The usage requirements of high-speed steel rolling mill rolls in bar rolling line are basically the same as those of conventional material rolls, but due to their relatively higher hardness, special emphasis is placed on cooling conditions here.
The ideal cooling system should have a ring-shaped distribution of a series of nozzles that can ensure continuous and sufficient water flow towards the groove. Among these nozzles, the main nozzle should be located near the exit guide, and the water sprayed from this nozzle should account for 30% of the total water volume on the entire groove. The spraying angle should be between 20-30°, and its function is to ensure that the cooling water is rapidly sprayed onto the part of the groove that has just separated from the rolled piece. This is particularly important. The water pressure should be maintained at above 0.5MPa, and the water volume per slot for a single roll should not be less than 300L/min, ensuring that 70-80% of the water volume is on the exit side. The cooling water must be completely flushed into the groove. Since the cooling conditions of the lower roll are worse than those of the upper roll, the water volume of the lower roll should be slightly higher than that of the upper roll. The cooling water should be precipitated and the content of solid particles should be reduced as much as possible.
Although there are significant differences in the water cooling device, cooling method, water volume, water pressure, and nozzle angle of the roll for each mill, reducing the surface temperature of the roll, maintaining a uniform distribution of temperature, and ensuring the cooling effect of the roll surface are essential for improving the service life of the roll and improving the surface quality of the rolled material. Under similar cooling methods and water pressure, increasing the cooling water volume of the roll has a significant effect on reducing the roll temperature and reducing roll surface heat cracks.
When a bar rolling mill using high-speed steel rolls encounters steel sticking or stacking, the water should be immediately stopped, the upper roll should be lifted quickly to remove the rolled material from the roll surface, and the rolled material piled up on the lower roll should be removed immediately, allowing the heated groove to slowly cool in the air. When production resumes after incident handling, the slot must be changed, and it should be done at least 2-3 slots away. It is absolutely not allowed to allow cooling water to be flushed or flow onto the heated groove. If it is inevitable and the slot cannot be changed, the roll must be replaced. After the roll cools naturally, it can be reused on the machine. Otherwise, if the cooling water is directly poured onto the overheated groove, cracks will inevitably appear on the groove.