What are the types of hot strip mill rolls and how to choose their material?

Hot strip rolling mill rolls can be divided into roughing rolls, vertical rolls, F1 to F3 finishing rolls, F4 to F7 finishing rolls, support rolls and complete rolls. The work roll of the two-high roughing mill should be made of cast steel or forged steel to bear greater bending stress and thermal cracking resistance, especially the composite casting work roll of hot tool steel containing 5%Cr. Because of the bending stress in rolling process by supporting roller bear, core can be used for composite centrifugal casting of ductile iron work roller, roller surface of high chromium cast steel and high chromium cast iron is generally selected material, recently, four roll roughing mill work roll after use of semi high speed steel and high speed steel composite work roll, can improve the service life of more than double, especially when rolling stainless steel, high speed steel roll use effect is better. Overall cast steel and semi-steel are generally used for vertical rollers. In recent years, the material of vertical rollers has been changed into centrifugal composite rollers with nodular cast iron core and high chromium cast iron roll surface on THE E3 and E4 racks. The service life of vertical rollers is about one time longer than that of cast semi-steel rollers.

The traditional material of F1 to F3 finishing rolls is cast semi-steel and high chromium cast iron. Since 1980s, the market share of HSS composite rolls applied on F1 to F3 stands is increasing. Its wear resistance and thermal cracking resistance are extremely superior, and effectively overcome the defects of roll surface spots, especially suitable for rolling stainless steel plate with high surface quality requirements. In recent years, high speed steel compound roll in F4 to F6 rack application also has a tendency to increase gradually, F7 stand still in use nickel-chromium molybdenum infinite chilled cast iron roll, in order to improve the nickel chromium molybdenum infinite chilled cast iron roll abrasion resistance and thermal crack resistance, by adding one strong carbide forming elements such as vanadium, niobium and refine the solidification organization, obtained the improved infinite chilled cast iron roll, The service life of roller can be increased by more than 20%. In steel rolling production, according to user requirements, part of hot rolled plates need to be leveled before delivery. For the four-roll machine, the support roller and the work roller used to choose centrifugal composite high ni-Cr infinitely chilled cast iron roll, in recent years, the use of high chromium cast iron roll, its wear resistance is 2 to 3 times higher than the high ni-cr infinitely chilled cast iron roll. However, for the two-roll flattener with roll bending function, its roll neck strength requirements are higher, can not use the casting roll, choose 5%Cr forged steel quenching material, the use effect is better.