Abstract:
Mine hoist is an important throat equipment for coal transportation from the bottom of the shaft to the ground in coal mining. Hoisting wire rope is an important part of the hoist. For the winding hoist, there must be friction and wear when the wire rope is wound on the drum, which affects the service life of the rope. In addition, the drum room is generally in an open state, and its internal temperature is the same as the ambient temperature. However, the low temperature in winter in the north of China forces the wire rope to serve in the cold and freezing environment, and the lubrication state, icing and mechanical properties of the wire at low temperature will affect the improvement of the friction and wear properties of the rope, thus threatening the safety of mine production. Therefore, based on the self-made friction and wear test device of wire rope in low temperature environment, the sliding friction and wear characteristics of mine winding-hoisting wire rope under low and freezing environment were explored, which provided important basic data and theoretical basis for the design of mine hoisting system in low temperature environment. Firstly, the friction and wear characteristics of wire rope (6×19+FC) under dry friction and oil-water lubrication at low temperature were investigated. The results showed that the friction coefficient increased non-linearly with the decrease of ambient temperature under the same speed and load test conditions. For dry friction, the friction coefficient increased slightly with the decrease of ambient temperature, and reached the maximum value of at −25 ℃, approximately 0.85. However, under oil-water lubrication, the friction coefficient of wire rope increased first and then decreased at different ambient temperatures, and reached the maximum value of at -15 ℃, approximately 0.35. In addition, humidity decreased as the temperature decreased. In low temperature and humidity environment, the oxidation reaction between friction pairs of the upper and lower layer rope without lubricating oil protection was greatly weakened, which reduced the generation of metal oxides that played an isolation role. This intensified the adhesion between the friction pairs of wire rope, leading to higher friction coefficient in dry friction than that in oil-water lubrication. Then, the influence of low temperature environment on the wear of wire rope was analyzed quantitatively and qualitatively by statistical analysis of the relationship between wear depth, wear area and the ambient temperature of the wire rope. It was found that the wear depth and wear area of the wire rope were consistent with the change of ambient temperature under dry friction, with the minimum values of 278 μm and 6.23 mm
2 at 0 ℃, respectively. During lubrication, the wear area and wear depth decreased to about 1/4 and 1/7 of that of dry friction, respectively, and both reached the maximum at −15 ℃, approximately 2.98 mm
2 and 58 μm. In addition, the analysis of the element content on the worn surface showed that the oxygen atom atomic fraction on the worn surface of the wire rope was the highest, approximately 10.3%, when the ambient temperature was −10 ℃ during dry friction. Under oil-water lubrication, the oxygen atomic fraction was approximately 3.54% at the ambient temperature of −15 ℃. Finally, the wear mechanism of wire rope was analyzed. With the decrease of the temperature, the wear patterns of wire rope samples changed from oxidation wear and abrasive wear at 0 ℃ to fatigue and adhesion wear at −25 ℃. As the ambient temperature decreased from 0 ℃ to −25 ℃, the adhesion wear of the wire rope increased first and then weakens under oil-water lubrication. At the same time, the oxidation wear of wire rope can be greatly reduced in low temperature environment.