Spray forming: Controlling the atomization result with regard to particle properties

Spray forming is a new production process for manufacturing semi-finished metal products. The procedure combines the liquid metal atomization with the compaction event of the generated metal droplets on a substrate. During spray forming, the heat emission of the molten metal particles is one of the most important transfer operations defining the thermal conditions in the spray and deposit. Definite thermal conditions throughout the manufacturing process lead to fine equiaxed grain structures and therewith to characteristic and desired material properties. Thus, in particular, the disintegration of the molten metal occurring during spray forming is an essential step. In this work, the PDA technique was used to characterize the atomization result based on the particle properties. Applying this optical measurement technique to the spray-forming process, the size and the velocity of the particles forming the spray can be determined. In addition, process quantities such as particle flux and mass flux can be evaluated considering the PDA data. Further, extending PDA to an on-line measurement system, process analysis even very close to real time is possible, i.e. in our experiments an on-line PDA is employed to monitor the spray forming process. Thus PDA can be classified as an important part of a detailed on-line process control procedure complementing the usual data acquisition of process temperatures and pressures.