Analysis of Gear Damage and Start-up Difficulty in the Use of Rolling Mills

The key equipment in the steel rolling equipment is the hot rolling mill, which plays a crucial role in the rough rolling, intermediate rolling, and precision rolling of the billet. Its operational condition is closely monitored. After undergoing the rolling operation of the rolling mill, the steel billet enters the intermediate rolling mill, precision rolling mill, and other equipment for continuous steel rolling operations. During operation, the internal gears of the reducer and gearboxes act to buffer power and evenly distribute power, making them essential equipment in the steel rolling production line.

During the use of the hot rolling mill, malfunctions occurred, affecting normal production. Upon inspection, it was found that the gears had cracks or broken teeth. The causes of gear cracks or broken teeth in the rolling mill are not only related to the internal structure of the hot rolling mill gears but also have other significant factors.

Due to the need for shrinkage compensation, risers are placed on the inner edge of the gears, and the risers increase the thermal stress and heat stress during the cooling process of the castings in the hot rolling mill. When oxygen-cutting the risers on the inner edge of the wheel, thermal stress is increased. The temperature is high at the cutting position of the risers on the inner edge during the cutting process, resulting in lower strength than other parts of the wheel, forming a weak link and causing cracks.

When the diameter of the hot rolling mill rolls exceeds the specified standard, it significantly increases the frictional force during the rolling process. During overload, the operation of the rolling mill becomes difficult. Difficulty in starting may also occur when the motor power of the hot rolling mill is less than the rated power. Insufficient loading of the rolling mill also makes starting difficult. The impact rolling and frictional collision between the rolls increase correspondingly, leading to increased power consumption in the hot rolling mill.

Therefore, it is recommended to use a frequency-sensitive variable resistor low-voltage starting cabinet for the hot rolling mill controller, with a wound motor of 380V, 245KW, stator rated current of 464A, rotor current of 355A. Difficulties in starting the rolling mill can hinder continuous production, significantly affecting the economic benefits of the steel rolling plant. Therefore, addressing the problem of difficult start-up in the rolling mill is crucial.