu Li Yan-Yan zhang Wen-Die Li quan-Yong Yi Ningbo Eye Hospital Wenzhou Medical UniversityNingbo 315042Zhejiang ProvinceChina Health Science Center Ningbo UniversityNingbo 315211Zhejiang ProvinceChina

With the advancement of retinal imaging,hyperreflective foci(HRF)on optical coherence tomography(OCT)images have gained significant attention as potential biological biomarkers for retinal neuroinflammation.However,these biomarkers,represented by HRF,present pose challenges in terms of localization,quantification,and require substantial time and resources.In recent years,the progress and utilization of artificial intelligence(AI)have provided powerful tools for the analysis of biological markers.AI technology enables use machine learning(ML),deep learning(DL)and other technologies to precise characterization of changes in biological biomarkers during disease progression and facilitates quantitative assessments.Based on ophthalmic images,AI has significant implications for early screening,diagnostic grading,treatment efficacy evaluation,treatment recommendations,and prognosis development in common ophthalmic diseases.Moreover,it will help reduce the reliance of the healthcare system on human labor,which has the potential to simplify and expedite clinical trials,enhance the reliability and professionalism of disease management,and improve the prediction of adverse events.This article offers a comprehensive review of the application of AI in combination with HRF on OCT images in ophthalmic diseases including age-related macular degeneration(AMD),diabetic macular edema(DME),retinal vein occlusion(RVO)and other retinal diseases and presents prospects for their utilization.

关键词： artificial intelligence deep learning hyperreflective foci image analysis

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