This article mainly introduces common faults and solutions to the crystallizer vibration of the 2# continuous casting machine. The 2# continuous casting machine is designed by DANIELI. The crystallizer and the vibration of the crystallizer reflect the principle of overall motion. The vibration device is directly driven by dual hydraulic cylinders, which is not only easy to maintain, but also generates more waveforms, and the waveform and amplitude can be adjusted at any time.
Keywords: continuous casting; crystallizer; hydraulic vibration; rolling elements; servo control
Introduction
The purpose of mold vibration is to improve the lubrication condition of the mold through the penetration of protective slag into the mold wall, so as to maintain small mold friction and prevent the cast slab from sticking to the copper plate during the solidification process. A steel plant built a slab continuous casting machine with an annual output of 1.52 million tons in 2007. It adopts the principle of integral motion mold (INMO). This mold vibration system can provide precise guidance of mold vibration according to the movement trajectory of the casting strand. , and can also provide flexible operating modes according to the amplitude, frequency and waveform used.
2# continuous casting machine crystallizer vibration device
Fig.1 Sketch map of the mould oacillator
As can be seen from Figure 1, the crystallizer vibration device consists of 4 parts: crystallizer support platform, moving parts, rolling elements, and vibration hydraulic cylinder. The mold support is a heavy-duty device mounted on the base frame of the mold. The moving parts are installed on the upper part of the crystallizer support platform, and the two are directly connected through hydraulic cylinders and rolling elements. The rolling elements are used to guide the movement of the crystallizer so that the crystallizer only moves vertically, with an accuracy of up to 0.03mm.
The characteristics of this device are as follows
1) This device is directly driven by dual hydraulic cylinders, without resonant springs. It has a simple structure, few parts, and is easy to maintain. It can generate more waveforms, and the waveform, amplitude, and frequency can be adjusted at any time.
2) Since the rolling elements avoid fatigue failure that is common in springs, they almost eliminate any wear and tear in the system when the guiding moving parts move, greatly increasing the working life of the system.
Common faults and solutions
The two cylinders are out of sync
The vibration of the crystallizer of the 2# continuous casting machine achieves synchronous movement through two hydraulic cylinders.
1. Cause of failure
1) The vibration starting position of the hydraulic cylinder is offset; 2) The servo valve has zero drift; 3) The hydraulic cylinder always moves near the neutral position, causing wear at this position; 4) The position sensor fails. When the position sensor fails, you can use the computer to In the monitoring system (FDA), check the vibration waveform, and the fault waveform is shown in Figure 2.
2.Solution
1) Calibrate the vibration starting position of the oil cylinder: Lift the crystallizer, move the hydraulic cylinder to the maximum position, and reset the sensor;
2) Increase the zero bias current, or manually adjust the valve core to return it to the zero position;
3) Replace the hydraulic cylinder and repair it offline;
4) Replace the sensor.
The crystallizer swings along the direction of the casting stream
The crystallizer and vibration device of the 2# continuous casting machine are connected by rolling elements and hydraulic cylinders. The function of the rolling elements is to make the crystallizer only move vertically, and its vertical movement accuracy can reach 0.03mm.
1. Cause of failure
1) The rolling elements are worn and cannot maintain their accuracy;
2) The hydraulic cylinder connector is worn;
3) The connecting bolt between the hydraulic cylinder and the vibration device is loose.
2. Solution
1) If the deviation is within the range of 0.5mm, adjust the rolling element wedge. If the deviation is greater than 0.5mm, the rolling element needs to be replaced;
2) The hydraulic cylinder connector cannot be replaced online, only the hydraulic cylinder can be replaced;
3) Tighten the bolts.
Vibration waveforms do not overlap
The vibration status of the crystallizer can be checked through the computer monitoring system (FDA) to check the vibration waveform.
1. Cause of failure
1) The servo valve has a large center wear. The valve is always moving at high frequency and large stroke, and is easily worn, which leads to a reduction in the response performance of the valve. The servo valve center wear fault waveform is shown in Figure 3. After wear, the valve Zero leakage occurs, resulting in an increase in zero current and jitter at the peak of the vibration waveform. In severe cases, the entire curve jitters.
2) The leakage in the hydraulic cylinder is large. Since the hydraulic cylinder is always in the middle position and moves at high frequencies, it is easily worn, resulting in large leakage in the middle position and causing the two hydraulic cylinders to be out of sync.
2. Solution
1) Replace the servo valve;
2) Replace the hydraulic cylinder or change the starting position of the hydraulic cylinder.
The middle position of the crystallizer vibration table is unstable.
When the crystallizer vibration table stops in the neutral position, its position waveform should be a straight line. After using the 2# continuous casting machine for nearly 2 years, it appears that when the crystallizer vibration table stops in the neutral position, its position waveform is a curve, which means vibration The platform is unstable in the middle position.
1. Cause of failure
1) The servo valve has large wear in the middle position. When the servo valve is in the middle position, the internal leakage is large;
2) The leakage of the hydraulic cylinder in the neutral position is large, causing the hydraulic cylinder to stop unstable in the neutral position, so the position sensor always feeds back signals to the servo valve to make its valve core move.
2. Solution
1) Replace the servo valve;
2) Replace the hydraulic cylinder or change the starting position of the hydraulic cylinder.
Conclusion
The vibration fault of the continuous casting mold is reflected in the intertwining of mechanical, electrical and hydraulic information. The relevant parameters recorded by the on-site computer (servo valve control signal, position waveform, pressure waveform, etc.) are important information for fault diagnosis. Since the metallurgical equipment is in a high-temperature environment, And it needs to run continuously, which is closely related to the formation of its fault.
