6kW大功率光纤激光器切割6mm不锈钢工艺

采用6kW光纤激光器切割6mm不锈钢,分析了不同的激光切割工艺参数,如激光功率、切割速度、切割气体种类及压力、焦点位置以及激光倾斜角度对切割质量的影响。以切缝背部的挂渣情况作为评判切缝质量的标准,结果表明:增大切割气体压力可以降低底部挂渣以及粗糙度,但是压力达到一定程度后,挂渣和粗糙度没有明显变化;在切割厚板时,焦点位置位于工件的下部并且越靠近底表面,效果越好;光束入射倾角超过25°,切割质量变差,甚至切不透。通过大量的切割工艺试验得到在切割气体为N2,激光功率为3.3kW,切割速度为2.0m/min,离焦量为-4mm,气体压力为1.7MPa,喷嘴到工件表面距离为1.0mm时,切割质量最佳。     

光纤激光切割对医用金属L605管切面质量的影响

采用不同的光纤激光切割工艺参数(功率、频率、脉宽、切割速度、氧气压力、喷嘴距离)对?1.8 mm(壁厚0.1 mm)的L605管材进行了切割。将切割试样酸洗处理后,用3D共聚焦显微镜测量切缝宽度和切面粗糙度,用扫描电镜(SEM)观察切面的微观形貌。结果表明:激光功率增大,切缝宽度增大,切面粗糙度先减小后增大;激光频率、脉宽增大,切缝宽度和切面粗糙度都增大;切割速度增大,切缝宽度减小,切面粗糙度增大;氧气压力提高,切缝宽度增大,切面粗糙度降低;喷嘴距离为0.25 mm时,切缝宽度和切面粗糙度均最小。激光功率、频率、脉宽、切割速度、氧气压力、喷嘴距离改变使切面上的切割条纹发生改变以及出现残渣、金属屑、重铸层等。     

大功率激光水下切割用喷嘴设计

综合考虑激光光束尺寸要求和拉瓦尔喷嘴的设计原理,对喷嘴的稳定段、收缩段、喉口及扩张段进行了设计.稳定段尺寸主要由激光切割枪整体尺寸限制确定,收缩段连接稳定段与喉口段,采用相切圆弧过渡方式,为保证激光顺利通过喉口部位,喉口段直径大于激光光斑直径,扩张段采用直线扩张方式,鉴于切缝宽度限制,扩张角不应过大.根据设计尺寸制造了超音速拉瓦尔喷嘴,喷出氧流速度及挺度得以改善,在激光水下切割试验中,采用局部排水法,较大氧气流量条件下顺利实现了深水条件下30 mm厚碳钢板的高效激光切割,与会聚型喷嘴相比,切割效果改善明显.     

钛合金的激光切割

研究了不同辅助气体和工艺参数对激光切割钛合金板的影响，分析了激光切割切缝的断面特征和热影响区特点。试验结果表明，用氩气作辅助气体，切割质量最好；激光功率和切割速度对切缝宽度和热影响区宽度有一定影响；切缝断面可分为形貌不同的两个区，两区之间有明显界线；切缝上表面和下表面热影响区宽度不同，特点为上窄下宽。     

中厚钢板大功率固体激光切割模式

对30mm厚钢板进行大功率固体激光切割试验,研究了主要工艺参数对切割特性的影响,揭示了中厚板激光切割的传热机理.结果表明,中厚板激光切割时呈现窄缝和宽缝两种切割模式,氧气压力和激光离焦量对窄缝-宽缝切割模式转变有很大的影响.窄缝横截面呈现出较平直的"I"型,宽缝横截面呈现出上宽下窄的"V"型.     

铝合金脉冲固体Nd：YAG激光切割及其对比试验

利用高功率脉冲固体Nd:YAG激光和空气等离子弧分别对4mm厚的5A06铝合金板材进行了切割试验.探讨了工艺参数对激光切割质量的影响,得出结论,激光功率、脉宽、频率和离焦量对切缝宽度影响较大,而切割速度、辅助气压的影响很小.通过光学显微镜和扫描电子呈微镜观察分析切缝宏观形貌及微观组织,结果表明,激光切缝窄钿平直,垂直度0.28mm,切面波纹浅,没有明显的热影响区;与空气等离子弧的切割效果进行对比,后者切缝较宽,大约是激光切缝的4倍,切面易氧化,波纹较深,且切割面有大量微裂纹存在.     

钨合金薄板单模光纤激光切割

钨合金是高熔点材料,其激光热切割是难点。利用单模光纤激光作为切割热源,切割板厚0.9 mm的钨合金(合金成分:93W-4.9Ni-2.1Fe),探讨激光切割工艺参数及其切口质量。试验结果表明,在切割激光功率500 W、切割速度0.5 m/min、切割气体(氮气)压力0.8 MPa的条件下,切割缝宽约102μm,切割缝质量较好。在此激光切割工艺参数的基础上,若降低切割速度,切割缝宽度增大;若提高切割速度,无法获得良好的切割质量;若降低切割气体压力,无法获得良好的切割质量;若增加切割气体压力,对减小切割缝宽度及改善切割质量基本没有影响。     

低碳钢薄板氧-乙炔火焰手工气割工艺研究

针对低碳钢薄板氧-乙炔火焰手工气割过程中出现的质量问题,分析了影响薄板气割质量的氧气纯度、预热火焰的性质及能率、氧气压力、切割速度、割嘴到工件表面的距离等工艺参数.结果表明:薄板气割时,氧气压力在0.2～0.25MPa之间、纯度应大于98.5%,预热火焰选取轻微的碳化焰及相对较大的能率,焊矩的后倾角在30°～45°之间随着板厚的减小而增加,切割速度较快,割嘴到工件表面的距离为10～15mm时缺陷不易产生,切割质量较好.     

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。     

钛合金的激光切割

介绍了用1.5kWCO_2激光器切割厚度为1.6～4mm的TC_4钛合金板材,影响切割速度及切割质量的主要工艺因素。采用了氩气及压缩空气两种辅助气体。观察了切缝的形貌及测量了切缝宽度;并对热影响区(HAZ)进行了金相及显微硬度的分析。两种不同的辅助气体切割钛合金对切缝质量无明显的影响,而用压缩空气的切割速度比用氩气切割速度高。     

干式切削20Cr表面粗糙度和残余应力研究

针对低渗碳钢20Cr材料制作齿轮轴等零件表面质量要求,如表面粗糙度低于1.6μm,零件表面耐疲劳性能良好。试验采用干式切削20Cr钢材方式,在背吃刀量固定的工序中,研究切削速度和进给量对20Cr材料表面粗糙度的影响,同时结合有限元技术,分析切削速度和进给量对20Cr表面残余应力的影响。干式切削试验采用单因素方法,进行多组干式切削20Cr工件,对比分析各组工件表面粗糙度,结果表明当进给量较小时,切削速度对工件表面粗糙度有显著影响,表现为表面粗糙度随切削速度增加而变大;当切削速度一定时,进给量增加导致表面粗糙度变大,并且进给量对表面粗糙度的影响大于切削速度;对于工件表面残余应力,增加切削速度和进给量均导致残余应力变大,因而较小的切削速度和进给量可以降低工件表面残余应力,改善应力分布状态。     

Analysis of heat effects in laser cutting of steels

Efficient control of laser cutting processes is closely related to knowledge of heat effects in the cutting front and its surroundings. Similar to other machining processes using high power densities, in laser cutting processes it is very important to monitor the heating phenomena in the workpiece material due to heat input. In laser cutting processes with oxygen as an auxiliary gas, cutting energy is a combination of laser beam energy and the energy of the exothermic reactions occurring in the cutting front. The presence of oxygen in the process increases cutting efficiency, but also causes additional physical processes in the cutting front that render a more detailed analysis of the cutting phenomena difficult. The aim of this article is to analyze the emission of infrared rays from the cutting front with a photodiode, statistically analyze the temperature signals, and optimize the laser cutting process based on a critical cutting speed. The measured infrared radiation temperature signal was, on the basis of calibration, converted into a temperature that was related to the formation of macro- and microstructures and to the change in microhardness in the surface layer of the cut. On the basis of experimental results, it was proved that heat effects in the cutting front decisively influenced the quality of cut. Finally, factor analysis was used to establish statistical relations among variables of the laser system, variables of the cutting process, and geometrical characteristics of the cut.     

前混合磨料水射流切割参数对表面粗糙度的影响

采用前混合磨料水射流对Q235碳素结构钢进行切割实验,测量样品切口表面粗糙度;研究前混合磨料水射流的切割压力、喷嘴出口直径、切割靶距、切割速度和切割深度对样品切口表面粗糙度的影响规律;结合实验数据,建立表面粗糙度二次非线性回归预测方程。研究结果表明：前混合磨料水射流的切割压力、喷嘴出口直径与表面粗糙度呈负相关关系;切割靶距、切割速度、切割深度与表面粗糙度呈正相关关系;各因素的影响权重大小依次为：喷嘴出口直径、切割深度、切割压力、切割速度、切割靶距;影响表面粗糙度的实质因素为磨料流量和磨料能量;建立的表面粗糙度二次非线性回归预测方程的平均偏差为7.99%。     

Nano-second pulsed DPSS Nd:YAG laser striation-free cutting of alumina sheets

Lasers are extensively employed in cutting alumina sheets in the electronic industries. An important quality factor of laser cutting is striation (periodical lines) formation on the cut surfaces, which affects the surface roughness and geometry precision of laser cut products. The elimination of striation is important for laser cutting of alumina since it is necessary for denser circuit patterns and device miniaturisation. The present study demonstrates, for the first time, striation-free cutting of alumina sheets with 1 mm thickness using a 400 W high repetition rate nano-second pulsed DPSS Nd:YAG laser. The short pulse duration minimises heat damages. The effects of gas type, gas pressure, nozzle standoff distance, average laser power, cutting speed, and pulse repetition rate on striation characteristics were studied. The specific operating conditions for nano-second pulsed laser striation-free cutting were presented. The present study supports one of the existing theories for continuous wave (CW) laser striation-free cutting of metallic materials and further extends it to the pulsed laser striation-free cutting of ceramic materials. A mechanism of pulsed laser striation-free cutting was proposed, by which a model to predict the operating window for the nano-second pulsed laser striation-free cutting of alumina sheets was developed. The operating window predicted by the model was in agreement with the experiment.     

药芯割丝水下湿式电弧切割割口成形及热影响区组织分析

针对水下作业发展的需要,利用药芯割丝进行了水下湿式电弧切割试验,分析了水下电弧切割过程中切割电压、电流及切割速度对割口成形的影响规律,并研究了割口热影响区的显微组织.结果表明,药芯割丝水下电弧切割过程中电弧长度、割丝伸出长度在不停变化;割口下口基本较上口宽;随切割电压或电流的增大,割口上下宽度均有所增加;随切割速度的增大,割口下口宽度逐渐变小.同时发现,由于水下冷却速度较快,割口热影响区较窄,可分为重熔区、过热区、完全再结晶区与不完全再结晶区等区域.     

气割工艺分析

对切割氧气压力、切割速度及倾角、割嘴与割件距离等对切口表面的质量的影响因素进行了分析,并提出改进质量的措施。     

Experimental and numerical investigations of single abrasive-grain cutting

The present work will provide an in-depth analysis of the abrasive-grain cutting process using a combination of experimental observations and finite element simulations. The workpiece material was AISI 4340. The cutting tool was spherical in shape with a 0.508 mm radius and was fabricated from diamond. The experiments were conducted at cutting speeds of 5−30 m/s in 5 m/s increments and depths of cut from 0.3 to 7.5 μm. The analysis provided a comprehensive understanding of the abrasive-grain cutting process related to the friction between the cutting tool and the workpiece, the material mechanics of the workpiece, and the cutting mechanics of the operation. It was found that the normal forces increased as cutting speed increased due to strain-rate hardening of the workpiece and that the tangential forces decreased as cutting speed was increased due to a reduction in tool-workpiece friction and due to a change in cutting mechanics. The scratch profiles showed that the cutting mechanics changed as cutting speed was increased due to a reduction in material pile-up height. The approximate uncut chip thicknesses for the transitions from elastic, elastoplastic, and fully plastic cutting were identified and were found to increase as cutting speed was increased.     

An investigation of energy loss mechanisms in water-jet assisted underwater laser cutting process using an analytical model

The water-jet assisted underwater laser cutting processes has relatively low overall efficiency compared to gas assisted laser cutting process due to high convective loss in water-jet from the hot melt layer and scattering loss of laser radiation by the water vapour formed at the laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this cutting process has been formulated considering various laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum cutting speed, cut front temperature, cut kerf and the loss of laser power through different mechanisms as functions of laser power and water-jet speed. The predictions of cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of laser power loss. This also predicted that the percentage losses are lower for higher laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to laser heating and its removal by water-jet was experimentally studied. And, the cutting was done with modulated power laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW laser beam the modulated laser beam of same average power yielded higher process efficiency.     

基于LS-DYNA仿真的射流加工参数分析

目的通过LS-DYNA对磨料射流冲蚀切削进行仿真,研究相关工艺参数对切削参数的影响。方法采用磨料水射流对Al_2O_3陶瓷进行了单点冲蚀仿真和切削仿真研究,其中水和磨料粒子采用SPH方法建模,氧化铝陶瓷工件采用FEM方法建模,并通过SPH-FEM耦合算法,实现射流冲蚀切削过程的仿真。结果分析射流冲蚀过程仿真和切削过程仿真可知,射流加工前期,由于射流中磨粒碰撞与反弹,使壁面成不规则"V"型。初始阶段,切深随计算时间呈线性增加,同时壁面对磨粒产生制约作用,从而使加工处的孔深基本不再增加。由于磨粒在冲蚀处壁面底部的冲蚀作用,使凹坑底部宽度增加并迅速趋于稳定。同时切削仿真与冲蚀仿真也存在一定区别,主要由于切削过程设定了移动速度。结论将仿真结果与实验结果进行比较可知,切削深度随着泵压的增大而成线性增大,切深随磨料流量的增大而增大,随靶距和横移速度的增大而减小。其中切深与磨料流量、靶距、横移速度均为非线性关系,工件最大切深与计算时间不呈线性关系增长。