The influence of titanium and iron oxides on the coloring and friability of the blue fired aluminum oxide as an abrasive material

(Influência da titânia e óxido de ferro na coloração e friabilidade do óxido de alumínio blue fired como material abrasivo)

Abstract

The quality of abrasive grains is crucial to increase the lifespan of roughing, polishing and cutting tools. The purpose of the work herein was to evaluate the variables of the blue fired aluminum oxide heat treatment process. This heat treatment process improves the physical properties of the brown fused aluminum oxide and results in a blue coloring, which uniquely identifies it within the abrasives industry. The work herein includes information beginning with the electro-fusion process of bauxite (the manufacturing of the brown fused aluminum oxide) to the Blue Fired process. It also compares the fracture resistance index between these materials. This index is the inverse of the friability. Besides the content of titanium and iron oxides, process variables such as time, temperature and atmospheric conditions are important to monitor in order to reach standard requirements. Experimental evidence measuring these parameters is presented in the article herein. The blue coloring of this aluminum oxide is explained by the optical phenomena of electron transition, and not by the formation of aluminum titanate, as some technical literature has stated. Furthermore, it was proved that the coloring of blue fired material should not be used exclusively as an indicator of the optimal abrasive characteristics of this class of aluminum oxide.

Keywords:
abrasives; brown fused alumina; blue fired fused aluminum oxide; titanium oxide; iron oxide; fracture resistance index