水再压缩等离子弧切割喷嘴的改进及应用

水再压缩等离子弧切割是常规的氮气等离子弧切割技术的一个发展,它进一步提高切割质量、效率,并有效地改善了因等离子弧切削所造成的环境污染,改善了工人的劳功条件。喷嘴结构当前实现水再压缩等离子弧切割的方法,大都是在割炬喷嘴之外再加一个由绝缘物质(如页腊石)做成的水喷嘴,由其喷水进一步     

信息窗

核工业部第六研究所研究的空气等离子水再压缩弧切割技术已于1984年10年通过技术鉴定。采用这种切割方法可高质量地切割不锈钢、铜、铝、铸铁、碳钢等金属。这种方法的优点是:气源(压缩空气)方便、成本低廉、切割效率高、切口光洁无挂渣、切缝     

磁再约束等离子弧切割陶瓷实验研究

通过磁再约束等离子弧切割陶瓷实验，考察约束磁场对等离子弧特性，切割质量及无渣切速的影响规律，分析了所用磁约束装置的性能和方法的局限性，指出了进一步研究高质量约束磁场装置的必要性。     

提高等离子切割机切割质量的方法

介绍了等离子切割机的孤切割原理,指出了等离子孤切割的质量评价标准,从切口宽度和平面度、切口熔瘤消除方法、如何避免双弧产生和大厚度切割质量控制等方面阐述了提高等离子切割机切割质量的方法.     

横向磁场压缩等离子弧提高切割效能的试验

本文介绍了用横向磁场压缩等离子弧减少等离子弧切口宽度和提高切割速度的探讨试验。试验表明,此方法是有效的。     

水再压缩等离子弧切割的研究

本文研究设计的新型水再压缩等离子弧割炬,也可以作为浅水下等离子弧割炬,还可以作为一般等离子弧割炬。文中较详细地介绍了该割炬喷嘴的结构,列举了切割2.5～60mm厚不锈钢和10～23mm厚铝板的一些技术数据。本文还对等离子弧切割时产生的有害气体、粉尘及经济效果进行了分析。     

气流再压缩等离子弧焊接电弧行为

电弧等离子体行为对焊接接头组织结构和性能具有决定性作用,开展气流再压缩等离子弧特性研究对于指导先进材料的气流再压缩等离子弧焊接工艺和提高焊接接头质量具有重要意义. 针对气流再压缩等离子弧焊接新工艺,基于流体动力学和电磁理论,建立气流再压缩等离子弧数值分析模型,采用ANYSYS Fluent软件,通过C语言进行二次开发,定量计算等离子弧温度分布、流场分布、电势分布,分析压缩气对等离子弧温度场、流场、电弧电压的影响规律. 模拟结果表明,压缩气对喷嘴内的等离子弧温度分布基本没有影响,压缩气对喷嘴外的等离子弧具有拘束压缩作用;压缩气对等离子弧流场分布基本没有影响;压缩气能够提高电弧电压. 相同电流条件下,与常规等离子弧焊接相比,气流再压缩等离子弧焊接电弧穿透能力有望提高.     

水再约束等离子弧加工的形式与改进

针对现有水再约束等离子弧加工中存在容易断弧等问题，提出了把水射流“焦平面”与被切割工件上表面重合的水再约束方案，并分析了该方案中再约束水流量对弧柱稳定性及切口质量的影响。     

高频焊螺旋管的空气等离子弧切割

将水再压缩式空气等离子弧切割法用于高频焊螺旋管生产线上,明显地提高了切割速度,降低了原材料消耗,从而提高了生产效率并降低了生产成本。为实现随机切割而研制的刀轮式夹管器,结构合理、运行轻便、性能可靠,适用于各种规格螺旋管的随机切割。     

水压缩弧等离子切割枪的改进

我厂1978年研制成功的水压缩弧等离子切割工艺,具有电弧能量集中、切口质量好(切口窄,在一定厚度内表面光滑而无挂渣)等特点。在长期应用水压缩弧等离子切割工艺过程中,由于认识到原切割枪(参见《焊接》1978,№3,P24)在结构上存在下列不足之处:零件多、装拆不便、喷嘴形状复杂、易漏     

Relationship between plasma arc cutting acoustic and cut quality

Abstract

The tremendous acoustic signal exiting during the plasma arc cutting process includes a lot of information about this process and has a close relation with cut quality. To investigate the relationship between the plasma arc cutting acoustic and cut quality, a number of experiments have been carried out. In the present study, cut quality by plasma arc is described by top and bottom kerf widths, bevel angle, and attached dross state, and the relationship between the evaluation items for cut quality and the SPL (sound pressure level) of the cutting acoustic is investigated in detail. It is shown that the SPL reaches a maximum as the bottom kerf width equals the diameter of the plasma arc potential core. The attached dross and kerf widths in a state of free dross obviously affect the low and high frequency components of the plasma arc cutting acoustic, respectively. These results also suggest the possibility of designing an acoustic-based monitoring system for the plasma arc cutting process.     

Laser Cutting of Multilayered Kevlar Plates

Laser cutting of Kevlar plates, consisting of multilayered laminates, with different thicknesses are carried out. A mathematical model is developed to predict the kerf width, thermal efficiency, and specific energy requirements during cutting. Optical microscopy and Scanning Electron Microscopy (SEM) are employed to obtain the micrographs of the cutting sections. The kerf width size is measured and compared with the predictions. A factorial analysis is carried out to assess the affecting parameters on the mean kerf width and dimensionless damage sizes. It is found that the kerf width and damage sizes changes sharply when increasing cutting speed from 0.03 to 0.08 m/s. Thermal efficiency of the cutting process increases with increasing thickness and cutting speed while specific energy reduces with increasing thickness. The main effects of cutting parameters are found to be significant on the mean kerf width and dimensionless damage sizes, which is more pronounced for the workpiece bottom surface, where locally distributed char formation and sideways burning are observed.     

LG8—25型空气等离子弧切割机切割工艺性能测试

空气等离子弧切割工艺是值得推广的热切割新技术。文内从介绍该工艺和设备的最佳切割参数、割口质量评定以及环境污染测定,确认该工艺与设备允许在自然通风条件下能正常切割。     

金刚石线锯切割绝缘陶瓷的切缝精度研究

为了探寻一种切缝窄、切缝轮廓平直的金刚石线锯切割工艺,将电火花线切割机床改装为金刚石线锯切割机床,并进行了金刚石线锯恒力进给切割陶瓷的实验,探究了丝速和配重对切缝宽度和切缝轮廓平直度的影响;用光学显微镜测量切缝宽度,并观察切缝轮廓的平直度。实验结果表明:随着丝速的增大,切缝宽度变化不明显,随着配重的增大,切缝宽度明显减小;随着丝速的增大,切缝轮廓逐渐出现锯齿状,随着配重的增大,切缝轮廓发生弯曲甚至崩碎。     

A study of abrasive waterjet cutting of metallic coated sheet steels

A study of Abrasive Waterjet (AWJ) cutting of metallic coated sheet steels is presented based on a statistically designed experiment. It shows that AWJ cutting is a viable technology for processing metallic coated sheet steels with good productivity and kerf quality. A scanning electron microscopy analysis indicates that micromachining and plastic deformation are the dominant cutting phenomena in sheet steel processing. Plausible trends and relationships between kerf characteristics and process parameters are discussed. It is found that an optimum water pressure together with small standoff distance between the nozzle and workpiece may be used, while the traverse speed should be selected as high as possible for through cuts in order to increase the cutting rate. Empirical models for kerf geometry and quality are finally established for the prediction and optimization of AWJ cutting performance.     

激光切割过程辅助气体动力学性能的数值模拟

激光切割过程中辅助气体的动力学性能对切缝形成过程具有重要影响.利用VOF算法和深度自适应激光热源,建立了能反映切割过程中辅助气体和切缝之间相互作用的多相流模型,结合切割试验对模型的有效性进行了验证.采用多相流模型分析了从打孔到稳定切割过程中切缝形貌、辅助气体动力学性能和温度场分布.计算结果表明,在未切透阶段,受切割前沿形状和切割深度等的影响,辅助气体动力学性能不断发生变化;当切割过程稳定后,辅助气体流场几乎不发生变化,切缝形状和温度场也不再改变;所建模型能够有效反映辅助气体动力学性能对切割深度和切缝宽度的影响.     

CO2 laser cut quality of 4130 steel

Samples of 4130 steel were cut on a CO₂ laser cutting system and the combined effects of power and feed rate on kerf width, surface roughness, striation frequency and the size of heat affected zone (HAZ) have been studied. Regression analysis was used to develop models that describe the effect of the independent process parameters on laser cut quality. For the range of operation conditions tested, it was observed that power had a major effect on kerf width and size of HAZ, while feed rate affects were secondary. On the other hand, surface roughness and striation frequency were affected most by feed rate. At low power levels, the smallest kerf width and HAZ are obtained and the effect of feed rate is moderate. Low feed rates gave good surface roughness and low striation frequency. For optimum cut quality, kerf width, HAZ and surface roughness are kept at a minimum. However, operating conditions that satisfy these requirements while maintaining high productivity could not be identified.     

304不锈钢水下药芯割丝电弧切割机理

药芯割丝电弧切割(flux-cored wire arc cutting,FCAC)作为一种高效、低成本、安全的水下切割方法,具有广阔的应用前景. 由于水下复杂环境的干扰,该方法的不锈钢切割机理仍不明确,采用工艺试验、水下观测和数值模拟相结合的方法对水下割口成形机理进行研究. 首先通过工艺试验确定水下切割相关特征参数;其次采用半椭球体热源模拟切割热源,并根据试验观测设置热源的运动和切换方式;最后对工件进行网格划分和水下边界条件设置,使用生死单元法动态模拟切割中熔融金属的去除;对工件上特定点的模拟和实际温度以及切割后的模拟割口与实际割口形貌进行了研究对比,验证该方法数值模拟的准确性. 结果表明,水下电弧切割不锈钢割口主要分为“/ \”型、“| |”型和“\ /”型3种形貌. 通过高速摄像观察得出,水下不锈钢切割过程由多个周期型连续穿孔过程组成,通过模拟进行验证,对割口成形过程进行有效预测,有助于进一步优化工艺并进行有效控制.     

AN EXPERIMENTAL STUDY OF CO 2 LASER CUTTING OF METALLIC COATED SHEET STEELS

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Analysis and prediction of laser cutting parameters of fibre reinforced plastics (FRP) composite materials

A theoretical model is presented considering the spatial distribution of the laser beam, interaction time between the laser and the work material, absorption coefficient of the laser beam at the laser wavelength and the thermal properties of the material. It is assumed that the laser energy is absorbed through the entire thickness of the material. The developed model predicts the various parameters in laser cutting of composite materials such as kerf width at the entry and at the exit, material removal rate and energy transmitted through the cut kerf. The theoretical analysis also determines the position of the beam with respect to the cutting front. Experiments for different laser and material combinations to evaluate the effects of cutting parameters on the cut quality were carried out to compare with the predicted results. The results obtained show very good agreement.