SQ460FRW抗震耐蚀耐火钢气保焊焊接技术

通过焊接性试验对28 mm厚的新钢种SQ460FRW抗震耐蚀耐火钢进行焊接工艺研究。改善了焊接坡口,对比纯CO_2和混合气体保护下对接平焊的差异,对气保焊对接接头平焊、立焊、横焊、仰焊和十字接头横焊、立焊进行了工艺评定。在十字接头中应用了双面双弧单熔池同步同向焊接、高速脉冲压缩电弧技术、双面K型坡口35°+4 mm间隙等焊接方法,焊缝无损检测、力学性能检测、宏观金相、冲击试验、微观金相组织观察等各项检测内容均合格,可用于指导后续新钢种的实际应用。     

平仰位置的9%Ni钢双面氩弧焊打底工艺及接头性能分析

针对9%Ni钢仰焊位置的焊接工艺和外观成形差的问题,采用双面氩弧焊工艺打底后,分别采用氩弧焊和焊条电弧焊进行平焊位置的填充焊接。试验结果表明,两种不同填充焊接方法的接头横向拉伸均达到母材抗拉强度的下限值,实现了等强匹配,且在-196℃时低温冲击韧性良好。证明双面氩弧焊打底工艺能将仰焊位置转换为平焊进行焊接,有利于保证9%Ni钢平仰位置的焊接质量和焊缝外观成形。     

双丝窄间隙焊接工艺参数对焊缝成形的影响

通过工艺试验,研究了双丝共熔池窄间隙焊焊丝与侧壁间距、双丝前后间距和双丝倾角3个工艺参数对焊缝成形的影响.结果表明,焊丝与侧壁间距减小,侧壁熔深和表面下凹增加;沿焊接方向双丝倾角为零时,侧壁熔深和表面下凹达到最大值;而在电弧和熔池热量的共同作用下,双丝前后间距增大,侧壁熔深和表面下凹先增大,后减小,在5～10 mm内达到最大值.在不形成指状熔深时,这3个参数对焊缝熔深影响不大.采用I形坡口会出现底部未熔合,调节这3个参数不能消除未熔合现象.     

铝合金非熔化极直流正接氦弧焊氧化膜撕裂机理

采用高速摄影观察了不同气体流量下铝合金非熔化极直流正接氦弧焊焊接过程中电弧的形态及氧化膜撕裂过程. 观察测量结果表明,在试验参数范围内氦气流量的增加减弱了氧化膜的撕裂程度,但提升了焊缝深宽比及电弧能量效率. 氦弧焊阳极产热功率的提升削弱了氧化膜之间的化学键强度,产生了氧化膜撕裂现象. 在静力学平衡方程基础上推导得出了熔池液面与电极所在平面交线的微分方程,解释了熔池液面下凹程度随氦气流量增加而增加的原因,同时熔池中心指向熔池边缘表面张力也随气体流量增加而减小,两种因素共同作用使氧化膜撕裂程度随气体流量增加而减弱.     

交变磁场作用下金属液面的变形和波动行为

采用低熔点Sn-32%Pb-52%Bi合金模拟钢液,研究交变磁场作用下金属熔池液面的波动和变形行为。结果表明:交变磁场会使金属液面发生弧形变形,液面一直处于波动状态;熔池在三相点附近形成汇聚撞击的两个回流区,导致液面上三相点附近的波动最剧烈,易造成表面卷渣;增加线圈电流强度,液面变形增大,波动加剧;当熔池外壁面的磁感应强度达到约50mT时,液面的波动幅度达到约±3mm,应有一个合理的电流强度;适当增加频率可减小电磁力对自由表面波动的影响范围,有利于增大弯月面变形和减小液面波动,频率控制在30kHz左右较适宜;液面位于线圈中心高度附近时,弯月面变形较大,液面波动较剧烈,初始液面控制在线圈高度中心有利于节能。波动规律可解释电磁软接触连铸中铸坯表面振痕随电流强度大小的变化规律。     

电弧力对TIG焊接熔池液面形态影响的数值模拟

在建立TIG焊接熔池液面三维形状模型基础上,对电弧力作用于熔池液面进行了表征,采用Surface Evolver有限元分析软件进行数值模拟,研究了电弧力对TIG焊接熔池液面三维形态的影响.得到了有电弧作用时,熔池的三维形态和熔池各液面参数随电弧力大小变化的规律.结果表明,在熔池形状一定时(正面、背面熔化区域半径和板厚一定),电弧力的作用深度增加会引起熔池上、下液面和固液面的表面积均增加,其中电弧力的大小对TIG焊接熔池的上液面影响程度大于下液面.这些分析结果为探讨TIG焊接熔池的各类问题提供了基础.     

双面激光打底焊根部熔合模拟及组织演变分析

提出了一种双面摆动激光错位同步焊接新工艺,用于厚板大钝边的自熔打底焊接,开展了不同激光间距下打底焊接试验,建立了双面激光打底焊接有限元模型,获取熔池形貌,并与试验焊缝形貌进行对比验证,在此基础上分析了接头粗晶区的焊接热过程及组织演变.结果表明,双面摆动激光错位同步焊接可以实现大钝边打底焊缝的良好熔透成形;与单面激光打底焊接相比,双面激光焊接粗晶区800 ~ 500 ℃的冷却时间(t_8/5)和800 ~ 300 ℃的冷却时间(t_8/3)延长;当激光间距不低于50 mm时,粗晶区发生重新奥氏体化. 单面摆动激光焊接粗晶区的显微组织为板条马氏体,双面摆动激光焊接粗晶区的显微组织为板条马氏体和板条贝氏体,而且随着激光间距的缩短,板条贝氏体含量逐渐增加;双面摆动激光错位同步焊接利于改善接头性能,降低冷裂倾向.     

管线钢中厚板激光诱导电弧全位置焊接工艺与性能

采用低功率脉冲激光诱导MAG电弧复合热源新工艺,对板厚为16 mm的X65管线钢进行了全位置单面焊双面自由成形及受力分析研究。试验结果表明:热输入是影响全位置打底焊内凹缺陷产生的主要原因,热输入的增大使得熔池体积增大,熔池所受重力增大,流动趋势增强,导致打底焊焊缝内凹缺陷变大;通过调控焊接电流、焊接速度以及焊枪倾角匹配,可促进熔池受力平衡并减弱熔池流动,激光对于电弧的诱导作用使得单道熔深达到6 mm的同时获得良好背面成形;不同位置焊接接头拉伸试验均断裂在母材,抗拉强度与母材的相当;焊缝区冲击吸收功为母材的82%,热影响区冲击吸收功却高于母材的。     

焊条电弧焊操作"基础四法"

焊条电弧焊“基础四法”概括了四种不同位置试板单面焊双面成形断弧焊操作技术及运条方式,每种焊接位置的操作仅对应一字,从而达到易懂易记、印象深刻的目的。 1“基础四法”操作 (本文以板状试件为例 )　　(1)平焊位——点 　　“点”,即“两点击穿焊法”。平焊的打底焊时,焊条在坡口根部一侧位置引弧,钝边熔化后划向另一侧,待另一侧钝边熔化并形成一个整体熔池后灭弧,此为第一“点”,也是焊道的起点;当熔池未完全凝固时,在前一个熔池灭弧处,压着该熔池的 2/3重新引弧,熔化两侧钝边,观察熔孔并听到穿透的弧声,形成一个完整清…     

自冲铆接凹模损伤对铆接质量的影响

采用了试验结合有限元仿真的方法,对自冲铆接(Self-Piercing Riveting,SPR)设备中的重要部件凹模出现的不同程度的损伤情况可能对SPR接头质量产生的影响进行了试验研究。对凹模的受损情况进行统计分类,根据凹模的受损程度将凹模分为早期受损、中前期受损等5个级别。使用不同受损程度的凹模对厚度为1. 5 mm的A6111铝板进行自冲铆接,测量铆接接头的外观质量与接头剖面几何参数。通过拉伸-剥离仿真试验,探究凹模断裂损伤对SPR铆接接头的连接质量的影响。试验结果表明:凹模损伤会对接头表面外观质量造成损伤,并且会随着凹模损伤程度的增加而增大;凹模没有发生断裂时,凹模损伤对接头剖面的几何参数不会产生太大影响;凹模发生断裂,会降低接头的连接质量。     

Arc force and shapes with high-frequency pulsed-arc welding

Arc plasma is the source of heat and force for molten pool with dynamics fluid and convections. The arc force is studied with shape surveillance and force measurement during pulsed welding process. The results indicated that the average force increased by 42–57%. And the pressures were 322?Pa (conventional welding), 409 Pa and 517?Pa (pulsed welding). Imaging process is carried out for energy distribution analysis. The core region ratio increased up to 51%, compared with 43.7% by conventional welding. The arc pressure derivation was produced and the error was discussed. The increased arc force happens with arc constriction during pulsed welding. It is supposed to create surface depression of molten pool, enhance the fluidity and improve the heat convections.     

基于熔池受力的全位置STT打底焊分段工艺

油气管道在全位置焊接时通常按照固定角度机械化地进行分段,此过程中,熔池容易发生失稳流淌而导致焊缝成形不良。文中对管道全位置焊接过程中的熔池受力进行了分析,建立了一种基于熔池径向力变化的新型分段工艺,以解决全位置焊接时管道内、外壁成形不良的问题。通过对220 mm×10 mm×400 mm的X70管线钢采用STT打底焊试验发现,该分段工艺抑制全位置焊接时的熔池失稳流淌问题有良好效果,且内壁成形更加平滑美观,对于管道自动焊接过程中的分段问题具有一定的参考价值。     

Microstructural and mechanical characteristics of laser welding of Ti6Al4V and lead metal

Titanium alloy Ti6Al4V and lead metal were welded using a continuous wave Nd:YAG laser. The influences of laser power, scanning velocity, and laser beam offset on weld morphology were investigated. Microstructure, chemical composition and mechanical properties of the joints were evaluated. Experimental results showed that fusion weld formed at the upper part of the weld and brazing weld with solder of Pb formed at the lower part of the weld under appropriate process condition. Interfaces were formed between mixed fusion zone and liquid lead zone in molten pool during laser welding of Ti6Al4V and lead. Reasons for interface formation may be different driving force of various regions in molten pool, and the miscibility gap of Ti and Pb binary system. Ti-Pb intermetallic compound Ti₄Pb was detected at the fusion weld zone, which made the microhardness of the weld seam was higher than that of the base materials. The strength of the joint was at least equal to or larger than that of lead base material.     

Porosity and microstructure in pulsed Nd:YAG laser welded Ti6Al4V sheet

The overlapping factor of pulsed laser welding is used to help understand the correlation between welding parameters and the quality of Ti6Al4V welded joints. The number of porosity decreases with the increase in overlapping factor, and the welded joints are almost completely free of porosity when overlapping factor is greater than 75%. This can be attributed to the fact that the remelted volume of the spot region increases with the increase of overlapping factor, which assists porosity formed in the previous pulse wave in escaping from molten pool formed by the subsequent pulse. With the increase of overlapping factor, the weld microstructure becomes much coarser and the width of the fully transformed region of heat affected zone increases, which reduces the microstructure gradient and microhardness gradient from the fusion zone to heat affected zone. A method to evaluate the porosity susceptibility of a specific welding condition prior to actual welding process is presented.     

Numerical analysis of flow-thermal coupling in micro-plasma welding pool of thin-wall part

The formed characteristics of thin-wall part is studied when it is in the process of MPAW. Finite element method is used to simulate the temperature field coupling flow field in the welding of thin-wall part. It is found that because of the obvious effect of heat accumulation in cross-section,where the distribution of temperature field area presents trapezoidal inverted approximately in the molten pool and the non-molten pool area presents level. The surface tension,the electromagnetic force and buoyancy are considered for analyzing the effects on the fluid flow of welding-pool. It can be obtained that the surface tension is the main driving force in the welding pool,which is far greater than electromagnetic force and buoyancy.     

高强铝合金双脉冲VPPA焊缝成形机理

建立双脉冲VPPA(variable polarity plasma arc)焊接系统,进行7A52高强铝合金双脉冲VPPA焊接工艺试验,研究低频脉冲调制叠加高频脉冲对VPPA焊接过程中焊缝成形和焊缝力学性能的影响. 结果表明,低频脉冲周期性振荡液态熔池,可获得表面饱满的鱼鳞纹焊缝;高频脉冲使电弧更为集中,有效地提高了电弧能量密度,穿透力加强;双脉冲耦合振荡加强了对熔池的搅动作用细化了铝合金焊缝晶粒. 焊接接头抗拉强度达到384.13 MPa,相比VPPA焊接接头强度提高了10.21%左右;焊接接头断面收缩率和断后伸长率均有一定程度的提高. 铝合金双脉冲VPPA焊接工艺提高了焊接接头力学性能.     

A study on V-groove GMAW for various welding positions

This study performed three-dimensional transient numerical simulations using the volume of fluid method in a gas metal arc V-groove welding process with and without root gap for flat, overhead, and vertical welding positions. The elliptically symmetric arc models for arc heat flux, electromagnetic force and arc pressure were used to describe the more accurate molten pool behaviors. The numerical models not only formed a stable weld bead but also simulated the dynamic molten pool behaviors such as overflow which was not described before. This study analyzed these molten pool flow patterns for various welding positions and validated the numerical models used by comparing the simulation results with experimental ones.     

The comparison between laser screw welding and resistant spot welding of lap joint with large thickness ratio

The present paper investigates the welding forming, microstructure and shear tensile test of lap joints with large thickness ratio which were fabricated by laser screw welding(LSW) and resistant spot welding(RSW). The comparison was conducted on two kinds of lap joints, galvanized sheet and hot pressed steel(GS-HPS), galvanized sheet and high strength steel(GS-HS). The microstructure and fracture morphology were analyzed by optical microscope. It was demonstrated that with large thickness ratio the sound lap joint of GS-HS could be obtained by LSW regardless of the irradiation of laser beam from thick metal to sheet or otherwise, and the morphology shows it is better when the laser is irradiated on the thick metal. Nevertheless, when the laser beam was applied on thick metal of HPS, blind hole or blowhole was formed in the center of joint, which is attributed to the shrinkage during solidification of the molten pool. Small pores or dispersed porosity appeared on the faying face of the joint without predetermined gap which provides the degassing. However, the increase of predetermined gap could reduce the shear strength and nugget size. Two kinds of joints made by LSW have superior shear strength than those made by RSW when the laser were applied on galvanized sheet.     

旋转电弧GMAW堆焊短路过渡熔池动态仿真

为探究旋转电弧GMAW堆焊短路过渡时熔池的温度和对流分布规律,利用Flow-3D软件建立三维数学模型,采用球形旋转热源模型,考虑重力、熔滴拖拽力、表面张力、浮力作用,模拟了堆焊状态下,工件材料为Q235的旋转电弧GMAW短路过渡的熔池成形规律. 采用流体体积法追踪熔滴过渡和熔池表面的自由变形,并分析熔滴进入熔池时熔池内部温度场和流场的变化. 结果表明,熔池形成过程中,旋转熔滴对熔池有搅拌作用,并使熔池内部液态金属活性增强,流速变快,熔池内部液态金属体积变大,熔池的宽度变大. 模拟预测的焊缝尺寸、形状与试验吻合良好. 为优化焊接工艺参数、改善旋转电弧GMAW堆焊焊缝质量提供参考依据.