Hybrid model for BOF oxygen blowing time prediction based on oxygen balance mechanism and deep neural network

The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.

Effect of hypoxia on expression of placental trophoblast cells SATB1 and β-catenin and its correlation with the pathogenesis of preeclampsia

Objective: To study the effect of hypoxia on the expression of placental trophoblast cells SATB1 and β-catenin and its correlation with the pathogenesis of preeclampsia. Methods: Trophoblastic cell lines HRT8/SVneo were cultured, SATB1 and β-catenin expression and cell biological behavior were determined after hypoxia reoxygenation treatment; cell biological behavior and the expression of related genes were determined after the transfection of SATB1 and β-catenin siR NA; preeclampsia placenta and normal placenta tissues were collected and the expression of SATB1 and β-catenin were determined. Results: OD value, cell migration rate, m RNA contents of SATB1 and β-catenin of H/R group were significantly lower than those of Nor group, cell apoptosis rate was higher than that of Nor group and the number of invasive cells was less than that of Nor group; OD value and bcl-2 mRNA content of SATB1-siRNA group were lower than those of NC group; cell apoptosis rate as well as Bax, Caspase-3, caspase-6 and caspase-9 mRNA contents were higher than those of NC group; cell migration rate as well as CTSB, CTSD, MMP2 and MMP9 mRNA contents of β-catenin-siRNA group were lower than those of NC group; the number of invasive cells was less than that of NC group; the expression levels of SATB1 and β-catenin in preeclampsia placenta tissue were significantly lower than those in normal placenta tissue. Conclusions: Hypoxia can inhibit the expression of SATB1 and β-catenin in the pathogenesis of preeclampsia, which can affect the proliferation, apoptosis, migration and invasion of cells.

Basic properties of steel plant dust and technological properties of direct reduction

Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 mm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces （BF） if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the bri-quettes were kept at 1250℃ for 6 min.

Quantitative evaluation of multi-process collaborative operation in steelmaking–continuous casting sections

The quantitative evaluation of multi-process collaborative operation is of great significance for the improvement of production planning and scheduling in steelmaking–continuous casting sections(SCCSs). However, this evaluation is difficult since it relies on an in-depth understanding of the operating mechanism of SCCSs, and few existing methods can be used to conduct the evaluation, due to the lack of full-scale consideration of the multiple factors related to the production operation. In this study, three quantitative models were developed, and the multiprocess collaborative operation level was evaluated through the laminar-flow operation degree, the process matching degree, and the scheduling strategy availability degree. Based on the evaluation models for the laminar-flow operation and process matching levels, this study investigated the production status of two steelmaking plants, plants A and B, based on actual production data. The average laminar-flow operation(process matching) degrees of SCCSs were obtained as 0.638(0.610) and 1.000(0.759) for plants A and B, respectively, for the period of April to July 2019. Then, a scheduling strategy based on the optimization of the furnace-caster coordinating mode was suggested for plant A. Simulation experiments showed higher availability than the greedy-based and manual strategies. After the proposed scheduling strategy was applied,the average process matching degree of the SCCS of plant A increased by 4.6% for the period of September to November 2019. The multi-process collaborative operation level was improved with fewer adjustments and interruptions in casting.

Synthesis of nanostructured Mg_2FeH_6 hydride and hydrogen sorption properties of complex

Reactive mechanical alloying(RMA)was carried out in a planetary ball mill for the synthesis of ternary hydride Mg2FeH6 for hydrogen storage.The formation mechanism of Mg2FeH6 in RMA process and the sorption properties of the products were investigated.The results show that Mg2FeH6 has a yield ratio around 80%,and a grain size below 10 nm in the powder synthesized by milling 3Mg+Fe mixture for 150 h under the hydrogen pressure of 1 MPa.The synthesized powder possesses a high hydrogen capacity and good sorption kinetics,and absorbs 4.42%(mass fraction)of hydrogen within 200 s at 623 K under the hydrogen pressure of 4.0 MPa.In releasing hydrogen at 653 K under 0.1 MPa,it desorbs 4.43%(mass fraction)of hydrogen within 2 000 s.The addition of Ti increases the hydrogen desorption rate of the complex in the initial 120 s of the desorption process.

Hydrogen sorption properties of nanocrystalline Mg_2FeH_6-based complex and catalytic effect of TiO_2

The diversities of hydrogen sorption properties of Mg2FeH6-based complexes with and without TiO2 were investigated. Mg2FeH6-based complexes with and without TiO2 were synthesized respectively by reactive mechanical alloying,and hydrogen sorption properties of the complexes were examined by Sieverts-type apparatus. The results show that the sample without TiO2 releases 4.43 % (mass fraction) hydrogen in 1.5 ks at 653 K under 0.1 MPa H2 pressure and absorbs 90% of the total 4.43 % (mass fraction) hydrogen absorbed in 85 s at 623 K under 4.0 MPa H2 pressure. But for the sample with TiO2 addition under the same condition,it only needs 400 s to release all of the stored hydrogen and 60 s to absorb 90% of the total hydrogen absorbed. The activation energies for desorption process of the samples with and without TiO2 are determined to be 71.2 and 80.3 kJ/(mol.K),respectively. The improvement in hydrogen sorption rate and and reduction in activation energy can be attributed to the addition of TiO2.

Synthesis of ZrN-Si_3N_4 Composite by Carbothermal Reduction and Nitridation of Zircon

Zircon （ ≤44 μm） and carbon black （≤30μm） were used as starting materials and mixed for 24 h using anhydrous ethanol as medium with the mass ratio of 100：40, dried fully at 60 ℃ and then dry mixed for 10 h. Specimens with size of Ф20 mm × 5 mm were pressed under 60 MPa, then dried fully at 120 ℃ , put into a furnace with 1. 0 L ·min^-1 nitrogen gas and fired at 1 400, 1 450, 1 480 and 1 500℃ for 6, 9 and 12 h, respectively. The phase composition and microstructure of the specimens were studied by XRD and SEM, and the carbothermal reduction and nitridation reaction process was thermodynamically analyzed. The results show that using zircon and carbon black as starting materials, ZrN - Si3N4 composite is synthesized by carbothermal reduction and nitridation reaction in nitrogen atmosphere. The composites with different compositions are obtained by controlling the firing temperature and partial pressure of CO gas. The proper firing temperature and holding time to synthesize ZrN - Si3N4 composite are 1 500 ℃ for 12 h.

MiR-200a and miR-200b target PTEN to regulate the endometrial cancer cell growth in vitro

Objective:To study whether miR-200a and miR-200b target PTEN gene expression to regulate the endometrial cancer cell growth in vitro. Methods:Endometrial cancer cells ECC-1 were cultured and transfected with the miR-200a and miR-200b mimics and inhibitors as well as the negative control mimics and inhibitors,and then the cell proliferation activity as well as the expression of PTEN and downstream genes in cells was determined; after transfection of miR-200a and miR-200b mimics as well as PTEN-3'UTR luciferase report gene plasmids,the fluorescence activity of luciferase reporter gene was determined. Results:12 h,24 h and 48 h after transfection,the cell proliferation activity of miR-200a mimics group and miR-200b mimics group were significantly higher than those of NC mimics group while the cell proliferation activity of mi R-200 a inhibitor group and miR-200b inhibitor group were significantly lower than those of NC inhibitor group; 48 h after transfection,PTEN expression in cells and PTEN-3'UTR luciferase reporter gene fluorescence activity of miR-200 a mimics group and miR-200b mimics group were significantly lower than those of NC mimics group while p-PI3K and p-Akt expression were significantly higher than those of NC mimics group; PTEN expression in cells and PTEN-3'UTR luciferase reporter gene fluorescence activity of miR-200 inhibitor group and miR-200b inhibitor group were significantly higher than those of NC inhibitor group while p-PI3K and p-Akt expression were significantly lower than those of NC inhibitor group. Conclusion:miR-200 a and miR-200b can promote the endometrial cancer cell growth in vitro by targeted inhibition of PTEN gene expression.

Ore-proportioning optimization technique with high proportion of Yandi ore in sintering

The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum （SFCA）, and so on, were investigated in detail. Besides, the high temperature behavior and function of sintering were obtained. As a result, the techniques for ore-proportioning in sintering were obtained. The results show that Yandi ore possessing higher assimilation ability, better liquid phase fluidity, lower self-strength of bonding phase, and better forming ability of SFCA, should be mixed with iron ores whose properties are opposite to those of Yandi ore. In the optimization of sintering ore-proportioning, Yandi ore, whose price is relatively low, can be mixed as high as 40wt%.

Application of Artificial Neural Network to Predicting Hardenability of Gear Steel

The prediction of the hardenability and chemical composition of gear steel was studied using artificial neural networks. A software was used to quantitatively forecast the hardenability by its chemical composition or the chemical composition by its hardenability. The prediction result is more precise than that obtained from the traditional method based on the simple mathematical regression model.

Effect of Electromagnetic Stirring on Molten Steel Flow and Solidification in Bloom Mold

The effect of electromagnetic stirring on molten steel flow and heat transfer in a 260 mm× 300 mm bloom mold was investigated by using a method combining both finite element method and finite volume method. The simu lation results related to magnetic fields were consistent with the onsite measured data. The magnetic flux density in creased with increasing the current intensity but decreased with increasing the current frequency. Electromagnetic stirring caused molten steel to flow with rotation on a horizontal section and two sets of recirculation regions with opposite fellow directions in a longitudinal section formed. The maximum tangential velocity increased with increasing the current intensity and frequency. Furthermore, the superheat degree of the molten steel on the outlet cross section of the mold decreased with increasing the current intensity. growth zone of solidified shell in the effective stirring zone. bearing steel, the appropriate values of current intensity and to be 300 A and 3 Hz, respectively. Electromagnetic stirring caused the emergence of a zero For the 260 mm N 300 mm bloom continuous caster of current frequency of electromagnetic stirring were found

Development of Ti–V–Mo Complex Microalloyed Hot-Rolled 900-MPa-Grade High-Strength Steel

A new Ti-V-Mo complex microalloyed hot-rolled high-strength steel sheet was developed by controlling a thermo-mechanical controlled processing （TMCP） schedule, in particular with variants in coiling temperature. The effects of coiling temperature （CT） on various hardening mechanisms and mechanical properties of Ti-V-Mo complex mi- croalloyed high-strength low-alloy steels were investigated. The results revealed that the steels are mainly strengthened by a combined effect of ferrite grain refinement hardening and precipitation hardening. The variation in simulated coiling temperature causes a significant difference in strength, which is mainly attributed to different precipitation hardening increment contributions. When the CT is 600 ℃, the experimental steel has the best mechanical properties： ultimate tensile strength （UTS） 1000 MPa, yield strength （YS） 955 MPa and elongation （EL） 17%. Moreover, about 82 wt% of the total precipitates are nano-sized carbide particles with diameter of 1-10 nm, which is randomly dispersed in the ferrite matrix. The nano-sized carbide particles led to a strong precipitation hardening increment up to 310 MPa.

AlN Precipitates and Microstructure in Non-oriented Electrical Steels Produced by Twin-roll Casting Process

Aluminum nitride （AIN） precipitates and microstructure of 4 wt.% （Si＋AI） non-oriented electrical steel were investigated. The 2.0 mm thick cast strips with three different silicon/aluminum （Si/AI） ratios were produced by twin-roll casting process, then the strips were reheated, warm rolled, cold rolled and annealed. The microstructure and AIN precipitates were characterized using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that with the increase of Si/AI ratio, on the one hand, the casting microstructure changed from columnar grains to equiaxed grains, and the uniformity of annealed microstructure was improved; On the other hand, the number of AIN precipitates in cast strips reduced meanwhile the distribution became dispersed. By the reheat treatment, the size and distribution of the AIN precipitates can be changed. Moreover, the grain size of the annealed strips is in the range of 20-50 #m, at the same time, many AIN precipitates were located at grain boundaries. Therefore, controlling the Si/AI ratio is a simple method to obtain desired microstructure. Then AIN precipitates in non-oriented electrical steel prepared by twin-roll casting process hinder markedly the recrystallized grains growth, A compatible reheat treatment can be an approach worth exploring to control the behavior of AIN precipitates.

Effect of Cooling Rate and Deformation on Microstructures and Critical Phase-Transformation Temperature of Boron-Nickel Added HSLA H-Beams

Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy （HSLA） H-beams cooled at different cooling rate, with different deformation were investigated. Continuous cooling transformation （CCT） diagram of this new type of steel was obtained by using Gleeble 1500 ther- momechanical simulator. Microstructures and hardness, especially micro-hardness of the experimental steel were in- vestigated by optical microscopy （OM）, scanning electron microscope （SEM）, Rockwell and Vickers hardness tests. Phase analysis was also studied by X^ray diffraction （XRD）. The results indicated that with increase of cooling rate, microstructures of continuous cooled specimens gradually transformed from polygonal ferrite and pearlite, grain boundary ferrite and bainite, bainite and martensite to single martensite. The CCT diagram revealed that slow cool- ing was needed to avoid austenite-bainite transformation to ensure toughness of this steel. By plastic deformation of 40%, austenite-ferrite transformation temperature increased by 46℃, due to deformation induced ferrite transfor- mation during continuous cooling, but Rockwell hardness has little change.

Impact Toughness of an NM400 Wear-Resistant Steel

An NM400 wear-resistant steel was hot rolled and then the plates were heat-treated by direct quenching and tempering （DQT） and reheat quenching and tempering （RQT） techniques, respectively. The Charpy impact test was carried out with an instrumented Charpy impact tester. The microstructure and fracture surface were investiga-ted by a combination of optical microscopy, transmission electron microscopy and scanning electron microscopy methods. It was found that the impact toughness of DQT specimen was much higher than that of RQT specimen. The microstructure of both DQT and RQT specimens was characterized by a mixture of tempered lath martensite and lower hainite. The lower bainite in DQT specimen extended into prior austenite grains and the content was higher than that in RQT specimen. The lower bainite in DOT specimen improved the impact toughness by increasing the proportion of large-angle boundaries and relieving the stress concentration at the crack tip. A number of fine and dis-persed carbides in DQT specimen also contributed to the improvement of the impact toughness.

A New Steel Teeming Technology by Using Electromagnetic Induction Heating System in Ladle

In order to overcome the pollution of the tratitional nozzle sand into the molten steel in tundish,a new method is proposed in this paper.In this method,the nozzle sand is substituted with iron-carbon alloy particles which have the same or similar compositions as the liquid steel.During casting processes,iron-carbon alloy forms solidification shell and the sintered layer in the upper nozzle to block the molten steel.When the slide gate is opened,the eletromagnetic induction heating is used to melt them so as to achieve 100%smoothly steel teeming.The electromagnetic induction heating effects were analyzed theoretically in the new slide gate system.Then the new method has been experimentally tested by using self-designed experimental device.The results show that the electromagnetic induction heating can complete the steel teeming within the required time.Furthermore,this steel-teeming technology can further improve the cleanliness of liquid steel.

Effects of Steel Teeming in New Slide Gate System with Electromagnetic Induction

Steel teeming time is a very important parameter in the new slide gate system with electromagnetic induction （called electromagnetic steel teeming system）, and how to shorten this time is a key to realize application of the new system in continuous casting. The effects of power parameters, coil position, nozzle material and other factors on the steel teeming time were investigated by a self-designed electromagnetic steel teeming system in detail. The experimental results show that the relationship between power and steel teeming time is nonlinear. The coil position has great in- fluence on steel teeming time. And the upper nozzle with high permeability can reduce the teeming time. In addition, the steel teeming time becomes minimum when the size of the spherical cast iron particles is 2.0 ram. This research can provide technical references for the industrial application of the new electromagnetic steel teeming system.

Genetic optimization of ladle scheduling in empty-ladle operation stage based on temperature drop control

To optimize ladle scheduling in the empty-ladle operation stage of steel plants,a mathematical scheduling model was established for the empty-ladle operation stage,taking the minimum total waiting time in the empty-ladle operation stage as the optimization goal and setting the equipment assignment uniqueness as the key constraint.An improved genetic algorithm was designed to calculate the mathematical scheduling model.In the operation of the genetic algorithm,the strategy of"ladle temperature drop control"was adopted to solve the problem of equipment conflicts and reduce unreasonable ladle temperature drops to enhance"red-ladle"utilization.Five main production modes operating at 95%capacity in a Chinese steel plant were simulated using the genetic optimization model.The results showed that the genetic optimization model could improve the efficiency of ladle operation and reduce the total waiting time in the empty-ladle operation stage by 868–1147 min.