Intelligent Sensors for Atomization Processing of Molten Metals and Alloys
ABSTRACT We briefly introduce the principles of atomization processing of molten metals and alloys, discuss potentially applicable instrumentation, and propose opportunities for developing intelligent sensors for monitoring and control of the process. Particle size and velocity are considered the two most important variables to monitor and control the atomization process. Several on-line sensors suitable for atomization of molten metals and alloys are compared: laser light scattering methods using small angle scattering analysis, moderate angle scattering analysis, and doppler analysis, electrical methods using surface ionization and triboelectric charging, and image analysis. The isokinetic sampling probe is introduced as a direct method to sample powders at the desired point in the atomized spray. Prospects and problems of integrating instruments based on these principles into intelligent processing of materials (IPM) scenarios are discussed.
Ensemble and Single Particle Laser probe sizing results for gas atomized zinc powders
On-line characterization of powder and droplets during gas atomization of molten metals and alloys offers extensive opportunities for real-time process monitoring and control. The capability to make on-line measurements can significantly reduce tedious and costly powder classification, which, currently, is always carried out subsequent to the atomization process. Two laser-based particle sizing instruments, the EPCS (ensemble instrument) and PCSV (single particle instrument), were used during gas atomization of zinc with a double Coanda nozzle configuration. The laser instruments were positioned in the duct leading from the bottom of the atomization tower to the powder collection cyclone. The effect of gas to metal ratio on particle size was studied by varying the atomization gas pressure from 0.69 MPa to 1.03 MPa
Laser-Based Single Particle Counters For In Situ Particulate Diagnostics
Optical techniques for particulate analysis have inherent and significant advantages over those conventional methods which involve batch sampling and subsequent analysis. Optical particle diagnostic techniques can be divided into three broad categories: ensemble methods which analyze the integrated optical properties of an assembly of particles; single particle counters (SPC) which analyze individual particles; and, finally, imaging techniques based on photography or holography. This paper is primarily concerned with laser-based single particle counters applicable to in situ sizing of particles and droplets in the diameter range 0.1 um to 1 mm. Theoretical principles of the various single particle counter designs are discussed with emphasis on comparing performance characteristics and relative advantages. The effects of size-dependent sample space, nonspherical particles, unknown particle composition, and applicable size ranges are considered.