RollerIt is a tool for plastic deformation of (rolling) metal and an important vulnerable part that determines the efficiency of the mill and the quality of the rolled material. Roll is an important part of the rolling mill in the rolling mill. It uses the pressure generated by a pair or a group of rolls to roll steel. It is mainly affected by the rolling process of dynamic and static load, wear and temperature changes. So, what are the characteristics and common problems of the roll? Let's look at it together.

Classification and Material of 1. Rolls

1. Classification: There are two types of rolls usually used, namely cold rolling rolls and hot rolling rolls.

There are many kinds of materials made by cold rolling, such as 9Cr, 9Cr2, etc. This type of roller has two requirements: one is. The surface of the roller needs to be quenched; second, its surface hardness needs to be between HS45 and 105.

The material of the hot rolling roll is generally 60CrMnMo, 55Mn2, etc. This type of roll can be used in a wide range of fields, such as steel, bar, rebar, high-speed wire, seamless steel pipe, billet cutting, etc. It withstands strong rolling forces, severe wear and thermal fatigue. Moreover, the hot roll has a high working temperature and allows the diameter of the unit workload to wear, so it does not require surface hardness, but only requires high strength, toughness and heat resistance. The hot roll is only normalized or quenched as a whole, and the surface hardness requires HB190 ~ 270 hardness.

2. commonRollerFailure forms and causes

1. Cracks. The cracks are mainly caused by excessive local pressure and rapid cooling and heating of the rolls. On the rolling mill, if the emulsion nozzle is blocked, resulting in poor local cooling conditions of the roll, cracks will occur. Because the temperature is low in winter, it is easier to crack than in summer.

2, peeling. If the crack continues to develop, it will form a block or flake. Those with light peeling skin can be polished again, and those with serious peeling skin will be scrapped.

3. Pit marks. Pit marks are mainly due to the weld or other debris of the strip into the rolling mill, leaving different shapes of pit marks on the surface of the roll. Usually, the grooved roller needs to be replaced. When the quality of the strip steel weld is not good, when the rolling operation passes through the weld, it should be raised and pressed to prevent scratches.

4, sticky roller. The reason why sticky rolls are also called sticky rolls is that there are broken pieces, wave folds and broken edges in the cold rolling process, and the bonding between the steel strip and the rolls is easy to form under high pressure and instantaneous high temperature, resulting in small area damage to the rolls. Through grinding, after eliminating surface cracks, the roller can still be used, but the service life is significantly reduced, and peeling accidents are prone to occur in future use.

5, clip stick. It is mainly due to the heavy skin of the strip steel caused by excessive pressure or slight folding and the heavy skin caused by the deviation of the strip steel. When the roller is severely clamped, the roller will be stuck and the strip will crack. When the pinch roller is slight, there are pinch marks on the strip and the roller.

6, broken. The main cause of roll fracture is overpressure (I. e. excessive rolling pressure),RollerInternal defects and stress fields caused by non-uniform roll temperature.