Common faults and maintenance measures of continuous casting machines

High-efficiency continuous casting technology is a continuous casting system technology with high casting speed as the core and high-quality, defect-free slab production as the basis to achieve high continuous casting rate and high operating rate. The premise of efficient continuous casting technology is the trouble-free and stable operation of continuous casting equipment. Therefore, it is crucial to promptly discover and eliminate the causes of continuous casting machine production failures, as well as to maintain and repair the continuous casting machine. This article analyzes the common faults that have occurred in the three continuous casting machines since they were put into production and the corresponding maintenance measures taken.

Keywords: continuous casting machine; fault; maintenance measures

For continuous casting production, on the premise of satisfying product variety and quality, increasing the casting speed and operating rate of the continuous casting machine means increasing output and increasing efficiency. The safe, stable and trouble-free operation of the continuous casting machine is crucial.

The three continuous casting machines of the Wire Rod Division were all designed by a domestic company and put into production in October 2011. After more than three years of operation, some common mechanical failures of the continuous casting machine gradually appeared. Combined with the actual situation on site, how to analyze the common mechanical failures of continuous casting machines and find out the causes of the failures. Taking corresponding process technology improvement measures to avoid the occurrence of failures and doing systematic maintenance are the main issues faced by continuous casting maintenance and inspection work.

Common faults and maintenance measures of continuous casting machinery

Since the three continuous casting machines were put into operation in October 2011, some common continuous casting machine mechanical failures have occurred during the many years of operation of the continuous casting machines. Based on the actual situation on site, common mechanical failures were analyzed and corresponding maintenance and improvement measures were summarized.

?Common mechanical failures and improvement measures of large bale rotary table

(1) Hydraulic slip ring. In order to realize the rotation of the bale rotary table, the three continuous casting machines all use 22-channel hydraulic slip rings. They are installed vertically and include hydraulic, air and backup channels. The working pressure of the hydraulic system is 20MPa. After one year of use, hydraulic oil leakage began to occur, and it was manifested as oil leakage at the joints of the outer cylinder wall. In order to make the bale rotary table compact, the installation position of the hydraulic slip ring is not conducive to construction operations, so the replacement operation takes a long time and has a great impact on production. Improvement measures: After repeated research and discussion, the sealing form of the hydraulic slip ring was changed to YX ring seal, made of PTFE. The seal has the characteristics of simple structure, small cross-section, easy installation, low cost, and good sealing performance; the hydraulic slip ring is also periodically replaced to ensure its normal use. In addition, its fixed lever also broke due to welding quality, causing part of the hydraulic hose to be severed, causing very serious consequences. It is recommended that the welding of the lever here be inspected for flaw detection if conditions permit, and its welding deterioration should be checked every week.

Big bag skateboard mechanism failure and improvement measures

The accident system was fully considered in the design of the bale skateboard mechanism. However, after operation, many failures occurred where the skateboard could not be closed normally, and fire accidents occurred due to oil leakage. It was analyzed that the cause of the accident was mainly caused by the hydraulic cylinder and the connecting oil pipe. The working position of the hydraulic cylinder was located directly above the opening of the tundish cover. The molten steel in the tundish radiated serious heat to it. The temperature of the piston rod of the hydraulic cylinder was measured to be as high as 420°C. ℃. In this regard, the following maintenance measures were focused on: first, reducing the opening of the tundish cover to reduce the thermal radiation of molten steel to the hydraulic cylinder; second, adding a heat-insulating cushion layer under the hydraulic cylinder; third, making a protective bracket for the oil pipe , and add a layer of heat-insulating protective sleeve to the original armored oil pipe; fourth, cancel the quick connector connecting the hydraulic cylinder and the oil pipe to prevent the quick connector from failing and blocking the oil line under high temperature conditions; fifth, control the hydraulic valve of the skateboard cylinder regularly Carry out replacement, cleaning and testing.

?Tundish truck failures and improvement measures

(1) Tundish truck manipulator. The three continuous casting machines all have the ladle long nozzle manipulator fixed on the side of the ladle rotary table and are driven by hydraulic pressure. A total of 10 failures occurred this year, 5 of which were caused by pressure regulating valve failures, 3 of which were due to blockage of the pressure regulating valve and 2 of which were due to inaccurate pressure regulation.

The prevention and improvement measures are as follows: First, regularly replace and test the manipulator pressure regulating valve at the long nozzle of the large package, send the problematic pressure regulating valve for repair in a timely manner, and detect the normal pressure regulating valve for cleaning and backup; second, insist on doing a good job Oil cleanliness testing work to monitor the cleanliness of the oil; third, it is emphasized that operators must prevent contamination of the system when replacing oil pipes, seals, valves, etc.

(2) Tundish roaster. The tundish roaster is a vertical hydraulically driven roaster. Due to the working environment, the middle bag often cannot be lifted after baking, resulting in the inability to start pouring or change the bag normally. Through the following technical transformation, the thermal shutdown caused by the failure of the roaster to lift up properly has been eliminated, unsafe factors during equipment maintenance have been eliminated, and the service life of spare parts has been improved: First, the original solenoid reversing valve power supply is 220VDC, and there is If there is a major safety hazard, change it to a 24VDC safe power supply; secondly, if the roaster cannot be lifted normally after baking the buns, it will cause a thermal shutdown. A pressure relief ball valve should be added to the circuit of the rodless cavity of the hydraulic cylinder to Eliminate this hidden danger; thirdly, when the main pump is transferred to the backup pump, there is a great safety hazard in the process of disassembling and assembling the oil pipe. A ball valve is added between the main pump and the backup pump to facilitate the activation of the backup pump.

?Problems with crystallizer vibration and improvement measures

When the continuous casting machine was put into operation, there was a bonded steel leakage accident caused by improper amplitude adjustment; after the equipment was operated for a period of time, the vibration marks were irregular and too deep. In order to solve these problems, the following series of process technology improvements have been carried out.

(1) Calibration of mechanical equipment. After the vibration device has been running for a period of time, it is easy to deflect due to stress release, loose bolts, changes in billet resistance, large temperature changes, etc. It is necessary to detect the online vibration status of the vibration device. According to the actual situation on site, select the CVD200 series sensor detection method with higher accuracy to regularly detect the online vibration status to ensure that the longitudinal and lateral deflections are controlled within 0.1mm. For vibration devices whose deflection exceeds the range, measures such as adjusting the tightness of the leaf spring and adjusting the buffer spring should be taken to make the vibration parameters normal. Regularly calibrate the vibration device to ensure that the vibration marks on the four surfaces of the billet are uniform and neat.

(2) Optimization of vibration parameters. Generally speaking, transverse cracks and vibration marks on the surface of the cast slab are symbiotic. To reduce transverse cracks, the depth of vibration marks must be reduced. Under normal operation of mechanical equipment, vibration marks depend on vibration parameters such as vibration frequency, amplitude, negative slip time and vibration waveform. One is the choice of amplitude. The smaller the amplitude, the smaller the amount of mold slag inhalation, which affects the lubrication of the mold copper tube and the shelling of the continuous casting billet, and can easily cause adhesive leakage accidents. The larger the amplitude, the longer the negative slip time, the larger the deflection and it is difficult to control, and the deeper the vibration marks, which can easily cause transverse cracks on the surface of the slab and pull-off accidents. The second is the choice of vibration frequency. Considering that the pulling speed is extremely low when pouring is started, if the vibration frequency is too low, it is easy to cause bonding and leakage accidents. The parameters are short-arm four-bar mechanism, sinusoidal curve, amplitude ±4; casting machine radius 10m; vibration frequency: 26-260 times/min; motor power 7.5kw, speed 1500r/min; reducer speed ratio 5.6, output speed 268; Casting machine flow spacing is 1250mm. By controlling the vibration parameters through the vibration parameter model, the vibration frequency can maintain a good linear relationship within the normal pulling speed range, thereby ensuring that the continuous casting billet has good vibration marks.

Conclusion

High-efficiency continuous casting is a systematic project. Only through the comprehensive application of various new continuous casting technologies and continuous development and innovation can the further development of high-efficiency continuous casting be promoted. In continuous casting production, the efficient and stable operation of continuous casting equipment is the key to continuous casting production. This article summarizes some common faults that have occurred since the three continuous casting machines were put into production and the related process and technology improvement measures taken. One is to provide technical support for the smooth flow of production, and at the same time to provide production technology maintenance for the equipment maintenance of the continuous casting machine. experience.