Study On Impact Wear Performance Of Welded Joints Of Hypereutectoid Steel Rail

The use of seamless rail significantly reduces the wheel-rail impact load and improves the wheel-rail service life.However,the welded joint is the worst part of the seamless line.The welded joint will have a low step under the repeated wheel rolling,which increases the unevenness of the welded joint.In particular,with the increase of the train speed and axle weight,the impact force of wheel-rail increases sharply,which may cause serious damage to the rail welded joint.At present,there are few researches on the impact wear performance of rail welded joints at home and abroad.In view of this,this paper simulates the impact behavior of the wheel on the rail welded joint by using the self-made impact wear tester,and studies the impact performances of rail weld,the softening part of heat affected zone and the base metal,which were welded by the two welding processes of flash welding and aluminum heat welding.By means of optical microscope,scanning electron microscope,MVK-H21 Vickers hardness tester and laser confocal microscopy,the evolutionary behavior of impact wear and wear mechanism of the welded joint material under different impact cycles were compared and analyzed.The main conclusions are as follows:1.The maximum impact force of the impact wear tester is 1000 N,the impact frequency is 0-20 Hz.In principle,the impact wear tester can work continuously without stopping when the impact force is less than 800 N.The tester has a high degree of automation.The system software is developed by Labview,and the test parameters are easily adjusted.The test data is automatically stored and remotely monitored and controlled in a networked state.2.With the increase of the number of impacts,the impact wear of the material at the rail welded joints underwent plastic deformation,pitting corrosion and fatigue spalling.After impact,the content of oxygen element in the inner side of the impact pit was significantly higher than that in the outer side.The impact wear was the result of combined action of fatigue wear and oxidative wear,and the late damage was mainly caused by fatigue spalling.3.Due to the differences in microstructure and mechanical properties of the joint caused by the welding process,the impact properties of the materials indifferent welded parts are quite different.For the same welded joint,the softened part of the heat affected zone has the worst impact resistance,the most serious plastic deformation,and the largest wear volume and wear rate.That was followed by the weld,and the base material has the best impact resistance.The hardness has a significant influence on the impact resistance of the welded joint.The smaller the hardness,the earlier the fatigue peeling,and the worse the impact resistance.4.For hypereutectoid steel rails,the uniformity of the microstructure is improved,and the mechanical properties are obviously improved since the flash-welded joints are subjected to normalizing heat treatment after welding.The overall hardness is higher than that of the aluminum heat-welded joints.Therefore,its impact resistance is better than that of aluminothermic welded joints.