Microstructural Characterization of Welded Joint in Duplex Stainless Steel by Laser Continuous Heat Treatment

Microstructural characterization in fusion zone of the laser continuous heat treatment welded joint was in vestigated. The results showed that the martensite-like microstructure is the face centered cubic （FCC） crystal structure so that it can be identified as the secondary austenite. The dislocation is observed inside and outside the seconda ry austenite, whereas inclusion is not found in the vicinity of the secondary austenite. In the fusion zone, there is a kind of carbide precipitate which is identified as M23 C6 by the means of transmission electron microscope （TEM）. The carbide precipitate is a representative mode of transformation, which can be generated by the eutectoid reaction. Furthermore, the formation mechanisms of the secondary austenite and chromium carbide are analyzed.     

Preparation and Fluorescence Properties of TiO2 ：Eu Nano-Materials

A series of europium-doped titanium dioxide (TiO2) fluorescent nano-materials prepared by sol-gel method is presented. The phase structure and crystalline sizes of TiO2:Eu, which is doped with different europium content and then heat-treated at different temperature, were investigated by XRD ,TG, DTA and TEM. The results show that europium could be introduced into TiO2 under high temperature and it can suppress the structural phase transition from anatase to rutile and the crystal growth of TiO2 in TiO2:Eu nano-materials. The fluorescence spectra were examined by fluorescence spectrophotometer, and the results show that the fluorescence intensity is the strongest when europium content is 2.68% (molefraction) and the heat-treated temperature is 700℃. From the measurement results of the fluorescence lifetimes, it can be seen that the fluorescence lifetime could be prolonged when europium is incorporated in TiO2.     

Microstructure Evolution of Cu-6%Ag Alloys by Modified Unidirectional Solidification Under a Horizontal Static Magnetic Field

The microstructure evolution of Cu dendrites in Cu-6%Ag alloys by modified unidirectional solidification under a static magnetic field has been investigated experimentally and quantitatively.The results show that the proeutectic Cu dendrites are finer when they are closer to the water-cooling copper mould and the unidirectional effect is more obvious,which is attributed to the higher solidification velocity.The quantitative analysis of the microstructure indicates that with increasing external magnetic flux density,the primary arms of the proeutectic Cu dendrites are refined and along a given direction.The analysis indicates that it is both the thermoelectromagnetic convection effect by the external magnetic field and the branch effect of the dendrites.     

Improvement in Production Yield of Hot-rolled Coil by Controlling Process Cobbles

The yield is dependent upon many factors,such as cobbles,total scrap generation,crop loss and scale loss. It appears that the huge quantity of scale is mainly responsible for the yield loss.However,by the correlation study, it reveals that the number of cobbles is the major contributor to the yield loss.The innovation lies in changing the fo-cus of attacking the real problem by analysing the operating data which was not surfaced earlier.The focus shifted from the furnace to the mill and the cobbles studied through the years deeply.All the analysis proved to be helpful for the future prevention of the similar kind of failure.The internal target of bringing down the number of cobbles per month in single digit was taken.This also helped in improving the maintenance practice and reducing the amount of delays significantly.The yield was improved by 0.9 3%.     

Artificial Neural Network Modeling of Microstructure During CMn and HSLA Plate Rolling

An artificial neural network (ANN) model for predicting transformed microstructure in conventional rolling process and thermomechanical controlled process (TMCP) is proposed. The model uses austenite grain size and retained strain, which can be calculated by using microstructure evolution models, together with a measured cooling rate and chemical compositions as inputs and the ferrite grain size and ferrite fraction as outputs. The predicted results show that the model can predict the transformed microstructure which is in good agreement with the measured one, and it is better than the empirical equations. Also, the effect of the alloying elements on transformed products has been analyzed by using the model. The tendency is the same as that in the reported articles. The model can be used further for the optimization of processing parameters, microstructure and properties in TMCP.     

Research on the heat treatment of tool steel 5Cr15MoV

Tempered tool steel 5Cr15MoV was normalized at different temperatures followed by air-cooling.It is found that the hardness increases with the increment of a normalizing temperature from 950℃ to 1 150℃,and it then decreases with the temperature getting higher.The Thermo-calc calculation reveales that the mole fraction of carbides decreases when the normalizing temperature increases,which indicates that more carbon dissolved in the matrix enhances the hardness of the steel.However,the existence of retained austenite causes hardness reduction when the normalizing temperature is over 1 150℃.The salt spray test shows that the steel possesses poor corrosion resistance when it is normalized at a temperature above 1 100℃.The precipitation of the carbides in the cooling process creates a number of chromium-depleted zones,making the steel vulnerable to corrosives.In the present work,an appropriate normalizing temperature is suggested.     

Design of Two-Phase Inductor Circuit for the Floating-Zone Crystal Growth

The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency(RF)induction heating.In order to maintain a convex solidification interface,which is required for the growth of single crystals,we have developed a novel two-phase inductor comprising a secondary coil,which is short-circuited through capacitor and resistor.The former is adjusted to have resonance in the secondary circuit,which results in a 90 degrees phase lag of the secondary current relative to the primary one.However,it is not always possible to tune the secondary circuit into the resonance as it turns out to be incompatible with the operation of contemporary self-tuning RF-generators.We show that the resonance frequency is unstable unless the resistance of the secondary circuit is made high enough.Analytical results are confirmed by both numerical simulation of the circuit system using the Simulink and measurements on the floating-zone crystal growth facility equipped with a two-phase inductor.     

Gas Ionizationon During Carbothermic Reduction in Microwave Field and Its Effect

 Ionization of gas on carbothermic reduction of metal oxides containing coal by microwave heating is studied in the paper. The result of using the conventional heating method to conduct the carbothermic reduction of metal oxides containing coal is obviously weaker than that of the microwave heating in the term of the reduction time, temperature, atom mole ratio of carbon and oxygen. After studied on the cause, it is believed that gas is ionized in carbothermic reduction of solid-solid phrase between metal oxides and coals, which accelerates progress of carbon gasification and significantly improves kinetic conditions of carbothermic reduction.     

Discussion on coke passivation technology

This paper summarized the coke passivation technology which was carried out by major domestic steel companies and research institutions.The paper briefly discussed the different knowledge on coke reactivity between different periods.The reaction in a blast furnace is extremely complex and it is a black box.As the level of awareness of different periods is various,the understanding is opposite. Furthermore,this paper also declared that the effects of temperature and CO_2 concentration of the reaction of c...     

Investigation on Dephosphorization of Stainless Steel

In the scale of ironmaking and steelmaking, the dephosphorization can be divided into four classes. The first level which is known very well by metallurgists is the dephosphorization for carbon steels and low alloy steels. The second level is that included in the pretreatment process of hot metal. It differs from the first level as it must consider how to treat the selective oxidation of ［P］ and ［C］. Furthermore, The contradictory of dephosphorization and desulphurization has to be harmonized. The third level is that for high alloy steels and the fourth is that for ferroalloys. In these cases, two technical ways either oxidizing dephosphorization or reducing dephosphorization can be selected. Whether which one is chosen, the key problem is to lower down phosphorous content efficiently meanwhile to keep the concentration of Cr and/or Mn almost lossless. 　　The cheapest raw materials for the production of high alloy steel are the returning scrap of that steel. Raising the proportion of the returning scraps in the total amount of raw materials is a very important measure to decrease the production cost. In order to avoid an obvious oxidation of Cr, Mn and so on during that melting process it is impossible to adopt the oxidational dephosphorization procedures which is generally carried out in the production of low alloy steel. In this case, after returning several times the phosphorous content in the scraps is accumulated. And then it gradually approaches to the level specified in the standard of the steel. Finally, it will become a waste. It was estimated that the market demand on high alloy steels as stainless steels would rapidly grow. So the scraps containing low phosphorous is urgently needed in a great deal. 　　On the other hand, the standards of some high alloy steels, which are designated for extremely severe environment only, allow a very low phosphorous content. For example, it is claimed that W［P］<0.015 %—0.020 % if the stainless steel products will contact with urea or nitric acid. If the resistance to corrosive fatigue and welding crack is highlighted the phosphorous content should be decreased to less than (100—50)×10－4 %. And Koros P J et al estimated that dephosphorous to 14×10－4 % will be wanted［1］. 　　So far no technology for dephosphorization of stainless steels can be widely adopted in industrial scale. This will be one of the major research projects in the coming century. This paper devotes to a discussion on the strategy of oxidational dephosphorization and the improvement of the reductional dephosphorization.     

Luminescent properties of YVO4·xTa2O5:Eu3+

The samples of YVO4·xTa2O5:Eu3+(x=0.45,0.35,0.25,0.15,0.05)were synthesized by the conventional solid state reaction.The structure of the prepared sample was checked by the X-ray diffraction.XRD measurements at room temperature were confirmed that the prepared YVO4·xTa2O5:Eu3+ consisted of two phases。One phase was YVO4,which is tetragonal according with the JCPDS-Card(17-0341);the other phase was YTaO4,which is according with the JCPDS-Card(72-2018).The spectrum property of the sample was studied under the VUV.The effects of Ta doped on the luminescent properties of sample were investigated and it was found that some Ta doped could highlight the absorption of matrix in VUV region.The emission spectrum was dominated by the red peaks at 613 and 619 nm due to the electric dipole transition 5D0→7F2 of Eu3+.It indicated that Eu3+ occupied a site lacking inversion symmetry.There was one band peaked at 155 nm in the excitation spectrum of the sample,it could be assigned to the absorption of the host.     

Characteristics and Mechanism of Reduction and Smelting-separation Process of Copper Slag

The characteristics and mechanism of the reduction and smelting-separation process of the copper slag were studied by investigating the variation rule of metallization ratio,yield as well as carbon content of iron nuggets.The formation of molten slag is necessary for slag-iron separation,and iron is in half-molten state during smelting-separation process,the carbon content of which is about 1.25%.Carburization occurs through direct contact between carbon and iron in essence,no matter in solid or molten state.The carburization rate is slow below 1 200 ℃,which is inhibited by the existence of slag.Residual FeO in molten slag tends to form fayalite with SiO2 in the copper slag,which is the root cause for the low melting temperature of copper slag.The addition of CaO improves the reducibility of the copper slag,but Al2O3 addition has no obvious effect.The melting temperature of slag affects the carburization extent in solid state,while the content of FeO in molten slag affects that in molten state,both of which co-determine the carbon content in iron nuggets.     

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

The thermodynamic characteristics of desulfurization reaction (CaO)+[S]=(CaS)+[O] is analyzed based on the detailed composition of liquid steel and slag of Steel Plate Hot Commercial (SPHC) in Jiuquan Iron & Steel Corporation(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 condition. 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 computing results when taking the activity of Al2O3 as 1 that due to the inclusion component 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.     

Finite Element Analysis of 100 t Hot Metal Ladle in Process of Tipping

 Hot-metal ladle is an important part in continuous casting production line and its stress distribution has direct influence on its life. In the process of design and calibration of the large sized hot-metal ladle, it’s of great significance to determine the stress distribution of each part of the ladle for safely and reliably running the device. Based on 100t hot-metal ladle which is designed by Baotou Iron &; Steel Group, a simulation of stress field was made by finite element software ANSYS 10.0 in the different dumping angles. Through modeling, loading, restricting and calculating, strain and stress field distribution of the hot-metal ladle were acquired. Finally, an assessment of strength and stiffness was made on the hot-metal ladle. The results show that in the process of tipping for the hot-metal ladle, maximum stress is 137MPa, maximum strain is only 0.681‰, maximum stress and strain have appeared in the stiffener plate which is located at the bottom of the trunnion, and strength and stiffness are qualified. The method which is convenient and practical, reasonable and reliable provides theoretical evidence for checking analysis and further optimal design of the hot-metal ladle.     

Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

 The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were considered responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a non-metallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydrophobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettabiliy can be changed by changing solid-liquid interface tension. The non-metallic inclusion removal in swirling flow tundish is studied. It shows that, under certain turbulent conditions, the particle concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.     

Evaluation of Scheme Design of Blast Furnace Based on Artificial Neural Network

Blast furnace scheme design is very important, since it directly affects the performance, cost and configuration of the blast furnace. An evaluation approach to furnace scheme design was brought forward based on artificial neural network. Ten independent parameters which determined a scheme design were proposed. The improved threelayer BP network algorithm was used to build the evaluation model in which the 10 independent parameters were taken as input evaluation indexes and the degree to which the scheme design satisfies the requirements of the blast furnace as output. It was trained by the existing samples of the scheme design and the experts＇ experience, and then tested by the other samples so as to develop the evaluation model. As an example, it is found that a good scheme design of blast furnace can be chosen by using the evaluation model proposed.     

Model of Forming-Accretion on Blast Furnace Copper Stave and Industrial Application

 Copper staves have been equipped on nearly all of BF (blast furnaces) with volume over than 1000 m3 in China since their introduction from abroad about more than 10 years ago. Because of short application and lack of experience, phenomena of thickened or naked of copper stave happen occasionally which influence production severely. So it is important to study the model of forming-accretion on BF copper stave and realize real-time monitoring of forming-accretion on different copper staves. Therefore, mathematic model of calculating accretion thickness by heat flow of BF is proposed, and the calculated results indicate that accretion thickness could be kept at a reasonable range of around 50 mm by controlling heat flux around 22.0 kW/m2. The monitoring program based on the model was applied to a certain BF in China successfully, and it is found that slip of BF near the inner wall is one of most important reasons that cause fluctuation of accretion thickness. During the period of scheduled maintenance of the certain BF, the thickness of accretion measured through the static pressure holes is in good accordance with the value calculated by the monitoring program, so the results calculated by the monitoring program can be used to guide industrial production.     

Zirconium content induced mitigation of mechanical anisotropy in 2:17 type SmCo magnets

The mitigation of mechanical anisotropy is observed in 2:17 type SmCo magnets by adjusting the Zr content This behavior is supposed to be closely related to the density of lamellar phase,the density of which is enhanced obviously with increasing Zr content.The other reasons which could cause the reduction of the mechanical anisotropy is discussed from the Zr-rich impurity phase to the atom substitutions and crystal lattice distortion.The observation of crack in nano scale that dearly forms angles of 60° and 90° with respect to the lamellar phase,indicates that the probable cleavage planes are crystal faces(1011) and(1010).The results of investigation can deepen the understanding of mechanical anisotropy and cleavage fracture in the SmCo magnets.     

Qualitative Analysis of Relationship between Refractive Index and Atomic Parameters of Solid Materials

The refractive index is one of the important parameters describing the optical properties of solid materials. However, it is difficult to obtain a quantitative relation between the refractive index and the structure and composition of materials. A qualitative relation between the refractive index and some atomic parameters of materials was proposed and demonstrated by some oxide optical crystals. A parameter P = r^-/F=r^-/( r^ ΔxD ) is defined, in which Δx is the difference of the electronegativities between cations and anions in the materials and r^ and r^- are the radii of cations and anions respectively. On the other hand, the factor D was introduced to describe the effect of mass difference of the ions. It is demonstrated by both theoretical discussion and experimental data that refractive index is a decreasing function of parameter P. The relation may be useful for the investigation of optical materials.