KR20000045505A - Method for measuring final point of solidification using pinch roll displacement during continuous casting - Google Patents

Abstract

PURPOSE: A method is provided to effectively predict the position of final point of solidification by monitoring displacement of a pinch roll by on-line in continuous casting. CONSTITUTION: In continuous casting, a tool for measuring the displacement of a pinch roll in casting process is installed in a frame of a continuous casting device stand and a pinch roll. By using the tool, the displacement(20) of a pinch roll caused by an iron static pressure of molten metal is measured and the final point of solidification of a cast piece is measured. Thereby, the final point of solidification is measured by using the displacement of the pinch roll in continuous casting.

Description

Measurement method of end point of solidification using pinch roll displacement during continuous casting

The present invention relates to a method for measuring the end of solidification by measuring the displacement of the pinch roll online during continuous casting, and to predict the internal quality (center crack, center segregation, etc.) of the cast through the measurement of the end of solidification In addition to providing an important means to prevent this, this method can be applied to soft reduction and high speed casting to achieve efficient facility management and optimization of operating conditions. It relates to a point measuring method.

Currently, methods for predicting the end point of solidification online during continuous casting operations include electromagnetic ultrasonic waves, strain gauges, guide roll displacement measurements, and load cells. In the case of the ultrasonic method, the thickness of the solidification cell can be measured directly, while the speed of the ultrasonic wave varies depending on the slab temperature, and the end point of solidification can be predicted theoretically based on the solidification rate model at the end of solidification. There is a downside to falling. Strain gauge method is a method of predicting the end of solidification by measuring the deformation of the player frame, which can be used as a maintenance tool for diagnosing the condition of the player segment, but it is possible to measure the behavior of individual rolls. There is a drawback that the diagnosis cannot be made and therefore the accuracy in end point of coagulation is also low. When the guide roll displacement and load sensor are used, the end point of solidification can be predicted by measuring the displacement or load of individual rolls according to the static pressure, but it is difficult to predict the end point of solidification when the roll gap is smaller than the slab thickness. In addition, in the case of the load sensor, when installed in the bearing block of the roll also has the disadvantage that must always be replaced when replacing the roll.

The present invention has been studied in this background. By monitoring online the displacement of the pinch roll during continuous casting, it is possible to diagnose the rolling state of the cast steel derived from the relationship between the roll gap and the slab thickness, as well as to measure the guide roll displacement and Unlike the method using the load sensor, it is possible to effectively predict the position of the end point of solidification by monitoring the displacement of the pinch roll that moves according to the change of the iron static force of unsolidified molten steel in the part even under the condition that the rolling force is applied to the cast. Has its purpose.

1 is a block diagram of a pinch roll displacement measuring means used in the present invention;

Figure 2 is a conceptual diagram illustrating the pinch roll displacement according to the change of the iron tension during casting,

3 and 4 are graphs showing the correlation between the end point of solidification and the pinch roll displacement under various casting conditions such as casting speed, steel grade, degree of cooling, and the like.

Explanation of symbols on the main parts of the drawings

1: lower unit 2: upper unit 3: connection part

4 sensor holder 5 displacement sensor 6 sensor target

7: spring 8: air inlet 9: air outlet

10 reference frame 11 drive roll stand 12 target axis

13: pinch roll 15: stand 16: entrance roll

17: exit roll 18: molten steel 19: displacement of the pinch roll when solidification is completed

20: displacement of pinch roll in the presence of unsolidified molten steel

As a technical configuration for achieving the above object, the present invention is to install the pinch roll displacement measuring means in the girder on which the standard stand and pinch roll of the continuous casting machine is seated, through which the iron static pressure of unsolidified molten steel during continuous casting By measuring the displacement of the pinch roll generated by the on-line predicting end point of solidification online, it provides a method that can be applied to the optimization of the operation and equipment conditions.

Hereinafter, with reference to the accompanying drawings the present invention will be described in more detail.

Fig. 1 schematically shows the configuration of the pinch roll displacement measuring means usable in the present invention. The sensor 5 is installed upside down inside the upper unit 2 to indirectly measure the pinch roll movement and to prevent foreign matter from accumulating between the sensor 5 and the sensor holder 4. Inside the lower unit 1, a target 6 is installed in which the position is sensed by the sensor 5. The size of the target 6 was manufactured in an appropriate size not to exceed the sensing range in consideration of the movement in the casting direction of the pinch roll during casting and the zigzag movement when the roll was opened and closed during non-casting. Here, it is important to keep the target 6 horizontal during measurement since the sensor 5 may not be located at the center of the target 6. Therefore, the shaft 12 supporting the target 6 was manufactured so that the shankdong smoothly while casting, while the target 6 was kept horizontal. Since the cylinder stroke at the time of pinch roll opening and closing is much larger than the casting gap or the measuring range of the sensor, the pinch is provided by installing the spring 7 on the target shaft 12 to protect the sensor 5 and to allow a large stroke. The spring 7 is designed to operate when the roll movement exceeds the measuring range. At this time, when the spring 7 moves during casting, the reliability of the measurement data drops sharply, so that the elastic modulus of the spring 7 is increased so that the spring 7 is operated only when the pinch roll movement exceeds the measurement range. . In addition, in order to prevent thermal expansion of the system, to protect the displacement sensor, and to maintain the durability of the system, an on-site air line is connected to the air inlet 8 and the air outlet 9 to purge the inside of the device for 24 hours. It was designed to be controlled by needle valve, and it was manufactured to install the air gauge separately to adjust the pressure state inside the device optimally. The connecting portion 3 is a part connecting the upper unit 2 and the lower unit 1 as described above, and is much lower than the casting direction movement of the punch roll during casting, roll opening, zigzag movement during closing, and casting gap. The bellows was manufactured to allow a large cylinder stroke, and the silicone rubber was coated on the bellows surface to prevent deterioration due to prolonged use. 1, reference numeral 10 denotes a reference frame, and 11 denotes a driving roll stand.

Fig. 2 is a conceptual diagram showing the displacement of the pinch rolls 16 and 17 moving according to the iron static force of the unsolidified molten steel 18 in the cast steel, where 19 is the pinch roll displacement when solidification has already been completed, and 20 is Pinch roll displacement when unsolidified molten steel is present.

Specifically, cracks or central segregation may occur in cast pieces due to abnormal casting conditions such as the alignment of equipment near the end of solidification during continuous casting. In the case of soft reduction, not only the end point of coagulation should be adjusted to exist in the pressing section, but also the end point of coagulation is essential from the viewpoint of equipment limitation and productivity in high speed casting. Due to the large thickness of the cast sheet, the rolling resistance may be excessively increased as well as the rolling force on the guide roll.In this case, the rolling resistance is applied even after the solidification is completed due to the rolling resistance, and the roll displacement is reduced at all. Since it is not possible to predict the end point of solidification by means of the load sensor and guide roll displacement measurement. However, in the case of the pinch rolls 16 and 17, the pinch rolls 16 and 17 can move freely up and down by the bulging force of the cast steel according to the casting conditions. Since is changed, it is possible to effectively measure the end point of solidification regardless of the presence or absence of rolling force.

Hereinafter, embodiments of the present invention will be described.

Example 1

Fig. 3 shows left and right displacements of the # 2 entry pinch roll 16: m1 and the exit pinch roll 17: m2 according to the casting speed. As the casting speed increases around 7600 seconds, the end point of solidification moves forward, thus reducing the m2 (outlet roll) displacement. It is interesting to note that the displacement of the roll increases slightly for m1 (side roll). This may be due to the fact that the molten steel near the end of the solidification pressed by m2 pushed up m1 as the end of the solidification approached the pinch roll. In the case of the second cast, the position during the casting of m2 and the point at which the casting ends are not significantly different. That is, the displacement of m2 before and after casting is not large. This means that solidification is almost complete near # 2 pinch roll. In the case of the third smoke, the second cooling is changed from strong to weak cooling near 62500 seconds, and the end point of solidification becomes long, and both the displacements of m1 and m2 become large. In conclusion, in the case of m1, it is difficult to predict the end of coagulation due to the interaction with m2, but in the case of m2, the displacement is increased when the end of coagulation is long, and the displacement is decreased when the end of coagulation is short. In other words, by monitoring the displacement of m2, the end point of solidification during casting can be predicted very effectively and easily.

Example 2

Figure 4 also shows the behavior of the # 2 pinch roll according to the casting conditions. In the case of the first soft-margin, m2 is significantly lowered, and m1 is relatively high. The displacement of m2 indicates that solidification is almost complete at this position, suggesting that the solidification is relatively fast by the addition of alloying elements. In the 2nd and 3rd rings, the solidification progressed less than the first, but the solidification point is still near the # 2 pinch roll. In the 4th performance, the main speed is 1.3m / min and the solidification completion point is quite long. The displacement of m2 is considerably large, and the relative force of m1 decreases the pushing force by m2 and is applied only by iron static pressure. The displacement is small during casting. This confirms that m2 increased as the solidification point was increased as described in Example 1, and once again, solidification completion point behavior by m2 monitoring during casting can be predicted.

As described in detail above, the present invention provides efficient facility management by accurately measuring the end point of the solidification of cast steel in continuous casting by a method of measuring and monitoring the displacement of the pinch roll causing the displacement due to the static pressure of molten steel during continuous casting. And the effect of optimizing the operating conditions.

Claims (1)

In continuous casting, a means for measuring the displacement of the pinch roll during the casting process is provided in the frame of the continuous casting machine stand and the pinch roll, and the displacement of the pinch roll caused by the iron static pressure of unsolidified molten steel during casting through the means. The method of measuring the end point of solidification using the pinch roll displacement during continuous casting, characterized in that to measure the end point of solidification of the cast.