RollerThe service life mainly depends on its internal performance and working stress, and the internal performance includes strength and hardness. In order to make the roll have sufficient strength, the material of the roll should be considered. Hardness usually refers to the hardness of the working surface of the roll, which determines the wear resistance of the roll, and to a certain extent also determines the service life of the roll. Reasonable material selection and heat treatment can meet the hardness requirements of the roll. Below, the small series will bring you together to understand the development of roll materials and heat treatment processes.

What many people don't know is that the cold roll bears a lot of rolling pressure during the working process, and the welding seam, inclusion, edge crack and other problems of the rolled piece are easy to lead to instantaneous high temperature, which makes the working roll crack, stick the roll and even peel off and scrap due to strong thermal impact. Therefore, the cold roll should have the ability to resist cracking and spalling caused by bending, torsion and shear stress, and should also have high wear resistance, contact fatigue strength, fracture toughness and thermal shock strength.

Therefore, from the late 1970 s to the mid-1980s, domestic and foreign research began to use chromium content of 3% to 5% of the deep-hardened layer cold-rolled work roll steel. However, these steels are high-carbon and high-alloy materials with good hardness and wear resistance, but the hardened surface of the roll is brittle, the contact fatigue life is short, and the quality is unstable. In order to improve the depth and contact fatigue life of the hardened layer, reduce the brittleness and overheating sensitivity of the hardened layer, and meet the further requirements of the rolling parts on the mechanical properties and performance of cold-rolled work rolls, starting from the middle and late 1980 s, abroad.RollerThe manufacturer optimizes the chemical composition of 5% Cr cold roll steel, mainly adding molybdenum and vanadium or titanium and nickel to 5% Cr steel. In a 5% Cr steel roll to which about 0.1% titanium is added, titanium is finely precipitated in the matrix in the form of TiCN. After the friction loss, TiCN falls off and scratches are formed on the surface of the roll, thereby regenerating moderate roughness. In the actual operation of tinplate rolling mill, the advantage of low roughness reduction is effectively used, and high-speed rolling can be realized from the early stage of rolling.

Looking forward to the future, the development direction of cold roll will be to further improve the strength, hardness and hardened layer depth while ensuring a certain toughness. Large cold rolling work rolls generally use improved 5% Cr steel containing vanadium, milling, nickel and other elements. In order to improve the hardenability of the material, the content of Cr will be further increased. For example, forged steel containing Cr 8% ~ 10% and higher has been used in actual production, but the increase of Cr content will lead to poor toughness. Therefore, it is necessary to properly balance the content of C and Cr, and quench at a lower temperature to obtain the required hardness of the cold roll, thereby reducing the fracture of the roll and its fracture sensitivity. In addition, with the further improvement of forging manufacturing technology, high-chromium steel work rolls will be more widely used in large-scale tandem cold rolling mills. 5% Cr and its vanadium-containing modified steel are widely used in large backup roll forgings, and large forged steel backup rolls with high chromium content have entered the practical stage.

In short, reasonable material selection and proper heat treatment can save a lotRollermaterials, reduce rolling production costs, improve roll quality and output.