Reasons and treatment of pile-up of high-speed wire rods during rolling

1 Introduction

The production line equipment of the No. 1 Wire Rod Plant of Beijing Shougang Co., Ltd. imitates the design of the fifth-generation Morgan rolling mill and is produced by domestic manufacturers. The maximum stable rolling speed of this production line is 88m/s. The whole line consists of 28 rolling mills, including 14 roughing and intermediate rolling mills, 4 pre-finishing mills, which are alternately arranged horizontally and vertically, and the 10 finishing mills are arranged at 45° at the top. Feed roll and laying machine.

The product specification is φ5.5—φ16mm, the specification span is large, and the variety of products is wide. Judging from the current production situation, the steel stacking accident rate of small-sized wire rod products below φ6.5mm (including 6.5mm) is much higher than that of other specifications due to the fast-rolling speed and small section size. According to the classification of different rolling areas, this paper introduces the causes and solutions.

steel rolling

2 Cause analysis and measures of steel stacking

2.1 Rough and medium rolling area (1-14 frames)

2.1.1 The rolled piece cannot be successfully bited into the next pass, resulting in piled steel

The main reasons for such accidents are:

①The front of the rolled piece is tilted after coming out from the last pass;

②The rear end of the last one is poured to raise the exit guide;

③ Inappropriate adjustment of the opening of the import guide;

④ The guide and the pass are not aligned (the rolling line is not correct);

⑤ The slot slips;

⑥ The size of the rolled piece does not meet the process requirements;

⑦ The front head is split due to the billet.

Treatment measures:

①For the warped head of the rolling piece, it is necessary to check the diameter and wear of the upper and lower rolls, the gap at the connection of the transmission parts, and the consistency of the import and export guides;

②Reasonably adjust the opening of the inlet guide and the distance between it and the roller;

③ If the setting of the roll gap for the new slotted hole is too small, make appropriate adjustments to the roll gap of the rolling mill or re-grind the slotted hole;

④ Make appropriate adjustments to the roll gap of the rolling mill;

⑤ Carefully check the blank, lengthen the length of the cutting head by 1# shear.

2.1.2 Stacking steel between the stands after the rolling stock bites

main reason:

①Incorrect setting of parameters such as rolling speed and roll diameter caused by man-made reasons;

②The adjustment of the stack-pull relationship after changing the roller or slot is not appropriate;

③ The billet temperature fluctuates too much;

④The speed of a rolling mill is suddenly increased or decreased due to electronic control;

⑤ The operator of the main console adjusts the wrong number of revolutions or sorties when adjusting the speed of the rolling mill;

Treatment measures:

① Correctly set the rolling speed, and roll diameter, and reasonably adjust the stack-pull relationship between the rolling mills. Do a good job of confirmation between the two;

②Notify the heating furnace to adjust the fire, and at the same time keep warm and wait for rolling;

③Professional electrical inspection, reverse the spare cabinet.

2.1.3 Tail pile of steel after rolling

The main reason is that at the upstream stand when the rolling stock pulls the steel when the rear tail is separated from the upstream stand, the steel is stacked on the downstream stand. Treatment measures: Reasonably adjust the stack-pull relationship and the size of the rolling mill.

2.2 Pre-finishing area (15-18 stands)

2.2.1 Steel stacking between racks

main reason:

①The parameters such as roll gap, roll diameter and rolling speed are set incorrectly;

②The installation of the guide is not suitable;

③The guide strikes iron;

④ Coarse-medium rolling and drawing steel cause the rolled piece to be left behind in the pre-finishing rolling;

⑤The rotation speed of a rolling mill is abnormal due to the reasons of electric control.

Treatment measures:

①Recheck the setting parameters;

②Check, replace or adjust the import and export guides;

③Adjust the height of the inner looper in the pre-finishing rolling and strengthen the inspection;

④ Reasonably adjust the stack-pull relationship of the continuous rolling mill;

⑤Electrical professional inspection and at the same time turn down the spare cabinet.

2.2.2 Jumping in a certain sort of pre-finishing rolling

main reason:

①Pre-finishing cooling water pressure and lubrication system failure;

②The motor trips;

③ The role of the accident detection system.

Treatment measures:

①Check the cooling water pressure and the control water valve beside the machine;

②Professional equipment inspection and lubrication system;

③ Check whether the pre-finished fishing line pendant is fastened, and check its proximity switch at the same time.

2.3 High-speed area (finishing mill to laying machine)

2.3.1 Steel stacking between stands in the finishing mill

main reason:

①The guide wheel does not rotate or the bearing burns;

②The rolling piece is split;

③The guide or the roller ring is wrongly installed;

④ Improper setting of roll gap or inappropriate size of incoming material;

⑤The roller ring is broken;

⑥ Broken fishing line will cause the rolling line to break automatically.

Treatment measures:

①Replace the guide guard, and at the same time strengthen the correctness of the guide guard installation;

②Strengthen the blank inspection and lengthen the length of the cutting head;

③Recheck and adjust the roll gap;

④Replace the roller ring and check the cooling water pipe at the same time.

⑤ Check the proximity switch at the fishing line pendant and check whether there is scrap steel at the guide in the finishing mill. If there is, it means that the front and rear tails are stacked in the finishing mill, and the roll gap in the finishing mill is reset.

2.3.2 Steel stacking at the scrap box of the finishing mill

There are two cases, one is stacking steel without spinning, and the other is stacking steel after spinning several turns.

The main reasons are:

①The cooling water in the water cooling section cannot be closed normally or opened too early;

②There are foreign objects in the water cooling section;

③The installation of the water-cooled guide groove is dislocated;

④The water valve of the first water-cooling box after the finishing mill is opened is too large or the water pressure is too large;

⑤ The speed matching between the finishing mill, pinch roll, and laying machine is not good;

Treatment measures:

①The electric control professional inspects the water valve control system and manually tests the water, and the main console adjusts the opening delay;

②Check whether the water-cooling nozzle and guide groove are installed correctly and whether there is looseness, and at the same time check whether there are foreign objects, and use a φ13mm round steel to pass through the water-cooling section;

③ Check the speed match between the three;

④The use specifications of the water-cooled nozzles and guide grooves can be enlarged, such as replacing φ12mm with φ16mm.

2.3.3 Steel stacking at the pinch roll laying head

main reason:

①The inlet and outlet conduits of the pinch rollers are not installed correctly, are severely worn or have foreign objects in the conduits;

②The detection signal before the pinch roller fails, so that the pinch roller cannot be opened/closed on time;
③ The spinning tube is seriously worn;

④The setting of the delay time of the clipped tail is too short, causing the tail to be lost;

⑤ Speed ​​mismatch between finishing mill and laying machine;

⑥Internal quality defects (smelting defects) or rolling defects (severe folds or ears) of the wire rods cause piled steel.

Treatment measures:

①Check and replace the inlet and outlet conduits;

② Electrical professional inspection and detection signal;

③Replace the laying tube;

④ Extend the delay time of the clipped tail;

⑤ Reasonably set the speed matching between the finishing mill and the laying machine;

2.4 Steel stacking at flying shears

main reason:

①The shearing speed of the flying shear does not match the speed of the upstream rolling mill, and there is a bend in the front and back of the cutting, resulting in piled steel;

②The length of the tail after flying shearing is too short so that the tail is not completely cut off and brought into the next rolling mill;

③ The shearing blade and the switch are seriously worn, causing the shearing position to be incorrect;

④The flying shears malfunction in the middle, and the shearing is out of control.

Treatment measures:

①Reset the lead coefficient of the flying shear;

②Adjust the length of the cutting head and tail;

③ Check the front guide groove of the cutting edge and flying shear;

④Check the photocell and thermal detection signal.

2.5 Steel stacking at looper

main reason:

①The looper delay setting is incorrect;

②The height setting of the looper is inappropriate;

③The lifting roller, guide roller or guide plate of the looper is seriously worn;

④ Looper scanner failure;

⑤ The front thermal detection signal is blocked;

⑥ Too much water mist or sunlight exposure will affect the inspection effect.

Treatment measures:

①Reset or adjust parameters;

②Replace process spare parts, or repair welding of guide plate;

③Replace the looper scanner and re-adjust the zero position;

④ Add a fog blower in the place where the water mist is large and add a shielding plate at a suitable angle for sunlight exposure.

3 Conclusion

In the production process, when a steel stacking accident occurs, due to the limitation of time and indicators, it is necessary to quickly and accurately find the cause. This requires a comprehensive consideration of the accident that occurred, and the cause of the multi-faceted search, so as to shorten the processing time and avoid repetition. Sexual accidents happen. It is also required that the on-site operators continuously and regularly check the size of the rolling stock, the stacking relationship of the rolling mill, and the guide and guard conditions in daily production, so as to better reduce the frequency of accidents.

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