Steel rolling basics Q&A – part II

1. What are the adjustment devices of the rolling mill?

The short stress line rolling mill has been developed to cancel the rolling mill stand arch, so it is generally a no arch rolling mill. The short stress line mill has the following characteristics:

1) Negative tolerance rolling is easy to achieve. Because the high rigidity of the rolling mill ensures the high precision of the product.

2) The symmetry adjustment can be realized.

3) The roll system of the rolling mill can be pre-installed and adjusted before the roll change, and the new roll system can be replaced after about 10 minutes after stopping, and the pre-adjusted new roll system can ensure that the product is qualified after rolling one or two steels. Therefore, the rolling mill has good pre-adjustment performance, fast roll change and high yield.

Upper roller adjustment device: to realize the pressing or lifting of the upper roller. There are three common types: a manual pressing, with gear and screw structure, mainly used in section steel rolling mills. B electric pressing, there is an electric upper roller adjustment structure, and there is also an adjustment structure through a first-stage worm gear and a two-stage cylindrical gear. Generally, blooming mills, steel plate mills, etc. use electric upper rollers to adjust the structure. C hydraulic pressure.

The lower roller adjustment device can realize the lifting or falling of the lower roller. There are two commonly used forms: a. The adjustment structure under the gear screw; b. The adjustment structure under the oblique block screw.

Middle roll adjustment structure: The three-roll section steel rolling mill is generally fixed, but due to the wear of the roll neck and bearing bush, the middle roll will be loose, which will cause a large change in the pass of the lower rolling line. The middle roller is used to adjust the structure to ensure the fixed position of the middle roller.

Axial adjustment device: realize the axial movement of the roll. There are two commonly used structural forms: a side pressure plate, which is the most used axial adjustment structure at present; b hook bolt.

2. What safety devices does the rolling mill have?

1) The safety mortar is installed between the pressing screw of the rolling mill and the upper and lower roll bearings, and is equipped with a protective cover. When the rolling force exceeds the allowable value, the rupture of the safety mortar increases the distance between the rolls, thereby protecting the rolls. The material of the safety mortar is generally hard and brittle cast iron. Its strength should be lower than that of the roll, and cast steel or forged steel should not be abused.

2) The plum blossom bushing is loaded on the plum blossom head of the roll. When the rolling torque exceeds the allowable torsion torque, the plum blossom bushes first break, thus protecting the rolls.

3) The coupling is installed at the connection between the shaft and the shaft of the transmission mechanism. When the motor is overloaded, the pins in the coupling are cut off, thereby protecting the motor.

4) Overcurrent relay and thermal relay, located at the power input of the motor. When the input current exceeds the load, it can automatically cut off the power supply to protect the motor.

3. What guide devices are there in the rolling mill?

The guide device is an indispensable and important part in the section steel rolling mill. In order to make the rolling piece enter and exit the pass accurately according to the specified position, direction and required state, avoid the rolling piece from wrapping the roll, the rolling piece is scraped and extruded, and ensure the Workers and equipment are safe, and guide devices are installed before and after the roll. The guide device includes a guide plate, a guide box, a fixed beam, a guide tube, a torsion guide plate, a torsion roller, and a front and back enclosure.

The guide plate is used to guide the rolling piece to enter and exit the pass correctly, so that the rolling piece will not be skewed and twisted in the horizontal direction. The guide plate at the loading entrance is called the entrance guide plate, and the guide plate installed at the exit is called the exit guide plate. Sometimes the guides are loaded into the guide box.

The guard plate is installed on the outlet side to prevent roll wrapping accidents. The lower guard plate is mounted on the guide beam. The upper guard plate is more difficult to fix, and it is not as reliable as the lower guard plate, and its top may leave the roll due to the vibration of the stand, or it may cause an accident due to the rolling stock hitting the guard plate tip. The use of upper pressure in the hole design is an effective measure to avoid this trouble.

The three-roll mill needs to have a lifting table or a steel turning guide plate, as well as various special steel turning machines, steel shifting machines, reverse enclosures, positive enclosures, vertical enclosures and other devices.

The function of the reverse enclosure is to guide the flat oval, diamond, and rectangular rolling stock to the next stand, and turn the 90-degree angle to make the rolling stock stand into the square hole or vertical rolling hole. The rolling stock cannot naturally complete the above-mentioned turning action in the running groove of the hoarding, and must resort to twisting the guide tube.

The function of the front plate is to guide the standing square from one rolling mill to another rolling mill, and make the rolling piece naturally turn over at an angle of 45 degrees and enter the elliptical pass.

The function of the standing wall is to guide the rolling stock of the upper rolling line to the lower rolling line on the same stand, and twist the rolling stock at an angle of 45 degrees. Some rolling mills for the production of welded pipe blanks also use vertical fences, which only play a guiding role and do not function to reverse the rolling stock.

4. How are rolling mills classified?

According to the use, it is divided into two categories: semi-finished rolling mills and finished rolling mills. Semi-finished rolling mills include: various blooming mills, continuous billet rolling mills and small and medium-sized rolling mills. Finished mills include section steel mills, steel plate mills, steel tube mills and special purpose mills. The size of semi-finished rolling mill and section steel rolling mill is usually expressed by the nominal diameter of the roll, that is, the pitch circle diameter of the herringbone gear. The size of the steel plate rolling mill is represented by the length of the roll body, and is divided into thick plate, medium plate and thin plate mills according to the thickness of the rolled steel plate. The steel pipe mill is generally expressed by the outer diameter of the steel pipe being rolled.

According to the arrangement form: there are seven kinds. Single stand rolling mill, tandem rolling mill, tandem rolling mill, semi-continuous rolling mill, continuous rolling mill, cross-country rolling mill, chess rolling mill.

According to the number of rolls: there are five categories. Namely two-roller, three-roller, four-roller, multi-roller, and universal.

5. What does the rolling process system include?

The rolling process system mainly includes deformation system, speed system and temperature system.

1) Transgender system

Under certain rolling conditions, the deformation process from billet to finished product is called deformation system. Its main content is to determine the total deformation and pass deformation. The distribution of deformation is an important parameter in process design, and it is the main basis for rolling equipment selection and roll shape design. The deformation system plays an important role in the output of the rolling mill and the quality of the product.

The reduction rules of the blooming mill, the pass design of the section steel mill, the reduction rules of the steel plate rolling, and the part of the steel pipe rolling mill table all belong to the deformation system.

2) Speed system

The main content of the speed system is to select the rolling speed, that is, to determine the rolling speed of each pass and the speed of different stages in each pass. The higher the rolling speed, the larger the mill output. Therefore, increasing the rolling speed is one of the main ways to improve the productivity of modern rolling mills. However, the improvement of rolling speed is limited by a series of factors such as the structure of the rolling mill and its strength, motor capacity, mechanization and automation level.

The speed regulation of the blooming mill, the determination of the speed of each stand of the continuous rolling mill, and the determination of the speed of the non-speed rolling mill belong to the content of speed rolling.

3) Temperature regime

The temperature regime specifies the temperature range during rolling, that is, the starting rolling temperature and the finishing rolling temperature. Whether the temperature system is reasonable has a direct impact on the output of the rolling mill, equipment safety and product quality.

The above three process systems are interrelated and restrict each other.