Cooling issues in the use of high-speed steel rolls

The thermal expansion of high-speed steel rolls is large, and the poor temperature distribution of the rolls can easily cause uneven thermal expansion and abnormal shedding of the oxide film, which affects the thermal crown and roll gap accuracy of the rolls. The key factor affecting the oxide film and thermal crown of high-speed steel rolls is the roll surface temperature. Therefore, the ideal roll cooling method and shortening the time when the roll surface is in a high-temperature state are important means to control the oxide film thickness of the roll surface, control the thermal crown, and reduce thermal cracks.

The instantaneous contact temperature of the roll during the hot rolling process is 600 ~ 750℃. After the roll surface comes out of the contact arc, the temperature must be reduced from 700℃ to below 300℃ as soon as possible to prevent further oxidation. After the roll passes through the instantaneous high-temperature contact area, it must work quickly In a 100% water-cooled environment, it is conducive to the formation of an oxide film with the best protective performance. By optimizing the roll cooling water distribution, measures such as increasing the cooling water volume on the exit side, increasing the cooling water volume in the middle of the roll, and reducing the height of the cooling water pipe can significantly reduce the roll surface temperature.

A flat nozzle is used instead of a conical nozzle, and 3/4 of the cooling water is used for cooling the tappet side of the roll to control the roll surface temperature below 50°C. The cooling system is an annular series of nozzles that ensure a continuous and sufficient flow of water to the rolling groove.

The main nozzle should be near the exit guide. The amount of water sprayed from the nozzle is 30% of the total water volume in the entire rolling groove. The spray angle is 20° ~ 30°. The function of this nozzle is to ensure that the cooling water is quickly sprayed into the rolling groove. On the part that has just separated from the rolled piece.

Control the water pressure at (4 ~ 6) × 105 fifth power 5Pa, and the water volume in each tank is at least 500L/min. The water flow cannot be scattered, and the cooling water needs to be precipitated to reduce the content of solid particles as much as possible to avoid damage to the rolls.

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