核电站TIG全位置自动焊打底工艺分析

TIG全位置自动焊工艺是一种先进的焊接生产技术,受人为因素影响较小,且自动化程度较高,实用性强。对于此工艺而言,打底焊接是其中的关键技术难题。结合国防科工委核能开发科研项目《核岛辅助管道自动化焊接应用技术研究》中核心子课题——TIG全自动焊工艺,对其打底焊接工艺进行较为详细的分析和研究。介绍了TIG全自动焊中打底焊接工艺的影响因素——先决因素和工艺因素,针对先决因素提出解决途径,针对工艺因素找出其内在规律。     

管道全位置焊接参数控制系统

众多焊接参数的合理匹配和有效控制是管道环缝全位置焊接过程自动化的难题之一。结合路径示教、参数匹配及参数控制等技术，建立了管道环缝全位置焊接过程自动控制系统，并介绍了其工作原理、系统构成和软件设计。该系统能根据焊接位置自动匹配焊接电流、电弧电压、焊接速度以及焊炬摆动的速度和幅度等参数，并通过调节送丝速度实现了焊接电流的PID控制，通过调整焊炬高度实现了电弧长度的模糊控制。该系统还具有离线编程、路径示教和记忆跟踪等功能。将该系统用于非旋转管道环缝全位置焊接过程，实现了打底、填充和盖面焊接的自动控制。结果表明，实际焊接参数与预设值吻合良好，焊缝成形稳定。     

管道预制焊接机器人的研究

研究了一种管道焊接机器人系统,采用激光视觉传感,在两个维度上完成管道焊缝的识别与跟踪,并在焊接第一道焊缝(打底焊)的同时,利用机器人记忆功能完成管道焊缝示教过程,简化了焊接操作过程.试验结果验证该焊接机器人系统满足管道自动化焊接的需求.     

GMAW管道打底焊视觉监控系统研究

针对熔化极气体保护焊(GMAW)打底焊特点,利用CCD相机和复合滤光技术组成的光学系统,实时获取焊接图像,采用熔池检测、焊丝提取和焊缝跟踪算法,实时处理焊接图像,获取精确的焊缝边缘位置和焊缝宽度完成焊接,统计焊丝中心位置,并计算该位置与焊缝中心位置偏差,控制微调电机,完成焊丝中心纠偏.开发了一套完整的视觉监控系统,实验结果表明,系统能很好地完成GMAW管道打底焊.     

基于被动光的MAG管道打底焊焊缝边缘提取方法

焊缝跟踪是实现焊接自动化的前提条件.间隙的变化会影响基于熔化极气体保护焊（metal active gas,MAG）的管道自动打底焊的焊接质量,为此设计了基于电荷耦合器件（charge-coupled device,CCD）视觉传感的MAG打底焊焊接过程监控系统.但从CCD获取的焊接过程的图像通常具有很大噪声,亟需设计...     

华恒焊接-亮剑管道工程解决方案

华恒管道工程的核心竞争力:TIG和MIG的自动焊打底工艺和具有多项专利技术的管道自动焊接系统。超过15年的TIG焊接工艺积累,无论是全位置焊接还是工件旋转焊接,TIG焊接对我们来说小菜一碟;华恒独特的弧长控制+横摆控制技术,让你感觉焊缝质量控制如此简单。     

焊接机器人管道全自动打底焊研究

采用自主研发的新型管道全位置焊接机器人,结合CMT焊接电源,研究了一种焊接机器人管道全自动打底焊方法.打底焊整圈一次完成,所焊焊道只有一个接头.试验表明,该打底焊方法焊接速度快,焊缝成形美观,背面成形良好,实现了管道全自动打底焊单面焊双面成形.     

PWT-DWS.03全自动管道焊接技术

文中介绍了意大利PWT全自动管道焊接最新的DWS.03焊接系统的组成、特点、原理。通过对该系统的研究、试验,找出了影响未焊透、未熔合、烧穿、焊缝尖角等焊接缺陷产生的工艺原因,并且通过进行反复调试试验,得出了采用DWS.03焊接系统进行管道全自动焊接的理想焊接工艺。     

海洋平台管道自动焊接工艺研究

针对海洋平台运维工程管线厚壁管道对接接头的机器人自动焊接生产线要求,分别采用K-TIG、高频TIG焊及直流TIG焊等打底焊工艺,以及混氩保护气体条件下的脉冲MAG填充盖面焊工艺,对生产线的焊接工艺进行了工艺适应性研究,并按照美标ASME BPVC相关要求对焊接试验中的焊件进行了焊缝力学性能和X射线探伤,制定出一套可用于实际焊接生产焊接生产工艺参数,为管线管道的自动化焊接生产奠定了工艺基础。     

非旋转管道环缝焊接自动控制技术

建立了非旋转管道环缝焊接自动控制系统,并介绍了其系统结构和工作原理。该系统可控制焊炬沿三个方向运动,并具有记忆跟踪功能。为满足全位置焊接工艺的要求。焊接电流、电弧电压、焊接速度及焊炬摆动的速度和摆幅等参数能根据焊接位置的不同自动调节。实验表明,该系统运行可靠,能有效提高生产效率,很好地满足了管道环缝打底、填充和盖面焊接的需要,具有重要的工程应用前景。     

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.