Investigators: Stephen D. Ridder and Frank S. Biancaniello

Technical Description:

Research in this project has focused on measurement and modeling tools for process understanding and control of metal powder produced by atomization. This research has resulted in the development of advanced process sensors and the incorporation of these sensors into an expert system based process controller. The processing tool chosen as a demonstration platform is the NIST Supersonic inert Gas Metal Atomizer (SiGMA). This research apparatus produces up to 30 kg of metal powder with average particle diameters ranging from 5 µm to 50 µm depending on alloy composition and processing conditions. The SiGMA system incorporates a controlled atmosphere chamber with vacuum pumping capabilities to limit powder contamination and enable processing with various gas mixtures. These features also provide an opportunity to apply advanced process control methods to regulate gas and metal flow rates within the atomizer, and control particle size and chemistry.

NIST research groups that have participated in this research effort include the Applied Systems Group of the Manufacturing Systems Integration Division (826.01), the Surface and Particle Metrology Group of the Precision Engineering Division (821.06), the Fluid Flow Group of the Process Measurements Division (836.01) and the Metallurgical Processing Group of the Metallurgy Division (855.14). The NIST scientists collaborated in this work with representatives from Ampal/Metallurg, Crucible Materials Corporation, DOE Office of Industrial Processes, General Electric Company, Martin Marietta Energy Systems, and Pratt & Whitney Aircraft.

The current project activities are focused on the transfer of the process control technology to a commercial atomizer at Crucible Research Center near Pittsburgh. This work involves software and hardware conversion to move the control system from a Macintosh computer environment to a PC computer running Labview for Windows. This change of software and operating platforms has greatly simplified the hardware requirements and relinquished software maintenance to a third party vendor, thus making the system more user-friendly to encourage wide-spread use. The resulting control system is easily portable to other computer systems, other atomizers, and other industrial processes.

Technical Objectives:

• Develop diagnostic tools for measuring process conditions of controlled atmosphere, gas atomizers. This includes off-line analysis tools (e.g. high-speed cinematography, holography) and real-time sensors suitable for process control.

• Develop mathematical modeling techniques to provide predictive calculations of process conditions and powder product characteristics of controlled atmosphere, gas atomizers. This includes Computational Fluid Dynamics (CFD) of supersonic jets, process simulators, statistical analysis of process performance, and calculations of composition and phase stability within the resulting powder product.

• Develop expert system driven process control strategies with generic applicability to a wide range of metal processing equipment and computer platforms.

• Provide industry with the methodology necessary to incorporate technology developed in this project into the production environment.

Anticipated Outcome:

• Robust process sensors for monitoring and control of gas atomizers.

• New mathematical modeling tools to aid in equipment design and improve process efficiencies.

• Expert system driven process controllers with hardware and software supplied and supported by third party companies with established national distribution network.

Accomplishments for FY 1995:

• Installed and operated new process controller on SiGMA system suitable for transfer of expert system and control software to an industrial gas atomizer.

• Provided industry with list of the sensors, data acquisition and control hardware, and software necessary to implement the NIST developed technology.

• Applied empirical models and thermodynamic data to develop methods for predicting nitrogen solubility and phase stability in atomized stainless steel alloys.

Impacts and Technical Highlights:

• CFD code developed by NIST under this project has been used by industry to redesign gas jet geometry and operating parameters to substantially improve efficiency of powder production process. The estimated cost savings are in the millions of dollars.

• Technology Transfer workshops held for industry representatives at NIST disseminated key information concerning NIST-developed sensors, analyses of the atomization process, particle-size measurement systems, and methods for automated process control.

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Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister