Sometimes there are small defects in the production of sunken rolls, such as scratches on the sunken roll. So how did this happen? What are the influencing factors?
In fact, there are many influencing factors. For example, in terms of equipment, there are generally the following reasons:
a. Regarding the mechanical structure of the sunken roll device, the groove shape on the surface of the sunken roll should be considered first from the point of view of increasing friction.
There are two reasons for this: First, zinc is a heavy metal, and its liquid zinc has poor fluidity and high viscosity. In the high-speed movement between the strip and the submerged roll, a liquid zinc film is easily formed between the strip and the submerged roll, which plays a certain lubricating role and reduces the transmission friction between the strip and the submerged roll, which is easy to cause subsidence. Roller scratches.
Therefore, the grooves must facilitate the flow of molten zinc between the strip and the submerged rolls and prevent the formation of sliding films of the molten zinc.
Secondly, when designing the grooves on the surface of the submerged roll, it is necessary to make the submerged roll and the strip in an ideal stress state from a mechanical point of view, and increase the transmission friction between the two as much as possible.
Therefore, the above two points must be considered when designing the grooves on the surface of the immersed roll.
b. The requirement of roller surface material is also one of the influencing factors. Due to the special working position of the sunken roll, the material of the roll surface of the sunken roll should meet three requirements:
- Corrosion resistance 2. Hardness requirements 3. Roughness requirements
c. From the dynamic point of view, the influence of the self-weight of the sunken roll is another important factor affecting the transmission of the sunken roll. Under normal production conditions, the sinking roll is affected by the positive strip pressure, the friction between the strip and the sinking roll, the force between the strip and the bearing housing, and its own weight.
From the synthesis and decomposition of the force, the resultant force of the above four forces can be decomposed into radial positive pressure and radial tangential force, of which the radial tangential force is the driving force of the submerged roller, and its magnitude directly affects the rotation of the submerged roller.
d. According to the structural design requirements of the submerged roller device, the submerged roller device must be designed to solve the problem of axial fixation to prevent the submerged roller from sliding axially during its rotation. Especially for some strips with poor shape, such as wedge-shaped strips and strips with uneven thickness, when they are in contact with the strips, the force between the strips and the sinking rolls is uneven, which is easy to cause the strips to run away. Deviation, causing the strip to slide axially on the sunk roll, resulting in scratches on the sunk roll.
The gap between the bearing of the sunken roller and the bearing seat should be as small as possible; if the gap is too large, it is easy to cause the radial runout of the sunken roller.