What Is an Impact Roller?

The back-up roll is a spot color inspection on the surface of the back-up roll body and roll neck to detect whether there are crack defects on the surface.

Support roller

Right!

The back-up roll is a spot color inspection on the surface of the back-up roll body and roll neck to detect whether there are crack defects on the surface.

Chinese name

Support roller

Category

Welding repair

1 Flaw detection

Perform spot color inspection on the surface of the support roll body and neck to detect cracks on the surface; perform ultrasonic non-destructive inspection on the interior of the support roll to detect internal cracks, inclusions, and other defects, as well as the depth of cracks and inclusion defects to determine Can surfacing repair and roll turning volume.

2 roll surface turning

According to the requirements of the process, a single-sided cut is not small, and the hardened layer at 50mm is processed into a welding groove, and the designed thickness of the surfacing layer is guaranteed. Perform comprehensive inspection on the processed roller surface and welding groove to confirm that there are no defects in the roller. If local defects are still found, cut in the circumferential direction until there are no defects.

3 roll surface preheating

The roll enters the special heating furnace for preheating, and the preheating temperature is 400 500 ; the furnace temperature is controlled by the computer, and the temperature rise should be slow (30 40 / h); during the heating process, the support roller should rotate slowly and continuously, To ensure that the heating temperature is uniform, after the roll reaches the set preheating temperature, it is held for a certain period of time to ensure that the core temperature reaches the required preheating temperature.

4 roll surfacing

The surfacing layer is divided into 3 layers:

(1) It has high compressive strength and good rigidity, which is enough to withstand high rolling force and peak load;

(2) It has good toughness to avoid broken rolls, roll cracks and surface peeling;

(3) The working layer of the roller body has good abrasion resistance and fatigue resistance to reduce roller consumption;

(4) The working layer of the roller body has uniform structure and hardness, which makes the entire roller surface have uniform wear resistance;

(5) It has good corrosion resistance to resist high temperature and corrosion of lubricating or cooling medium during hot rolling.

(1) Optimize the roll profile system, and change the support roll profile from a flat roll to a double taper type with a taper value of 2 × 200mm to alleviate the rolling bearing capacity of the side of the roll; meanwhile, the rolling bearing capacity of the roll body will vary with the amount of wear Increase the position and change the position to avoid the concentration of rolling force on the shoulder of the roll.

(2) When the surfacing roll is used on the machine, only the upper roll is configured for the first two times to reduce the impact force on it. At the same time, the rolling cycle is shortened, and the total rolling volume is less than 60,000 tons to prevent welding stress from remaining inside the backup roll, and to avoid fatigue cracks caused by superimposing the fatigue stress and the limit value.

(3) When the surfacing rolls are used on the machine, priority is given to the production of low-grade steels such as ordinary carbon series. After the use of the rolls is stable, the production of low-alloy series plates will be gradually arranged.

(4) The grinding amount of the surfacing roller must be greater than 2mm, and the fatigue layer must be ground cleanly. ^[1]

1. Add softener to the quenching liquid to reduce the quenching intensity.

2. Reduce the heating time in the middle of the support roller to about 80s, and keep the heating time on the upper and lower sides to 3-4s. Increase the number of up and down cycles, and up and down cycles 8 times. During the cycle, the supporting roller rotates at a speed of 800 rpm. Through a small number of multi-frequency methods, the heating temperature of the rough roller is uniform.

3. Increase the water spray pressure and control the water spray time above 90s, completely change the phenomenon of water spray while heating before, causing less cycles of up and down and uneven temperature during cooling.

4. Improve the height of the high-frequency coil to make the heating area larger and prevent the temperature gradient from being too steep. The heat treatment method tends to the surface full-section treatment property.