异形坯结晶器三维流场模型的研究

依照湍动能理论及异形坯连铸的特点 ,建立了异形坯结晶器三维流场数学模型。运用该模型分析了不同水口参数及工艺参数条件下的流场分布 ,从而得出影响结晶器内钢液流动的因素有水口倾角、水口浸入深度及拉坯速度。结果表明 :采用上倾 15°有利于夹杂物上浮 ;拉速 0 .9m/s可使流场分布均匀 ;适宜的水口深度可选 2 0 0mm。利用该模型可对连铸过程进行离线分析 ,确定最佳参数 ,并可作为在线控制模型的基础     

板坯连铸结晶器流场及液面波动水模研究

以我国实际生产的某结晶器为原型,建立1∶1有机玻璃水模型,模拟研究了结晶器断面和中间包液位对板坯连铸结晶器流场形态和结晶器液面波动的影响。中间包液位改变了水口出口的压力从而使结晶器流场和液面波动发生变化。通过实验研究进一步认识了板坯连铸结晶器液面波动及其影响因素,并用以指导高质量连铸坯的生产。     

宽厚板坯连铸结晶器内的钢液流场的数值模拟

基于流体力学的基本理论,针对连铸结晶器的结构和工艺参数,利用商业软件fluent的k-ε湍流模型,实现了对结晶器内钢液流场的三维数学模拟。重点分析了浸入式水口的插入深度、水口侧孔倾角以及拉速等工艺参数对结晶器钢液流场的影响。结果表明：对于断面为2300mm×250mm的板坯结晶器,水口插入深度为150mm,水口倾角为向下15°,拉坯速度为1.2m/min时,结晶器内的流场较好。数值模拟结果可为宽厚板坯连铸结晶器确定合理工艺参数提供理论依据。     

板坯连铸结晶器内钢液流动数值模拟

利用商业软件PHOENICS建立一个三维有限差分模型,对板坯连铸结晶器内钢液流动进行了数值模拟.重点研究了浸入式水口结构尺寸和工艺参数对连铸结晶器内液面紊动能和窄面冲击压力分布的影响.计算结果与水模实验结果吻合较好.     

大板坯连铸结晶器内熔体流动的DPIV物理模拟

采用DPIV技术(粒子图像测速技术)对大板坯连铸结晶器内熔体的流动进行了物理模拟。通过测试分析结晶器内流场,描述了结晶器内熔体流动的基本特征,研究了浸入式水口结构、浸入深度、拉坯速度对结晶器流场的影响。TECPLOT作为后处理软件进行速度向量、流线和各种等值云图的计算与分析,从而揭示金属液流动的规律,以便有目的地控制流动和水口工艺,改善连铸坯的组织性能。结果发现,0°水口与15°水口相比,流体在结晶器上部向上流动的趋势更加强烈,而冲击深度变浅;随着水口浸入深度的增加,液面流速降低,液面附近向上运动的回流范围变得越来越大,向下回流的涡心位置下移。试验表明:液面高度要控制在100～150mm;拉坯速度增加时,结晶器内的流速随之增大,自由表面变得更加不稳定,同时液流对窄面的冲击能量增强。     

大方坯连铸结晶器水口优化模拟探究

为了研究不同浸入式水口类型对结晶器内流场流动的影响,以结晶器水口优化为出发点,利用物理模拟和数值模拟两种手段对断面280 mm×380 mm大方坯结晶器不同水口开展优化研究。本研究首先构建了一个1∶1结晶器水模拟试验装置,实现不同浸入式水口下的连铸流动模拟,利用PIV测量了不同水口下的结晶器截面流场,然后利用Fluent软件进一步研究了浸入式水口开孔角度、开孔数目、安装角度等参数变化对结晶器内流场以及液面波动的影响。物理模拟和数值模拟研究表明,开孔角度向上时,波动范围大于5 mm;开孔角度水平时,对窄面冲击速度过大,达到0.35 m/s;较双孔水口,四孔水口液面速度为0.22 m/s,小于卷渣临界速度值;水口安装角度改为对角线时,强化了内流场角部流动,整个流场流动更加稳定。     

连铸板坯结晶器流场的数值模拟

板坯结晶器液面流速对保护渣熔化、坯壳均匀性都有着较为重要的影响.使用瞬态数模模拟的方法对板坯结晶器内钢液流动进行研究,通过对比结晶器液面平均流速,评价了不同参数对结晶器流场的影响.结果 表明,水口倾角由20°将至10°时,表面流速平均值由0.192 m/s增加至0.211 m/s,表面流速提高,有利于保护渣的熔化和流场...     

板坯连铸结晶器内钢液流场的数值模拟

用流体力学的三维计算软件,运用湍流脉动动能k方程和湍流脉动动能散耗率ε方程的k-ε双方程模型在给定的数值计算条件下,对板坯连铸结晶器内钢液的流场进行了模拟.通过数值计算,研究了浸入式水口出口面积、水口插入深度、铸坯断面尺寸等工艺参数对结晶器内钢液的流动的影响,为结晶器及水口的优化设计提供了依据.     

水口吹氩对结晶器弯月面波动的影响

水口吹氩时,结晶器液面波动行为对夹杂物的去除、卷渣、漏钢和拉裂的防止很重要。利用水模型实验研究了氩气流量、浇铸速度、铸坯宽度和浸入式水口的张角、出口面积、浸入深度对结晶器弯月面波动的影响,并运用数值模拟方法对结晶器流场和实验结果进行了分析。     

圆坯连铸结晶器钢液流场研究

应用ANSYS有限元软件,对圆坯连铸结晶器(断面尺寸为φ450mm)中钢液的紊流流动特点,模拟计算不同工艺参数条件下的流场,并用水模试验结果进行了验证.从流场的数值模拟计算结果还可以判定:圆坯连铸采用直孔形水口时必须要用外力来改善结晶器内流体的流动.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。