20 high carbon steel strip mill rolling process

The 20 high rolling mill is a kind of multi-roll cold rolling mill. Compared with the 4-high and 6-high cold rolling mill, it has the characteristics of a small diameter of the work roll, a large reduction in each pass, and a strong ability to control the shape of the plate. It is mainly used It is suitable for rolling precision strip steel or high-strength strip steel.

In recent years, some iron and steel enterprises have begun to use twenty-high rolling mills to produce thin carbon steel strips with a finished thickness of less than 0.2 mm. Compared with the conventional production process of carbon steel thin strips, the 20-high rolling mill can use thicker raw materials when producing thin strips, so as to save the cost of raw material procurement and supply; in addition, the 20-high rolling mill has good shape control Capability. The rolled strip with a thickness of less than 0.2 mm can have a good shape.

Characteristics and common models of twenty-high rolling mills

In order to be able to roll thinner strips, the diameter of the work rolls of the 20 high rolling mill is relatively small. The reduction of the diameter of the work rolls leads to the deterioration of the lateral stiffness of the work rolls. For this reason, the 20-high rolling mill adopts a tower Shaped roll system. That is, the upper and lower roll systems are respectively composed of one work roll, two one middle rolls, three two middle rolls, and four backing rolls superimposed in a tower shape, (see Figure 1)

 

20 high rolling mill
Figure 1
1–Intermediate roll;  2-Two intermediate rolls;  3-Working roll;  4-Backing roll

 

Such a roll system structure not only ensures the lateral stiffness of the work rolls but also ensures the stability of the roll system. This is also the most notable feature of the 20 high rolling mill compared to the four-high and six-high rolling mills.

The four outermost rollers among the middle rollers in the tower roller system are drive rollers, and the middle ones are idler rollers. The four drive rollers are centrally driven through a gearbox, so the difference in roll diameter between the four drive rollers is adjusted when the rollers are matched. There are strict requirements, and there is a safety handover between the gearbox and the k-motor, which can protect the mechanical equipment of the transmission system in the event of an accident (see Figure 2)

 

20 high rolling mill
Figure 2
1—main motor;  2—safety handle;  3—gear box; 4—drive shaft

 

The 20-roll pressing mechanism and the rolling height adjustment mechanism respectively use hydraulic cylinders and hydraulic motors to drive the racks, and drive the gears connected to the eccentric wheels to adjust the working position of the roll system: the thrust provided by the hydraulic cylinders and hydraulic motors is as long as It is enough to overcome the friction between the sliding surfaces caused by the rolling force component, so the size of the hydraulic equipment and the rolling mill can be greatly reduced (see Figure 3)

20 high rolling mill
Figure 3
1—Depression device; 2—Rolling elevation adjustment device

 

In addition to better mill rigidity, the 20 high rolling mill has a strong shape control ability. Its four middle rollers have the function of lateral movement, and one side of the roller body is provided with a taper. They are arranged in a staggered manner in the upper and lower roller systems. Use the taper to cooperate with the lateral movement of the rollers to control the shape of the edge of the strip. In addition, it can also be used Sheet shape (ASU) is controlled by adjusting the backing roll. The backing roll of the twenty-high rolling mill is composed of multiple backing bearings, each backing bearing is driven by a separate hydraulic cylinder through a rack and pinion, and can be adjusted by adjusting the reduction amount of each backing bearing during work. The shape of the roll gap, thereby controlling the shape of the strip.

 

 

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