Rolling mill online adjustment, rolling mill technology

1 Axial adjustment of roll

Due to the large pass turning error, improper roll installation can cause the axial misalignment of the pass (commonly known as the wrong roll). The wrong roll can cause bending, twisting, irregular rolling, or ears, causing groove wear Uneven rolling and unstable rolling may cause accidents such as piled steel and finished products between racks in serious cases. Therefore, the adjuster must check and confirm before rack installation or roll adjustment. If a 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. Especially the adjustment after a new roll or groove change is particularly important.

The adjustment of the roll gap of the rough rolling mill and the intermediate rolling mill: the rough and intermediate rolling mills have relatively large roll gaps and large errors during pass turning. Generally, the adjuster should adjust the roll gap value according to the depth of the groove bottom of the pass. It 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 middle rolling is about 0.5mm. The measured groove bottom depth plus the roll gap bounce is the actual red billet size of the rolled product.

In the production of rough and middle-rolled pieces, the size of the rolled piece can be measured with an external caliper in the movement of the rolled piece. At this time, the measured value has a certain error, and the adjuster should measure multiple times.

The size of the rolling piece of the final stand of the rough and medium rolling is also a key value. The size of the rolling piece can be measured with the head or tail of the 1# and 2# flying shears.

 

3 Adjustment of Finishing Roll Gap

There are two methods for adjusting the roll gap of the finishing roll, namely, using a feeler gauge to plug the 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 must also consider the bounce of the rolling mill.

The small round steel indentation method is to select a soft round steel about 3mm larger than the set roll gap value, rotate the rolling mill at a “jogging” speed, hold the round steel bar, roll the round steel through 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.

In production, it is difficult to measure the dimensions of finished rolling pieces, and wood printing is generally used.

Wood-burning is a simple and effective method for dynamic inspection of rolled parts. The method is to use a wooden strip directly facing and sticking to the moving rolling piece, and then take it out to observe the shape of the imprint of the burnt wood, so as to judge the fullness of the rolling piece, the guide and the pass shape.

 

4 Centering of the rolling line

During production, the rolling lines of each stand are required to be on the same straight line. The deviation of the rolling line of the stand may cause uneven wear of the pass and damage the guide guard, and the heavy one may directly cause steel pile accidents.

The meaning of the alignment of the rolling line includes not only the alignment of the inlet and outlet guides and the rolling pass of the same stand, but also the consistency of the entire mill on the rolling line.

In the process of rack installation, the positioning of the rolling line of each rack 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. After the roll is changed, the rolling line can be centered by the following three methods:

The rolling line is used as a marking method. Generally, the center coordinates of the rolling line are marked on the base of the rolling mill or the archway. During the horizontal movement or installation of the rack, the center line of the guide and guard coincides with the mark.

Use the light source to observe the alignment. Generally, a light source is installed at the entrance guide of the previous stand rolling mill, and the next stand is guided and observed at the exit of the next stand to determine the rolling centerline of the middle stand.

Data adjustment method: Calculate the size between the rolling mill and the end of the rolling mill base through the relevant size of the rolling mill, and then calculate the size relationship between the center line of each pass on a pair of rolls and the rolling line in combination with the size of the rolling line , To measure and adjust the rolling line.

 

5 Adjustment during the rolling process

The main adjustment process in the rolling process is to check the operation and size of the rolled piece to determine whether the guide, the use of the rolling groove, and the speed adjustment are reasonable, so as to ensure that no pile-up accidents occur, 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 exit of the rolling piece during the biting process between the racks. If there is, the imported rolling guide is installed too low; on the contrary, if the head of the rolling piece has a “down” phenomenon, it can be judged that the imported rolling guide is installed Too high. Observe the round rod rolling piece, if there is a torsion phenomenon, it means that the imported rolling guide wheel gap or the height of the rolling piece is too small.

By sampling the flying shear head (tail) or broken pieces, it is possible to judge the wear of the rolling groove, the centering of the guide and the use of the guide and whether the roll gap meets the size requirements of the rolling piece. The judgment can be divided into the following situations:

The width dimension of the roll seam print on both sides of the rolling piece is different, indicating that the imported guide and guard are not installed properly;

The height dimension of the rolled piece is appropriate, but the width dimension fluctuation is small, indicating that the section size of the incoming material is insufficient or the tension is too large;

There are many reasons for ears. 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 rolling piece is relatively full, and there are ears on both sides of the rolling piece; Large, the rolling piece is also bilateral ears, and the height is too small; the third is that the entrance guide is relatively biased, which is manifested as the rolling piece has ears on one side and the other 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 guard should be replaced in time.

Folding is generally caused by ears or scratches on a previous rack and then rolling. The cause should be found in time.

Up and down asymmetry (inappropriate ellipticity), caused by the wrong roller or the imported guide is too large.

There are periodic pockmarks, pits, and indentations on the rolling piece, which are caused by “flesh falling” and cracks in the rolling groove.

Wood-burning is a simple and effective method for dynamic inspection of rolled parts. The method is to directly stick a wooden strip to 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 rolled piece, the guide and the use of the roll, etc.

The size adjustment of the finished product should be carried out in a certain way on the basis of the above judgment method. Here are a few simple judgment adjustment methods:

Through the finished product size sampling measurement or using the method of burning wood samples to observe the width of the rolling piece at the head, middle, and tail dimensions of the entire rolling piece, the change in the head, middle and tail dimensions of the entire rolling piece is large, medium, or small. It should be judged that there is excessive drawing and rolling between the stands. Notify the main console in time to adjust as soon as possible;

The size of the rolling rod has little change, the height is suitable, 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 piece of the whole unit should be adjusted;

In the process of the size control of each pass, the size of the rolled piece should be enlarged or reduced at the same time on the basis of ensuring that it is basically close to the standard size of the rolled piece, so that the deformation of each pass is evenly distributed. Small phenomenon. The size of the rolling piece in the middle pass can be calibrated by trial rolling small steel during the 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 between each pass, so that the main console operator can easily control and adjust the rolling speed. , So that the upper and lower can be combined in unison.

The actual rolling load and elongation coefficient of the main console are compared with theoretical values to judge whether the deformation of each pass is reasonable.

The ellipticity of the finished product size is not appropriate. Check whether the finished roll hole groove or the opening of the imported guide guard is too large.

 

6 Judgment and adjustment of tension between racks

The influence of the tension between the stands on the size of the rolled piece is a very complicated plastic mechanics process. For example, drawing steel occurs in the No. 1 and No. 2 pass, that is, tension is generated between the No. 2 and No. 1 rolling mills. This tension reduces the resistance in the rolling direction, thereby increasing the flow of the metal in the rolling direction. The flow in the width direction is reduced, so that the width of the rolled product becomes smaller. On the contrary, the stacking process can make the dimension of the rolling piece in the width direction larger.

From the above analysis, it can be seen that the width of the rolling piece becomes larger when it leaves the previous stand, indicating 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 changes Big. The greater the width change, 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 middle rolling piece. The change of the width dimension of the middle rolled piece can be judged by the width of the unrolled part on both sides of the rolled piece (at the roll gap). There are two specific methods used at the scene: one is to observe with the naked eye, and the other is to judge by burning wood prints. The latter is suitable for rolling pieces of smaller size.

The size 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, such as less than (or greater than) a value , It indicates that there is drawn steel (or piled steel) in the first and second frames.

After the rolling mill has confirmed the height of the rolled pieces in each stand, the speed of the rolling mill can be used to eliminate the tension one by one. To adjust the tension, start from the first frame and adjust backward one frame at a time. If you start to adjust from the last frame, it is possible to adjust the back. When you adjust the first few frames, the tension relationship at the back will be destroyed again, causing an accident.

It is possible to increase the speed of the previous frame, but the increase speed should be small and progressive. While increasing the speed, observe whether the rolling piece of this frame has increased in the width direction. When raising the speed, pay attention to observe whether there is a trace of vertical loops in the rolling pieces between the two stands. The speed is increased until the rolling stock width of the stand meets the requirements. If the size of a rolled piece changes irregularly in the width direction, it may be caused by uneven local steel temperature; if there is periodicity, it may be that in the previous several passes, one of the stands rolls eccentrically rotated, or the pass A piece of the upper part falls off, commonly known as “meat loss”, which causes periodic inconsistencies in the size of incoming materials. The occurrence of the above situation should be dealt with according to specific reasons.

Generally speaking, the main method to adjust the tension is to adjust the speed of the rolling mill, but before this process is realized, it is necessary to ensure that the height of the rolling pieces of each stand meets the technological requirements. Simultaneous adjustment will inevitably cause adjustment confusion.

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