Fault causes and solutions of roller press - roller surface damage

Since the introduction of the roller press in the mid-1980s, it has been widely used in various grinding operations. The roller press consists of two rollers of the same speed and relative rotation. The material is removed from the upper feeding port of the roller and enters the gap between the rollers. Under the action of high-pressure grinding force, the material is squeezed, and the pressed material becomes a dense but cracked flat feed, significantly improving its grindability. The wear of the roller surface of the roller press and the damage of the bearing are common problems of the roller press, so regular maintenance greatly contributes to the production of the roller press.

The roller surface is made of several layers of composite metal. And the base of the roller is made of alloy forged steel. The hardened layer of alloy with a Rockwell hardness smaller than 50 is deposited on the transition layer, and the abrasion resistance pattern is further welded on the hardened layer. In order to make the service life the roller surface between over 8000 hours or even 10000 hours, the hardness of abrasion resistance pattern of the most surface can reach 60 to 65 HRC to improve the wear resistance.

Causes of roller surface damage

1) In the production process of the roller press, the damage of the roller surface is a common phenomenon. The main performance is that the roller surface is cracked and spreads into deeper fissures, which causes the peeling of the hard anti-wear layer of the roller surface. As can be seen from the working conditions of the roller press, this type of wear of the roller surface is typical of high stress abrasive wear.

During the abrasive wear process, the material particles will elastically and plastically deform the roller surface under the action of pressure, so that cyclic compressive stress and tensile stress will be formed at different depths of the subsurface of the roller surface, when the cyclic stress exceeds the fatigue strength of the roller material, cracks will be caused in the surface layer.

Under cyclic loading, the plastic deformation of the subsurface continues to develop, and cracks will also occur at a certain depth from the surface and gradually expand. When the crack extends, the material above the crack is fractured and peeled off. This phenomenon is fatigue wear. The wear mechanism of the roller is the result of the combination of the high stress abrasive wear of the roller surface and the fatigue wear of the subsurface of the roller surface.

2) As a result of the operation, metal materials or other hard materials may be mixed in the material fed to the roller press. Under the strong grinding force between the two rollers, the metal debris may directly damage the roll surface, causing the surface of the roll to be pitted or the hard wear layer to collapse. Since the hardened layer is very hard, the resilience is relatively poor, the impact between the hardened layer and hard materials may result in microcrack extension and collapse of the hardened layer, and eventually cause roll surface defects. If the situation is serious, it will directly affect the service life of the roller surface, and the increase of defects will directly influence the quality of the materials produced by the roller press and the expected rolling effect will not achieve.


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