Types of rolls used in rolling mills

1. Rolls are mainly divided into three categories according to the material:

cast iron rolls, cast steel rolls and forged steel rolls. Among them, the carbon content of cast iron rolls is about 2.5% to 3.5%.

According to the main materials, it can be divided into four categories: chilled cast iron rolls, infinite chilled cast iron rolls, high chromium cast iron rolls and ductile iron rolls.

The common structures of cast iron rolls can be divided into three categories: matrix, cementite, and graphite. The matrix structure mainly includes austenite, ferrite, pearlite, bainite, and martensite. The shape of graphite in cast iron is general. There are two kinds of flake and spherical.

Cast steel rolls can be divided into two categories: steel rolls (carbon content 0.4% ~ 1.4%) and semi-steel rolls (carbon content 1.4% ~ 2.4%).

Steel rolls have low carbon content, so their hardness is low, and their structure is generally composed of the composition of ferrite and pearlite, as the carbon content increases, the number of ferrite decreases, and the number of pearlite increases. In order to improve the hardness, alloy elements such as chromium, nickel, manganese, molybdenum, and vanadium can be added, or special heat treatment can be carried out. Due to the high tensile strength and toughness of steel rolls, it is suitable for billet rolling mills or blooming mills with high rolling temperatures and large rolling loads, and can also be used as backup rolls such as special heat treatment to obtain high hardness above HS90. Do cold rolled work rolls.

The carbon content of the semi-steel roll is between the cast steel roll and the cast iron roll, and its hardness is higher than that of the general cast steel roll and lower than that of the cast iron roll. The main feature of the semi-steel roll is that the internal hardness drop is very small, so it is especially suitable for the manufacture of deep-hole roll forgings. If the silicon content is increased in the semi-steel roll material, it has high thermal crack resistance and strong toughness through graphitization treatment. Vertical roll can obtain a good rolling effect. Through smelting, forging and heat treatment of forged steel rolls, the working layer of the roll body has high hardness, high wear resistance and excellent accident resistance, while ensuring that the roll neck and the core of the roll body have certain strength and high toughness. This unique property of forged steel rolls makes them irreplaceable for cast rolls in cold rolling and non-ferrous rolling.

types of rolls used in rolling mills

2. Rolls are divided into casting rolls and forging rolls according to forming methods and are divided into integral rolls, metallurgical composite rolls, and combined rolls according to process methods.

Integral rolls are divided into integral casting and integral forging rolls. The outer layer, core, and roll neck of integral rolls are cast or forged from a single material. The outer layer of the roll body and the roll neck have different structures and properties. Forging process and heat treatment process to control and adjust. Metallurgical composite casting rolls mainly include semi-flushing composite casting, overflow (full flushing) composite casting, and centrifugal composite casting. In addition, there are continuous casting outer layer forming methods, electro slag casting composite methods, spray deposition methods, and thermal isostatic Composite rolls manufactured by special methods such as pressing.

Combination rolls are mainly inset and sleeve combination rolls. The use of inset and sleeve combination rolls instead of cast composite rolls is an effective measure to solve the problem of roll breakage. The outer layer (roll sleeve) of the roll and the roll shaft is fitted through interference. In order to ensure the torque required for rolling, it is usually necessary to open a keyway or process a threaded hole on the inside of the roll sleeve, and use splines or bolts to make the roll sleeve and the roll shaft. Bond firmly. The use of combined rolls has a good effect on solving broken rolls, reducing roll consumption, and improving the steel rolling operation rate. In addition, the roll shaft of the combined roll can be reused. In the manufacture of the combined roll, only the roll sleeve is smelted and processed, which can reduce the energy and power consumption of the roll production, which is conducive to energy saving and emission reduction.

3. According to the type of rolling mill, the rolls can be divided into the following three categories:

(1) Flat rolls, that is, rolls of strip mills, whose roll bodies are cylindrical. Generally, the rolls of the hot-rolled steel plate mill are made into a slightly concave shape, and when heated and expanded, a better shape can be obtained; the rolls of the cold-rolled steel plate mill are made into a slightly convex shape, and the rolls are bent during rolling to obtain a good shape. .

(2) Rolling bar with tip, which is used for rolling large, medium, and small sections, wire rods, and blooming. Grooves are engraved on the roll surface to shape the rolling stock.

(3) Special rolls, which are used in special rolling mills such as steel pipe rolling mills, wheel rolling mills, steel ball rolling mills, and piercing mills. The rolls of this rolling mill have various shapes. For example, the rolls rolled by the principle of skew rolling in the steel pipe rolling are conical, waist drum, or disc.

4. According to the product type, there are strip steel rolls, section steel rolls, wire rod rolls, etc.;

5. According to the position of the rolls in the rolling mill series, there are billet rolls, rough rolls, finishing rolls, etc.;

6. Rolls can be divided into work rolls, intermediate rolls, and backup rolls according to their uses.

7. According to the state of the rolled steel, there are hot rolls and cold rolls.

Various classifications can be combined to make the rolls have more specific meanings, such as centrifugally cast high-chromium cast iron work rolls for hot-rolled strips.

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