JPH0645055B2 - Control method of withdrawal of slab in continuous casting - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for pulling out a slab formed in a mold in continuous casting of metal, particularly a casting method effective when cutting the slab. The present invention relates to a piece pullout control method.

[Prior Art] As is well known, continuous casting is a technique for continuously solidifying a supplied molten metal to obtain a long continuous slab. In order to solidify the molten metal, a mold having a cylindrical mold having openings at both ends and its water cooling jacket is used. Continuous casting by supplying molten metal from the tundish into the mold to solidify the area around the outer periphery and continuously pulling this out downstream (further solidifying the inside while sending it to the mold and beyond) You get a piece. Continuous casting is classified into vertical type (vertical type or curved type), horizontal type, etc. depending on the direction in which the slab is pulled out, that is, the direction in which the mold is arranged.

In continuous casting, in order to reduce friction between the slab and the mold and prevent seizure, relative oscillation is applied between the slab and the mold. For example, in vertical continuous casting in which molten metal can be supplied to the mold by the action of gravity, in most cases the mold is placed separately from the tundish, the mold is oscillated, and the slab is pulled out at a constant speed. .

On the other hand, in horizontal type continuous casting in which the tundish and the mold are closely connected to each other so that the molten metal does not flow out, it is usual that the mold is fixed together with the tundish and the slab is withdrawn while being oscillated. In this case, the slab is withdrawn according to an oscillation (intermittent withdrawal) pattern in which each cycle such as withdrawal / stop, or withdrawal / stop / (slight) pushback is one cycle. The oscillation pattern is specified by parameters such as time, distance, speed, and the number of cycles per time regarding each stroke for each cycle, and the movement given to the slab by the drawing means arranged downstream from the mold. As expected. It should be noted that pulling out the slab in this manner is common to vertical continuous casting in which the tundish and the mold are closely connected.

The above-mentioned oscillation provided between the slab and the mold has a meaning in stably forming the initial solidified shell in the mold, and is one of the conditions for casting a high quality slab. This is the same when pulling out the slab while oscillating, and the type of metal to be cast (for steel, further steel type).
The optimum oscillation pattern is set for each casting equipment according to the size of the cast piece and casting is performed. For example, to obtain a low carbon steel slab with a cross-sectional diameter of 100 mm, 1
It is said that it is good to pull out at an average speed of 2 to 3 m / min while giving an oscillation of about 00 cpm (100 cycles per minute). The average speed includes a stop stroke and a push-back stroke. In this case, the maximum speed in the pulling stroke is several times the average speed.

As means for cutting continuously cast slabs to a predetermined length, a shear such as a hydraulic type (having a reciprocating blade), a grindstone cutter (having a rotating blade) or a gas cutting machine (using a torch) ), Etc., are used, but in continuous casting in which a slab is withdrawn while oscillating, the following measures have been taken in relation to cutting and withdrawing the slab.

Firstly, the cutting means is configured so as to integrally follow the slab during cutting. Since it takes several seconds to cut the slab with any method, it is necessary for the cutting means to move at the same speed as the slab during that time. Since it is difficult to synchronize the speeds with each other, the cutting means has such a configuration. In a hydraulic shear, etc., since the blade bites the slab, it naturally moves together with the slab, but other cutting means also have a mechanism for gripping the slab,
During cutting, it holds the slab with it and follows the slab,
It moves with the slab (cuts the slab with a grindstone or torch while moving).

Secondly, at the time of cutting so that the moment when the cutting means follows the cast piece (the timing at which the blade bites the cast piece or the gripping means grips the cast piece) does not coincide with the drawing stroke of the aforementioned cycle. The point is that the oscillation pattern is changed. In the drawing process, the slab moves at a considerably high speed as described above, so if the moment when the cutting means follows the slab in some cases coincides with this process, even if the cutting means is delayed, this is still the slab. It is impossible to cut the slab into a predetermined length because the position along with is irregularly displaced from the predetermined cutting position.Because the mass of the cutting means that was stationary until then is suddenly added to the slab, This is because the impact force acts on the piece, and the brittle solidified shell that has just been formed in the mold breaks, which deteriorates the properties of the cast piece and makes it impossible to continue casting.

This second point is related to JP-A-63-80950 and JP-A-62-137.
No. 149 etc. have already been specifically disclosed.

[Problems to be Solved by the Invention] As a method of changing the oscillation pattern at the time of cutting a slab as described above, conventionally, a control signal for operating the cutting means is issued, and then the pulling means receives the signal. I was changing the oscillation pattern. For example, the method disclosed in the above-mentioned JP-A-63-80950 is
When a disconnection command signal is issued in the pulling stroke, the oscillation pattern is changed so as to immediately shift to the low speed pulling or stop (or push back) stroke from that point. Also, in Japanese Patent Laid-Open No. 62-137149, the oscillation pattern is rearranged within the cutting delay time after the cutting command signal.

According to such a method, it is necessary to significantly change the oscillation pattern within a short time after the signal for operating the cutting means is issued and before the cutting means accompanies the slab. In the former method of the above, the slab that is moving at high speed in the drawing process must be immediately moved to the low speed or stopped state. Even in the latter method, the intended purpose cannot be achieved unless the oscillation pattern is changed to a significantly different one in the cutting delay time.

Since the speed of the slab is not abruptly changed due to its inertia, the former method causes the slab to deviate from the predetermined cutting position and cause an error in the cutting length unless a high output is obtained by the drawing means. Even in the latter method, since the oscillation pattern after change must be recombined with an extremely high number of cycles per hour, for example, a high-output drawing means is required.

Further, both of them largely change the optimum oscillation pattern set to obtain a high quality slab as described above, and thus are often unfavorable with respect to the quality of the slab. In particular, when casting a metal having a high crack susceptibility, cracks may occur in the slab.

[Object of the Invention] The present invention has been made to solve the above problems.
In addition to satisfying the requirement to cut the slab accurately to a predetermined length without applying impact force, it is possible to reduce the degree of change of the oscillation pattern at the time of cutting and reduce the quality of the slab. An object of the present invention is to provide a slab withdrawal control method in continuous casting, and a slab withdrawal control method in continuous casting that can satisfy the above-mentioned requirements even with a low-power drawing means.

[Means for Solving the Problems] In the drawing control method of the present invention for achieving the above object, a continuous slab cooled and solidified in a mold is set as one cycle including a drawing process and a stopping process. In addition to pulling out according to the oscillation pattern, when cutting the slab to a predetermined length, the cutting means is operated before the cutting means is operated so that the moment the cutting means is added to the slab is within the stop stroke. The method is characterized in that the oscillation pattern is changed for a plurality of cycles up to the moment of joining the cast piece.

Further, the drawing control method according to the second aspect is such that the slab is drawn at a low speed after the cutting means is put on the slab and after the cutting is completed, until the slab is separated from the slab.

[Operation] According to the drawing control method of the present invention, since the moment the cutting means follows the cutting piece is within the stop stroke, no impact force is generated by the cutting means, and the casting piece has a predetermined length. Can be cut accurately.

Further, since the oscillation pattern is changed over a plurality of cycles before the cutting means is operated until the cutting means accompanies the slab, the degree of change in each cycle may be extremely small. That is, some parameters of the optimum oscillation pattern set as described above (that is, the number of cycles per hour, the time of each stroke, the distance, the speed, etc.) need only be slightly changed. Has almost no effect on the quality of. The larger the number of cycles for changing the oscillation pattern (for example, 5 or more), the smaller the degree of parameter change.

Since the cutting means moves along with the slab after having moved along with the slab, even if the moment of leaving the slab after completion of cutting coincides with the drawing stroke of the slab, no impact force is exerted on the slab. . That is, the load of the drawing means (the load due to the driven mass) increased by the cutting means following the slab,
The cutting means decreases at the moment of leaving the slab, but since the cutting means moves at the same speed as the slab at this moment, the load fluctuation has almost no effect on the movement of the slab, and even if there is Is only a gradual increase (in some cases, a gradual decrease).

Further, according to the drawing control method of claim 2, the slab (together with the cutting means) is drawn at a low speed while the driven mass with respect to the drawing means is increased by the cutting means along with the slab. The required output of the extraction means does not increase.
In other words, the drawing means does not require an output higher than that in the steady operation in which only the slab is drawn in accordance with the predetermined oscillation pattern.

[Embodiment] FIG. 1 is a diagram showing an example of a horizontal continuous casting facility for steel for carrying out the present invention, and FIG. 2 is a time chart relating to the first embodiment of the invention.

The continuous casting shown here is carried out mainly using the tundish 30, the mold 40, the transfer roll group 50, the drawing means 10, the cutting means 20 and the length detector 30 arranged as shown in FIG. The mold 40 is configured to cool the outer peripheral wall of the cylindrical mold 41 with water, and the upstream end is tightly connected to the tundish 30 via the connection refractory 31.
It is fixed with 30. Molten steel A stored in the tundish 30 flows into the mold 40 and is cooled to form a cast slab B whose outer peripheral portion is solidified. The slab B is pulled out one after another from the mold 40 by the pinch rolls (driving roll 14 and pressing roll 15) of the drawing means 10 in the right direction of the drawing. Further, the slab B is released from the mold 40 and then solidified to the inside by natural heat dissipation, and the length is measured by the detector 30 to cut the cutting means 20.
It is cut to a predetermined length.

The pulling-out means 10 is composed of rolls 14 and 15, a motor 13 for driving the roll 14, an amplifier 12 and a controller 11. Roll to remove slab B while oscillating
14 is driven to rotate intermittently. That is, the motor 13 and the roll 14 are rotating in the normal rotation / stop or reverse rotation according to the oscillation pattern (which is arbitrarily set according to the casting content) input to the control device 11 in advance. The details regarding this will be described later.

The length detector 30 detects the length of the slab B that passes through the set position, and for example, a part that comes into contact with the slab B and rotates, and a part that outputs the number of revolutions converted into a pulse. And have. Then, the output is input to the control device 11 described above.

The cutting means 20 is a hydraulic shear, and in the frame 23 thereof, the moving blade 26 is configured to move together with the moving frame 24 toward the fixed blade 25 by the cutting hydraulic cylinder 22. Since the cutting blades 25 and 26 need to move together with the slab B in the pulling direction when the slab B is bitten, the frame 23 is swingably supported at its lower end via a pin 26. Further, the frame 23 has a pullback hydraulic cylinder 27.
Is attached, and the frame 23 after cutting is returned to its original position (before cutting). However, while the frame 23 moves (swings) together with the cast slab B during cutting, the cylinder 27 is released from hydraulic pressure and is in an expandable and contractible state. Driving (expansion and contraction) of cylinder 22 and cylinder 27
This is done by hydraulic oil supplied and controlled by the hydraulic unit 21. Then, the hydraulic unit 21 has a pulling means 10
It is connected so as to send and receive signals to and from the control device 11.

In order to smoothly cast a good quality slab B in the above equipment and accurately cut it into a predetermined length, the withdrawal means 10 controlled the withdrawal of the slab B as follows. Hereinafter, a case of casting a high alloy steel (having a high crack susceptibility) will be described as an example with reference to FIG. The three diagrams of FIG. 2 are, in order from the top, the drawing (moving) speed v of the slab B, the length l of the slab B (the definition of l will be described later), and the moving blade 26 of the cutting means 20.
Displacement s (both are vertical axes) and time (time) t (horizontal axis)
And the charts are called vt chart, lt chart, and st chart, respectively.

The drawing means 10 usually draws the cast slab B according to an optimum oscillation pattern (hereinafter, simply referred to as a pattern) according to the steel type and size (cross-sectional dimension) thereof.
This pattern is 1 for each process of pulling out, stopping, pushing back, and stopping.
Repeated as a cycle, and is represented by left-sided (t ≦ ti) waveforms pl and <pl> in the vt chart (v> 0 pulls out, v = 0 indicates stop, v <indicates pushback) and the lt chart. It is a thing. The parameters that specify this pattern are the times f, wl, and
r, w2, cycle time (time per cycle) c, waveform pl, pullout amount F (pullout distance during pullout time f) and pushback amount R (between pushback time r) on the 1-t chart Push back distance). The waveform <pl> of the lt chart corresponds to the speed v shown in the vt chart, which is integrated over time t. Typical parameters used for actual casting are F = 10mm, R when the slab B is a high alloy steel with a diameter of around 100mm.
= 0.5 mm, c = 0.4 sec.

The length detector 30 detects the pull-out amount F and the push-back amount R in which the slab B has actually moved and inputs it to the control device 11.
In 11, the length l of the cast slab B as the product length is calculated based on these detected values. That is, the control device 11 adds / subtracts the above amounts F and R each time, and performs hot correction (converts a value at high temperature to a value after cooling) and position correction (from the detector 30 to the cutting means 20). (Subtracting the distance) gives the product length l, that is, the previously cut point Ba
(See FIG. 1) to cutting means 20 (cutting blades 25, 2 in standby)
The length l of the cast slab B up to the position of 6) after being cooled is calculated. Since this calculation is performed with the time when the push-back stroke is finished as the calculation point for each pulling cycle, the length l is usually increased by about F-R at each calculation point. At the same time, the control device 11 compares the length l with a preset cutting length ls and also calculates the number of remaining cycles until the length l becomes the cutting length ls.

In this embodiment, in order to avoid the moment when the cutting blades 25 and 26 of the cutting means 20 bite the slab B from coincident with the drawing stroke, the length l approaches the predetermined cutting length ls and the remaining n After the cycle, the cutting blade length 25, 2
The above-mentioned pattern was changed until 6 bites the slab B. This n may be set to an arbitrary value in advance, but a case where n = 5 will be described below as an example.

The control device 11 judges whether or not the length 1 of the cast slab B approaches the cutting length ls until the length 1 of the cast slab B satisfies ls-l≤nx (FR) (where n = 5) by the above-mentioned calculation. , Ti is the time of the calculation point where the formula is first satisfied, and li is the length of the ingot B at that time. There is no problem when the equal sign is satisfied in the expression, but when the inequality sign is obtained, with this pattern as it is, the time corresponding to the cutting length ls of the cast slab B reaches the positions of the cutting blades 25 and 26. , The stop stroke (time w2) does not match. That is, for example, as shown in FIG. 2, when the waveforms pl and <pl> remain, the length 1 of the cast slab B becomes the cutting length ls at time tpl, and the cast slab B is at a high speed in the drawing stroke. It overlaps when moving. If the cutting blades 25 and 26 are bitten into the slab B at this time, the above-mentioned inconvenience will occur. Therefore, the pattern after the time ti at the above calculation point is the waveform of the solid line in the vt chart and the lt chart of the same figure. Change to the pattern indicated by p2 and <p2>.

The pattern after this change may be one that determines the withdrawal amount per cycle so that the slab B can be withdrawn by the length (ls-li) in exactly 5 cycles, but in this embodiment, before the change For the (normal) pattern, the cycle time c, the push-back time r, and the push-back amount R are unchanged, and the pull-out amount is changed to F '(<F) to obtain F'-R.
= (Ls-li) / 5. Further, in order to determine this amount F ', the withdrawal time f'(<f) was set, and the stop stroke times before and after that were changed to wl '(> wl) and w2'(> w2), respectively.

Such a pattern change is automatically performed by the control device 11, but as a result of the change, the length l of the slab B becomes the cutting length ls as shown in the figure so that it coincides with the stop stroke (time w2 '). become.

Therefore, as shown in the st chart of the same figure, if a disconnection command signal is issued from the control device 11 to the disconnecting means 20 at time tc in which the operation delay of the disconnecting means 20 is expected, at an appropriate time tp2 within the above stop stroke. The cutting blades 25 and 26 bite the slab B. The time from time tc to time tp2 in the chart is the operation delay time of the cutting means 20, and is the time for signal processing, the operation time of the control valve (not shown) in the hydraulic unit 21, and the play of the movable blade 26. The time (depending on the clearance with the slab B) and the like are included, but this time does not have a difference for each cutting, and therefore the value actually measured in advance may be expected. The cutting blades 25 and 26 bite the slab B and move together, while the moving blade 26 ascends according to the solid line in the chart and descends from the time te at which the cutting ends, and the cutting means 20 moves to the cylinder 27. It is pulled back to the original position by the action of. The slab B separated at time te (the slab from the previously cut location Ba to the current slicing) is promptly delivered by the transport roll group 50.

After the cutting blades 25 and 26 bit the slab B, the slab B may be pulled out by returning it to the original pattern represented by the waveforms pl and <pl> as shown in the figure. Since the cutting means 20 moves together with the slab B together with the frame 23, even when the cutting blades 25 and 26 separate from the slab B, no impact force is exerted on them.

As described above, in order to match the moment when the length 1 of the slab B is equal to the cutting length ls (the moment when the cutting blades 25 and 26 are bitten into the slab B) with the stop stroke, l ≧ ls. Since the pattern is changed over the previous 5 (n) cycles, the degree of change may be about 1/5 at the maximum. Also in this embodiment, the withdrawn amount F ′ per cycle after the change is
With respect to the original withdrawal amount F (at the time ti when the equation is established, it depends on the value of the remaining length ls-li), but at most 1 /
It is reduced by 5. The degree of change becomes smaller (to 1 / n) as n is set larger. However, when both the withdrawal amount F and this n are large, it is better to perform hot correction with respect to the length 1 of the slab B as well as the withdrawal amount and the pushback amount R.

In the above, when the pattern is changed, the cycle time c and the pushback amount R are left unchanged, and the pullout amount F is changed by changing the respective times f, wl and w2 of the pullout stroke and the stop stroke. In order to change the withdrawal amount F, the maximum speed (or speed waveform) may be changed without changing the time f. In addition, the push-back amount R is changed without changing the pull-out amount F, or both amounts F,
By changing R together, the difference becomes (ls-li) /
It may be set to n (n = 5 in the above example). Furthermore, for the cycle time c, c '= (tpl-ti) / n
If the pattern is changed to the waveform <p3> on the lt chart, the cast slab B can be cut at the time tpl predicted as before the pattern change. The stop stroke time w2 (and therefore w2 ') is extremely short,
When it takes a certain amount of time for the movable blade 26 to bite securely (to the extent that it can move along with the slab B) after touching the slab B, when this biting (example of It is sometimes good to lengthen the stop time before and after tp2). Further, by the pattern change described above, at the moment when the cutting blades 25, 26 bite into the slab B (when the length l becomes the cutting length ls), another stop stroke (time wl ′ in the previous example) is used. ).

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the speed v of the slab when low carbon steel is cast by the horizontal continuous casting equipment similar to the above embodiment.
And vt chart and st chart showing the relationship between the displacement t of the cutting blade (moving blade) and the time t.

First, in the left part of the vt chart, the original (normal) pattern for withdrawing the slab as shown by the waveform p11 is the same as in the above embodiment, and after a certain calculation point where the slab length approaches the predetermined cutting length. It is shown that the pattern is changed to the pattern represented by the waveform p12 of the solid line in FIG. Here, the original pattern (waveform p11) is still pulled out, stopped, pushed back,
It consists of each stroke of the stop, and it is the most suitable for this slab, whereas the modified pattern (waveform p12) is
With each stroke time and cycle time unchanged, the maximum speeds of the withdrawal stroke and push-back stroke are reduced to reduce the withdrawal amount and push-back amount per cycle. By doing so, at the moment when the position corresponding to the cutting length of the slab comes to the position of the cutting blade, it coincides with the stop stroke, and the cutting blade can be engaged with the slab at an appropriate time tp12 of the stop stroke. . The st chart in the figure shows that a disconnection command signal is issued at time tc ′, which is expected to delay the operation of the disconnecting means, and
Figure 12 shows that the cutting blade (moving blade) bites the slab. As shown in the same chart, the moving blade finishes cutting at time te ', leaves the slab, and returns to its original position.

The feature of this embodiment is that the cutting blade bites the slab until it leaves (at least the above time tp12 to the time te ′).
Until the slab is drawn at a low speed according to the pattern represented by the waveform p13 of the vt chart. During this time, the cutting means is accompanied by the cast piece, so the drawing means needs to drive the cutting means together with the cast piece.
Since the slab is once stopped at the moment when the cutting blade bites, the slab is pulled out at an extremely low speed (therefore, the acceleration is small and the acceleration time is short), so that the load of the drawing means does not increase. That is, it is not necessary to use a high output as a drawing means.

Note that the speed during this period must be a value that does not adversely affect the properties of the slab, but it has low susceptibility to cracking (that is, it is easy to cast), such as low carbon steel, and has good rolling characteristics (the properties of the slab are not a problem. In the case of producing a slab (which does not occur), the value can be set to an extremely low (slow) value such that the molten steel does not solidify and block at the connection part of the tundish mold. Then, after the cutting blade is separated from the slab, the slab is pulled out by returning to the original pattern represented by the waveform p11 as shown in the figure (for example, restarting from the stop / push stroke).

Although the present invention has been described above with reference to the two embodiments, the present invention can be carried out as follows.

a) The oscillation pattern is not limited to the one including both the stopping and pushing back strokes as described above. Even when there is no pushing back stroke, the moment when the cutting means follows the slab and the stopping stroke are matched in the same manner as above. If there is no stop stroke (only the pull-out and push-back strokes), provide a short stop stroke in the changed pattern, or consider that the moving speed and distance of the slab are small in the push-back stroke, The pattern may be changed so that the moment when the cutting means follows the slab is adjusted to the pushing back stroke.

b) The cutting means is not limited to the hydraulic shear described above, but a mechanical shear, a rotary grindstone cutter, a gas cutter, or the like can be used. Since the cutting means other than the shear is configured to grip the slab by the gripping mechanism during cutting, the cutting blade grips the slab instead of the cutting blade biting the slab. It will move along with the cast slab. Therefore, in order to carry out the present invention when the cutting means is other than the shear, the oscillation pattern may be changed so that the moment at which the gripping mechanism grips the slab falls within the stop stroke of the slab.

c) Not limited to horizontal type continuous casting and steel casting,
It can also be applied to vertical continuous casting or casting of non-ferrous metals such as copper and aluminum. Further, the vertical continuous casting can be applied not only to the type in which the tundish and the mold are closely connected but also to a case in which a slab is pulled out while oscillating in a general type in which the two are separated.

[Advantages of the Invention] As described above, according to the method for controlling the withdrawal of a slab according to claim 1 of the present invention, 1) the moment when the cutting means is added to the slab is within the stop stroke, so the cutting position The slab can be accurately cut into a predetermined length without slippage. As a result, there is no wasted slab in the process after casting (rolling, etc.), and the yield of slab is improved.

2) Similarly, since the moment when the cutting means follows the stop stroke, the cutting means does not cause the blade of impact force to follow the cast piece. Therefore, the property of the cast slab and the casting equipment are not adversely affected.

3) It does not degrade the quality of the slab, as it only needs to be changed slightly over the optimum oscillation pattern for casting over multiple cycles. This point becomes a great advantage especially when a metal cast piece that needs to be maintained in proper casting conditions due to high crack susceptibility is drawn out.

Further, according to the drawing control method of claim 2, in addition to the effects of 1) and 2) described above, while the cutting means follows the slab and the driven mass with respect to the drawing means is increasing, the slab is Is pulled out at a low speed to reduce the load on the pulling means, so that the required output of the pulling means is reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a horizontal continuous casting facility for steel for carrying out the present invention, and FIG. 2 is a time chart relating to the first embodiment of the invention. Further, FIG. 3 is a time chart regarding the second embodiment. 10 ... Withdrawal means, 11 ... Control device, 14 ... Drive roll, 20 ...
Cutting means, 21 ... Hydraulic unit, 22 ... Cutting hydraulic cylinder, 25 ... Fixed blade, 26 ... Moving blade, 30 ... Length detector, B ... Cast slab v ... (Slab withdrawal) speed, l ... (Casting) Length), ls ...
Cutting length (of slab), s ... displacement (of moving blade), t ... time,
pl, <pl>, p11 ... (according to normal oscillation pattern) waveform, p2, <p2>, <p3>, p12, P13 ... (according to changed oscillation pattern) waveform, F, F '...
Drawout amount, R ... Pushback amount, c, c '... Cycle time.

Claims (2)

[Claims] 1. A continuous slab that is cooled and solidified by a mold is pulled out in accordance with an oscillation pattern that is set as one cycle of a pulling stroke and a stopping stroke, and the slab is cut into a predetermined length. Changing the oscillation pattern for a plurality of cycles from before operating the cutting means to the moment the cutting means follows the slab so that the moment the cutting means follows the slab falls within the stop stroke. A method for controlling the withdrawal of a slab in continuous casting. 2. A slab for continuous casting according to claim 1, wherein the slab is pulled out at a low speed during the period after the cutting means has followed the slab and until the slab is separated from the slab after completion of cutting. Pull-out control method.