According to the rolling materials, passes, reduction, rolling speed, and rolling varieties, the roll materials and the hardness of the roll body working face shall be selected reasonably. The principle of using mill rolls is: high hardness is applicable to finish rolling, medium hardness is applicable to intermediate rolling, and low hardness is applicable to blooming. The rolls must be used according to the corresponding stand to avoid misuse or mixing when selecting roll materials. Pay attention to the following items when using mill rolls:
1. Roll shall be protected from any collision damage during handling.
2. The mill roll shall be stored in a dry and ventilated room to prevent moisture, and the surface shall be coated with antirust oil.
3. Before the mill roll is used, the oil stain, dust, and rust on the surface shall be wiped off, and then a routine inspection shall be carried out to check whether there are scars (including indentation, rust spot, crack, and other defects) on the surface of the roll body and roll neck. It is not allowed to use the mill rolls with surface defects on the machine.
4. Before the roll is put into use, a roll quality account shall be established to record the roll number, specifications and dimensions, and relevant inspection results, and the original records shall be filed.
5. The installation of the mill roll shall be done carefully. Before the installation of the roll journal bearing, all sundries shall be removed. The assembled bearing must be accurate and in place. The horizontal and vertical parallelism on the rack shall be corrected on-site to prevent scratching or bumping the roll surface.
6. Before rolling, the quality of rolled billets shall be carefully checked, and the operation shall be carried out in strict accordance with the rolling process. The rolling of low-temperature steel shall be avoided to prevent overload from affecting the service life of mill rolls and breaking of mill rolls.
7. The mill roll shall meet sufficient cooling and lubrication conditions during rolling, reduce the thermal corrosion, thermal fatigue, and thermal stress of rolled products on the roll surface, and prevent hot cracks, chipping, and spalling during rolling. Ensure the lubrication between each transmission shaft to prevent quality accidents caused by transmission obstruction.
8. Cooling water used in rolling shall be neutral to prevent contamination by impurities. Water with strong acidity or alkalinity will corrode rolls. The water temperature shall be kept ≤ 30 ℃, and the quality, water temperature, and water pressure of cooling water will directly affect the wear resistance of rolls.
9. During the rolling process, it is required to prevent the rolled products from deviation, overlapping, piling up steel, or bringing in foreign matters, and prevent corrosion objects from embedding into the metal, damaging the roll, and causing the roll to be scrapped.
10. The hot rolling rolls replaced from the rolling mill shall not be stacked on the wet and cold ground to prevent uneven heating and corrosion of the roll surface from affecting the service life, and direct collision between rolls shall be avoided.
11. Establish a reasonable roll change cycle, formulate a roll change grinding system, and cooperate with the corresponding nondestructive testing methods to ensure that the processing turning, and grinding processes conform to the grinding system.
12. During the processing, cutting, or grinding of the work roll, the minimum cutting amount and grinding amount for each processing shall ensure that the fatigue layer is eliminated. The depth of this layer is generally 0.15-0.30mm. If it is found that the thermal fatigue cracks on the roll surface are serious, the fatigue layer shall be completely removed (the depth of this layer is generally 2-5mm) to prevent the cracks from extending and causing peeling.
