【作者】 周乐；

【导师】 陈培锋；

【作者基本信息】 华中科技大学 ， 光电信息工程， 2013， 博士

【摘要】 冷轧金属薄板在汽车、家电、建筑、装饰等行业需求日益增加,同时对于薄板的冲压成型性能和外观涂镀性能要求也越来越高。通过对轧制金属薄板的轧辊表面进行毛化,经过轧制过程将辊面的微形貌组织复印到薄板表面,从而实现对轧制金属薄板表面质量的控制。研究表明,相较喷丸毛化技术和电火花毛化技术,对辊面加工的激光毛化技术具有加工精确、清洁、均匀性好等优点,且激光毛化辊工作寿命长,轧制的金属薄钢板兼顾深冲成型和涂镀性能,可用于高档汽车和家电外用漆面板。但是,现有单头激光毛化技术的加工效率难以满足大型冷轧企业的生产需求,为了缩短加工时间,往往采用低毛化点密度加工辊面,影响了其轧制薄板的表面质量,从而限制了激光毛化技术的推广和应用。针对单头激光毛化存在的效率瓶颈问题,本论文提出了基于多棱镜扫描分光脉冲调制原理的多头CO2激光毛化技术方案。全文的主要工作内容如下：(1)首先介绍了多棱镜扫描分光脉冲调制的原理,将一束连续高功率激光经过旋转多棱镜扫描分光后产生多路高功率高重复频率脉冲激光束,其单路脉冲输出频率可达30kHz,多路激光脉冲同时加工,加工效果一致,成倍提高毛化效率。(2)采用“内嵌基模高斯光束”的方法推导了扫描高斯光束在近轴条件下经过多棱镜扫描分光脉冲调制光学系统后在输出平面上的光强分布,并根据分布特征分析了实际扫描高斯光束的聚焦特性,聚焦光斑近似为圆形。由于扫描高斯光束聚焦光斑在聚焦镜几何焦面外随扫描角运动,因而讨论了聚焦光斑中心运动与辊面加工区域旋转同步的条件,实现聚焦点跟踪技术,从而可以在辊面获得圆形毛化点,改善了单头斩光盘CO2激光椭圆毛化点所导致的轧制钢板表面各向异性的问题。(3)根据毛化加工在效率、表面粗糙度、微形貌参数等方面的要求对多头C02激光毛化加工系统进行了设计,分析了多棱镜和聚焦镜等主要光学器件的设计参数以及加工飞行光路对聚焦效果的影响,并采用几何光学扫描模型简化聚焦点跟踪技术参数范围的分析。(4)通过工艺实验研究了多头CO2激光毛化的加工参数范围以及功率和脉宽等毛化工艺参数对于辊面表面粗糙度和微形貌几何参数的影响规律,并对毛化后辊面进行了金相显微分析和硬度测试,毛化后辊面硬度≥HV800。(5)对双头激光设备的实践生产情况进行了总结,该设备在具有稳定性好,运营成本较低,加工效率高的特点,毛化加工后辊面表面粗糙度波动范围在±0.2μm内,满足辊面均匀性要求。更多还原

【Abstract】 Cold-roll steel sheet is widely used in automobile, appliance, construction and decoration industry, and the requirement for its forming ability and painting quality is also increasing. The surface quality of cold-roll steel sheet is controlled through surface texturing of cold roll whose micro organizations of surface will be printed into the surface of steel sheet during the rolling process. Comparing with the SBT(shot blast texturing) and EDT(electrical discharging texturing) technology, research shows that laser texturing is more precise, clean and uniform, meanwhile its textured roller has longer working duration and the laser texturing cold roll steel sheet has both good forming and painting quality, thus can be used as vehicle and appliance outer panel. However, the efficiency of single-head laser texturing is not sufficient to meet the requirement of large cold-roll enterprise. In order to shorten the texturing time, the surface crater density of single-head laser texturing is usually low and thus has compromised the quality of cold roll steel sheet, which in turn affect the application of laser texturing technology. In order to solve the problem of low efficiency of single-head laser texturing, a multi-heads CO2laser texturing technology based on pulse beam modulation by polygon scanning is proposed. The major content of this thesis is as following:(1) The principle of modulation of a high power continuous laser into several high repetition pulse lasers by polygon scanning is introduced, and the repetition rate is up to30kHz.(2) By using "Embed fundamental Gaussian beam", the distribution of light intensity of the focusing spot on the output plane is derived and the transmission and focus of pulse beam through the optical system is analyzed. The focusing spot is constantly on the move outside the focusing plane while the roller is rotating, and the condition for synchronization is discussed. Therefore, round texturing crater can be obtained instead of elliptical ones which will influence the of steel sheet surface uniformity.(3) Multi-heads texturing system parameters are determined according to the requirement of texturing condition. The design parameters of focusing lens and rotating polygon are discussed and the influence of flying optics on the focusing spot is analyzed. A geometrical optical model is introduced to simplify the analysis of synchronization between focusing spot and roller surface to determine the appropriate off-focus parameters.(4) The influence of texturing parameters such as laser power and pulse width on surface roughness and surface topography parameters are studied through laser texturing experiments. Metallographic analysis and hardness tests are performed on the textured surface of roller, and the average hardness is above HV800.(5) The practice of two-heads CO2laser texturing device is introduced and the device possesses features such as low cost, stability and high efficiency. The fluctuation of roughness of textured roller surface is between±0.2μm and meets the requirement of roller surface uniformity.更多还原