Medium and thick plate basic knowledge questions
1. How are steel plates classified by thickness?
Steel strip is divided into five categories according to thickness: extra thick plate, thick plate, medium plate, thin plate and extremely thin strip. In China, the steel plate with a thickness greater than 60mm is called an extra-thick plate, the steel plate with a thickness of 20 ~ 60mm is called a thick plate, the steel plate with a thickness of 4.5 ~ 20mm is called a medium plate, the steel plate with a thickness of 0.2 ~ 4mm is called a sheet, and the steel plate with a thickness of less than 0.2mm is called a very thin strip or foil. Traditionally, the extra-thick plate, thick plate and medium plate are collectively referred to as medium thick plate. Most foreign countries call the steel plate with a thickness of more than 3mm a medium-thick plate.
2. What are the forms of plate mill?
The form of plate mill, from the frame structure, there are 2 roll reversible, 3 roll Lauter, 4 roll reversible, universal and compound.
3. What is a 3-high Lauter mill?
The 3-roll Lauter mill is developed from the 2-roll reversing mill, generally the diameter of the upper and lower rollers is 700 ~ 800mm, the diameter of the middle rollers is 500 ~ 550mm, and the length of the roll body is 1800 ~ 2300mm.
The main advantages of the 3-high Lauter mill compared with the 2-high reversing mill are: it can be driven by the AC motor with lower cost to realize round-trip rolling, and the motor capacity is reduced by the flywheel, so the equipment is simple and the investment is less. The deflection of the middle roll supported by the upper and lower rolls is small, and the middle roll is easy to change, so that the roll profile is better, and the accuracy of the steel plate thickness is improved. Due to the use of small rolls, the rolling pressure and energy consumption can be significantly reduced, and the steel plate can be extended more easily.
The disadvantages of this mill are that it cannot change speed, the diameter of the middle roll is small and it is a passive roll, so the biting ability is reduced. The lifting platform is installed before and after the mill, which limits the weight of raw materials. The rigidity of the roller system is not large enough. Therefore, this mill is not suitable for rolling thicker and wider products, and is commonly used to produce 4 ~ 20mm medium plates. Due to the rise of the 4-high mill, this kind of mill is no longer built, and some old plants are gradually replaced with 4-high mills.
4. What is a 4-high reversing mill?
4 high reversing mill is the most widely used medium and heavy plate mill in modern times. It combines the advantages of 2-high reversing rolling mill and 3-high Lauter rolling mill, and its support rolls and work rolls are completely divided, which not only reduces rolling force, but also greatly increases the rigidity of the rolling mill. Therefore, it is suitable for rolling medium and thick plates of various sizes and specifications, especially the medium and thick plates with large width, precision and strict plate shape requirements. However, the cost of this mill is high, so it is often used as a finishing mill to save investment.
5. How to adjust the reversing mill?
First of all, adjust the lower support roller level with gasket, and then press the work roller roller surface is 15 ~ 20mm higher than the frame roller to add or remove the gasket under the support roller bearing box. The parallelism of the upper and lower work rollers can be placed at both ends of the roll end l00mm from the sound of 5 ~ 8mm low carbon steel wire, slowly press down the upper roll, so that the upper and lower work roller roll gap is adjusted to 3 ~ 5mm after lifting the upper roll, measuring whether the steel wire thickness is equal, the general requirement is not less than 0.5mm, and then zero adjustment, generally press the upper and lower rollers against each other. Until the pointer on the dial does not move, it is adjusted as the initial zero position after taking into account the roller jump value. When rolling, it can be repaired for 2 to 3 times.
6. What is a universal mill?
A steel mill with both horizontal and vertical rolls is called a universal mill. Vertical rollers are arranged on the exit side of the mill or both sides of the import and export, and the type of universal rolling mill is generally 2-roll reversible, 4-roll reversible, etc. The purpose of the roller is to roll the side of the steel plate, roll the edge of the steel plate without cutting the edge, in order to reduce the metal consumption and improve the yield.
7. What are the layout of the plate mill?
Because the rolling mill with the same performance parameters adopts different layout forms, the product output and rolling process of the rolling workshop are different, so according to the production characteristics of medium and thick plate, the layout form of medium and thick plate mill can be divided into: single rack type, double rack type, semi-continuous type and continuous type.
8. What is double rack arrangement?
The double-stand arrangement is to divide the roughing and finishing stages into two stands to complete, the two stands are roughing mill and finishing mill, the raw materials are billet on the roughing mill, and then rolled into finished products on the finishing mill.
In the current production of medium and thick plates, the double rack arrangement is the main form. The roughing mill in the two-stand arrangement can be used in the 2-high reversible, 3-high Lauter or 4-high reversible, while the finishing mill is generally used in the 4-high reversible.
The advantages of double-stand arrangement are: high output, good surface quality, dimensional accuracy and shape of the product, fewer roll changes and high operation rate.
9. What is semicontinuous plate mill?
The so-called semi-continuous mill refers to the roughing mill whose stands are mainly or all reversible rolling, while the finishing mill group is continuous.
The roughing mill of semi-continuous rolling mill is composed of vertical or horizontal scaler, reversible roughing mill stand and one or two ordinary roughing mill stands. The finishing mill group is composed of a descaling device and 4 to 6 4-roll stands. Most of these mills are equipped with coilers, which can coil strips up to 20ram thickness.
The advantages of semi-continuous rolling mill are: it can produce medium and thick plate and thin plate, and the product specifications are wide, which is especially necessary for the development of areas where the amount of steel plate is not large but the variety requirements are complete.
10. What is the function of the vertical roller mill?
Its function is to control and correct the plane shape, which is easy to produce uneven width in the forming and widening stage. The vertical roll edging is carried out in the length direction and the width direction after forming, and the length direction is to correct the head and tail plate shape, and the width direction is to correct the edge plate shape to prevent the irregular tongue and fishtail deformation of the head and tail, as well as the width change in the length direction and the edge folding. Make sure the board width is the target value.
11. Vertical rolling mill according to rolling force, use, transmission mode, frame structure, layout position divided into what kinds of forms?
(1) According to rolling force is divided into heavy, medium and light;
(2) According to the use of edge rolling, edge and scale breaking;
(3) According to the transmission mode is divided into upper transmission and lower transmission;
(4) According to the frame structure is divided into closed type and open type;
(5) According to the layout position, there are points before and after the host, close and non-close.
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