激光与电弧相互作用时的电弧形态及焊缝特征

激光与电弧的复合热源在焊接过程中，由于激光的压缩与引导作用，可以在焊接速度增加时，电弧仍然较稳定。在去掉激光同轴保护气流而只采用TIG的保护气体进行保护时，由于激光同轴气体的冲击、压缩和冷却作用的消失，等离子气体将会随着电流、激光功率的增加而增大，因而引起焊缝横截面的变化。通过调整激光与电弧的规范参数，并用CCD摄取各参数下的电弧图像以分析等离子体的长大情况，然后将得到的焊缝沿横截面剖开。通过对各种参数下等离子体图像和焊缝横截面之间的相互的关系进行分析，得到与常规情况下相比熔宽较宽而熔深较浅的焊缝的焊接参数。这种产生涂敷型焊缝的参数可用于高速表层涂覆。     

Temperature field simulation of laser-TIG hybrid welding

The three-dimensional transient temperature distribution of laser-TlG hybrid welding was analyzed and simulated numerically. Calculations were based on a finite element model, in which the physical process of hybrid welding was studied and the coupling effect of the laser and arc in the hybrid process was fully considered. The temperature fields and weld crosssections of the typical welding parameters are obtained using present model. The calculation results shou that the model can indicate the relationship of energy match between laser and arc to joints cross-sections objectively, and the simulation results are well agreed with the experimental results.     

Welding characteristics in different laser-TIG hybrid manners

An experiment for determining the laser-TIG hybrid welding characteristics was carried oat in three kinds of hybrid methods: CO2 laser-TIG coaxial hybrid, CO2 laser-TIG paraxial hybrid and Nd: YAG laser-TIG paraxial hybrid. The experimental results indicate that hybrid welding has two welding mechanisms in CO2 laser-TIG hybrid welding: deep penetration welding and heat conduction welding. As the effect of the laser-induced keyhole, the arc root is condensed, the current density and penetration depth increase significantly, the welding characteristic is apt to deep penetration welding.When current increases to some degree, the keyhole induced by laser disappears, which produces a shallow penetration and wide bead. The weld exhibits heat conduction welding characteristics. Furthermore, the arc images and weld bead crosssections of three kinds of hybrid manners were also compared and analyzed at different welding currents, which established the foundation for understanding the welding characteristics of laser-TIG hybrid welding comprehensively.     

铝合金激光-钨极氩弧双面焊的焊接特性

以4 mm和10 mm厚5A06铝合金为实验材料,对激光-钨极氩弧(TIG)双面焊(LTDSW)的焊接特性进行了研究.该工艺充分利用了激光和钨极氩弧两种热源相互作用的优势,不仅可以获得稳定可靠的焊接过程与美观的焊缝成形,还具有显著增加接头熔深、减少焊接缺陷、提高焊接生产率和降低焊接成本等优势,实现了在小功率(1.0 kW)激光条件下4 mm厚铝合金板的可靠连接.与激光焊相比,激光-钨极氩弧双面焊的气孔数量有所下降,气孔分布位置主要受激光和电弧能量匹配关系的影响,气孔数量和大小主要取决于焊接热输入的大小.激光-钨极氩弧双面焊的接头抗拉强度为310 MPa,约为母材强度的88%.     

不锈钢激光-电弧双面焊接头熔化特征分析

在4 mm厚不锈钢激光-电弧双面焊接试验的基础上,研究了激光功率、电弧电流对接头形貌特征和接头特征量的影响规律,并对熔化效率进行了分析。结果表明,在较小的能量匹配下,双面焊接头呈现出激光焊与电弧焊的混合特征,随着热输入的增大,混合特征消失;增大激光功率,可使激光侧焊缝熔宽增加,而电弧侧焊缝熔宽减小,增加电弧电流,可使电弧侧焊缝熔宽增加,而对激光侧焊缝影响很小;激光功率和电弧电流增加都对焊缝中部最小熔宽有明显的增加;中部最小熔宽的深度随激光功率增加而增加,而电弧电流则起到相反的作用。在非熔透条件下,激光对电弧焊的熔化效率影响很明显,而电弧对激光焊的影响很小;在熔透条件下,增加激光功率、电弧电流对激光电弧双面焊的熔化效率都有显著的提高。     

利用光致等离子体声信号监测激光焊缝的熔透性

介绍了CO2 激光深熔焊接时 ,利用光致等离子体声信号来监测焊缝熔透性的一种方法。文中通过试验研究 ,获得了焊缝熔透性变化时 ,光致等离子体声信号的变化规律 ,从而建立了一种可正面监测焊缝熔透性的方法     

Influence of laser energy input mode on joint interface characteristics in laser brazing with Cu-base filler metal

The flange butt joints of 1 mm-thick galvanized steel sheets were brazed with CuSi3 as filler metal at different laser heating modes. The microstructures and element distributions of joint interface were investigated by SEM and EDS. The results show that there is no obvious interface layer with the circular individual beam heating and lamellar Fe-Si intermetallic compound layer is found with dual-beam laser spot heating. With the irradiation of rectangular laser spot, the joint interface layer is also formed. The layer thickness is larger than that of dual-beam brazing and the layer shape is flat so that intermetallic compounds trend to grow into cellular crystals. Moreover, the interface layer shape also depends on its position in the joint. Under the high heat input, dendritic or granular intermetallic compounds dispersively distribute in brazing seam adjacent to the interface, which is caused by the melting or dissolving of the base metal. According to the results, the brazing quality can be controlled by laser heating mode and processing parameters.     

铝钛异种合金的激光熔钎焊

提出了一种连接Al/Ti异种合金的新工艺，即采用激光为热源，AlSi12为填充材料，实现了Ti-6Al-4V钛合金和LF6铝合金的激光熔钎焊连接。激光熔钎焊是一种局部加热焊接过程，通过调整激光加热参数，控制填充材料的润湿铺展及界面金属间化合物的形态和数量，从而控制接头质量。在实验过程中，填充焊丝实时送入，通过改变激光功率、间隙大小、光斑尺寸、焊接速度、送丝速度、激光辐照位置等工艺参数，以获得对接头的不同加热效果。研究了不同参数下的钎缝成形规律、接头界面特点及接头拉伸强度。结果表明，采用激光熔钎焊工艺连接Al/Ti异种合金可以获得成形良好、强度较高的接头，但焊接过程对工艺参数要求严格;接头厚度方向不同位置的界面金属间化合物的厚度和形态各不相同;热输入较低情况下，钎料与钛合金材料作用不充分，接头易从界面处断裂;热输入较高时，接头容易从铝合金侧熔合区附近断裂。     

Relation between welding parameter and acoustic emission information during laser deep penetration welding

In laser non-penetration deep penetration welding process, welding material will vaporize, metal vapor and ambient gas will produce a higher degree ionization, which forms plasma of high concentration. In the case of forming a small hole, plasma will eject .from the hole, and form acoustic emission ( AE ) signals. Because AE information has many advantages such as non-contact measuring, fast response, and high ratio of signal to noise, it can be used as a monitor variable for in-process control. By studying AE information, information of welding pool and small hole can be obtained. According to characteristic of AE information, this paper reveals the correlation between welding parameters and AE signals, and provides a good base for further quality control.     

激光弯曲成形温度场的有限元数值模拟

激光成形技术是以激光为热源加热金属板料,依靠内应力使板料弯曲成形。研究激光成形过程中弯曲角与各影响参数之间的关系,了解板料内部温度场的分布规律是尤为重要的。本文应用有限元方法对不同热源形式、激光参数、板料尺寸及冷却条件下的三维瞬态温度场进行了数值模拟,分析了各因素对激光成形温度场的影响特性,为进一步的应力应变分析打下基础。