Metal Powder Production by Vapor Explosion

对金属液滴与水之间的热相互作用进行了实验研究。本研究旨在探讨水雾化炼钢过程中的破碎及快速冷却机制。实验装置由加热装置、注水系统和集粉部分组成。感应加热主要用于熔化金属。用辐射温度计测量金属液的温度。第一、第二，用铁液滴进行了水雾化实验。使用了两种类型的水喷嘴。一种是直喷嘴，另一种是扁平喷嘴。每种类型的四个喷嘴安装在实验单元上，具有一定的喷射角。四个喷嘴的方向集中在流中心，熔融金属滴向流中心。研究了铁水温度、喷嘴类型和角度对粉末形状、粒度分布和收得率的影响，采用石英玻璃铁水喷嘴，对落料位置进行控制，具有较高的确定性。喷嘴的出口直径为1.5、2.5、3.5和5.5 mmφ。使用这些喷嘴，我们带来了很好的收率，所生产的粉末的尺寸主要在100μm以下。作为一种新的尝试，我们尝试开发一种氧化锌粉末生产工艺。在常规方法中，需要辅助热来蒸发锌金属。从热力学角度考虑，通过回收反应热，实现自发氧化过程是可能的。对氧化锌生产进行了初步试验。在空气流量为10 L/min、氩气流量为5L/min、热输入功率为1100 W的条件下，自发反应持续时间为15 min。通过显微镜观察，本研究中产生的粉末的尺寸大于市售粉末的尺寸。热回收估计为280 W。

Thermal interaction between molten metal drop and water has been investigated experimentally. The purpose of this study is to disclose the mechanisms of fragmentation and rapid cooling in steel-powder-making process, so-called water atomization process. Experimental apparatus consists of heating unit, water injection system and powder-collection part. Mainly, induction heating is used to melt the metals. Temperatures of the molten metal are measured by the radiation thermometer.First, The second, water atomization experiments have been performed using a molten iron drop. Two types of water nozzle were used. One is straight nozzle and the other is flat nozzle. Four nozzles of each type were mounted on the experimental unit with some injection angle. The direction of four nozzles is focused to the stream center, to which the molten metal is dropped. Influence of water temperature, type and angle of nozzles on the shape, the size distribution and the yield rate of powders were investigated.The quartz glass nozzles for molten iron were used to control the dropping position with higher certainty. The exit diameters of the nozzles are 1.5, 2.5, 3.5 and 5.5 mmφ. The use of these nozzles brought us good yield rate and the size of produced powders ranges mainly below 100μm.As a new attempt, we tried to develop a zinc oxide power production process. In the conventional process, auxiliary heat is needed to vaporize zinc metal. By the thermodynamic consideration, it is possible to realize a spontaneous oxidizing process by recovering heat of reaction. We have made a preliminary experiment of zinc oxide production. Duration of spontaneous reaction was 15min in the condition of air flow rate of 10L/min, argon flow rate of 5L/min and heat input of 1100W. By microscopic observation, the size of power produced in the present study is larger than that of commercially available power. The recovery of heat is estimated to be 280W.