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Process of the finishing rolling unit


Table of Contents

Description:This article introduces the causes of a series of problems encountered in the stacking of steel during rolling and the laying ring of the laying machine, for reference

Keyword:Steel rolling process

The process adjustment of finishing rolling unit generally only adjusts the first time and the finished sorties, and other sorties shall not be adjusted at will. There are two reasons:

  1. move the roller joint of one frame, it will destroy the micro-tension relationship of each frame, resulting in the fluctuation of product size;
  2. The opening of the guide roll of the rolling guide is accurately adjusted according to the sample rod. If a roll joint is enlarged, the incoming material will become larger, reduce the service life of the guide roll and even damage the guide wheel and produce the waste; if a small roll joint is collected, the incoming will become smaller, the guide wheel will be unstable, and the steel reversing phenomenon will appear.

For the height of the finished product and the width, the first mill shall be adjusted and then the finished mill; the cumulative adjustment of the first and finished frame mill shall not exceed 0.3mm.

When the surface quality of the billet is found to be bad, stop to check whether there is foreign body in the roller ring and guide.

(1) The finished product has a larger vertical diameter and a slightly smaller horizontal diameter. Reduce the roll gap of the finished product;

(2) When the vertical diameter of the finished product is small and the horizontal diameter is just right. Enlarge the roll gap of finished product sorties;

(3) When the vertical diameter of the finished product is just right and the horizontal diameter is large. Reduce the roll gap of the first sortie;

(4) When the vertical diameter of the finished product is just right and the horizontal diameter is small. Zoom in on the roll gap for the first sortie.

If the requirements are still not met after the above adjustments, the incoming material size of the front unit should be checked, and the roll gap of the last sortie of the front unit should be enlarged or reduced. Generally, the cumulative adjustment of the roll gap between the first stand and the last stand of the finishing mill shall not exceed 0.3mm.

Reasons for stacking steel during rolling:

The main reasons for piled steel at the head during rolling are as follows:

(1) The size of the rolled piece in the previous pass is too large, so that when the rolled piece enters the next pass, it is squeezed into the entrance splint to form a pile of steel;

(2) Due to the uneven deformation of the billet head during rolling, the low temperature of the billet head and inclusions may cause the rolling piece to start;

(3) The torsion guide is severely worn or the bearing of the torsion guide wheel is burnt out and does not rotate, resulting in a change in the torsion angle and causing piled steel;

(4) The elbow of the rolled piece causes the next pass to fail to advance, causing piled steel.

Reasons for stacking steel at the end of rolling are:

(1) Defects caused by the billet itself, such as delamination, severe air bubbles, etc., will be half-broken during the rolling process and cause stacked steel;

(2) When the rotational speed of an intermediate rolling mill is improperly set, the stacked steel rolling state will actually occur, and the first half of the rolled piece will be rolled by the front rolling mill to maintain tension; Cause the rack to generate piles of steel;

(3) Due to the sudden increase or decrease in speed of the motor of a certain rolling mill, the original continuous rolling relationship is destroyed and steel piles are caused;

(4) Due to the sudden breakage of the roll, or the serious damage of the guides in the previous passes, the cross-section of the rolled piece is changed and the pile of steel is caused.

The reasons for stacking steel between the racks of the finishing mill are:

(1) guide and guard bonded steel;

(2) The guide wheel does not rotate or the bearing burns out;

(3) The beginning of the rolled piece;

(4) The guide guard or roller ring is installed incorrectly;

(5) Improper roll gap setting or incoming material size does not meet the requirements;

(6) The guide is not fastened;

(7) The key of the pressure roller is broken to loosen the roller sheet;

(8) Roller pieces;

(9) The bearing bush of the roll shaft is worn or broken;

Reasons for piles of steel in scrap bins

When spinning 5 times, the main reasons are:

1. The entrance guide of 28# is not good, such as the guide is installed sideways, the opening is too large, the guide sticks to iron, the guide roller does not rotate, etc.

2. Misalignment of the rolling line between the 28# export guide and the waste box, and the base of the guide is not correct, etc.

3. The 28# export guide, the waste box is excessively worn or stuck to iron.

When spinning between 5-12 turns, the main reasons are:

1. The water cooling section is installed incorrectly or excessively worn.

2. There are foreign objects in the water cooling section.

3. The cooling water in the water cooling section, the blowback water, the air nozzle is often open, it cannot be closed or it is opened too early.

When spinning about 12 times, the main reasons are:

1. The guide in the middle of the pinch roller is installed off-center.

2. Excessive wear of the bell mouth core tube of the laying machine.

3. The pinch roller is in the normally closed state.

The reason for the pile of steel in the scrap box at the end of the wire rod:

1. The speed matching between the finishing mill, pinch roll and laying head is not correct.

2. The opening degree of the pinch roller is not set correctly.

3. The parameters of the pinch roller are set incorrectly during the full clamping process, such as cylinder pressure, roll diameter, current limit value, etc.

4. The steel quality is not good, such as rotten steel, etc.

Judging the position of the steel head according to the number of spinning circles, generally check the position and reason of the impact of the steel head before this position. The Measures Taken Against the Stacked Steel in Waste Containers

1. During the initial installation, the turning guide groove of the waste box deviated from the rolling line, and then the base of the turning guide groove of the waste box was centered again.

2. After the pins of the overturning guide groove are ground, the upper cover moves up and down. In severe cases, it reaches 0.5-0.6mm, and then replace the original pins with screws.

3. The top cover of the waste box is too light and easy to open, but too heavy to provide protection. Later, the weight of the top cover of the waste box will increase.

4. Renovate the rear guide of the pinch roller, increase its inclination angle, and avoid the steel head hitting the inlet duct of the laying machine.

5. The guide and guard fixture in the middle of the pinch roller is biased, causing the guide and guard in the middle to deviate. Replace the fixture with a new one.

6. Formulate the use standard for the guide groove in the water-cooling section: the maximum wear diameter of the guide groove in the water-cooling section after finishing rolling is not greater than 24mm, the maximum wear diameter of the small-size guide groove is not greater than 19mm, the deviation from the center line does not exceed 2mm, and the swing of the guide pipe does not exceed 2mm.

Delineate maintenance responsibilities: The responsibility for the misalignment of the rolling line at the exit of the 28 rolls to the pinch rolls belongs to the production preparation. It is required that the major rolling line should be checked once a month, and the daily maintenance and parking time of the small ones should be checked immediately. The steel rolling workshop is responsible for checking whether there are steel heads, steel slag and whether the water nozzle is active. The water nozzle activity is undertaken by the preparation; the centering of the guide groove after stacking steel is processed by the rolling steel, and the vibration of the water nozzle pipe is resolved by the production preparation.

Red billet quality and influence

If the size of the rolled piece in the previous pass is too high or too wide, the rolled piece will be squeezed into the entrance guide of this pass and be blocked from stacking steel. The traces of the blocked head of the rolled piece should be observed to make a judgment.

2. Uneven deformation of the head of the rolled piece during large-reduction rolling, low temperature of the head or slag inclusion and other reasons cause splitting and pile up steel.

3. The incoming material in the last pass is too small, resulting in too large gap between the rolled piece and the guide, causing the head to fall steel, so that the rolled piece is blocked in the entrance guide of this pass, resulting in stacked steel.

4. The center line of the import and export guide is not consistent with the center line of the hole shape, the upper and lower rollers are worn unevenly, and the gap between the transmission parts is too large, which causes the elbow to pile up steel.

5. Improper setting of the size of the red billet may cause breakage or chipping of the roller ring.

6. If the size of the incoming material is too large, it will be overfilled in the hole pattern and produce ears, resulting in folding.

7. If the size of the incoming material is too small, the rolling piece will swing back and forth to produce irregular ears, causing irregular folding.

8. The rough and medium rolling unit utilizes the high temperature of the rolled piece to increase the extension of the rolled piece.

9. The pre-finishing rolling unit takes advantage of the good surface quality and small cross-section tolerance of the intermediate rolled piece to meet the requirements of the incoming materials of the finishing rolling unit and ensure the reduction of waste products.

10. Only when the material shape of each frame of the finishing rolling unit meets the requirements can the normal continuous rolling relationship (the expected micro-tension rolling effect) be guaranteed.

11. The temperature of the red billet affects the deformation resistance and thus the motor load.

12. The lower temperature of the rolled piece will increase the bounce of the rolling mill and affect the second flow of metal, resulting in a slight pile of steel.

13. The low temperature at the head of the rolled piece will increase the width of the head and pile up steel.

14. The high temperature of the rolled piece will make it too soft to pile up steel in the finishing mill, and it will also cause serious secondary oxidation, causing the scale to fall off and block the stacking of steel in the guide.

15. The uneven temperature of the rolled piece will cause tension fluctuations and affect the precision of the finished product.

Problems such as the spinning circle of the spinning machine fluttering left and right, different sizes of spinning circles, and out-of-round spinning circles affect production.

1. The reason why the spit circle flutters left and right:

When the coil is ejected and dropped at the outlet of the spinning pipe, there is a speed in the tangential direction of the coil. Technically, the speed advance value of the laying head and pinch roller should be adjusted to make the laying coil fall smoothly and evenly.

2. Different sizes of spinnerets:

Due to the continuous wear of the laying tube wall, the dynamic balance of the laying machine is destroyed, and the spinning process may be blocked due to wear. Therefore, the wear resistance requirements of the laying tube should be improved, and the speed of the laying machine should be reduced; Improper installation of the spinning tube, high temperature spinning, deformation and displacement of the spinning tube will also cause large and small circles, and should be installed strictly;

On the other hand, the wear and tear of related equipment for spinning will also cause large and small circles. You should check the wall thickness of the spinning tube, the outlet bend of the pinch roll, the guide groove between the double-module rolling mill unit and the pinch roll, and the cooling water tank. Control the wear and tear of the cold water pipe and adjust it in time; in addition, improper control of electrical automation and improper adjustment of rolling line tension will also cause large and small circles, and relevant necessary measures should be taken.

3. The spit circle is not round:

The out-of-round spinning circle is due to the fact that after the rolling line is changed, the spinning tube is not replaced or the dynamic balance is damaged after the spinning tube is worn, and the dynamic balance test is not carried out after the new spinning tube is replaced. It should be checked regularly and carried out during installation. Spinning maneuver balance test.

Generally it is 5-10 days if the goods are in stock. or it is 15-20 days if the goods are not in stock, it is according to quantity.

A: Payment<=1000USD, 100% in advance. Payment>=1000USD, 30% T/T in advance ,balance before shippment.

Always a pre-production sample before mass production;
Always final Inspection before shipment;
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The world No. 1 in crude steel production steel plant, over 70% of the HSS for bar and wire are from us.

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Generally, the amount of steel passing in a single groove (times) is 3 to 5 times that of cast iron rolls.

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