1. Roll installation and rolling adjustment
Roll installation and rolling adjustment is a core work to complete and establish a stable rolling process. The purpose of rolling mill adjustment is to ensure that the rolling mill runs in a good state, to ensure that the rolling process is carried out in accordance with the feasible process system, so as to ensure the rationality of the production process, ensure product quality, reduce steel stacking accidents, and improve rolling mill operation rate.
In order to achieve the above purpose, the rolling mill adjuster should first reconfirm the rolls, guides and stands provided in the roll maintenance section, implement online replacement and installation of the above components, and complete the online pre-adjustment of the rolling mill. During the rolling process, the adjustment workers make timely judgments on the causes of production accidents in production according to the quality situation, formulate reasonable adjustment plans and implement them. The adjustment should ensure the geometric shape and geometric dimensional accuracy of the rolling piece, ensure the micro-tension control of the rolling mill and the tension-free control of the looper, and ensure the normal continuous rolling process.
The completion of the rolling process is divided into three steps: first, the online replacement and installation of the rolling mill or the replacement and installation of the rolls must be completed; then the rolling mill is pre-adjusted for re-line; finally, the rolling mill starts normal rolling and performs online rolling mill adjustment.
2. Online replacement and installation of rolling mill
Before changing the rolls, it is necessary to recheck whether the upper-line rolls are the rolls of the order, rolling type, and specification; scrub the slideways, the flat heads of the rolls, and the inner hole of the sleeve, and apply clean grease after scrubbing. After the preparation work is completed, the rack can be replaced according to the roll replacement plan. The working steps are:
Turn off the mill cooling water and remove the inlet and outlet guides. Disconnect the water pipe joints of the upper and lower rolls. Activate the hydraulic locking device to open the stand. Select “Stand traverse” for the horizontal stand to move the stand forward and move the rolling mill to the limit position on the operating side. (Choose the “Rack Up/Down” button for the vertical rolling mill to lower the stand and lower the rolling mill to the lower limit position.) Pull out the fixing pin of the bracket wrench of the flat head cover, and turn the bracket wrench to make the flat head of the stand and the flat head The headgear bracket is separated. Pull the “stand traverse” button of the horizontal rolling mill to make the flat head cover back, the flat head cover is disengaged from the flat head of the roll, and the flat head cover bracket is moved to the limit position on the transmission side (pull the vertical rolling mill button to make the flat head cover The bracket rises, the flat head cover is disengaged from the flat head of the roll, the flat head cover bracket is raised to the limit position on the transmission side, and then the “stand traverse” button is pulled to traverse the vertical rolling mill to the outer limit position). Use the crane to lift the stand from the rolling line as a whole. Put the new roll stand on the sliding roll as a whole, and use the skid bar to rotate the roll so that the flat head of the roll is in the same position as the flat head cover of the rotating shaft. After confirming that the rolling mill stand and the rolling line are centered, pull the horizontal rolling mill “stand traverse” button to move the flat head bracket to the operation side (pull the vertical rolling mill “stand traverse” button to make the stand move back , move the vertical rolling mill to the inner limit position. Then pull the vertical rolling mill “stand up/down” button to lower the flat head cover bracket). Make the roll flat head enter the drive shaft flat head cover until it reaches the limit position. Activate the locking device to lock the rack and connect the water pipe joints. Install the guide. , and fine-tune the roll gap and guide of the rolling mill.
3. How to replace the rolling groove
Each pair of rolls is engraved with multiple grooves. After the tonnage is specified in the production process specification of the grooves (or the grooves are damaged), the new grooves should be replaced. Its operation method is as follows:
- Loosen the guide guard at the exit and entrance, traverse to the new rolling groove, and install and tighten after alignment;
- Set the roll gap value of the new pass with reference to the height of the original pass and the specified value in the process specification;
- Adjust the position of the cooling water pipe so that the cooling water can be poured on the new rolling groove accurately;
- Move the rolling mill to make the new groove out of the rolling line;
- The new rolling groove should be derusted with a portable grinder, and the surface should be roughened to prevent the rolling stock from slipping.
4. Trial rolling after groove change
Under normal circumstances, due to the large section and low rolling speed of the rough rolling stock, there are few steel stacking accidents. Generally, small steel is not trial-rolled, but directly rolled. During intermediate rolling or finishing rolling, in order to prevent the steel pile from slipping or the speed mismatch caused by irregular adjustment, small steel should be trial rolled.
The common problems of new grooves are the difficulty of biting the steel and the slipping of the rolled piece after biting. In order to smoothly bite the first steel, the following measures can be taken:
- Grind the groove with a grinding wheel to remove oil and roughen the surface to increase friction;
- Properly raise the hole height of the new slot, generally 0.5~1mm;
- Reduce the tandem speed of the front (upstream) mill of the new groove mill by 3~5%;
- Turn off the cooling water of the rolling groove to reduce the temperature drop of the rolling head;
Trial rolling of small steel is generally carried out after finishing or intermediate rolling mill slot change. The purpose is to confirm whether the given roll gap is reasonable and whether the size of the rolling piece meets the requirements; the second is whether there is a problem with the installation and adjustment of the guide guard; the third is to increase the roughness of the rolling groove and confirm whether there is a problem with the bite of the rolling groove on the rolling piece. .
The size of the sample can be sampled by the flying shear in front of the unit or a certain sample can be left after the accident is piled up. The specification requirements are the same as the size requirements of the rolling stock in front of the unit. The sample is placed in the heating furnace and heated to the rolling temperature before the groove is changed. The rolling mill is fed manually one by one at the “crawling” speed, and the height of the sample is measured with a vernier caliper.
5. On-line adjustment of rolling mill
The main contents of online adjustment of rolling mill include: axial adjustment of roll, radial adjustment of roll, roll gap adjustment, installation and adjustment of guide, measurement and adjustment of rolling piece, inspection and adjustment of finished product.
1) Axial adjustment of the roll
Due to the large pass turning error, poor roll installation can lead to axial misalignment of the pass (commonly known as misaligned rolls). Misaligned rolls can cause bending, twisting, irregular rolling, or ears, causing groove wear. Uneven and unstable rolling will cause accidents such as stacking of steel between stands and finished products in severe cases. Therefore, the adjuster must check and confirm before the stand is installed or the roll is adjusted. If the wrong roll is found, it must be adjusted.
2) Adjustment of roll gap
The adjustment of the roll gap is one of the important parameters of the rolling process, and its setting and adjustment are an important part of the operation of the rolling mill. In particular, the adjustment after a new roll change or groove change is particularly important.
Adjustment of the roll gap of the roughing mill and the intermediate rolling mill: the roll gap of the rough and intermediate rolling mills is relatively large, and the error of the pass turning is large. Generally, the adjuster should adjust the roll gap value according to the depth of the groove bottom of the pass. Can be measured with internal calipers. When adjusting, consider the bounce value of the roll gap. The rough rolling is generally about 1mm, and the intermediate rolling is about 0.5mm. The measured groove bottom depth plus the roll gap bounce is the actual red billet size of the rolled piece.
In the production, the measurement of the size of the rough and medium rolling stock can be measured by the outer caliper during the movement of the rolling stock. At this time, the measured value has a certain error, and the adjuster should measure it several times.
The size of the rolled piece of the rough and middle rolling stands is also a key value. The size measurement of this rolling piece can be measured by taking the cutting head or cutting tail of the 1# and 2# flying shears.
3) Adjustment of finishing roll gap:
There are two ways to adjust the finishing roll gap, that is, the feeler plug roll gap and the small round steel indentation method.
The feeler gauge adjustment method is relatively simple, but the roll gap value measured at this time also needs to consider the bounce of the rolling mill.
The small round bar indentation method is to select a softer round bar about 3mm larger than the set roll gap value, idle the rolling mill at the “jog” speed, hold the round bar, roll the round bar from the roll gap, and then measure The thickness of the indentation is compared with the set value of the roll gap, and the adjustment is repeated until the thickness of the indentation is equal to the set value of the roll gap.
It is difficult to measure the size of the finished rolling stock in production, and the wood printing method is generally used.
Wood-burning is a simple and effective means of dynamic inspection of rolling stock. The method is to use a piece of wood to face and stick it directly on the moving rolling piece, and then take it out to observe the shape of the burnt wood imprint, so as to judge the fullness, guide and hole shape of the rolling piece.
4) Alignment of the rolling line
In production, the rolling lines of each stand are required to be on the same straight line, and the offset of the rolling line of the stands may cause uneven wear of the pass pattern and damage to the guide, and in the severe case, it may directly cause a steel stacking accident.
The meaning of the alignment of the rolling line includes not only the alignment of the inlet and outlet guides of the same stand and the pass pattern, but also the consistency of the entire unit on the rolling line.
In the process of stand installation, the positioning of the rolling line of each stand is usually to select two coordinate points at both ends of the entire rolling line, and determine the coordinates of each rolling mill by hanging the wire. Make the center line of the steel wire coincide with the center of the rolling line of the stand, and install a fixed stand.
Roll line marking method. Generally, the center coordinate mark of the rolling line is made at the base of the rolling mill or the position of the arch. During rack traverse or installation, it is the centerline of the guide that coincides with the mark.
Use the light source to observe the alignment. Generally, a light source is set at the entrance guide of the rolling mill of the previous stand, and the guide is observed at the exit of the next stand, so as to determine the rolling center line of the intermediate stand.
Data adjustment method: Calculate the size between the rolling mill and the end of the base of the rolling mill through the relevant dimensions of the rolling mill, and then combine the size of the rolling line to calculate the dimensional relationship between the center line of each pass on a pair of rolls and the rolling line , to measure and adjust the rolling line.
5) Adjustment during rolling
The main adjustment process in the rolling process is to judge whether the guide guard, the use of the rolling groove, the speed adjustment and other technological systems are reasonable by checking the operation and size of the rolling stock, so as to ensure that no steel stacking accident occurs, and at the same time, qualified products are rolled. The basis for adjustment is obtained through methods such as “observation”, “sampling”, “wood printing”, and “strike”.
Observe whether there is a “head up” at the outlet during the bite of the rolling piece between the stands. If so, the installation of the imported rolling guide is too low; on the contrary, if the head of the rolling piece is “pulled down”, it can be judged that the imported rolling guide is installed. too high. Observing the round rolled piece, if there is torsion, it means that the gap between the imported rolling guide and the guide wheel or the height dimension of the rolled piece is too small.
By sampling the flying shear head (tail) or the broken rolled piece, it is possible to judge the wear of the rolling groove, the use of the guide and the alignment of the roll gap and whether the roll gap meets the size requirements of the rolled piece. The judgment can be divided into the following situations:
- The width and size of the roll gap marks on both sides of the rolled piece are different, indicating that the imported guide is installed incorrectly;
- The height size of the rolled piece is appropriate, but the width size fluctuation is small, indicating that the size of the incoming section is insufficient or the tension is too large;
Ears, for many reasons. One is that the incoming material is too large, which causes the pass to be overfilled when entering the next rolling mill. In this case, the section of the rolled piece is relatively full, and there are ears on both sides of the rolled piece; Large, the rolled piece is also bilateral ears, and the height and size are too small; the third is that the entrance guide is relatively biased, which means that the rolled piece has ears on one side and the size of the other side is relatively lacking; the fourth is that the entrance guide is too large or damaged, In this case, the section of the rolled piece after rolling is irregular, with ears on both sides, and the guide should be replaced in time.
Folding is generally caused by the appearance of ears or scratches on a previous rack and then rolling. The reason should be found in time.
Asymmetry up and down (inappropriate ovality), caused by wrong rollers or too large imported guides.
There are periodic pockmarks, pits and indentations on the rolled piece, which are caused by “falling meat” and cracks in the rolling groove.
Wood-burning is a simple and effective means of dynamic inspection of rolling stock. The method is to stick a piece of wood directly on the roll gap of the moving red steel, and then take it out to observe the imprinted image of the burnt wood, so as to judge the fullness of the rolling piece, the use of the guide and the roll, etc.
The adjustment of the finished product size should be carried out according to a certain method on the basis of the above judgment method. Here are a few simple judgment adjustments:
- Sampling and measuring the size of the finished product or using the method of burning wood samples to observe that the width of the rolling piece changes in the head, middle and tail dimensions of the entire rolling piece as large, medium and small. It should be judged that there is excessive steel rolling between the stands. The main console should be notified in time to adjust as soon as possible;
- The size of the rolling strip does not change much, the height size is appropriate, and the width is slightly out of tolerance. The front hole of the finished product and the steel material of the front front hole of the finished product should be adjusted. If the width is too large, the size of the rolling stock of the entire unit should be adjusted;
In the process of controlling the size of each pass, it should be enlarged or reduced at the same time on the basis of ensuring that the size of the rolled piece is basically close to the standard, so that the deformation of each pass is evenly distributed. small phenomenon. The size determination of the intermediate pass rolling can be calibrated by trial rolling small steel in the shift shift. With the wear of the rolling groove, the roll gap adjustment in the shift can be carried out by the method of roll gap compensation, which avoids the uneven deformation of each pass, so that the operator at the main console can easily grasp and adjust the rolling speed. , so that the upper and lower can be combined in a consistent manner.
By comparing the actual rolling load and elongation coefficient of the main console with the theoretical value, it is judged whether the deformation amount of each pass is reasonable.
If the ovality of the finished product size is not suitable, it should be checked whether the opening of the finished roll hole groove or the inlet guide is too large.
6) Judgment and adjustment of tension between frames
The effect of inter-stand tension on rolling stock size is a very complex plastic mechanics process. For example, steel drawing is generated in No. 1 and No. 2 passes, that is, tension is generated between No. 2 and No. 1 rolling mills. This tension reduces the resistance along the rolling direction, thereby increasing the flow of metal along the rolling direction. The flow in the width direction is reduced, making the width dimension of the rolling stock smaller. On the contrary, the stacking process can make the width dimension of the rolled piece larger.
It can be seen from the above analysis that when the tail of the rolling stock leaves the previous stand, the width becomes larger again, which means that there is tension between the previous stand and the stand, because once the tension disappears, the width of the rolling piece of the stand becomes larger. big. The greater the change in width, the greater the tension. In this way, the adjuster can determine whether there is tension between the stands by measuring or judging the change in the width dimension of the head and tail of the rolling piece and the width dimension of the intermediate rolling piece. The change in the width of the intermediate rolling stock can be judged by the width of the unrolled part on both sides of the rolling stock (roll gap). There are two specific methods on site: one is to observe with the naked eye, and the other is to judge by burning wood printing, the latter is suitable for smaller-sized rolled pieces.
The magnitude of the tension between the racks can be directly judged by the main console through the change of the motor load current. When the rolling piece bites into the first steel, the current value is a. If the current value remains unchanged after the rolling piece bites into the second frame, there is no tension. When the current value changes, if it is less than (or greater than) the a value , it indicates that there is drawn steel (or piled steel) in one or two frames.
After the height of the rolling stock in each stand of the rolling mill is confirmed, the tension can be eliminated one by one by the speed regulation of the rolling mill. The tension adjustment should start from the first frame and adjust backward one by one. If the adjustment is started from the last frame, it is possible to adjust the rear, and when the first few frames are adjusted, the tension relationship at the rear will be destroyed again, causing an accident.
The speed of the previous stand can be increased, but the speed-up should be small and progressive. Observe whether the rolling stock of the stand increases in the width direction while increasing the speed. When increasing the speed, pay attention to observe whether there is a small amount of vertical loops in the rolling stock between the two stands. The speed has been increased until the width of the rolling stock of the stand meets the requirements. If the size change of a rolled piece in the width direction is irregular, it may be caused by the uneven local steel temperature; if there is periodicity, it may be that in the previous several passes, one of the stand rolls rotates eccentrically, or the pass A piece falls off from the top, commonly known as “dropping meat”, which causes periodic inconsistencies in the size of incoming materials. The above situations should be dealt with according to the specific reasons.
Generally speaking, the main method of adjusting the tension is to adjust the speed of the rolling mill, but before this process is realized, it must be ensured that the height and size of the rolling pieces of each stand meet the process requirements, and the speed and the roll gap must not be adjusted at the same time. Adjustment at the same time is bound to cause adjustment confusion.