Introduction
Rolling mills are machines designed to shape metal into various forms using a series of rollers. They are used in the production of various metals, including steel, aluminum and other metals. The rollers, or cylinders, can be set at different distances apart to create various shapes. When the rollers are too close together, they create a “false-roll” that results in the metal being distorted and deformed, causing unacceptable shapes and contours.
When this occurs, the mill must be stopped and the rollers adjusted before it can continue. The process is known as “tapping” and can often be a time consuming process, as the rollers must be set back to the correct position, especially when the false-roll has created uneven surfaces or voids.
Causes
One of the most common causes of a false-roll is improper alignment of the rollers. When the rollers are not properly aligned, the metal will be bunched up in one area and then stretched or distorted in another. This can cause the rollers to become unevenly spaced and cause the metal to become misshapen. Additionally, if one of the rollers is not properly set, it may move when subjected to the weight of the metal, resulting in further misalignment and false-rolls.
Another common cause of false-rolls is the use of inadequate lubrication. When the rollers are under high pressure and heat, they can become distorted and deformed if the necessary amount of lubrication is not applied. As the pressure and heat increases, the lubrication becomes less effective, resulting in false-rolls.
Finally, false-rolls can also be caused by uneven temperatures across the rollers. If the rollers are not evenly heated or cooled, the metal may become distorted as it is passed between them. This can cause the rollers to move in opposite directions, creating a false-roll.
Solutions
The first step in preventing false-rolls is to ensure that the rollers are properly aligned. This can be done by adjusting the pressure, ensuring that the rollers are the same distance apart, and ensuring that the rollers are level. Additionally, the rollers should be regularly checked for displacement, as they can become misaligned over time.
It is also important to make sure that the rollers are properly lubricated. This should be done on a regular basis, and the lubricant should be applied evenly to both rollers. Additionally, a good quality lubricant should be used, as lower quality lubricants may not be able to withstand the heat and pressure of the rolling process.
Finally, the temperature of the rollers should be maintained at a consistent level. This can be done by using fans or air circulating systems to control the temperature of the rollers. If the temperatures are not kept consistent, it can lead to false-rolls as the metal passes between rollers with different temperatures.
Conclusion
False-rolls can be a frustrating problem in metal rolling mills. However, by ensuring that the rollers are properly aligned, lubricated, and temperature controlled, the incidence of false-rolls can be greatly reduced. Additionally, it is important to check the rollers on a regular basis to ensure that they remain properly aligned and that no displacement has occurred. By following these steps, false-rolls can be minimized.
