Metal Powder Production by Vapor Explosion

实验研究了金属熔滴与水之间的热相互作用。本研究的目的是揭示钢粉制造过程中的破碎和快速冷却机理，即所谓的水雾化过程。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。用辐射测温仪测量了熔融金属的温度。第二，用铁水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，另一种是扁喷嘴。在实验装置上安装了四个不同型号的喷嘴，并设置了一定的喷射角。四个喷嘴的方向被聚焦到流中心，熔融的金属被落到那里。研究了水温、喷嘴类型和喷嘴角度对粉末形状、粒度分布和产率的影响，铁水用石英玻璃喷嘴控制滴落位置的准确性较高。喷嘴出口直径分别为1 5 mm、2 5 mm、3 5 mm和5 5 mmφ。这些喷嘴的使用给我们带来了很好的产率，所生产的粉末的粒度主要在100μm以下。作为一种新的尝试，我们试图开发一种氧化锌粉末生产工艺。在传统工艺中，锌金属的汽化需要辅助加热。从热力学的角度考虑，可以通过回收反应热来实现自发氧化过程。我们对氧化锌的生产进行了初步试验。在空气流量为10L/min，气体流量为5L/min，热输入为1100W的条件下，自发反应时间为15min。通过显微镜观察，本研究生产的电能的大小大于商业上可获得的电能的大小。回收热量估计为280W。

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.