Effect of inert gas on ignition ability of metal friction

Abstract

For typical equipment used in the industries, such as conveyors, grinding and polishing machines, the potential hazard of friction sparks and hot surfaces as ignition sources should be considered. In this study, three representative metallic materials are selected to study the incendivity of the friction spark and hot surface in an inert gas environment. When the metal has a lower thermal conductivity, the heat energy is more likely to accumulate at the contact surface instead of being conducted. CO2 exhibits a better inhibitory effect on the spark formation and the temperature of sparks and hot surface than N2. When additional N2 content reaches 40%, the maximum temperatures of cast iron, 304 stainless steel, and 316 stainless steel decreased by 43.7%, 33.2%, and 35.6%. For 40% CO2, the maximum temperatures of the three metal friction surfaces are reduced by 48.1%, 47.7%, and 47.5%. The ignition test results are quantitatively analyzed, and the probability distributions of ignition and spark and friction surface temperatures are obtained. Compared with N2, the ignition probability of cast iron friction can be reduced by up to 57.8% with CO2. SEM, XPS and EDS analyses are performed for frictional products to examine the suppression effect of inert gas. The oxidation degree and the atomic percentage of oxygen in the friction products decrease with the increase of inert gas content.