RollerClassification

There are many classification methods for rolls, mainly including:(1) according to product types, they are divided into strip rolls, special-shaped steel rolls, wire rolls, etc.;(2) According to the position of rolls in the rolling mill series, there are open rolls, rough rolls, finish rolls, etc. (3) According to roll functions, they are divided into scale breaking rolls, perforated rolls, leveling rolls, etc. (4) According to the material of rolls, there are steel rolls, cast iron rolls, carbide rolls, ceramic rolls, etc.;(5) according to the manufacturing method is divided into casting rolls, forging rolls, surfacing rolls, inlaid rolls, etc.;(6) according to the state of rolled steel is divided into hot rolls and cold rolls. Various categories can be combined accordingly, so that the roll has a clearer meaning, such as centrifugal casting of high chromium cast iron work rolls for hot strip steel. Common drum materials and uses are shown in the table. The performance and quality of a roll generally depends on its chemical composition and manufacturing method, and can be evaluated by its microstructure, physical and mechanical properties, and the type of residual stress inside the roll (see roll inspection). The effect of the roll on the rolling mill depends not only on the material and metallurgical quality of the roll, but also on the conditions of use of the roll, roll design, operation and maintenance. The rolling conditions vary greatly for different types of mills. The factors contributing to the difference are:(1) mill conditions. Such as mill type, mill and roll design, pass design, water cooling conditions and bearing types; (II) rolling conditions, such as mill varieties, specifications and anti-deformation capacity, pressure system and temperature system, output requirements and operation;(3) Product quality, surface quality and other requirements. Therefore, different types of rolling mills and the same type of rolling mills have different operating conditions, and the performance requirements of the rolls used are also different. For example, the rolls of billet and slab primary rolling mills should have good torsion and bending strength, toughness, bite force, thermal crack resistance, thermal shock resistance and wear resistance; The hot strip finishing mill frame has high requirements for roll surface hardness, indentation resistance, wear resistance, peeling resistance and thermal cracking.

To correctly determineRollerThe technical conditions, the selection of appropriate and economical materials, it is necessary to understand the performance and manufacturing process of various roll materials, clear the conditions of use of the roll and the failure mode of the same type of mill roll.

The commonly used methods for evaluating the roll performance of rolling mills are:(1) the roll weight (kg)(referred to as roll consumption) consumed by rolling 1t rolling materials, expressed as kg/t;(2) Reduce the weight of rolling materials per unit roll diameter, expressed in T /mm.

With the modernization of rolling mills, in-depth research on roll failure and improvement of roll materials and manufacturing technology, the average consumption of rolls in industrial developing countries has been reduced to less than 1 kg/t. Usually rough roll strength, heat cracking resistance as the main requirements; small 20 hours mill work roll weight is only about 100 grams, and wide plate mill support roll weight up to more than 200 tons. In the selection of rolls, according toRollerThe basic strength requirements of the rolling mill, select the main material of the safety bearing (cast iron, cast steel or forged steel of various grades). When the finishing roll speed is high, the roll product should have a certain surface quality, hardness, wear resistance, etc. as the main requirements. The wear resistance of the roll in use is then considered. Due to the complexity of the wear mechanism of rolls, including mechanical stress, thermal effect in the rolling process, cooling effect, chemical effect of lubricating medium, etc., there is no unified index for comprehensive evaluation of the wear resistance of rolls. Because the hardness is easy to measure and can reflect the wear resistance under certain conditions, the radial hardness curve is generally used to approximate the wear resistance index of the roll.