LD10随焊预拉伸作用位置的有限元分析

对于铝合金的焊接其焊后残余应力导致的焊接变形,尤其对于薄板的焊接其焊接变形问题更为严重。本文运用MSC.Marc大型有限元模拟软件对LD10铝合金的预拉伸工艺进行三维模拟,为优化铝合金预拉伸工艺的工艺参数,提供了理论依据和指导。结果说明:在弹性应力范围内,随着预应力作用范围的增大,试件的纵向残余拉应力峰值、纵向残余弹、塑性变形量均逐渐减小。分析认为,预拉伸应力部分抵消了焊接区因局部加热而导致的压缩塑性变形,减小了焊接残余应力,从而起到控制薄板焊接失稳变形的目的。

拉锻式摩擦塞焊的热力耦合解析模型和试验验证

为快速得到拉锻式摩擦塞焊的焊接工艺参数,对焊接过程进行预测,建立了摩擦塞焊过程的扭矩、轴向力、功率和能量等指标的力学模型和热力耦合解析模型。模型的输入量为焊接塞棒的几何参数、材料属性、焊接转速和进给速度,输出量为焊接过程的扭矩、轴向力、功率和能量等。在自主设计的拉锻式摩擦塞焊设备上进行了焊接试验。通过将试验数据的输入和输出指标与理论模型值进行对比分析,验证了理论解析模型的可行性。

不等厚拼焊管轴向压缩变形的数值模拟研究

采用两种焊缝建模方法对拼焊管的轴向变形进行了数值模拟和实验研究,分析了不同建模方法和料厚比对拼焊管轴向变形的影响。研究结果表明,随着料厚比的增加,差厚同材拼焊管和传统等厚管的载荷-位移曲线形貌、折叠铰数量和折叠波长存在差别;焊缝位置和料厚比适当的拼焊管轴向力学性能优于等厚管。正确估算不等厚紧排折叠铰的折叠波长,设计适当的料厚比和焊缝位置,对于差厚同材拼焊型吸能管结构设计具有较为重要的意义。

螺旋叶片组合冷拉成型法

对螺旋叶片进行了分析 ,把螺旋叶片焊接组合起来 ,旋加外力 ,冷拉成型。

手工烙铁焊在表贴元器件焊接中的应用

本文主要介绍了3种手工烙铁焊接表面贴装元器件方法,以便于电子专业的学生或电子设计制作爱好者了解、学习。

压力容器组合焊缝焊接工艺评定的理解和实施

本文介绍了对JB4708－92《钢制压力容器焊接工艺评定》组合焊缝焊接工艺评定规定的理解和体会，对如何判别坡口形式和尺寸是否类同，如何采用与焊件接头坡口形式和尺寸类同的对接焊缝试件进行评定，如何选用组合焊缝试件，如何进行插入式接管的组合焊接工艺评定等具体问题作了讨论。

核电安装工程焊接组织体系初探

民用核电安装工程在我国已开始起步，由于核电安全的重要性，对整个核电安装工程质量保证体系提出了更高更严的要求，本文从焊接工程的角度出发，阐述了施工管理和质量保证体系的基本要求和内容。

Effect of brazing temperature on microstructure and tensile strength ofγ-TiAl joint vacuum brazed with micro-nano Ti−Cu−Ni−Nb−Al−Hf filler

A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220°C for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180°C possess three interfacial layers and mainly consist ofα2-Ti3Al,τ3-Al3NiTi2 and Ti2Ni,but the brazing seams are no longer layered and Ti2Ni is completely replaced by the uniformly distributedτ3-Al3NiTi2 at 1200 and 1220°C due to the destruction ofα2-Ti3Al barrier layer.This transformation at 1200°C obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.

超大直径超大壁厚渣油加氢反应器的国产化研制

针对渣油加氢反应器操作条件苛刻、制造过程复杂、技术难度大、价格昂贵的特点,介绍了目前国内最大的渣油加氢反应器的设计和制造情况。从结构设计、材料选择与制造以及焊接工艺等方面阐述了超大直径、超大壁厚加氢反应器国产化攻关制造的关键技术。通过锻件性能分析、焊接性能分析以及无损检测,对渣油加氢反应器质量进行了检测,结果表明:产品锻件的成分、力学性能、金相组织、非金属夹杂物、抗回火脆化倾向等各项指标均满足设计技术条件要求;产品焊接试板的力学性能、焊缝金属抗回火脆化倾向、焊缝及内壁堆焊层的成分、无损检测等结果均满足设计技术条件要求;产品满足装置生产的需要。

反变形工艺技术应用实例

介绍了反变形焊接工艺在反轨式板结构龙门吊主梁和工字钢构件焊接中的应用

Effects of weld reinforcement on tensile behavior and mechanical properties of 2219-T87 aluminum alloy TIG welded joints

Tungsten inert gas （TIG） welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their manufacturing and strength evaluation. Experimental and numerical simulation methods were used to investigate the effects of weld toe shape and weld toe position on the tensile behavior and mechanical properties of these joints. The simulation results indicated that the relative difference in elongation could be as large as 96.9% caused by the difference in weld toe shape. The joints with weld toes located in the weld metal or in the partially melted zone （PMZ） exhibited larger elongation than joints with weld toes located at the juncture of the weld metal and the PMZ.

Quasi-static and dynamic tensile behaviors in electron beam welded Ti-6Al-4V alloy

The quasi-static and dynamic tensile behaviors in electron beam welded（EBW） Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system（MTS） and reconstructive Hopkinson bars apparatus.The microstructures of the base metal（BM） and the welded metal（WM） were observed with optical microscope.The fracture characteristics of the BM and WM were characterized with scanning electronic microscope.In Ti-6Al-4V alloy joint,the flow stress of WM is higher than that of BM,while the fracture strain of WM is less than that of BM at strain rates of 103 and 10-3 s-1,respectively.The fracture strain of WM has apparent improvement when the strain rate rises from 10-3 to 103 s-1,while the fracture strain of BM almost has no change.At the same time,the fracture mode of WM alters from brittle to ductile fracture,which causes improvement of the fracture strain of WM.

Microstructural evolution and mechanical properties of TIG welded superalloy GH625

The tungsten inert gas welding（TIG） technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the welded joint were investigated systematically. The results indicated that the welded seam was of austenite dendrite crystal structure and no obvious heat affected zone（HAZ） was observed. A number of precipitated δ phases with homogeneous distribution were observed in the interdendritic region of the weld fusion zone. The abnormal phenomenon observed in the weld fusion zone of GH625, i.e., higher hardness and larger grain size compared with the base metal, may be attributed to the precipitated δ phase in the weld fusion zone. The higher tensile strength in the base metal was mainly attributed to the presence of more contents of fine grains and twin boundaries, while the lower elongation in the welded joint was mainly owing to the precipitated δ phase.

Mechanical properties and wear resistance of aluminum composite welded by electron beam

The welding property of TiB2/ZL101 composite was investigated using electron beam（EB） welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing parameters and scanning rate.The reinforcement particles TiB2 distributed homogeneously in welding seam without any segregation.The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal.Wear resistance of welding seam is improved greatly compared with base metal.The results show that the TiB2/ZL101 composite can be successfully welded by EB technology.

Effect of axial force on microstructure and tensile properties of friction stir welded AZ61A magnesium alloy

The influences of axial force on tensile properties of friction stir welded AZ61A magnesium alloy were studied. Five different values of axial forces ranging from 3 to 7 kN were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the stir zone microstructure and hardness. From this investigation, it is found that the joint fabricated with an axial force of 5 kN exhibits superior tensile properties compared to other joints. The formation of finer grains in the stir zone and higher hardness of the stir zone are the main reasons for the superior tensile properties of these joints.

Tensile resistance,microstructures of intermetallic compounds,and fracture modes of welded steel/aluminum joints produced using laser lap welding

The joining of DP780 steel to Al5052 was conducted by laser lap welding,in which the metal vapor and spatters were monitored by a high-speed camera.A universal testing machine was used to test the mechanical properties of the welded joints,and the changing law of lap tensile resistance with the laser welding parameters was analyzed.Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure,respectively.Three different intermetallic compounds(IMCs)phases,i.e.banded Fe2Al5,FeAl2 and needle-like FeAl3 were generated at the steel/Al interface on microscopic observation.The aim of this research is to investigate the relationship among the lap tensile resistance,the welding parameters and the failure mode under different energy densities.Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input.The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface,respectively.And both of the two failure modes are brittle fractures.Additionally,cracks appeared at the fracture interface,and needle-like particle clusters were found in the fracture microstructure.

Effect of pulsed current on temperature distribution,weld bead profiles and characteristics of gas tungsten arc welded aluminum alloy joints

Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.

Effect of welding processes on AA2219 aluminium alloy joint properties

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.

Effects of weld penetration on tensile properties of 2219 aluminum alloy TIG-welded joints

Numerical simulation and experimental methods were used to investigate the effects of weld penetration on tensile properties of 2219 aluminum alloy tungsten inert gas(TIG)welded joints.The results show that when other geometric parameters are consistent,within a certain range,the deeper the weld penetration of the capping weld is,the lower the tensile strength of the j oint is.The deeper weld penetration of the capping weld can cause the more concentrated stress at the weld toe and the joint is more likely to crack accordingly.Based on necessary assumptions,a model for analyzing the mathematical relation between the weld penetration of the capping weld and the tensile strength of the joint was proposed to validate the experimental results. The decrease of weld penetration of capping weld can be controlled by decreasing welding current,helium content or increasing welding voltage.