Influence of Billet Size on Flow,Solidification and Solute Transport in Continuous Casting

The dead load crown of hydraulic elastic bulging roll was discussed using the theory of elastically supported beam, and the dead load experiment was carried out. The theoretical calculation is consistent with the experimental result. The structure parameters for the thickness of roll sleeve, the length of the oil groove and the crown of roll were discussed. The fundamental principle of determining the parameters was put forward. The theoretical basis of the application of the hydraulic elastic bulging roll was established.

特高压无功补偿装置管母支撑绝缘子断裂原因分析

针对一起特高压无功补偿装置管母支撑绝缘子断裂事故,介绍了事故发生概况,并对断裂的绝缘子进行了相关检查及试验分析,指出此次事故的主要原因是绝缘子烧结工艺不当,水泥胶装不严实,安装端存在较大应力,诱发多处裂纹造成绝缘子断裂。为防止再次发生绝缘子断裂,提出合理的解决对策。

1000 kV特高压串补控保系统CT取能异常分析

基于特高压南阳站长南Ⅰ线串补控保B系统CT取能异常事件,分析了特高压串补控制保护系统组成及平台测量箱的取能方式,对事件概况及现场情况进行了描述,通过理论分析和现场检查,指出此次事故的原因是串补平台上CT取能系统故障导致非功能性切换为地面激光送能。通过此次分析为其他厂站处理类似问题积累了理论基础和实际经验。

Improvement of Inner Quality of High Carbon Wire Rod Steel Using Combined Electromagnetic Stirring

To improve the quality of high carbon wire rods,combined electromagnetic stirring was introduced in the continuous casting of round billets with a diameter of 250mm at Tianjin Rockcheck Steel Group Co.In this paper,the positioning of final electromagnetic stirring(F-EMS)was determined by nail-shooting method.Furthermore,the effect of mold electromagnetic stirring(M-EMS)on the macrostructure and internal defects in the round billets was investigated to find out the optimal operating parameters for continuous casting of SWRH 82B round billets.The results show the desirable positioning of F-EMS locates 9.7m below the mold level where the molten steel can be effectively driven by electromagnetic force and disperse central composition segregation.The shrinkage cavity is totally eliminated with the rotational M-EMS.The ratio and index of central composition segregation and center porosity can be reduced significantly. Furthermore,the equiaxed crystal ratio is considerably increased to 64%under 480A/3Hz M-EMS and 500A/10Hz F-EMS. Fine microstructure and mechanical property of wire rod are presented after optimization of combined electromagnetic stirring.Accordingly,the probability of occurrence of cup-cone fracture of wire rod is reduced dramatically.

Effect of 31.2T Magnetic Field on Microstructure and Performance of an Ag-45.8wt%Ni Alloy

Ag/Ni Multilayers were prefabricated by Accumulative Roll-Bonding(ARB),with an average layer thickness ranging 20-100 nm.The Ag-45.8wt%Ni alloys were annealed under 31.2T high magnetic field to study its effect on microstructure and performance.31.2T high magnetic field significantly suppressed the coarsening of layer structure during annealing,the magnetic field parallel to the layer has a larger suppression effect.As the annealing temperature increased,the resistivity of Ag/Ni multilayers increased,and the hardness decreased.The case of perpendicular high magnetic field has the largest resistivity and the largest hardness,compared with the other two cases.The hysteresis loops shows that Ag-Ni has a hard ferromagnetic property.The case of parallel magnetic field has the largest coercivity about 90Gs.

Effect of Electromagnetic Stirring on the Distribution of Nb Phase in Cu-5wt%Nb Alloys

The effect of electromagnetic stirring(EMS)on the distribution of Nb particles in solidified microstructure of a Cu-5wt%Nb alloy were studied.In this paper,we have Cu-5wt%Nb alloy remelted and solidified with or without electromagnetic stirring,to study the effect of EMS on the distribution of Nb phase and the hardness of ingots.The 300A/16Hz EMS has refined the mircostrucrure of Cu-5%Nb alloy,with smaller particles sizes and larger amounts,and is benefit to the homogenous distribution of particles.The fitted lognormal distribution of particles diameter that in case without or with EMS are compared,and the EMS case has the highest frequency percentage in the range of smaller size. EMS considerably increased the hardness of Cu-5%Nb alloy ingot.

Effect of M-EMS Parameters on Quality of 82B High Carbon Steel

In this paper,the rule of M-EMS on Φ250mm 82B high carbon steel during the casting process was investigated by numerical simulation and experiments.The influence of M-EMS current and frequency on distribution of flow field was researched.The simulation results show that:At the same current,velocity increases with the frequency increase.With the increase of frequency,the velocity first decreases and then increases as the frequency increase along the casting direction. At the same frequency,velocity increases with the current increase.The turbulence zone also become more strenuous, especially in free surface,the suitable turbulence is benefit to uniform steel temperature.Experiment results show that the quality defects of 82B high carbon steel can be significantly improved with M-EMS.The zone of central pipe decreases. With the increase of current,equiaxed zone ratio increases.Considered the results of numerical simulation and experiments, the optimized EMS parameters of Φ250mm high carbon steel are the stirring current of 480A and the stirring frequency of 3Hz,which can improve strand quality greatly.

The Research on Soft-Contacting Electromagnetic Continuous Casting in Baosteel

The paper introduces the research and new development on soft-contacting electromagnetic continuous casting in Baosteel.At the year of 2008,Baosteel successfully completed the carbon steel SCEMCC industrial experiment in a 6-strand curved type round billet caster.At the year of 2011,Baosteel selected another 3-strand curved billet caster. Baosteel successfully developed the SCEMCC mold for the first time to do the industrial production experiment for stainless steel round billet continuous casting.Then,in the same stainless steel caster,the square billet SCEMCC mold was successfully developed too.And at the beginning of the year 2012,the square billet SCEMCC of SUS304 and SUS303Cu was implemented up to now.It was proved the machine system was reliable for the long time production.The industrial experimental result shows the soft-contacting electromagnetic continuous casting can reduce the depth of oscillation mark from about 0.7mm to near zero.The SCEMCC billets without surface grinding were transferred to mill tubes,of which the quality is satisfied.

Development of a Non-Contact Electromagnetic Surface Velocity Sensor for Molten Metal Flow

During continuous casting of steel,knowledge of both direction and magnitude of the velocity at the mold surface is of special interest.However,the surface is covered by a non-transparent layer of mold powder to prevent formation of slag.Thus,this meniscus flow cannot be registered by optical measurement techniques.Non-contact measurement methods are of interest.One of such non-invasive techniques is Lorentz force veloeimetry(LFV).It is based on measuring the electromagnetically induced force acting on a magnet system.In this paper we present a series of experiments that aim to demonstrate the feasibility of using two identical velocimeters,termed Time-of-Flight LFV(ToF LFV).Using ToF LFV the free-surface velocity may be purely determined by cross-correlating the two force signals delivered by the two force sensors.We have developed a special prototype of such a measuring device termed meniscus velocity sensor(MVS).It has been designed to record local surface velocities in high-temperature metal melts.At Ilmenau University of Technology,the method has been successfully tested using both solid body movement and Ga^(68%)In^(20%)Sn^(12%)as a low-melting model melt.In the present paper we apply this technique to the case of high-temperature metal melts.In more detail,we present test measurements under industry-relevant conditions using both Sn^(32%)pb^(52%)Bi at 210℃ and molten steel at about 1700℃.These experiments were conducted at Key Laboratories on EPM at North Eastern University.The evaluation of the data shows that our prototype of MVS works well in producing reproducible signals of which surface velocity can be determined.

Effect of High Magnetic Field on Solidified Structure and Properties of Cu-Cr In Situ Composite

The microstructure of ripening processed Cu-15%Cr alloys and deformed samples were examined under a 12T high magnetic field.The high magnetic field has accelerated the Ostwald Ripening process of Cr phase,the Cr-rich particles in 12T HMF case are coarser compared with 0T case.The 12T high magnetic field increased the peak strength of Cu(111)crystal plane and Cr(110)crystal plane,and appeared to has an orientation effect.Compared with the 0T case, the 12T high magnetic field case decreased the tensile strength and hardness.

Large Magnetostriction of Fe-Ga Alloys by Solidification With a Static Magnetic Field

A simple but effective process to fabricate the bulk and practical Fe-Ga alloys at low fields is proposed just by applying a static magnetic field to their solidification process.We have introduced a static 1-T magnetic field to solidify the Fe-17%Ga alloys.The results indicate that the magnetostriction of a polycrystalline textured Fe-17%Ga alloy is increased about threefold by solidifying with a 1-T magnetic field compared to that without a magnetic field.This large magnetostiction could be attributed to the increasing volume fraction and the strong texture of the disordered α-Fe phases. The systematic analysis shows that they are originated from the undercooling and orientation effects induced by the imposed magnetic field during the solidification process.

Effect of Magnetic Field on Solidification Microstructure of Cu-20wt%Nb Alloys and Properties of the In-Situ Deformed Wires

Magnetic field has great impact on the second phase distribution in metal solidification process.In this paper, we have Cu-20wt%Nb alloy remelted and solidified with or without the imposition of magnetic field,to study the effect of magnetic field on the distribution of Nb phase and the properties of deformed wires.Magnetic field has an inhibiting effect on the ripening process of Nb particles,and is benefit to the prolongation of Nb-rich phase in deformed wires.Both the ultimate tensile strength and conductivity in 1 T case is larger than that in 0 T case.

Microstructure of Cu-6%Ag Alloys Solidified With Different EMS and Their Drawn Properties

The effects of different electromagnetic stirring currents on the microstructures of Cu-6%Ag alloys by applying electromagnetic stirring during solidification process are investigated experimentally.The results show that with increasing stirring current,the macro-microstructural grains of the Cu-Ag alloys are refined gradually and evenly distributed.The observation on the microstructure indicates that the primary Cu dendrites become shorter and thicker,and the secondary dendrites are underdeveloped with small-sized equiaxed dendrites with increasing current.Cu-6%Ag alloys solidified with electromagnetic stirring are drawn to the composite wires with different drawing ratios.The results show that their microstructures are refined along the drawing direction when the stirring current increases from 100 A to 200 A. As the current increases to 350 A,the microstructure is not changed obviously.Correspondingly,the tensile strength of Cu-6%Ag alloys increases and the conductivity reduces with increasing drawing rate.Cu-6%Ag alloys could get the better strength with stirring current of 200 A,which is consistent with the microstructural results.

Numerical Simulation on Distribution of Stress in the Electromagnetic Soft-Contact Continuous Casting Mould

A two-dimensional axisymmetric finite element model for stress distribution of billet in electromagnetic soft-contact continuous casting mould was established by a two-way coupled method.The contact state between solidified shell and mould was described to simulate the thermal-mechanical behaviors in the soft-contact mould.And the effects of frequencies and currents on stress distribution of billet had been discussed and analyzed.The results show that the equivalent stress of initial solidification shell both at its outer and inner surface decreases but at the bottom the equivalent stress of two sides of shell both increases when the current intensity is 1600 A,and the frequency is 20 kHz,compared with the status of conventional continuous casting.

Effect of Rotating Electromagnetic Stirring on Solidification Structure of Incoloy 800H

In this work,the solidification structure of Incoloy 800H with rotating electromagnetic stirring(R-EMS)and without R-EMS were investigated.Comparing the structure without R-EMS,structure with R-EMS is greatly affected by the R-EMS.From the point of view of dendrites,we studied the evolution of solidification structure of Incoloy 800H with R-EMS,consisting of the fine equiaxed dendrites,the long unidirectional dendrites,cross dendrites and equiaxed dendrites.According to the evolution,dendrite fragment dissociation was presented and proved by acquiring the main element composition variation of dendrite trunk in the different zone.As a result,element segregation of the ingot is improved and the grains are refined.

Solidification Structure of Cu-Fe Alloy under a Rotary Electromagnetic Stirrer

The effect of rotary electromagnetic stirring(EMS)on the Cu grain size and Fe dendrites is investigated in this paper,in order to get a Cu-Fe alloy ingot with good quality.The macro-and micro-structures are observed by Leica-DMR optical microscope.The solidification structures of Cu-2 and 8wt.%Fe consist with finer equiaxed grains. The Cu grain size is most sensitive to the Fe content.EMS can't effectively improve the grain size for the Cu-Fe alloy. For ingot cooled without EMS,there are also many large Fe-rich particles distribute in the Cu-matrix,beside the Fe dendrites,because of the existence of metastable miscibility gap in the undercooled liquid state.And the Fe-rich phases are not found in the ingots with EMS,indicating the EMS can affect the undercooling of the liquid and further restrain the liquid phase separation.Under the EMS,the Fe dendrites break up into many smaller Fe fragments.And the size of Fe fragments decreases with the increasing stirring current.

Effect of Electromagnetic Stirring on Fine Grain Formation and Tensile Property Improvement for Fe-Ni Superalloy

Due to its excellent creep rupture strength and low cost,superalloy GH2984 has becoming a promising material to be used as heat exchanger in the prospective 700 oC fossil power plant.The mechanical strength,which is a particularly important indicator for the superalloy,strongly depends on the grain size and crabide distribution.In current study,we have investigated the influence of a rotating magnetic field(RMF)on the solidified microstructures and tensile properties of superalloy GH2984.RMF has been applied to provide a forced convection within the solidifying melt.The melt stirring by a sufficiently high magnetic field provides homogeneous grain size and elements distribution in the sample volume.Meanwhile,yield strength is found to be effectively enhanced for the sample solidified under magnetic field.The result has demonstrated that the RMF method on the melt solidification process shows a promising perspective for refining the grains and promoting the mechanical strength of superalloy GH2984.

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.

Evolution of Microstructure for Superalloy Inconel 625 by Electromagnetic Stirring

Due to its excellent creep rupture strength and prominent corrosion resistant properties under various circurmstances,superalloy Inconel 625 has been extensively used in aviation industry and chemical industry.The mechanical strength,which is a particularly important indicator for the superalloy,strongly depends on the matrix structure and crabide distribution.In current study,we have investigated the influence of linear travelling magnetic field(LMF)on the solidified microstructures of superalloy Inconel 625.The result has demonstrated that the solidification route is not affected but the size and amount of NbC and Laves+γ eutectic structure are significantly influenced by the application of electromagnetic field due to the introduction of a forced convection which changes the diffusion process of element niobium.The application of LMF has increased the mount of NbC with larger size,as well as the fraction of eutectic structnre.Furthermore,Compared to the normal cooling condition,the Nb and Mo elements were observed to be enriched in the interdendritic area with LMF,which is confirmed to be the main reason to enhance the growth of carbide and Laves phase in solidification process.

Effect of Electromagnetic Stirring on Solidification Structure of Incoloy 825 Superalloy

Superalloy Inconel 825 has been extensively used in chemical industry and transportation industry due to its excellent creep rupture strength and prominent corrosion resistant properties under various circumstances.However,the mass production of this alloy by continuous casting method is restricted because of the serious macrosegregation and coarse grains in the billet.In current,a linear travelling magnetic field was introduced in the solidification process of Inconel 825 with the aim of changing the final microstructure by electromagnetic stirring(EMS)force.The results have indicated that the dendrite structure of Incoloy 825 is refined obviously with applying EMS,and the mechanism of dendrite refinement is presumed to the introduction of a forced convection within the solidifying melt.Moreover,The number and the size of precipitated phases including carbide and nitride were found to be significantly reduced with EMS, a phenomenon on the reduction of interdendritic segregation of titanium and molybdenum was simultaneously observed, which demonstrated that he release of interdendritic segregation by EMS inhibits the growth dynamic of carbide and nitride from the melt.