Efeitos da adição de nióbio no desempenho de ferros fundidos brancos de alto teor de cromo utilizados no bombeamento de polpa na mineração

Abstract

During the pirite and arsenicpirite ore processing, a mixture containing mainly silicon oxide, other oxides and water is guided through different process as crushing, grinding and slurry pumps in order to reduce and separate it. These operations lead to large maintenance costs due to abrasive and erosive wear. To reduce wear in this field, the high chromium white cast irons are widely used in the crushing, grinding and slurry pump parts. High Chromium white cast irons have being used in slurry pumps components. This work presents a set of different analysis, which were carried out to find, first of all, the underlying wear mechanisms and so an appropriate wear laboratory test. High Chromium white cast irons containing 15 wt. percent of Chromium, 2 wt. percent of Molybdenum and a range from 0,0 to 1,5 wt. percent of Niobium, where different microstructures were produced, as an attempt to reduce the erosive wear. The erosive wear rate was measured using SiO2 as abrasive and compared with the wear rate of commonly used white cast iron for pulp pumps. Sand with an average grain diameter of 150 μm was selected as abrasive. In order to simulate the wear behavior of pump parts a erosive test were designed. A suspension of sand (10 % weight) was used and the impingement velocity was fixed at about 14 m/s and variable impingent angle. The wear mechanisms were analyzed. A reduction on the wear rate was observed on the white cast irons with a niobium percentage of 0,5 wt. percent.