JP5742471B2 - Continuous casting method - Google Patents

Description

  The present invention relates to a continuous casting method for suppressing component segregation that occurs at the center of a slab during continuous casting.

  In the solidification process of continuous casting, volume shrinkage (also referred to as solidification shrinkage) occurs, and accompanying this shrinkage, unsolidified molten steel is sucked and flows in the drawing direction of the slab. Since this unsolidified molten steel is enriched with solute elements such as C, P, Mn, and S (referred to as “concentrated molten steel”), when the concentrated molten steel flows, the solute elements solidify in the central part of the slab. Phenomenon (so-called center segregation) occurs. Factors causing the flow of concentrated molten steel at the end of solidification include slab bulging between rolls due to static pressure of molten steel and misalignment of roll alignment of slab support rolls in addition to the above-mentioned solidification shrinkage. It is done.

  This central segregation deteriorates the quality of steel products, particularly thick steel plates. For example, in line pipe materials for oil transportation and natural gas transportation, hydrogen-induced cracking occurs from the center segregation due to the action of sour gas, and the same problem occurs in offshore structures, storage tanks, oil tanks, etc. Will occur. Moreover, in recent years, the use environment of steel materials is often required to be used in a severe environment such as a lower temperature or a more corrosive environment, and the importance of reducing the center segregation of the slab is increasing.

  Therefore, many countermeasures for reducing or detoxifying the center segregation of the slab have been proposed from the continuous casting process to the rolling process. For example, in order to improve the center segregation, it is known that light reduction at the end of solidification in which a continuous cast slab having an unsolidified portion is reduced is effective. In the light reduction at the end of solidification, a reduction roll is arranged near the solidification completion position of the slab, and the slab during continuous casting is gradually reduced by a reduction amount corresponding to the solidification shrinkage amount by this reduction roll. The center segregation of the slab is suppressed by suppressing the formation of voids at the center and the flow of concentrated molten steel.

  Under this light pressure at the end of solidification, if the amount of reduction is insufficient, the prevention of center segregation and internal defect generation is insufficient. On the other hand, if the amount of reduction is too large, internal cracks occur and the quality of the slab is deteriorated. Therefore, it is important to control the amount of reduction within an appropriate range under the light pressure at the end of coagulation. For this reason, conventionally, the light reduction segment is continuously monitored during operation to determine whether or not the reduction amount is within an appropriate range. And based on this determination result, operation which changes the operation condition in a continuous casting process was performed (refer to patent documents 1 to 3).

JP-A-8-132203 JP 2005-193265 A JP 2008-119726 A

However, in the conventional method for determining the light reduction amount, when an excessive load is applied to the light reduction segment, it has not been possible to determine whether the light reduction amount is within an appropriate range. For example, when the solidification completion position fluctuates, the ratio of the solidified portion of the slab increases in the lightly pressed segment, and a load exceeding the load resistance set for the column support may be applied. In that case, the elastic mechanism installed at the top of the column functions to protect the segment, but even if this elastic mechanism is functioning, there is a need for a method of determining the light reduction that can be performed appropriately. It was.

  The present invention has been made in view of the above problems, and its purpose is to determine whether or not the amount of light reduction is within an appropriate range even when an excessive load is applied to the light reduction segment. An object of the present invention is to provide a continuous casting method for reducing the center segregation of a slab.

  In order to solve the above-mentioned problems and achieve the object, the continuous casting method according to the present invention measures the amount of displacement of a column supporting a frame holding a pair of rolling rolls for lightly rolling the cast slab. A step of measuring a displacement amount of the elastic mechanism in an elastic mechanism provided in the support column in order to protect the lightly reduced segment from an excessive load, and a load applied to the slab by the lightly reduced segment is less than a predetermined value. In some cases, the strut determination step for determining whether or not the light reduction amount is within an appropriate range based on the amount of displacement of the strut; and when the load applied to the slab by the light reduction segment is equal to or greater than a predetermined value, the elastic mechanism An elastic mechanism determination step for determining whether or not the light reduction amount is within an appropriate range based on the displacement amount, and a step for changing the operating conditions of continuous casting based on the determination result. The features.

  According to the continuous casting method of the present invention, even when an excessive load is applied to the lightly reduced segment, it is determined whether or not the amount of light reduction is within an appropriate range, and the center segregation of the slab is reduced. Can do.

FIG. 1 is a schematic view showing a continuous casting machine to which a continuous casting method according to an embodiment of the present invention is applied. FIG. 2 is an enlarged schematic view of a light reduction segment in a continuous casting machine. FIG. 3 is a cross-sectional view of the lightly pressed segment in a plane perpendicular to the transport direction. FIG. 4 is a graph showing a stiffness curve of a lightly pressed segment according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a method for determining a light reduction amount of a light reduction segment according to an embodiment of the present invention. FIG. 6 is a table of measurement data obtained by measuring the center segregation degree in the slab cast by the continuous casting method according to the embodiment of the present invention. FIG. 7 is a table of measurement data obtained by measuring the degree of center segregation in a slab cast by the continuous casting method according to the embodiment of the present invention. FIG. 8 is a graph in which the relationship between the light pressure gradient and the disc spring displacement gradient is represented by a position on the coordinate plane, and the center segregation degree is represented by the size of a point. FIG. 9 is a graph showing the relationship between the upstream disc spring displacement and the downstream disc spring displacement as a position on the coordinate plane, and the center segregation degree as a point size. FIG. 10 is a graph in which the relationship between the light pressure gradient and the column displacement gradient is represented by a position on the coordinate plane, and the center segregation degree is represented by a point size. FIG. 11 is a graph showing the relationship between the upstream column displacement and the downstream column displacement as a position on the coordinate plane, and the center segregation degree as a point size.

  Hereinafter, a continuous casting method according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a continuous casting machine 1 to which a continuous casting method according to an embodiment of the present invention is applied. As shown in FIG. 1, a continuous casting machine 1 according to an embodiment of the present invention gradually adds a tundish 3 into which molten steel 2 is injected and molten steel 2 poured from the tundish 3 through an immersion nozzle 4. A copper mold 5 to be cooled and a plurality of rolls for transporting a semi-solid cast slab 6 drawn from the mold 5 are provided.

  The plurality of rolls provided in the continuous casting machine 1 have various uses depending on where they are arranged. For example, what is arranged in the vicinity of the mold 5 is called a drawing roll for use in extracting the slab 6 from the mold 5, and the object for supporting the slab 6 is called a slab support roll. In particular, the roll near the end of solidification at the position where the slab 6 solidifies to the center (so-called crater end) is called a reduction roll 7 for lightly reducing the slab 6. The reduction roll 7 is unitized into a plurality of segments, and each segment includes a mechanism for lightly reducing the slab 6. Hereinafter, this segment is referred to as a lightly pressed segment 8.

  FIG. 2 is an enlarged schematic view of the light reduction segment 8 in the continuous casting machine 1, and FIG. 3 is a cross-sectional view of the light reduction segment 8 in a plane perpendicular to the conveyance direction of the slab 6. As shown in FIGS. 2 and 3, the light reduction segment 8 includes a plurality of upper reduction rolls 7 a and a lower reduction roll 7 b that apply a pressing force to the slab 6 from above and below, and a plurality of upper reduction rolls. The upper frame 10a and the lower frame 10b that hold the 7a and the lower side pressure-reducing roll 7b via the hydraulic cylinder 9, and the two arranged on the upstream process side for supporting the upper frame 10a and the lower frame 10b substantially in parallel An upstream column 11a and two downstream columns 11b disposed on the downstream process side.

  As described above, each of the plurality of reduction rolls 7 is fixed to the upper frame 10a or the lower frame 10b via the hydraulic cylinder 9, so that the upper reduction roll 7a can be expanded and contracted independently by expanding and contracting the hydraulic cylinder 9. And the lower side roll 7b can be controlled independently. In particular, it is possible to set a so-called light rolling gradient in which the interval between the rolling rolls 7 on the upstream process side is set wider than the spacing between the rolling rolls 7 on the downstream process side.

  The upper frame 10a and the lower frame 10b apply loads to the slab 6 from above and below via the upper roll 7a and the lower roll 7b. Since the upper frame 10a and the lower frame 10b are supported by the upstream column 11a and the downstream column 11b, the upstream column 11a and the downstream column 11b are lightly applied to the slab 6 as the light pressure lower segment 8 as a whole. Specify the amount of reduction.

  A disc spring 12 as an elastic mechanism is installed on the upper side of the support column 11a and the downstream support column 11b in order to apply a load exceeding the load resistance set for the support column. That is, when the load is equal to or less than the predetermined load, only the upstream strut 11a and the downstream strut 11b receive the load applied to the slab 6, and when the load is equal to or greater than the predetermined load, the disc spring 12 is bent. In this configuration, the load applied to the slab 6 is received.

  FIG. 4 is a graph showing the stiffness curve of the lightly under-pressed segment 8 having two stages of stiffness by the support columns 11a and 11b and the disc spring 12 as described above. Note that the rigidity curve shown in FIG. 4 shows the relationship between the load (tonf) per column and the displacement (mm).

  As shown in FIG. 4, the lightly reduced segment 8 according to the embodiment of the present invention has a slab 6 via a reduction roll until the displacement amount of the upstream column 11 a (or the downstream column 11 b) is 1.5 mm. When the upstream strut 11a receives a load applied to the upper strut 11a and the displacement amount of the upstream strut 11a (downstream strut 11b) is 1.5 mm or more, the slab 6 is bent via the reduction roll by bending the disc spring 12. It is the structure which receives the load applied to. Further, the load when the displacement amount of the upstream column 11a (downstream column 11b) is 1.5 mm corresponds to 150 tonf. With this load as a threshold, the displacement amount of the upstream column 11a (downstream column 11b) or One of the displacement amounts of the disc spring 12 determines the load applied to the slab 6.

  Hereinafter, with reference to FIG. 5, a method for determining a light reduction amount of the light reduction segment 8 according to the embodiment of the present invention will be described.

  FIG. 5 is a schematic diagram showing a method for determining a light reduction amount of the light reduction segment 8 according to the embodiment of the present invention. As shown in FIG. 5, the control unit 13 includes a column displacement measuring unit 13a, a column displacement determining unit 13b, a spring displacement measuring unit 13c, a spring displacement determining unit 13d, and an operation condition changing unit 13e. The column displacement measuring unit 13a, the column displacement determining unit 13b, the spring displacement measuring unit 13c, the spring displacement determining unit 13d, and the operation condition changing unit 13e can also be configured as hardware, and the program executed by the control unit 13 It can also be configured as a step.

As shown in FIG. 5, the method for determining the light reduction amount of the light reduction segment 8 according to the embodiment of the present invention is based on the displacement amounts (Δx _p1 , Δx _p2 , Δy _p1) of the upstream column 11a and the downstream column 11b. (Δy _p2 ) and displacement amounts (Δx _s1 , Δx _s2 , Δy _s1 , Δy _s2 ) of the disc springs 12 provided on the upper portions of these columns are monitored. Here, lengths of the two upstream-side struts 11a (the convenience considered frame distance) and x _p1, x _p2, the amount of displacement of the x _p1, x _p2 respectively [Delta] x _p1, and [Delta] x _p2. Further, the lengths y _p1 and y _p2 of the two downstream struts 11b are set, and the displacement amounts of y _p1 and y _p2 are set to Δy _p1 and Δy _p2 , respectively. Similarly, the lengths of the disc springs 12 provided on the two upstream struts 11a are x _s1 and x _s2, and the displacement amounts of x _s1 and x _s2 are Δx _s1 and Δx _s2 , respectively. The lengths of the disc springs 12 provided on the two downstream struts 11b are y _s1 and y _s2, and the displacements of y _s1 and y _s2 are Δy _s1 and Δy _s2 respectively (see FIG. 2 and FIG. 2). (See FIG. 3). The amount of displacement of the disc spring 12 can be measured by providing a general displacement meter such as a vortex type displacement meter or a laser displacement meter at the attachment portion of the disc spring 12, and the upstream column 11a and the downstream column 11b can be measured. The amount of displacement can be measured with a laser displacement meter or the like in the vicinity of the upstream column 11a and the downstream column 11b in the upper frame 10a from the reference point outside the light pressure lower segment 8.

The column displacement measuring unit 13a calculates the displacement amounts (Δx _p1 , Δx _p2 , Δy _p1 , Δy _{p2) of the} upstream column 11a and the downstream column 11b from the output of the displacement meter related to the displacement of the upstream column 11a and the downstream column 11b. ) Is calculated. That is, the difference from the predetermined zero position is calculated from the output of the displacement meter, and the displacement amounts (Δx _p1 , Δx _p2 , Δy _p1 , Δy _p2 ) of the upstream column 11a and the downstream column 11b are calculated.

Further, the strut displacement measuring unit 13a uses the following parameters used for the light reduction amount determination condition from the displacement amounts (Δx _p1 , Δx _p2 , Δy _p1 , Δy _p2 ) of the upstream strut 11a and the downstream strut 11b: ΔX _p , ΔY _p , ΔZ _p are calculated. As can be seen from the following equation, ΔX is an average value of the displacement amount of the upstream column 11a, and ΔY is an average value of the displacement amount of the downstream column 11b.
ΔX _p = 1 / 2Δx _p1 + 1 / 2Δx _p2
ΔY _p = 1 / 2Δy _p1 + 1 / 2Δy _p2
ΔZ _p = ΔX _p −ΔY _p

The strut determination unit 13b determines whether the light reduction amount is within an appropriate range based on ΔX _p , ΔY _p , ΔZ _p calculated by the strut displacement measurement unit 13a. The determination conditions used for the determination are the following (Condition 1 _P ) and (Condition 2 _P ).
(Condition 1 _P )
ΔZ _P <1 / 40Z
(Condition _2P )
ΔX _P <1 / 40Z or ΔY _P <1 / 40Z
Here, Z is the amount of rolling reduction per segment (so-called light rolling gradient), using the interval d _in between the rolling rolls 7 on the entry side of the light rolling segment 8 and the interval d _out between the rolling rolls 7 on the exit side. , Z = d _in −d _out .

The spring displacement measuring unit 13 c calculates the displacement amount (Δx _s1 , Δx _s2 , Δy _s1 , Δy _s2 ) of the disc spring 12 from the output of the displacement meter related to the displacement of the disc spring 12. That is, the difference from the predetermined zero position is calculated from the output of the displacement meter, and the displacement amount (Δx _s1 , Δx _s2 , Δy _s1 , Δy _s2 ) of the disc spring 12 is calculated.

Further, the spring displacement measuring unit 13c uses the following parameters used for the light reduction amount determination conditions from the displacement amounts (Δx _s1 , Δx _s2 , Δy _s1 , Δy _s2 ) of the disc spring 12: ΔX _s , ΔY _s, ΔZ _s Is calculated. As can be seen from the following equation, ΔX _s is an average value of the displacement amount of the upstream disc spring 12, and ΔY _s is an average value of the displacement amount of the upstream disc spring 12.
ΔX _s = 1 / 2Δx _s1 + 1 / 2Δx _s2
ΔY _s = 1 / 2Δy _s1 + 1 / 2Δy _s2
ΔZ _s = ΔX _s −ΔY _s

The spring displacement determination unit 13b determines whether the light reduction amount is within an appropriate range based on ΔX _s , ΔY _s, ΔZ _s calculated by the spring displacement measurement unit 13a. The determination conditions used for the determination are the following (Condition 1 _s ) and (Condition 2 _s ).
(Condition 1 _s )
ΔZ _s <1 / 2Z
(Condition 2 _s )
ΔX _s <1 / 2Z or ΔY _s <1 / 2Z
Here, Z is the amount of rolling reduction per segment (so-called light rolling gradient), using the interval d _in between the rolling rolls 7 on the entry side of the light rolling segment 8 and the interval d _out between the rolling rolls 7 on the exit side. , Z = d _in −d _out .

  The operation condition changing unit 13e changes the operation condition of the continuous casting machine 1 based on the determination results by the column displacement determination unit 13b and the spring displacement determination unit 13d. As described above with reference to FIG. 4, when the light reduction segment 8 according to the embodiment of the present invention is equal to or less than a predetermined load, only the upstream column 11 a and the downstream column 11 b are interposed via the reduction roll. When the load applied to the slab 6 is received and the load is equal to or greater than a predetermined load, the disc spring 12 is bent to receive the load applied to the slab 6 via the reduction roll. Therefore, the operation condition changing unit 13e changes the operation condition of the continuous casting machine 1 based on the determination result of the column displacement determination unit 13b when the load is equal to or less than the predetermined load. Based on the determination result by the part 13d, the operating conditions of the continuous casting machine 1 are changed.

  In addition, as an example of the operation conditions of the continuous casting machine 1 changed by the operation condition changing unit 13e, cooling water for cooling the cast slab 6 or a speed at which the slab 6 is pulled out from the mold 5 can be considered. . Further, for example, the light reduction amount itself can be changed by changing the interval between the reduction rolls 7 of the light reduction segment 8.

  Hereinafter, the effect of the continuous casting method according to the embodiment of the present invention described above will be examined.

6 and 7 are tables of measurement data obtained by measuring the center segregation degree in the slab cast by the continuous casting method according to the embodiment of the present invention. The measurement method is to analyze the carbon concentration in the thickness direction at the center of the cross section of the slab, C _max is the maximum value, C ₀ is the average carbon concentration (that is, the carbon concentration in the molten steel), and C _max / C ₀ Is defined as the central segregation degree. That is, in this definition, the center segregation decreases as the center segregation degree approaches 1. Here, it is determined that the center segregation has deteriorated when the degree of center segregation is 1.1 or more.

  The apparatus used for the experiment is the same as that of the continuous casting machine 1 shown in FIG. Using this continuous casting machine 1, low carbon aluminum killed steel was cast. The cast slab had a slab thickness of 250 mm and a slab width of 2100 mm, a secondary cooling specific water amount of 1.6 L / kg, and a slab drawing speed of 1.4 m / min. As for the arrangement of the lightly under-pressed segments 8, the first to third lightly under-compressed segments 8 were respectively arranged at positions of 21 to 23 m, 23 to 25 m, and 25 to 27 m from the meniscus. There are eight reduction rolls 7 in each light reduction segment 8, and the outer diameter of the reduction roll 7 is 230 mm. Moreover, the light pressure gradient Z in one segment is 1.7 mm / seg.

  Under the above conditions, the amount of displacement of the disc spring 12 and the amount of displacement of the support 11 and the central segregation degree of the first to third lightly compressed segments 8 were measured. FIG. 6 is a table showing the relationship between the amount of displacement of the disc spring 12 and the center segregation degree, and FIG. 7 is a table showing the relationship between the amount of displacement of the support 11 and the center segregation degree. 6 and 7, only the relationship between the disc spring displacement and the center segregation degree of the second light pressure lower segment is shown for the sake of space.

As can be understood from FIG. 6, when (Condition 1 _s ) ΔZ _s <1 / 2Z and (Condition 2 _s ) ΔX _s <1 / 2Z or ΔY _s <1 / 2Z are satisfied, the center segregation degree of the slab Is lower than 1.1. On the other hand, as can be understood from FIG. 7, if (condition 1 _p ) ΔZ _p <1 / 40Z and (condition 2 _p ) ΔX _p <1 / 40Z or ΔY _p <1 / 40Z are satisfied, the center of the slab It can be seen that the degree of segregation is lower than 1.1. Therefore, considering FIG. 6 and FIG. 7 together, in the light reduction amount determination method according to the embodiment of the present invention, when the load is not more than a predetermined load, (condition 1 _p ) and (condition 2 _p ) are satisfied. When it is determined that it is within the proper range, and when the load is equal to or greater than the predetermined load, it is understood that it is sufficient to determine that the range is within the proper range when (condition 1 _s ) and (condition 2 _s ) are satisfied.

FIGS. 8 to 11 show (condition 1 _p ) ΔZ _p <1 / 40Z, (condition 2 _p ) ΔX _p <1 / 40Z or ΔY _p <1 / 40Z, (condition 1 _s ) ΔZ _s <1 / 2Z, respectively. , And (Condition 2 _s ) ΔX _s <1 / 2Z or ΔY _s <1 / 2Z.

FIG. 8 shows the relation between the light pressure lowering gradient Z and the disc spring displacement gradient ΔZ _{s in} terms of the position on the coordinate plane, and the central segregation degree in terms of the size of the measurement data satisfying (Condition 2 _s ). It is a represented graph. As seen from the graph of FIG. 8, under conditions that satisfy the (condition _{2 s) ΔX s <1 /} 2Z or ΔY _s <1 / 2Z, region that satisfies (Condition _{1 s) ΔZ s <1 /} 2Z ( It can be seen that the central segregation degree is kept low in the lower area of the broken line in the figure.

FIG. 9 shows the relationship between the upstream Belleville spring displacement ΔX _s and the downstream Belleville spring displacement ΔY _s with respect to the measurement data satisfying (Condition 1 _s ) by the position on the coordinate plane. It is a graph expressed in size. As can be seen from the graph of FIG. 9, under the condition that (Condition 1 _s ) ΔZ _s <1 / 2Z, (Condition 2 _s ) Region satisfying (Condition 2 _s ) ΔX _s <1 / 2Z or ΔY _s <1 / 2Z ( It can be seen that the center segregation degree is kept low in the L-shaped region in the figure.

FIG. 10 shows the relationship between the light pressure gradient Z and the disc spring displacement gradient ΔZ _p in terms of the coordinate plane, and the center segregation degree in terms of the size of the measurement data satisfying (Condition 2 _p ). It is a represented graph. As seen from the graph of FIG. 10, under conditions that satisfy the (condition _{2 p) ΔX p <1 /} 40Z or ΔY _p <1 / 40Z, region that satisfies (Condition _{1 p) ΔZ p <1 /} 40Z ( It can be seen that the central segregation degree is kept low in the lower area of the broken line in the figure.

FIG. 11 shows whether or not (Condition 1 _p ) ΔZ _p <1 / 40Z satisfies (Condition 2 _p ) ΔX _p <1 / 40Z or ΔY _p <1 / 40Z. It is a graph showing a mode that a segregation degree differs. The graph shown in FIG. 11 represents the relationship between the upstream column displacement ΔX _p and the downstream column displacement ΔY _p with respect to the measurement data satisfying (Condition 1 _p ) by the position on the coordinate plane, and the center segregation degree It is a graph expressed in size. As can be seen from the graph of FIG. 11, the center segregation degree is suppressed to be low in a region satisfying (condition 2 _p ) ΔX _p <1 / 40Z or ΔY _p <1 / 40Z (broken line L-shaped region in the figure). I understand.

  As described above, according to the continuous casting method according to the embodiment of the present invention, the step of measuring the displacement amount of the column supporting the frame holding the reduction roll 7 for lightly reducing the cast slab 6, The step of measuring the amount of displacement of the disc spring 12 provided on the support 11 to protect the reduction segment 8 from an excessive load, and when the load applied to the slab 6 by the light reduction segment 8 is below a predetermined value, the support 11 A column determining step for determining whether or not the light reduction amount is within an appropriate range based on the amount of displacement, and if the load applied to the slab by the light reduction segment 8 is greater than or equal to a predetermined value, based on the displacement amount of the disc spring 12 It includes an elastic mechanism determination step that determines whether or not the light reduction amount is within an appropriate range, and a step that changes the operating conditions of continuous casting based on the result of this determination, so that an excessive load is applied to the light reduction segment. Even when it is pressurized, it is determined whether or not soft reduction amount is within the proper range, it is possible to reduce the center segregation of the slab.

Since the elastic mechanism determination step determines whether or not the light reduction amount is within an appropriate range based on the determination conditions listed below, the deterioration of the center segregation of the slab 6 can be appropriately suppressed. (Condition 1 _s ) ΔZ _s <1 / 2Z, (Condition 2 _s ) ΔX _s <1 / 2Z or ΔY _s <1 / 2Z. However, ΔX _s is an average value of the displacement amount of the upstream disc spring 12, ΔY _s is an average value of the displacement amount of the downstream disc spring 12, and ΔZ _s is expressed as ΔY _s and ΔX _s . Z is the light pressure gradient of the light pressure segment 8.

Since the column determining step determines whether or not the light reduction amount is within an appropriate range based on the determination conditions listed below, it is possible to appropriately suppress the deterioration of the center segregation of the slab 6. (Condition 1 _p ) ΔZ _p <1 / 40Z, (Condition 2 _p ) ΔX _p <1 / 40Z or ΔY _p <1 / 40Z. However, ΔX _p is the average value of the displacement amount of the upstream column 11, ΔY _p is the average value of the displacement amount of the downstream column 11, and ΔZ _p is the difference between ΔY _p and ΔX _p. Z is the light pressure gradient of the light pressure segment 8.

  The embodiment to which the present invention is applied has been described above, but the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to the present embodiment.

DESCRIPTION OF SYMBOLS 1 Continuous casting machine 2 Molten steel 3 Tundish 4 Immersion nozzle 5 Mold 6 Cast piece 7 Rolling-down roll 8 Light pressure-down segment 9 Hydraulic cylinder 10 Frame 11 Post 12 Disc spring 13 Control part

Claims (3)

Measuring a displacement amount of a column supporting a frame holding a pair of reduction rolls for lightly reducing a cast slab;
Measuring the amount of displacement of the elastic mechanism in the elastic mechanism provided on the strut in order to protect the lightly pressed segment from excessive load;
When the load applied to the slab by the lightly reduced segment is less than a predetermined value that is a load resistance set on the support column, it is determined whether the light reduction amount is within an appropriate range based on the displacement amount of the support column. A strut determination step to perform,
When the load applied to the slab by the lightly reduced segment is equal to or greater than the predetermined value , an elastic mechanism determining step of determining whether the lightly reduced amount is within an appropriate range based on a displacement amount of the elastic mechanism;
Changing the operating conditions of continuous casting based on the result of the determination. 2. The continuous casting method according to claim 1, wherein the elastic mechanism determination step determines whether or not the light reduction amount is within an appropriate range based on the determination conditions listed below.
(Condition 1 _s )
ΔZ _s <1 / 2Z
(Condition 2 _s )
ΔX _s <1 / 2Z or ΔY _s <1 / 2Z
However, ΔX _s is an average value of the displacement amount of the elastic mechanism on the upstream side, ΔY _s is an average value of the displacement amount of the elastic mechanism on the downstream side, and ΔZ _s is ΔY _s and ΔX _s Z is the light pressure gradient of the light pressure segment. 3. The continuous casting method according to claim 1, wherein the column determining step determines whether or not the light reduction amount is within an appropriate range based on the determination conditions listed below.
(Condition 1 _p )
ΔZ _p <1 / 40Z
(Condition 2 _p )
ΔX _p <1 / 40Z or ΔY _p <1 / 40Z
However, ΔX _p is the average value of the displacement amount of the support column on the upstream side, ΔY _p is the average value of the displacement amount of the support column on the downstream side, and ΔZ _p is the difference between ΔY _p and ΔX _p. And Z is the light pressure gradient of the light pressure segment.

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