Common defects of rolls and their solutions
During the use of rolls, various factors often cause defects such as wear, cracks, peeling, and breakage of rolls, which have a serious impact on our production process. So what is the solution? Let me give you a specific summary of the common defects of the roll and the introduction of the solutions:
1. Roll wear
Divided into three categories: mechanical wear is caused by the friction between the surface of the roll and the rolled piece, thermal wear is caused by the softening, melting or evaporation of the surface layer due to high temperature, and corrosion wear is caused by the chemical action, electrochemical action, and oxidation of moisture on the roll surface. Effects, etc. cause surface material loss and migration.
2. Roll cracks
Accidents such as stacking of steel, jamming of steel, and rear-end collisions occurred during rolling, resulting in a sharp rise in local temperature, resulting in thermal stress and structural stress exceeding the limit, forming hot cracks. The tongue is formed by rolling and extending, and its temperature is lower than that of the middle rolled piece, which will cause thermal stress and sudden change of rolling stress, forming impact cracks. During rolling, cracks will also be formed due to iron oxide scale rolling, guide scratches and other reasons.
3. Roll peeling
The formation and propagation of cracks is accelerated, and after reaching a certain length and depth, it will cause spalling.
4. Roll breakage
1) Roller casting defects
In the centrifugal casting of rolls, due to the centrifugal vibration, the layered segregation of composition and structure will form, and the cracks will expand rapidly, causing the rolls to break.
2) Defects in roll structure
Unqualified chemical composition and improper cooling rate will lead to defects such as composition segregation and excessive cementite, but the mechanical properties will decrease and eventually lead to fracture.
3) Processing technology
When the roll is forged, the pressure is too small or the deformation is unreasonable, so that the core of the roll is not forged through, forming transgranular cracks.
1. The roll is made of wear-resistant and heat-resistant crack-resistant material, and corresponding heat treatment and logistics chemical treatment measures are taken to homogenize the structure and increase the wear resistance of the surface. defects such as cracks.
2. When the roll is turned, the residual oxide layer and cracks should be completely removed to reduce the cracks and spalling on the roll surface.
3. Reasonably arrange the roll changing cycle, select rolls, formulate a detailed roll repair plan, control the amount of repairs within the required range, reasonably arrange the range of cooling water injection and control the cooling water volume, and ensure that the cooling temperature of the rolls is controlled within the normal range .
4. Strengthen equipment spot inspection, prevent steel rolling equipment accidents, reduce accidents such as steel jamming, stacking of steel, and rear end collisions, strictly control rolling temperature, prevent low-temperature steel from passing through the rolling mill, and avoid rolling force overload.