Primary losses in disk and CO2 laser beam inert gas fusion cutting

Cutting experiments with CO₂ and disk lasers were carried out using a design of experiments (DOE) approach. The experimental evaluation of primary energy losses through the cut kerf and their dependence on the type of the applied laser source was performed. The primary energy losses consisting of directly transmitted and reflected laser power were gathered by collecting them within polymethylmethacrylate (PMMA) blocks placed under the sheets being cut. Cutting trials were performed on cold work steel test specimens with different sheet thicknesses. The particular feature of the applied experimental setup was the similar geometry of both the CO₂ and the disk laser beam with comparable values of the focus diameter and the Rayleigh length. Experimental results revealed lower values of primary energy losses in case of disk laser cutting if both processes are compared at the same values of relative cutting speed.     

盘型激光焊接状态多传感信息融合分析

针对大功率盘型激光焊接状态,研究一种基于支持向量机的多传感信息融合分析方法. 使用紫外、可视和红外波段的两个高速摄像机同时获取激光焊接过程中金属蒸气、飞溅和熔池动态图像. 通过模式识别技术提取焊接过程多传感信息特征及进行数据主成分特征分析,并以焊缝宽度变化作为衡量焊接状态稳定性的参数. 运用支持向量机融合各特征,通过网格搜索和粒子群算法优化支持向量机参数,建立基于支持向量机的多传感信息融合模型. 结果表明,支持向量机多传感信息融合方法能够有效预测焊缝宽度变化趋势,为大功率盘型激光焊接状态的实时监控提供试验依据.     

CO2激光切割系统中防反射技术的研究

在CO2激光切割铝、铜等有色金属过程中,经常发生工件反射现象。为防止在激光切割系统中由于光束反射导致的不稳定和损坏,光路系统中必须设计防反射装置进行隔离。本文从理论上阐述了该装置的设计原理、结构形式以及安装方法。     

半导体与CO_2光斑模式下激光熔覆工艺

为了研究不同光斑模式的激光热源熔覆镍基合金效果的差异,分别采用矩形大光斑半导体激光与圆形小光斑CO_2激光在Q235低碳钢表面上进行镍基合金单道熔覆试验。通过相同条件下单道熔覆试验,对比分析不同光斑模式的激光获得的熔覆层尺寸、稀释率以及成形系数随激光功率及扫描速度的变化;还分析了矩形大光斑半导体激光热源与传统圆形小光斑CO_2激光热源的差异。结果表明,在相同工艺参数下,矩形大光斑半导体激光获得的熔覆层尺寸、稀释率及成形系数明显优于传统CO_2激光。     

AZ61镁合金CO2激光焊接工艺

采用CO2激光试验系统对AZ61镁合金的激光焊接工艺进行了研究.探讨了焊接工艺参数包括激光功率、焊接速度、正反面保护气体流量对焊接效果的影响.结果表明,通过适当地选择工艺参数可以获得比较理想的焊缝,并通过大量试验获得了较为优化的参数范围.     

船用钢板的高功率CO2激光焊接

激光作为高能束和洁净热源在焊接中得到了越来越广泛的应用.船舶制造中的激光焊接技术也正得到广泛的研究并开始应用.利用 15 kW 级CO2激光对国产船用板CCS-B、SUS304、A36以及CCS-A进行了对接接头和T形接头的激光焊接研究.在多种板厚条件下获得了良好的激光填丝和激光电弧复合焊接接头.通过宏观和显微金相分析比较CCS-B激光填丝焊和激光电弧复合焊接头焊缝截面形状和组织.通过成分分析,观察了在三种不同高功率激光焊方法(纯激光、激光填丝和激光复合)下焊缝中主要化学成分的含量变化.通过硬度测量、拉伸和弯曲试验测试分析了接头力学性能.     

Parametric investigation of CO2 laser cutting of 2024-T3 alloy

Influence of processing parameters and optimal conditions for CO₂ laser cutting of an aluminium–copper alloy (2024-T3) have been determined. Results are evaluated in terms of productivity (i.e. cutting speed) and cut quality. Moreover, main observed effects in each processing mode are discussed.Superior cut quality is obtained when processing in CW mode versus pulsed mode. The results obtained allow affirming that adopting the necessary precautions for preventing laser beam backreflections and under optimized processing conditions (here identified), sound cuts can be made in 2024-T3 Al alloy. This opens a new sort of materials to be cut by existing CO₂ laser cutting machines.     

IGBT逆变式CO2激光电源的设计研制

采用半桥式逆变电路,使用绝缘栅极晶体管ＩＧＢＴ作主开关器件,研制成功３０ｋＨｚ的高频激光电源。本文主要讨论了升压用高压变压器设计中的结构因素,并给出了采用的方案和设计参数,深入分析了ＥＸＢ８４１模块使用过程中的一些实际技术问题。     

激光能量和辅助气体对切割能力影响的数值模拟

采用旋转高斯激光体热源和氧气流量控制的氧铁燃烧反应放热复合热源,基于计算流体力学建立了能够反映激光切割中激光能量、辅助气体和切缝之间相互作用的多相流模型.利用该模型对以氧气和氮气为辅助气体的激光切割过程进行了数值模拟,通过改变激光功率和辅助气体压力,研究了热输入和辅助气体流场对激光切割能力的影响,并对两种辅助气体的切割结果进行了比较和分析.结果表明,所采用的计算模型较好地模拟出激光功率和辅助气体对激光切割能力的影响,并对切缝形状进行预测.     

CO2激光焊残余应力测试与分析

采用盲孔研究了CO2激光焊工艺参数对焊接残余应力的影响，并对激光焊接工件残余应力的形成过程进行了初步的研究，试验结果表明，激光功率，爆接速度，试板尺寸等因素对残余应力分布情况有明显的影响。     

Properties of magnesium alloy joints welded by a CO2 laser beam

Because of their specific gravity, magnesium alloys find increasing applications in the automotive industry.¹ Safety and travelling comfort requirements, satisfied by the use of steel or aluminium parts, are responsible for the increase in the car weight and, therefore, in increased fuel consumption and consequent environmental pollution.² Replacement of these materials by magnesium alloys satisfies the two requirements while not changing the car mass. The factor which is responsible for the delay in the acceptance of magnesium alloys in the automotive industry is the lack of investigative work into the development of the methods of the manufacture of alloys which would possess the required microstructure, i.e. free of pores and homogeneous structure. The newly developed manufacturing methods indicated, however, that a significant increase in the use of magnesium alloys by the industry can be expected.³ Consequently, a rather limited usage of these alloys in the 1970s for the manufacture of parts, had been extended in the 1990s to whole systems of, mainly, pressure die-cast components (covers, oil sumps, etc) being produced for a number of car makers.⁴     

Investigation of novel metal additive manufacturing process using plasma electron beam based on powder bed fusion

The plasma electron beam (P-ebeam) with a cold cathode has various advantages, including longer cathode life, easier beam diameter control and lower vacuum pressure, as compared to the thermionic electron beam with a hot cathode. The present paper is concerned with investigation of a novel metal additive manufacturing process using the P-ebeam based on powder bed fusion. The proposed process is composed of preheating, deposition and re-melting steps. An experimental system with some desired features is newly developed. Preheating and deposition characteristics are examined to estimate appropriate operation conditions. Fabrication characteristics of the process are elucidated through multi-layer deposition experiments.     

Joint performance of CO2 laser beam welding 5083,H321 aluminum alloy

Laser beam welding of aluminum alloys is expected to offer good mechanical properties of welded joints. In this experimental work reported, CO2 laser beam autogenoas welding and wire feed welding are conducted on 4 mm thick 5083- H321 aluminum alloy sheets at different welding variables. The mechanical properties and microstructure characteristics of the welds are evaluated through tensile tests, micro-hardness tests, optical microscopy and scanning electron microscopy （SEM）. Experimental results indicate that both the tensile strength and hardness of laser beam welds are affected by the constitution of filler material, except the yield strength. The soften region of laser beam welds is not in the heat-affected zone （ HAZ ）. The tensile fracture of laser beam welded specimens takes place in the weld zone and close to the weld boundary because of different filler materials. Some pores are found on the fracture face, including hydrogen porosities and blow holes, but these pores have no influence on the tensile strength of laser beam welds. Tensile strength values of laser beam welds with filler wire are up to 345.57 MPa, 93% of base material values, and yield strengths of laser beam welds are equivalent to those of base metal （264. 50 MPa）.     

Automated task planning for industrial robots and laser scanners for remote laser beam welding and cutting

Remote laser beam welding and cutting can be applied to a wide range of applications within the manufacturing technology domain. With high process rates, consistent high quality welding seams and cutting edges at various contours these technologies offer an increased flexibility to process a wide variety of work pieces. To take advantage of the process the laser beam must be positioned precisely on the work piece. Programming a system of an industrial robot combined with a laser beam deflecting scanner manually is a very time consuming job. Programming any “on the fly” movements, a synchronously movement of the scanner and the robot, is even more difficult. This paper describes challenges and a concept for the automated programming of the two devices to apply the advantages of remote laser beam welding and cutting.     

基于PC的激光切割数控系统的开发研究

阐述了采用普通PC机和可编程多轴控制卡(PMAC)实现激光切割的数控系统，并简要介绍了该系统的组成以及硬件、软件结构。     

关于大功率CO2激光器在船舶制造中应用的探讨

文章介绍了在欧洲一些工业发达国家激光焊接技术在船舶制造中应用的发展历程和现状,指出了大功率CO2激光器在船舶制造应用中需要解决的问题:光束传输与变换、激光焊接过程中激光束与焊缝中心的对位以及激光焊接技术在船舶制造中应用的经济性,进而指出激光焊接技术在船舶制造的应用研究中不仅要从激光焊接技术的工艺可行性入手,还要从光束传输、设备制造、焊缝跟踪以及船体结构等方面入手进行多方面的研究.     

CO_2激光-MAG电弧复合焊过程中激光功率对电弧及熔滴行为的影响

利用高速摄像系统和电弧分析仪分析CO2激光-MAG电弧复合焊过程中激光功率对电弧及熔滴行为的影响。试验结果表明:焊接过程中的实际热源间距受到焊接电流大小的影响,且当其在2 mm时焊接效果最优;在导电通道中的带电粒子在运动过程中扰动、漂移以及熔滴过渡模式、焊接模式的改变造成了焊接过程中电弧电流及电压波形的紊乱;激光功率影响了熔滴行为,当采用160 A和180 A的焊接电流时,激光功率的增加导致熔滴过渡频率先减小后增大。     

基于同轴视觉的激光切割质量自寻优控制

研制了基于同轴视觉传感、DSP和开放式数控系统的在线检测与控制系统,获得了火花簇射的视觉图像,发现同轴最大火花簇射长度(火花簇射图像中不同亮度带的最大像素数)与最低的切割面粗糙度具有很好的对应关系.利用这一规律,进行了激光切割质量的实时检测与自寻优控制.结果表明,系统可以迅速的找到最佳切割速度,获得该工艺条件下切割面近下缘粗糙度最小.