JPS61137659A - Method for changing ingot width - Google Patents

Abstract

PURPOSE:To absorb effectively the error for a target change quantity arising from the difference between the taper quantity in the stage of starting the width change on the short side of a casting mold under continuous casting and the target taper quantity at the end of the width change by providing a parallel moving period when the speed at the top and bottom ends of the short side are made the same during the time of the shift from the previous tilting period to the post tilting period. CONSTITUTION:The movement of the short side 1a of the casting mold is segmented to the previous tilting period when the short side is successively tilted toward the central side of the mold and the post tilting period when the short side is gradually tilted toward the counter central side of the mold in the stage of expanding or reducing the width of the ingot 4 by moving the side 1a during continuous casting. The speed increase rate alpha of the horizontal moving speed at the top and bottom ends of the short side in each period is prelimi narily determined with the permissible resistance force against the shell deformation as a parameter and the difference DELTAV in the moving speed of the top and bottom ends is deter mined by the equation. The error for the target width change quantity arising from the difference in each target taper quantity in the stage of starting the width change and at the end of the width change is absorbed by providing the parallel moving period during the time of the shift from the previous tilting period to the post tilting period in the case of changing the width while maintaining the specified speed increase rate alpha and speed differ ence DELTAV during said period, by which the exact width change of the ingot is executed in the min. time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for continuous casting of steel, and more particularly to a method for changing the width of a slab by moving the short side of the mold during continuous casting.

[Conventional technology]

In recent years, continuous casting, especially continuous casting of steel.

Continuous casting methods, in which the width of a slab is changed without stopping pouring into a mold, have been implemented in response to demands for improved operating efficiency and slab yield.

Particularly recently, a method of directly linking the continuous casting process and rolling process has been put into practical use, and the width of the slab during continuous casting can be changed according to the product sheet width. Changing technology is becoming increasingly important. When changing the slab width without stopping the operation of the continuous casting machine, it is important to make the length of the part where one width changes as short as possible and to immediately change the width to the required width. For this reason, it is necessary to increase the width change speed vyr.

To change the width of a slab in continuous casting, the short side of the mold is moved toward the center or away from the center of the mold by some method. FIG. 2 conceptually shows an example of a width changing device that fixes the long sides of the mold and moves the short sides. That is, a pair of short sides 1a and 1b are held between long sides 2a and 2b fixed to a mold vibration table (not shown).

Electric or oil field drive device 3a mounted on the short side
This device is driven by e a b Vcx and changes the width of the slab 4 without stopping casting. When increasing the speed of width change in such a device, there is an increase in the force driving the short side and an increase in the risk ratio of slab defects, which has put an upper limit on how high the speed of width change can be increased.

As for the conventional width changing method, for example, 1
Please note that the method disclosed in Japanese Patent Publication No. 60326 and Japanese Patent Publication No. 54-33772 and shown in Fig. 3 and Fig. 4 is not generally practiced.

That is, FIG. 3 explains the case of width reduction, and [
In the first step, indicated by al, the short side 1 is inclined as shown by the dotted line 3, and in the second step, it is translated in parallel as indicated by fbl, 7ti,
Next, in the third step, the method of returning the slope to its original state as shown in (C) is shown, and FIG. 4 explains the case of widening the width. This figure shows a method in which the object is tilted as shown in FIG. 1, and then translated in the second step as shown in (b), and then the inclination is reduced in the third step as shown in (c).

In other words, in the past, (a) and (c) in Figures 3 and 4
The Teno R-change operation in Figure 1 and the parallel movement operation in Figure 1 were performed completely separately.

However, in the conventional method described above, it takes too much time to change the width, and even if the parallel movement speed 1)i-Vm'i is increased, the effect of reducing the length of the width change transition part is very small, which hinders yield improvement. Become a friend.

In order to solve the above problem, various attempts have been made to further increase the translation speed Vm. However, in order to increase the parallel movement speed Vmf without breaking the solidified shell (#solid shell) in the remaining mold and by overcoming the deformation resistance force of this shell, it is necessary to The inclination change angle Δφ must be increased.

On the other hand, when the inclination change angle Δφ is increased, a gap, ie, a feed gap, is created between the short side 1 and the slab 4, and when this air gap becomes large, the slab 4! There are problems such as /c cracking and breakout. Therefore, in the conventional method, there is a limit to increasing the parallel movement speed FiiVmf, and there is a limit to shortening the width change time. In order to solve this problem, the present applicant developed a method of simultaneously moving the upper and lower ends of the short sides in the first step and the third step to shorten the required time for these steps, which was first proposed in Japanese Patent Application No. 57 -184103 and Japanese Patent Application No. 58-143157.

However, this method also uses parallel movement as the basic idea 4, and although it is possible to make the time to reach parallel movement as fast as possible, it still shortens the total time required to change the width. There was a limit to what I could do.

[Problem that the invention seeks to solve]

The present invention is intended to fundamentally solve the problems of the nine conventional methods mentioned above, and to further improve the aforementioned Japanese Patent Application No. 57-184103 and Japanese Patent Application No. 58-143157. By making the width change to expand or contract in the minimum time, it reduces the width change part to improve the yield, and it is stable without the occurrence of casting defects such as breakouts (hereinafter referred to as BO) and slab cracks. In addition, the error in the target width change caused by the difference in the amount of tape before and after the width change is started and finished is efficiently absorbed by the actual width change, and the accurate slab width is ensured. This provides a method for obtaining

[Means for solving problems]

The present invention provides a forward tilting period in which the movement of the short side is sequentially tilted toward the short side tl - the center of the mold, and The acceleration rate α of the horizontal movement speed of the upper and lower ends of the short side in each period is determined in advance using the allowable shell deformation resistance force as a parameter, and the movement speed of the upper and lower ends is determined in advance. The difference v is determined by the following formula (1), and during the relevant period.

In the method of changing the width while maintaining the speed increase rate α and the speed difference Δv constant, the target width change amount resulting from the difference between the tenor R amount at the start of one width change and the Mekeyaki tenor amount at the end of the width change. This is a method for changing the width of a slab during continuous casting, which is characterized by absorbing errors in the width of the cast slab during continuous casting by providing a parallel movement period during the transition from the forward tilting stage to the backward tilting stage.

ΔV = α fist L / Uc - (1) However, △V: Speed difference between the upper and lower ends of the short side (mm/min) α: Acceleration rate at the upper and lower ends of the short side (m/min”) L
; Mold short side length m l Uc; Casting speed 91L (s+/min) [Function] FIG. 1 shows the horizontal movement speed K (hereinafter referred to as "the horizontal movement speed K" of the upper and lower ends of the short side when changing the width according to the present invention).

This is a diagram for explaining the movement speed.

FIG. 1(,) shows width reduction, and FIG. 1(b) shows width expansion. In addition, the speed is the moving speed toward the center of the mold Kt-+
(positive), and the moving speed toward the center of the tSS type was expressed as wo- (negative).

First, the case of width reduction will be explained based on FIG. 1(a). In the figure, the broken line X indicates the moving speed (hereinafter referred to as top end speed, expressed as Vu) of the top end of the short side (referring to the position corresponding to the meniscus in the mold, hereinafter referred to as the top end of the short piece). ,fruit#! y represents the moving speed V of the lower end of the short side (the lower end of the short side refers to the lower end of the short side, and the moving speed of the lower end of the short side is hereinafter expressed as Vtt). In the process of width reduction, the short side is moved toward the center of the mold, but in the first half, the short side is tilted forward toward the center of the mold. Direct the center of the mold. Complete the backward tilt operation. Incidentally, the inclination angle of the short side during normal operation (in the present invention, the inclination angle refers to the angle between the horizontal line 2 shown by a dashed line in Fig. 5, which will be described later, and the short side 1, and hereinafter expressed as β) It is set depending on the width, casting speed, etc., and the wider the slab width, the greater the amount of teno (in the present invention, the amount of teno is the difference between the vertical line Yz passing through the lower end of the mold and the upper end shown by the two-dot chain line in Fig. 5, which will be described later). When the inclination angle β is 90 degrees, the taper amount is ±0.Hereinafter, it will be expressed as the taper amount 'ik). The amount of taper also becomes smaller.

Therefore, if the width of the slab is changed during continuous casting, the width of the slab will change before and after the change, and the inclination angle β of the short side will also change, and the amount of chi/saw will also change. It is necessary to do so. For example, if this change in taper i is performed after the width change is completed.

An operation that changes only the taper amount apart from the width change operation (
(hereinafter referred to as a taper amount correction operation), the following problem occurs.

In other words, control of one width change is very complicated and troublesome, and casting is performed with inappropriate chi/thread amounts from the end of one width change until the end of the taper lid correction operation, which can lead to slab defects. The risk of occurrence of 80% is increased. In addition, in the taper lid correction operation, if the taper amount is corrected by moving the lower end or the upper and lower ends of the mold at the same time, the target width change amount of the slab will not match the actual width change amount, and the width of the slab will change. There is a very high possibility that an error will occur.

On the other hand, it is also possible to consider a method in which the target taper amount is reached in the retrograde phase, which corresponds to the latter half of the width change based on the present invention, and the width change is finished at the 9th point, but in this method, the width is changed before the target width change amount is reached. The operation will end, resulting in an error in the actual slab width relative to the target slab width.If this error is to be corrected after the width changing operation is completed, the short side must be translated in parallel. If such parallel movement is performed, the shell deformation resistance increases (when the width is reduced) or an air gap is created (when the width is expanded), making stable continuous casting impossible.

Therefore, the present invention reduces the error to the target width change amount caused by the difference between the chi A- amount at the start of the nine-width change and the target taper amount at the end of the width change from the forward tilt period to the backward tilt period. We have succeeded in effectively absorbing this by providing a parallel movement period in which the speeds of the upper and lower ends of the short sides are the same during the transition.

The example in Fig. 1 shows two types of width change chisel turns, where the target width change amount is expressed as width change time 'pwl and 1w2, and the period from the start of the anteversion period (width change start) to the end of the anteversion period (parallel The time until the start of movement is Trl and Tr2, and the parallel movement period 'k Thr ITh! It was expressed as FIG. 5 is a schematic diagram showing the movement of the short side when the width is reduced.

During the forward tilt period, the upper end velocity Vu of the short side is changed to the lower end velocity vj
In order to make the vehicle feel as if it is constantly moving at a constant speed, the inclination angle β of the short side 1 relative to the horizontal line Z indicated by the dashed-dotted line gradually increases, and the forward tilt period increases and becomes smaller. When the center of the short side of the mold reaches approximately half of the target width change amount, parallel movement is performed to make the speed of the upper and lower ends the same, but this parallel movement period is the same as the amount of chi A at the start of width change, which will be described later. This is a short enough time to completely absorb the error in the target width change amount caused by the difference between the target width change amount and the target width change amount of ~1 at the end of the width change. After passing through the parallel movement period and transitioning to the amount of backward inclination, the inclination angle β gradually decreases by increasing the upper end vVuL and lower end velocity VAf at a constant speed, contrary to the forward inclination period, and the amount of forward inclination decreases ( In the present invention, the moving period in which the tilt angle β increases, that is, toward the center of the mold and the saw amount decreases, is referred to as a forward tilting period.
On the other hand, the movement period in which the tilt angle β decreases, that is, tilts away from the center of the mold and the saw amount increases, is defined as the backward tilt amount. ) On the other hand, the upper and lower end speeds IJjVu and V# are constant speed increases α in the amount of forward and backward tilting, that is, in the forward tilting period, they are in the positive direction.

In other words, the speed increase rate α at which the short side moving speed increases sequentially.

In addition, in the backward tilt amount, if the negative direction, that is, the positive direction of the accelerating silkworm α1 in which the short side moving speed decreases sequentially, it becomes a deceleration cycle, but in the present invention, it is unified to the accelerating rate, and it is specially differentiated. When it is necessary to express it, the sign will be used to express acceleration (e) and deceleration 1 = (→).

In addition, when referring to this collectively, it will be referred to as the acceleration rate α below. )
and the speed difference ΔV, and the amount of forward #4i and backward tilt increases with time. In FIG. 1, the speed increase rate during the forward tilt period is expressed as αl, the speed difference between the upper and lower end speeds Vu and VA is expressed as ΔvI, and the speed increase rate of the backward tilt amount to be decelerated is expressed as α2. α
21, and the speed difference between the upper and lower end speeds qVu and Vik is Δv2
．． It was expressed as Δv2t.

In addition, the speed increase rate α and speed difference ΔV during the parallel movement period are “
``Zero''.

Next, the case of width expansion will be explained based on the schematic diagrams of FIG. 1(b) and FIG. 6. In order to widen the width, contrary to the aforementioned width reduction, the short side is moved in the direction away from the center of the mold, but in the first half, the lower end speed 1fvl' (I - upper end speed vu machining is always After performing a backward tilting operation to increase the speed by a certain amount and moving by a predetermined amount, the target width change amount resulting from the difference between the tip amount at the start of the width change and the target taper amount at the end of the width change as described above. After undergoing a parallel movement period to absorb errors, the trowel performs a forward tilting amount P1 to increase the upper end vVu and the lower end speed Vl.In this case, the forward tilting period and the backward tilting amount include the upper and lower end speeds vVu, Vn. As described above, has a constant speed increase rate α and a speed difference ΔV, and the amount of forward tilt or backward tilt increases with time.

As described above, in the present invention, the speed increase rate α is determined in advance by determining the allowable shell deformation resistance as a nocerameter according to the steel type, slab size, casting speed, etc., as described later, and the upper end speed Vu and the upper end By determining the speed difference ΔV of the speed vj based on the above (1), and changing the width while maintaining it constant during the forward tilting period and the backward tilting amount, it is possible to prevent casting problems such as %BO and slab cracks. To change the width in the shortest possible time without causing defects 2! ! - The first feature, and by providing a parallel movement period during the transition from the forward tilt period to the backward tilt amount, the target width change occurs due to the difference between the taper amount at the start of the width change and the target taper amount at the end of the width change. The second feature is that errors in quantity can be effectively absorbed.

Therefore, first of all, the speed increase rate α and the speed difference Δψ
The reason why the width can be changed in the shortest possible time without causing casting defects by using as a control factor will be explained.

As mentioned above, in order to increase the speed when changing one width, it is necessary to take care not to cause defects in the F2O or the slab during the width change. In order to ensure this, no air gap is created between the slab and the short side during the entire width change implementation period.
In addition, it is important to always ensure proper pushing so that the slab is not pushed in excessively on the short side. FIG. 7 is a conceptual diagram explaining the movement of the short side and the conditions for generating the air gap, where %Xu and ), β represents the inclination angle between the above-mentioned short side and the horizontal line 2 at the time, and σ represents the inclination angle with respect to the vertical line (θ=J'-90').

Now, during the minute time dt, the upper end of the short side is dXu, and the lower end is dXu.
It is assumed that the slab moves by XA, and during this time the slab moves at a casting speed f Uc
Then, it moves downward by [Uc-dt] and becomes as shown in Fig. 7 (a
Point d at t moves to the important point, and point e moves to point 61. If the distance traveled by the short side 1 during this period is small, the above-mentioned air gap (η in Fig. 7 (at)) will occur between the short side and the slab. figure(
As shown in b), the short side between dt is (Uc・dt @
tan θ] or more. That is.

Regarding the amount of movement of the upper end of the short side and the amount of movement of the lower end, see the following (21)
, (It is sufficient if Equation 31 holds true.

dXu≧Uc1) dtetanσ□ (2) dXI/≧U
c * dt @tan & - (3) ta here
nθ can be expressed by the following equation (4) (when θ is small, tL m
cos θ = L), by dividing the above formula (21, (31) by dt and rearranging, the following (51, (6
1 Formula % Formula % Therefore, the upper end speed Vu and the upper end speed V# 2 above (
51. It has been found that if the equation (6) is set so as to always be satisfied, the width can be changed without generating the air gap η.

Next, the total amount of displacement (hereinafter referred to as the indentation amount δ below t) that any point on the slab undergoes while passing through the mold will be explained based on FIG.

The point d generated at the upper end of the short side at any time t is L /
After the Uc waiting time, it passes the lower end of the short side. At this time, if the short side is moving, the slab is deformed by the difference from the lower end position of the short side at the time T = t + L / Uc and leaves the mold. The total amount of shaping that the slab undergoes when passing through the mold, that is, the pushing amount δ can be expressed by the following equation (7).

a=XZ (t+7/Uc l −Xuftl (
7)! ; The indentation state of the slab is expressed by the vertical distance from the meniscus, the indentation amount δ, and the condition that no gap occurs as described above.

By controlling these two conditions so that they do not change with respect to the elapsed time during the width change, we found that it is possible to maintain a stable pressed state without causing casting defects. Is further research needed to satisfy the above conditions? Continue next.

In order to satisfy the above conditions, it is necessary to find Vu and VL f that simultaneously satisfy the above equations (5) to (7).

The following formulas (81, (91) and (10) are based on the above (5),
(This is an equation obtained by differentiating Equation 61 and Equation (7) with respect to time, respectively. By arranging the series of (8) to [10)t, the following equation (1) is obtained.

dVu / d t -Uc / L ・(Vu -'
II&) -0-(8)dVt/dt-Uc/L
・(Vu −Vj)−0−(91V# (t +Z/
Uc 1-Vu (tl=0-(10)dVu/d
t = (Vu (t) −Vu (t −L/Uc
)J/ (L/Uc) When the solution to the above formula (1) is expressed as a general solution formula, it becomes the following formula (12).

Vu −A at + 8 − (12) In equation (12), A and B are constants.

Further, by substituting the above equation (12) into the above (9), vb can be expressed by the following equation (13).

v7==A@t + (B-A-L/Uc) −(
13) In other words, from equations (12) and (13), in order to maintain the stable pushing state described above, Vu and V7 t-
New knowledge has been obtained that it is sufficient to set it as a linear function of the elapsed time t from the start of width change, and that Vu and vj should always be kept at a constant speed difference.

Based on this knowledge, the present inventors conducted further research on changing the width during continuous casting in actual operation, and as a result, the above (12
) and (13), it was confirmed that the above knowledge could be applied on an industrial scale by setting the constant A in equations (13) to the values determined as the allowable deformation resistance 2 pR rammeter.

In the present invention, the constant A has a value other than zero during the forward tilt period and the backward tilt period, and the ninth vu and VA are accelerated or decelerated with time. During this width change period, Vu and VA2 are accelerated or decelerated at a constant At, which is used as the speed increase rate α in the present invention. or.

The constant B in the above equations (12) and (13) is the initial speed at the start of width change at the upper end of the short side, and is j Vs if appropriately determined in advance according to one width change and the operating conditions at that time.

When the speed increase rate α is set, the speed difference between Vu and vl/ is determined by e, V from the short side length L and casting speed qUc in equation (13).
” Vu −1)= a IIL / Uc −(1
), and the above-mentioned equation (1) is obtained.

Incidentally, when the speed increase rate α is zero, Δv=O in the above equation (1), and Vu=Vb, that is, the upper and lower ends of the short side have the same speed. This results in the same state as the parallel movement in width change in the conventional method. It is true that during the parallel movement period in the conventional method, the indentation state remains stable, so no casting defects occur in this area.

Conventionally, a nine-width change/(turn) was carried out centering on this parallel movement.However, in this conventional method, as mentioned above, an inclination angle change period is required before and after the parallel movement period, and during this period There were problems such as it was difficult to secure an appropriate pushing amount and there was a limit to shortening the page width change time.The present invention solves these conventional problems by setting the acceleration rate In addition to setting the parallel movement period to a value determined from the allowable shell deformation resistance, the error in the target width change amount resulting from the difference between the turn amount before the width change starts and the target turn amount at the end of the width change is determined. It is hoped that a drastic solution will be possible by utilizing it only in the ninth stage of absorbing it.

A specific method for determining the missing acceleration rate α will be explained.

As the speed increase rate α is increased, the width change time is shortened (
However, if this value is exceeded, the slab may buckle and the shell on the surface may break, or the deformation resistance will increase and the driving force to move the short side will be insufficient, making it impossible to change the width. I'm going to growl.

As a result of repeating many experiments, the inventors found that the acceleration rate α
It was confirmed that it is possible to determine the optimal range from the allowable shell deformation resistance. The allowable shell deformation resistance force is determined either from the shell strength or from the mold strip driving force.

First, we will explain how to determine it from the strength of the slab shell.

When a machined slab is pushed into the short side of the mold, distortion occurs in the solidified shell formed on the surface of the slab. At this time, a resistance force corresponding to the strain rate is generated in the shell. However, if the resistance force exceeds the critical strength of the shell, the shell undergoes buckling deformation, resulting in casting defects. In order to avoid the occurrence of such defects, the strain rate in the strained portion f' of the shell must be lower than the critical strain rate corresponding to the shell strength. The explanation will be based on. Assuming that the minute indentation amount is t-dxig) at an arbitrary distance 4H from the upper end of the short side, and the upper end moves dXu and the lower end moves d■ during a minute time dt, the slab at the eight points minute indentation amount dME)
can be expressed by the following equation (14).

dX(Fi) = ((dX7-dXu ”I/L
) ・13+ dXu-Uc e dt IItan
θ □ (14) Therefore, the pushing amount per unit time is as follows (1
5) It can be expressed by the formula.

dxlF! l/dt = (VB -t/u)*Fi
/L+Vu -UC@tanθ By the way, the first half of the width change (in the forward leaning period when the width is reduced and in the backward leaning period when the width is expanding, Vu and VZ are f16 below as described above) can be expressed by equation (17).

Vu = ('I @t + 81 - (16)"0
1=α1・t+Bt=αI IIL/Uc
−(17) However, αl; speed increase rate B in the first half of width change
t: Initial velocity of the upper end of the short side in the first half of the width change. Also, in the second half of the width change (backward tilting period when the width is reduced, forward tilting period when the width is expanding), the following (1) 3), (19) It can be expressed as a formula.

Vu =%1) (t −Tr ) +th −(18
)VI=%・(t−Tr)
+ am = α2 − L/Uc
(19) However, the speed increase rate B2 will fail in the latter half of the α32 width change.
; Initial speed Tr at the upper end of the short side in the second half of the width change; According to the time from the start to the end of the first half, the above (
16) When formulas (17) and (17) are substituted into formula (15) and tanθ=(Xu −KA)/L is taken into account, the push-in rate for the first half is expressed as formula (20) below.

dX[Bl/d t = 81-at ・8/Uc
- (20) Similarly, the push-in rate in the second half is expressed by the following formula (20').

dXiFil/dt=82 − α weight “g2/Uc
= α1 ・Tr (20'
) (dxtg)/d of the above formulas (20) and (20')
t), one short side of which is half the width of the slab width 2W (・(
When divided by 1/2) and 2w), the strained part of the slab in the first half and second half of the width change is calculated as follows (21):
It is determined by L in equation (22).

ε+1F3) = (B, = α1 ・[ii / Uc
) ・1 /W −(21)g*(Ff) −(th
=α weight ”t/Uc=α1 ・Tr )・l/W
(22) This can be illustrated as shown in FIG. 10 and FIG. 1). 12a, Figure 10 shows the width reduction, and the first
Figure 0 (at is the first half, 1) Figure 10 (b) is the second half. Further, Fig. 1) shows the width expansion, and Fig. 1) 1al is the first half, and Fig. 1) (b) is the second half. Figure 10 and 1
) In the figure, the vertical axis is the vertical distance from the meniscus, and the horizontal axis is the strain rate ε, and α and B are determined by setting the strain rates ε at the upper and lower ends, respectively.

By the way, if the strain rate ε becomes negative (→), an air gap will occur, and if it exceeds the value, the slab will buckle, making it impossible to perform stable casting as described above. The appropriate range of should be greater than or equal to zero and less than or equal to the maximum allowable value εmax (O≦ε≦tmax).

As a result of various investigations regarding the above-mentioned tmax K, the present inventors found that ;max differs between the upper and lower parts of the slab, and by applying the values shown in Table 1 for steel types manufactured by ordinary continuous casting, It was confirmed that the function of the invention could be reliably demonstrated.

Table 1 Therefore, from the above (21) and (223 formula), the following (23) holds true for the upper end in the first half, the following (24J formula) holds true for the lower end, and similarly, the following (25) holds true for the upper end in the second half. )
, the following formula (26) holds true at the lower end.

0<Bt/W≦I+maxl (2
3) 0<(81=α1 @L/Uc) ・1/W5S
max2− (24)0 <(Bz=α2@Tr)・
1/W≦'maxt - (25) 0 < (Bz=α
2.L/Uc=αi@Trii/W≦εmaxt−(2
63 or more expressions are satisfied. In other words, the following (a)-(
Each equation of h) is found.

B1>0 (a)
Bl > α, -L/Uc
(b) Bl (We gmaxl
(C) Bl (We 2maz!+α1 *
L/Uc (d) B2≧α1・Tr
(e) B, ≧α1 *
Tr+α, @El/UC(r)B, ≦Wagmaxl
+αt fist T r(g)B2 ≦W@tmax goose +
α1sTr+α, @L/Uc
(h) Figure 12 shows the relationship between (a) to (h), distinguishing between the first half and the second half, as described above.
Figure (a) shows the first half, and Figure 12 (b) shows the second half. Furthermore, the horizontal axis represents the speed increase rate α1. α, the vertical axis is the initial speed B
l, B,. The hatched area in FIG. 12 indicates a range in which no casting defects occur, that is, a range in which the width can be changed while stable casting is continued. Therefore, the speed increase rate α1. By selecting and setting K as α: any value within the range of the hatched portion, the width change of the present invention described above can be implemented. Furthermore, 81+81 is also determined by setting the αhα value.

By the way, as mentioned above, it is required that the one-width change be carried out in as short a time as possible, and it is necessary to find the speed increase rate α that satisfies this requirement from within the range of the hatched portion. In the first half of the width reduction, both the speed increase rate α1 and the initial speed B1 are positive, and the larger the absolute value, the better. From this, point A shown in FIG. 12(a) becomes the optimal condition, that is, B, ==α1 * L/U c == W aεma
x, −(27) is sufficient. In the second half of the period, the angle of inclination that was made during normal operation in the first half of the period must be returned to its original value, so α1 s'pr==α2・(Tw −Tr J
−(28)Tw−Tr=−(α1/α2)”
T r -(29), and in order to reduce the width change time, the larger the absolute value of α2 is, the better, and the points shown by K in FIG. 12(b) are the optimal points. That is, B2==α1 *Tr=Wa gmaX2+α1 @T
It is sufficient if it is r+α2·L/Uc.

Next, K to shorten the width change time in the first half of width expansion.
The smaller the value of aIIBT, the better. Therefore, Fig. (12) (
a) Point A indicated by K becomes the optimal condition, and the initial speed B1 becomes K as shown below.

81 = O=W mg mmg+α1-L/Uc
(31) Also, in the latter half of width expansion, TW−Tr=(α1/αt l ・Tr −
In the relational expression (32), α1(O1α!〉0), so in order to reduce the width change time, the larger α is better.Therefore, the point shown in Fig. 12(b) is the optimal point, and the initial speed is B2 is as follows.

8! = CLHaTr + α * L / Uc = W @
;maxl +α1 The acceleration rate α and initial speed B are determined to minimize the width change time as described above, and Table 2 below shows them as a list.

Table 2 Upper and lower end speeds Yu, vt under the conditions of Table 2 above
is according to Table 3 (II! Reduction) and Table 4 (Width expansion) below.

From Tables 3 and 4, it is clear that when the width begins to narrow, the initial velocity B1 at the upper end of the short side is taken as the velocity difference Δv1 in the forward tilt phase.<, (Bl=ΔV, = α
1・L/Uc), in order to secure this speed difference ΔVl, it is most effective to set the initial speed at the lower end of the short side to "0" as shown in the formula below, in terms of shortening the width change time. It is.

Table 3 Table 4 Vl=Vu-(ΔVt)=(αH1ll+αs・L/Ucl-(α1-t/Uc
) = αssl + “O” Similarly, when expanding the width, set the initial velocity at the top of the short side to “0”.
It has been found that starting the width change as `` is the best way to shorten the width change time. The above-mentioned FIG. 1 shows an embodiment in which the width is changed with the initial speed at the upper end of the short side being zero when the width reduction change is started, and the initial speed at the top end of the short side is zero when the width expansion change is started.

Also, according to the experience of wood inventors, the shell thickness is thinner above the short side than below, so generally g maxl , > i maxz
(34), and in the case of width reduction α1〉αx (35
In the case of 3-width expansion, it is possible to set α1 <α snow □ (36) from the shell deformation resistance force, and it is effective from the viewpoint of increasing the width change speed. On the other hand, when it comes to town closing α2, control of the timing of transition from the forward tilt phase to the backward tilt phase becomes complicated. Therefore, when emphasis is placed on ease of control, α1
It is preferable that =α2.

Next, a case where the allowable shell deformation resistance force is determined from the capability of the short side drive device will be described. When implementing the present invention using an existing electric device, or when there is a limit to increasing the capacity of the drive device due to constraints such as the installation location or equipment costs, α, which is set from the above-mentioned shell strength, In case B, there is a possibility that the driving force is insufficient and the width cannot be changed. In such a case, the speed increase rate α and the initial speed B can be set within the above-mentioned shell strength and at which the drive device can efficiently demonstrate its capabilities.
All you have to do is ask for. Although there are various types of drive devices, a specific method for determining the acceleration rate α and the initial speed B from the cylinder capacity for a typical one-cylinder type will be described below.

The inventor conducted tests with various α and B values and found that the linear driving force F required to drive the short side of the mold is here! (1
3) is obtained by setting the speed increase rate α and the initial speed B at the upper end of the short side as shown in the equation (21) above in the first half of the width change and as shown in the equation (22) in the second half.

In addition, H is the shell thickness, which can be calculated using the following equation (38).G is the creep constant, which is given by the following equation (39).

H=Ho, (L'UC) "2 G=Go*exp(q/Be)
(39) In addition, (in formula 383, Ho is the solidification coefficient, which is usually 18 to 25 m+/m1nl in the case of ordinary steel.
/1, and strictly speaking, it is determined by measuring the shell thickness for each steel type. (37), (G o + n + q in formula 391 is a coefficient determined from the physical properties of the target spn, and can be determined by performing a tensile test for each steel type.

Furthermore, the sFi integral variable, gJ-1'', is the distance from the upper end of the short side as described above, and Re is the temperature (0K).

As shown in Fig. 13, the driving force of the upper and lower cylinders (hereinafter referred to as necessary driving force) necessary to drive the short piece is
(Required driving force of the upper cylinder) and Ft (Required driving force of the lower cylinder), Fu and FA are as follows (40)
, and (41).

Ft+=F (5o-j)LL-(40)F A=
F −F u −(41) However,
”: Distance Ll between the meniscus and the upper cylinder mounting position ff; Distance F between the upper and lower cylinders; Required total assembly force So for the upper and lower cylinders; Sequentially change α and B so that they are equal to or greater than the values found from equation (42) below. (21)゜(
22] is obtained from equation (37), and the required linear driving force F is obtained from this equation and equation (37). When this required linear driving force F is found,
The required linear driving forces Fu and Ft for each of the upper and lower cylinders are determined by equations (40) and (41). On the other hand, the ability of the upper and lower cylinders to effectively act on the slab 9 through their short sides (hereinafter referred to as cylinder capacity) is as follows (433, (4
As shown in equation 43, from the generation capacity Pa, the static pressure F of molten steel is
It is the value obtained by subtracting g and sliding friction force Fμ.

Fuu=Fa Fg−Fμ □ (43)F
LL=, Fa −Fg −Fμ (44) However, Fuu
: Upper 7 cylinder capacity Ftf; Lower cylinder capacity Fg; Molten steel static pressure acting on the short piece Fμ; Sliding friction force Therefore, Fuu>Fu, FAA) Acceleration rate α that satisfies F't, and initial speed B at the upper end of the short side , and find the speed difference ΔV between the upper and lower ends.

Next, when changing the width using the aforementioned speed increase rate α and speed difference ΔV as control factors, it is assumed that the taper amount at the start and end of the width change is the same, and from forward tilting operation to backward tilting operation, or A method for determining the timing of switching from the retroversion side to the anteversion phase will be explained.

If the taper amount at the start and end of the width change is the same, the parallel movement period is "0", that is, unnecessary.

The end of the anteversion period is the turning point at which the anteversion phase immediately begins. For example, taking width reduction as an example, as shown in FIG. 14, a forward tilting operation is performed in the first half, and a backward tilting operation is performed in the second half. The timing of switching from the forward tilting operation to the backward tilting operation may be determined by the following method.

First, if the total width change time is Tw, and the time required for the forward tilting period and the turning time J is Tr, then the inclination angle deepened to a predetermined angle from normal operation in the forward tilting phase is the same on the backward tilting side before the width change starts. It is necessary to return the angle of inclination to . From this, the following formula (45J) is established, and from this formula 45, the speed difference Δvl in the forward tilting period and the speed difference Δv snow in the backward tilting side can be calculated as follows (46), (
It can be calculated as shown in formula 473.

ΔV1*Tr+ΔV2(Tw-Tr)=0-(45
JΔV1 = α1 @L/Uc (
461ΔV, = αI IIL/Uc
-(47) In addition, αl is the speed increase rate in the forward lean phase and its direction is positive (10), and αl is the speed increase rate in the backward lean side and its direction is negative (-). (46), ( Equation 47) The above Equation (45) can be expressed as Equation (4B) below.

α1 eTr+αx ・(Tw−Tr)−0(483
Next, if the target width change amount is 2Q, then the short side on one side only needs to be moved by Q, and the following equation (49) holds true.

(1/2)=α1 ・T r” +B1 @T
r” (1/2)” Snow (Tw-Tr l” +B1
s(Tw-Tr) = Q - (49) Substituting equation [(48) into equation (49) yields (1/2J-(1+(α1
/α2 )]α1 ・Trl+[B1−(αI/αx
l・Bt]@Tr −Q=O (50) Therefore, this (
50) By solving the equation, the timing of switching from forward tilting operation to backward tilting operation, that is, Tr, is as follows (51), (52)
It can be obtained using the formula.

To α, l! When '=α2, Tr = (1/[: 1 + (αI/α2)]・α
1) φ[-+1/2)・[1+(α1/α2)]・α1
+ (CBl-(αl/α21 happiness B2) 2+2(1+(
αl/αt+〕・αs・Q)”/'〕−(51)
When α1==α2, Tr=Q, /(81+B2 J
(52'As can be seen from equation (52), if α1==αs, then Tr is simply determined as Q and Bl*s), and therefore its control becomes easy.

In addition, the full width change time Tw is as described above (481 & Tr is Tw
It is sufficient to shift from the forward tilting operation to the backward tilting operation when the target width change amount reaches 172.

As mentioned above, when α1==α, the formula (2) is very easy to achieve, so the case where α1==α2 will be explained below as a representative.

As mentioned above, since the width of the slab is different before and after changing the width, it is normal for the amount of taper to change.
In particular, if the present invention allows a large amount of width change in a short time, the change in taper amount will inevitably increase.

In the conventional width changing method, the taper amount is changed in the first and third steps shown in FIGS. 3 and 4 (2), and the operation to match the target taper amount is performed in the third step. At this time, since the taper amount is changed by moving the lower end of the short side, the width change amount increases by the difference between the taper amount during parallel movement and the target taper amount, resulting in an error. Conventionally, rounding to prevent this error has been dealt with by methods such as terminating the parallel movement quickly. However, in the present invention, since the upper and lower ends of the short sides always move at different speeds, it is difficult to absorb the error in the forward and backward tilting periods, and an effective countermeasure is required.

Next, a method will be described in which the taper amount is changed during the width change implementation process and an error with respect to the target width change amount that may occur due to the change in the taper amount is absorbed.

In relation to the amount of slab solidification shrinkage, it is common that the wider the slab width, the larger the taper amount (smaller the inclination angle β), and conversely, the narrower the slab width, the smaller the taper amount (larger the inclination angle β). known to.

Therefore, when reducing the width of the slab, the amount of taper change during the backward tilting stage will be smaller than the amount of taper change during the forward tilting stage, and if the width change is completed by correctly matching the taper amount to the target value, the width change time will be is TΔ shown in FIG. 15 and equation (54) below.
As a result, the width change amount is as follows (55)
This means that the target width change t is insufficient by ΔW shown in the equation.

T△c=l (2-cot AV
(54) Also, in the case of expanding the slab width, the amount of taper change during the forward tilting stage is smaller than the amount of taper change during the backward tilting stage, and as mentioned above, the width can be changed by correctly matching the taper amount to the target value. When the width change time is completed, the width change time is shortened by TΔ, which is the same as the formula (54), and as a result, the width change amount becomes short by ΔW shown in the following formula (561).

, -TV ΔW== Mt@at=(1/2)sa・(T
Δni l-! In addition, in the formulas (54] to (56), the target team 7 < - amount at the end of the width change is 0; the taper amount ΔV at the start of the width change; the upper and lower ends of the short side. Speed difference α; Acceleration rate at the top and bottom ends of the short side 'ILL: Movement speed Tw of the bottom end of the short side in the second half (backward tilting period when width is reduced, forward tilting period when width is expanding); Width change time (55), ( The shortage amount ΔW with respect to the target width change amount in equation 56) corresponds to the error with respect to the target width change amount resulting from the difference between the taper amount at the start of the width change and the target taper amount at the end of the width change.In the present invention, the error is The error is absorbed by performing parallel movement during the transition from the forward tilt period to the backward tilt period, and the parallel movement time required to absorb the error can be expressed by the following equation (57).

Th=ΔW/Vut(57) VuL: Moving speed of short side during parallel movement Next, an example of a specific control method for parallel movement to absorb the above error is shown in the line diagram in Fig. 16 and the block diagram in Fig. 17. The explanation will be based on the example of width reduction shown in FIG.

First, when implementing the 5-width change, the taper amount at the end of the forward tilting period is 1, and the slab width at the end of parallel movement W2 ((1/2
)X slab width) is determined based on the following equations (58) to (60).

Tr=(1/2α)((ΔV”+4α・(l ws−w
ol))'/”El=−ΔV*Tr+to o
-(r'?) -Δv)-(58)Wx=
w3 + ((1/21 ・α*(Tr”−TΔ2
)+ΔV 1)(T r −TΔ) ) −(601
w6: (Slab width before width change) Xi/2 w3; (Target slab width after width change) 0 for Xi/2; Amount of taper before width change If l and WS are obtained above, calculate in advance The forward tilting operation is started while maintaining the speed increase rate α and the speed difference ΔV constant. This forward tilting phase is carried out until the taper amount reaches lVc, and immediately after reaching lVc, the velocity of the upper and lower ends of the short sides is made the same and the movement shifts to parallel movement. The speed of the upper and lower end portions during this parallel movement period may be arbitrarily set between the upper end speed vuI of the short side at the end of the forward tilt period and the lower end speed vtl, and in this embodiment, the lower end speed vtl is set.

During the parallel movement, the slab width is W! The process continues until W2C is reached, and immediately after reaching W2C (transition to retroversion phase).

The speed increase rate during this backward leaning period is only the opposite direction to the speed increasing rate during the forward leaning period, but its absolute value is the same (1 α 1) = α 1
) Therefore, the upper end speed Vul of the short side immediately after transitioning to the backward tilting phase is the lower end speed Vtl at the end of the forward tilting phase, and the lower end speed VtS is the upper end speed Vul at the end of the forward tilting phase. The speed increase rate α and the speed difference ΔV are maintained constant during the backward tilt period. This backward tilting operation causes the taper amount to gradually return to the taper amount at the start of the width change, but when the taper amount matches the target taper amount, the width change ends at that point.

From the above, the taper amount at the end of the forward tilting period is 1, and the slab width W at the end of the parallel movement is the error caused by the aforementioned shortage ΔWK, and the error caused by the calculation process of equations (58) to (601). By setting the calculation error in consideration, the error with respect to the target width change amount can be effectively absorbed by the parallel movement during transition from the forward tilt period to the backward tilt period.

〔Example〕

The invention was carried out during the production of low carbon kt killed steel in a 350 ton/H curved continuous caster. The equipment specifications and operating conditions for this continuous casting machine are as shown in Table 5.

Table 5 First, the following example will be described in which the slab width was reduced from 1200 nyx to 1000 m. When implementing this width reduction, it is also necessary to change the taper amount from 8WR to 5th tone.

By the way, in the above explanation, the upper and lower end speeds of the short side are set at the meniscus section at the upper end and at the lower end of the short side at the lower end, and the acceleration rate α and the speed difference ΔV are calculated based on the upper and lower end speeds Vu and VL. However, when the short side is driven by the upper and lower cylinders, it is preferable from the viewpoint of drive control etc. to use the speeds of the upper and lower cylinders as a reference. In this case, the upper and lower end speeds Vu.

If you replace vL with the speed of the upper and lower cylinders as shown below! stomach. Based on Figure 13, set the interval between the upper and lower cylinders to LI
%If the distance from the upper end of the short side to the upper cylinder is j, the velocities of the upper and lower cylinders Vuc and VLc are as follows (61L (6
2) It can be expressed by the formula.

Vu c = (VL - Vu) Fist j/L+Vu
-(61)VLc= (VV-Vu) ・(
j+Lt J /L+Vu -<623 Therefore, the speed difference between the upper and lower cylinders is Vuc-Vtc=(VL-Vu)sLt/L=α・
L/U c -(631), and instead of the length L of the short side, the distance between the upper and lower cylinders may be used.

In this embodiment, the above (27
), (Formula 307, initial velocity Blb of the upper end of the short side during the forward tilting phase
and the initial velocity B2 of the short side upper part during the backward tilt period were set as follows.

Bl=α1・Ll/Uc B,=+α1sTr On the other hand, since the cylinder capacity was insufficient for α with the value set from the shell strength, the upper and lower cylinder capacities Fuu were determined from the cylinder capacity again.

PTT is 7 tons from the above (431, (441 type) (
10 ton - 1,5 ton - 1,5 ton J,, also, the said 1ii! From the tensile test results of seeds, Go = 2.5 x 10-13 ((
kg/aJ) ”・5ec), n=0.32.q=2
8000 (1,10K) was found. In addition, the shell thickness was measured and found that Ho = 20 (mm/minl/21). Under this condition, the speed increase rate α was successively changed, and the above (
The required driving forces Fu and Ft were determined based on 37) to (41) &.

The 181st %l shows the center, and the required driving force Fu, Ft of the upper and lower cylinders is the nodal force puu, Ftt
In order to satisfy the following conditions, the busy speed increase rate α is 50m/m1
It was set as n'. Therefore, the upper and lower cylinder speed difference ΔVc is (
1) Equation (63) corresponding to 2: Δvc = α difference L1/Uc = 50X640/1600
=20 (m/m1r3).

The speed increase rate α1 during the forward tilt period and the speed increase rate α1 during the backward tilt period are set to α1goa in order to improve controllability, as described above.

Therefore, the speeds of the upper and lower cylinders in the forward tilting period and the backward tilting period are determined as follows.

Forward tilt period during width reduction (0≦t≦Tr) Vuc=20+50 t (4/m1n)
−(64)VLc = 50 t (tm/m1n
) (653 Retrograde period during width reduction (Tr≦
t≦TV) Vuc=50(Tw-1)(+m/m1n) −
(66) VLc =20+50(Tvr-t)(+w/
m1nJ - (67) Furthermore, assuming that the taper amount at the start and end of width change is the same, width change time Tw and width change time TwTr = 0.2X ((1 + 0.5X10
0)V'2-1)=1:, 23 (min)
-(68)Tw=0.4X ((1+0.5X100
)1A-1)=2.46 (m1nt-(69)
In addition, the error with respect to the target width change amount caused by the difference in the taper amount at the start and end of the width change is as described in (54) on one side.
, (Based on formula 553, the result obtained using formulas (70) and (71) below is 3.135 m (one side), and the parallel movement time T
h becomes the following equation (72) from the above equation (57), assuming that the parallel movement speed is the lower cylinder speed at the end of the forward tilt period.

Pay = (640/800)X (5-83/20=0
．． 12 (minJ-(To) △W=(1/2)X50X0.12"+(1+(100
/640))X20X0.12=3.135(m)
(71) Th-3,13s/ (50xO,12)=0
．． 05 (minl - (72)) Furthermore, add 1 to the taper amount at the end of the forward tilting phase and W at the end of parallel movement, (slab width/2)
From the above formulas (59) and (60), the following (73) and (74
There will be 1 set.

1)=-(800/640 JX(20X1.23 l
+8=-22,75(cod pW cod=500+((1/21
x50x(1,23"-0,12"r+(1+(10
0/640))X20X(1,23-0,12J)
=5.53. Item 3 (21) 1) 1) As mentioned above, set the upper and lower speeds Vu and VL, start changing the width, move forward until the taper amount matches 1, and change the upper cylinder speed to the lower cylinder speed. is the same, and the width of the slab is (W,
2), and then the lower cylinder speed was changed to the upper cylinder speed at the end of the forward tilt period, and the backward tilt movement was performed until the taper amount matched the target taper amount to 3 to reduce the width. The 19th factor shows the width change time relative to the target width change (reduction) amount in comparison with the conventional method, where the solid line is the embodiment of the present invention and the broken line is the conventional method. 19th
In the figure, the horizontal axis indicates the width reduction amount Qm/one side, and the vertical axis indicates the width change time Tw.

Further, the width reduction by the conventional method was carried out by the method shown in FIG. In this case, in order to suppress the generated air gap amount to a level that does not cause large casting defects, and to reduce the width by reducing the required driving force to 7 tons or less, the parallel movement speed Vm must be 35 tp.
-n/' minutes was the limit.

According to FIG. 19, regardless of the size of the width reduction amount.

It can be seen that the width changing time is shorter in the embodiment of the present invention than in the conventional method. Further, as the amount of width reduction increases, the effect of shortening the width change time according to the embodiment of the present invention increases.

20. Figure 1 (a) and (b) show the width reduction of the conventional method (,) and the embodiment (b) of the present invention.
Figure 1 shows the change in the shell deformation resistance force acting on the upper and lower cylinders over time from the start of the width change.

The maximum required driving forces Fumax and Ftmax of the upper and lower cylinders shown in FIG. Note that in this embodiment, the parallel movement time Th is extremely small compared to the times of the forward and backward tilting phases, so it is omitted from the above diagram. In addition, as for the air gap generated, in the case of the conventional method, a maximum of 1.5 f1 was generated, whereas in the case of the present invention, it was almost zero, and no internal or surface defects were observed. 'Next, an example will be described in which the slab width was increased from 1000 mK to 1200 mK. In this case, the taper amount needs to be changed from 5m to 8wK. In this width expansion, as well as in the width reduction, the above (37) to (
From formula 41), the vertical cylinder speed Vuc, V of short side 1
tc is set, and the velocity pattern of the upper and lower cylinders is determined by the following formulas (751 to (781).

Retroversion phase during width expansion (O≦t≦Trl Vuc=-50t (ww/mLnJ
−(753VLc =20 50t (we
/min+ -(763Anterior phase when width is expanded (T
r≦t≦Tvr)Vuc=20 50 (Tw-t)
(+w/mtn) -C77)VLc =-50(Tw
-t) (mm/min) -(78) Also, assuming that the taper amount at the start and end of the width change is the same, the width change time Tw and the retroversion period time Tr are as follows (79), (80
) is given by the formula.

Tr =0.2X ((1+0.5X100)1/2
+1)=1.63(mlnl-(79) Tw=Q,4X((1+0.5X100J1/2+1
) = 3.26 (minJ - (801) Also, the error for the target width change amount button caused by the difference in the taper amount at the start and end of the 2-width change is (54J, (
Based on the following equation (81J, (82) based on the equation 561, the result is 0.735-, and the parallel movement time Th is calculated by the above (
It is determined by the following (83) from the formula 57).

TΔ=(6407800)×(l 8-513/20
=0.12(mi'n)-(81) ΔW=(1/21X50X0.12"+(100/64
0)X20X0.12=0.735(m)-(8
2) Th=0.735/(50/1.63-207=Q
, Q 1 (Dew) - (83) 21st r! A shows the width change time based on this example in comparison with the conventional method. In FIG. 21, the horizontal axis shows the width expansion amount Qal/one side, and the vertical axis shows the width change time Tw. Further, the solid line in the figure shows the embodiment of the present invention, and the broken line shows the conventional method. Width expansion using the conventional method is carried out using the method shown in Figure 4, and the parallel movement speed Vm
As in the case of width reduction, the limit was 15 m/+ in order to keep the air gap amount below the allowable value and the required driving force within 7 tons. In this width expansion, as in the case of width reduction,
It can be seen that the width changing time is significantly shorter in the embodiment of the present invention than in the conventional method, regardless of the amount of width expansion.

Also, regarding the amount of air gap generated and the required driving force,
The amount of air gap generated was almost zero, and the required driving force of the lower cylinder was 7 tons or less, and as in the case of width reduction, each was within the allowable value.

(Effects of the Invention) As detailed above, by carrying out the present invention, the width of the mold can be changed in a minimum amount of time. Therefore, the portion where the width of the slab changes due to the width change can be reduced, and the yield can be significantly improved.

In addition, the width of the slab was changed to 130 mm in order to efficiently absorb the error in the target width change amount caused by the difference in the Taber amount before and after the width change (before and after the width change is started).
It becomes possible to change the width by any amount between 0 and 650 square meters while keeping the air gap amount and shell deformation resistance force below the allowable value during the width change. As a result, stable operation without cracking or breakouts is possible even when changing the width at high speed.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams for explaining the horizontal movement speed of the upper and lower ends of the short side when changing the width according to the present invention, and Figure 2 is a diagram of a known variable width mold. It is a perspective view showing an example. Figure 3 ((a), (b), (c)
)> and Figure 4 ((a), (b), (c))
2A and 2B are schematic diagrams showing an example of a conventional width changing method, in which FIG. 3 shows width reduction, and FIG. 4 shows width expansion. Figures 5 to 21 are diagrams showing examples based on the present invention, the fifth is a schematic diagram showing the movement of the short side when the width is reduced, and the sixth is a schematic diagram showing the movement of the short side when the width is expanded. Schematic diagram showing the movement status of Figure 7 (a) and (b)
8 is a conceptual diagram explaining the movement of the short side and the conditions for generating the air gap, 8th panel is a conceptual diagram illustrating the amount of linear mass received by an arbitrary point on the slab while passing through the mold, and FIG. 9 FIG. 2 is a conceptual diagram illustrating the strain rate of the shell in the width changing method of the present invention. Figure 10 (a), (b) and Figure 1) (a)
) and (b) are diagrams showing the relationship between the strain rate and the acceleration rate of the shell, in which Figure 10 shows width reduction and Figure 1) shows width expansion. Figures 12 (a> and b) are diagrams showing the ranges of α and B where no casting defects occur, Figure 13 is a structural diagram showing the arrangement of the upper and lower cylinders that drive the short sides, and Figure 14 The figure is a diagram showing another example of the moving speed of the upper and lower ends of the short side when width is reduced. Figure 15 is a diagram for explaining the error in the width change amount caused by changing the taper amount. 17 is a diagram showing an example of width reduction; FIG. 17 is a block diagram showing an example of a specific control means in width reduction; FIG. 18 is a diagram showing an example of a method for determining α from the required driving force;
Figure 9 is a diagram showing the target width change (width change time for reduced J-IK compared to the conventional method; Figures 20 (a) and (b)
) is a diagram showing the change in the shell deformation resistance force acting on the upper and lower cylinders with time from the start of width change in width reduction in the conventional method and the embodiment of the present invention. It is a figure showing change time compared with a conventional method. 1.1a, 1b: short side of the mold, 2: long side of the mold. 3a, 3b: Drive device, 4: Slab. Representative speaker 1 benshi Aki Sawa Masa Mitsunobu 2 Softui 10 diagrams (Q) Ben 14 diagrams 71'1.51) D (1) 0L) I: 1 'n-14 heavy'H" Life: f;
+t rock cane η N \ ward
(Fighting) ~ Knee〇〇 or Engineering 7 H'n-Jff41'l'f*J'ψ7.4 (, Te Ding Ward e O'' Interpretation 21 times crystal m large + Q (mm 1 piece i) Spontaneous Procedural amendment May 21, 1985

Claims (1)

[Claims] (1) When moving the short side of the mold during continuous casting to expand or reduce the width of the slab, the short side is moved in two stages: a forward tilting phase in which the short side is sequentially tilted toward the center of the mold, and a phase in which the short side is tilted toward the center of the mold. The acceleration rate α of the horizontal movement speed of the upper and lower ends of the short side in each period is determined in advance using the allowable shell deformation resistance force as a parameter, and the difference ΔV between the movement speeds of the upper and lower ends is determined in advance. is determined by the following equation (1), and in a method in which the width is changed while maintaining the speed increase rate α and the speed difference ΔV constant during the period, the taper amount at the start of the width change and the target taper amount at the end of the width change. A method for changing slab width during continuous casting, characterized in that an error in a target width change amount caused by a difference in width is absorbed by providing a parallel movement period during transition from a forward tilting period to a backward tilting period. ΔV=α・L/Uc (1) However, ΔV: Speed difference between the top and bottom ends of the short side (mm/min) α: Speed increase rate at the top and bottom ends of the short side (mm/min^2) L: Length of the short side of the mold ( mm) Uc: Casting speed (mm/min)