Abrasive wear behavior of new wear resistant steels applied for the middle plate of scraper conveyor

The middle plates of scraper conveyors used in coal mines suffer heavy abrasive wear, which decreases the transportation efficiency and increases the maintenance costs, as well as affect the safe production of coal mines. The microstructures, phase structures and abrasive wear properties of Ti20 and Ti60 low alloy wear resistant steels with different Ti content, which are newly developed for the scraper conveyor plates, are studied. The abrasive wear tests were conducted by a rubber wheel dry sand abrasive wear tester respectively using quartz sand as well as a mixed abrasive of coal and sand. Martensitic wear-resistant steel Hardox 450, commonly used in the middle plates of scraper conveyors, was used as a comparing steel. The Ti20 and Ti60 steels, whose Ti content is 0. 2% and 0. 6% respectively, were rolled into a plate after casting. The rolled plates were quenched at 900 ℃ then tempered at 200 ℃. The results show that the microstructure of both Ti20 and Ti60 steels is lath martensite. With the increase of Ti content, the original austenite grain size of the wear-resistant steels decreases, and the length of martensitic lath also decreases. A little of irregular shape TiC particles with a size of 1-5 μm were in-situ precipitated at the original austenitic grain boundary. The TiC particles play the roles of pinning grain boundary and refining grains. In the wear tests respectively using quartz sand and a mixed abrasive of coal and quartz sand, the hardness of coal particles is much lower than that of quartz sand, and the coal particles are more round and blunt, so that the micro-cutting and micro-plowing grooves abraded by the quartz sand present much wider and deeper than by the mixed abrasive. Whether in the quartz sand or in the mixed abrasive coal wear tests, the wear weight loss of the new wear resistant steels decreases with the Ti content. Their wear resistance can reach up 1.3 times, comparing with Hardox 450. The wear mechanisms of wear-resistant steel are mainly micro-cutting and micro-plowing. As the Ti content increases, the furrow and the cutting grooves become shallower. The worn surface looks smoother and the furrow is obstructed at the Ti element concentration zones. The TiC particles play a role of local strengthening in their surrounding area, that is, they enhance the hardness and impede the micro-cutting of the abrasives, so the wear resistance of the new wear resistant steels is improved. © 2020, Editorial Office of Journal of China Coal Society. All right reserved.