高Cr支承辊KD法锻造工艺模拟研究

针对高Cr支承辊锻件采用传统WHF法锻造导致表面开裂的现象,本文通过数值模拟技术,对105A级Cr5锻钢支承辊进行了两种不同工艺方案的模拟对比与分析,为我公司今后应用KD法生产大型高Cr支承辊提供理论依据。     

大型支承辊锻件缺陷分析

通过低倍检验、金相分析、断口分析、电镜扫描分析等方法对支承辊锻件缺陷进行综合分析,结果表明:该支承辊锻件缺陷性质为二次缩孔残余,浇注温度偏低对该锻件缺陷的产生具有重要影响。     

国内最大的φ2000mm整锻支承辊在第二重机厂制造成功

<正> φ2000mm整锻支承辊是二重厂为上钢三厂生产的3300mm轧机中的关键部件之一,是迄今我国生产的最大整锻支承辊.φ2000mm整锻支承辊产品重量达107t,材质为高碳合金钢.其锻件260t真空浇注钢锭120MN水压机锻造而成,锻件重量达154t.最终热处理采用喷雾淬火+高温回火,辊身硬度达Hs45以上.     

两种连续局部塑性成形工艺对锻件微观组织的影响

通过模拟分析与实验分析结合的方法,验证连续局部塑性成形微观组织演变有限元模型的正确性,采用该模型对42CrMo钢坯料辊锻过程中的组织晶粒度进行预报,研究42CrMo钢辊锻过程的奥氏体晶粒尺寸演化规律;对楔横轧变形过程中组织晶粒度变化进行研究,并对两种连续局部塑性成形后锻件组织晶粒度进行对比。研究结果表明,辊锻变形坯料P1、P2、P3处奥氏体晶粒尺寸实验结果与有限元预报结果吻合良好,晶粒尺寸变化为动态再结晶细化;楔横轧变形过程中,动态再结晶和奥氏体晶粒长大作用同时发生;通过对两种连续局部塑性成形得到的锻件微观组织进行比较,楔横轧锻件整体平均晶粒尺寸更加细小、均匀。     

冷轧过程中组合式支承辊与整体式支承辊性能的比较

为比较四辊冷轧条件下热装组合式支承辊与整体式支承辊的工作性能,将辊套和辊芯进行分段离散,根据工作辊、辊套及辊芯之间的变形协调以及力平衡条件,采用影响函数法基于C语言编程求解组合式支承辊弹性压扁、辊间压力及出口前张力横向分布,研究弯辊力以及窜辊量对组合式支承辊性能的影响,并将其与相同轧制工艺参数条件下的整体式支承辊性能进行比较。结果表明,相同条件下,组合式支承辊的辊间压扁量比整体式支承辊的辊间压扁量减少6%以上,组合式支承辊辊身边部与中部的辊间压力差值比整体式支承辊边部和中部辊间压力差值大0.2kN/mm左右;但当弯辊力及窜辊量较大时,组合式支承辊出口前张力边部与中部差值明显大于整体式支承辊出口前张力边部与中部差值。     

基于Qform的建筑脚手架连接叉锻压工艺模拟

针对高强度、高可靠建筑零件成形较难的问题,分析了建筑脚手架连接叉的成形工艺。运用有限元软件Qform对其锻压中的辊锻成形进行了模拟,得到辊锻成形过程中不同位置处的等效应力、等效应变。分析了不同辊轮转速与辊轮进给速度对连接叉辊锻等效应力的影响。结果表明:连接叉在辊锻过程中,随着辊轮转速增加,等效应变也随着增加;随着辊轮进给速度的增加,等效应变反而逐渐减小。连接叉辊锻过程中锻件等效应力比较均匀,辊轮转速及进给速度对锻件变形影响较大。     

铁路货车钩尾框精密辊锻过程数值模拟

铁路货车钩尾框锻件为异形长轴类锻件,目前采用自由锻工艺制坯,效率低,质量差,大型自动辊锻机精密辊锻是一种优质高效的先进制坯工艺,用于钩尾框制坯有望取得良好的技术经济效益.以刚塑性有限元法为基础,利用Deform-3D软件对铁路货车钩尾框精密辊锻过程进行三维有限元模拟,揭示了钩尾框辊锻变形过程中金属的流动规律,分析了辊锻成形过程中各道次辊锻过程中模具受载荷情况,以及各道次辊锻过程中的辊锻力矩,为钩尾框精密辊锻工艺及模具设计提供了有效的参考依据.     

室兰制作所支承辊制造技术介绍

<正> 日本制钢所(JSW)室兰制作所(以下简称室兰厂)以生产大型铸锻件著称,各类轧辊是其代表性产品.该厂轧辊锻件年产量约占全部锻件年总产量的30%,其中各种冷热轧机支承辊锻件又占轧辊锻件生产总数的三分之一左右.支承辊的规格从小到大,以     

DEFORM模拟支撑辊的锻造

轧机中的关键零件之一支撑辊在轧制设备运行的过程中承受轧辊传来的交变应力。大型支撑辊由大型钢锭锻造而成,但大型钢锭中存在种种缺陷,给支撑辊的质量带来很多问题。针对此问题,采用WHF法能够锻合锻件内部组织缺陷,可改善锻件质量。采用DEFORM软件,模拟WHF法拔长,研究WHF法在锻造拔长过程中对锻件心部的作用。实验研究表明,WHF法在拔长的第3道次时,锻件心部的应力状态由拉应力完全转变为压应力。同时,到第6道次后,锻件心部等效应变达到1.2。通过锻件心部压应力和等效应变值可知,WHF法能够完全破碎锻件内部的组织缺陷,生产出质量合格的支撑辊锻件。     

二重成功签订国内最大支承辊制造合同

近日，二重与五矿营口中板有限公司签订5m宽厚板轧机6件支承辊制造合同。该合同的成功签订，为全面提升集团公司大型辊类锻件，尤其是大型支承辊的制造技术创造了有利条件。     

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.