Ten Basic Questions about Steel Rolling
The problems existing in hole-free rolling and the solutions are as follows:
The stability issue of rolled pieces. Due to the fact that hole-free rolling is not restricted by the side walls of the hole, it is prone to square deviation or distance deviation. The greater the deformation of the rolled piece, the more unstable the rolled piece becomes, making it difficult to continue rolling. The solution is to install double-row rolling guide guards at the entrance of the rolling mill. Additionally, the first rolling mill roll has a hole type to keep the first pass of the rolled piece stable, thereby ensuring the stability of the entire rolling process.
The problem of the edges and corners of the rolled parts. Usually, the edges and corners of the rolled pieces are repeatedly rolled by flat rolls. The edges and corners are very sharp and prone to folding. The temperature drops rapidly here, and some alloys are prone to cracking. However, the reduction of the bar rolling mill is relatively large, and each pass of the rolled piece forms a certain single analysis drum shape, and the edges and corners of the rolled piece naturally disappear.
2. Why are rolling guide guards divided into oil-gas lubrication and grease lubrication?
Rolling guide guard bearings that operate at speeds above 25m/s and are continuously rolled have extremely high rotational speeds and should be lubricated with a mixture of oil and gas. Fuel consumption: 2×0.230cm ³, with an interval of 1 to 2 times per minute. Gas consumption is 2×50 standard liters per minute.
(2) When rolling at a speed below 25m/s, grease lubrication is adopted. Monthly fuel consumption: between 2×2cm ³ /h and 4×4cm ³ /h.
3. What are the characteristics of the horizontal and vertical alternating rolling mill unit compared with the horizontal rolling mill unit?
The rolling torsional guide guards between the racks are eliminated, reducing the steel biting impact of the rolled pieces, and the entire rolling process is stable.
The rolling pieces between the two racks do not twist during rolling, and the size fluctuation of the billets is small (especially at the head and tail).
3. It can avoid rolling accidents and waste products caused by torsional cracks during torsional rolling, and is more suitable for the production of alloy steel.
The rolled pieces do not twist, and the overall performance of the finished products fluctuates little.
4. What are the advantages of cantilever rolling mills?
(1) Easy to operate. There are no archways, bearing housings or various adjusting screws, which is convenient for adjustment. The rack spacing is short, and the hole type and guide guard are easy to align, greatly simplifying and facilitating the operation.
2) Component simplification. The cantilever rolling mill has no transmission connection shaft and its components are also very simplified, reducing by 1/23 compared with traditional rolling mills. Roll changing is fast. Roller changing is both easy and fast, reducing the roller changing time by three quarters.
(4) Reduced the amount of maintenance
(5) Low investment and high operation rate. Compared with traditional rolling mills, the initial investment saves 20% of building costs, 300k of foundation costs, shortens the installation and commissioning time by 25%, and reduces equipment investment by 10%. During the rolling production process, the stop-rolling time for changing the rolling groove is reduced by three quarters, the intermittent time for changing the rolling program is decreased by 15%, and the operation rate of the rolling mill unit is increased by 5% to 7%.
5. What are the requirements for the maintenance and care of cantilever rolling mills?
Transmission system: Regularly inspect the motor's usage condition, load status, lubrication of the tooth contact, and the wear condition of the tooth surface.
Reducer and housing: Regularly open the viewing holes to check the wear of gears and the lubrication condition of bearings.
Lubrication system: Keep unobstructed, with normal pressure and flow.
Regularly inspect and replace the lip seal, eccentric flange and dynamic and static labyrinth.
What are the structural features of the high-precision prestressed rolling mill?
The structure of the rolling mill is a semi-rack structure: The high-precision prestressed rolling mill has the following characteristics:
The rolling mill has high rigidity and the precision of the rolled products is high. The columns of the prestressed rolling mill archway are shorter than those of the old-fashioned rolling mill, and the stress line of the rolling mill is reduced by 75%. Therefore, the prestressed rolling mill has greater rigidity, which improves the accuracy of the rolled pieces and ensures the stability of the dimensional deviation at the head and tail of the rolled pieces. The precision deviation of the head and tail can be controlled within ± 0.06mm, creating favorable conditions for the negative deviation rolling of section steel.
(2) The rolling mill has a compact structure and the equipment is lightweight. The equipment structure of the prestressed rolling mill is compact. Under the same allowable rolling force, its equipment is light in weight and requires less investment.
(3) The rolling mill is easy to disassemble and convenient for installation and maintenance. The roll changing operations for each body pressure unloading and pressure tightening of the prestressed rolling mill are very convenient and can be completed within 10 to 15 minutes, improving the operation rate of the rolling mill.
(4) The rolling mill adopts a welded structure, which is easy to process and manufacture, and its price is 60% of that of cast steel parts.
7. What are the characteristics of closed-end rolling mills?
The closed multi-hole slot two-high rolling mill is the most common form of small-scale rolling mills. In recent years, when designing this kind of rolling mill, it is often necessary to
The lowering device is located between the upper crossbeam and the upper bearing housing of the rolling mill archway, which not only maintains the integrity of the archway but also increases the rigidity of the rolling mill. Moreover, the upper roller hydraulic balance and manual worm - worm gear structure are adopted for the axial adjustment technology of the upper roller, as well as the hydraulic trolley roller changing and the lateral movement technology of the rolling mill, to keep the rolling line fixed. Its multi-hole groove rolls can reduce the frequency of roll changing, thereby reducing the loss of roll changing time. The closed two-high rolling mill is a reliable rough and medium rolling mill unit, and most conventional finishing mill units also adopt this type of machine.
In recent years, single-hole slot closed rolling mills have emerged internationally. That is, the rolls adopt short roll bodies and are assembled on the roll shaft with roll rings. Only one roll slot is engraved on the roll ring, and the material of the roll ring is high-strength wear-resistant ductile iron cast by centrifugal casting. Compared with the common closed two-high rolling mill, the equipment weight of this kind of rolling mill is lighter, almost half as much. Due to the adoption of single-hole grooves, the rolling line is constant and there is no need for a hole type centering device. The roll body is short and double-supported. The rolling mill has high rigidity and can withstand high rolling forces. The equipment takes up little space and is easy to operate. If it is a vertical roll mill, its structure is simple and lightweight.
8. What is a short stress line rolling mill and what are its characteristics
The stress loop line, which is the distribution of the internal forces caused by the rolling force along each load-bearing part of the frame during the steel rolling process of the rolling mill, is simply called the stress line. In order to enhance the rigidity of the rolling mill, a rolling mill that has adopted various technical measures to shorten the stress line is called a short stress line rolling mill.
The short stress line rolling mill has the advantages of small volume, light weight, high rigidity of the rolling mill and long service life of the bearings. In recent years, it has been increasingly widely used on the small rolling mills of this rolling mill. With the emergence of the online rapid roll changing device for short stress line rolling mills, the overall replacement of the stand has been avoided, which reduces the investment in the rolling mill and leads to its more widespread application. Short stress line rolling mills are suitable for use as medium and finish rolling mills. When used as roughing rolling mills, if the cross-section of the rolled piece is large, the thrust or tension of the rolled piece is prone to damage the connection between the stand and the base.
9. What are the main features of compact rolling mills?
Compact rolling mills belong to large reduction rolling mills, and their main characteristics are as follows:
(1) The spacing between the rolling mills is small. The workpiece is pushed into the following rolling mill by the previous one to achieve forced biting, thereby conducting large drop rolling.
(2) The unit is usually composed of 4, 5 or 6 rolling mills and adopts an alternating layout of horizontal and horizontal.
(3) The roll body is short, with only one hole type opened on each roll body (or for single-pass flat roll rolling).
(4) Due to the adoption of large pressure reduction, under the same conditions, compared with the ordinary two-high rolling mill, 1 to 2 rolling mills can be reduced.
(5) The frame is of short stress line structure or cantilever roller structure;
(6) Due to the use of large pressure reduction, if not adjusted properly, steel stacking accidents between racks are prone to occur. Moreover, the small spacing between racks makes operation adjustment and accident handling inconvenient.
(7) Each stand of the compact rolling mill is driven independently, featuring high transmission control accuracy and hard characteristics. The rolling process involves no twisting and no live loops. The units are generally controlled by microcomputers or PLCS, featuring a high degree of automation.
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