Common Defects of Rollers and Their Remedial Measures

　　During the operation of rolling mills, various factors often lead to defects such as wear, cracks, spalling, and fractures, which can severely impact the production process. So, what solutions are available? Below is a detailed summary outlining common rolling‑mill defects and corresponding corrective measures.

　　1. Roll wear

　　They are classified into three types: mechanical wear is caused by friction between the roll surface and the workpiece; thermal wear results from high temperatures that soften, melt, or vaporize the surface layer; and corrosive wear arises from chemical, electrochemical, and oxidative reactions of surface moisture, leading to material loss and migration.

　　2. Roll Cracks

　　During rolling, incidents such as steel pile‑up, steel jamming, and rear‑end collisions can cause a rapid local temperature rise. When the resulting thermal stresses and microstructural stresses exceed their limits, thermal cracks develop. Rolling elongation may produce “tongues” of material whose temperature is lower than that of the central region, leading to thermal stresses and abrupt changes in rolling stresses, which in turn give rise to impact cracks. Additionally, during rolling, cracks can also form due to factors such as the repeated rolling of oxide scale or scratches caused by guide devices.

　　3. Roll spalling

　　The initiation and propagation of cracks accelerate, and once they reach a certain length and depth, spalling occurs.

　　4. Roll Fracture

　　1) Casting defects in roller shafts

　　In centrifugal casting of rolls, centrifugal vibrations give rise to compositional and microstructural lamellar segregation, which leads to the rapid propagation of cracks and ultimately results in roll fracture.

　　2) Microstructural defects in the roll

　　Nonconforming chemical composition and improper cooling rates can lead to defects such as compositional segregation and excessive cementite, resulting in degraded mechanical properties and ultimately fracture.

　　3) Manufacturing Process

　　During forging, insufficient forging pressure or improper deformation can result in incomplete penetration of the roll core, leading to transgranular cracks.

　　Its solutions:

　　1. The rolls are made from materials that exhibit both wear resistance and resistance to thermal cracking, and undergo appropriate heat treatment and surface chemical treatments to achieve a uniform microstructure and enhanced surface wear resistance. Prior to installation on the rolling mill, the rolls undergo comprehensive inspections, including hardness testing and ultrasonic examination, to ensure they are free of cracks and other defects.

　　2. During roll turning, thoroughly remove any residual oxide scale and cracks to minimize the occurrence of surface cracking and spalling on the rolls.

　　3. Reasonably schedule roll‑change intervals, select appropriate rolls, and develop a detailed roll‑turning and repair plan to keep the amount of turning and repair within specified limits. Additionally, properly configure the cooling‑water spray pattern and regulate the cooling‑water flow rate to ensure that roll‑cooling temperatures remain within the normal operating range.

　　4. Strengthen equipment inspections to prevent accidents involving rolling mill equipment, reduce incidents such as steel jams, steel buildup, and rear-end collisions, strictly control rolling temperatures, ensure that low‑temperature steel does not pass through the mill, and avoid overloading of rolling forces.