Determination of the outer arc reference line of billet continuous casting machine

 In order to solve the problem of the permanent reference point loss of the external arc of the billet continuous casting machine on site, the arc radius of the continuous casting machine is used to determine the external arc reference line of the continuous casting machine.

Keywords: billet continuous casting machine; outer arc reference line; arc radius

Overview

When the continuous casting machine is installed, the permanent base points of the continuous casting machine will be retained on site. These permanent base points include the outer arc base point, the center point and the infrastructure elevation point. Basically, 3 to 4 center points will be reserved, distributed on the center line of the casting machine. Two reference points for the outer arc reference line will be reserved, distributed on both sides of the crystallizer vibration device. Generally, three to four permanent base points will be reserved for infrastructure elevation points on the pouring platform and the ground. These permanent base points can be used to calibrate the outer arc reference line, center line and elevation of the continuous casting machine to improve the equipment accuracy of the continuous casting machine.

Introduction to billet continuous casting machine

The No. 3 billet continuous caster of the steelmaking plant was put into operation in 2003. It adopts an arc continuous caster with an arc radius of 8m and a caster with 6 machines and 6 strands. The crystallizer vibration device is a double eccentric half-leaf spring 4-bar linkage mechanism, which is arranged on the inner arc side of the continuous casting machine, and the vibration curve is a sinusoidal curve. The vibration device mainly consists of a transmission device (composed of a motor, a reducer and an eccentric mechanism), a push rod, a half-leaf spring 4-bar linkage mechanism and a vibration table. In March 2014, the vibration mode of the crystallizer was transformed into a non-sinusoidal vibration mode of the electric cylinder. After the transformation, all parts of the vibration device were replaced. After the transformation, the transmission system of the vibration device was changed to a servo motor, guide screw and buffer spring device. The vibration frame, vibration frame mounting beam, transmission system fixed beam, and transmission system were all replaced and modified.

There are problems

During the site cleaning of the billet continuous caster during the renovation, it was found that its center point and elevation point were well preserved, but the permanent base point of the outer arc reference line was located on both sides of the first and sixth stream vibration devices (see Figure 1). There was a steel leakage accident in the tundish during production, causing the permanent base point to stick to the molten steel. It was damaged during the on-site cold steel cleaning and was cleaned up together with the cold steel. Therefore, there is no trace of the outer arc base point. Before the transformation, the vibration frame was installed in a suspended manner, suspended on the vibration frame mounting beam. Since the equipment has been in operation for nearly ten years, the vibration frame mounting beam has been deformed, and the vibration device has never been calibrated during this period. After the transformation, the vibration frame mounting beam will be replaced as a whole, and the original mounting beam will not be used. However, the outer arc reference point of the existing vibration frame is already deviated. How to determine the outer arc reference point has become the key to the transformation of the vibration system.

Determination of outer arc reference line

Since the outer arc reference point of the billet continuous casting machine has been lost, the accurate outer arc reference line cannot be found directly on site. The outer arc reference line can only be found and determined indirectly. The indirect search for the outer arc reference line requires accuracy.

Figure 1 On-site reference point distribution of continuous casting machine

Relevant technicians made a misunderstanding when they first looked for the outer arc reference line, and set the uppermost end of the mold copper tube near the outer arc as the outer arc reference line. After checking the drawings, I found that the upper end of the mold copper tube on the outer arc side is not above the outer arc reference line of the continuous casting machine. Because the billet continuous casting machine is an arc-shaped continuous casting machine, the copper tube of the mold is arc-shaped, and the intersection point of the copper tube in the direction of the horizontal center line of the mold is the outer arc reference line. That is to say, the distance between the upper end of the mold copper tube and the outer arc side and the outer arc reference line is still 15.64mm (see Figure 2).

Figure 2 Distribution of base line of outer arc of crystallizer

Due to the deviation of the crystallizer during hoisting, the position of the crystallizer will change slightly every time it is hoisted. It is difficult to determine the outer point of the copper tube. It can be seen that the use of the crystallizer copper tube to determine the outer arc baseline has a large deviation.

The standard for on-site installation is the arc radius of the continuous casting machine. The arc radius of the casting machine refers to the radius of curvature of the outer arc of the cast slab, that is, the distance from the outer arc reference line to the horizontal line of the cast slab outlet tension and straightening device. The method adopted is to use the existing vibration frame to initially determine the outer arc baseline, and then use the arc radius of the continuous casting machine to review the outer arc baseline to determine the outer arc baseline. The specific operation method is:

(1) Lift all the crystallizers on the vibration frame away from the site. Determine the center line of the casting machine and whether the position of each stream has changed based on the permanent base point of the center line of the continuous casting machine on site. First find out the center line of the entire casting machine, mark it on the vibration frame, and then use the flow spacing of the casting machine to confirm whether the position of each flow has changed and adjust the center of each flow.

(2) Initial determination of the outer arc baseline. Before the old frame is dismantled, the positions of the outer arc reference points on both sides of the casting machine are determined based on the outer arc marking points of the original vibration frames of the 1st and 6th streams. First hang the wire to make a fixed point on the outside of the 1st stream and 6th stream, temporarily serving as the outer arc reference point, and then use these two points to use the steel wire to make the outer arc reference line.

(3) Use theodolite to initially determine the outer arc reference line and the center of the casting machine

Is the line vertical? First use the three center points of the continuous casting machine to find the center line of the casting machine, and then use the theodolite to determine whether the outer arc reference line and the center line of the casting machine are perpendicular. If it is not vertical, you can make appropriate adjustments. The principle of adjustment is to offset the outer arc as much as possible.

(4) Final correction is made based on the arc of the casting machine, that is, the outer arc reference line and the horizontal radius of the cast slab after it exits the tension and straightening device. This size is fixed and is determined when designing the continuous casting machine. The design of the continuous casting machine is also designed based on this arc radius, so this size is reliable. The distance between the intermediate transition roller of the straightening roller and the outer arc reference line on the design drawing is 8508.3mm (see Figure 3).

Figure 3 The relationship between the outer arc reference line and the position of the tension leveler

The outer arc reference line can be calibrated based on this size.

Conclusion

The arc radius is an important parameter of the continuous casting machine. The size of the arc radius depends on the type of steel being poured and the cross-sectional size of the cast slab. The precise determination of the arc radius of the continuous casting machine also ensures the precise determination of the distance between the outer arc reference line and the tension leveling machine. This dimension is the basis for the design of the entire continuous casting machine and is fixed. The arc radius is used to verify that the distance between the outer arc reference line is accurate.

During the transformation of the billet machine, after the outer arc reference line was determined using this method, the molten steel port of each flow in the intermediate tank was well aligned and the equipment was operating normally.

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