Energy Losses in Cross Junctions

Energy losses occurring in pipe junctions have been studied for many years. Head loss coefficients (K) are commonly used to characterize losses across elbows, tees, crosses, valves, and other pipe fittings. When accurate values of K are used, the flow rate and corresponding total head at any location in a pipe network can be calculated. While K is well defined for most pipe junctions and fittings, the literature has limited documentations of K for crosses. This study was commissioned to determine K for a wide range of flow combinations in a pipe cross with equal diameter pipes and varied flow combinations. This study provides and innovatively presents over 1,000 experimental values of K for designing and analyzing equal diameter pipe crosses.     

直缝钢管的高频焊接

论述了直缝钢管高频焊接的工作原理与方法,并对影响高频焊接焊缝质量的有关工艺参数进行了分析。     

爆炸焊接过程的能量分析

从金属物理学的观点描述了爆炸焊接的过程 ,由此进行了该过程中的能量分析和能量平衡。     

Welding of Materials for Energy Applications

Materials will play a critical role in power generation from both new and existing plants that rely on coal, nuclear, and oil/gas as energy supplies. High efficiency power plants are currently being designed that will require materials with improved mechanical properties and corrosion resistance under conditions of elevated temperature, stress, and aggressive gaseous environments. Most of these materials will require welding during initial fabrication and plant maintenance. The severe thermal and strain cycles associated with welding can produce large gradients in microstructure and composition within the heat-affected and fusion zones of the weld, and these gradients are commonly accompanied by deleterious changes to properties. Thus, successful use of materials in energy applications hinges on the ability to understand, predict, and control the processing–microstructure–property relations during welding. This article highlights some of the current challenges associated with fusion welding of materials for energy applications.     

3 200 m3高炉炉壳立缝、环缝自动焊接技术

介绍了天钢3 200 m3高炉炉壳自动焊技术和工艺,该工程对焊接设备进行了改造,改变了传统高炉壳体焊接工艺,并在国内首次在高炉壳体结构焊接工作中全面使用立缝、环缝自动焊,保证了工期的按时完成,取得良好的经济与社会效益.     

弧焊机器人焊缝位置的电流检测法

本文介绍了弧焊机器人在进行\     

焊缝金相分析系统的设计与实现

针对实际焊接工艺研究的需要,在对图像处理技术进行探索的基础上,对焊缝金相组织图像处理技术进行了研究,并在Visual C＋＋平台上开发了金相组织图像分析程序。在人机交互下,通过对金相图像进行图像预处理、图像复原、图像分割和图像识别等处理,使数码拍摄的焊缝金相组织图像可以由图像处理技术进行分割并识别,同时程序还完成了焊缝金相组织的微观结构特性参数的统计。这些参数的获得为实际焊接工艺研究提供了重要的试验参数。     

Real Local Losses Estimation for On-Line Emitters Using Empirical and Numerical Procedures

This paper presents a procedure based on a lateral, where the flow rate of all the emitters and the pressure every 10?m were measured. Our goal was to obtain a general formula for directly calculating the local losses of on-line emitters as a function of the number of emitters, the average emitter discharge, and the ratio between the protrusion area and the pipe cross-sectional area. A total friction factor, including the local losses and the Blasius friction factor, was obtained as well. Both approximations accurately predict the local and total losses for the experimental data obtained in an irrigation loop system placed in the Rural Engineering Laboratory. Finally, an estimation of these local losses using a computational fluid dynamics model was carried out by the writers. Our numerical approach accurately predicts the local losses and allows the use of this technique to obtain a better estimation of the local turbulence originated by the emitter’s connection.     

平板垂直接管构件环形焊缝变形的控制

针对焦炉炉顶水封盖底座的平板垂直封闭环形多道焊焊接形式,制定了有效的措施和焊接工艺,圆满完成了构件的制作,成功控制了焊接变形,保证了产品质量。     

Simulation of Heat Flow During the Welding of Thin Plates

Based on the finite difference method and the enthalpy model of Shamsundar, a computer model was developed to describe the steady state, two-dimensional heat flow during the welding of thin plates. In order to allow accurate computations of the weld pool configuration, the size of the mushy zone and the temperature distribution near the heat source, a grid mesh of variable spacings was used. The heat of fusion, the size and distribution of the heat source, the temperature dependence of thermal properties, the heat conduction in the welding direction and the surface heat loss during welding were considered. The model was first checked with Rosenthal’s analytical solution of welding heat flow using pure aluminum for examples. Experimental results of 6061 aluminum, including the width of the fusion zone and the thermal cycles at positions in both the fusion and the heat affected zones, were then compared with the calculated results of the heat flow model. The agreement was very good. Finally, in order to demonstrate systematically the quantitative effect of welding parameters such as the heat input, the welding speed and the preheating of the workpiece, a series of computations were made based upon 6061 aluminum.     

激光拼焊焊缝显微组织及精细结构分析

将厚度为1.2 mm和0.8 mm的低碳冷轧汽车薄板通过激光拼焊工艺焊接成一个整体,利用光学金相显微镜和透射电子显微镜研究了焊缝处的显微组织和精细结构,并利用显微硬度计连续地测量了焊缝处的显微硬值。结果表明,该钢激光拼焊缝焊处组织为通过块型转变形成的块型铁素体,其位错密度高于多边形铁素体,块型铁素体硬度介于先共析铁素体与贝氏体之间。     

A Three-Stage Mechanistic Model for Solidification Cracking During Welding of Steel

Metallurgical and Materials Transactions A - A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of...     

On the Occurrence of Liquation During Linear Friction Welding of Ni-Based Superalloys

A combination of experimental and analytical methods was used to study the possible occurrence of liquation during LFW of the newly developed AD730^TM Ni-based superalloy. LFWed joints were produced using a semi-industrial size facility and the interfaces of the joints as well as the ejected flash were examined using optical and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Physical simulation of the LFW thermal cycle, using thermomechanical simulator Gleeble™ 3800, showed that incipient melting started from 1473 K (1200 °C). The analytical model, calibrated by experiments, predicted that the highest temperature of the interface was about 1523 K (1250 °C). The constitutive equations based on lattice and pipe diffusion models were developed to quantify the self-diffusivity of the elements and control the extent of liquation by considering the effect of LFW process parameters. Analytical results show that the application of compressive stresses during LFW results in 25 times increase in the diffusion of Ni atoms at the weld interface. Therefore, no presence of re-solidified phases, i.e., occurrence of liquation, was observed in the microstructure of the weld zone or the flash in the present study. Based on the obtained results, a methodology was developed for designing the optimum pressure above which no liquation, and hence cracking, will be observable.

     

怎样识别压力容器焊缝超声波探伤中变型波

用压力容器对接焊缝超声波探伤过程中。在一定条件下会产生变型干扰波，很容易被误判为缺陷波。通过分析变型波的产生机理和总结实际探伤经验，明确了这种假设缺陷回渡产生的原因及特点。对压力容器焊缝超声波探伤有参考意义。     

Grain Structure Development During Friction Stir Welding of Single-Crystal Austenitic Stainless Steel

The high-resolution electron backscatter diffraction (EBSD) technique was used to study the grain boundary development and texture evolution during friction stir welding (FSW) in a single-crystal austenitic stainless steel. Strain-induced crystal rotations were found to be induced by simple shear deformation. With the crystal rotations, the single-crystal structure was broken up into a fine-grained polycrystalline aggregate in the stir zone. This process was deduced to be governed by continuous and discontinuous recrystallizations operating during the FSW process. The final texture which evolved in the stir zone was dominated by $ A/\bar{A}\left\{ {111} \right\} \, \langle 110 \rangle $ ideal simple shear orientations.     

Mass Transfer of Nickel-Base Alloy Covered Electrode During Shielded Metal Arc Welding

The mass transfer in shielded metal arc welding of a group of nickel-base alloy covered electrodes according to AWS specification A5.11-A5.11M was investigated by directly measuring their deposited metal compositions. The results indicate that the chromium mass-transfer coefficient is in the range of 86 to 94 pct, iron in the range of 82 to 89 pct, manganese in the range of 60 to 73 pct, niobium in the range of 44 to 56 pct, and silicon in the range of 41 to 47 pct. The metal mass-transfer coefficient from the core wire is markedly higher than that from the coating. The basicity of slag, the metal contents in the flux coating, and the welding current together affect the mass transfer. As the basicity of slag increases, the mass-transfer coefficients of Mn, Fe, and Cr slightly increase, but those of Nb and Si decrease significantly. As the niobium and manganese contents increase in the coating, their mass-transfer coefficients also increase. However, iron is different. The content of iron in the coating in the range of 8 to 20 wt pct results in the optimal effective mass transfer. The lower, or higher, iron content leads to lower mass-transfer coefficient. As the welding current increases, the mass-transfer coefficients of niobium and manganese decrease, but chromium and silicon increase. Iron has the lowest mass-transfer coefficient when welded under the operating current of 100 A.     

氧化铝种分槽体横环缝自动化焊接的分析

通过对大型氧化铝种分槽主体建设施工现场的研究,分析了氧化铝种分槽体自动化焊接施工的特性,开发研制成功了罐体立缝高效气电立焊机和横环缝埋弧自动焊接操作机。通过几年来在三十几座氧化铝种分槽主体施工工程中的应用,其焊接技术先进,焊接效率高,焊接质量好,极大地减轻了工人的劳动强度,降低了综合成本,有广阔的前景。     

Microstructural Evolution During Friction Stir Welding of Mild Steel and Ni-Based Alloy 625

Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW.