Mill Rolls

The performance and quality of the rolls generally depend on their chemical composition and manufacturing and can be assessed by their metallographic tissue, physical and mechanical properties, and residual stress type present in the mill roll.

The use effect of mill rolls in the mill is not only dependent on the material of the roll and its metallurgical quality, and it is also related to the conditions, roll design, and operation maintenance.
There is a big difference in the use conditions of rolls of different types of mills, resulting in differences:

• Rolling mill conditions. Such as rolling mills, rolling mills, and mill rolls design, hole design, water-cooled conditions, etc.
• Rolling conditions such as rolling products, specifications, and deformation resistance, depression systems, and temperature systems, yield requirements, and operations.
• Requirements for product quality and surface quality.

Therefore, different types of rolling mills and rolling mills are used in the same type, which requires no thunder, such as bullet and slab initial rolling rolls to have good twists and bend strength, toughness, bitterness, Anti-thermal cracking and thermal impact and wear resistance; and the tropical finishing rack requires high hardness, resistance, wear-resistant, anti-flakes and heat-resistant cracks such as roll surface.

To clarify the use conditions of the roll and the failure of the rolls used in the same type of rolling mill to understand the performance and manufacturing process of the current various rolls, in order to correctly formulate the technical conditions of the rolling mill and the selected suitable and economical roll material.
The most common method of evaluating the performance of the roll in the mill is:

• Rolling the rolling weight (kg) (referred to as the roll consumption) consumed by the 1t rolling material, expressed by kg/t;
• Reduce the weight of the rolled material per unit roll, expressed with t/mm.

With the modernization of the rolling mill, the in-depth study of the fading of the rolls and the improvement of roll materials and manufacturing processes, the average roll consumption of industrially developed countries has decreased below 1kg/t.

What are the performance requirements of the mill rolls?

• Anti-thermal crack: Typically, the coarse roll is mainly required, and the thermal crack is mainly required; the working roll of the small 20 rolling mills is only 100 grams, while the weight of the support roller of the wide plate roller has exceeded 200 tons. When the roll is used, the safety-loaded body material (various levels of cast iron, cast steel or forged steel, or the like) is selected according to the basic strength of the roll.
• Hardness: The finishing roller speed is high, and the final product of rolling should have a certain surface quality, which is mainly required to hardness, wear resistance, etc. The wear resistance should then be considered when the roll is used. Since the wear mechanism of the roll is complicated, including mechanical stress, the thermal action, cooling effect, the chemical effect of cooling effect, lubrication medium, and other effects, no comprehensive evaluation of the anti-wear resistance of the roll resistance. Since the hardness is easy to measure, and the wear resistance can be reflected under certain conditions, the wear-resistant indicator of the roll is generally expressed in the radial hardness curve.
• Impact Resistance: In addition, there are some special requirements for the roll, such as the amount of pressure, which requires a strong bit bite ability, more impact.
• Degree of finish: When the thin size product is rolled, the rigidity, tissue performance uniformity, processing accuracy, and surface finish of the roll are strictly required.
• Cutting performance: When rolling the complex section, the cutting performance of the roller working layer is considered.
  When the roll is selected, some of the performance requirements of the roll often are opposite each other. The roll purchase fees and maintenance costs are very expensive, so we should fully weigh the techniques and economical pros and cons decided to cast or forged, alloys or non-alloys, Single material or composite.

There are a variety of classification methods of mill rolls, mainly:
(1) According to the product type, there is a steel roller, type steel roll, wire roll, etc.

(2) Press the roll in the roll series in the mill series, there is a blank roll, a thick roll, and a finishing roll or the like;

(3) Press the rolling function to divide the roller, perforated roll, flat roller, etc.

(4) According to the roll material, steel rolls(High-Speed Steel Rolls), cast iron rolls, Tungsten Carbide Rolls, ceramic rolls, etc.

(5) According to the manufacturing method, there is a cast roll, forged rolling roller, a stainless rolling roll, a set roll, etc.

(6) Press the rolled steel state with a Hot Mill Roll and Cold Mill Roll.

Various classifications can be combined to make the rolls more clear, such as hot-rolled steel for centrifugal steel working rolls.

Variety and manufacturing process of mill rolls with the progress of metallurgical technology and the evolution of rolling equipment.

1. Medieval rolling soft non-ferrous metallic rolls.
2. In the middle of the 18th century, Yeying, Master the production technology of cold cast iron rolls for rolled steel sheets.
3. The advancement of European steelmaking technology in the next half of the 19th century requires rolling a larger tonnage of steel ingots, whether it is the strength of the gray cast iron or the cold cast iron rolls, with no requirements. The carbon content is 0.4% to 0.6%, the ordinary cast steel roller is born. The emergence of heavy-duty-duple forging equipment is further improved by the strong toughness of the forging rolls of this component.
4. The introduction of alloying elements of alloy elements in the early 20th century significantly improves the wear resistance and toughness of cast steel and forged steel hot rolls and cold rolls. The surface quality of the rolled material is improved in the cast iron roll of the hot-rolled sheet. The composite casting of the rinsing method significantly increases the core strength of the cast roll.
5. A large number of alloy elements in the roll is after the Second World War, this is the rolling equipment towards large, continuous, high speed, automation, and improved the strength of the rolling, and the deformation resistance increases higher requirements. the result of. A semi-steel roll and a ductile iron roll occurred in this period.
6. After the 1960s, it was also developed successfully the powder tungsten carbide roll.
7. In the early 1970s, the comprehensive performance of the roll rolls in Japan and Europe in the early 1970s, the overall performance of different temperature heat treatment technology, etc. Composite high chromium cast iron rolls are also successfully used in a tropical rolling mill. In the same period, forging white mouth iron and semi-steel rolls were applied in Japan.
8. In the 1980s, Europe also introduced high-chromium rolls and ultra-deep hardening cold rolls, and special alloy cast iron rolls for small steel and wire finishing rolling. The development of contemporary rolled steel technology has prompted the development of higher performance rolls.
9. Using centrifugal casting method and new composite method such as continuous casting compound (CPC), injection deposition method (Osprey method), electroflag welding method, and heat-like, a forged steel or pneumo Cast iron, the outer layer of high-speed steel series composite rolls and metal-ceramic rolls have been applied to Europe, Japan new generation profiles, wire, steel mills.