JP6098577B2 - Method for adjusting roll interval of continuous casting machine and method for continuous casting of steel slab - Google Patents

Description

  The present invention relates to a method for adjusting a roll interval of a continuous casting machine and a method for continuously casting a steel piece in a continuous casting machine for casting a steel piece.

In steel slabs such as slabs cast by continuous casting machines, internal defects due to segregation of component elements (center segregation) at the center of the slab and shrinkage holes (center porosity) caused by solidification shrinkage are considered to be quality problems. Become.
One method for preventing internal defects in the steel slab is a casting method using a light reduction method in which the slab at the end of solidification is squeezed in the thickness direction. In the light reduction method, the roll interval, which is the interval between the upper roll and the lower roll at the end of solidification, is gradually narrowed. At this time, by making the reduction gradient, which is the ratio of the reduction amount of the slab to the length in the casting direction, an amount capable of suppressing the movement of the concentrated molten steel at the end of solidification, it prevents the occurrence of center segregation and center porosity. (For example, refer to Patent Document 1 and Patent Document 2).

  In the light rolling method described above, it is necessary to compensate the roll interval with high accuracy in order to surely obtain a desired rolling gradient. However, in the case of a continuous casting machine capable of changing the thickness of the slab, since the amount of increase / decrease in the roll interval when changing the thickness varies, the roll interval after the thickness change cannot be compensated with high accuracy. For this reason, after changing a roll space | interval, measuring a roll space | interval using the measuring apparatus provided in the dummy bar, the measuring apparatus provided in the roll axial part, etc., and adjusting a roll space | interval again is performed. For example, see Patent Document 3 and Patent Document 4).

JP-A 49-1217388 JP 2008-260056 A JP 58-81545 A JP 2010-240727 A

However, in the roll interval adjusting methods described in Patent Documents 3 and 4, the adjustment is performed by providing a reference range for the average roll interval in each roll interval or a roll segment composed of a plurality of rolls. At this time, in order to ensure the target rolling gradient, it is necessary to narrow the reference range of the roll interval. In the adjustment of the roll interval, after the adjustment is performed once, the roll interval is measured again. If the roll interval is further out of the reference range, the adjustment and measurement processes are repeated. For this reason, when the reference range is narrow, it takes a long time to adjust the roll interval.
Then, this invention is made paying attention to said subject, and provides the roll space | interval adjustment method of a continuous casting machine and the casting method of a steel piece which can shorten the time concerning adjustment of a roll space | interval. It is an object.

In order to achieve the above object, a method for adjusting a roll interval according to an aspect of the present invention includes a plurality of roll segments arranged side by side in a casting direction, and each roll segment is opposed to a cast piece to be cast. In the continuous casting machine having a plurality of roll sets that can change the first roll interval, which is the distance between the rolls of the roll set, the first time at the same time when the dummy bar is inserted after the width changing operation of the continuous casting machine measuring a roll nip, from the measurement result of the first roll nip, the second for calculating a second roll gap is the average of two or more rolls of pairs of the first roll gap in the roll segment A roll interval calculating step, a rolling gradient calculating step of calculating a rolling gradient from the second roll interval of two adjacent roll segments, and if the rolling gradient is less than the reference rolling gradient, Among the segments, a first roll interval increase / decrease calculation step for calculating the roll interval increase / decrease amount of the roll segment whose second roll interval exceeds the first reference, and the first roll interval according to the roll interval increase / decrease amount. possess the roll clearance adjusting step of increasing or decreasing, the first criterion is set such reduction gradient of the roll segment of two adjacent is the reference pressure gradient above, the roll segment of two adjacent second When determining whether the second roll interval exceeds the first reference in the first roll interval increase / decrease amount calculation step. , Whether the absolute value of the difference between the second roll interval and the second roll interval set value exceeds the first reference value, or whether the second roll interval is outside the first reference range And the rolling gradient is greater than the reference rolling gradient. If it is, not adjusted first roll nip.
Moreover, the roll space | interval adjustment method which concerns on 1 aspect of this invention has several roll segments provided along with the casting direction, and each roll segment has several roll groups which oppose on both sides of the cast piece to be cast. In a continuous casting machine having a first roll interval that is a distance between rolls of a roll set, the first roll interval is measured simultaneously with the insertion of the dummy bar after the width changing operation of the continuous caster. A second roll interval calculating step for calculating a second roll interval, which is an average value of the first roll intervals of two or more roll sets in the roll segment, from the measurement result of the step and the first roll interval; A rolling gradient calculating step of calculating a rolling gradient from the second roll interval between two adjacent roll segments, and when the rolling gradient is less than the reference rolling gradient, among the two adjacent roll segments, A first roll interval increase / decrease amount calculating step for calculating a roll interval increase / decrease amount of a roll segment in which the roll interval of 2 exceeds the first reference, and when the reduction gradient is less than the reference reduction gradient, the reduction gradient is the reference reduction gradient Two adjacent roll segments that are less than two adjacent roll segments and other two adjacent roll segments that have a rolling gradient greater than or equal to the reference rolling gradient, and two adjacent rolls that have a rolling gradient greater than or equal to the reference rolling gradient When the second roll interval of at least one of the segments exceeds the second reference, the second roll interval increase / decrease amount calculation for calculating the roll interval increase / decrease amount of the roll segment whose second roll interval exceeds the second reference. The first roll interval increase / decrease amount calculation step and the second roll interval increase / decrease amount calculation step. A roll interval adjusting step for increasing or decreasing the interval, and the first reference is set so that the rolling gradient of the two adjacent roll segments is equal to or greater than the reference rolling gradient. The first reference value or the second reference range of the second roll interval, and the second reference is a second reference value that is larger than the first reference value or a second reference value that is wider than the first reference range. When determining whether the second roll interval exceeds the first reference in the first roll interval increase / decrease calculation step, the second roll interval and the second roll interval It is determined whether the absolute value of the difference from the set value exceeds the first reference value, or whether the second roll interval is outside the first reference range, and the second roll interval increase / decrease amount is calculated. When judging whether or not the second roll interval exceeds the second reference in the process Determining whether or not the absolute value of the difference between the second roll interval and the second roll interval set value exceeds the second reference value, or whether the second roll interval is outside the second reference range It is determined whether or not the first roll interval is not adjusted when the rolling gradient is equal to or larger than the reference rolling gradient.

Furthermore , the continuous casting method of the steel piece which concerns on 1 aspect of this invention has several roll segments provided along with the casting direction, and each roll segment has several rolls which oppose on both sides of the cast piece to cast. In the continuous casting machine having a set and capable of changing the first roll interval, which is the distance between the rolls of the roll set, after the width changing operation of the continuous caster, the first roll interval is set simultaneously with the insertion of the dummy bar. The first roll interval is adjusted using the above-described roll interval adjustment method of the continuous casting machine, and the steel piece is cast after the adjustment of the first roll interval .

  ADVANTAGE OF THE INVENTION According to this invention, the time concerning adjustment of the roll space | interval of a continuous casting machine can be shortened.

It is a conceptual diagram which shows the state at the time of casting of the continuous casting machine of 1st Embodiment. It is a conceptual diagram which shows the state at the time of dummy bar insertion of the continuous casting machine of 1st Embodiment. It is a conceptual diagram which shows the 4th and 5th roll segment of 1st Embodiment. It is a flowchart which shows the roll space | interval adjustment method of the continuous casting machine which concerns on 1st Embodiment. It is a flowchart which shows the roll space | interval adjustment method of the continuous casting machine which concerns on 2nd Embodiment.

The first and second embodiments of the present invention will be described below. In the following description of the drawings, the same parts are denoted by the same reference numerals.
<First Embodiment>
[Construction of continuous casting machine]
Prior to the description of the roll interval adjusting method of the continuous casting machine according to the first embodiment, the continuous casting machine of the first embodiment will be described with reference to FIGS. The continuous casting machine manufactures a slab having a rectangular cross section perpendicular to the longitudinal direction by cooling and solidifying the refined molten steel 7a, and cutting the slab into a desired longitudinal length. A rectangular parallelepiped steel piece 7c is manufactured. The steel piece 7c is a slab that is a material of a product such as a thick steel plate, a thin steel plate, or a shaped steel. As shown in FIGS. 1 and 2, the continuous casting machine includes a tundish 1, an immersion nozzle 2, a mold 3, a roll segment 4, a pinch roll 5, a torch 6, a transport roll 8, and a dummy bar 9. And have.

  The tundish 1 is an intermediate container that contains molten steel 7a poured from a molten steel ladle (not shown) and whose inner wall is made of a refractory. Moreover, a hole for discharging the molten steel 7a is formed at the bottom of the tundish 1. The immersion nozzle 2 is a nozzle made of a refractory material and is connected to a hole at the bottom of the tundish 1. The casting mold 3 is a metallic casting mold, and the molten steel poured through the immersion nozzle 2 is cooled by the flow of cooling water therein to form a solidified shell 7b. In addition, the mold 3 is replaced with a member whose surface facing the width direction of the slab has a different length in the thickness direction of the slab according to the thickness of the slab.

  A plurality of roll segments 4 are provided side by side in the casting direction from the lower end side of the mold 3. In the example shown in FIGS. 1 to 3, the continuous casting machine has five roll segments 4a to 4e arranged from the upstream side in the casting direction. Each roll segment 4 includes a plurality of upper rolls 41, a plurality of lower rolls 42, an upper frame 43, and a lower frame 44. The upper roll 41 and the lower roll 42 are metal rolls, and are provided to face each other with a shaft portion perpendicular to the casting direction and a cast piece that is cast in the thickness direction. Opposing upper roll 41 and lower roll 42 are provided to be separated by a distance of a first roll interval r. Further, the upper roll 41 and the lower roll 42 are respectively supported by the upper frame 43 and the lower frame 44 so that the shaft portion is rotatable about the shaft portion. Hereinafter, a pair of the upper roll 41 and the lower roll 42 facing each other is also referred to as a roll set.

The upper frame 43 is configured to be movable in the slab thickness direction by an extension device such as a cylinder (not shown) provided on the opposite side of the upper roll 41. The lower frame 44 is fixed to a building or the ground (not shown). In the continuous casting machine, the upper frame 43 moves in the thickness direction of the slab while the lower frame 44 is fixed, so that the first roll interval r is set to 4 roll segments according to the desired thickness of the slab. It is configured to be adjustable. In 1st Embodiment, the member of the surface which opposes the width direction of the slab of the casting_mold | template 3 according to the thickness of a slab is changed, and each roll set of the roll segments 4a-4e is changed according to the thickness of a slab. By adjusting the first roll interval r, a slab having a thickness of 210 to 270 mm can be manufactured.
The roll segment 4 further includes a cooling device (not shown) provided on each of the upper frame 43 and the lower frame 44. The cooling device cools the slab to a desired surface temperature and a thickness of the solidified shell 7b by spraying cooling water onto the slab.

In the example shown in FIG. 3, the fourth roll segment 4d from the upstream side in the casting direction includes five upper rolls 411d to 415d, five lower rolls 421d to 425d, an upper frame 43d, and a lower frame 44d. Have. Opposing upper rolls 411d to 415d and lower rolls 421d to 425d are provided apart from each other by a first roll interval r _{(4,1) to} r _(4,5) . The fifth roll segment 4e from the upstream side in the casting direction includes five upper rolls 411e to 415e, five lower rolls 421e to 422e, an upper frame 43e, and a lower frame 44e. The upper rolls 411e to 415e and the lower rolls 421e to 422e are provided to be separated by a first roll interval r _{(5,1) to} r _(5,5) , respectively.

In the first embodiment, the first roll intervals r of the respective roll groups in the same roll segment 4a to 4e are all set to have the same value, or gradually as they become downstream in the casting direction. It is provided so as to be narrow. For example, in FIG. 3, the first roll intervals r _{(4,1) to} r _(4,5) in the roll segment 4d are all set to the same value or gradually decreased. Moreover, the 1st roll space | interval r _(5,1) -r _(5,5) in the roll segment 4e is provided by said method similarly to the roll segment 4d. In the first embodiment, the first roll interval r of each roll segment 4 is adjusted by the parallel movement of the upper frame 43 of each roll segment 4 in the thickness direction of the slab. At this time, by moving the upper frame 43, the first roll interval r of each roll set in one roll segment is adjusted by changing by the same amount.

Here, in the continuous casting machine of 1st Embodiment, casting of a slab is performed using the light reduction method. In the light reduction method, the internal quality of the steel slab 7c can be improved by reducing the slab at the casting position where the solid phase ratio at the thickness center of the slab is 50% to 80%. At this time, the 1st roll space | interval r of each roll segment 4 is set so that a rolling gradient may ensure 0.2 mm / m or more which is a standard rolling gradient. In the example illustrated in FIGS. 1 to 3, the position where the solid phase ratio at the center of the thickness of the slab is 50% to 80% corresponds to the position of the roll segment 4c to the roll segment 4e. Therefore, the rolling gradient G _(3,4) from the roll segment 4c to the roll segment 4d and the rolling gradient G _{(4, 5)} from the roll segment 4d to the roll segment 4e are 0.2 mm / m or more, respectively. Are set with a first roll interval r.

The pinch rolls 5 are five pairs of metal rolls provided facing the thickness direction of the slab, and are provided side by side downstream of the roll segment 4 in the casting direction. The pinch roll 5 moves the slab in the casting direction by pinching the slab between the pinch rolls 5 facing each other in the thickness direction of the slab and rotating around the shaft portion by a driving device (not shown).
The torch 6 is a cutting device provided downstream of the pinch roll 5 in the casting direction. The torch 6 melts the slab perpendicularly to the longitudinal direction so that the length of the steel piece 7c in the longitudinal direction becomes a desired length.

The transport roll 8 is a metal roll, and a plurality of transport rolls 8 are provided side by side on the downstream side of the pinch roll 5. The conveyance roll 8 conveys the steel piece 7c cut by the torch 6 to the next step by rotating around the shaft portion by a driving device (not shown).
The dummy bar 9 is a device that closes the bottom of the mold 3 at the start of casting and guides the slab to the pinch roll. In the example shown in FIG. 2, the dummy bar 9 is inserted from the downstream side of the continuous casting machine before casting is started, and when the molten steel 7a is poured into the mold 3 and casting is started, the dummy bar 9 is pulled out in the casting direction. It is. A roll interval measuring device (not shown) is provided at the tip of the dummy bar 9. The roll interval measuring device measures the first roll interval r of the roll set through which the dummy bar 9 passes when the dummy bar 9 is inserted into the continuous casting machine.

[Operation of continuous casting machine]
Next, the operation of the continuous casting machine in the first embodiment will be described. First, the member of the surface which opposes the width direction of the slab of the casting_mold | template 3 corresponding to the thickness of the slab cast is provided, and the 1st roll space | interval r of each roll segment 4a-4e is set according to the thickness of a slab. The width changing operation to be adjusted is performed.
Next, as shown in FIG. 2, the dummy bar 9 is inserted from the downstream side in the casting direction of the continuous casting machine. At this time, the first roll interval r in all roll groups is measured by the roll interval measuring device provided at the tip of the dummy bar 9. The dummy bar 9 is inserted until the tip of the dummy bar 9 is in a position to close the bottom of the mold 3.
Further, it is determined from the measurement result of the roll interval measuring device whether or not the first roll interval r needs to be adjusted. When adjustment of the 1st roll space | interval r is required, the 1st roll space | interval r is adjusted with the adjustment method mentioned later. On the other hand, when it is not necessary to adjust the first roll interval r, casting is started.

When casting is started, molten steel 7a that has been refined in advance is poured into the tundish 1. Further, the molten steel 7 a is poured from the tundish 1 into the mold 3 through the immersion nozzle 2. In the mold 3, the molten steel 7 a is cooled, so that a solidified shell 7 b is formed on the contact surface with the mold 3.
Thereafter, the slab formed with the solidified shell 7b is cooled by the roll segments 4a to 4e while moving in the casting direction, so that the thickness of the solidified shell 7b is increased, and finally the unsolidified region in the slab. All solidify.
Next, the slab is cut with the torch 6 to produce a steel piece 7c having a desired length in the casting direction. The steel piece 7c is transported to the next process by the transport roll 8.

[How to adjust the roll interval]
Next, with reference to FIG. 4, the roll interval adjusting method according to the first embodiment will be described in detail. The roll interval adjusting method according to the first embodiment is performed after the width changing operation before casting.
First, in step S100, the dummy bar 9 is charged from the downstream side of the continuous casting machine. Simultaneously with the loading of the dummy bar 9, the roll interval measuring device measures the first roll interval r of each roll set.

Next, in step S102, a second roll interval R is calculated. The 2nd roll space | interval R is an average value of the 1st roll space | interval r in each roll segment 4, and is calculated by the following (1) formula. In the formula (1), the second roll interval R _(x) in the x-th roll segment 4 from the upstream side of the continuous casting machine is shown. The x-th roll segment 4 is provided with n pairs of upper rolls 41 and lower rolls 42. In the formula (1), the first roll interval r _{(x, i)} is the distance between the upper roll 41 and the lower roll 42 in the i-th roll set from the upstream side of the x-th roll segment 4.

  Further, in step S104, a reduction gradient G in the light reduction region is calculated. The lightly reduced region is a region where the slab is lightly reduced in the thickness direction, and is a casting position where the solid phase ratio at the thickness center of the slab is 50% to 80%. In the light reduction region, the first roll interval r of each roll set is set to be smaller than the interval corresponding to the solidification and thermal contraction of the slab. In the first embodiment, the lightly reduced area is an area divided into four roll segments. That is, the lightly reduced region is a region of a plurality of roll segments 4 including a casting position where the solid phase ratio at the thickness center of the slab is 50% to 80%.

The rolling gradient G indicates the amount of rolling of the two adjacent roll segments 4 with respect to the unit distance in the casting direction. The reduction gradient G is calculated between the two adjacent roll segments 4 using the following equation (2). The expression (2) shows the rolling reduction gradient G _{(x, x + 1)} in the two roll segments 4 from the upstream side of the continuous casting machine. M _(x) and M _{(x + 1} ) in the equation (2) indicate distances in the continuous casting machine from the meniscus to the center position in the casting direction of each roll segment 4 in the x-th and x + 1-th roll segments 4, respectively.

The reduction gradient G is calculated between at least one roll segment according to the number of roll segments 4 in the light reduction region. For example, in the example of the continuous casting machine shown in FIGS. 1 and 2, the light reduction region corresponds to the roll segment 4c to the roll segment 4e. Therefore, the rolling gradient G _{(3,4) in} the roll segment 4c and the roll segment 4d and the rolling gradient G _{(4, 5)} in the roll segment 4c and the roll segment 4d are calculated.

After step S104, it is determined in step S106 whether or not all the rolling gradients G are equal to or higher than the reference rolling gradient. The reference rolling gradient is a rolling gradient required for light rolling, and is 0.2 mm / m in the first embodiment.
When it is determined in step S106 that all the rolling gradients G are equal to or greater than the reference rolling gradient, the first roll interval r is not adjusted and the process ends, and then casting is started.

On the other hand, if it is determined in step S106 that at least one of the rolling gradients G is less than the reference rolling gradient, the dummy bar 9 is pulled out in step S108.
Next, in step S110, the roll interval increase / decrease amount of at least one roll segment 4 in which the second roll interval R exceeds the first reference among the two adjacent roll segments 4 where the reduction gradient G is less than the reference reduction gradient. Is calculated. Judgment whether more than a first reference, the absolute value of the difference between the second roll gap R and the second roll gap set value _{R a (x) A (x} ) is the first reference value It is judged by whether or not it is larger than 0.05 mm. In Step S110, first, for two adjacent roll segments 4 where the rolling gradient G is less than the reference rolling gradient, the second roll interval R of each roll segment 4 and the second roll interval setting of each roll segment 4 are set. The absolute value A _(x) of the difference from the value R _{a (x)} is calculated by the following equation (3). Equation (3) shows the absolute value A _(x) of the difference of the xth roll segment 4 from the upstream side of the continuous casting machine.

After the absolute value A _(x) is calculated, it is determined whether or not the absolute value A _(x) is greater than the first reference value 0.05 mm. When the absolute value A _(x) is larger than the first reference value as a result of the determination on the absolute value A _(x) , the second roll interval R _(x) and the second roll interval set value R _{a (x The} roll interval increase / decrease amount is calculated using the absolute value A _(x) so that there is no difference from the difference between That is, when the second roll interval R _(x) is smaller than the second roll interval set value _{Ra (x)} , the second roll interval R _(x) increases by the absolute value A _(x) . The value is the roll interval increase / decrease amount. On the other hand, when the second roll interval R _(x) is larger than the second roll interval set value _{Ra (x)} , the second roll interval R _(x) is decreased by the absolute value A _(x) . The value is the roll interval increase / decrease amount. The absolute value _{A (x)} result of the determination for, when the absolute value _{A (x)} is 0.05mm or less, roll distance increment or decrement is zero.

  After step S110, in step S112, the first roll interval r is adjusted according to the roll interval increase / decrease amount. In the first embodiment, the first roll interval r of each roll set is adjusted by moving the upper frame 43 by the roll interval increase / decrease amount calculated in step S110. After step S112, a series of processing from step S100 to step S108 is performed, and the same processing is repeated until all the rolling gradients G in the light rolling region are equal to or higher than the reference rolling gradient.

[Effect of the first embodiment]
The effects of the first embodiment will be described below.
(1) The roll interval adjusting method according to the first embodiment is based on the measurement result of the first roll interval r in a continuous casting machine capable of changing the first roll interval r which is the distance between the rolls of the roll set. A second roll interval calculation step (S102) for calculating a second roll interval R, which is the roll interval in the roll segment 4, and the second roll interval R between the two adjacent roll segments 4 are calculated. When the rolling gradient calculating step (S104) to be performed and the rolling gradient G is less than the reference rolling gradient, of the two adjacent roll segments 4, the second roll interval R of the roll segment 4 that exceeds the first reference First roll interval increase / decrease calculation step (S110) for calculating the roll interval increase / decrease amount, and roll interval adjustment step (S1) for increasing / decreasing the first roll interval r according to the roll interval increase / decrease amount. With 2) and.

  Here, in the roll interval adjusting methods described in Patent Documents 3 and 4, the adjustment of the first roll interval r is determined for each roll segment 4 from the measurement result of the first roll interval r. For this reason, in order to secure the reduction gradient G required for light pressure, it is necessary to narrow the reference range of the first roll interval r. Further, if the reference range is widened due to concerns about the lengthening of the adjustment time due to the narrow reference range, there may be a case where the required rolling gradient G cannot be obtained. On the other hand, the roll interval adjusting method according to the first embodiment determines whether or not the first roll interval r is adjusted based on the rolling gradient G. Since the roll interval adjusting method according to the first embodiment only needs to ensure the necessary rolling gradient G, internal defects can be reduced even if the reference range of the first roll interval r is widened. it can. For this reason, the time required for adjusting the first roll interval r can be shortened.

(2) The reference rolling gradient is 0.2 mm / m, and the thickness of the cast slab is 210 mm or more and 270 mm or less. According to the said structure, when the thickness of a slab is 210 mm or more and 270 mm or less, the rolling-down gradient G required in order to reduce an internal defect can be ensured.
(3) The method of continuous casting of steel slabs according to the first embodiment is the measurement of the first roll interval r in a continuous casting machine capable of changing the first roll interval r, which is the distance between the rolls of the roll set. A second roll interval calculation step (S102) for calculating a second roll interval R which is a roll interval in the roll segment 4 from the result, and a rolling reduction gradient G from the second roll interval R of two adjacent roll segments 4 The rolling gradient calculating step (S104) for calculating the roll segment, and when the rolling gradient G is less than the reference rolling gradient, the roll segment in which the second roll interval R exceeds the first reference among the two adjacent roll segments 4 The first roll interval increase / decrease calculation step (S110) for calculating the roll interval increase / decrease amount of 4 and the roll interval adjustment step (S1) for increasing / decreasing the first roll interval r according to the roll interval increase / decrease amount. With 2) a casting step of casting the billet 7c after roll clearance adjusting step.
According to the above-described configuration, since a reduction gradient necessary for light reduction can be reliably obtained, a steel piece with few internal defects can be cast, and the time required for adjusting the first roll interval r can be shortened. Can do. For this reason, the productivity of the steel piece 7c can be improved.

<Second Embodiment>
[How to adjust the roll interval]
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment differs from the first embodiment in the roll interval adjustment method, but the other configurations and operations are the same. Therefore, only the roll interval adjusting method different from the first embodiment will be described below.

In the roll interval adjusting method according to the second embodiment, first, in step S200, the dummy bar 9 is charged from the downstream side of the continuous casting machine. Step S200 is the same as step S100.
Next, in step S202, the second roll interval R is calculated. Step S202 is the same as step S102.
Further, in step S204, a reduction gradient G in the light reduction region is calculated. Step S204 is the same as step S104.
Thereafter, in step S206, it is determined whether or not all the rolling gradients G are equal to or greater than the reference rolling gradient. Step S206 is the same as step S106.
If it is determined in step S206 that all the rolling gradients G are equal to or greater than the reference rolling gradient, the first roll interval r is not adjusted and the process ends, and then casting is started.

On the other hand, if it is determined in step S206 that at least one rolling gradient G is less than the reference rolling gradient, the dummy bar 9 is pulled out in step S208.
Next, in step S210, two adjacent roll segments 4 on the most upstream side in the casting direction are selected from the roll segments 4 in the light reduction region. In the example illustrated in FIGS. 1 and 2, the two most upstream roll segments 4c and 4d are selected from the roll segments 4c to 4e in the lightly squeezed region.

Further, in step S212, it is determined whether or not the rolling gradient G of the two roll segments selected immediately before is greater than or equal to the reference rolling gradient.
If the reduction gradient G is less than the reference reduction gradient as determined in step S212, the roll of at least one roll segment 4 in which the second roll interval R exceeds the first reference in the two roll segments 4 in step S214. An interval increase / decrease amount is calculated. Step S212 is the same as step S110.

On the other hand, if the reduction gradient G is greater than or equal to the reference reduction gradient in the determination in step S212, it is determined in step S216 whether or not the second roll interval R between the two roll segments 4 exceeds the second reference. Is done. Determined whether more than a second criteria, (3) the absolute value of the difference between the second roll gap R and the second roll gap set value R _{a (x)} calculated by the formula A _(x) Is greater than 0.25 mm, which is the second reference value.

If the absolute value A _(x) of at least one of the roll segments 4 is larger than 0.25 mm in the determination of step S216, the second roll interval R of the two roll segments 4 is the second reference in step S218. An increase / decrease amount of the roll interval of at least one roll segment 4 exceeding the above is calculated. The method for calculating the roll interval increase / decrease amount is the same as in step S110.
If the absolute value A _(x) of the two roll segments 4 is 0.25 mm or less after step S214 and step S218 or at the judgment of step S216, in step S220, all the roll segments 4 in the lightly rolling area are It is determined whether or not it has been selected.

  If not all the roll segments 4 in the light pressure reduction area are selected in step S220, two roll segments 4 that are one downstream from the two roll segments 4 selected immediately before in step S222. Is selected. For example, when the roll segments 4c and 4d are selected immediately before, two roll segments 4d and 4e on the downstream side for one are selected. Step S212 is performed after step S222.

  On the other hand, when all the roll segments 4 in the light pressure reduction region are selected in the determination in step S220, the roll interval is adjusted in step S224 according to the roll interval increase / decrease amount. In step S224, the roll interval is adjusted by the roll interval increase / decrease amount calculated in steps S214 and S218. After step S224, a series of operations from step S200 to step S206 is performed, and the above-described operation is repeated until all the reduction gradients G in the light reduction region are equal to or higher than the reference reduction gradient.

[Effects of Second Embodiment]
The effects of the second embodiment will be described below.
(1) The roll interval adjustment method according to the first embodiment calculates the roll interval increase / decrease amount of the roll segment 4 in which the second roll interval R exceeds the second reference in addition to the configuration of the first embodiment. A roll interval increase / decrease amount that is further calculated in the first roll interval increase / decrease amount calculation step and the second roll interval increase / decrease amount in the roll interval adjustment step. Accordingly, the first roll interval r is increased or decreased.

  According to the above configuration, in addition to the effect of the first embodiment, it is possible to reduce the influence of an error newly generated when adjustment is performed using the roll interval increase / decrease amount calculated in step S214. For example, when the first roll interval r is adjusted using the roll interval increase / decrease amount calculated in step S214 between one roll segment that is less than the reference pressure reduction gradient in step S212, the adjustment is adjacent by this adjustment. It is conceivable that the rolling gradient G between the other roll segments 4 changes. At this time, if the rolling gradient G between the other adjacent roll segments 4 is changed in a decreasing direction, there is a possibility that it may be less than the reference rolling gradient. In the second embodiment, the processing of steps S200 to S224 is repeatedly performed by providing the second reference and adjusting the first roll interval r of other roll segments 4 that are not adjusted in the first embodiment. The number of times can be reduced.

<Modification>
The first and second embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

For example, in the above embodiment, the dummy bar 9 is inserted from the downstream side in the casting direction, but the present invention is not limited to such an example. For example, the dummy bar 9 may be inserted from the upstream side in the casting direction.
Furthermore, the number of the roll segments 4 and the number of the upper rolls 41 and the lower rolls 42 in the roll segment 4 may be provided as appropriate depending on the specifications of the continuous casting machine.
Further, appropriate values may be used for the solid phase ratio condition and the reference rolling gradient of the slab to be lightly reduced depending on the specifications of the continuous casting machine, the steel type of the steel slab 7c to be cast, and the like. . Further, the first and second reference values are determined according to the specifications of the continuous casting machine, the steel type of the steel slab 7c to be cast, etc., if the first reference value is smaller than the second reference value. An appropriate value may be used as appropriate.

Furthermore, in the said embodiment, although 1st or 2nd reference value was used as 1st or 2nd reference | standard in step S110, S214, S216, S218, this invention is not limited to this example. For example, the first and second reference ranges having the upper and lower limits by the first and second reference values around the second roll interval setting value _Ra as the first and second references, respectively. It may be used. At this time, in steps S110, S214, and S216, it is respectively determined whether or not the second roll interval R exceeds the first or second reference, and the second roll interval R is in the first or second reference range. If it is outside, it is determined that the first or second criterion is exceeded.
Furthermore, in the said embodiment, although the 2nd roll space | interval R was made into the average value of the 1st roll space | interval r of all the roll groups in each roll segment 4, this invention is not limited to this example. For example, it may be an average value of the first roll intervals r of some roll sets such as the most upstream, the most downstream, and the central three roll sets in the roll segment 4.

Next, examples performed by the inventors will be described.
In the examples, the thickness of the slab at the continuous casting machine outlet side is 260 mm, the casting speed is 0.6 m / min, the width of the slab is 1900 mm, and the carbon concentration is 0.01 mass% or more and 0.30 mass% or less. The steel piece used for the thick steel plate whose manganese concentration is 0.410 mass% or more and 2.00 mass% or less was manufactured. The continuous casting machine used in the embodiment has ten roll segments 4, and the dummy bar 9 is inserted from the downstream side in the casting direction. Further, in the casting conditions of the examples, the light reduction region where the solid phase ratio at the center of the slab thickness is 50% to 80% is from the fifth roll segment 4 to the tenth roll segment 4 counting from the upstream side. It corresponds to.

  In the examples, the first roll interval r was adjusted using the roll interval adjustment method according to the second embodiment, and a steel piece was cast after the adjustment. Prior to casting, the member on the surface facing the width direction of the cast piece of the mold 3 is changed so that a cast piece having a thickness of 260 mm can be cast from the state where the cast piece just casted is 215 mm. The first roll interval r of the roll set of each roll segment 4 was changed.

Next, steps S200 to S204 were performed. In the examples, the rolling gradients were calculated for each of the five sets of two adjacent roll segments from the fifth roll segment 4 to the tenth roll segment 4 serving as a light rolling area.
Furthermore, the process of step S206 was performed. As a result of step S206, between the roll segments of the sixth roll segment 4 and the seventh roll segment 4, the rolling gradient G _{(6, 7)} is 0.15 mm / m, which is less than the reference rolling gradient of 0.20 mm / m. became. All other locations were above the reference pressure gradient.

Then, the process of step S208-S224 was performed. In an embodiment, the absolute value _{A (6)} of the difference between the 6 th second roll segment 4 of the roll gap R and the second roll gap set value _{R a (6)} was 0.03 mm. Furthermore, the seventh second roll gap R and the absolute value of the difference between the second roll gap set value _{R a (7) A (7} ) of the roll segment 4, at 0.32 mm, the second roll spacing R was wider than the second roll interval setting value _{Ra (7)} . Therefore, for the seventh roll segment 4 exceeding 0.05 mm which is the first reference, the first roll interval r was corrected to be reduced by 0.32 mm. Further, in the eighth second roll gap of the roll segment 4 R and the absolute value _A of the difference between the second roll gap set value _{R a (8) (8)} is the 0.28 mm, the second reference Beyond a certain 0.25 mm, the second roll interval R was wider than the second roll interval set value _{Ra (8)} . For this reason, the eighth roll segment 4 was modified to reduce the first roll interval r of each roll set by 0.28 mm. The other fifth, ninth, and tenth roll segments were not adjusted because they did not exceed the second standard.

  After step S224, the processes of steps S200 to S206 were performed again. In step S206, since the rolling gradient G is 0.20 mm / m or more among all the roll segments 4 of the 5th to 10th roll segments 4 that are in the light rolling region, the adjustment of the first roll interval r is completed. did. After the adjustment of the first roll interval r, steel slabs were cast, and internal defects were investigated by ultrasonic flaw detection on the thick steel plates manufactured from the manufactured steel slabs.

  As a result of investigating the internal defects of the thick steel plate, when cast immediately after changing the thickness of the slab without using the roll interval adjusting method of the present invention, the internal defect rate is 1 at an average value of 50 charges including 10 times of changing the thickness of the slab. 0.0%. On the other hand, when the roll interval adjusting method of the present invention is carried out for every slab thickness change, the average value of 52 charges including 10 slab thickness changes is 0.04% or less, and the defect rate is greatly reduced. I was able to confirm.

  In the example, the time from the start of loading the dummy bar to the end of the correction of the first roll interval r, that is, the time from the start to the end of FIG. It was. On the other hand, as a conventional method, when the roll interval is adjusted by providing only the reference range of the second roll interval R without performing the determination by the rolling gradient, the adjustment of the roll interval is completed after the dummy bar is inserted. The required time was 54 minutes on average after 10 thickness changes. In the conventional method, in order to secure a rolling gradient, the range of the second roll interval R in which the difference from the reference roll interval is less than 0.15 mm is used as the reference range, thereby tightening the reference range of the roll interval. Adjusted. Further, in the conventional method, correction was carried out for all the segments of the rolling zone where the difference from the reference roll interval was 0.15 mm or more. From the above results, it was confirmed that the roll interval adjustment time can be shortened by using the roll interval adjusting method of the continuous casting machine according to the present invention.

1: Tundish 2: Immersion nozzle 3: Mold 4, 4, 4a-4e: Roll segment 41, 411d-415d, 411e-415e: Upper roll 42, 421d-425d, 421e-425e: Lower roll 43, 43d, 43e: Upper Frames 44, 44d, 44e: Lower frame 5: Pinch roll 6: Torch 7a: Molten steel 7b: Solidified shell 7c: Steel slab 8: Conveying roll 9: Dummy bar r: First roll interval R: Second roll interval G: Rolling gradient

Claims (4)

A plurality of roll segments provided side by side in the casting direction, each roll segment having a plurality of roll sets facing each other across a cast piece to be cast, and a distance between the rolls of the roll set; In a continuous casting machine capable of changing the roll interval of 1
After the width changing operation of the continuous casting machine, the step of measuring the first roll interval simultaneously with the insertion of the dummy bar;
From the measurement results of the first roll nip, and the second roll interval calculating step of calculating the second roll spacing is the average of two or more of the roll pairs of the first roll nip in the roll segment,
A rolling gradient calculation step of calculating a rolling gradient from the second roll interval between the two adjacent roll segments;
When the rolling-down gradient is less than the reference rolling gradient, the roll interval increase / decrease amount of the roll segment in which the second roll interval exceeds the first reference among the two adjacent roll segments is calculated. Roll interval increase / decrease calculation step;
A roll interval adjustment step of increasing or decreasing the first roll interval according to the roll interval increase or decrease amount;
I have a,
The first reference is set so that the rolling gradient of the two adjacent roll segments is equal to or greater than the reference rolling gradient, and the second roll interval of the two adjacent roll segments is 1 reference value or first reference range,
When determining whether or not the second roll interval exceeds the first reference in the first roll interval increase / decrease calculation step, the second roll interval and the second roll interval set value are determined. Determining whether the absolute value of the difference between and exceeds the first reference value, or whether or not the second roll interval is outside the first reference range,
The roll interval adjustment method for a continuous casting machine , wherein the first roll interval is not adjusted when the reduction gradient is greater than or equal to a reference reduction gradient . A plurality of roll segments provided side by side in the casting direction, each roll segment having a plurality of roll sets facing each other across a cast piece to be cast, and a distance between the rolls of the roll set; In a continuous casting machine capable of changing the roll interval of 1
After the width changing operation of the continuous casting machine, the step of measuring the first roll interval simultaneously with the insertion of the dummy bar;
From the measurement result of the first roll interval, a second roll interval calculation step of calculating a second roll interval that is an average value of the first roll intervals of the two or more roll sets in the roll segment;
A rolling gradient calculation step of calculating a rolling gradient from the second roll interval between the two adjacent roll segments;
When the rolling-down gradient is less than the reference rolling gradient, the roll interval increase / decrease amount of the roll segment in which the second roll interval exceeds the first reference among the two adjacent roll segments is calculated. Roll interval increase / decrease calculation step;
In the case where the rolling gradient is less than the reference rolling gradient, the two adjacent roll segments in which the rolling gradient is less than the reference rolling gradient, and two other adjacent units in which the rolling gradient is equal to or greater than the reference rolling gradient. The second roll interval exceeds a second reference, and the second roll interval exceeds the second reference, and the second roll interval exceeds the second reference. A second roll interval increase / decrease amount calculating step for calculating a roll interval increase / decrease amount of the roll segment exceeding the second reference ;
A roll clearance adjusting step of increasing or decreasing the first roll gap according to the roll gap decrease amount calculated respectively before Symbol first roll spacing decrease amount calculation step and the second roll gap decrease amount calculation step
Have
The first reference is set so that the rolling gradient of the two adjacent roll segments is equal to or greater than the reference rolling gradient, and the second roll interval of the two adjacent roll segments is 1 reference value or first reference range,
The second reference is a second reference value larger than the first reference value or a second reference range wider than the first reference range,
When determining whether or not the second roll interval exceeds the first reference in the first roll interval increase / decrease calculation step, the second roll interval and the second roll interval set value are determined. Determining whether the absolute value of the difference between and exceeds the first reference value, or whether or not the second roll interval is outside the first reference range,
When determining whether or not the second roll interval exceeds a second reference in the second roll interval increase / decrease calculation step, the second roll interval and the second roll interval set value, Determining whether or not the absolute value of the difference exceeds the second reference value, or determining whether the second roll interval is outside the second reference range;
The roll interval adjustment method for a continuous casting machine, wherein the first roll interval is not adjusted when the reduction gradient is greater than or equal to a reference reduction gradient. The reference pressure gradient is 0.2 mm / m,
The method for adjusting a roll interval of a continuous casting machine according to claim 1 or 2, wherein a thickness of the cast piece to be cast is 210 mm or more and 270 mm or less. A plurality of roll segments provided side by side in the casting direction, each roll segment having a plurality of roll sets facing each other across a cast piece to be cast, and a distance between the rolls of the roll set; In a continuous casting machine capable of changing the roll interval of 1
After the width changing operation of the continuous casting machine, the first roll interval is measured simultaneously with the insertion of the dummy bar,
Using the roll interval adjustment method of the continuous casting machine according to any one of claims 1 to 3, the first roll interval is adjusted,
A method for continuously casting steel slabs, comprising casting steel slabs after adjusting the first roll interval .

Images