HC六辊冷轧机垂扭耦合振动分析

轧机系统异常耦合振动是影响轧件质量的重要因素。通过对某钢厂2180型六辊冷轧机的现场测试及分析发现工作辊的异常振动会传递到主传动系统中,造成齿轮箱等部件的故障,万向接轴并未有效隔断振动的传递。根据实际参数建立了包含主传动系统扭转振动和工作辊垂直振动的轧机耦合振动数学模型,并求解了模型的响应特性。同时,通过仿真分析发现了轧机垂扭耦合振动的真实性。定量分析发现系统发生耦合振动时工作辊扭转角及振动位移变化相对较大,扭转振动对垂直振动的影响较为明显。此方法为抑制轧机系统振动、减少设备故障提供了理论依据。     

CSP轧机主传动系统致振因素的分析

对CSP轧机主传动系统异常振动现象进行分析,为了确定引起振动的原因,分析了主传动系统机械间隙的存在对振动产生的影响,以及轧制界面因轧制力矩的变化对振动产生影响。通过MATLAB的Simulink软件对轧制力矩进行仿真发现,轧制力矩的波动对主传动系统振动的产生有直接影响;摩擦系数的波动对主传动系统振动产生的影响,是对主传动系统产生稳态的自激扭转振动;在对变频器控制的电气参数与主传动系统扭振的影响分析得出,由电磁谐波产生的谐波转矩,使主传动系统产生相应的扭振响应。最后在理论上提出了一系列抑制振动的措施。     

1700带钢冷连轧机主传动系统扭振研究

武钢１７００冷连轧机主传动系统的弧形齿接轴，在轧机运转过程中产生剧烈的振动。为了诊断其振动原因，从轧机主传动系统扭振动态特性进行了研究，结合现场测试和频谱分析，得出相应的结论，为解决接轴的振动问题提供理论依据。     

厚板轧机含间隙主传动系统扭振的研究

由于设计、安装和磨损等因素导致轧机主传动系统存在不同间隙,在咬钢冲击或打滑条件下振子在间隙内发生重复碰撞,造成振幅大幅度增加,是导致轧机主传动系统零部件异常破坏的主要原因。本文基于5000 mm厚板轧机,对咬刚冲击和打滑两种情况分别建立扭振模型,采用数值计算方法,求出扭矩放大系数,得到受不同间隙影响的系统动态响应的仿真结果,并比较分析不同情况下引发的扭振响应。结合现场工程实际情况对轧机主传动系统中各间隙及加载时间对扭矩放大系数的影响进行分析,研究结果可为控制和分析该类轧机扭转振动提供重要的理论参考。     

上、下辊分别驱动的四辊轧机主传动系统扭振研究

对某厂“1+4”热连轧开坯机的扭转振动动态特性进行了研究。在一定的简化基础上,建立了轧机主传动系统的扭转振动力学模型和数学模型,获得了系统的固有频率和主振型及其对转动惯量和扭转刚度的灵敏度。对系统在各阶模态下的能量分布进行了计算和比较,确定了系统的危险模态。根据系统的输入得出了各轴段扭矩放大系数的仿真结果,以判定扭振发生时主传动系统的最大动力载荷。计算发现轧机主传动系统扭振固有频率分布合理,基本满足最佳动力设计准则。研究结果对于实际生产和系统扭振问题的识别与解决具有指导作用。     

铝热轧机含间隙主传动系统扭振分析

在铝热轧机轧制生产中,轧机主传动系统中存在着间隙,该间隙会在咬料时引起对系统的冲击,会进一步增加系统的扭矩放大系数。用保守系统拉格朗日方程建立了某铝带热轧机主传动系统的扭转振动数学模型,并用模态叠加法计算了系统在不考虑间隙和考虑间隙两种情况下,主传动系统在冲击载荷作用下的动力学响应,得出了各轴段扭矩放大系数的仿真结果,并进行比较分析。     

轧机垂直振动的研究现状与展望

通过对国内外各种类型轧机在高速轧制薄板带时存在的垂直振动问题进行了分析与总结,分析了轧机产生垂直振动的机理和引起轧机振动的主要因素,并提出了有效控制轧机垂直振动的措施.     

基于Adams的冷轧机工作辊振动分析与仿真

随着对冷轧机振动研究的不断深入,发现冷轧机工作辊所呈现的振动通常都是耦合振动。首先建立冷轧机主传动系统和冷轧机辊系的简化振动模型,并利用Matlab软件计算出冷轧机主传动系统和辊系振动模型的固有频率。然后利用Adams软件对冷轧机辊系进行动力学仿真,并在仿真过程中添加3倍振频的扰动力和扰动力矩。仿真结果表明:在无外界干扰情况下,由于轧辊间存在的摩擦力,该冷轧机会发生自激振动;对于六辊冷轧机,中间辊的水平振动也会影响工作辊的垂直振动和扭转振动;当垂直振动和扭转振动同时发生时,轧机工作辊每种振动会显示其他振动的特征。     

四辊轧机垂直振动特性研究及测试分析

为研究四辊轧机系统的垂直振动特性,考虑到四辊轧机具有较复杂的振动过程,建立了四辊轧机非对称6自由度垂直振动模型,利用机械振动学牛顿第二定律理论,构建四辊轧机的垂直振动系统动力学方程。采用Matlab软件对四辊轧机6自由度系统垂直振动模型的固有特性进行理论计算,对系统各阶固有频率及其相应的主振型进行分析,得到了第5阶固有频率是引起四辊轧机强烈自激振动的主要频率。通过现场垂直振动测试平台的验证,表明了该系统垂直振动模型具有较高精度的优点。以上研究结果为研究四辊轧机的现代动态设计、动力学分析以及抑振减振等问题提供了一定的理论基础。     

冷连轧机多种水平共振状态特性对比研究

针对冷连轧机工作辊轧制过程中的水平振动现象,建立轧机辊系非线性水平振动模型。采用多尺度法求解得到冷连轧机水平方向主共振、超谐波共振和次谐波共振下的幅频特性方程。仿真表明:轧机参数的变化和不同的共振状态会对系统振动的幅值、共振点、共振区域及脊骨线位置产生明显影响。系统在次谐波共振状态下的振动相对稳定,而在主、超谐波共振情况下有明显的跳跃现象和不稳定区域产生。对比系统位移动态响应,发现次谐波共振响应曲线相对于超谐波共振情况下的位移正、负幅值减小且趋于对称,有利于减少轴承座撞击牌坊现象的产生。对比系统位移分叉特性,发现不同共振状态系统随着干扰力幅值的变化表现出不同的周期运动规律。以上研究为抑制轧机水平振动提供了参数区域和理论参考。     

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).     

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.     

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.     

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.