A high-speed rolling mill generally refers to a rolling mill with a maximum rolling speed higher than 40m/s. Therefore, when the maximum rolling speed of a wire rod rolling mill is faster than 40m/s, it is called a high sheath rolling mill. The characteristics of the high-speed wire rod mill are: high speed, single wire, no torsion, slight tension, combined structure, calcium carbide spoke ring, and automation. Its products are of large discs, high precision, and good quality. Improving the rolling speed of the wire rod mill is the trend and the key to the development of the wire rod mill. Increasing the rolling speed of the rolling mill can increase the output of the rolling mill, increase the coil weight and reduce the cost.
Focusing on the problems caused by the increase in speed, various types of high-speed wire rod mills have been researched from the perspective of realizing torsion-free rolling and reducing mill vibration. After the disk weight increases, the inner layer wire stays at a high temperature, forming coarse grains, which makes the performance of the inner and outer rings very different. Controlled cooling is required to solve this problem.
High speed, no torsion, and controlled cooling are the main technological features of modern high-speed wire rod mills:
High-speed rolling: the rolling speed of an ordinary continuous wire rod rolling mill is generally below 35m/s, and the rolling speed of a double-double rolling mill is about 16m/s. And the rolling speed of the high-speed wire rod mills currently in use is mostly above 75m/s, and the higher rolling speed has reached 120m/s, even 140m/s;
Twist-free rolling: the finishing rolling unit of a general high-speed wire rod mill consists of 8 to 10 stands, single-wire rolling, and the rolling is cantilever type, adjacent to the stands;
Cooling: Due to the high rolling speed and heavy disk of the high-speed wire rod mill, it is not acceptable to adopt the method of directly collecting coils. On the high-speed wire rod rolling mill, the rolled piece comes out of the finishing mill and directly enters the water cooler for rapid cooling, and then through the laying machine, the wire rod is scattered in a controlled manner on the conveyor for coil cooling, generally using air cooling, and finally, Air cooling is natural cooling. Controlled cooling is not only to cool down the temperature quickly, prevent the formation of secondary oxide scale and make the structure uniform but more importantly, to control the structure and performance of the wire. Therefore, the processing system for controlling each section of cooling is determined by the microstructure and performance requirements of the steel type of the rolled wire rod;
Low-temperature rolling and controlled rolling: Due to the high rolling speed, the temperature not only does not decrease but rises during the rolling process, so the rolling start temperature can be reduced to achieve low-temperature rolling. The temperature of each section is controlled by setting water coolers at different positions to carry out controlled rolling.
Under such equipment and process conditions, the high-speed wire rod mill has high output, heavy coil, high product precision, good surface quality, and excellent microstructure.