The train wheel is one of the most important components of the rail vehicle running the department, and its product quality is directly related to the running safety of the rail vehicle. On the one hand, with the vigorous development of China’s rail transit, the domestic high-speed EMU and urban rail vehicles have an increasing demand for new wheels; on the other hand, wheels are consumable parts that need to be replaced regularly, so the maintenance market is very large. At the same time, with the continuous increase of vehicle speed, the technical requirements for the specialized production of high-speed wheels are also getting higher and higher. At present, the manufacturing technologies of domestic and foreign wheels mainly include forged wheels and cast wheels. Forged wheels are increasing day by day and are the most widely used wheels for rail vehicles.
An integral track wheel refers to an integral wheel manufactured by forging and rolling in the forming process, also known as rolled steel wheel.
The main processes used in the manufacture of train wheel forgings are steelmaking, hot forming, heat treatment, machining, and testing.
(1) The steelmaking process includes steelmaking, out-of-furnace refining, and pouring.
(2) The hot forming process includes performing, forming, rolling and punching, and bending. The round billet is heated in a ring furnace; the function of the performing process is to subject the circular batch to the steps of upsetting, performing, and forming; forming means that the basic shape of the wheel is completed, in which the forming of the hub and the hole of the hub is completed, the web and the rim Part of the distribution are completed to form the basic shape; the function of rolling is to roll and expand the wheel spokes, roll the rim to the maximum height, and complete the forming of the wheel tread and rim. At present, there are two main types of wheel rolling mills for rolling: one is a horizontal rolling mill and the other is a vertical rolling mill; there are two types of punching and bending methods: press and rotary forging. The web bending process is used to flatten the rim and bend the web to the required position. Most manufacturers also complete the hub hole punching in this step. The temperature of the thermally deformed wheel blank is 850-950oC. Generally, slow cooling and isothermal processes are used to control the cooling rate, and the temperature is cooled to room temperature, waiting for the next step.
(3) The mainstream process of wheel heat treatment is rim quenching + tempering. There are also some manufacturers who have adopted the rim immersion quenching + tempering process, as well as normalizing and other processes. The quenching methods also include continuous quenching, intermittent quenching, vertical quenching, and horizontal quenching.
(4) Machining refers to the use of special or general vertical lathes to semi-finish and finish the wheels, so that the shape, surface quality, and geometric tolerances of the wheels meet the requirements of the drawings. Wheel processing is generally divided into single equipment processing and line equipment processing. With the application of computer technology, more and more line equipment is processed, and the efficiency is getting higher and higher. The quality is also further guaranteed. Its production process is compact and the level of automation is high, which represents the highest level of wheel production at home and abroad.
(5) The final inspection of the wheel production line includes a Brinell hardness test of the rim surface, an ultrasonic inspection of the wheel, magnetic particle inspection of the wheel, static balance test of the wheel, surface quality inspection, external dimension inspection, etc. The inspection items involve mechanical properties, internal and External integrity, external dimensions, etc.
At present, there is still a certain gap between my country’s high-speed EMU wheel manufacturing and the industry’s leading level, especially in the smelting and heat treatment process research methods and the work content of new material special steel. In future development, attention should be paid to the research and development of high-speed wheel materials, the prediction and test methods of new wheels, the research and development of new wheel quenching methods, the research of wheel detection methods, and the comprehensive simulation performance detection of wheelsets.
The strength of the wheel spoke is directly related to driving safety, and the shape of the spoke has a great influence on the structural strength and rigidity of the wheel. At present, the shapes of the webs used at home and abroad are S-shaped auxiliary panels, wave-shaped webs, straight webs, and basin-shaped webs. The straight spokes are smaller in mass than other types of spokes. The disadvantage is that the radial stiffness is too large and the axial stiffness is small. However, with the large-scale manufacturing of high-speed EMUs, due to structural limitations, the power wheels of EMUs are mostly used, Therefore, the shape of the wheel spokes is also mostly in the form of straight spokes, with high-precision spoke holes to install the brake disks, such as the wheels for China CRHT, CRH2, CRH3 EMU power wheelsets, This puts forward new requirements for the force and processing of high-speed wheels.
In order to ensure machining accuracy, eliminate accumulated errors, and simplify the process flow, the concept of wheel machining center is proposed internationally, which includes wheel forming processing (including webs, treads, front and back sides of hubs), web hole processing, oil injection hole processing, The machining of hub holes is centralized on one piece of equipment to ensure efficient finishing of all parts of the wheel. At present, this technology has been applied in some factories.
