Roll Classification

　　There are various methods for classifying rolls, mainly: (1) According to product type, they are divided into strip rolls, shaped steel rolls, wire rolls, etc.; (2) According to the position of the rolls in the rolling mill series, there are opening rolls, roughing rolls, finishing rolls, etc.; (3) According to roll function, there are descaling rolls, piercing rolls, leveling rolls, etc.; (4) According to roll material, there are steel rolls, cast iron rolls, cemented carbide rolls, ceramic rolls, etc.; (5) According to manufacturing method, there are cast rolls, forged rolls, weld-deposited rolls, inlaid rolls, etc.; (6) According to the state of the rolled steel, there are hot rolls and cold rolls. Various categories can be combined to give rolls a clearer meaning, such as a high-chromium cast iron working roll for hot-rolled strip steel made by centrifugal casting. Common roll materials and uses are shown in the table. The performance and quality of a roll generally depend on its chemical composition and manufacturing method, and can be evaluated through its microstructure, physical and mechanical properties, and the type of residual stress inside the roll (see roll inspection). The performance of a roll on a rolling mill depends not only on the material and metallurgical quality of the roll, but also on the operating conditions, roll design, and operation and maintenance of the roll. Different types of rolling mills have very different rolling conditions. Factors causing differences include: (1) Rolling mill conditions. Such as rolling mill type, rolling mill and roll design, roll pass design, water cooling conditions, and bearing type; (2) Rolling conditions, such as rolling mill variety, specifications and deformation resistance, pressure system and temperature system, output requirements and operating conditions; (3) Product quality, surface quality, etc. 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 the initial rolling mill for steel billets and slabs should have good torsional and bending strength, toughness, bite force, hot 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, spalling resistance, and hot cracking resistance.

　　To correctly determine Roll the technical conditions, and select suitable and economical materials, it is necessary to understand the properties and manufacturing processes of various roll materials, and clarify the operating conditions of the rolls and the failure modes of rolls in the same type of rolling mill.

　　Commonly used methods for evaluating the performance of rolling mill rolls include: (1) Roll consumption (kg) per ton of rolled material (referred to as roll consumption), expressed as kg/t; (2) Reducing the weight of rolled material per unit roll diameter, expressed as T/mm.

　　With the modernization of rolling mills, in-depth research on roll failure, and improvements in roll materials and manufacturing technologies, the average roll consumption in developing industrial countries has been reduced to less than 1 kg/t. Usually, the main requirements are the strength and hot crack resistance of the roughing rolls; the working roll weight of a small 20-hour rolling mill is only about 100 grams, while the supporting roll weight of a wide and thick plate rolling mill can reach more than 200 tons. When selecting rolls, according to Roll the basic strength requirements of the rolling mill, the main materials (cast iron, cast steel, or various grades of forged steel) for safe bearings are selected. When the speed of the finishing rolls is high, the product of the rolls should have certain surface quality, hardness, and wear resistance as the main requirements. Then consider the wear resistance of the rolls during use. Because the wear mechanism of rolls is complex, including the effects of mechanical stress, thermal effects during rolling, cooling effects, and chemical effects of lubricating media, there is currently no unified index to comprehensively evaluate the wear resistance of rolls. Because hardness is easy to measure and can reflect wear resistance under certain conditions, the radial hardness curve is generally used to approximate the wear resistance index of rolls.