A Research On Steel Rail Materials Processed By High-speed Grinding With Cryogenic Gas-liquid Two-phase Supplying Technique

With the rapid development of modern railway technology,the traditional operating types of steel rail shaping are facing new challenges.Thus,it will become increasingly important to improve the efficiency and quality of steel rail shaping operations.The milling train's repairing quality and efficiency closely link the grinding performance of grinding wheel.CBN grinding wheel's overall performances are far superior to the corundum grinding wheel which is currently being used,and using it in the milling train can greatly increase the car's operating efficiency.Besides,cooling technology is a key issue in high-speed and high-efficiency grinding.In order to appropriately reduce the usage amount of grinding fluid under the premise of guaranteeing the quality and efficiency of grinding,from the perspective of environmental protection,cryogenic gas-liquid two-phase supplying technique of high-speed and high-efficiency grinding has been studied in this thesis.The main research contents are as follows:(1)Propose the cryogenic gas-liquid two-phase supplying method for high-speed and high-efficiency grinding,and design a set of cryogenic gas-liquid two-phase supplying device.This device uses cryogenic compressed gas to carry a small amount of liquid which is injected into the processing area to achieve enhanced heat exchanging with the way of sprayed impact jet flow.(2)Use Fluent,this software to study the fluid in the grinding wedge-shaped area via analogue simulation,and work out the distribution rule of airflow field and pressure field in the grinding wedge-shaped area.The airflow layer is present on the surface of the high-speed rotating grinding wheel.With the increase of the distance of the grinding wheel's outer edge,the airflow velocity will decrease.In addition,there is a large velocity gradient.The existence of the workpiece makes the speed of the air present certain regularity in the wedge-shaped area which is between the grinding wheel and the workpiece.In the grinding introduced area,due to the effect of the air viscosity,the airflow velocity gradually increases.When it reaches the minimum clearance,the speed of the generated airflow field reaches to the maximum,which is close to the grinding wheel's linear speed.In the grinding introduced wedge-shaped area,backflow phenomenon appears.(3)Study the cryogenic gas-liquid jet velocity distribution field.And use the principle of equal pressure to analyze the effect of gas-liquid two-phase supply.(4)Apply the cryogenic gas-liquid two-phase supplying technique to the test of using CBN grinding wheel to grind steel rail materials.Make a comparison between cryogenic cooling gas and cryogenic gas-liquid two-phase supply,these two grinding cooling methods.And investigate the impact of grinding parameters on the grinding force,grinding temperature and surface quality with these two cooling methods.The experimental results show that,compared with cryogenic cooling gas cooling method,the grinding force and grinding temperature of cryogenic gas-liquid two-phase cooling method are lower,and the grinding surface quality of it is better.As a result,CBN grinding wheel greatly improves the efficiency of the steel rail grinding.