双辊薄带钢铸轧熔池电磁侧封模拟试验

报道双辊薄带钢持轧熔池电磁侧封低熔点合金模拟试验研究结果。在额定功率60kW、频率2500Hz的电源下，成功实现对高10cm金属熔池的例向电磁约束与封堵。     

连铸侧封技术的凝固终点参考模型自适应系统研究

为解决国内双辊连铸薄带成品率低、裂纹、易断带和轧卡等问题,对侧封技术进行研究。结果表明,侧封压力过大,引起结晶辊边与侧板磨损与电机功率消耗;侧封压力过小,又将引起漏钢。侧封板位置可以通过凝固终点位置来确定。通过采样薄带温度,建立凝固终点模型,可解决凝固终点不能测量及因干扰致其波动而不能实时修正侧封板位置的问题;通过模型参考自适应解决系统实时性和鲁棒性问题。     

金属薄带双辊连铸复合式电磁侧封的物理模拟

针对薄带双辊连铸的辊端金属液侧封问题,采用低熔点合金物理模拟实验,研究单纯的电磁侧封、电磁场复合有机玻璃挡板侧封、电磁场耦合内置或外置铁芯的耐材挡板侧封4种方式下的磁感应强度分布特点和侧封效果。结果表明:电磁场耦合内置铁芯挡板的侧封方式效果最好,可将金属液侧封高度提高3.3倍,且金属液的侧封高度随电流强度线性递增。同时还观察和分析侧封过程中金属液面波动现象。     

考虑材料非线性双辊铸轧辊套流热固耦合温度场研究

基于Procast连铸模块材料数据库,提取低碳钢物性参数随铸轧温度不断变化的散点数据进行非线性曲线拟合,并在此基础上考虑铸轧辊旋转、冷却系统、浸入式铸嘴、侧封板传热等影响,建立了辊套、熔池与冷却系统整体三维流热固耦合有限元模型并进行瞬态仿真,得出了双辊铸轧辊套整体温度分布情况及内、外表面的温度变化规律。结果表明,根据前处理方式得到的温度场更加贴合双辊铸轧实际生产情况,为辊套的设计和优化铸轧工艺参数具有一定的参考价值。     

薄带双辊连铸水口电磁制动的实验模拟

为控制薄带双辊连铸结晶器内金属液面的波动,提出了水口电磁制动（N-EMBr）设想,通过在水口区域施加稳恒磁场与直流电流,减缓水口金属液对双辊熔池的冲击文中对熔池液面的波动情况进行了实验模拟;观测了有无电磁制动及不同水口浸入深度等条件下熔池液面的波动情况,并测量了水口金属液冲击力的相对变化。结果显示,随输入电流增大,水口出量减小,双辊结晶器内液面波动幅度和频率降低,熔池液面趋于平稳,这表明水口电磁制动可望有效抑制熔池液面波动,为解决薄带双辊连铸结晶器内金属液的布流和流动控制问题,提供一种可选择的方法。     

热镀锌电磁封流技术的研究综述

热镀锌是镀锌板生产过程中必不可少的步骤,而热镀锌电磁封流技术相对于传统热镀锌技术具有带钢表面无划伤、沉没辊和稳定辊不被腐蚀、维修频率低和工作效率高的优势,具有重要的工程应用价值。首先,介绍了热镀锌电磁封流技术的特点和意义。其次,分别介绍了电磁泵热镀锌电磁封流技术、CVGL热镀锌电磁封流技术、直流磁场热镀锌电磁封流锌技术和永磁感应密封热镀锌电磁封流技术的工作原理、研究现状、技术组成及其优缺点。再次,分析了热镀锌电磁封流锌工作过程中,温度场、流场、固体结构力学场和电磁场之间复杂耦合的特点,并且依据热镀锌电磁封流过程的技术特点,指出了热镀锌电磁封流过程中带钢振动的抑振技术、锌液不稳定流动抑制技术、温度稳定性控制技术、张力控制等关键技术。最后,提出了电磁装置结构参数优化、带钢振动抑制技术和基于大数据的过程控制技术是提高热镀锌电磁封流锌工作过程的关键技术。     

优化工艺下电磁搅拌对板坯冶金效果的影响

为了研究板坯辊式电磁搅拌器对板坯冶金效果的影响,采用现场试验的方法,经过调整电磁搅拌工艺参数及连铸工艺参数,揭示了优化工艺条件下电磁搅拌对板坯冶金效果的影响。研究表明,电源频率为7 Hz,电流分别为0、100、400 A时,电磁搅拌力依次增强,对板坯的冶金效果逐渐改善;当电磁搅拌辊的数量增加时,板坯非稳态下的低倍质量提高;当相同电磁搅拌参数应用于相同钢种时,只有在综合优化连铸工艺参数条件下才能得到好的冶金效果。参数条件为电源频率7 Hz、板坯拉速0.9 m/min、电流400 A。     

工艺参数对振动铸轧熔池的影响

为了探究双辊薄带振动铸轧技术中，艺参数对振动铸轧熔池流场和温度场的影响，采用有限元软件构建了双辊薄带振动铸轧熔池仿真模型。基于该模型，研究铜带厚度、铝板出口厚度和铸轧速度对熔池流场和温度场的影响，并通过轧辊急停获得双辊薄带振动铸轧熔池切片，验证了该模型的准确性。结果表明：铜带厚度、铝板出口厚度和铸轧速度对熔池流场的影响与轧辊振动相位有关，工艺参数与轧辊振动共同改变熔池流场。工艺参数变化对熔池上部温度场影响较小，对熔池下部尤其是熔池底部温度场影响较大。     

双辊薄带铸轧熔池近侧封板处流场与温度场研究

以某钢铁公司的双辊薄带连铸机为原型,通过建立三维铸轧熔池流热耦合数学模型,研究了铸轧熔池近侧封板处的流场和温度场变化规律。结果表明,近侧封板处铸轧熔池存在三个较大的的漩涡区,与熔池内部流场有较大差异。研究还发现,端面布流水口倾角严重影响着熔池液面波动和上部钢液混合均匀程度,合理的水口倾角有利于熔池出口Kiss点高度的均匀一致,提高薄带产品质量。     

工艺参数对双辊薄带铸轧中心层偏析影响

双辊薄带铸轧过程中工艺参数对中心层偏析有重大影响,针对双辊薄带铸轧机的特点,利用多相流技术建立完全耦合溶质场、流场、温度场的数学模型,对铸轧熔池中液相-液固两相-固相同时存在的复杂凝固过程进行模拟仿真,研究分析铸轧熔池中Mg、Si元素溶质场与流场分布特征,对比研究不同工艺参数(浇铸温度、辊缝宽度)对铸轧薄带中心层偏析的影响规律,并结合铝合金6061的铸轧实验对结论进行验证。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.