JP5342905B2 - Slab slab continuous casting equipment - Google Patents

Description

  The present invention relates to a continuous casting facility for producing a steel slab slab by continuous casting, and in particular, a continuous slab for producing a steel slab slab for obtaining a final product steel material in which center segregation and formation of minute cavities are reduced as much as possible. It relates to casting equipment.

  FIG. 1 is a schematic explanatory view showing a continuous casting facility, in which 1 is a mold, 2 is a slab cast piece, 3 is a guide roll provided in pairs along the cast piece 2, and 4 is a reduction roll. ing. In such continuous casting equipment, the molten steel is cooled (primary cooling) by the mold 1 to form a slab cast 2 while forming a solidified shell, and further cooled (secondary cooling), along the guide roll 3 and the rolling roll 4. Will be pulled out. The slab slab 2 obtained in this way is subsequently hot-rolled to obtain a product steel material having a predetermined thickness.

  When steel is continuously cast, there is a problem that components such as carbon, sulfur, phosphorus, and manganese are segregated at the center of the slab and are likely to be concentrated. Such segregation is known to be caused by the molten steel flow due to solidification shrinkage at the end of solidification of the slab slab. It is also known that a central cavity defect (hereinafter sometimes referred to as “center porosity”) occurs when a closed unsolidified region is solidified with a delay in the center of the slab slab.

  As a technique for solving such a problem, various methods have been proposed for continuously casting a slab slab at the end of solidification while being reduced by the reduction roll 4 as shown in FIG. 1 (for example, Patent Documents 1 and 2). . Among them, the technique of Patent Document 1 shows that a slab of good quality can be produced by lightly reducing at the end of solidification using a small-diameter roll and then strongly reducing using a large-diameter roll immediately after solidification. Yes.

  However, if the slab slab passes through the installation position of a large diameter roll with a diameter of 1000 mm when the slab slab is unsolidified due to factors such as fluctuations in the casting speed, a bulging phenomenon due to molten steel static pressure occurs. Cracks occur at the solidification interface, and the internal quality deteriorates.

  On the other hand, in the technique of Patent Document 2, it has been proposed to reduce the final solidification portion of the slab cast with a roll having a diameter of 2 to 5 times the thickness of the slab cast (large reduction roll). However, for example, if the thickness of the slab slab is about 280 mm, the size of the reduction roll needs to be at least about 560 mm. Therefore, in this technique, the same thing as the above technique can be said, and due to factors such as fluctuations in casting speed, the deterioration of internal quality due to the bulging phenomenon that occurs when unsolidified slabs pass through the reduction zone is fully considered. It cannot be said that it is doing.

  By the way, when rolling down the slab slab, from the viewpoint of preventing the occurrence of center segregation, the slab slab has a low central solid fraction (for example, 0.1 to 0.3 as the central solid fraction). From the viewpoint of achieving the effect of reducing the center porosity, the slab has a central solid fraction of 0.7 (flow limit solid fraction). ) Is preferably reduced.

The center porosity can be reduced to some extent by the reduction in the subsequent hot rolling process. However, especially when the final steel plate product is thick (for example, the steel material has a thickness of about 60 to 140 mm), since a large reduction ratio from the slab slab cannot be obtained, strong reduction is applied in the rolling process. However, the center porosity will remain. Therefore, when the slab slab thickness before starting rolling is W ₀ (mm) and the steel product thickness after hot rolling is W (mm), these are (W / W ₀ )> 0. In order to obtain a product having no internal defects when producing a thick steel material that satisfies the relationship of No. 5, it is necessary to reduce defects as much as possible in the continuous casting stage (stage under slab pressure).

  Furthermore, regarding the configuration of the reduction roll, the larger the roll diameter, the larger the frame structure for supporting the reaction force from the reduction roll (see FIG. 6 described later). For these reasons, there is a demand on the facility side that it is preferable that the diameter of the rolling roll is as small as possible, and it is also important to have a facility configuration that meets these requirements as much as possible.

JP-A-8-164460 JP-A-3-124352

  The present invention has been made to solve such problems in the prior art. The purpose of the present invention is to effectively reduce the occurrence of center porosity even in a thick plate product, and at the time of slab production. It is an object of the present invention to provide a steel continuous casting facility capable of producing a good slab slab without causing any bulging phenomenon.

The continuous casting equipment of the present invention that has been able to solve the above problems is a continuous casting of a slab slab having a carbon content of 0.03 to less than 0.2% by mass while being reduced by a reduction roll, and then hot rolling. Is a continuous casting facility for producing a slab slab that obtains a steel material satisfying the relationship of the following formula (1), and the central solid fraction of the slab slab when the slab slab is reduced during continuous casting: The range from the position where A becomes 0.7 to the downstream side 8 m is set as the effective reduction area, and one or more pairs of reduction rolls integrally formed in the axial direction with a roll diameter of 417 mm or more are arranged in the effective reduction area. However, the present invention has a gist in that the total reduction amount to the slab is 10 mm or more.
(W / W ₀ )> 0.5 (1)
However, W ₀ (mm): Thickness of slab slab before starting reduction W (mm): Steel product thickness

  The above-mentioned problems of the present invention include (a) an equipment configuration in which one or more pairs of rolling rolls having a roll diameter of 380 mm or more and divided in the axial direction are arranged in the effective rolling reduction area as described above, or (b) as described above. This can also be solved by an equipment configuration in which one or more pairs of rolling rolls having a roll diameter of 280 mm or more and divided into three in the axial direction are arranged in the rolling reduction effective region.

  In any of the above-described continuous casting equipment, the roll diameter of the reduction roll is preferably 620 mm or less, and the number of rolls to be arranged is appropriately adjusted according to each roll diameter. For example, in the case of continuous casting equipment that employs a rolling roll integrally formed in the axial direction (hereinafter sometimes referred to as “integrated roll”) (that is, the roll diameter is 417 to 620 mm), 3 to 19 It is preferable to adopt a configuration in which a pair is arranged. Further, in the case of a continuous casting facility that employs a rolling roll formed by being divided into two in the axial direction (hereinafter sometimes referred to as “two-divided roll”) (that is, the roll diameter is 380 to 620 mm), 3 It is preferable to have a configuration in which ~ 20 pairs are arranged. Furthermore, in the case of a continuous casting facility that employs a rolling roll formed by being divided into three in the axial direction (hereinafter sometimes referred to as “three-divided roll”) (that is, the roll diameter is 280 to 620 mm), 3 It is preferable to have a configuration in which ~ 20 pairs are arranged.

  In addition, it is also preferable to have a configuration in which a preliminary reduction area is provided in the range of 2 m or less at least downstream of the effective reduction area. By adopting such a configuration, it is possible to cope with changes in casting conditions such as casting speed. It will be something.

  When such a preliminary rolling area is provided, it is preferable to arrange one or more reduction rolls having the same diameter and form as the reduction roll used in the effective reduction area so that the roll pitch is 620 mm or less.

  In the present invention, in the continuous casting equipment configured to reduce the slab cast piece by the reduction roll immediately after the solidification end stage or the end of solidification during the continuous casting, the reduction roll is defined and arranged in the area. By appropriately defining the diameter and the form of the slab, a continuous casting facility capable of producing a slab slab with reduced microcavity defects generated at the end of solidification was realized.

It is a schematic explanatory drawing which shows a continuous casting installation. It is the enlarged view which showed the reduction area | region. It is the graph which showed the influence of rolling when various places of a slab slab were rolled down. It is a graph showing the relationship between the specific (W / W ₀₎ and the defect reduction ratio. It is the schematic for demonstrating the form of a reduction roll. 4 is a graph showing a relationship between a roll reaction force RF and a roll diameter R. It is the graph which showed the relationship between the slab surface temperature when a bulging is easy to generate | occur | produce, and the distance from a meniscus. It is the graph which showed the influence which the number of rolls (number of roll pairs) has on the roll diameter and the rolling reduction range (the rolling effective area).

The present inventors are intended for high carbon steel (steel material having a carbon content of 0.2 to 0.6 mass%), and the ratio of the steel product thickness W to the slab slab thickness W ₀ before the start of rolling. (W / W ₀ ) is a slab slab for producing a thick steel material having the relationship of the above formula (1), and no bulging phenomenon occurs during continuous casting. In addition, the construction of continuous casting equipment that does not generate defects such as center segregation has been studied from various angles.

  As a result, a slab casting that reduces the cavity defects generated at the end of solidification by prescribing the effective rolling reduction area according to the type of steel material and making the diameter and number of reduction rolls to be arranged in that area appropriate. Since it was found that a piece can be produced and its technical significance was recognized, the application has been filed first (Japanese Patent Application No. 2008-081672).

  The inventors of the present invention target medium carbon steel (steel material having a carbon content of less than 0.03 to 0.2% by mass) having a different carbon content even after the above invention is completed, and the same viewpoint as described above. From now on, further investigations were made. As a result, the present inventors have found that the above object can be achieved by designing the equipment according to the medium carbon steel and completed the present invention. Hereinafter, the configuration and operational effects of the present invention will be described along the background of the completion of the present invention.

The steel material to be used in the present invention satisfies the relationship of the above formula (1), but when the value of the ratio (W / W ₀ ) is 0.5 or less, a cavity defect occurs in the hot rolling stage. Since it becomes possible to press-fit, it is not necessary to reduce a defect by reduction. The upper limit of the value of the ratio (W / W ₀ ) is not particularly limited, but if the steel material is such that this value becomes too large, the effect of reducing defects due to reduction may not be achieved. The following is preferable. Further, the value of the ratio (W / W ₀ ) only needs to satisfy the relationship of the above formula (1) finally (after hot rolling), and the value of this ratio also takes into account the rolling rate after hot rolling. It was put in. Therefore, it is not necessary to satisfy the relationship of the above formula (1) only by the reduction of continuous casting, but in order to achieve the purpose of reduction, it is necessary to reduce under the conditions that can be implemented with the facility of the present invention.

Under the preconditions as described above, the present inventors have made various solid slab slab solid fractions (central solid fraction), total reduction amount (mm), and slab slab central portions at the start of reduction. The effect of temperature (center temperature) (° C) on the defect size was examined based on internal defect investigation and three-dimensional finite element method (FEM method) analysis. An enlarged view of the reduction region at this time is shown in FIG. In FIG. 2, 5 is a solidified shell of a slab slab, 6 is a reduction range, 7 is an unsolidified portion (molten steel portion), R is a diameter of a reduction roll, H is a total reduction amount, and Δh ₁ and Δh ₂ are each pair of rolls. Each of the reduction amounts to be reduced by. Further, the “total reduction amount H” is the sum of the reduction amounts Δh ₁ , Δh ₂ ... By each reduction roll pair, as shown in FIG. That is, when the thickness of the slab slab 2 at the start of the rolling is X ₀ (mm) and the thickness of the slab slab at the end of the rolling is X ₁ (mm), it is represented by (X ₀ -X ₁ ). Is.

  As a result, in the case of medium carbon steel whose carbon content is 0.03 to less than 0.2% by mass, the central solid phase ratio is 0.7 (the central temperature of the slab cast is C-containing). It is effective to start the reduction from the amount: 0.15% by mass (1481 ° C.) and to reduce the temperature range of the slab slab center to 1150 ° C. (hereinafter this range is referred to as “effective reduction area”). It turned out to be. The time required to pass through the effective rolling reduction area at, for example, a casting speed of 1.0 m / min is about 8 minutes. Therefore, the effective rolling reduction area is approximately 8 m downstream from the position where the central solid fraction is 0.7. It will be up to the position. The center temperature is calculated by solidification heat transfer calculation.

  FIG. 3 shows the experimental results for the inventors to search for the effective reduction area. That is, FIG. 3 shows the influence of the reduction when various portions of the slab slab are reduced. In the figure, the asterisks indicate the center of the slab slab (the center in the width direction and the thickness direction). ) Was evaluated for the occurrence of defects, and those indicated by △ were evaluated for the occurrence of defects at the center part in the thickness direction at the part inside the slab slab width direction end face by the thickness length. Is. The steel types used at this time are C: 0.15 mass%, Si: 0.24 mass%, and Mn: 0.74 mass%, and have a slab cast cross section of 280 mm x 2100 mm. Moreover, an integrated roll is adopted.

  The defect reduction rate (defect size reduction rate) shown in FIG. 3 is determined based on the following criteria, and the larger the reduction rate, the more effective the reduction.

[Defect size reduction rate evaluation method]
Based on the initial defect thickness d ₀ (defect original thickness at the start of rolling), the ratio of the reduction amount (d ₀ −d) of the defect size d after the completion of rolling to the defect original thickness d ₀ [(d ₀ -d) is concerned with the evaluation by / d _0]. As the thickness of the product increases, the allowable defect size in the slab slab decreases (that is, the reduction ratio increases), but the steel material has a relationship such that (W / W ₀ )> 0.5. Therefore, it is necessary to guarantee that the reduction ratio is 0.2 or more, and the effective reduction range is set from this viewpoint.

FIG. 4 shows the defect reduction rate [relation between the ratio (W / W ₀ ) and the defect reduction rate] of the slab according to the ratio (W / W ₀ ) (which can be rendered harmless by rolling / reducing). That is, it was confirmed that when the defects of the slab were 20% (defect reduction rate 0.2), the defects could be rendered harmless in the subsequent rolling process. In the case of high carbon steel (steel material having a carbon content of 0.2 to 0.6% by mass), a defect reduction rate of 0.25 was required, but medium carbon steel (carbon content of 0.1%). In the case of steel materials of less than 03 to 0.2% by mass, since the deformation resistance is smaller than that of high carbon steel, the inside is easily deformed, and the defects are sufficiently harmless with a smaller defect reduction rate than high carbon steel. It is considered possible.

  As shown in FIG. 3 above, the effective reduction area in the present invention is from the end of solidification phase where the central solid phase ratio (Fs) is 0.7 to the complete solidification position where the central solid phase ratio is 1.0. Of course, it is shown that the reduction can be effectively performed in a temperature range where the temperature is high and the internal deformation is easy even after complete solidification.

  In addition, since the strength of steel material increases as the C content increases (that is, it becomes difficult to deform), the roll reaction force during slab slab reduction increases as the carbon concentration increases, and is required for equipment such as rolls. It is necessary to increase the strength. From this point of view, the present invention is intended for medium carbon steel having a C content of less than 0.2% by mass. If the C content decreases, the strength decreases accordingly, but if the C content is designed up to 0.03% by mass according to the above criteria, there is almost no inconvenience. If the C content of the steel material decreases, the solidus temperature increases accordingly. However, if the C content is within the above range, the temperature of the slab slab center can be determined based on the above range. good.

  Even if the basic casting speed (constant speed) is changed depending on the steel type, the effective rolling reduction area is about 8 m, assuming that the effect on the cooling rate of the center part of the slab is small in the above-described carbon content range. It becomes.

  When the present inventors have arranged the relationship between the total reduction amount H and the occurrence of defects, the reduction effective region shown in FIG. 3 can be obtained by reducing the total reduction amount H to 10 mm or more in the effective reduction region. It is also known that the good results shown (defect reduction rate in the effective reduction area of 0.2 or more) can be obtained. Therefore, an equipment design for assuring that the total reduction amount in the effective reduction range is 10 mm or more was examined.

  The reaction force RF acting on the roll due to the roll pressure can be obtained by the following equation (2) from the beam theory where the allowable deflection of the roll is 0.5 mm. Further, the relationship between the rolling amount Δh per pair of rolls and the reaction force RF can be expressed by the following equation (3) which is a general rolling theoretical equation.

R ≧ −1.19 × 10 ⁻⁹ RF ² + 1.41 × 10 ⁻³ RF + 2.73 × 10 ² (2)
RF = 2Aσ√ (R × Δh) (3)
However, A: Rolling width (mm), σ: Deformation resistance (kN), R: Roll diameter (mm)
Δh: Amount of narrowing (rolling amount) per pair of rolls (mm)

  Furthermore, regarding the form of the reduction roll, the larger the roll diameter, the larger the frame structure (the structure of the part that supports the reduction roll) for supporting the reaction force from the reduction roll (see FIG. 6 below). become. For these reasons, there is a demand on the upper surface of the facility that the diameter of the rolling roll is preferably as small as possible, and it is also important to have a facility configuration that meets such a requirement as much as possible.

  Such a situation will be described with reference to the drawings. 5A and 5B are schematic views for explaining various types of rolling rolls. FIG. 5A is a rolling roll (integral roll) formed integrally in the axial direction, and FIG. 5B is an axial direction. FIG. 5C shows a reduction roll formed by dividing into two in the axial direction (three-division roll). FIG. In FIG. 5, 4 is a rolling roll, 8 is a shaft box for covering a bearing (not shown) for supporting the rolling roll 4, and 9 is a shaft of the rolling roll.

  In the case of split rolls [FIGS. 5 (b) and (c)], the reduction roll is split and held by different bearings. In order to support the same reaction force, the split roll has a roll diameter. Can be reduced. It should be noted that the position of the axle box 8 for covering the bearing needs to be arranged at a position where defects are unlikely to occur so that the reduction at the portion to be reduced does not become insufficient. If the rolling roll is divided into four or more parts, it is difficult to avoid the axle box 8 being disposed near the center of the roll (position where defects are likely to occur). Therefore, the rolling roll is preferably divided into three or less parts.

  The present inventors have examined the relationship between the roll diameter R and the roll reaction force RF (per pair) based on the above formulas (2) and (3), taking these situations into consideration. The result (relationship between the roll reaction force RF and the roll diameter R) is shown in FIG. 6, and it can be seen that the roll reaction force RF increases as the roll diameter R increases. In other words, it can be seen that a large reaction force can be achieved with a small number of rolls if the roll diameter is increased due to the design of the reduction roll. In this case, the “necessary reaction force” is about 3,000 kN.

  On the other hand, in terms of the form of the reduction roll, it can be seen that the roll diameter for achieving the required roll reaction force can be reduced in the split type. This means that a large roll reaction force RF can be secured even if the roll diameter is small by dividing the roll and holding it with different bearings. From these viewpoints, the present inventors have studied the optimum configuration of the continuous casting equipment according to the form of the rolling roll (that is, the rolling roll is an integral type or a split type) from various angles.

  FIG. 7 is a graph showing the relationship between the slab slab surface temperature (slab surface temperature) and the distance from the meniscus when the bulging phenomenon is likely to occur. The “assumed rolling start position” shown in FIG. 7 indicates a position where the solid phase ratio becomes 0.7 (starting point of the effective rolling area). As shown in FIG. 7, the surface temperature of the slab slab when the bulging phenomenon is likely to occur is about 700 ° C. In addition to the surface temperature of the slab slab, there are factors such as the molten steel static pressure, roll pitch, etc. The larger the bulging phenomenon, the easier the bulging phenomenon occurs, resulting in defects. It becomes easy to do. According to a study by the present inventors, if the roll diameter (roll pitch P ≧ roll diameter R) corresponding to the roll pitch P (distance between the centers of adjacent rolls) is 620 mm or less, the bulging phenomenon is caused. It was found that it did not occur.

  The above results were examined using a high carbon steel having a carbon content of 0.6 mass% as a raw material. However, if the roll pitch is 620 mm or less, other steel types (carbon content is 0.03 mass% or more, It has been confirmed that the reduction of internal alteration is negligible even for slab slabs that pass through the effective reduction area while remaining unsolidified (less than 0.2% medium carbon steel).

  According to the results shown in FIG. 6, in the case of an integrated roll, it can be predicted that the roll diameter should be about 650 mm or more in order to ensure the necessary reaction force, but the above-described bulging phenomenon does not occur. Therefore, the roll diameter (roll pitch P ≧ roll diameter R) is preferably 620 mm or less.

  Therefore, based on the knowledge obtained above, after setting the effective reduction area within 8 m, the minimum diameter and the number (logarithm) of the integral rolls for ensuring the total reduction amount: 10 mm or more in this area were examined. . FIG. 8 is a graph showing the influence of the number of rolls (number of roll pairs) on the roll diameter R and the reduction range (effective reduction area) as a condition for satisfying the above conditions. R (required minimum roll diameter) and ▲ indicate the reduction range, respectively. As a result, the roll diameter R and the roll pitch P are regarded as being equivalent, and the number of rolls (number of roll pairs) for securing a total reduction amount of 13 mm or more in an effective reduction area of 8 m or less is examined. The data used as the basis for FIG. 8 is shown in Table 1 below.

  As is clear from these results, when using an integral roll, if the number of rolls is 20 pairs or more, even if the reduction roll is designed to be as small as possible, the reduction required within the effective reduction area (within 8 m) is required. I can't understand. In this case (the maximum number of necessary rolls is 19), it can be seen that the roll diameter needs to be 417 mm or more. On the other hand, when the roll diameter is about 620 mm, the effective number of rolls can be realized by setting the number of rolls to 3 pairs or more (however, the roll pitch is 620 mm or less). Become.

  From these examination results, the roll diameter R is set to 417 mm or more in order to control with an integrated roll so that the total reduction amount is 10 mm or more within the range (within the effective rolling reduction region) effective for improving the internal quality. It can be seen that one or more pairs may be arranged. Further, it is preferable that a continuous casting facility in which 3 to 19 pairs of rolling rolls having a roll diameter R of 417 to 620 mm are arranged in the above-described region (within a range of 8 m) depending on the roll diameter.

  Incidentally, “according to the roll diameter” basically means that the number of rolls is increased as the roll diameter is reduced, as is apparent from FIG. However, the number of rolls shown in FIG. 8 indicates the minimum number (the number of roll pairs) for achieving a total reduction amount of 10 mm or more. For example, a reduction roll having a diameter of 600 mm is applied to the effective reduction area. It is also within the technical scope of the present invention to arrange 6 to 7 pairs. However, whatever roll arrangement is adopted, the roll pitch P is preferably 620 mm or less.

  The equipment configuration described above is for a case where the casting speed is in a steady state (for example, the casting speed is constant at 1.0 m / min). In continuous casting operation, the variation in casting speed is ± 0.1 m / min. There is a case where it is allowed within the range of min. The present inventors also examined the equipment configuration that can cope with such operating conditions.

  When the range of the above-described variation in the casting speed is converted into a reduction distance, the necessary reduction area changes within a range of 2 m on both the upstream side and the downstream side of the effective reduction area. That is, when the casting speed is reduced by 0.1 m / min, the reduction start position (position where the central solid fraction is 0.7) is 2 m upstream from the reduction start reference position (starting point of the effective reduction area). Up to. When the casting speed is increased by 0.1 m / min, the reduction end position is 2 m downstream from the reference position (end point of the effective reduction area).

  In order to cope with such a situation, in the continuous casting equipment of the present invention, a preliminary rolling reduction area is provided at least downstream of the effective rolling reduction area, and a reduction roll conforming to the above standard is also provided in this area. Is preferred. Various specific forms in the case where such a reduction preliminary area is provided will be described.

  For example, when only a rolling roll having a roll diameter of 417 mm (however, an integrated roll) is arranged, 19 pairs of rolling rolls are arranged in the effective rolling area (range of 8 m). There will be no room. In such a case, it is necessary to set the total rolling reduction area up to 2 m upstream and 2 m downstream of the effective rolling reduction area up to 12 m (effective rolling reduction area: 8 m + reducing preliminary rolling reduction area: 4 m). What is necessary is just to arrange | position a reduction roll in each reduction preliminary | backup area | region. At this time, as the number of rolling rolls arranged in the rolling reduction area, a maximum of 9 pairs (19 × 4/8) is required as the ratio (4/8) of the rolling reduction area (4 m) to the rolling reduction effective area (8 m). As a whole, a total of 28 pairs of rolling rolls (up to 10 pairs in the effective rolling area) are required.

  For such a preliminary rolling area, it is not necessary to always operate both the upstream and downstream rolling rolls, and either upstream or downstream of the effective rolling area depending on the casting speed. What is necessary is just to make it operate | move about the reduction preliminary | backup area | region. However, in order to cope with such an operation, it is preferable in terms of equipment to arrange a reduction roll in the preliminary reduction areas on both the upstream side and the downstream side. In addition, when the reduction roll arranged in either the upstream side or downstream side of the effective reduction area is operated, the corresponding effective area of the reduction area (for example, the upstream preliminary area is activated). What is necessary is just to make it not act | operate the reduction roll arrange | positioned in the 2m upstream part of the effective reduction area | region at the time of making it operate | move.

  On the other hand, when installing a reduction roll having a roll diameter of 620 mm, it is sufficient to arrange at least one pair (preferably 3 pairs or more) of reduction rolls in the effective reduction area (range of 5 m). There will be room. For example, the casting speed is reduced by 0.1 m / min, and the reduction start position (position where the central solid fraction is 0.7) is 2 mm upstream from the reduction start reference position (starting point of the effective reduction area). Even so, if one or more pairs of rolling rolls are installed in the range of 3 m upstream of the effective rolling reduction area, a total rolling reduction of 10 mm or more can be secured in this range. Further, even if the casting speed is increased by 0.1 m / min and the reduction end position is 2 m downstream from the reference position (end point of the effective reduction area), it is within the range of 3 m downstream of the effective reduction area. If one or more pairs of reduction rolls are installed, a total reduction amount of 10 mm or more can be secured in this range.

  That is, in the case of a rolling roll having a roll diameter of 620 mm, 6 to 12 pairs are arranged in the effective rolling reduction area (range of 8 m) so that the roll pitch is 620 mm or less, thereby responding to fluctuations in casting speed. Operation becomes possible. In such a case, it is possible to cope with fluctuations in the casting speed without providing a preliminary rolling reduction area.

  If the roll diameter is other than that, a preliminary reduction area is provided upstream and / or downstream of the effective rolling area in accordance with the above criteria, and the roll diameter and the number (number of pairs) to be arranged in the effective rolling area. Depending on the arrangement position (arrangement position in the effective reduction area), it is possible to adopt a configuration in which one or more reduction rolls are arranged in the preliminary reduction area. However, it is necessary to secure at least the roll pitch of 620 mm or less for the rolls arranged in the preliminary rolling area. The roll pitch when a pair of reduction rolls are arranged in the preliminary reduction area means the closest distance between the roll arranged in the effective reduction area and the reduction roll arranged in the preliminary reduction area.

  However, in consideration of the compatibility and workability of the reduction roll in the effective reduction area, the diameter of the reduction roll arranged in the reduction reduction area and the form thereof are the diameter of the reduction roll arranged in the effective reduction area. Further, it is preferable to align them with the form as much as possible. For example, when a reduction roll integrally formed with a roll diameter of 417 mm is installed in the effective reduction area, it is preferable to install a reduction roll having the same form and the same roll diameter in the preliminary reduction area.

  That is, in the continuous casting equipment of the present invention, a configuration in which the reduction preliminary region as described above can be arranged as necessary according to the roll diameter can be adopted, and by adopting such a configuration, a continuous according to the variation in casting speed can be adopted. Casting can be performed without causing the occurrence of center porosity.

  The above results stipulate the optimum equipment configuration when the integrated roll is applied. However, the inventors have determined the optimum equipment configuration when the rolling roll divided into two or three is applied. Were also examined in the same manner as described above. That is, the continuous casting equipment has a requirement on the equipment side that it is preferable that the diameter of the rolling roll is as small as possible. In order to meet such a demand, it is advantageous that the rolling roll to be applied is divided into two or three parts. Is expected (FIG. 6). Therefore, the optimum equipment configuration when such a rolling roll was applied was also examined.

  The relationship between the roll reaction force RF and the roll diameter R when the two-part or three-part reduction roll is applied is as shown in FIG. 6, but based on this result, the reduction roll was made a split type. In this case, the roll diameter can be reduced.

  In the integrated roll as described above, it is impossible to set the roll diameter in consideration of only the roll reaction force RF, and the minimum diameter and number of the reduction rolls from the viewpoint of the size of the effective reduction area and the allowable roll pitch. In consideration of (logarithm), when the rolling roll is divided, the roll reaction force RF can be secured with a smaller roll diameter (FIG. 6). Therefore, the minimum required roll diameter may be set in consideration of only the minimum diameter of the rolling roll that ensures the roll reaction force RF. That is, as apparent from the results shown in FIG. 6, (a) when using a rolling roll divided in two in the axial direction, the roll diameter is set to 380 mm or more, or one or more pairs are arranged, or ( b) When using a rolling roll divided into three in the axial direction, the roll diameter is set to 280 mm or more (necessary reaction force: 3,000 kN or more), one or more pairs are arranged, and other conditions are the same. It has been found that the same effect as in the above-described equipment configuration can be obtained with the equipment configuration.

  Even when such an equipment configuration is adopted, the roll diameter of the reduction roll is preferably set to 620 mm or less. In this case, when the optimum number of rolls was examined in the same manner as described above, the reduction rolls in the effective reduction area can be arranged in more than 20 pairs depending on the roll diameter, but the facility becomes complicated. Considering this, it is preferable to arrange 3 to 20 pairs in each case where the roll diameter is 380 mm or more and in the case where the roll diameter is 280 mm or more.

  Further, even in a continuous casting facility that employs a split-type rolling roll as described above, a rolling preliminary area can be provided in the range of 2 m or less upstream and / or downstream of the effective rolling area. In the preliminary reduction area, one or more pairs of reduction rolls corresponding to the roll diameter and form of the reduction rolls arranged in the effective reduction area may be arranged so that the roll pitch is 620 mm or less.

1 Mold 2 Slab slab 3 Guide roll 4 Rolling roll 8 Axis box 9 Axis

Claims (12)

The relationship of the following formula (1) is obtained by continuously casting a slab slab having a carbon content of less than 0.03 to 0.2% by mass while being reduced by a reduction roll, and then hot rolling the obtained slab slab. In the continuous casting equipment for producing the slab cast slab used in the method for obtaining a steel material satisfying the requirements, the slab slab has a central solid fraction of 0. The range from the position 7 to the downstream side 8 m is set as the effective rolling reduction region. In this effective rolling reduction region, one or more pairs of rolling rolls integrally formed in the axial direction with a roll diameter of 417 mm or more are arranged, and the slab A slab slab continuous casting facility characterized in that the total reduction amount to the slab is 10 mm or more.
(W / W ₀ )> 0.5 (1)
However, W ₀ (mm): pressure before the start of the slab slab thickness W (mm): steel material thickness of The continuous casting equipment for slab cast pieces according to claim 1, wherein a roll diameter of the reduction roll is 620 mm or less, and 3 to 19 pairs of the reduction rolls are arranged according to the roll diameter. The slab according to claim 1 or 2, wherein a preliminary reduction area is provided in a range of 2 m or less on both the upstream side and the downstream side of the effective reduction area, or on either the upstream side or the downstream side. Continuous casting equipment for slabs . The slab slab according to claim 3, wherein one or more pairs of reduction rolls integrally formed with a roll diameter of 417 to 620 mm are disposed in the preliminary reduction area so that the roll pitch is 620 mm or less. Continuous casting equipment. The relationship of the following formula (1) is obtained by continuously casting a slab slab having a carbon content of less than 0.03 to 0.2% by mass while being reduced by a reduction roll, and then hot rolling the obtained slab slab. In the continuous casting equipment for producing the slab cast slab used in the method for obtaining a steel material satisfying the requirements, the slab slab has a central solid fraction of 0. The range from the position 7 to the downstream side 8 m is the effective rolling reduction area, and in this effective rolling area, one or more pairs of rolling rolls having a roll diameter of 380 mm or more and divided in the axial direction are arranged, and a slab slab A continuous slab casting facility for slab slabs , wherein the total reduction amount of the slab is 10 mm or more.
(W / W ₀ )> 0.5 (1)
However, W ₀ (mm): pressure before the start of the slab slab thickness W (mm): steel material thickness of The roll diameter of the rolling roll is 620 mm or less, and the rolling roll is a continuous casting facility for slab cast pieces according to claim 5, wherein 3 to 20 pairs of rolling rolls are arranged according to the roll diameter. The slab according to claim 5 or 6, wherein a preliminary reduction area is provided in a range of 2 m or less on both the upstream side and the downstream side of the effective reduction area, or on either the upstream side or the downstream side. Continuous casting equipment for slabs . The slab casting according to claim 7, wherein one or more pairs of reduction rolls having a roll diameter of 380 to 620 mm and divided in the axial direction are arranged in the preliminary reduction area so that the roll pitch is 620 mm or less. Single piece continuous casting equipment. The relationship of the following formula (1) is obtained by continuously casting a slab slab having a carbon content of less than 0.03 to 0.2% by mass while being reduced by a reduction roll, and then hot rolling the obtained slab slab. In the continuous casting equipment for producing the slab cast slab used in the method for obtaining a steel material satisfying the requirements, the slab slab has a central solid fraction of 0. The range from the position of 7 to the downstream side 8 m is set as the effective rolling reduction area. In this effective rolling area, one or more pairs of rolling rolls having a roll diameter of 280 mm or more and divided in the axial direction are arranged, and a slab slab A continuous slab casting facility for slab slabs , wherein the total reduction amount of the slab is 10 mm or more.
(W / W ₀ )> 0.5 (1)
However, W ₀ (mm): pressure before the start of the slab slab thickness W (mm): steel material thickness of The roll diameter of a reduction roll is 620 mm or less, and this reduction roll is a continuous casting equipment of the slab cast piece of Claim 9 which arrange | positions 3-20 pairs according to a roll diameter. The slab slab according to claim 10, wherein a preliminary reduction area is provided in a range of 2 m or less on both the upstream side and the downstream side of the effective reduction area, or on either the upstream side or the downstream side. Continuous casting equipment. 12. The slab casting according to claim 11, wherein one or more pairs of rolling rolls having a roll diameter of 280 to 620 mm and divided into three in the axial direction are arranged in the rolling reduction area so that the roll pitch is 620 mm or less. Single piece continuous casting equipment.

Images