How to Improve the Assembly Quality of the Roller Box of the Wire Rod Mill?

1. The roller box of the wire rod mill

The roller box of the wire rod mill is an important part of the finishing rolling mill and the final forming equipment of the wire rod. It is mainly composed of several parts: two roller shafts, two eccentric sleeves, a box body supporting the eccentric sleeves, a roller box panel, and a roller gap adjusting device. The assembly accuracy of the roll box directly determines the product quality of the rolled parts, especially the axial gap control of the roll shaft, the comprehensive gap adjustment of the adjustment mechanism, and the radial gap control of the eccentric sleeve and the panel are particularly important.　

       2. Theoretical rolling state and fault types of the roll box

In the assembly process of the roll box, the horizontal alignment of the upper and lower roll ring grooves is ensured by adjusting the roll shaft height. The difference in height between the two roller rings does not exceed 0.02 mm. The ideal rolling state is: (1) The seasoning device pulls the eccentric sleeve to rotate to a certain position. After the desired roll gap is obtained, the centerline of the two roll shafts is constant (that is, the position of the roll shaft centerline does not change in the radial direction). (2) The position of the roll ring rolling center line is constant (that is, the rolling center axis is constant). The actual situation is that during the rolling process, with the failure of the components and the occurrence of wear and tear, the position of the groove can be changed in both the axial and radial directions, thereby changing the adjusted roll gap size, resulting in super poor product size.

       3. Cause analysis and treatment of failure

           (1)Failure of cushion washers at both ends of the bearing

Axial positioning is achieved by a pair of 1622560LB angular contact high-precision ball bearings. The bearing is installed in a face-to-face manner, and there is a buffer damping washer filled with glue at the upper and lower ends. The failure of the buffer washer is the main reason for the axial vibration.

Failure mode: the two ends of the buffer washer are worn; the rubber in the middle of the buffer washer is extruded or completely cracked.

Cause analysis: The assembly size is not suitable.

Before assembly, there is a gap of 1mm between the contact end surface of the gland and the bearing seat when the gland is not compressed (use a depth micrometer to check). When the gap value is too large, the end cover squeezes the buffer washer excessively under the action of the bolt tightening force. For a long time, the rubber will be squeezed out, and the cushion pad will crack from the middle. When the gap value is too small (or negative), during the steel rolling process, the roller shaft produces a slight amount of axial movement in the bearing seat, on the one hand, it is easy to cause the end surface of the cushion to wear, on the other hand, the bearing and the cushion are high The frequency axial force is easier to damage, and the life is greatly reduced, resulting in a greater amount of axial movement.

Solution: (1) When assembling the roller box, strictly guarantee the size of the gap, measure with a depth micrometer to ensure that the gap between the gland and the bearing seat is 1mm. (2) Use a dial indicator to regularly detect the axial movement. When the axial crosstalk exceeds 0.061mm, the roller box should be repaired offline. (3) The screws fixing the gland are tightened with a torque wrench with a tightening torque of 55Nm to ensure an even pressing force.