Physical and Technological Features of Mechanoactivation of Powder Particles Formed during Hydro-Vacuum Dispersion of Metallic Melts

Abstract

A study has been conducted on the hydro-vacuum dispersion process of metal melts using gray cast iron SCh20 (in Russian nomencluture; 3.3–3.5C, 1.4–2.4Si, 0.7–1Mn, <0.15S, <0.2P in wt %)—an analogue of GG20. It has been revealed that the main factor conditioning the mechanoactivation of formed particles is their solidification in a fibrous non-equilibrium structural-tensioned state. This state is achieved by flattening and asymmetric twistedness of droplets that are detached from the liquid metal in the disperser under volumetric impact of shock-pulsating waves of hydraulic discharge. The degree of particle activation was found to depend exponentially on their dispersion and specific surface area. These parameters determine the degree of asymmetry of shear deformations and the amount of accumulated energy. In turn, the size dispersion and specific surface are significantly influenced by physical and technological factors such as the specific flow rate and pressure of injected water, the thickness and the elevation angle of the hydro shell of the vacuum diffusion funnel, the diameter of the dispersed melt jet passed through it, and its superheating temperature. The control of these parameters makes it possible to smoothly adjust the key ratio “liquid metal: water” and set up the dispersion process with the highest possible degree of size dispersion and activation of the resulting powder.