Relative Gas Supply Cost Notes: [a] Based on a minimum usage of 2830 cubic meters (100,000 cubic feet) per month. [b] All gases compared to nitrogen whose relative cost is unity. [c] Based on liquid supply.Heat treaters use a variety of gases with vacuum furnaces during the processing cycle in partial pressure operation, for backfilling to atmospheric pressure at the end of the processing cycle, and for cooling/quenching. In this article, VAC AERO describes the most common of these gases — (in order of frequency of use) nitrogen, argon, hydrogen and helium — as well as other common gases such as various hydrocarbons and ammonia (for vacuum carburizing/carbonitriding) and specialty gases such as neon (for certain electronics applications), and analyzes their uses and value in various vacuum heat treating processes. In addition, their relative cost per 100,000 cubic feet, the liquid properties and physical properties of common backfill gases, and the conversion between common pressure and vacuum units are explored.
