KR101183420B1 - Hammering vibrator in continuous casting - Google Patents

Abstract

This invention is for preventing the segregation of a casting piece effectively, even if the casting piece has a large casting piece width.
When continuously casting the casting piece 1 having a rectangular cross section, the thickness direction of the casting piece 1 per casting length 1 m in a range in which the center solid phase ratio f _S of the casting piece thickness center portion is at least 0.1 to 0.9. While reducing the pressure continuously so that the rolling reduction ratio of is within 1%, and at least one of the central solid-state rates f _S is in the range of 0.1 to 0.9, the short sides of both sides of the casting piece 1 are opposed to each other. Is a device that strikes continuously in the casting piece width direction by using the mold 3 arranged between adjacent pairs of pinch rolls 2a and 2b at a vibration vibration frequency of 4 to 12 Hz and vibration energy of 30 to 150J. .
Even in a casting piece with a large casting piece width, it is possible to effectively prevent the occurrence of segregation such as center segregation and V segregation, and to obtain a casting piece having good internal quality.

Description

HAMMERING VIBRATOR IN CONTINUOUS CASTING}

In order to improve center segregation and the like, the present invention relates to a striking vibration device for imparting vibrations by striking the short sides of the casting pieces during continuous casting.

Macro segregation called center segregation and V segregation is easy to generate | occur | produce in the center part and thickness vicinity of the continuously cast casting piece. Hereinafter, this macro segregation is also called internal defect.

Among them, the central segregation is an internal defect in which solute components (hereinafter, also referred to as segregation components), which are easy to segregate, such as C, S, P, and Mn are concentrated on the final solidification portion of the cast piece. V segregation is an internal defect in which these segregation components are concentrated in a V-shape in the longitudinal section of the cast piece in the vicinity of the final solidification portion of the cast piece.

When the casting piece which generate | occur | produced these macro segregation was made into the product by hot working, the fall of toughness, hydrogen organic cracking, etc. will arise easily. In addition, when such a product is cold worked into a final product, cracks tend to occur.

By the way, the generation | occurrence | production mechanism of segregation in a casting piece is considered as follows.

That is, as the solidification progresses, the segregation component is concentrated between the columns of columnar crystals which are solidification structures. The molten steel enriched in this segregation component flows out of the stem of columnar crystals by shrinkage of the casting piece during solidification, or swelling of the casting piece called bulging. The thickened molten steel which flowed out flows toward the solidification completion point of a final solidification part, solidifies as it is, and becomes a thickening zone of a segregation component. The thickening zone of the segregation component formed in this way is segregation.

To prevent such segregation of the cast pieces, it is effective to prevent the movement of the molten steel in which the segregation components remaining between the columns of the columnar crystals are concentrated, and to prevent the localized accumulation of these thickened molten steels.

Therefore, during continuous casting, an air hammer is provided between the rolls arranged on the long side of the casting pieces, and 10 to 100 times per minute of vibration vibrations of an amplitude of about 2.0 mm or less is applied to the casting pieces moving between the rolls. The method is proposed by patent document 1.

[Patent Document 1: Japanese Patent Application Laid-Open No. 51-128631]

In addition, the applicant proposes, in Patent Document 2, a method of casting while applying a vibration to a casting piece when pressing down a position including an unsolidified portion of a casting piece having a rectangular cross section with a plurality of pressing guide roll pairs. have. This method strikes at least 1 part of the casting piece surface continuously in the range of a reduced area.

[Patent Document 2: Japanese Patent Application Laid-Open No. 2003-334641]

The method of this patent document 2 bulges the casting piece of the position containing an unsolidified part, and reduces this bulging casting piece with at least 1 pair of rolling roll pairs until solidification of a thickness direction center part is completed. It is a way. At that time, a method of casting while imparting vibration to the casting piece is also proposed. That is, in the range of the casting direction area | region from the start of bulging until the start of rolling reduction, or in the range of the reduction area | region in a casting direction, it is a method of hitting continuously at least 1 place of the casting piece surface.

However, in the method proposed by patent document 1, in order to fully exhibit the reduction effect of center segregation, there exist the following big problems.

Between rolls arrange | positioned at the long side side of a casting piece, a casting piece is easy to bulge. When striking vibration is provided to the long side of the bulging casting piece, a large amplitude cannot be provided to the center part of the thickness direction of a casting piece. Moreover, since it is necessary to install an air hammer between rolls, there exists a possibility that the spray arrangement | positioning for secondary cooling of casting pieces between rolls may be impaired. Therefore, continuous oscillation cannot be provided when the secondary cooling is appropriately attempted. In addition, it is difficult to propagate sufficient vibration energy to the casting piece with 10 to 100 blow vibrations per minute.

On the other hand, the method of patent document 2 is effective for preventing segregation of a casting piece. However, after that, the inventors continued to study, and it turned out that the segregation reduction may not be enough depending on the shape of the casting piece.

This is because, when the casting piece is hit from the short side, when the casting piece width is large, the impact vibration does not sufficiently propagate to the inside of the casting piece near the central portion in the width direction. In this case, since columnar crystals do not break during growth, columnar crystals grow and fine crystal structures cannot be produced. Further, vibration is not sufficiently transmitted to the equiaxed crystals generated near the final solidification portion in the width direction central portion, and the equiaxed crystals are easy to bridge.

Incidentally, the test conditions described in paragraphs 0039 to 0041 of Patent Document 2 (the vibration amplitude is ± 3.0 mm, the vibration frequency is 120 times / min (2 Hz), and the mold dimension is 200 mm x 100 mm x 400 mm (weight calculation value is 62.4 kg). In)), when the striking speed is 0.5 m / sec, the vibration energy is 7.8J.

The problem to be solved by the present invention is that, in the conventional blow performed from the short side surface of the casting piece during continuous casting, when the casting piece width is increased, it may not be possible to effectively prevent segregation such as center segregation or V segregation. .

The blow vibration device at the time of continuous casting of the present invention,

In order to prevent the segregation of the casting pieces effectively by giving a blow from the short side surface side of the casting pieces effectively even in the casting pieces having a large casting piece width,

When continuously casting a casting piece having a rectangular cross section, the rolling reduction rate in the thickness direction of the casting piece is 1% or less per length of the casting direction for 1 m in the range in which the center solid phase ratio f _S of the casting piece thickness center portion is at least 0.1 to 0.9. In addition to lowering the pressure continuously, and at least one of the central solid-state ratio f _S in the range of 0.1 to 0.9, the short vibration surfaces of both sides of the casting pieces oppose the vibration vibration frequency of 4 to 12 Hz and the vibration energy. Is a device that strikes continuously in the casting width direction at 30 to 150 J,

A mold hitting the short side of the casting piece,

A striking device for generating a periodic vibration and transmitting the vibration to the mold;

Has a striking positioning device for setting the interplanar distance between the mold and the short side of the casting piece,

The mold has a structure capable of collectively striking the cast piece short side surfaces between at least two neighboring pinch roll pairs of the light pressure zone composed of a plurality of pinch roll pairs.

The hitting positioning device sets the interval between the tip end surface of the mold and the casting piece short side at the return position of the mold after the detection of the pressing position on the casting piece short side of the mold, or the casting piece. The most important feature is that the impact positioning is performed while pressing the guide for setting the interval between the tip and the end face of the mold.

In addition, the center solid phase ratio of the f _S is, from the temperature T of the center of the liquidus temperature of the molten steel T _L and the solidus temperature T _S and the thickness, _S = f (T _L -T) / (T _L -T _S) You can get it. When the temperature T of the casting center convenience thickness less than the liquidus temperature T _L in the molten steel is f _S = 0, if the temperature T of the center of the thickness _S is less than the solidus temperature T of the molten steel is an _S f = 1.0. In addition, the temperature T of the thickness center of a casting piece can be calculated | required by the abnormal heat transfer analysis calculation of the casting piece thickness direction 1-dimensional considering the casting speed, the surface cooling of the casting piece, the physical property of the cast steel grade, etc.

According to the present invention, even in the case of a casting piece having a large casting piece width, generation of segregation such as center segregation and V segregation can be effectively prevented, and a casting piece having good internal quality can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the example of the pinch roll pair with a hitting apparatus in the short side surface direction of a casting piece.
Fig. 2 is a view explaining the positional relationship between the mold and the casting piece of the hitting device, (a) is a view showing the standby position of the hitting device, (b) is a view showing a state where the mold is pressed on the short side of the casting piece, (c) The figure which showed the state which returned predetermined | prescribed amount of metal molds from the position of (b) as a starting point.
3 is a view illustrating the positional relationship between the mold and the casting piece of another hitting device, (a) is a view showing the standby position of the hitting device, (b) is a view showing a state in which the pressing guide is in contact with the short side of the casting piece. , (c) is a diagram showing a state of being hit.
4 is a view showing the casting direction length and the non-solidification thickness in the region where the center solid phase ratio is 0.1 to 0.9 in the case of high carbon steel.
FIG. 5 is a diagram showing the casting direction length and the non-solidification thickness in the region where the central solid phase ratio is 0.1 to 0.9 in the case of medium carbon steel.
6 shows experimental results.

When hitting from the short side surface side of the casting piece at the time of continuous casting, when the casting piece width is large, generation | occurrence | production of segregation, such as center segregation and V segregation, may not be prevented effectively. The present invention has been achieved by allowing the structure of the mold to be blown continuously and collectively by unifying the entire short side of the casting piece located between at least two adjacent pinch roll pairs.

Example

Best Mode for Carrying Out the Invention The best mode for carrying out the present invention will now be described in detail along with the process until the invention is established.

As described above, when the casting piece is hit from the short side surface side, when the casting piece width is large, the vibration due to the hitting is not sufficiently propagated to the inside of the center portion in the width direction of the casting piece. In this case, since columnar crystals cannot be broken during growth, columnar crystals grow and cannot be made into a fine crystal structure, and sufficient segregation reduction effect is not obtained. In addition, vibration is not sufficiently transmitted to the equiaxed crystals generated near the final solidification portion in the width direction central portion of the cast piece, the equiaxed crystals are easy to bridge, and sufficient segregation reduction effect is not obtained.

Therefore, in order to prevent the occurrence of center segregation, V segregation, or the like, the inventors have repeatedly experimented to impart a blow from the surface of both short sides of the casting pieces including the unsolidified portion to face each other. By this experiment, it was examined how the impact vibration was sufficiently propagated to the inside of the width direction center part vicinity of the casting piece, when the casting piece hits from the short side surface side.

As a result, the inventors found that the vibration frequency and vibration energy in which the impact vibration effect is obtained exist in the range whose center solid-state rate f _S of a casting piece is 0.1-0.9. It has also been found that striking nearly the entire range of the above range is extremely effective for reducing segregation.

And the inventors proposed the continuous casting method of the steel which pressure-reduces the range whose center solid-state rate f _S of the thickness direction center part of the casting piece is at least 0.1-0.9, when casting the casting piece which has a rectangular cross section (Japanese Patent Application No. 2006-53057). This method is a method of hitting continuously in the width direction of the casting piece at at least one of the center solid phase ratios f _S when performing the above-described low pressure.

At that time, the pressure reduction ratio in the thickness direction of the cast piece becomes 1% or less per 1 m of the casting direction length, and the pressure is continuously reduced. Further, the short side faces on both sides of the casting piece face each other in the casting piece width direction at 4 to 12 Hz and a vibration energy of 30 to 150 J.

In Japanese Patent Application Laid-Open No. 2006-53057, an apparatus for performing the continuous casting method is proposed. This apparatus is a striking vibration apparatus of the structure which can collectively strike all the short side surfaces of the casting piece in the at least 1 segment of the segment which consists of a some guide roll integrally on both sides of the opposing side.

By the way, from the characteristic of the structure of the continuous casting machine which pressure-reduced in continuous casting of steel, it may not be performed in the segment which consists of a some guide roll, but may be performed in a pinch roll part.

When the inventor performed the hitting test in the continuous casting method of the steel proposed by the Japanese Patent Application Laid-Open No. 2006-53057, the inventors could obtain a sufficient effect as in the case of hitting the segment.

When hitting in such a pinch roll part, as shown in following Table 1, compared with the case of hitting in a segment, a structure becomes simple, securing installation space is easy, and maintenance of a facility can also be performed easily. There is an advantage.

[Table 1]

The striking vibration device during continuous casting of the present invention is made based on the above findings, and when the continuous casting of a casting piece having a rectangular cross section, the center solid phase ratio f _S of the thickness center of the casting piece is at least 0.1 to 0.9. In the range in which the reduction ratio in the thickness direction of the cast piece is within 1% per 1 m of the casting direction length, the pressure is continuously reduced, and at least one place within the range of the central solid-state ratio f _S is 0.1 to 0.9, As a device that strikes the short sides of both sides of the casting piece against each other in the casting piece width direction with a hitting vibration frequency of 4 to 12 Hz and a vibration energy of 30 to 150 J,

A mold hitting the short side of the casting piece,

A striking device for generating a periodic vibration and transmitting the vibration to the mold;

Has a striking positioning device for setting the interplanar distance between the mold and the short side of the casting piece,

The mold has a structure capable of collectively striking the cast piece short side surfaces between at least two neighboring pinch roll pairs of the light pressure zone composed of a plurality of pinch roll pairs.

The hitting positioning device sets the interval between the tip end surface of the mold and the casting piece short side at the return position of the mold after the detection of the pressing position on the casting piece short side of the mold, or the casting piece. Blowing positioning is carried out while pressing the guide which sets the space | interval of the front end surface of a metal mold.

In the continuous vibration casting of the present invention, the striking vibration device includes a cast piece 1 solidified and cast in a mold between a pair of pinch rolls 2a and 2b of a plurality of stages disposed downstream of the casting direction. The mold 3 etc. which were arrange | positioned as shown in FIG. Are arrange | positioned.

In FIG. 1, 3 is a metal mold | die hitting the short side surface of the casting piece 1. As shown in FIG. The die 3 has a structure in which a striking plate 3a is provided between at least two pairs of pinch rolls 2a and 2b adjacent to each other among pairs of pinch rolls 2a and 2b of multiple stages. By setting it as this structure, the whole short side surface of the casting piece 1 located between the pair of two-stage pinch rolls 2a and 2b which adjoin each other can be integrally integrated, and it can continuously hit collectively. In addition, it is preferable to make this metal mold | die 3 a casting agent from a viewpoint of durability, heat resistance, etc.

By the way, bridging, such as equiaxed crystal | crystallization, arises in the position where the center solidity rate of the casting piece 1 is 0.1 or more. However, bridging may occur again if the prevention of bridging by a blow is not complete. Therefore, it is preferable to continuously hit the range where the center solidity rate of the casting piece 1 is 0.4 or more fully, and it is preferable to strike the full length between a pair of pinch rolls 2a and 2b of multiple stages.

In addition, as will be described later, the central solid phase ratio of the casting piece 0.1 to 0.9 is relatively wide, and the position is constantly changing during the working industry. Therefore, in some cases, a blow between two pairs of pinch rolls 2a and 2b adjacent to each other is sufficient, and a blow between three pairs of pinch rolls 2a and 2b adjacent to each other is required as shown in FIG. have. However, in order to apply to the range of all the central solid-state rates, hitting a long range becomes excessive in equipment costs, and thus is a range in which vibration effects are obtained, for example, between three pairs of pinch rolls 2a and 2b adjacent to each other. A blow at is performed.

That is, it is important to vibrate over the wide range of the casting direction of the casting piece 1, and if possible, the length of the casting direction of the metal mold | die 3 can strike the whole region of a pair of pinch rolls 2a and 2b of multiple stages. It is preferable to set it as the length which is. However, in reality, the pair of pinch rolls 2a and 2b may be arranged or taken out in the continuous casting machine, so that the length that can be hit as long as possible as long as the various continuous casting apparatus does not interfere with each other. It is desirable to.

In addition, the pinch rolls 2a and 2b are generally configured to be capable of adjusting the amount of reduction by the hydraulic cylinder 5 or the like attached to the upper frame 4, and to prevent the pressure reduction.

6 is a striking device in which the mold 3 is attached to the tip portion thereof, and generates a periodic vibration and transmits the vibration to the mold 3, for example, an air cylinder is employed. The striking device 6 is disposed at, for example, two locations on the short side surfaces on both sides of the cast piece 1 including the unsolidified portion.

7 is a hitting position determination device, and the mold 3 is pressed against the short side of the casting piece 1 from the standby position shown in FIG. 2 (a) (see FIG. 2 (b)). After detecting the pushing position, this striking positioning device spaces the tip end surface of the metal mold 3 and the short side surface of the casting piece 1 at the return position of the metal mold 3 (refer to FIG. 2 (c)). Set L (hit amplitude: about 8 mm).

The striking positioning device 7 is not limited to the configuration shown in FIG. 2, and may be the configuration shown in FIG. 3. The impact positioning device 7 of FIG. 3 makes the mold | die by making the press guide 8 abut the short side surface of the casting piece 1 from the standby position shown in (a) figure (refer also (b)). The distance L (hit amplitude: about 8 mm) between the tip end face of (3) and the short side face of the casting piece 1 is set. The hitting positioning device 7 keeps the pressing guide 8 pressed against the short side of the casting piece 1 during the hitting shown in Fig. 3C. In addition, the arrangement conditions of the press guide 8 are previously set so that the space | interval L of the metal mold | die 3 and the casting piece 1 may become a predetermined space | interval.

Since the space | interval L of the short side surface of this metal mold | die 3 and the casting piece 1 differs also according to the width | variety of the casting piece 1 to cast, it actually references the short side surface of the casting piece 1 during casting. It is necessary to set. This spacing L affects the stroke of the striking device 6. In the case of a stroke shortage, the striking speed at the time of striking cannot be ensured, and vibration energy cannot fully be obtained. Therefore, at the time of a hitting start, the relative position adjustment of the short side surface of the metal mold | die 3 and the casting piece 1 is called positioning.

When continuously casting the casting piece 1 having a rectangular cross section using the apparatus of the present invention, the casting rate 1 in the casting direction length is 1 m in a range in which the center solid phase ratio f _S of the casting piece thickness center is at least 0.1 to 0.9. The pressure reduction in the thickness direction of the cast piece 1 is made to be within 1%, and the pressure is continuously reduced. At the same time, in at least one place within the range where the central solid-state ratio f _S is 0.1 to 0.9, the short side surfaces of both sides of the cast piece 1 face each other at a vibration frequency of 4 to 12 Hz and a vibration energy of 30 to Strike continuously in the width direction of the casting piece with 150J.

In the present invention, at least one place within the range where the center solid phase ratio f _S of the center of the cast piece thickness center is 0.1 to 0.9, it is the following reason that the cast pieces 1 continuously strike the short side surfaces of the opposing sides. Follow.

Since bridging such as equiaxed crystals occurs at a position where the center solid phase ratio is 0.1 or more, at the position of the cast piece 1 having a central solid state ratio of less than 0.1, generation of equiaxed crystals or the like is not sufficient, and the cast piece 1 is hit. This is because the effect is small. In addition, when the center solid phase ratio exceeds 0.9, the unsolidified molten steel becomes difficult to vibrate and flow, and therefore, it is difficult to break the space formed by bridging or bridging such as equiaxed crystals by the impact of the casting piece 1. For it is done.

4 shows the central solid phase rate of a cast piece when a high carbon steel (C = 0.40 mass%) having a thickness of 300 mm is continuously cast on the condition of a casting speed of 0.75 m / min and a specific quantity of 0.8 liter / kg of secondary cooling. It is a figure which shows the casting direction length and unsolidified thickness in this 0.1-0.9 area | region.

As shown in FIG. 4, the range whose center solid phase rate as described in this invention is 0.1-0.9 turns into an area long in a casting direction. In addition, the two arrows in FIG. 4 show the example which arrange | positioned the impact plate which gives a vibration to a casting piece at the position of these two places from the mold ejection side.

Thus, for the impact plate of FIG. 4, in the central solid phase rate in the range f _S is 0.4 to 0.8, it is an example that is batting Sequentially short side surfaces on both sides relative to the side cast cast piece in the width direction.

5 is a center solid phase of a cast piece when a medium carbon steel having a thickness of 250 mm (C = 0.06 mass%) is continuously cast under conditions of a casting rate of 1.0 m / min and a specific quantity of 0.8 liter / kg of secondary cooling. rate f _S is a view showing the casting direction length and thickness of the unsolidified area of 0.1 to 0.9.

Moreover, the two arrows in two places in FIG. 5 show the example which arrange | positioned the striking plate which gives a vibration to a casting piece at the position of these two places distance from a casting-out side.

Examples of the impact plate of FIG. 5, in the central solid phase rate f _S containing in the range 0.25 to 0.9, 0.25 to 1.0, continuously short-side surfaces of both sides of the casting section (1) relative to the cast piece in the width direction It is an example hitting.

In the case of the present invention, the casting piece in the thickness direction of the casting piece 1 in the thickness direction of the casting piece 1 per 1 m in the casting direction length is within a range in which the center solid phase ratio f _S of the casting piece thickness center is at least 0.1 to 0.9. Is continuously reduced. The reason is that the inventors calculated the roll spacing (limit amount) of the pinch rolls (2a, 2b) pairs in consideration of the amount of solidification shrinkage and the amount of heat shrinkage. This is because the reduction ratio in the thickness direction of (1) was within about 1%.

That is, if the reduction in the thickness direction of the casting piece 1 in the thickness direction of the cast piece 1 greatly exceeds 1% in the range of low solidity, deformation of the solidification interface increases and internal cracking occurs per 1 m of casting direction length. easy. In the case of continuous light reduction, it is sufficient to reduce the occurrence of internal cracking while reducing the amount of internal cracking, and the reduction ratio in this case is in the thickness direction of the casting piece 1 per 1 m of the casting direction length. Within 1%.

In addition, in the present invention, the short side rather than the long side of the casting piece is continuously hit. Between the rolls on the long side, the casting piece is easy to bulge, and when the hit vibration is applied to the bulged long side, fluctuation of the hot water surface on the upstream side is encouraged. Moreover, since the casting piece is bulging, a large amplitude cannot be given to the thickness center part of the casting piece. In addition, since the imparting imparting means is provided between the rolls, the spray arrangement for secondary cooling of the casting pieces between the rolls may be impaired, and continuous vibration imparting is not possible.

On the other hand, when the striking vibration is applied to the short side, a large volume change does not occur in comparison with the long side even if the displacement caused by the vibration does not occur. . Moreover, there are few mechanical problems for providing a hitting means.

For example, in the case where the casting piece width is 2300 mm and the mold 3 is 200 mm in width, in the case where the striking vibration is applied to the long side surface, the site to which the striking vibration can be applied is 200 mm in the casting direction. On the other hand, in the case where the striking vibration is applied to the short side surface, about 2300 mm in the casting direction becomes possible, for example, if the length of the striking plate is sufficiently secured, for example. Therefore, in the case where the striking vibration is applied to the short side, the volume change is about 1 / 11.5.

Further, in the present invention, the impact vibration frequency at the time of striking is set to 4 to 12 Hz, when the vibration vibration frequency is less than 4 Hz, since the vibration energy is not sufficiently transmitted to the non-solidified portion of the cast piece, the effect of reducing center segregation is reduced. Is less.

From the viewpoint of vibration energy provision, the larger the frequency, the more advantageous. However, when an air cylinder system is used as the vibration energy supply means, confusion occurs in the vibration waveform with an increase in the vibration frequency. In addition, when the cast piece 1 is hit, if the vibration up to about 12 Hz is applied from the deformation characteristic of the cast piece, the effect is sufficiently obtained. In addition, in the case of increasing the vibration frequency, it is necessary to increase the supply air pressure, and the influence on the peripheral device due to the vibration is concerned. Therefore, the upper limit of the center segregation reduction possible range was 12 Hz.

In addition, in this invention, vibration energy shall be 30J-150J. This is because when the vibration energy exceeding 150J is added, the peripheral equipment provided in the continuous casting machine may be damaged. In addition, the addition of more vibration energy than necessary causes disturbance to the durability of the striking device 6.

On the other hand, when the vibration energy is less than 30J, it is because the striking vibration performed from the short side surface side of the casting piece 1 does not sufficiently propagate to the inside of the casting piece near the center part of the casting piece width direction.

The vibration energy E (J) is equal to E = 0.5 × M when the weight of the mold 3 is M (kg) and the blow speed of the mold 3 to the casting piece 1 is V (m / sec). It can be obtained by × V ^2. Therefore, in order to change vibration energy, what is necessary is just to change the weight of the metal mold | die 3, or to change the speed of collision with the casting piece 1 of the metal mold | die 3. However, even if a large vibration energy is applied every minute and several times, the bridging at the end of the solidification, especially under a high solidity rate, cannot be completely suppressed, and therefore, the vibration frequency is particularly important.

In addition, the range of the blow vibration frequency prescribed | regulated by the said invention does not change to the bloom and slab from which the casting piece width differs. However, in bloom and slab, since the volume containing non-solidification differs, the optimal vibration energy changes.

Using a blow vibration device of the present invention in a range of the downstream side from an upstream side of a position, it strikes the surface of the cast piece (1) in the soft reduction at the time of continuous casting, and also, the center solid phase rate f _S 0.1 ~ 0.9 It is preferable to perform the cast iron piece 1 at the ratio of 0.5-2.5 mm per length of 1 m of a casting direction.

As described above, in the present invention, even when the casting piece 1 is lightly reduced, the vibration caused by the blow is sufficiently propagated inside the casting piece 1 by giving the casting piece 1 a blow vibration satisfying the optimum vibration condition. The segregation reduction effect can be obtained further.

(Example)

Hereinafter, the experimental results performed to verify the present invention will be described.

Two pairs of striking devices as shown in FIG. 1 were provided in the casting direction. High carbon steels in the component ranges shown in Table 2 below were cast into bloom or slab. The size is 250-310 mm in thickness, 425 mm in width, or 2300 mm. In addition, the casting speed was 0.70 m / min or 0.75 m / min.

Table 2

At the time of pressure reduction, the center solidity rate was 0.1-0.9, and the casting piece was pressure-reduced at the ratio of 1.0 mm per 1m of length in the casting direction. As secondary cooling, specific water quantity was unified on the condition of 0.8 liter / kg.

By using an air cylinder type striking device, a frequency of 4 Hz or 6 Hz (240 per minute) is applied to two parts of the short sides on both sides of the casting piece at the position including the non-solidified portion so that the amplitude of the vibration of the striking surface is ± 3 mm. 3 times or 360 times), and the casting piece was vibrated.

As for the impact conditions, the mold weight was 450 kg and the impact speed was about 0.47 m / sec or 0.71 m / sec (vibration energy was 50 J or 114 J). As for the shape of the contact surface of a bloom or slab of the metal mold | die attached to the front-end | tip of a hitting apparatus, the width | variety of the casting piece thickness direction was about 200 mm, and the length of the casting direction was about 1100 mm.

In the casting test, a sample of the casting piece is taken and sandwiched between the thickness direction central part and the thickness direction 10 mm in the thickness direction, 200 mm in the width direction, and 15 mm in the casting direction from a position corresponding to the thickness of the cross section of the sample and the center in the width direction. A test piece of degree was taken.

Using these test pieces, cutting powder was extract | collected from 26 places of positions corresponded to the thickness direction center part of the casting piece with the drill blade of diameter 2mm in 7 mm pitch, and C content was analyzed. The ratio C / CO obtained by dividing the analysis value C (mass%) by the C analysis value CO (mass%) of the molten steel in the ladle was obtained, and the maximum value of these ratios (hereinafter referred to as "maximum center segregation rate") was obtained.

The experimental conditions are shown in Table 3 below. This experiment compares the invention example which added the striking vibration between pinch rolls by the striking vibration apparatus of this invention (high carbon steel C), and the striking vibration in the segment part by the striking vibration apparatus proposed by Japanese Patent Application No. 2006-53057. It carried out about the example (high carbon steel B) and the comparative example (high carbon steel A) manufactured without adding a hitting vibration.

The experimental results are shown in FIG. 6. When the impact vibration was added, there was no big difference in the maximum center segregation in either case, and the maximum center segregation ratio was all good at 1.15 or less. On the other hand, in the case where the impact vibration was not added, the maximum center segregation rate might exceed 1.15 when the casting piece width became large. In addition, evaluation of the experimental result made the case where the maximum center segregation rate is 1.15 or less, and made the case exceeding it the defect.

It is needless to say that the present invention is not limited to the above examples and may change the embodiment as appropriate as long as it is a scope of the technical idea described in each claim.

For example, in the above description, although the air cylinder is shown as the striking device 6, as long as it can drive the mold 3, even if it is a hydraulic cylinder, any method, such as a system using an eccentric cam and a spring, is used. It may be.

The present invention can be applied not only to high carbon steel casting pieces as shown in the examples, but also to continuous casting of other steel grades such as medium carbon steel casting pieces and low carbon steel casting pieces.

1: Casting piece 2a, 2b: Pinch roll
3: mold 3a: blow plate
6: striking device 7: striking positioning device
8: pressing guide

Claims (1)

When continuously casting a casting piece having a rectangular cross section, the rolling reduction rate in the thickness direction of the casting piece per 1 m of the casting direction length falls within a range in which the center solid phase ratio f _S of the casting piece thickness center portion is at least 0.1 to 0.9. ) And continuously lowering the pressure to be within 1%, and hitting short sides of the opposing sides of the cast piece at at least one location within the range of the central solid phase ratio f _S of 0.1 to 0.9. The vibration frequency is 4-12Hz, the vibration energy is 30-150J, and the device continuously strikes in the casting width direction,
A mold hitting the short side of the casting piece,
A striking device for generating a periodic vibration and transmitting the vibration to the mold;
Has a striking positioning device for setting the interplanar distance between the mold and the short side of the casting piece,
The mold has a structure capable of collectively striking the integral piece short side surfaces between at least two adjacent pairs of pinch roll pairs in a light-pressure zone composed of a plurality of stage pinch roll pairs. Done,
The hitting positioning device sets the distance between the tip end surface of the mold and the casting piece short side at the return position of the mold after detection of the pressing position of the mold piece short side of the mold, or the casting piece and A striking vibration device during continuous casting, characterized in that the striking position is determined while pressing a guide for setting the gap between the end faces of the mold.

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