- Slitting knife sticks to steel
The sticking of steel on the slitting knife refers to the
phenomenon that the two sides or one side of the slitting knife stick to the
slag during the slitting and rolling production process, which will eventually
lead to the failure of the slitting. The main reasons for the sticking of the
slitting knife are as follows:
1. The rolling temperature is too high. If the opening
temperature is too high, during the cutting process of the finishing rolling
zone, when the reduction of the cutting wedge is very large, a large amount of
heat is generated due to the sharp deformation, which causes the local metal
temperature to rise rapidly and the shape of the cutting strip is irregular,
causing The slitting knife sticks to steel.
2. If the incoming material is too large or too small, the
slitting and rolling follows the axe principle, and the incoming material must
match the angle of the 16-frame slitting wedge. 15 If the shape of the material
is too large or too small, it will cause difficulty in cutting, resulting in
excessively large slitting belts. During the advancement of the rolling piece,
friction between the slitting belt and the slitting knife will cause steel
sticking.
3. The slitting wheel is off-track or misaligned with the
rolling groove. The installation of the splitting guide guard must ensure that
the splitting wedge, the splitting wheel, and the splitting knife are three
points and one line. The alignment is good. If the installation is not correct,
the material and the cutting wheel cannot be aligned and the cutting is off,
causing the cutting belt to be too large, and friction with the cutting knife,
causing steel sticking.
4. The slitting knife is not cooled well, and the slitting guide
must ensure sufficient cooling, especially the slitting knife. During the
normal production process, due to the wear of the billet and the rolling
groove, the surface of the rolling piece has a small oxide scale and the shape
of the slitting strip. Irregular, friction with the slitting knife sticks on
both sides, if the cooling effect is not good, it will stick more and more, and
eventually lead to rush out of the guide pile steel, and the downstream rolling
mill cannot be adjusted.
5. The slitting knife spacing is not appropriate. After the
rolling piece enters the slitting box, it will be at a certain angle. If the
slitting knife spacing is not set, the rolling piece will rub against the
slitting knife and stick to the steel.
6. The splitting hole design is unreasonable. The design of the
15-16 rack hole pattern system is very important, and the splitting angle
design must match.
7. The rolling mill has poor rigidity, large bouncing, and poor
material shape control.
8. The length of the slitting knife is inappropriate, and the
three slitting is more obvious. Too close to the slitting wheel will cause
inconvenient slag discharge and cause sticking of steel.
9. The angle design of the splitting wheel is unreasonable and
the splitting is not smooth.
10. The shape of racks from 12 to 18 is not well controlled, and
the material will be twisted obliquely, too large or too small, and the head is
large and the tail is large, causing stickiness and rigidity.
11. There is a problem with the billet itself, which contains
air bubbles and blooms.
12. The rolling groove of the key train is aging or jumping out
of the groove.
13. The guide beam and the guide guard of the key sorties are
not aligned with the rolling center.
14. The tension of each flight is not well controlled or the
temperature is not stable.
15. The guide plate or guide plate is excessively worn or the guide groove assembly is faulty.
1. The steel temperature should be controlled according to the process requirements. When the load of the main motor is satisfied, the steel temperature should be controlled at 1000 to 1050 degrees Celsius, preferably not more than 1100 degrees Celsius.
2. Strictly control the size of the good material type according to the process requirements. The size deviation of the rough rolling six stands is controlled within ±0.5 mm, the medium rolling dimension deviation is controlled within ±0.3mm, and the finish rolling dimension deviation is controlled within 0.2 mm. The pre-cutting and cutting sorts should be strictly controlled in accordance with the technological requirements. Ensure the fullness of the split sorties.
3. The installation of the slitting guide should be accurate, keeping the slitting knife, slitting wheel, and slitting groove in the same straight line, and at the same time strengthen the cooling of the slitting guide and rolling groove, and observe the degree of turning steel of the material type in time. The designer must do a good job of design proofreading for the hole pattern.
4. The spacing of the slitting knives is certain, carefully check whether the spacing of the slitting knives is appropriate.
5. Control the material type of each pass as required.
6. Make an online inspection of the rolling line in time. Install the guide guard and guide guard beam correctly.
- The problem of the four-line difference of the slitting rolling
line
Although the slitting rolling process has effectively increased
the operating rate and increased the output significantly, it is affected by
various factors such as steel temperature fluctuations, rolling groove wear,
pass system design, guide and guard installation, and rolling groove processing
accuracy. The size of the parts can not be exactly the same, that is, there is
a line difference. If the quality of the steel is required to obtain higher
economic benefits, this requires various means to narrow the gap between the
lines. The main reasons for the line difference are as follows:
1. The imported guide guards for pre-cutting 15 racks or cutting
16 racks are not aligned with the rolling line and are biased to one side. At
this time, the side that is biased after the incoming material is cut is large
due to the large cross-sectional area, resulting in a large size of the
finished line.
2. The hole type wear is inconsistent. Due to the inconsistent
cooling of the rolling groove, the irregular shape of the previous pass or the
design of the guide and guard pass, the cross-sectional area of the
severely worn line will increase, resulting in the size of the finished
product.
3. The roll gap on both sides is inconsistent. During the
roll-changing adjustment, due to the inconsistent roll gap control on both
sides of the 15-18 racks, the hole area on the side with the larger roll gap is
larger, which leads to differences in the finished product.
4. The processing precision of the rolling groove is not high.
This is mainly related to the material of the roll, the wear and repair
accuracy of the forming tool in the repair workshop, and the processing method.
5. There is a problem with the material shape control of the
12-16 sorties. Slicing production pays great attention to the matching of 12-16
sorties. If the matching is not good, it will cause line difference.
6. The main reasons for the line difference are generally
concentrated on the aging of the K4 rolling groove, the alignment problem with
the K3K4 guide and guard, and the K6 material shape change problem.
The solution to the four-wire difference
1. Install guide and guard accurately. Before changing the
rollers, the guide and guard must be pre-adjusted to ensure that all positions
are aligned and fixed.
2. Improve 15, 16 cooling water pipes, strengthen the cooling
effect, and do a spot check during the production process.
3. Start the rolling mill when changing rolls, measure the roll
gap on both sides with the same welding rod, and control the deviation within
0.1mm.
4. Improve the material of the rolls, use high-speed steel rolls
for 15, 17, 18. Contact processing department to improve processing accuracy.
5. Control the shape of each pass in strict accordance with the
process requirements, and adjust the guide and guard gap with the sample bar as
required.
- 18 rack top exit failure
During the slitting and rolling production process, the failure
of the top outlet of the 18 stand is more common, which is a major failure
point that restricts the four slitting production. It is mainly manifested by
the sharp bending of the front end of the inner or outer two-wire steel in the
direction of the slitting belt, and the pipe The tip of the tongue falls off,
or bends 180 degrees and rushes out from the exit to be stuck in the guide
groove to pile steel. The main reasons for this phenomenon are as follows:
1. There are defects in the pass design, mainly due to the
problems in the allocation of parameters during the pass design, which makes
adjustments too difficult and requires extremely high requirements for the
overall quality and operational level of employees.
2. The design of the 17-frame hole-shaped slot is too large, and
the slitting belt cannot be processed well.
3. Inaccurate control of material shape. 15 racks are not fully
filled, or the shape of 16 racks is too small, the front ends of the two lines
are severely asymmetric after cutting, the deformation of the 17 racks is
uneven, and the slitting belt is not processed well, and the ejection
phenomenon occurs when entering 18 racks, or The shape of the 12-16 racks is
too large, and the 18 racks are deformed severely and unevenly, causing the
ejection phenomenon.
4. Inappropriate control of the guide and guard clearance of 15
racks and 16 racks is not good for neutrality. The front end of the rolling
piece is bent and cut off when cutting, causing the head size to be too large
or too small. After 17 racks, the top exit of 18 racks is caused.
5. The temperature at the slitting belt is relatively high, and
it is not easy to get out of the groove on the 18 racks.
6. There is a problem with the guide and guard design or the
size of the outlet cavity of the 18 racks is too large, which is relatively far
away from the roll, which cannot effectively prevent the head shape change of
the 18 racks.
7. The guide guards of the 18 rolling mills, and the guide guard
beams were not assembled and aligned as required.
8. The material shape of the 17 frame is not well matched with
the imported guide plate.
9. The splitting guide guard is not assembled as required, or
the splitting wheel has the wrong eccentric direction or the direction is not
uniform.
10. The transfer of steel between the previous sorties,
especially between the 12-13 racks.
11. The torsion angle of the exit of the 17 aircraft was not
adjusted properly.
12. The rolling groove is severely worn.
13. Splitting wheel and splitting guide and guard design issues.
14. The gap of the connecting shaft is too large.
Solutions for 18 rack top exit failures
1. Optimize the pass system and redistribute the reduction of
each pass. Determine the production process.
2. To explore the best technology, the focus is on heating
parameters, the size of each rack, the speed and current parameters of each
rack, and the formation standards are strictly implemented in each team.
3. Improve the assembly level of the guide and guard of the
rolling mill, and focus on the assembly of the guide and guard of the finishing
rolling mill 15-16 to ensure the rigidity and axial stability of the rolling
mill. Strictly do the pre-adjustment and installation of the guide and guard.
4. Perform key cooling on the slitting belt.
5. Improve the form of 18 guide guards and the size of the inner
cavity, and control them within a certain range, so that the tip of the tongue
is as close to the deformation zone as possible to improve the guidance.
6. The material shape of the 17 rack and the installation of the
imported guide plate should follow the following principles; when the hole
pattern of the 17 rack is not full, the guide plate is not easy to deviate to
cut the belt. When the 17 holes are full, the guide plate should be deflected
in the opposite direction of the slitting belt.
7. Check the roll wear in time.
8. Change the form of guidance and guarding.
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