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What is the failure analysis and countermeasures for rolling mill roll bearings?

What is the failure analysis and countermeasures for rolling mill roll bearings?

Roll bearing rolling mills are developed based on the replacement of previously used journal bearings. Compared with journal bearing rolling mills, their stability has been greatly improved. At present, steel mills in China need to widely use bearings to replace journal bearings, but it has been found that roll bearings often fail during use, which will have a great impact on production. According to statistics, the main factors causing roll failure are: assembly influence, improper lubrication influence, improper protection and foreign object entry, and overload. The following will analyze the causes of roll bearing failures and introduce measures to reduce roll bearing failures. 1. Failures caused by improper assembly of roll bearings One end of the roll bearing consists of four rows of short cylindrical roller bearings and a single row of deep groove ball bearings. In the steel rolling process, the radial force is mainly the main rolling force and the radial force generated during the rolling process, as well as the axial force generated during the rolling process. The radial force is shared by two bearings, and the axial force is mainly borne by the single row of deep groove ball bearings. Through analysis, it is found that this bearing allocation method has high load-bearing capacity, smaller bearing size than other bearing methods, and more accurate shaft positioning. In particular, the four-row short cylindrical roller bearings have high centering performance and high manufacturing accuracy. After consulting the bearing manual, it was found that the bearing clearance is less than 0.25 mm, which can meet the requirements of multiple disassembly.

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2022

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08

What are the causes of fracture in cold rolling rolls?

What are the causes of fracture in cold rolling rolls?

Currently, high-speed wire rod finishing mills generally consist of 8 to 10 rolling mills. Each rolling mill bears different rolling force and impact force. As the rolling pass increases, the speed of the roll ring will greatly increase, and the wear of the roll ring will also increase. Therefore, when selecting the material of the roll ring for each rolling mill, the impact force and wear resistance of each rolling mill should be fully considered. Otherwise, improper material selection will lead to roll collapse during finishing rolling, and the cause of roll collapse is difficult to identify. In each rolling mill during finishing rolling, due to the large cross-sectional size and deformation of the workpiece, the rolling load and impact force on the roll ring of the front stand are large. Therefore, the roll rings of the first few rolling mills of the finishing mill should use materials with high strength index and good resistance to thermal fatigue. The wear resistance index should be ranked second; however, the rolling load and impact force of the rear stand roll ring are smaller, so the wear resistance and resistance to thermal fatigue of the roll ring should be prioritized. Roll vibration and steel stacking during the finishing rolling process: 1. Poor roll matching High-speed wire rod mills have strict requirements on the inner roll rings of finishing rolling, because the high-speed wire rod finishing mill is collectively rotated by a 6000 kW variable frequency AC speed regulating main motor, and the gear ratio between each stand is fixed and cannot be changed. It is impossible to adjust the speed of a unit. The finishing mill is required to not only meet

17

2022

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08

Sharing relevant content about rolling mills

Sharing relevant content about rolling mills

Rolling mills are equipment used to perform metal rolling processes, generally referring to equipment that completes the entire rolling production process. Its working base consists of rolls, mill housings, bearing seats, bearings, independent coiling and uncoiling or payout platforms, base, roll adjusting device, top roll balancing device, and roll changing device. The rolls are the main working parts and tools for continuous plastic deformation of metal on the rolling mill, mainly consisting of the roll body, roll neck, and shaft.

08

2022

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08

Development history of roll materials and heat treatment processes

Development history of roll materials and heat treatment processes

The service life of a roll mainly depends on its internal performance and working stress. Internal performance includes strength and hardness. In order for the roll to 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, we will learn about the development of roll materials and heat treatment processes. Many people don't know that cold rolling rolls bear a lot of rolling pressure during operation. Problems such as welds, inclusions, and edge cracks in the workpiece can easily lead to instantaneous high temperatures, causing the working roll to crack, stick, or even peel off and be scrapped due to strong thermal shock. Therefore, cold rolling rolls should have the ability to resist cracking and peeling 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 1970s to the mid-1980s, domestic and foreign research began to use deep-quenched cold rolling work roll steel with a chromium content of 3%~5%. However, these steels are high-carbon, high-alloy materials with good hardness and wear resistance, but the quenched surface of the roll is highly brittle, the contact fatigue life is short, and the quality is unstable.

25

2022

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07

How should roll neck bearings be maintained?

How should roll neck bearings be maintained?

Roll and roll bearings are important components of rolling mills. In rolling production, the rolls are in direct contact with the rolled metal, causing plastic deformation of the metal. Therefore, the rolls are the main deformation tools of the rolling mill, and the rolls are supported by various bearings. The quality and service life of the rolls and roll bearings are directly related to the product quality, production efficiency, and production cost of the rolling mill. Therefore, the maintenance of roll bearings is particularly important. I. Working characteristics of roll bearings Roll bearings are used to support rolls. Compared with general bearings, roll bearings have the following characteristics: 1. Strong pressure bearing capacity. Due to the limitation of the overall size of the bearing seat, it cannot be larger than the smaller diameter of the roll body, and the roll neck is shorter, so the unit load on the bearing is larger. The unit pressure of general roller bearings is as high as 2000~4800Mpa, which is 2~5 times that of ordinary bearings, and the pv value (the product of unit pressure and linear velocity) is 3~20 times that of ordinary bearings. 2. Large speed difference. The operating speeds of different rolling mills vary greatly. For example, the exit speed of a modern six-stand cold rolling mill has reached 42m/s, and the exit speed of a high-speed wire rolling mill has reached 100m/s, while some low-speed rolling mills

18

2022

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07

Understanding Roll Materials and Common Issues

Understanding Roll Materials and Common Issues

Rollers are tools used for plastic deformation of (rolled) metals. They are important wearing parts that determine the efficiency of rolling mills and the quality of rolled materials. Rollers are an important part of rolling mills in steel plants. They use the pressure generated by a pair or a group of rollers to roll steel. They are mainly affected by dynamic and static loads, wear, and temperature changes during the rolling process. So, what are the characteristics and common problems of rollers? Let's take a look.

08

2022

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06

Below is a brief explanation of roll maintenance and production standards

Below is a brief explanation of roll maintenance and production standards

Below is a brief explanation of roll maintenance and production standards: Correctly judging the number of uses, the grinding interval of high-speed steel rolls depends on the oxide film on the roll surface and the retention of roughness after each shutdown. Generally, the front roll stand can be used 3-7 times, and the rear roll stand can be used 2-4 times. High-speed steel rolls can even be used more than 10 times.

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2022

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05

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