Classification Of Mg Die-casting Scraps And Safety Management During Their Collection, Storage And Transportation

As the lightest metal structural material of commercialization, the magnesium alloy find more and more applications. At present, more than 90% magnesium alloy parts are produced with die casting. During Mg die casting, only 30~60% material remains on the parts, while the rest becomes different type of processing scraps. The high chemical reactivity of the Mg alloys with the environment makes the scraps prompt to ignition and explosion. It is, therefore, of paramount important to set up a national safety standard for the handling of the scraps post their generation in Mg manufacturing industry.After an introduction to the current situations and the relevant theories of standard composition, this paper first studied the critical conditions and spontaneous combustion range of the heated power in the particle state and forced ignition and, then, analyzed the influence of different factors, such as, dispelling heat, volume size, medium temperature, particle size, alloying element, moisture, oxygen content of medium etc. on the ignition phenomenon in order to lay a theoretical foundation for proposing safety measurements. Then, the paper is devoted to magnesium die casting scrap classification with consideration of GB/T 20926-2007 for magnesium and magnesium alloy scraps and the thermodynamics and dynamics of scrap ignition.This paper studied the explosion conditions of magnesium powder. The magnesium alloy can react with water and moisture to produce hydrogen at the same time. The released hydrogen gas will mix with air, which, in turn, will explode when meets flame. This paper put forward precautions to prevent the reaction of scraps with water to eliminate the generation of hydrogen.According as classified ignition causes, this paper sets up safety management criteria for magnesium scraps during their collection, storage and transportation.As a conclusion of this study, a draft standard named'Classification of Mg Die-casting Scraps and Safety Management during Their Collection, Storage and Transportation'was composed in accordance with the existing relevant standards, the principles of national standard composition.