Common pile-up accidents in steel rolling and their treatment measures

Analysis and Countermeasures of Accidents in the Rough and Middle Rolling Area

After the rolled piece is bitten into, pile steel between the racks

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cause of issue:

(1) The rolling speed and roll diameter are not set correctly;

(2) The tension setting is too small after changing the roller (groove);

(3) The steel temperature fluctuates too much;

(4) The roll breaks suddenly;

(5) The motor of a rolling mill suddenly increases or decreases due to the electronic control system.

Treatment measures:

(1) Accurately set the rolling speed, roll diameter and tension;

(2) Keep warm and wait for rolling, notify the heating furnace to adjust the firer;

(3) Replace the broken roller;

(4) Check the electrical system.

The head of the rolling piece piles up steel when the rack bites into it

cause of issue:

(1) The size of the rolled piece does not meet the requirements;

(2) Foreign matter or slippage in the rolling groove;

(3) The guide and guard are poorly installed, severely worn, or there are foreign objects such as iron oxide scale in the guide and guard; (4) There is a "split" in the rolling piece caused by defects such as delamination, inclusion or smelting waste in the billet;

(5) The bending of the rolling piece head caused by different diameters of the upper and lower rolls, uneven wear, or non-synchronization;

(6) Difficulty in biting or cracking of the head caused by too low head steel temperature;

(7) The rigidity of the rolling mill stand is not good, and there is deviation phenomenon in the rolling process;

(8) The billet is "out of square" severely;

(9) When the rolled piece comes out of the rough rolling stand, the head can't be smoothly bitten into the next frame or the head punching guard. Simply put, it is the head.

Treatment measures:

(1) Make appropriate adjustments to the roll gap of the rolling mill;

(2) Inspect, clean or polish the rolling groove;

(3) Check, clean, adjust or replace the guide guard;

(4) Check the blank carefully;

(5) Check the gap of the transmission parts or replace the roll;

(6) Improve steel tapping conditions;

(7) Turn off the high-pressure water for descaling;

(8) Reinforce the rolling mill stand;

(9) Install a sliding guide guard in front of the 1# rolling mill.

(10) Carefully check whether the imported guide guard of the previous flight is loose. The loose guide guard causes the rolling piece to bite into the box hole and is pressured by the imported guide guard, which makes the lower part of the rolling piece more pressure, which causes the lower extension to become larger and cause warping. The head eventually failed to bite into the rolling mill smoothly and piled up steel.

The rolling piece is stuck in the rack and piles up steel

cause of issue:

(1) Motor overload trip due to low steel temperature or high rolling speed; 

(2) Emergency stop when equipment or safety accident occurs.

Treatment measures:

(1) It should be analyzed and dealt with according to the specific situation.

Analysis and countermeasures of accidents in the pre-finishing rolling area

Stacking steel between racks

cause of issue:

(1) The roll diameter and roll gap are set incorrectly;

(2) The guide and guard are installed inaccurately, and the guide and guard are blocked or washed away;

(3) The rough and intermediate rolling tension is too large, and the rolled piece is "flicking" in the pre-finishing rolling;

(4) The bearing of the rolling mill or the roller box is burnt, which leads to the change of the material type of the secondary train;

(5) The self-locking performance of the reduction device is bad, and the material type changes due to vibration during rolling.

Treatment measures:

(1) Reset the roll diameter and roll gap;

(2) Check, replace and carefully adjust the center guide and guard;

(3) Control the size of incoming materials;

(4) Eliminate tension;

(5) Electrical or mechanical personnel inspect, repair or replace equipment.

Automatic stop for pre-finishing rolling

cause of issue:
(1) Failure of lubrication system;

(2) The motor tripped.

Treatment measures:

(1) Check the lubrication system;

(2) Electrical inspection.

Analysis and Countermeasures of Accidents in Finishing Rolling Zone

Pile of steel in the scrap box after finishing rolling

cause of issue:

(1) There are relics left in the guide groove after finishing rolling;

(2) The speed of the finishing mill and the dual-module mill does not match;

(3) The import guide for the final stand of finishing rolling;

(4) The water-cooled guide groove is severely worn;

(5) After the finishing mill, a certain water tank or a certain water valve is adjusted too large, resulting in large water resistance or residual water in the water tank

(6) Problems with the installation or design of the spinning tube;

(7) The input error of the roll diameter of the finishing mill results in a large gap between the actual speed of the finishing mill and the feedback, which does not match the speed between the laying machines.

Treatment measures:
(1) Check and clean the guide groove and guard;
(2) Correctly adjust the stacking relationship;
(3) According to the shaking situation of the steel behind the scrap box, open the water valve evenly and stably;
(4) Replace the spinning tube with stable design and mature technology;
(5) Confirm the roll diameter of the finishing mill.

Stacking steel between the inner stands of finishing rolling

cause of issue:

(1) The guide and guard clamp iron is blocked, the installation is not good, and the rolling guide guard is broken;

(2) Mismatched rollers;

(3) The roll gap setting is wrong;

(4) There are raw material broken materials and inclusions;

(5) There is tension in the front unit, leaving the tail in the finishing mill;

(6) Export of rolled products.

Treatment measures:

(1) Check and replace the guide guard;

(2) Re-arrange rolls and set roll gaps;

(3) Lengthen the cutting head and tail of the flying shear, and the rough and middle rolling post workers carefully check whether the semi-finished material at the 1# flying shear has inclusions, and if there is any inclusion, contact the 2# station and the 2# flying shear will be broken;

(4) Control the size of incoming materials.

Pile of steel at the flying shear

cause of issue:

(1) The cutting head (tail) is too long and stuck in the guide groove;

(2) Shear blades and switches are worn, deformed or incorrectly positioned;

(3) Uncut, uncut head or cut elbow affects biting;

(4) Misoperation of flying shears in the middle and out of control of shearing.

Treatment measures:

(1) Reset the length and tension of the cutting head (tail);

(2) Check the cutting blade and the front and rear guide grooves of the flying shear;

(3) Reset the leading coefficient of flying shear;

(4) Check the photoelectric cell, thermal test and power signal.

Pile of steel at the looper

cause of issue:

(1) The looper action time is incorrect;

(2) The set amount is too large or the speed setting is incorrect;

(3) The looper set-up roll or the rolling piece guide plate is seriously worn;

(4) The looper scanner is faulty or the front thermal check signal is blocked;

(5) Too much cooling water or too much water mist affects the detection effect;

(6) The looper suddenly falls off due to electrical or mechanical problems.

Treatment measures:

(1) Reset the parameters;

(2) Replace related spare parts;

(3) Check the above related equipment and its actions;

(4) Add a baffle and fan at the appropriate position of the thermal check signal;

(5) Electrical or mechanical personnel inspect, repair or replace equipment.