Cause Analysis and Preventive Measures of Roll Neck Fracture

1. Roller Material: Chrome Molybdenum Nodular Infinite Chill

Roller body specification: ¢570*1000mm

Types of rolled products: ¢10-25mm rebar

Use rack: blanking

Objection form description: In the first cycle of use, the roll neck fracture occurs during the rolling process, the roll neck fracture is torn along the direction of the roll body, and the macroscopic structure of the section is fine.

Cause Analysis:

The roll neck fracture of the roll is caused by excessive thermal shock and twisting force during use, which causes the instantaneous reduction between the roll gaps to increase, and the excessive torque causes the roll neck to break. When the roll neck breaks, it is torn in the direction of the roll body.

Preventive corrective measures:

During the rolling process, strictly follow the operating procedures, strengthen supervision, prevent the existence of low-temperature rolling or rolling with foreign objects, reduce the rolling reduction and twisting force of the rolls, and effectively prevent similar accidents.

2. Roller material: nickel-chromium-molybdenum chilled centrifugal composite III

Roller body specification: ¢300*600mm

Types of rolled products: ¢8mm wire rod

Use rack: K1

Objection form description: In the first cycle of use, the roll neck (flat head at the end of the drive shaft) was broken during the rolling process, and several pieces were broken continuously, and the macroscopic structure of the fracture was fine. As shown

steel mill rolls

Cause Analysis:

The lower roll neck of the roll (the end of the roll connected to the universal shaft, that is, the position of the flat head at one end of the drive shaft) is broken, and the macroscopic structure of the flat head fracture is fine, no slag inclusions appear, and no radial shape appears. The roll is in the rolling process. The fracture of the flat head at the end of the drive shaft is due to the fact that the connected universal shaft is not concentric with the bearing seat and roll assembled by the roll, so the part where the drive shaft and the roll are connected (the flat head of the lower roll neck) produces a huge twisting force, resulting in The flat end of the roll was twisted off.

Preventive corrective measures:

Regularly inspect the rolling mill, bearing housing, and Cardan shaft to ensure that the roll, bearing housing, and Cardan shaft are concentric, reduce the twisting force between the flat end of the roll and the Cardan shaft, and effectively control the occurrence of this kind of roll neck fracture.

Roll material: Nickel-chromium-molybdenum infinite chilled centrifugal compound II

Roller body specification: ¢360*600mm

Types of rolled products: ¢6.5-8mm wire rod

Use rack: K14

Description of objection form: In the second cycle, the roll neck was broken during the rolling process, the macroscopic structure of the fracture was fine, and the section was not straight and distorted.

steel mill rolls

Cause Analysis:

1. The roll neck fracture of the roll is caused by excessive thermal shock force and twisting force during use, which causes the instantaneous reduction of the upper and lower rolls to increase. The excessive torque causes the roll neck to break or the bearing locks during the rolling process, causing the roll to rotate. Blocked, the torque continues to increase, causing the roll neck to break.

2. The inner diameter of the bearing sleeve used is inconsistent with the size of the roll bearing, which causes the rolling process to burn the inner ring and cause the roll neck to break.

Preventive corrective measures:

1. Improve the cooling system to ensure good cooling effect during the rolling process, eliminate low-temperature rolling of rolled products, and control the pressure and twisting force on the rolls; increase inspection efforts to ensure lubrication between each drive shaft and prevent The transmission is blocked and the quality accident is caused.

2. Check whether the size of the bearing sleeve and the roller bearing meet the requirements for use, increase the inspection of the maintenance work of the roller and the bearing, prevent substandard products from being put into use, and effectively control the occurrence of unnecessary accidents.

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