Practice questions on steel rolling process
Steel rolling machinery
Steel rolling machinery consists of several bases composed of a steel rolling mill and a series of auxiliary equipment.
2. Steel rolling production system
When organizing production, the primary rolling mill or continuous casting ingot is rolled into various finished products according to the differences in raw material sources, product types and production scales
Rolling mill supporting equipment constitutes various steel rolling production systems.
3. The most fundamental process in hot rolling production
1) Selection and preparation of raw materials - selection and surface cleaning;
2) Heating of raw materials - heating temperature, heating speed, heating time;
3) Rolling system - Deformation temperature range (starting rolling temperature, final rolling temperature), degree of deformation, deformation speed or rolling speed;
4) Post-rolling cooling and finishing of steel;
5) Inspection of steel quality.
4. Overheating
Definition: Excessively high heating temperature and prolonged heating time cause grain growth and weakened intergrain bonding force.
For carbon steel, the maximum heating temperature should be 100 to 150 degrees lower than the solid phase line in the iron-carbon balance diagram. If the heating temperature is too high or the heating time is too long, it will cause
Excessive growth of austenite grains weakens the bonding force between grains, deteriorating the mechanical properties of the steel.
5. Overburning
Definition: On the basis of overheating, if the heating temperature is further raised to an excessively high level, oxidation or melting occurs at the grain boundaries, leading to fragmentation (scrapping) during rolling. Overburning
In essence, it is a further development of overheating. Therefore, preventing overheating can prevent overburning.
6. Cold storage
After being cooled to a certain temperature on the cold bed, they are stacked for cooling.
7. Slow cooling
Slow cooling in a slow cooling pit or isothermal treatment in a holding furnace.
8. Rolls
Roller body, roller neck, shaft head
Roller body: It is the part where the rolled piece is rolled.
Roll neck: Located on both sides of the roll body, it is installed in the bearing and serves as the supporting part of the roll, transmitting the rolling force through the bearing housing and the lowering device
For the rack.
Roller head: Connected to the connecting shaft, it is used to transmit torque to make the roller rotate.
9. What are the functions and requirements of roll bearings?
Function: It is used to support the rolls, bear the rolling force transmitted by the rolls, and keep the rolls in the correct position in the frame at the same time.
It should have a small coefficient of friction, sufficient strength and rigidity, a long service life, and be easy to replace the rollers.
10. The conditions under which dynamic pressure bearings maintain liquid friction are
(1) There is a wedge-shaped gap between the roller diameter and the shaft liner to allow the lubricating oil to be drawn into the wedge gap and establish a definite oil wedge.
(2) The roller diameter should have sufficient rotational speed to form a pressure balanced with the external force in the oil film.
(3) It is necessary to continuously supply sufficient lubricating oil with appropriate viscosity and very clean quality.
(4) The friction surface of the bearing needs to be processed with high precision, with a dimensional accuracy of grade one.
(5) The bearing has good sealing performance.
11. Roll adjustment device
Function
Roll radial adjustment device: Adjust the roll gap and roll out the required cross-sectional dimensions, especially for primary rolling, billet, section steel rolling mills, etc.
Roll radial adjustment device: Adjust the height of the rolling line to be consistent with the height of the roller track; Keep the rolling lines of each frame consistent on the continuous rolling mill.
Axial adjustment of the rolls: Adjust the rolls of the section steel rolling mill axially to align with the hole shape.
Roll axial adjustment: For plate and strip rolling mills, axial movement is used to adjust the roll shape for plate shape control (such as CVC, HC rolling mills, etc.).
12. Why is the upper roller balancing device adopted?
Eliminating impact and clearance: If there is no roller balancing device, clearance will occur between the lower screw and the bearing housing as well as between the lower screw and the nut
In this way, when rolling is carried out, an impact will occur.
13. Types of upper roller balancing devices:
Spring balancing device, heavy hammer balancing device, hydraulic balancing device.
14. The function of the upper roll balancing device
Eliminate the clearance between the bearing housing, the pressing screw and the nut caused by the self-weight of the parts, and eliminate the impact. The action that helps the roll rise when lifting it
Use, adjust the shape of the roller
15. Requirements for the frame in the rolling process
The frame is a permanent part in the rolling mill and there are no spare parts for the frame.
Ensure sufficient strength;
Ensure sufficient rigidity;
Under the premise of meeting the requirements of strength and rigidity, it should have a reasonable structure. Adapt to the needs of roll adjustment and rapid roll changing.
Take a very high safety factor and design it as a permanently usable and non-replaceable part.
16. The function of the rack
It is used to install all the parts in the working base such as the rolls, roll bearings, roll adjustment devices and guide guard devices, and to bear the full rolling force.
17. Types of racks
Rolling mill frames are generally classified into two types according to their structure: closed frames and open frames.
The main structural parameters of the frame are the width and height of the window and the cross-sectional dimensions of the column.
19. Steel rolling mill transmission device:
It is composed of an electric motor, a reducer, a gear seat and a connecting shaft, etc.
20. Universal Rolling mill
A rolling mill with horizontal rolls and vertical rolls has a working base with a pair of horizontal rolls and a pair or two opposite rolls. When rolling slabs, the vertical rolls can roll the side
On the side, this rolling mill has more than the billet opening base of the slab primary rolling mill or the hot continuous rolling strip rolling mill. It is used for wide strip steel, slabs, wide-edge steel beams, H-beams, etc.
21. Vertical rolling mill
A rolling mill with vertically placed rolls, used in situations where steel flipping is not desired.
22. Classified by the layout form of the steel rolling mill
Single seat type, horizontal row type, vertical row type, semi-continuous type, continuous type, series reciprocating type and chess layout type, etc.
23. The transmission mechanism of the steel rolling mill includes:
Gear base, reducer, flywheel, connecting shaft, coupling and other parts.
24. Basic size parameters of the rolls:
The nominal diameter D, body length, diameter d and diameter length l of the roll.
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