The hot strip mill is divided into a rough rolling section and a finishing rolling section. The finishing part is divided into a front section and a back section.
Since hot rolling is performed at high temperatures, the rolls are required to have wear resistance at high temperatures. Therefore, the main material of the roll is a casting material containing a large number of carbides. The rolling load and heat load of the rolls in the rough rolling section are relatively large, so the rolls should be cast materials containing a large number of carbides.
However, starting from the finish rolling, the material of each stand roll can be changed to a material with a lower carbide content.
The castings of carbide-containing rolls are generally rolled composite structures. The outer layer of the roll is made of hard material, which makes the outer layer of the roll resistant to wear and orange peel. The inner layer of the roll is made of a tough material so that the roll will not break due to torque and pressure.
In the rough rolling section, the reduction rate is large, the rolling load is large, and the temperature of the rolled material is high, so the rough rolling rolls are made of high-strength and good heat resistance materials. The finishing rolls are made of materials with good wear resistance and orange peel resistance.
In addition, rolls should be used in the post-finishing section, and the material should be accident-resistant. That is, the roll will not be damaged due to deep cracks when a rolling accident occurs in the late stage of finishing rolling.
Rolls used in steel rolling production can be manufactured by forging, casting, powder sintering, and other methods.
Hot-rolled work rolls are mainly cast rolls. In the past, the roll was not a composite structure, but a single material. Improve the performance of the roll, and the roll has developed into a composite structure roll with a high degree of freedom in the outer layer material.
The casting methods of composite rolls are mainly centrifugal casting and continuous casting. The inner layer of the centrifugal casting roll is nodular cast iron, and the inner layer of the continuous casting composite roll is cast steel.
Cold-rolled work rolls are mainly forged rolls. Cast and forged rolls are available in a variety of materials. According to the material, adopt the corresponding roll manufacturing method. After rolling, the surface properties of the rolls are changed due to wear. At this time, the deteriorated layer on the surface of the roll can be removed by grinding and other methods, and it can be used continuously.