JP2004136368A - Vibration detector for casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a casting mold vibration detector used in realizing a continuous casting method which prevents manufacturing of a cast billet containing such conventional and occasional abnormalities as streaks or transverse cracks and which enables preventive maintenance of the equipment to be properly carried out. <P>SOLUTION: The detector is equipped with a flat plate mounted on the outer face of a casting mold and a position sensor for sensing positional change in the flat plate. The positional change of the flat plate is caused by vibration of the casting mold in the direction orthogonal to the withdrawing direction of a cast billet in the casting mold. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a mold vibration detecting device, and more particularly to a mold vibration detecting device used when continuously casting various cast pieces such as billets, blooms, and slabs.

It is common practice to manufacture various cast pieces such as billets, blooms and slabs by a continuous casting method. In this continuous casting, powder is added to the molten metal surface in a mold, and the cast pieces are drawn. As a result, the powder is introduced between the mold and the slab to reduce the frictional resistance between the mold and the slab. In addition, the mold is vibrated in a direction parallel to the slab withdrawing direction to achieve smooth drawing.

As described above, the vibration of the mold acts only in the direction parallel to the slab withdrawal direction (hereinafter, sometimes referred to as the “drawing direction”). In some cases, the vibration also occurs (hereinafter, may be referred to as a lateral direction). This lateral run-out becomes progressively worse as the casting equipment deteriorates, which causes an abnormal flow of powder between the mold and the slab, and an abnormal load is applied from the mold to the slab, resulting in the inside of the mold. Phenomena such as affecting the coagulation reaction that is proceeding occur. As a result, there is a high possibility that streak defects (dent defects on the slab surface caused by uneven flow of powder) and lateral cracking defects due to the fracture of the crystal structure during solidification due to external force occur on the slab surface. And quality problems arise.

However, in the related art, even if the above-mentioned abnormal situation occurs, the casting operation is continuously performed without noticing it, and it has been difficult to always produce a high quality product stably. For this reason, there has been a need for an operation of detecting quality defects occurring in the cast slab after casting by inspection in a post-process and selecting good products.

Therefore, the present invention has been made in view of the above situation, and prevents the production of cast slabs of abnormal quality beforehand, and also performs preventive maintenance of equipment for stabilizing lateral vibration of a mold at a low level. It is an object of the present invention to provide a mold vibration detection device used when executing a continuous casting method capable of appropriately executing the method.

The mold vibration detecting device according to the present invention is a mold vibration detecting device capable of measuring the amount of mold vibration in a direction orthogonal to the slab withdrawal direction during non-casting and during casting, and is attached to the outer surface of the mold. The gist comprises a flat plate and a position sensor for detecting a change in the position of the flat plate based on the vibration of the mold in a direction orthogonal to the direction of drawing the slab of the mold.

For example, the position sensor (for example, an eddy current sensor) is installed on a mount or the like (fixed) that is isolated from the vibration of the mold, and the fluctuation state of the distance from the sensor to the flat plate (for example, a metal flat plate) is measured. The vibration amount of the mold in the lateral direction is measured.

次 The following continuous casting method can be executed by using the mold vibration detecting device according to the present invention. In the continuous casting method, during non-casting and / or during casting, the amount of vibration of the mold in a direction perpendicular to the direction of slab withdrawal is measured, and a comparison with a preset reference value is performed to determine whether or not casting is appropriate. It is to be.

The present inventors have examined problems such as lateral cracks and streak defects near the slab surface, and have found that the cause of the problem is the lateral deflection of the mold as described above. In the conventional continuous casting method, the state of the lateral run-out of the mold is not monitored or the degree of the lateral run-out is not measured. Therefore, it is difficult to obtain a high quality product stably. It is thought that there was.

As described above, the amount of mold vibration in the direction (lateral direction) perpendicular to the slab withdrawal direction, that is, the amount of mold vibration related to lateral runout, is measured. If this vibration amount is larger than a predetermined reference value, the component replacement of the continuous casting apparatus is performed. It is advisable to perform preventive maintenance such as core adjustment of the casting line or the like, thereby stably controlling the vibration amount to a low level, and thus performing continuous casting with the horizontal vibration amount always small. High quality slabs can be stably manufactured.

The “non-casting time” refers to a state in which there is no slab (molten metal and its solidified body) in the mold (empty state) before starting casting or after completion of casting, The above-mentioned “during casting” refers to a state where there is a slab in the mold and casting is being performed.

{Circle around (4)} The “vibration amount” refers to the range of fluctuation of the vibrational displacement, that is, the distance from the peak to the valley when the vibration of the mold is represented by a graph.

Then, the mold vibration amount in a direction perpendicular to the slab drawing direction, and the mold vibration amount in a direction parallel to the slab drawing direction were measured, and these measured values were set so as to satisfy the following expression (1). Preferably, continuous casting is performed.
W ₁ / W ₀ ≦ 0.1… (1)
W ₁ : Maximum value of the vibration amount of the mold in the direction perpendicular to the slab drawing direction (μm)
W ₀ : Set value (μm) of the vibration amount of the mold in a direction parallel to the slab drawing direction

If W ₁ / W ₀ is more than 0.1, it is determined that the lateral run-out of the mold is too large, so that the powder inflow tends to be less favorable, and abnormal lateral load from the mold during casting. Since it is estimated that is added to the cast slab, maintenance of the continuous casting apparatus is performed to satisfy the above-mentioned expression (1). Thereby, occurrence of quality abnormality of the slab can be prevented beforehand, and the maintenance of the equipment can be appropriately performed. In particular, in steel types in which streak defects are easily generated (for example, steel types containing 0.10% of carbon) and in steel types in which lateral cracking defects are easily generated (for example, steel types containing 0.10 to 0.20% of carbon), It is desirable to satisfy the above equation (1).

More preferably, the ratio W ₁ / W ₀ is 0.08 or less, still more preferably 0.07 or less.

The “set value (W ₀ ) of the mold vibration amount in the direction parallel to the slab withdrawal direction” is a set value when a vibration is applied to the mold in the drawing direction.

Further, as a continuous casting method, during non-casting and during casting, measure the amount of mold vibration in the direction perpendicular to the slab withdrawal direction, and during non-casting, the amount of mold vibration in the direction perpendicular to the slab withdrawal direction, It is possible to compare the amount of vibration of the mold in a direction orthogonal to the direction of drawing the slab during casting and compare the amount of change with a predetermined reference value to determine whether or not the casting is appropriate.

For example, the horizontal vibration amount when the slab exists in the mold (during casting) is smaller than the horizontal vibration amount when there is no slab in the mold (during casting). In this case, it means that the slab receives a load in the lateral direction by an amount corresponding to the difference (amount of change). If the amount of change is large, there is an increased concern that a slab may have a lateral crack defect. Conversely, if the amount of lateral vibration during casting is a large value compared to the amount of lateral vibration during non-casting, the arrangement of the molds and rolls in the continuous casting machine will shift, and the core of the casting line will be misaligned. May not come out with high accuracy, and in this case also, an abnormal force acts on the slab in the mold, and there is a possibility that a crack defect or a streak defect may occur. If the amount of change is large as described above, there is a high possibility that a defective slab is manufactured. Therefore, it is preferable to perform maintenance or the like of the continuous casting apparatus so as to reduce the amount of change.

Furthermore, the absolute value of the difference between the mold vibration amount in the direction orthogonal to the slab withdrawal direction during non-casting and the mold vibration amount in the direction orthogonal to the slab withdrawal direction during casting is 0.1 mm or less. Preferably, there is.

As described above, if the difference (change amount) between the lateral vibration amount during non-casting and during casting is 0.1 mm or less in absolute value, there is little concern that the above-described problems will occur, and a good cast piece can be obtained. It can be manufactured stably. In particular, as a steel type, a steel type in which streak defects are easily generated (for example, a steel type containing 0.10% of carbon) and a steel type in which lateral cracking defects are easily generated (for example, a steel type containing 0.10 to 0.20% of carbon) In this case, when the absolute value of the variation is 0.1 mm or less, the effect of preventing defects is high.

More preferably, the absolute value of the difference between the lateral vibration amount during non-casting and during casting is 0.08 mm or less. More preferably, it is 0.05 mm or less.

As in the continuous casting method described above, the lateral vibration of the mold is monitored. For example, if the lateral vibration is large, streak defects and lateral vibration can be obtained by performing maintenance such as replacing parts of the equipment or adjusting the core of the casting line. It is possible to prevent the occurrence of defective products such as crack defects, and to constantly and stably produce high quality cast slabs. In addition, preventive maintenance of equipment can be appropriately performed before a large equipment abnormality occurs.

According to the mold vibration detecting device of the present invention, the lateral vibration of the mold can be accurately detected, and the continuous casting method can be easily performed.

FIG. 1 is a schematic view showing an example of a continuous casting apparatus provided with the mold vibration detecting device of the present invention, in which (a) is a longitudinal sectional view and (b) is a view of the mold 14 as viewed from above. 2 and 3 are enlarged sectional views showing the vicinity of a mold of the continuous casting apparatus. FIG. 2 shows a case where a good cast piece is manufactured, and FIG. Is shown.

(4) The molten metal 13 injected into the mold 14 from the immersion nozzle (not shown) gradually solidifies from the surface (contact surface with the mold) while being drawn downward (solidified shell 12). Powder 11 is added to the molten metal surface of the molten metal 13, and the powder 11 enters between the mold 14 and the slab (solidified shell 12) so as to cover the surface of the solidified shell 12 with the above-mentioned drawing, thereby reducing frictional resistance. Reduce. At this time, vibration is applied to the mold 14 in the drawing direction (Z-axis direction), and the slab is easily drawn. In the present specification, the molten metal 13 and the solidified shell 12 may be collectively referred to as a slab.

A metal plate 17 is attached to the outer surface of the mold 14 of the continuous casting apparatus (in practice, it is preferable to attach the metal plate 17 to an iron frame around the mold). Also vibrate. An eddy current sensor 18 is installed facing the metal plate 17, and the eddy current sensor 18 is mounted on a fixed base (not shown) and does not move. The metal plate 17 and the eddy current sensor 18 constitute a mold vibration detecting device 16.

The eddy current sensor 18 measures the distance from the metal plate 17 and thereby measures the amount of vibration of the metal plate 17 in the horizontal direction, that is, the amount of vibration of the mold 14 in the horizontal direction. The upper left eddy current sensor 18 shown in FIG. 1B senses vibration in the X-axis direction, and the lower left eddy current sensor 18 shown in FIG. 1B senses vibration in the Y-axis direction. Here, the X-axis direction is one direction orthogonal to the drawing direction (Z-axis direction), and the Y-axis direction is a direction orthogonal to the X-axis direction and the Z-axis direction. The lateral shake is the shake in the X-axis direction, the shake in the Y-axis direction, or the shake in which the X-axis direction and the Y-axis direction are combined.

When performing continuous casting, the mold vibration detecting device 16 is used to monitor the state of the mold run-out during casting or before casting (at the time of non-casting), and compare it with a preset reference value to determine the lateral direction. If the amount of vibration of the mold is large, parts are exchanged in the continuous casting apparatus, the core of the casting line is adjusted, etc., and the casting is always performed with a small horizontal runout. As a result, it is possible to prevent inferior quality of the slab caused by the mold runout.

(3) If the lateral run-out of the mold is large, the inflow of the powder 11 becomes non-uniform as shown in FIG. 3 and the possibility of causing streak defects in the solidified shell increases. In addition, an abnormal load is applied from the mold 14 to the solidified shell 12, and the possibility that the crack defect 15 is generated increases.

On the other hand, when the lateral runout of the mold 14 is small, the powder 11 flows in uniformly and well, and a sound solidified shell is formed (FIG. 2).

The method according to the present invention is particularly effective in a near net shape type continuous casting machine (a billet continuous casting machine, a thin slab continuous casting machine, etc.) in which defects in the casting stage are likely to remain in the product.

<Experiment 1>
Continuous casting was carried out using the following steel types a and b, the vibration amount of the mold in the horizontal direction at that time was measured, and it was observed whether or not the resulting steel had a streak defect. The amount of vibration (set value) in the drawing direction (Z-axis direction) imparted to the mold during this continuous casting is 3000 μm (W ₀ ).
Steel type a: C = 0.10%, Si = 0.02%, Mn = 0.43%, S = 0.030%, balance steel type b: C = 0.10%, Si = 0.02%, Mn = 0.43%, S = 0.008%, balance iron

FIG. 4 is a graph showing the relationship between the probability that streak defects do not occur (the streak defect non-occurrence rate (%)) and the lateral mold vibration amount. As can be seen from FIG. 4, the smaller the vibration amount of the mold in the horizontal direction, the less streak defects occur, and the larger the vibration amount of the mold in the horizontal direction, the more streak defects tend to occur. It is generally within the area between the two solid lines shown in the graph). Therefore, it can be seen that reducing the vibration amount of the mold in the lateral direction is effective for reducing streak defects.

Since W ₀ is 3000 μm as described above, the above equation (1) is satisfied when the lateral vibration amount of the mold is 300 μm or less, but as shown in FIG. 4, the lateral vibration amount is 230 μm or less. No streak defects occurred much.

<Experiment 2>
Continuous casting was performed using a billet continuous casting apparatus (strand Nos. 1 and 2), and the amount of vibration of the mold in the horizontal direction before casting (when not casting) and during casting was measured. The results are shown in FIGS. The amount of vibration applied to the strands Nos. 1 and 2 in the drawing direction, that is, the set value W _{0 of the} amount of vibration of the mold in the drawing direction is 3000 μm. The values shown in the graphs of FIGS. 5 and 6 are the average value of the lateral mold vibration amount during casting, and the average value of the lateral mold vibration amount when the mold is vibrated in the drawing direction before casting, respectively. It is shown in units of a cast (a series of continuous casting operations). The average value of the lateral mold vibration amount is an average of the values obtained by reading the signal of the eddy current sensor (position sensor) every 0.1 sec.

FIGS. 7 and 8 show graphs of values (changes) obtained by subtracting the lateral mold vibration during casting from the lateral mold vibration before casting. The results of strand No. 1 are shown in FIGS. 5 and 7, and the results of strand No. 2 are shown in FIGS.

If the lateral runout is large as described above, there is a high possibility that a crack defect or a streak defect will occur in the slab.However, as described above, by measuring the lateral mold vibration amount and managing the tendency, the mold lateral It is possible to grasp the state of deterioration such as wear of important parts that affect shaking (for example, the guide rail of the mold vibrating device, the rotating shaft, etc.), and to perform maintenance such as replacement of these parts at the appropriate timing in a preventive manner. It is possible to stably produce a slab without defects.

For example, in the case of the strand No. 1, the part A was replaced before the cast No. 7, and thereafter, the amount of change in the lateral run-out before and during the casting was small (FIG. 7). The value was 50 μm or less, and a slab of good quality was obtained stably. Also, after the replacement of the part A, the amount of vibration of the mold in the horizontal direction before and during casting was reduced (FIG. 5). Even before the replacement of the part A (cast Nos. ₁ to 6), W ₁ / W ₀ was about 0.07 at the maximum, and the cast slab was generally excellently manufactured. Thereafter, W ₁ / W ₀ is about 0.06 at the maximum, and a cast of high quality can be obtained more stably.

In the case of the strand No. 2, the part A was replaced before the cast No. 17, so that the rolling before casting became smaller after that (Fig. 6), and the variation of the rolling before and after casting. (Fig. 8), and a high quality cast slab can be obtained stably.

予 防 Early preventive maintenance is effective even when equipment maintenance is planned.

If the equipment is in a defective state, an accident may occur in which a large level of mold runout occurs suddenly.If such an accident occurs, the casting is stopped and a large-scale Equipment needs to be repaired. In this regard, the sudden accident can be prevented by monitoring the state of the lateral run-out as described above, detecting the deterioration and abnormality of the equipment at an early stage, and performing maintenance. As described above, it is effective from the viewpoint of systematically carrying out equipment maintenance, so that it is possible to stably obtain a good quality product without hindering a production plan.

In addition to measuring the lateral runout only during non-casting or only during casting, by monitoring the amount of lateral runout during non-casting and during casting, equipment abnormality management can be performed with higher accuracy.

For example, as can be seen from FIG. 6, the amount of vibration of the mold in the horizontal direction in the strand No. 2 is gradually increasing, but as shown in FIG. Indicates no value. As can be seen, by evaluating based on the amount of change (FIG. 8), the value of W ₁ / W ₀ (calculated from the amount of vibration in the lateral direction mold) due to equipment deterioration and the like is not affected by the temporal change. In addition, it is possible to accurately extract and evaluate only the influence of the external force applied from the mold to the slab during casting, and to stably produce a higher quality slab.

As described above, the mold vibration detection device according to the present invention has been specifically described with reference to the drawings showing examples. However, the present invention is not limited to the above-described examples, and may be adapted to the above-described purpose. The present invention can be implemented with appropriate modifications within the scope, and all of them are included in the technical scope of the present invention.

It is a figure which shows an example of the continuous casting apparatus provided with the mold vibration detection apparatus which concerns on this invention. It is an expanded sectional view showing the vicinity of a casting mold of a continuous casting device when a cast piece is in a normal state. It is an expanded sectional view showing the neighborhood of a casting mold of a continuous casting device when an abnormality occurs in a cast piece. 4 is a graph showing a relationship between a mold vibration amount and a streak defect non-occurrence rate. 6 is a graph showing the amount of vibration of the mold in the horizontal direction in strand No. 1. 9 is a graph showing the amount of vibration of the mold in the horizontal direction in strand No. 2. 6 is a graph showing the amount of change in the amount of vibration of the mold in the horizontal direction in strand No. 1. 9 is a graph showing a change amount of a mold vibration amount in a horizontal direction in a strand No. 2;

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 11 Powder 12 Solidified shell 13 Molten metal 14 Mold 15 Crack defect 16 Mold vibration detection device 17 Metal plate 18 Eddy current sensor

Claims (1)

During non-casting and during casting, a mold vibration detection device capable of measuring the amount of mold vibration in a direction orthogonal to the slab withdrawal direction,
A mold vibration detecting device comprising: a flat plate attached to an outer surface of a mold; and a position sensor for detecting a change in position of the flat plate based on the vibration of the mold in the mold in a direction orthogonal to the slab drawing direction. .

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