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Monitoring and diagnosis of complex production process based on free energy of Gaussian–Bernoulli restricted Boltzmann machine

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Journal of Iron and steel Research(International) 2023年第5期30卷 971-984页

作者： Qian-qian Dong Qing-ting Qian Min Li Gang Xu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

Online monitoring and diagnosis of production processes face great challenges due to the nonlinearity and multivariate of complex industrial processes.Traditional process monitoring methods employ kernel function or multilayer neural networks to solve the nonlinear mapping problem of data.However,the above methods increase the model complexity and are not interpretable,leading to difficulties in subsequent fault recognition/diagnosis/location.A process monitoring and diagnosis method based on the free energy of Gaussian-Bernoulli restricted Boltzmann machine(GBRBM-FE)was proposed.Firstly,a GBRBM network was established to make the probability distribution of the reconstructed data as close as possible to the probability distribution of the raw data.On this basis,the weights and biases in GBRBM network were used to construct F statistics,which represents the free energy of the sample.The smaller the energy of the sample is,the more normal the sample is.Therefore,F statistics can be used to monitor the production process.To diagnose fault variables,the F statistic for each sample was decomposed to obtain the Fv statistic for each variable.By analyzing the deviation degree between the corresponding variables of abnormal samples and normal samples,the cause of process abnormalities can be accurately located.The application of converter steelmaking process demonstrates that the proposed method outperforms the traditional methods,in terms of fault monitoring and diagnosis performance.

关键词： Process monitoring Fault diagnosis Gaussian–Bernoulli restricted Boltzmann machine Energy function Free energy Converter steelmaking production process

Characteristics of SEN clogging and adhesive behavior of oxide inclusion during continuous casting of Ti-stabilized ultra-pure ferritic stainless steels

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Journal of Iron and steel Research(International) 2023年第10期30卷 1939-1951页

作者： Xue-feng Bai Yan-hui Sun Hui-bin Wu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China

Submerged entry nozzle(SEN)clogging during continuous casting of Ti-stabilized ultra-pure ferritic stainless(Ti-UPFS)steels was systematically investigated via cross-sectional analysis and acid dissolution treatment.The SEN deposit profile was characterized as occurring in three major layers:(1)an eroded refractory layer;(2)an initial adhesive layer comprised an Al_(2)O_(3)-ZrO_(2) composite sub-layer and a dense Al_(2)O_(3)-based deposit sub-layer;and(3)a porous multiphase deposit layer mainly consisting of MgO·Al_(2)O_(3),CaO-Al_(2)O_(3),and CaO-TiOx.The MgO·Al_(2)O_(3)-rich inclusions did not adhere directly to the eroded refractory but were entrapped during the deposit growth.Results of inclusion characterization in the tundish revealed that the MgO·Al2O3-rich particles present in the tundish served as the primary source of clogging deposits.Furthermore,a novel cavity-induced adhesion model by circular approximation was established to explain the effects of complex inclusion characteristics and refractory material type on adhesion force.A high number of small MgO·Al_(2)O_(3) inclusions were expected to accelerate the buildup of clogging deposits.Improving the modification of MgO·Al_(2)O_(3)-rich inclusions in the size range of 2-4μm by Ca treatment was crucial to minimizing the risk of SEN clogging during the continuous casting of Ti-UPFS steels.

关键词： Ti-stabilized ultra-pure ferritic stainless steel Submerged entry nozzle clogging MgO·Al_(2)O_(3)-rich inclusion Adhesion Continuous casting

Solidification structure simulation and casting process optimization of GCr15 bloom alloy

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China Foundry 2022年第1期19卷 63-74页

作者： Jie Li Hao-tian Wu Yang Liu Yan-hui Sun Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

Based on the solidification heat transfer model and CAFÉmodel,the solidification structure of GCr15 bloom alloy was studied.Using nail shooting and acid etching experiments,the solidification models were verified.The secondary dendrite arm spacing(SDAS)model of GCr15 was obtained by simulation calculation and metallographic observation.With the increase of casting speed,the SDAS,equiaxed crystal ratio(ECR)and average grain size increase.With the rise of superheat,the SDAS increases in the 20-70 mm of thickness and decreases in the 80-160 mm of thickness.The ECR decreases and the average grain size increases with the increase of superheat.With the increase of specific water flow,both the SDAS and ECR decrease.The minimum average grain size is obtained when the specific water flow is 0.20 L·kg^(-1).The central carbon segregation index is reduced from 1.11 to 1.075.

关键词： numerical simulation continuous casting equiaxed crystal ratio secondary dendrite arm spacing carbon segregation

Formation and thermodynamics of CaS-bearing inclusions during Ca treatment in oil casting steels

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International Journal of Minerals,Metallurgy and Materials 2019年第5期26卷 573-587页

作者： Xue-feng Bai Yan-hui Sun Rui-mei Chen Yi-min Zhang Yi-fan Cai Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing

Industrial experiments were carried out to investigate the formation of CaS-bearing inclusion during Ca double modification in oil casting steels using polished cross sections and electrolytic extraction. Immediately after Ca addition, the role of newly generated CaS as an intermediate reaction product, which modified the Al_2O_3 inclusion into a liquid calcium aluminate, was confirmed. The formation of transient CaS was attributed to the high surface segregation of S at the liquid steel-calcium vapor interface, where a simple site coverage model based upon the Langmuir adsorption equation was established. Moreover, a CaS outer layer surrounding the liquid calcium aluminate was attained mainly in the tundish, which was distributed unevenly on the surface of liquid particles according to the three-dimensional mapping results. The surface of a well-modified calcium aluminate with higher CaO activity and Al_2O_3 activity under bulk composition conditions in the tundish acted as a favorable site for the generation of CaS. Additionally, CaS could be precipitated directly onto existing inclusions during solidification of the steel, which led to various morphologies of CaS-bearing inclusions in slabs. Furthermore, the phase transformation of inclusions during solidification was strongly influenced both by the S content and the Ca/S ratio in the tundish via thermodynamics.

关键词： CaS inclusions Ca treatment electrolytic extraction thermodynamics three-dimensional investigations

Tunable fabrication of single-crystalline CsPbI_(3) nanobelts and their application as photodetectors

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 1030-1037页

作者： Tao Yang Ya-peng Zheng Kuo-Chih Chou Xin-mei Hou Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

Lead halide perovskites have received increasing attention recently as a candidate material in various optoelectronic areas because of their high performance as light absorbers.Herein,we report the growth of CsPbI_(3) nanobelts via a solution process.A single-crystalline CsPbI_(3) nanobelt with uniform morphology can be achieved by controlling the amount of PbI_(2).A single-crystalline CsPbI_(3) nanobelt possesses a mean width,length,and thickness of 100 nm,5μm,and 20 nm,respectively.In this work,photodetectors(PDs)based on individual CsPbI_(3) nanobelts are constructed and found to perform well with an external quantum efficiency and responsivity of 2.39×10^(5)% and 770 A/W,respectively.The PDs also show a high detectivity of up to 3.12×10^(12) Jones,which is at par with that of Si PDs.The PDs developed in this work exhibit great promise in various optoelectronic nanodevices.

关键词： photodetector cesium lead triiodide perovskite nanobelt detectivity

Effects of chromium on the microstructure and hot ductility of Nb-microalloyed steel

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 1011-1021页

作者： Yang Liu Yan-hui Sun Hao-tian Wu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

It is well-known that the surface quality of the niobium microalloy profiled billet directly affects the comprehensive mechanical properties of the H-beam.The effects of chromium on theγ/αphase transformation and high-temperature mechanical properties of Nb-microalloyed steel were studied by Gleeble tensile and high-temperature in-situ observation experiments.Results indicated that the starting temperature of the γ→αphase transformation decreases with increasing Cr content.The hot ductility of Nb-microalloyed steel is improved by adding 0.12wt% Cr.Chromium atoms inhibit the diffusion of carbon atoms,which reduces the thickness of grain boundary ferrite.The number fractions of high-angle grain boundaries increase with increasing chromium content.In particular,the proportion is up to 48.7% when the Cr content is 0.12wt%.The high-angle grain boundaries hinder the crack propagation and improve the ductility of Nb-microalloyed steel.

关键词： phase transformation hot ductility chromium high-angle grain boundaries grain boundary ferrite

Effect of Sn doping concentration on the oxidation of Al-containing MAX phase(Ti_(3)AlC_(2))combining simulation with experiment

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Fundamental Research 2022年第1期2卷 114-122页

作者： Chunyu Guo Enhui Wang Yunsong Liu Yapeng Zheng Tao Yang Xinmei Hou Beijing Advanced innovation center for Materials Genome Engineering Collaborative Innovation Center of Steel TechnologyUniversity of Science and Technology BeijingBeijing 100083China

Sn doping is usually adopted to prepare Ti_(3)AlC_(2)in mass production because it can reduce the synthesis temperature while increasing the phase purity.However,excessive Sn doping usually deteriorates the oxidation resistance of Ti_(3)AlC_(2).Therefore,an appropriate Sn doping concentration is a vital issue.In this work,the effect of Sn doping concentration on the oxidation behavior of Ti_(3)AlC_(2)was systematically investigated by combining theoretical calculations and experimental methods.Density function theory calculations suggest that the oxygen adsorption mechanisms for the(001)surface of Ti_(3)AlC_(2)with and without Sn doping are similar,and Ti-O bonds are always preferentially formed.The molecular dynamics simulation further indicates that Al atoms have a faster diffusion rate during the oxidation process.Therefore,a continuous Al_(2)O_(3)layer can form rapidly at high temperature.Nevertheless,when the Sn doping concentration exceeds 10 mol%,the continuity of the Al_(2)O_(3)layer is destroyed,thereby impairing the oxidation resistance of Ti_(3)AlC_(2).Furthermore,oxidation experiments verify the above results.The oxidation mechanisms of Ti3AlC2 with different Sn doping concentrations are also proposed.

关键词： MAX phase Sn doping Density function theory Molecular dynamics Oxidation resistance

Research Progress of Refractory High Entropy Alloys:A Review

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Chinese Journal of Mechanical Engineering 2022年第6期35卷 1-22页

作者： Xiaochang Xie Neng Li Wei Liu Shuai Huang Xiaoyong He Qiuying Yu Huaping Xiong Enhui Wang Xinmei Hou Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Beijing Institute of Aeronautical Materials Beijing 100095China

Owing to superior comprehensive performance than conventional superalloys at high temperature,refractory high entropy alloy(RHEA)is becoming a promising candidate for the next generation high-temperature material.Herein,contemporary aspects of corresponding development of RHEAs are reviewed to discuss various factors affecting the organization structure and service performance.It mainly covers alloying system and strengthening mechanism,the preparation method,plastic deformation and the related mechanism,as well as microstructure control by heat treatment.Firstly,the alloy systems and strengthening mechanism are introduced.This is followed by different preparation methods and the comparison of strengths and shortcomings based on different RHEAs.Then,hot deformation behavior and plastic deformation under different loadings are analyzed.Based on this,the influence of heat treatment on microstructures prior to and after the deformation is further summarized.Finally,some important research areas to be carried out in future are pointed out.This review will give a deep understanding of the effects of different factors on the service performance and provide scientific guide in designing RHEAs with improved performance.

关键词： Refractory high entropy alloy Preparation method Strengthening Plastic deformation Heat treatment

Reverse-transformation austenite structure control with micro/nanometer size

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International Journal of Minerals,Metallurgy and Materials 2017年第5期24卷 530-537页

作者： Hui-bin Wu Gang Niu Feng-juan Wu Di Tang Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beijing Engineering technology Research center of Special steel for Traffic and Energy

To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure, the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. The samples were first cold-rolled, and then samples deformed to different extents were annealed at different temperatures. The microstructure evolutions were analyzed by optical microscopy, scanning electron microscopy (SEM), magnetic measurements, and X-ray diffraction (XRD); the mechanical properties are also determined by tensile tests. The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel. The micro/nanometric microstructure was obtained after reversion annealing at 820-870A degrees C for 60 s. Nearly 100% reversed austenite was obtained in samples annealed at 850A degrees C, where grains with a diameter ae 500 nm accounted for 30% and those with a diameter > 0.5 mu m accounted for 70%. The micro/nanometer-grain steel exhibited not only a high strength level (approximately 959 MPa) but also a desirable elongation of approximately 45%.

关键词： austenitic stainless steel structure control martensite reverse transformation grain refinement