Metallurgy is one of the main branches of modern production. It is thanks to her that enormous financial revenues go to the state budget, because steel and cast-iron products, as a rule, are exported and generate foreign exchange earnings of both the plant or the plant and the country. There are various metallurgical enterprises, the working cycle of which can be either complete or incomplete. But in any case, the final stage of the metallurgical cycle will be metal rolling in order to obtain the profile required by the consumer. It is in the rolling shops that produce beams, channels, rails and more. The main elements of any rolling mill are rolling rolls. The factories of the metallurgical complex without them are simply inconceivable, so we will talk about rolls in detail in this article.
general description
Metal rental - the operation is quite complicated, energy-intensive and requires special skills and knowledge from the staff. The compression of the material that produces the roll, allows you to achieve certain dimensions of the processed profile. It is important to know that the rolls in the course of their work take on an impressive effort, which occurs directly in the process of the entire rolling line. That is why the rolling roll is the most wearing part of any rolling mill.
Parts and Features
All rolls have three main components, including:
- Barrel roll. It is she who is in direct contact with the red-hot and processed metal. The barrel has two main linear parameters - length (L) and diameter (ØD).
- The necks (supporting parts) are located on the sides of the barrel and are supported by roller bearings. Also characterized by length and diameter.
- Drive end.
For the roll mill, the main indicators are: nominal diameter, diameter of the shoulders and working diameter. In those cases where the roll is used to rotate using a universal type spindle, its drive end will be in the form of a blade or cylinder. The drive end will have the appearance of a cross, if rotation of the roll with the help of the shaft is provided (an intermediate coupling is required).
Sheet metal rolls
Sheet rolling rolls, the manufacture of which is a rather time-consuming process, perform rolling of tape and strips. The barrel of such rolls is smooth, made in a cylindrical shape.
Rollers are used for the manufacture of shaped material, which can have both round and square sections (I-beams, corners).
Barrels of rolling rolls are made slightly convex if they are intended for cold rolling of sheet products. In other cases, for hot rolling the roll barrel is given a concave shape. This is done because at the moment the metal moves along the roll, its barrel will heat up and straighten.
Rollers for long products
The barrel of such rolls has special recesses (streams) that repeat the profile of the metal subsequently rolled. The streams of a pair of rolls when connected to each other form a caliber. The length of the barrel of high-quality rolls depends on the width of the rolled workpiece and the calibration conditions.
Varietal rolls are characterized by a nominal diameter and barrel length. If the mill has many stands and rolls of various diameters, then the diameter of the finishing stand rolls will be dominant.
According to the purpose of varietal rolls are divided as follows:
- For heavy crimping mills.
- For coarse and rail and beam mills.
- For mid-range rental.
- For small sections.
- For wire mills.
- For strip mills.
Centrifugal casting
Modern production of rolling rolls as one of the main methods involves a centrifugal casting method . This method is very expensive, however, it fully allows you to maximize compact the metal structure of the outer surface, which is the working surface of the roll. This approach can significantly increase the life of the product.
For this method, a special machine is used having a horizontal axis of rotation of the shape of centrifugal casting. The form itself is mounted on support rollers. The drive rollers are mounted in such a way that they fully ensure synchronization of the rotation process. The safety roller located above has a gap relative to the skating rim of the form itself. There are damping pads to absorb vibration between the rollers and the hub. Reducing the level of vibration and fluctuations in shape reduces to zero the probability of marriage.
Centrifugal casting of rolls is carried out from high-alloy cast iron. A metal is poured into a chill mold rotating around its vertical axis, the volume of which is within 95% of the total volume of the working layer of the rolling roll.
The indisputable advantages of centrifugal casting are:
- Providing high roll density.
- Improving the wear resistance of the roll.
- The absence of shells, voids, non-metallic inclusions, slag.
Forging method
This is the most expensive method for the production of rolling rolls, which nevertheless makes it possible to fully harden the entire body of the roll. Due to this, reliability and durability are significantly increased.
Forging itself is performed on special automated complexes designed and manufactured using advanced technologies. The power of these units can be up to 150 MN.
The rolls obtained in this way are most often used on blooms and slabs, as well as high-quality mills. These steel rolls have an increased coefficient of friction at the moment of contact with the rolled billet. This nuance is extremely important for stands with a high degree of reduction.
Forging itself involves the following operations:
- Billet ingot.
- Upset.
- Broach.
- Forged to size forgings.
Processing of rolls after forging involves complex heat treatment, the final stage of which is certainly surface hardening and tempering.
Titanium production
Today, Russia is one of those countries that regulate the global market for steel and alloys. Therefore, the creation of components and parts for metallurgy in the country has been given the closest attention. In particular, the Magnitogorsk plant of rolling rolls is one of the leaders in the production of these products.
In July 2016, new high-performance crucible induction furnaces were launched at this enterprise . These high-tech units will allow the production of complex alloys, reduce the amount of ferroalloys and charge consumed. In this case, the reduction in electricity consumption will be about 10%. The melting mode can be carried out with a frequency of 250 Hz, and refinement and mixing with a frequency of 125 Hz. Compliance with environmental requirements is also important: reduction of harmful emissions on these furnaces will occur by 2.6 times.
In general, the Ural enterprise regularly supplies the market for rolling rolls with its products and is an actively developing enterprise.
Sverdlovsk giant
You can also not ignore the Kushva roll mill. Its products are all kinds of rolls, bandages for them. At the enterprise, rolls of rolling mills are made using such materials for the working layer as:
- Indefinite.
- Indefinite improved with special carbides.
- High chromium cast iron.
- High chromium steel.
- High speed steel.
The necks and the core of the sheet rolls are made of especially durable cast iron.
Rolls for section rolling mills are made on the basis of bainitic and pearlitic alloyed cast irons with spherical or lamellar form of graphite.
Ukrainian manufacturers
In Ukraine, there are three main enterprises for the production of rolling rolls: Dnepropetrovsk, Lutuginsky and Novokramatorsky rolling mill plants.
The Dnieper plant has a wide range of roll production, not only for metallurgy, but also for other industries. Very often, an enterprise works for a specific customer, connecting its highly qualified specialists from the technical department to create a variety of drawings and new models of rolls.
Before the outbreak of hostilities in the Donbass in 2014, the Lutuginsky roll mill was consistently included in the cohort of the best. Its products were supplied not only to all metallurgical enterprises of Ukraine, but also to many countries of the near abroad and Europe. However, the military conflict led to the fact that the plant was stopped. The main assets of the enterprise were also affected. But nevertheless, in 2015 it was possible to restart the enterprise, and today it has begun to receive orders from the Russian Federation.
Roll Quality Control
In the manufacturing process, absolutely every rolling roll undergoes the procedure of technical quality control of its manufacture. Particular attention is paid to:
- The chemical composition of the source material.
- Analysis of the structure of the product material (roll).
- Analysis of centricity and geometric dimensions.
- Control the degree of hardness of the working layer of the roll.
- Control the degree of roughness of the working surface.
- Analysis of the metal structure of the surface layer.
Packaging
All rolling rolls (the factories producing them have appropriate quality certificates) are delivered to the consumer in special packaging. This container is often a wooden box with partitions, inside which the rolls are stacked and securely fastened with coupling elements. Manufacturers also pay close attention to the packaging container, because poor attachment of the rolls and the lack of proper protection of the working and landing surfaces of the industrial product may well lead to negative consequences on the quality of the rolls.
Conclusion
Rolling rolls, the production technology of which was discussed in detail above, have a significant impact on the products obtained as a result with their help. Therefore, the world's leading manufacturers of rolled products pay special close attention to this element. Each head of the metallurgical enterprise is well aware that the final profitability of the entire production will largely depend on the technical condition of the rolling mill as a whole and the rolling rolls in particular.