Improvement of Centrifugal Roll


Time:

2022/10/08

In view of the performance of high-speed centrifugal rolls, some powerful roll enterprises began to develop high-speed steel materials suitable for roughing and finishing mills. These two kinds of centrifugal rolls are different from the high-speed steel in the finishing part, and their performance design directions are as follows:

Given the high speedcentrifugal rollperformance, some of the strength of the roll enterprises began to develop high-speed steel materials suitable for roughing and finishing mills. These two kinds of centrifugal rolls are different from the high-speed steel in the finishing part, and their performance design directions are as follows:
 

离心轧辊的改进

(1) The rolling pressure of the roughing mill is higher, and the rolling temperature is the greater the bite angle of the roller,centrifugal rollThe greater the pressure and friction of the surface. Therefore, in view of wear resistance, the roller is required to have not only high strength and toughness but also high thermal crack resistance and crack growth resistance. Combined with the characteristics of roughing mill stand tool steel and high chromium steel, roughing mill stand high speed steel has the characteristics of low carbon, high chromium, high molybdenum, high vanadium, and low nickel, forming intermittent network carbides.

(2) Compared with finish rolling and rough rolling, the slab temperature of the rack after finish rolling is lower, the steel passing speed is faster, and the steel plate has a greater impact on the surface of the roll. Abrasive wear is the main form of wear. Rolls with poor wear resistance will affect the shape control of the strip section, and have higher requirements for the flatness of the roll surface. Therefore, centrifugal rolls are required to have high wear resistance and smoothness. For a long time, high Ni-Cr infinite chilled cast iron has been used for rolls in the later stage of finishing rolling. This cast iron contains fine graphite, which has a certain self-lubricating effect during the rolling process and has a good roll surface finish. However, with the development of the iron and steel industry, steel is developing in the direction of ultra-thin, and the use conditions of rolls are getting worse and worse. High nickel chromium infinite quenching material brittleness, rapid crack propagation and other defects gradually revealed, wear resistance gradually can not keep up with the development requirements.

The composition design of the later finished high-speed steel roll is characterized by high carbon, high molybdenum, high chromium, high vanadium and low tungsten, and a certain amount of niobium alloy is added to refine the structure, so as to form the microstructure characteristics of high carbide content, eutectic structure dispersion and fine particles, so as to realize the high wear resistance, high surface finish and good accident resistance of the roll.

(1) Material composite process:centrifugal rollUsing vertical centrifugal casting, divided into two layers of material (high-speed steel outer layer and core ductile iron) for multiple castings.

(2) Casting process: After the outer layer is poured, the inner surface is evenly covered with molten glass slag (liquid) to protect the surface from oxidation at high temperature. After the middle layer is solidified layer by layer through the external cooling mold, the appropriate pouring time and pouring temperature are selected according to the cavity temperature parameters. The warmer middle layer remelts a portion of the outer layer to fuse the inner and outer layers together. After the middle layer is poured for about 5 minutes, the core-filling molten iron is poured to complete the whole pouring process.

(3) After the pouring is completed, the whole cold mold is hung into the insulation pit, and the box is unpacked after holding for more than 7 days, and then the subsequent rough grinding, heat treatment, and processing of the green body are carried out.