长输管道安装焊接方法现状及展望

描述了当前长输管道安装焊接涉及的焊条电弧焊、手工钨极氩弧焊、自保护药芯焊丝半自动焊、STT技术气体保护实心焊丝半自动焊、RMD技术气保护金属粉芯焊丝半自动焊、单焊炬熔化极活性气体保护自动焊、双焊炬活性气体保护自动焊、管道环缝自动内焊机根焊、CMT技术气保护实心焊丝自动焊、埋弧自动焊、闪光接触对焊等焊接方法的特点及应用情况,并对长输管道未来会应用的双丝焊接方法、激光-电弧复合焊焊接方法、多焊炬自动焊外焊方法进行了介绍,藉此为广大从事长输管道施工技术人员选用高效、高质量的安装焊接方法提供一定的技术支持,为从事焊接技术开发的科研人员提供参考.     

直径1.4mm焊丝管道自动外焊焊接工艺

国内外大口径长输管道自动焊焊接施工中普遍使用0.9 mm焊丝内焊,1.0 mm焊丝热焊及填充、盖面焊,焊接效率偏低。针对性地进行大直径焊丝管道全自动焊焊接技术研究,实现了管道全自动高效焊接。介绍内焊机根焊+直径1.4mm气体保护焊丝管道自动外焊的成熟工艺。     

大口径长输管道自动焊施工技术分析

大口径长输管道具有管壁厚、压力高等特点，传统焊接方式在该管道焊接中存在一定的难度，而且难以保证焊接效率。因此自动焊施工方式的应用愈发广泛，可以保证焊接的速度和质量，解决传统焊接问题。本文主要对大口径长输管道自动焊施工的技术进行分析，探究更有效的焊接策略，以供参考。     

管道实心焊丝自动焊弧坑裂纹的产生及预防

随着石油天然气长输管道朝着高钢级、大口径方向的发展,管道自动焊施工成为长输管道施工中主要的焊接作业方式,但对于不同钢级、不同管径、不同焊材厂家和不同自动焊设备厂家来说,自动焊工艺参数的选择、控制和优化至关重要。依托中俄东线天然气管道工程项目,进行大量的管道自动焊工艺焊接试验,分析长输管道实心焊丝自动焊收弧处裂纹产生的原因及危害,并针对管道局研究院CPP900自动焊设备焊接过程中出现的收弧裂纹进行工艺参数优化,通过控制自动焊电源TPS3200的相关参数设定和试验有效解决了弧坑裂纹,为现场焊接施工提供了质量保障。     

自动焊技术在长输管道焊接中的应用

长输管道建设中的焊接环节是决定管道建设速度和使用寿命的重要环节之一。目前国内长输管道的环焊缝焊接在传统焊条电弧焊的基础上,吸收引进了药芯半自动焊和全自动焊技术。本文在此基础上充分分析介绍了自动焊技术在我国长输管道建设中的应用。     

气保药芯焊丝全位置自动焊技术应用与质量控制

管道自动焊技术以其焊缝力学性能优良、生产效率高等特点,已经在我国长输管道焊接施工中得到广泛应用,我国大口径长输管道建设中基本采用实心焊丝下向自动焊技术,但受限于地形和坡口加工精度,尚不能得到全面应用。而气保药芯上向自动焊技术以工艺参数执行过程中人为因素影响少、地形适应性较强、管径适用范围大、对坡口加工精度要求低及接头力学性能良好等优点,逐渐受到建设者的青睐。文中介绍了气保药芯焊丝自动焊技术原理、工艺参数选择、质量控制、自动焊设备及技术的工程应用,为管道自动焊技术的规模应用提供了一个选择。     

长输管道自动焊接设备及技术发展

随着社会技术进步和人类对石油和天然气需求量的急剧增加,长输管道在向着大口径、长距离、高压力、高钢级方向发展,焊接技术及相关的设备、材料性能也在同步提高,与之相适应的管道焊接技术也在发生着巨大的变化。管材钢级从X42提高到X80;焊接材料从纤维素焊条到自保护药芯、金属粉芯、实心等各种焊丝;焊接方法从手工上向焊到手工下向焊,到药芯自保护半自动焊,再到气保护半自动焊、自动焊,管道焊接技术日趋成熟。结合长输管道施工特点,在分析国内外管道焊接技术差异的基础上,提出我国现阶段长输管道焊接技术发展的建议。     

长输油气管道高强度管线钢管现场焊接技术

介绍了我国长输油气管道建设用管线钢管及现场焊接技术的发展和应用现状,指出高强度管线钢管的焊接技术难点和现场焊接技术特点,并从焊接方法选择、管道自动焊技术应用和无损检测技术三方面对比分析了国内外管道现场焊接技术的差异,提出我国今后管道现场焊接技术的发展趋势。自保护药芯焊丝半自动焊和低氢焊条手工焊工艺仍将是管道建设的可选择方法,但随着管道建设用钢管强度等级的不断提高,管径和壁厚的不断增大,管道自动焊技术的应用将会越来越广泛。     

管道焊接技术的发展及对未来的展望

焊接是长输管道安装的主要技术,介绍了在近几年特别是在西气东输工程中长输管道手工焊、半自动焊、全自动焊焊接技术的发展及未来的长输管道焊接技术发展趋势.     

燃气长输管道施工中的半自动向下立焊工艺研究

为优化燃气长输管道施工,采用半自动向下立焊工艺不仅可以提高管道施工的工作效率还可以提升燃气管道工程的整体质量,本文重点研究燃气长输管道施工中的半自动向下立焊工艺,实现管道焊接施工顺利运行,为相关工程提供参考。     

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).     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.