Rolling Mill Roller

The rolling mill roller is an important part of the rolling mill. According to the type of rolling mill, it can be divided into strip rolling mill, section rolling mill and steel tube rolling mill. The roll body of the strip mill is cylindrical, and the roll body of the hot strip mill is slightly concave. When heated and expanded, it can maintain a good plate shape; the roll body of the cold strip mill is slightly convex, which can ensure a good plate shape when it is forced to bend; the roll body of the section mill has a rolling groove, and the pass is arranged according to the rolling process requirements of the section steel. In the process of steel tube rolling, the roll which is rolled by the principle of cross rolling has the shape of cone, waist drum or disc.

According to the hardness of the roll surface, the roll can be divided into:

(1) Soft roll: Shore hardness is about 30 ~ 40hs, which is used in the roughing mill of the bloomer and large section mill.

(2) Semi hard roll: Shore hardness is about 40 ~ 60hs, used for roughing mill of large, medium, and small section steel mill and steel plate mill.

(3) Hard roll: Shore hardness is about 60 ~ 85hs, which is used for finishing mill and supporting roll of four high mill for sheet, medium plate, medium section, and small section mill.

(4) Super hard roll: Shore hardness is about 85 ~ 100hs, used in the cold rolling mill.

Techinical requirements

No matter hot rolling or cold rolling, roll is the direct tool to realize metal deformation in rolling process. Therefore, the quality of roll is strictly required. Its main quality requirements are strength, hardness, heat resistance and durability. Rolling strength is the most basic index. It must have certain impact toughness while meeting the strength requirements. In order to make the roller have enough strength, the selection of roller material and reasonable roller structure and size should be considered. Whether the roller strength is enough or not can be determined according to the calculation of roller strength.

Hardness usually refers to the hardness of the working surface of the roll, and it is also the main quality index of the roll. It determines the wear resistance of the roll and, to a certain extent, the service life of the roll. The hardness of the roller can meet the requirements through material selection and certain heat treatment of the roller surface. In addition, for the hot rolling roll, it should also have a certain degree of heat resistance to ensure the accuracy of the rolled products, but also determine the service life of the roll.

Material selection of common roll

1. Material selection of working roll

Working roll (R1) in the front section of rough rolling: the working roll in the front section of rough rolling must have strong toughness, wear-resistance and hot cracking resistance. The hardness range is about hs40-55. Generally, 60crnimo cast steel roll and other materials are used.

Work roll (R2) in the post roughing section: the work roll in the post roughing section shall be made of materials with good heat-resistant cracking performance. Generally, semi-steel, high chromium steel, high-speed steel, and other materials are selected.

Work roll (F1-4) in the front section of the finishing mill: the work roll in the front section of the finishing mill has a high temperature and heavy load. Generally, cast semi-steel and high chromium centrifugal composite cast iron are used. High chromium centrifugal composite cast iron has high wear resistance and hot crack resistance on the roll surface and can inhibit the roll surface spot defects.

Finishing work roll (F5-7): the use of finishing work roll in the final stage of rolling has a very important impact on product quality and surface state. For the roller performance, it mainly needs high hardness, wear resistance, pressure mark, peeling resistance, and hot crack resistance. Generally, infinite cold hard cast iron (common type, improved type) and other materials are used.

2. Selection of supporting roll and vertical roll materials

Whether it is used in rough rolling or finishing rolling, the back-up roll is required to have good heat crack resistance, wear resistance, fatigue resistance, and high strength. Generally, composite cast steel, alloy forged steel (chromium 3, chromium 5), and other materials are used.