热连轧薄带钢头尾窄尺的原因分析及改进

针对日照钢铁控股集团有限公司热连轧薄规格低碳钢带头尾窄尺问题,结合实际生产工艺研究了粗轧、精轧设定,活套、卷取张力对带钢窄尺的影响.通过改善粗轧控宽、精轧模型设定、精轧张力设定和卷取张力设定,有效提高了热连轧薄带钢的尺寸精度,为薄规格带钢生产提供了技术依据.     

热连轧自动厚度控制系统

<正>传统的带钢热连轧生产线包括板坯库、加热炉区、粗轧区、粗精轧之间的中间辊道及飞剪、精轧区、热输出辊道及层流冷却装置、卷取区、运输链、成品库等。带钢热连轧生产工艺在相当长的一段时间内变化不大,直到     

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为了提高不锈钢热连轧的宽度控制水平,通过粗轧短行程控制来改善带钢头尾宽度控制曲线。根据热轧粗轧短行程控制理论,分别使用了三段折线式和两段抛物线式来进行控制,同时根据带钢头尾的宽度偏差对短行程曲线进行自学习。现场投用表明:这种粗轧短行程控制模型能够明显地改善中间坯的头尾偏差,提高带钢成材率。     

不锈钢热连轧机粗轧短行程控制

为了提高不锈钢热连轧的宽度控制水平,通过粗轧短行程控制来改善带钢头尾宽度控制曲线。根据热轧粗轧短行程控制理论,分别使用了三段折线式和两段抛物线式来进行控制,同时根据带钢头尾的宽度偏差对短行程曲线进行自学习。现场投用表明:这种粗轧短行程控制模型能够明显地改善中间坯的头尾偏差,提高带钢成材率。     

热连轧粗轧立辊磨损模型的研究与应用

在热轧带钢生产过程中,粗轧立辊会不可避免地出现磨损现象。立辊磨损沿辊面非常不均匀,下线轧辊辊面呈梯形,最大磨损处磨损量可达5 mm。这严重影响了粗轧模型的设定精度,从而使带钢宽度控制精度降低。为了提高模型对立辊的设定精度,对辊面磨损范围各个位置的磨损量进行了分区计算,建立了新的粗轧立辊磨损计算模型。该模型在某1 500 mm热连轧生产线的应用表明,粗轧立辊磨损量计算值与实测值吻合较好,粗轧模型宽度预报稳定、准确。     

基于遗传算法的精轧区温降模型研究

采用有限差分法建立了热连轧精轧机组带钢的温降模型,并且通过实测数据,应用遗传算法对所建模型进行了优化。经验证,该模型的带钢终轧温度计算精度在10℃以内。     

带钢精轧阶段高精度宽度控制策略

出于节能考虑,带钢热连轧工艺增加中间坯的厚度,提高精轧开轧温度,降低粗轧和精轧总能耗。由于增加了中间坯厚度,精轧过程产生宽展,热连轧机精轧机组采用了两个立辊机架的设计方案。针对此种设备布置,以高精度的宽度控制为目标,提出了一种宽度自动控制策略,包括两个立辊的速度、辊缝的过程设定以及自学习算法。现场应用效果表明：该控制策略保证了穿带和轧制过程的稳定性,宽度精度高,宽度偏差控制在3 mm之内的达到95%以上。     

热连轧带钢头尾鱼尾形状模拟控制研究与应用

针对某钢厂1500热连轧机组粗轧区轧制过程的工艺特点,利用ANSYS/LS-DYNA建立了立辊/水平辊轧制的三维弹塑性有限元模型。研究了带钢在不同的立辊侧压量、水平辊压下量、板坯的原始宽度和厚度对轧后中间坯头部和尾部形状变化规律的影响,建立控制头尾形状的短行程控制曲线模型用来改善头尾形状。通过现场实际应用可以看出,此短行程控制模型能够有效的减少头尾失宽及鱼尾长度,从而减小头尾切损量,提高成材率。     

热轧带钢宽度控制模型的改进

针对济南钢铁集团公司热连轧厂宽度控制手段较单一、且粗轧前没有测宽仪而影响成品带钢宽度精度的问题$重新解析了宽展模型的参数,同时改善了宽展自学习方式,提高了成品宽度控制精度。     

热连轧带钢轧机设备的发展

本文简要介绍热连轧带钢轧机发展的基本方向以及热轧机主要设备(加热炉区、粗轧区、精轧区、地下卷取机)的新发展,同时阐明设备和工艺的互相依存和促进发展的关系。     

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。