TIG焊产生咬边影响机理的仿真计算

避免咬边是提高焊接速度过程中的关键要素。从数值模拟入手,采用有限元分析的方法,使用ANSYS软件进行数值模拟,通过TIG焊过程中不同焊接速度时熔池成形规律,分析解决高速焊接时的咬边问题;指出了在保证相同熔深的前提下,随着焊接速度的提高,熔宽最大处的深宽比越来越小,当达到某一临界值时,咬边就会产生,并进行了实验验证。     

耦合电弧钨极GPCA-TIG焊工艺

将耦合电弧钨极和GPCA焊方法结合,形成了耦合电弧钨极GPCA-TIG焊方法,该方法可实现深熔深高速度焊接.对比分析了在较高焊接速度时常规TIG焊、耦合电弧钨极TIG焊和耦合电弧钨极GPCA-TIG焊的焊缝表面成形和截面形貌,发现耦合电弧钨极GPCA-TIG焊可避免咬边和驼峰焊道的产生,并且焊缝熔深有所增加.耦合电弧钨极GPCA-TIG焊工艺试验表明,焊缝熔深和熔宽随焊接速度的减小和外喷嘴位置的升高而增大,随着弧长和外层氧气流量的增加先增加后略有减小;随着焊接速度的减小,弧长和外层氧气流量的增大,焊缝咬边减轻,外喷嘴相对高度变化时焊缝均未出现咬边.     

高速TIG-MIG复合焊焊缝驼峰及咬边消除机理

搭建了TIG-MIG复合焊试验平台及电参数-高速图像同步采集系统,进行了一系列低碳钢高速TIG-MIG复合焊工艺试验,研究了高速TIG-MIG复合焊的电弧形态、熔滴过渡及熔池行为对焊缝成形的影响,并确定了合适的匹配参数.结果表明,MIG焊电流在240~300 A,且TIG焊电流与MIG焊电流相当时,TIG-MIG复合焊焊接过程稳定,即使在焊接速度高达2.5 m/min时,焊缝仍无驼峰、咬边等缺陷,与传统MIG焊相比,熔深增加,熔宽减小.TIG-MIG复合焊由于电弧间的相互作用,两电弧指向发生偏转,电弧压力减小,焊接过程不产生弧坑,且熔宽变窄,这是避免驼峰和咬边缺陷的主要原因.     

双TIG活性电弧焊接工艺

提出双TIG活性电弧焊接方法,采用2支TIG焊枪前后排布,前置焊枪的焊接电流小于后置焊枪,且在前置焊枪保护气中混入少量O2,使电弧具有活性。对5 mm厚SUS304奥氏体不锈钢板进行焊接工艺试验。结果表明,与相同条件下的TIG焊接相比,双TIG活性电弧焊接焊缝熔深明显增加,焊缝表面成形良好;随着O2流量的增加,焊缝熔深先增加后减小,焊缝熔宽先减小后增加;在保持总电流不变的情形下,随着后置焊枪电流增加(前置焊枪电流减小),焊缝熔深先增加后减小,焊缝熔宽持续增加;随着弧长的增加,焊缝熔深先增加后减小,焊缝熔宽逐渐增加;当钨极间距从3 mm开始增加时,焊缝熔深逐渐减小,熔宽逐渐增加;而随着焊接速度的增加,焊缝熔深和熔宽都减小。O的混入对焊缝组织无明显影响。相比母材而言,焊缝冲击韧性有所下降。该方法能在高于普通TIG焊接速度的条件下实现深熔焊接。 创新点： 提出双TIG活性电弧焊接,2支独立的焊枪在焊接方向的平面内前后排布,前置焊枪焊接电流小于后置焊枪,前置焊枪采用Ar+O2作为保护气体,后置焊枪采用纯Ar作为保护气体,从而使电弧具有活性;在高于传统TIG的焊接速度下,焊缝熔深明显增加,可实现5 mm 厚的不锈钢板完全焊透。 高速焊接时能消除驼峰和咬边等缺陷,明显提高焊接生产率。     

外界因素对焊接咬边问题的影响规律

采用Ansys有限元分析法建立了数学模型,分析咬边形成和熔宽最大处熔池的深宽比之间的关系;通过数值模拟方法,分析了工件厚度、工件初始温度以及散热条件对熔池温度场的影响,发现工件厚度较小时不易产生咬边现象,通过提高工件预热温度、改善散热条件可有效抑制咬边的产生,最后,通过对不同预热温度下的工件进行TIG焊接实验,验证了数值模拟结果的正确性。     

光纤激光辅助TIG焊焊缝成形特点及影响因素分析

在活性焊接法研究的基础上提出了激光辅助TIG焊方法.焊前在氧气保护下采用小功率激光器熔化焊道表面,然后用常规TIG焊覆盖激光预熔焊道,从而可使熔深增加,熔宽减小.结果表明,激光预熔和未预熔焊道熔深、熔宽均随焊接电流的增加而增加,但激光预熔焊道熔深增加的更快;焊接速度的增加使激光预熔和未预熔焊道熔深、熔宽均减小;随激光功率增加,焊道熔深增加,熔宽减小;随预熔速度的增加,熔深先增大后减小,熔宽先减小后增大.综合最佳参数后可以得到焊缝熔深增加明显、焊缝表面成形良好的焊道,从而可以发展为一种新的活性焊接法.     

工艺参数对机器人TIG焊焊缝成形与组织的影响

在Q235钢平板上进行机器人TIG焊试验,研究焊接电流、电弧电压和焊接速度3个焊接工艺参数对焊缝成形与微观组织的影响。研究结果表明,当其中两个焊接工艺参数恒定时,熔深、熔宽和深宽比均随着焊接电流的增大而明显增大;焊缝的熔深和深宽比随着电弧电压的增大而减小,熔宽随着电弧电压的增大而增大;熔深、熔宽和深宽比均随着焊接速度的增大而减小。随着焊接速度的增大,焊缝区与热影响区的珠光体组织减少,铁素体组织增加,组织细化。     

气体熔池耦合活性TIG焊方法

提出了一种新型活性TIG焊方法——气体熔池耦合活性TIG焊,即GPCA-TIG焊.该焊接方法将气体分两层流动,内层气体采用惰性气体起到保护熔池的作用;外层气体则为含活性元素O的气体,将活性元素O引入熔池金属,达到增加熔深的目的.文中以SUS304不锈钢为焊接母材,研究了GPCA-TIG焊接法对焊接电弧及焊缝成形的作用,以及该方法主要工艺参数对焊缝熔深和深宽比的影响.结果表明,在相同参数下,与常规TIG焊方法相比,GPCA-TIG焊可不开坡口一次性焊透8 mm不锈钢板,焊接效率明显提高.同时采用该方法,可以有效避免钨极的氧化烧损.     

A-TIG焊接熔深增加机理

活性化氩弧焊(A-TIG)焊接方法与传统TIG焊相比,具有明显的熔深增加作用.模拟了Nimonic 263 A-TIG焊接流场温度场,并对试验与模拟焊缝形状进行了对比.结果表明,同一焊接电流下,与TIG焊缝相比,A-TIG焊缝的熔深较深而熔宽较小.随着焊接电流的增加或者焊接速度的降低,A-TIG焊缝熔深呈线性增加,且比TIG焊的熔深增加效果明显.通过分析流体流动方式,进一步推测了A-TIG熔深增加机理:熔池内液体流动方式是熔深增加的主要原因,熔池中心处液体的流速明显高于熔池边缘,中心由外向内的环流为熔池内液体流动的主导方向.这个方向的环流将高温液体带到熔池底部,使熔池底部的熔化速度较熔池边缘有了明显的增加,且随着焊接电流的增加,熔深增加效果也不断提高.     

耦合电弧AA-TIG高速焊工艺

传统TIG焊焊接熔深浅、效率低,焊接速度提高时会出现咬边和驼峰等焊接缺陷.传统活性焊(A-TIG)相对于传统TIG焊可以显著增加熔深,但由于电弧压力作用,在高于一定焊接速度时仍会出现咬边和驼峰等焊缝缺陷.以SUS304不锈钢为母材,提出新型的耦合电弧AA-TIG(arc assited activatingTIG we...     

High speed tandem TIG welding of ferritic stainless steel plate

Weld humping and undercut are the most common appearance defects in high speed welding. A high speed tandem TIG welding process was developed to suppress the formation of these appearance defects and to improve the productivity of TIG welding. In this paper, the mechanical properties and microstructure of joints obtained from tandem and single TIG welding were tested and compared. The results show that the sound weld appearance can be obtained by tandem TIG welding at the welding speed of 3 m/min for 1.5 mm thick 409L stainless steel plate. The mechanical properties of the tandem TIG welded joint are in the similar level with single TIG welded joint. The analysis of the tandem TIG welding process indicates that the assistant arc with a push angle can prevent the liquid metal flowing backward to the trailing region of weld pool and the premature solidification of thin liquid layer in the gouging region.     

TIG焊和PAW焊中活性剂对焊缝熔深的影响

针对常规TIG焊生产效率低、熔深小等问题，研究了TIG焊和PAW焊中应用活性剂对焊缝熔深的影响。结果表明，应用活性剂后，在同样的参数下，同传统TIG相比，活性剂能够大幅度提高不锈钢、铝合金和钛合金的焊缝熔深。对于PAW焊，熔深也有增加，但是增加的幅度不如TIG效果明显，但对焊缝成形有很好的改善。同时，活性剂对铝合金焊接背面能够起到保护作用。对于钛合金，活性剂除了增加焊缝的熔深外，还能够大幅度地消减焊缝产生的气孔。     

连续行走脉冲TIG焊熔池谐振法熔透控制

熔池振荡频率与熔池尺寸之间的良好对应关系,可以用于进行熔池尺寸检测及熔透控制,但在快速行走焊接时难度很大。本文在恒定直流之上叠加定频率正弦波电流做为脉冲焊接电流激振熔池,在连续行走焊接时,通过电弧电压检测熔池振荡即熔池尺寸。在脉冲电流作用期间,随着熔池尺寸的增长,当熔池自身固有振荡频率与焊接电流正弦波频率一致时,熔池产生谐振,从电弧电压中检测到谐振特征变化信号,该信号的强度,稳定性,重复性及与熔池     

Correlation between weld formation and processing parameters in CO2 laser welding of steels

Abstract

Laser welding, which has undergone rapid development in the past few decades, is one of the most important applications in laser materials processing. Although some general data are available, precise welding parameters are equipment specific. In the present study, a series of autogenous laser welds on mild and stainless steels has been investigated, using a Trumpf 3·0 kW CO² laser system, to establish welding parameter windows. The correlation between laser power, welding speed, and weld bead profile for bead on plate welding has been obtained. For a constant laser power, penetration depth reaches a stable value as welding speed exceeds 11 000–13 000 mm min^-1. This value is defined as the penetration threshold. Lower welding speed produces deeper penetration. However, under such conditions, the unstable keyhole and weld pool could result in undercut and porosity. The maximum penetration achievable for sound welds on both mild steel and stainless steel was investigated. The correlation between penetration threshold and power level was also established. The parameter windows established for autogenous welds can be adopted effectively on butt jointsif welding speed is reduced by 25%.     

激光-电弧复合焊接咬边缺陷分析及抑制方法

为了提高激光-电弧复合焊接的可靠性,对复合焊接咬边缺陷成形机理及抑制方法进行了研究.结果表明,激光能够提高复合焊接的临界咬边速度,最高可达电弧焊接的5倍.在激光-电弧相互作用下,复合焊接存在两种抑制咬边的机理.一种是改变焊趾处固、液、气三相的表面张力状况,形成指向熔池外部的合力.另一种是通过提高熔池内温度梯度和热输入来增加熔池内由内向外的流动速度和时间,使熔化金属能够流向并填充焊趾,这种抑制机理作用更为显著.试验确定了复合焊接临界咬边速度的经验公式和电弧电压的合理调节范围.     

The arc characteristic of ultrasonic assisted TIG welding

Many applications of ultrasonic-assisted methods were used during metal solidification, but they could not be introduced into weld pool. In this paper, a way of ultrasonic assisted TIG welding is introduced. By directly imposed ultrasonic vibration on welding arc, the vibration interacts with arc plasma and passes to the weld pool. Measurement results show that arc pressure is significantly increased with the ultrasonic vibration and the arc pressure distribution models are changed. Bead-on-plate welding tests on SUS304 confirm that this technology can influence the style of metal melting and increase weld penetration depth.     

Study of the law between the weld pool shape variations with the welding parameters under two TIG processes

A double-shielded TIG method was proposed to improve weld penetration and has been compared with the traditional TIG welding method under different welding parameters (i.e., speed, arc length and current). The strength of the Marangoni convection was calculated to estimate the influence of the welding parameters on the variations in weld pool shapes. The results show that the changes in the welding parameters directly impact the oxygen concentration in the weld pool and the temperature distribution on the pool surface. The oxygen content and heat distribution on the weld pool surface are determinants of the pattern and strength of the Marangoni convection. For a negative temperature coefficient of surface tension (∂σ/∂T < 0), an outward Marangoni convection leads to a wide and shallow weld pool shape. The narrow and deep weld pool shape occurs when the Marangoni convection flows along an inward direction (∂σ/∂T > 0). The oxide layer that may appear with the relatively high oxygen content in the weld pool is harmful for the heat flow along the pool surface so as to reduce the welding efficiency especially in the double shielded TIG process.