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 front tandem and single 77G 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 T1G 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.

Experimental determination of the critical welding speed in high speed MAG welding

In high speed MAG welding process, some weld formation defects may be encountered. To get good weld quality, the critical welding speed beyond which humping or undercutting weld bead can occur must be known for different conditions. In this research, high speed MAG welding tests were carried out to check out the effects of different factors on the critical welding speed. Through observing the weld bead profiles and the macrographs of the transverse sections of MAG welds, the occurrence tendency of humping weld was analyzed, and the values of critical welding speed were determined under different levels of welding current or voltage, and the effect of shielding gas compositions on the critical welding speed was also investigated.

Implementation of high speed arc welding with DE-GMAW

Modern manufacturing industry demands low cost and high efficient welding processes to remain competitiveness in the time of globalization. In this study, conventional gas metal arc welding （GMAW） was modified, a double-electrode GMAW （DE-GMAW） system is developed and DE-GMAW process is implemented through optimization of the design and process parameters and suitable selection of igniting sequence of double arcs. High speed welding tests were carried out to examine the effects of different factors on occurrence of weld formation defects. Through observing the weld bead appearance in DE-GMA W, the values of critical welding speed were determined under different levels of welding current and welding speed.

Application and development of friction stir welding technology in high speed EMU manufacturing

The application status of friction stir welding technology is introduced,and the application research of advanced FSW technology in the manufacture of high-speed electric multiple unit aluminum alloy body is analyzed,including the application of traditional friction stir welding technology to a combination of a lap joint and butt joint,and butt joint of large thick plate by both sides process,also introduces bobbin-tool friction stir welding to a butt joint and three-dimensional space curved friction stir welding to T-joint. At the same time the future development trend of new FSW technology derived from traditional FSW technology in rail vehicle manufacturing industry is put forward. As the fast developing of critical technology used on railway vehicles,quick applying advanced welding technology will affect products quality,manufacturing cost and production cycle time directly,and it certainly will be one of the approaches to develop markets by all the railway vehicles manufacturing enterprises.

Numerical simulation and control of welding distortion for double floor structure of high speed train

The welding heat source models and the plastic tension zone sizes of a typical weld joint involved in the double floor structure of high speed train under different welding parameters were calculated by a thermal-elastic-plastic FEM analysis based on SYSWELD code.Then,the welding distortion of floor structure was predicted using a linear elastic FEM and shrinkage method based on Weld Planner software.The effects of welding sequence,clamping configuration and reverse deformation on welding distortion of floor structure were examined numerically.The results indicate that the established elastic FEM model for floor structure is reliable for predicting the distribution of welding distortion in view of the good agreement between the calculated results and the measured distortion for real double floor structure.Compared with the welding sequence,the clamping configuration and the reverse deformation have a significant influence on the welding distortion of floor structure.In the case of30 mm reverse deformation,the maximum deformation can be reduced about 70%in comparison to an actual welding process.

Effect of welding current and speed on occurrence of humping bead in high-speed GMAW

The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding （GMAW） is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.

High-speed butt welding of magnesium alloy using pulsed laser-arc hybrid heat source

Laser-arc hybrid welding at a speed of 6 000 mm/min is carried out on 2 mm thick magnesium alloy AZ61 plateand completely-penetrated butt joints are obtained, lnvestigations of the influence of parameters on weld formation show that Ihe addition of pulsed laser can effctively enhance tlle heat penetrability attd directivity nf the hybrid heat source. Measurements on microstructures and mechanical properties the joint indicate that grain in the.fhsion zone is refined and the grain size is sensitive to the arc current ; the fitsioa zone exhibits the highest hardaess; the tensile strength of the joint reaches 93% of base metal; there is the brittle fracture along the grain bozmdaries in the fusion zone. High-speed camera images exhibit that although the two adjacent laser pulses can not overlap, the recorery relaxation of the concentrated electric arc after laser intlse action can still maintain the continuous welding process.

Characteristics of the electrode melting phenomena in narrow gap MAG high-rotating-speed arc welding

The influence of rotating speed on metal transfer and the wire metal speed was studied in the high rotating speed arc narrow gap welding.The results indicate that the high rotating speed arc has benefit on the metal transfer,and that with the rotating speed increasing,the droplet volume decreases.It is shown that the rotating speed has little influence on the wire metal speed with DC electrode positive polarity(DCEP),but the melting speed decreases with increasing of rotating speed in DC electrode negative polarity(DCEN).

Analysis of droplet transfer of pulsed MIG welding based on electrical signal and high-speed photography

In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of droplet transfer simultaneously, which is based on a self-developed soft-switching inverter. On the one hand, welding current and voltage signals are acquired and analyzed by a self-developed dynamic wavelet analyzer. On the other hand, images are filtered and optimized after they are captured by high-speed camera. The results show that instantaneous waveforms and statistical data of electrical signal contribute to make an overall assessment of welding quality, and that optimized high-speed images allow a visual and clear observation of droplet transfer process. The analysis of both waveforms and images leads to a further research on droplet transfer mechanism and provides a basis for precise control of droplet transfer.

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.

Effects of current waveform parameters during droplet transfer on spatter in high speed waveform controlled Short-circuiting GMAW

Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.

Analysis of Laser-Induced Plume During Disk Laser Welding at Different Speeds

During high power disk laser welding, the high-speed photography was used to measure the dynamic images of the laser-induced plume at different laser welding speeds. Various plume features （area, height and brightness） were extracted from the images by the color space clustering algorithm. Combined with observation on the surface and the cross sections of welding samples, the effect of welding speed on welding stability was analyzed. From the experimental results, it was found that these features of plume could reflect the welding state. Thus changes of the plume features corresponded to different welding speeds, which was helpful for monitoring the laser welding stability.

Some Problems of Rails for High-speed Railway of China

According to running experience of high speed railway abroad, a full attention must be paid to some requirements of specification of rails for high speed railway, such as material mechanical properties, dimension tolerances, straightness, surface flatness and so on. It is suggested that the long length rails should be laid in high speed railway, and the feasibility of producing, welding and transporting of long length rails should be researched. On the basis of technical innovation of domestic manufacturers, it is practicable to lay 50-100 m long\|length homemade rails in high speed railway of China. The following welding programme of rails for high speed railway can be adop\| ted: 50-100 m long length rails can be welded as 500 m long rail string through flash butt welding in plant, then in field the rail string can be welded through a mobile flash butt welding or thermit welding. As the specification of rails for high speed railway is rigorous, some related techniques to long length rails should be researched and practised as soon as possible, including mobile flash butt welding technique, transporting and reinforcing techniques of long length rails, etc..

高速钢桶焊缝机电机座支撑脚复合模设计

针对高速钢桶焊缝机电机座支撑脚使用2 mm厚的SECC板料进行中小批量冲压成形的要求,设计了3副模具用于制件的4道工序成形。冲孔落料和修边压印采用倒装式复合模结构、切分模和弯曲模采用正装结构,且切分模和弯曲模集成在1副模具内。弯曲模中设计了凸模驱动的双滑块内收弯曲成形机构,该机构在制件弯曲壁的两侧都使用滑块进行夹紧驱动弯曲,能有效防止弯曲回弹,保证了制件的弯曲成形尺寸。模具结构简单实用,成形工艺设计合理,实现了制件的自动化生产。

高速拉拔ER70S-6焊丝钢生产工艺优化

通过总结分析ER70S-6焊丝钢存在的质量问题,提出了有针对性的优化改进措施,重点对ER70S-6焊丝钢的化学成分范围、气体氮含量、尺寸精度、显微组织等关键指标严格控制,攻关后C、Si、Mn、N含量内控达标率提高,尺寸偏差C级精度得到改善,而且消除了混晶异常组织。用户拉拔使用结果表明,优化后的焊丝钢质量得到进一步的提高,可满足用户拉拔速度28 m/s以上高速拉拔的要求。

6061-T6铝合金高速搅拌摩擦焊数值模拟

基于耦合欧拉-拉格朗日方法,建立了6061-T6铝合金薄板的高速搅拌摩擦焊数值模型,研究高速焊接工艺条件下的温度场及变形场特点,采用示踪粒子方法研究焊接区材料塑性流动规律。开展高速搅拌摩擦焊试验,分别从温度场、宏观样貌和内部缺陷对数值模型进行验证。结果表明,采用该模型能够准确描述高速搅拌摩擦焊过程的温度场及变形场,也能精准预测焊接缺陷出现的位置及尺寸。相较于常规搅拌摩擦焊,高速搅拌摩擦焊在焊接方向和横截面都具有更密集的温度梯度,塑性应变区域也较为集中,其热影响区更小。

焊接位置对激光-电弧复合焊接底部驼峰的影响

目的通过改变焊接位置来抑制底部驼峰的形成进而降低生产成本。方法使用高速摄像机观察平向焊接和横向焊接2种不同焊接位置下熔池的匙孔和底部驼峰的形成过程,并对底部凸起受到的金属蒸气反冲压力、熔融金属重力以及表面张力进行受力分析。结果在S355J2W耐候钢的激光-电弧复合焊接平焊过程中,受金属蒸气反冲作用力的影响,熔融金属迅速从匙孔底部排出,流入匙孔底部凸起区域,底部凸起的增长速度极快,仅需7.5 ms即可形成大尺寸的驼峰。而在横向焊接中,匙孔前壁凸起数量减少,导致金属蒸气反冲压力减小,匙孔排出的熔融金属量减少,底部凸起的增速减缓,在13.6 ms时才达到最大高度,使驼峰在底部熔池凝固之前难以形成。结论采用横向焊接的方式可以有效避免驼峰的产生,降低生产成本。同时,该方式在焊缝背部成形效果方面也表现良好,为优化焊接工艺提供了重要参考。

高速列车侧墙焊接虚拟现实系统开发

侧墙是高速列车车体的主要构成部分,由于其焊接工艺复杂、专业设备昂贵,因此企业需要不断培养技术熟练的员工来满足生产要求,但常规的人员现场培训方法会占用专业的生产设备,降低企业生产效率,难以达到良好的培训效果。为了满足企业对专业焊接人才培养及培训的需要,基于虚拟现实技术,通过3dsMax建立焊接车间及装卡工具模型,采用LOD技术降低内存占用。依靠Unity3D虚拟现实引擎搭建仿真环境,采用C#编程语言开发系统功能,并应用包围盒算法优化焊接过程演示。参照铝合金侧墙焊接工艺流程,开发完成高速列车侧墙焊接虚拟现实系统。实践表明,所开发的系统包含知识考核、操作交互、结果展示等功能,具有较好的实用性、可视性及沉浸感,能够有效满足高速列车制造人员训练要求,同时保证培训期间企业生产效率,降低了事故发生的概率。

Q355/SKH9高速钢激光重频焊接接头冲击韧性分析

文章采用激光焊接技术制造Q355/SKH9高速钢焊接接头,并开展V型缺口冲击韧性实验。研究结果表明:当试验温度下降后,接头受到了更小冲击吸收能量作用,焊接接头形成了明显梯度冲击韧性;在BM中存在大量回火板条型马氏体组织,HAZ热处理时内部形成了不同焊接热循环过程;在BM和HAZ断口部位形成了许多撕裂棱,表现为准解理断裂;断HAZ具备优异韧性,达到了比BM更优的韧性;经过回火处理后,板条马氏体与粒状贝氏体获得了更强冲击韧性;BM保持相对稳定的显微硬度与剪切强度,HAZ形成了大梯度变化的显微硬度与剪切强度;经过焊接热循环处理与之后回火过程,HAZ基体与晶界部位形成了更多碳化物,增大HAZ强度与硬度。

复层TA1和中间层Cu之间的冶金结合状态及其对焊接质量的影响分析

TA1材料和其他低成本材料相结合是钛金属较为常见的应用方式。针对TA1/Cu复合板材料的性能问题,研究设计了一种焊接材料的冶金结合状态及焊接质量分析方法,利用激光高速冲击焊接进行焊接的试块制作方法,利用圆形冷镶嵌模具制作观察微观样貌的试样。实验结果表明:在飞行距离为0.1 mm、试件伸长量达到0.14 mm时,试件拉伸剪切力达到最大值7.46 N;在飞行距离为0.2 mm、试件伸长量达到1.93 mm时,试件剥离力达到最大值3.64 N,说明研究方法能够有效对焊接材料的冶金结合状态及其对焊接质量的影响进行分析。