Development of Wire Rod Mill

    At present, Asia is the fastest-growing economy in the world. However, China is the focus of Asia. Under such a rapid development situation, China's infrastructure has developed rapidly, and various types of wires have been in short supply. The original old-fashioned horizontal rolling mill and double-rolling mill are far from meeting the needs of today's market development in terms of accuracy and quality, as well as in terms of output and control level.

    Therefore, in the late 1960s, with the continuous improvement of the technical level, various new types of high-speed twistless finishing mills were developed in the world, and the wire weight was increased from tens of kilograms to two and a half tons. The final exit speed of the rolling is increased from the original 20m/s to 30m/s to the current 130m/s, and the finished product tolerance is ±011mm.

Due to the smooth surface quality of the wire, the head-to-tail tolerance value is small, and the metallographic structure is more uniform after the water-cooling and the loose-rolling control are cooled, so that the wire can be drawn without heat treatment, thereby greatly reducing the cost and receiving a large number of users. Praise and welcome.

At present, representative finishing mills include internal drive 45-degree wire rod mill, external mesh drive 45-degree finishing mill, X type 45 degree centralized drive finishing mill, Y type three-roll finishing mill, flat roll drive finishing mill, 75 degrees. ×15 degree concentrated transmission finishing mill six types.

Compared with the old-fashioned rolling mill, these rolling mills have the following characteristics:
1. Single-line continuous rolling, convenient and safe operation;
2. High rolling speed, currently up to 130m/s;
3. Convenient for changing rolls;
4. Convenient for changing guides;
5. High, low cost;
6. Wire rod tolerance is small, the surface is smooth;
7. Wire rod has high internal quality;
8. High level of automation control.

In recent years, China's wire rod mill equipment has developed very rapidly.

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Automatic Control Analysis of Bar Continuous Rolling Flying Shear

Flying Shear Start Control

Before rolling, the engineer's station personnel passed the screen set to transfer the cut and cut the size of the flying shear to the PLC. When the HMD detects the steelhead or steel tail signal before the shear, the detection signal is sent to the PLC that controls the scissors, and the scissors PLC then according to the line speed of the rolling piece passed by the basic PLC, the last cut of the scissors The error, and the set length of the cutting head and the tail length, calculate the flying shear start delay time. When the delay time is up, the start command of the flying shear is issued immediately, and the cutting function of the flying shear is completed. For the shredding function of the scissors, the manual start control is adopted, and the operation table manually breaks according to the accident. The shredding function of the scissors takes precedence over the function of cutting and cutting.

Rolling Steel Simulation Analysis Function

When the hot test run is not set at the production site, in order to comprehensively evaluate the linkage effect of each device, it can be completed by cold adjustment; when it is judged whether the cascade blocking function is normal, it can be analyzed by the automatic control model; When it is reasonable, it can be operated in a targeted manner, which shortens the trial hot car time to some extent. At the same time, under the action of rolling steel simulation analysis function, online simulation analysis is realized, and through the continuous improvement of offline simulation function, it provides necessary reference information for the development of transmission inverter equipment program. When the PLC is connected correctly, all module performance can be tested in real-time.

Bar Speed Correction

The rolling speed of the bar is the basis for control and the key to controlling the accuracy of the cutting, so the estimation of the speed of the rolled bar is particularly important. When the calibration function is activated, the speed of the bar is corrected. The speed of the rolled material is generally calculated by the mill control system based on the roll diameter, roll profile and motor type, due to elastic strain and rolled material at the stand roll. The actual reduction on the amount, the calculated value may not be consistent with the actual value. The actual speed is estimated by measuring the elapsed time of the end of the bar from the HMD before the flying shear to the time after the HMD. Alternatively, the flying shear performs shearing, and the measurement starts from the interlacing of the blade to the cutting. The time at which the end reaches the HMD downstream of the flying shear. The ratio of the distance between the HMDs and the measured time gives an estimate of the average speed of a bar during operation. A speed calibration factor is obtained relative to the average of the speeds calculated by the mill control system at the same interval. The speed received from the mill control system becomes a speed calibration factor, thereby obtaining the best estimate of the actual speed of the bar during shearing.

Flying shear Zero Compensation Control

After the end of a cutting process, the flying shear must be accurately parked at the zero position to prepare for the next cut. The zero detection of the flying shear is calibrated by the proximity switch. However, in practice, there is a certain error in the stop position from the original zero points. The error must be compensated to ensure that the speed of the scissors is accelerated to the set shear speed within the specified distance to meet the shear torque requirement. For this purpose, the position of the cutting edge is detected using the positioning code dial. The code wheel adopts 2048 two-phase orthogonal pulse. Each rotation of one wheel, the code wheel count is 0-8192, corresponding to the cutting edge angle of 0-360 degrees so that the angle of the scissors from the zero position can be calculated by counting the pulse of the code wheel. By this value and the angle between the zero point and the shear point, the initial angle of the flying shear can be calculated. Since the code wheel can achieve high precision and can effectively suppress the counting error caused by the vibration, the next cutting edge can be accurately compensated for the next cutting edge error.

In summary, the application of the bar shear system, the main technical performance indicators such as shear accuracy, shear section quality, shear response speed and optimized shear reliability can meet the on-site process requirements, in the rolling mill room Under the premise of normal cascading relationship, stable rolling mill speed and normal operation of all detecting components, the absolute value of the positive and negative shear length of the shearing length generally does not exceed the maximum linear velocity (m/s) of the rolling line multiplied by 5 milliseconds. The application of the automation control system has improved the production level to a certain extent, which is an inevitable trend in future development.

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