The pre-heated annular blank is sleeved on the driven roller of the ring rolling machine, and the driving roller rotates while making radial feeding, and the two rollers jointly roll the billet, so that the blank is extended under pressure while following the rotation of the driving roller, and the inner and outer diameters are increased, and the wall thickness is reduced until it is formed. Compared with forging molding, this manufacturing method has greater economic and technical advantages, which are mainly manifested in:
Compared with the integral pressure forming of die forging, only the roll needs to apply local continuous pressure to the blank during the processing of the ring rolling machine, and the contact area between the roll and the workpiece is small, so the required deformation force is small. For example, the production of a gear ring with a diameter of about 0.4 meters only needs to provide a pressure of 600 kN, and if a die forging press is used, it needs to provide a pressure of more than 80,000 kN.
Recently, this process has been used to successfully manufacture a diameter of 10 meters, a height of 4 meters of nuclear reactor vessel reinforcing ring, if the use of die forging process to be processed in sections, can not achieve the overall molding.
The ring mill only needs to punch a small hole in the blank in advance, without reserving flash and draft angle, and the cross-sectional shape of the ring is closer to the finished product, without too much subsequent shaping and cutting. The deformation caused by rolling is radial compression and axial extension, and the metal fibers in the ring billet are continuously arranged along the circumference, which is compatible with the force and wear direction in the use of the ring, so the strength of the finished product is higher, more wear-resistant, and the internal quality is better. Compared with other forging methods, there is no impact, no vibration, low noise, the working environment and working conditions have been greatly improved, and it is easy to realize mechanization and automation.
Due to the high utilization rate of materials, less machine time and low production energy consumption of ring rolling machine, the comprehensive production cost is low. According to foreign data, compared with open forging, the production cost is reduced by nearly half. Moreover, the rolling speed is usually 1-2 m/s, the whole processing cycle is generally about 10 seconds, and the production efficiency can reach 1000 pieces/hour, which is much higher than the efficiency of other ring forging methods.
Because the cross-sectional shape of the annular billet in the production process of the ring mill is always changing, and there are many unstable factors in the positioning of the billet and the roll, it is necessary to have a comprehensive consideration when designing the process parameters, and design the appropriate rolling and expansion ratio and the amount of pressure per revolution, so as to ensure that the whole rolling process always meets the bite conditions of the billet, which is quite difficult. In addition to a pair of rolls that realize the rolling function, it is necessary to add guide rollers to shape the workpiece while making it rotate smoothly. A control roller was added to stop the processing process.
At present, the materials suitable for processing of this new process have been extended to carbon steel, alloy steel, aluminum alloy, copper alloy, titanium alloy, cobalt alloy, nickel-based alloy, etc., and have successfully manufactured workpieces with a diameter of 40-10,000 mm, a height of 10-1,000 mm, and a weight of 0.2-82,000 kg.