激光熔覆成形薄壁件工艺基础研究

发布时间：2018-05-15 22:15

本文选题：激光熔覆 + 薄壁件　；参考：《新疆大学》2017年硕士论文

【摘要】：英国《经济学人》杂志认为增材制造技术将与其他数字化技术一起推动第三次工业革命。激光熔覆成形能够制造全致密金属零件的增材制造工艺。采用激光熔覆技术成形薄壁件,可以得到组织致密和性能优良的薄壁件。使用激光熔覆3D打印及再制造系统进行熔覆成形实验研究,采用搭建水冷实验工作台进行实验。单道熔覆成形是薄壁件成形的基础。激光熔覆单道熔覆轨迹的高度和宽度、熔池深度主要取决于激光功率、送粉速率、扫描速度等熔覆工艺参数,研究得到单道熔覆轨迹几何尺寸和激光熔覆过程中激光功率、送粉速率和扫描速度之间的关系。通过正交实验分析工艺参数对熔覆层宽度和高度的影响程度大小,并建立回归方程。本文成形的薄壁件为激光熔覆单道多层成形。激光熔覆成形的薄壁件零件是单道熔覆轨迹逐层堆积起来形成的,通过实验选择合理的工艺参数和路径,由层高控制成形过程中Z轴提升量,成形直薄壁件和曲面薄壁件,解决了成形中粘粉、坍塌、“起点高”“尾缩”和裂纹现象,得到表面良好的薄壁件。研究曲率不同的圆弧成形的薄壁件高度,曲率小的高度较稳定,曲率大的高度变化明显;成形薄壁件表面质量的测定实验,并进行方差分析,送粉速率对表面质量影响最大。成形薄壁件的金相组织良好,激光熔覆成形的薄壁件试样拉伸强度为573.7MPa,优于不锈钢热轧钢板的拉伸强度。对单道熔覆温度进行实验,研究得到基板温度变化与工艺参数之间的关系。采用热电偶和热成像仪两种方式测得薄壁件成形过程中温度变化,并拟合比较温度曲线,热成像仪所测温度偏低。金属熔覆成形过程中,是多场耦合的复杂过程,将温度场的数值模拟和温度场实验相结合,能够更加直观、全面地研究温度场的变化过程。通过温度场数值模拟的方法对单道熔覆成形和薄壁件过程中温度场进行模拟并与实验对比,对比拟合数据基本符合,采用相同模拟参数对薄壁件成形进行模拟,研究得到成形中温度累积效应和变化规律。
[Abstract]:The Economist believes that the technology will drive the third industrial revolution along with other digital technologies. Laser cladding can be used to fabricate all dense metal parts. Thin-walled parts with compact structure and excellent properties can be obtained by laser cladding technology. The laser cladding 3D printing and remanufacturing system was used to study the cladding forming experiment, and the water cooling experiment bench was built. Single-pass cladding is the foundation of thin-wall forming. The height and width of the laser cladding path and the depth of the melting pool are mainly determined by laser power, powder feeding rate, scanning speed and other technological parameters. The geometric dimension of the single channel cladding trajectory and laser power during laser cladding are studied. The relationship between powder feeding rate and scanning speed. The influence of process parameters on the width and height of cladding was analyzed by orthogonal experiment, and the regression equation was established. The thin-walled part formed in this paper is laser cladding single-pass multi-layer forming. The thin-walled parts formed by laser cladding are stacked up layer by layer with single-pass cladding track. Through experiments, reasonable technological parameters and paths are selected, Z axis lifting amount is controlled by layer height, and straight thin-walled parts and curved thin-walled parts are formed. The phenomena of sticking powder, collapsing, "starting point height", "tail shrinkage" and crack are solved, and the thin wall parts with good surface are obtained. The paper studies the height of thin-walled parts with different curvature, the height of small curvature is stable, the height of big curvature changes obviously, and the measurement of surface quality of thin-walled parts is carried out, and the analysis of variance shows that the powder feeding rate has the greatest influence on the surface quality. The tensile strength of the thin wall formed by laser cladding is 573.7 MPa, which is better than that of the hot rolled stainless steel plate. The relationship between substrate temperature and process parameters was studied by experiments on single pass cladding temperature. The temperature change of thin-walled parts during forming was measured by thermocouple and thermal imager, and the temperature curve was fitted and compared. The temperature measured by thermal imager was lower than that measured by thermocouple. The process of metal cladding forming is a complex process of multi-field coupling. Combining the numerical simulation of temperature field with the experiment of temperature field, the process of temperature field change can be studied more intuitively and comprehensively. The temperature field in the process of single-pass cladding forming and thin-wall forming is simulated by numerical simulation of temperature field and compared with the experiment. The comparison and fitting data are basically consistent, and the same simulation parameters are used to simulate the thin-walled forming. The cumulative effect and variation law of temperature are obtained.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG665

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