Methods for Prevention of Ignition during Machining of Magnesium Alloys

Abstract

Magnesium alloys have been increasingly used in automotive and aerospace components and in portable microelectronic devices due to their “ultralightness” and high specific strength. Machining is an important method used to process magnesium alloys. The advantages of machining over other processing methods such as die casting include reduction in power consumption and excellent surface finish. However, the ignition of chips presents a dangerous problem during machining. This problem has attracted considerable research interests. Though coolants can be used effectively to prevent ignition, the pollution of environment and reclamation of chips can not be resolved easily. Therefore, one better approach is to control the machining parameters for minimizing ignition hazard of magnesium alloy chips during dry machining. A systematic study was conducted for a few different magnesium alloys (including AM50A and AZ91D) to understand effect of cutting parameters (cutting speed, feedrate and depth of cut) on ignition of chips during face milling. It is interesting to find that for any fixed cut depth ignition in the forms of sparks, flares or ring of fire occurs only in the moderate cutting speeds and feedrates and can thus be easily prevented by adopting either higher or lower cutting speeds or feedrates. Chips produced in different machining conditions were collected and their morphology was analyzed to understand mechanisms of ignition.