Phase-Controlled Nitriding and Nitrocarburizing Applied To Reduce Flaking,
Jack A. Kalucki, Nitrex Metal Inc., Montreal, Québec, Canada
Brittleness and Improve Die Life
Track: EXTRUSION EQUIPMENT - Die Heating and Preparation
ABSTRACT—Nitrex Metal Inc. has developed and extensively relied on the concept of controlled gas nitriding to improve die life and productivity. This concept, albeit sophisticated, does not control nitrogen concentration during heating or cooling, causing the case to change structure and thus its properties. Since last year, a new control concept has been introduced and integrated by Nitrex into its control systems: PHASE-CONTROLLED NITREG®/NITREG®-C. It is a completely new approach to gaseous nitriding/nitrocarburizing. This proprietary technology allows us to control the nitrogen, or nitrogen and carbon content during the entire nitriding or nitrocarburizing cycle, including heating and cooling. With an improved distribution of nitrogen/carbon throughout the case, it is now possible to achieve optimum properties for aluminum extrusion dies. The technology relies on accurate H2 smart gas analyzers, closed-loop process control and proprietary control software. The resulting process is not a sequence of heating, nitriding, and cooling, but a more elaborate set-up that follows a specific nitrogen concentration on Lehrer’s diagram, and a nitriding potential that readjusts according to the temperature and the stage of the process. From a practical point of view, the process produces a perfect nitrided case with compressive stress distribution aimed to minimize die flaking and brittleness.
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