等离子弧制备金属粉末装置研制及粉末性能研究
发布时间：2018-11-03 14:06
【摘要】：以“3D打印”为代名词的增材制造技术方兴未艾,但随着应用领域日益广泛,也技术面临着材料种类单一,兼容性低的问题。所用粉末材料制备技术的匮乏成为了“3D”打印无法大规模工业应用的瓶颈,使得这一新技术仍有很多问题有待解决。相较于传统工业用粉末材料,增材制造要求所用粉末粒度在100μm以下、呈实心圆球状、粒度要达到一定的比例的分布,且每一个球形小颗粒的元素分布要与原材料相近而不能有明显偏析。这些苛刻要求成了摆在多种传统制粉方法面前的挑战。本文综合分析“增材制造”对粉末材料所提技术要求,基于熔化极气体保护焊与等离子切割原理,同时借鉴气体动力学等技术。创新性地提出了利用等离子弧同向雾化金属丝(棒)状材料,配合反用“拉瓦尔管”原理的“扩容室”喷嘴,制备了不锈钢、镍基合金、钛合金等多种球状微米级金属粉末。同时对粉末进行显微形貌、粒度分布、成分与物相分析,机理研究所得结果如下:(1)单个和多个电极等离子弧同向雾化制粉,充分发挥了等离子弧高温、高能量密度、高气动性等优点,更直接地实现了对材料的快速熔化与其后液滴的破碎细化;(2)根据超音速与亚音速等离子射流的特点,反用火箭发动机喷管原理,根据能量方程、解微分方程的龙格-库塔法,利用流体经过变截面区域速度、温度与压力变化规律计算出较合理的扩容室喷嘴外形,充分发挥了延长材料冷却时间,同时加速吹出等离子弧高温区的作用。将原本金属熔滴的凝固过程分解成两个可变速度的步骤;(3)对于外径4-10mm的丝状材料,在装置输出电流90A-110A、输出气体压力0.40MPa-0.55MPa、气体流量35L/min-55L/min;在距离等离子射流出口70mm-75mm处放置扩容室喷嘴,扩容室最小截面处半径20.00mm、最大处半径29.02mm、截面半角15°时。可使得制备的粉末材料外形更接近球形,且颗粒呈现快速凝固的组织形貌。粉末平均粒径57.96μm、粒度分布于30μm-100μm之间,较好实现了大小搭配;粉末松装密度2.50g/cm3,振实密度2.72 g/cm3。
[Abstract]:The technology of "3D printing" is in the ascendant, but with the increasing application field, the technology is faced with the problem of single material type and low compatibility. The shortage of the preparation technology of powder materials has become the bottleneck of "3D" printing which can not be applied on a large scale, so there are still many problems to be solved in this new technology. Compared with the traditional industrial powder materials, the powder size required for the material increasing production is less than 100 渭 m, which is like a solid ball, and the particle size should be distributed in a certain proportion. The element distribution of each small spherical particle should be similar to that of raw material without obvious segregation. These harsh requirements have become a challenge in front of a variety of traditional pulverizing methods. Based on the principle of gas shielded welding and plasma cutting, the technical requirements for powder materials in "material increasing manufacture" are analyzed synthetically in this paper. At the same time, the techniques such as gas dynamics are used for reference. By using plasma arc codirectional atomizing wire (rod)-like material and the "expansion chamber" nozzle of "Laval tube" principle, a variety of spherical micron metal powders, such as stainless steel, nickel base alloy, titanium alloy and so on, have been prepared. At the same time, the microstructure, particle size distribution, composition and phase of the powder are analyzed. The results are as follows: (1) single and multiple electrode plasma arcs are atomized in the same direction to make powder, giving full play to the high temperature and high energy density of plasma arc. The advantages of high aerodynamic performance, such as the rapid melting of materials and the subsequent breakup and refinement of droplets, are realized more directly. (2) according to the characteristics of supersonic and subsonic plasma jet, the inverse rocket engine nozzle principle, according to the energy equation, the Runge-Kutta method for solving differential equations, the velocity of fluid passing through the region of variable cross section is used. The change of temperature and pressure gives a reasonable shape of the nozzle in the expansion chamber, which can extend the cooling time of the material and accelerate the blowing out of the high temperature region of the plasma arc at the same time. The solidification process of the original metal droplet is decomposed into two variable speed steps; (3) for filamentary material with outer diameter 4-10mm, the output current is 90A-110A, the output gas pressure is 0.40MPa-0.55MPa, the gas flow rate is 35L / min-55L / min; The nozzle of the expansion chamber is placed at the 70mm-75mm exit of the plasma jet. The minimum section radius of the expansion chamber is 20.00 mm, the maximum radius is 29.02 mm, and the cross-section angle is 15 掳. The morphology of the prepared powder materials is more spherical and the particles exhibit the microstructure of rapid solidification. The average particle size of the powder is 57.96 渭 m and the particle size distribution is between 30 渭 m and 100 渭 m. The powder bulk density is 2.50 g / cm 3 and the vibrational density is 2.72 g / cm 3.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.3;TP391.73
[Abstract]:The technology of "3D printing" is in the ascendant, but with the increasing application field, the technology is faced with the problem of single material type and low compatibility. The shortage of the preparation technology of powder materials has become the bottleneck of "3D" printing which can not be applied on a large scale, so there are still many problems to be solved in this new technology. Compared with the traditional industrial powder materials, the powder size required for the material increasing production is less than 100 渭 m, which is like a solid ball, and the particle size should be distributed in a certain proportion. The element distribution of each small spherical particle should be similar to that of raw material without obvious segregation. These harsh requirements have become a challenge in front of a variety of traditional pulverizing methods. Based on the principle of gas shielded welding and plasma cutting, the technical requirements for powder materials in "material increasing manufacture" are analyzed synthetically in this paper. At the same time, the techniques such as gas dynamics are used for reference. By using plasma arc codirectional atomizing wire (rod)-like material and the "expansion chamber" nozzle of "Laval tube" principle, a variety of spherical micron metal powders, such as stainless steel, nickel base alloy, titanium alloy and so on, have been prepared. At the same time, the microstructure, particle size distribution, composition and phase of the powder are analyzed. The results are as follows: (1) single and multiple electrode plasma arcs are atomized in the same direction to make powder, giving full play to the high temperature and high energy density of plasma arc. The advantages of high aerodynamic performance, such as the rapid melting of materials and the subsequent breakup and refinement of droplets, are realized more directly. (2) according to the characteristics of supersonic and subsonic plasma jet, the inverse rocket engine nozzle principle, according to the energy equation, the Runge-Kutta method for solving differential equations, the velocity of fluid passing through the region of variable cross section is used. The change of temperature and pressure gives a reasonable shape of the nozzle in the expansion chamber, which can extend the cooling time of the material and accelerate the blowing out of the high temperature region of the plasma arc at the same time. The solidification process of the original metal droplet is decomposed into two variable speed steps; (3) for filamentary material with outer diameter 4-10mm, the output current is 90A-110A, the output gas pressure is 0.40MPa-0.55MPa, the gas flow rate is 35L / min-55L / min; The nozzle of the expansion chamber is placed at the 70mm-75mm exit of the plasma jet. The minimum section radius of the expansion chamber is 20.00 mm, the maximum radius is 29.02 mm, and the cross-section angle is 15 掳. The morphology of the prepared powder materials is more spherical and the particles exhibit the microstructure of rapid solidification. The average particle size of the powder is 57.96 渭 m and the particle size distribution is between 30 渭 m and 100 渭 m. The powder bulk density is 2.50 g / cm 3 and the vibrational density is 2.72 g / cm 3.
【学位授予单位】：长春工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.3;TP391.73
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