The maximum design speed of Chenggang high line is 113.26m/s, and the rolling speed is 90m/s. Product specifications < p5.5~16mm, the annual design production capacity of 400,000 tons. There are 28 rolling mills in the whole rolling line, including 14 roughing and middle rolling mills, which adopt flat and vertical alternating arrangement, 4 compact cantilever rolling mills for pre-finishing rolling, which adopt flat and vertical alternating arrangement, and 10 finishing mills, which are 45° top crossing arrangement. This paper analyzes the causes of some typical pile steel accidents in the process of high speed wire rod production, and puts forward the corresponding control measures to reduce pile steel accidents.
2. stacking steel accident causes and treatment methods
2.1 Rough rolling area
2.1.1 Pile steel at the head of rolling piece
(1) The friction of rolling groove after changing roll and groove is too small, causing the head of rolling piece to slip;
(2) The head of the rolling piece can not be successfully bitten into the downstream frame or the head of the top guide, the main causes of such accidents are loose inlet guide base, the rolling mill pass is not completely aligned, the size of the incoming head is out of line, the inlet guide is not installed to the middle;
(3) There are foreign bodies in the rolling groove or guide groove;
(4) the billet is seriously "out of square" and cannot enter the mill or bring out the outlet pipe;
(5) billet split head top outlet guide or roll.
The solution:
(1) Increase the friction of the rolling groove when changing the roll and changing the groove, the main method is to carefully polish the rolling groove with the grinder or take the spot welding method, and turn off the cooling water of the roll until it is completely bitten;
(2) Timely check whether the guide base is loose, whether the rolling line is centered, timely replace the seriously worn guide, and ensure the material type standard;
(3) In the rolling process, timely clean the oxide sheet and other debris remaining in the rolling line;
(4) Strengthen the inspection of the unqualified billet, find that the unqualified billet is removed in time, and the split in the rolling process should be stopped as soon as possible to reduce the scrap treatment time.
2.1.2 Pile steel in the middle and tail of rolled pieces
(1) After changing the roll and changing the groove, due to the improper setting of the roll gap, the improper size of the rolled piece will cause the stacking of steel;
(2) the defects of the billet, such as inclusions, bubbles, etc., break during the rolling process and cause stacking steel;
(3) When the speed of an intermediate mill is not set properly, it is actually in the state of stacking steel rolling, and the first half of the rolled piece is rolled by the front mill to maintain a micro-tension rolling, and when the tail of the rolled piece leaves the front mill, the tension is suddenly lost, resulting in the stacking tail at the stand;
(4) Due to the sudden increase or decrease in the speed of the motor of a rolling mill caused by stacking steel;
(5) The pile steel is caused by the sudden break of the roll or serious damage to the first few times of the guide.
The solution:
(1) Accurately set the bottom of the groove after changing the roll and groove, correctly calculate the roll diameter and speed, and reduce the speed error;
(2) Strengthen the inspection of unqualified billets;
(3) Correctly adjust the tension between the frames;
(4) Check electrical equipment and replace damaged electrical components;
(5) Check the roll cooling water, adjust the steel temperature, and prohibit rolling low-temperature steel and blackhead steel.
2.2 Pre-finishing area
(1) The wrong setting of roll diameter and roll gap causes stacking steel;
(2) improper guide and guard cause pile steel;
(3) the coarse and middle rolling tension is too large, and the rolled piece "tails" caused by the pile steel in the pre-finishing rolling;
(4) Due to insufficient oil and gas or no oil and gas caused by burning of the reactor steel;
(5) The automatic detection system shows that "pre-finishing water pressure" and "pre-finishing lubrication failure" cause pre-finishing rolling to skip.
The solution:
(1) Accurately set the phase gap when changing the roll, correctly measure the spoke diameter and speed;
(2) Carefully check and adjust the guide and guard to the center;
(3) Standardize the material type to eliminate excessive tension in rough rolling;
(4) Timely check the oil and gas situation, and replace the burning guide in time;
(5) Check the cooling water pressure, pipelines and manual valves; Check the lubrication system and electrical equipment.
2.3 Finishing rolling, pinch roll, spinning machine area
2.3.1 Stacking steel inside finishing mill
(1) the explosive cracking of the roller ring;
(2) When replacing the roller ring, the roller ring loses pressure due to the failure of the pressure trolley or the insufficient pressure;
(3) improper installation or damage of guide;
(4) The fishing line inside the finishing rolling suddenly breaks;
(5) Due to improper setting of roll gap, non-standard material type before finishing rolling and inappropriate tension caused by finishing a rack pile tail.
The solution:
(1) Find out the reason of the roller ring burst;
(2) Check whether the pressure display of the suppressing car is normal, and perform the correct operation method;
(3) Install in place, check and replace the guide in time;
(4) Do frequent spot check, frequent replacement, improve the responsibility of the post;
(5) Reset the set and control the incoming material size.
2.3.2 Scrap box pile steel in finishing rolling area
(1) There are relics in the guide groove after finishing rolling, and problems in the guide of the finished product import cause stacking steel;
(2) The speed mismatch between the finishing mill group and the spinning machine causes the stacking of steel;
(3) Defects such as blank inclusion cause sudden breakage in the process of spinning.
The solution:
(1) Check, clean the guide groove, guide and guard, and replace it if necessary;
(2) Correctly adjust the stacking relationship between finishing mill, pinch roll and spinning machine;
(3) Strengthen the inspection of unqualified billets.
2.3.3 The finishing mill is exported to the spinning machine for stacking steel
(1) Between the finishing mill and the spinning machine, there is often a pile of steel for unknown reasons after 3-10 turns of spinning, the rolled piece appears as a pile of steel first, then a pull off, and the pile of steel occurs in the scrap box after several turns of spinning.
(2) Due to the serious wear of the spinning tube, the spinning loop is chaotic and irregular when the spinning tube is about to wear through, and the head of the steel is stuck in the spinning tube in serious cases;
(3) Improper clamping action of the pinch roller or improper setting of the roll gap will cause the pile of steel.
The solution:
(1) When rolling small size discs, if the spinning 3-10 turns of the pile steel with unknown causes occurs, the most important check is the alignment of a certain guide groove, especially the position of the waste box guide groove and the population section of the water tank guide groove, whether the guide groove before and after the pinch roll is centered, and the general position of the scrap steel can also be checked according to the length of the spinning wire; If the rolling disc screw in addition to checking the above position, should also check the water pressure is appropriate, if necessary to reduce or close the cooling water.
(2) Find the cause of chaotic and irregular spinning and replace the spinning tube in time;
(3) Timely check the electrical device and set the correct roll gap.
2.4 Flying scissors, looping place
2.4.1 Flying shear pile steel
(1) the cutting head (tail) is too long and stuck in the guide groove or is not cut, not cut the head or cut the elbow;
(2) The cutting edge and switch wear seriously;
(3) mid-flight shear misaction.
The solution:
(1) Reset the length and tension of the cutting head (tail) and reset the leading coefficient of flying shear;
(2) Regularly replace the cutting edge, turning device and other wearing parts;
(3) Check the photocell, thermal detection and power signal.
2.4.2 Looper stack steel
(1) Looper lifting early or when the last rolled piece leaves the looper, the lifting roll does not fall off, causing the rolled piece to bump head;
(2) the looper falls early, and the rolled piece is in an unstable state in the looper, resulting in a tail pile of steel;
(3) Due to the large water mist and more oxide sheet blocking the thermal inspection lens, the steel can not be scanned;
(4) looper setting is not appropriate;
(5) the sleeve roller and guide roller are seriously worn or stuck;
(6) Horizontal looper looper table wear seriously, causing stacking steel.
The solution:
(1) Timely check whether the electrical components are damaged;
(2) Add a fan to purge the lens;
(3) Regularly clean the iron sheet around the looper;
(4) Reset looper parameters;
(5) Timely replacement of the sleeve, guide coil and other wearing parts, and regular repair welding of the looper wear parts.
3. Conclusion
Since the trial production of Chenggang high line, with the continuous improvement of operation proficiency and fault judgment level, the pile steel accidents are decreasing day by day. Through practice, it is realized that the fast and accurate judgment of the reactor steel fault in the process of high line production can not only effectively reduce the fault handling time, but also effectively formulate preventive measures, and fundamentally reduce the occurrence of reactor steel accidents. The above is only a brief analysis of some common steel stacking phenomena, and in the actual production process of steel stacking accidents are a variety of forms, which requires continuous learning, efforts to improve a variety of operating skills, to find out the cause and take appropriate measures to avoid it.
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