JPH0767605B2 - How to finish casting in continuous casting equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a casting termination method for a continuous casting facility having a plurality of strands.

(Prior Art) Each of the strands continuously cast by a facility having a plurality of strands is cut into slabs each having a predetermined size based on a production plan. It is desirable to finish the casting in accordance with the final cutting position determined from the production plan of the slab, and to avoid the production of slabs having dimensions outside the production plan as much as possible.

In the past, the control of pouring end in continuous casting relied heavily on the judgment of the operator. That is, the operator estimates the castable length of each strand from the casting target molten steel amount (steel output amount) and the current casting amount, and calculates the final cutting position according to the production plan. Next, the operator finishes the pouring while communicating with the cutting chamber operator and the pouring operator at the time of pouring to the final cutting position.

The conventional method by such an operator has the following problems.

(1) Since the calculation of the castable length of each strand depends on the operator's intuition, the precision of the cast end position (cutting end position) is poor. Also, the pouring end position cannot be determined until immediately before the pouring end.

(2) When the castable length of each strand changes due to changes in the casting speed and casting size due to casting problems, etc. (both strands change due to changes in one strand) It is necessary to review the position, but this cannot be followed.

(3) Due to these reasons (1) and (2), one strand may be terminated faster than necessary or the casting may be finished before the scheduled position.

(4) Since the operator decides the pouring stop position, the stop position tends to vary. If the stop position has an error of several centimeters, the weight required in the production plan cannot be secured when cutting.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a casting termination method for a continuous casting facility having a plurality of strands, which solves the above-mentioned problems of the prior art. In particular, for at least one strand of the multiple strands, the casting stop position is precisely adapted to the final cutting position determined from the production plan, avoiding the production of a halfway slab that is out of the production plan, and It is an object of the present invention to provide a pouring termination method that stops pouring almost in the same manner and improves production efficiency and product yield.

(Means for Solving the Problems) Thus, the gist of the present invention is that in the method of terminating the casting of the continuous casting equipment having a plurality of strands, a) measuring the residual molten steel amount in the ladle, and b. ) Calculate the castable length of each strand under the current casting conditions, and c) Determine the final cutting position of each strand from the castable length of each strand calculated in step b) and the slab cutting plan. And d) calculating the required casting time to the final cutting position of each strand calculated in step c), and e) maximizing the required casting time calculated in step d). A method of terminating the casting of each strand while decelerating the strand as a preceding stop strand and decelerating with the final cutting position calculated in step c) as a target; Is.

(Operation) Each step a) to e) will be described by taking as an example the end of casting in a continuous casting facility having two strands for simplicity.

In FIG. 1, the molten steel in the ladle 1 is the tundish 2
The molten metal is poured into the mold 3 via the to form strands 4 continuously (only one strand is shown).

The termination method determining device 6 for determining the pouring termination method according to the present invention determines the pouring termination method based on information from the upper CPU 5 and the continuous casting facility. The pouring control device 7 controls the pouring end of the casting equipment according to the ending method determined by the determining device 6.

Hereinafter, the steps a) to e) will be described separately for each item.

a) Determination of residual steel amount The residual molten steel amount in the ladle is calculated from the ladle weight value measured by the weight scale 1a, the pot condition (brick wear state, etc.) provided by the upper CPU5, and the thickness of the ladle by the following formula: (Remaining steel amount) = (Measured total weight of ladle)-(Calculated weight of pan)-(Noro weight) In the above formula, calculated value of pan weight and Noro weight are the data from CPU5 (pot condition, Noro thickness, etc.) It is a value calculated based on.

b) Calculation of the castable length The castable length 1 of each strand under the current casting conditions is calculated as follows.

The casting amount Δw per unit time is calculated by the following formula: Δw = S ₁ × specific gravity × V ₁ + S ₂ × specific gravity × V ₂ However, Si: i-th strand cross-sectional area Vi: i-strand casting speed here The Si, the specific gravity of steel, and the Vi required for the calculation are obtained from the CPU 5 and the pulse generator 8 (i = 1, 2).

The remaining castable time T under the current casting conditions is calculated by the following formula using the residual steel amount determined in a): T = (remaining steel amount) / Δw The castable length li of each strand ( i = 1, 2) is calculated by the following formula: li = Vi × T c) Final cutting position calculation FIG. 2 shows L: length from meniscus (melt surface) to already cut surface for one strand. (Pre-cut uncut length) l: Possibility of casting. Assuming that this strand is cut into slabs as shown by the broken line, in FIG. 2, λ: length from the meniscus to the final cutting position is Δl: l−λ. FIG. 3 schematically shows these lengths Li, li, λi, Δli (i = 1, 2) in the first and second strands (each cutting position is indicated by an opposing arrow and a broken line). ).

The cutting plan for slabs on each strand is the upper CPU5
Based on the stored slab production plan, all cleavable length L ₁
＋ l ₁ , L ₂ ＋ l ₂ It is done by taking as many billing slab lengths as possible. At this time, consider the following points.

For bottom slabs 4a of poor quality (Fig. 2), assign orders that can also be used for bottom slabs.

If there is a quality defect in the uncut length L that has been cast,
Avoid that part or leave it as a surplus.

The bottom slab 4a is supercooled and requires maintenance due to shrinkage of thickness and width and deterioration of quality. In order to meet the required weight in the lower process, these must be corrected by the following formula: However, K: weight correction factor for thickness and width shrinkage (average 1.3%) d) Calculation of required casting time Required time to final cutting position of each strand calculated in step c) τi (i = 1,2) Is calculated by the following formula: τi = λi / Vi e) Determination of pre-stopped strand and deceleration pattern τi obtained above is compared, and the strand having the maximum τi is determined as the pre-stopped strand (i = 1 or 2). ). (This pre-stopped strand may be determined by calculating Δli / li for each strand and selecting the strand that minimizes Δli / li. Alternatively, (li−Δli) / li = λi / li It is also possible to set the maximum strand as li = Vi · T and T is constant in all strands. These methods are naturally included in the present invention.) Next, regarding the preceding stop strand and other strands A deceleration pattern suitable for the steel type and size is selected from several types of deceleration patterns stored in advance (for the deceleration pattern example, see the description of the embodiment). In addition, it is preferable that the steps a) to e) are repeated at a constant cycle (for example, 5 seconds) to immediately respond to a change in the situation.

f) Casting end control For the preceding stopped strand, end control is performed based on the remaining casting length λi according to the deceleration pattern selected with the final cutting position as a target (strand stop control). Therefore, the preceding stop strand is stopped exactly at the target position.

It is preferable to control (auto stop control) the strands that do not stop in advance according to the deceleration pattern based on the amount of steel remaining in the tundish 2 (measured by the weight scale 2a). The strand that does not stop earlier stops immediately after the stop strand stops, leaving a predetermined amount of molten steel in the tundish 2.

For details of these pouring end control, refer to the description of the embodiment.

(Example) FIG. 4 shows an example of the deceleration pattern of the preceding stop strand (i-th strand) (lower stage) and the change in the remaining casting length λi (upper stage) calculated by the following equation based on this pattern Vi (i). = 1 or 2).

The preceding stop strand is decelerated at each time when the remaining casting length λi becomes the length corresponding to the deceleration change points A, B, C, D.
Vi / dt is changed according to the pattern and the pouring speed Vi is decelerated according to the selected deceleration pattern Vi and the pouring is completed.

FIG. 5 shows strands other than the preceding stop strand (jth j
Strand) deceleration pattern examples (lower stage) and changes in the predicted tundish weight W calculated based on this pattern Vj (j = 1 or 2, where j ≠ i). The predicted tundish weight W is calculated by the following formula based on the selected deceleration parameter Vj strand cross-sectional area Sj, molten steel specific gravity G, and the predetermined molten steel amount α to be left in the tundish 2: For the j-th strand, the measured tundish weight measured by the weight scale 2a is the deceleration change points A, B, C, D,
The deceleration Vj / dt is changed according to the pattern at each time when the predicted tundish weight corresponding to E (see FIG. 5) becomes equal. Therefore, the pouring speed Vj is decelerated according to the selected deceleration pattern, and after the preceding stopped strand is stopped, the pouring is completed while leaving the predetermined amount α of molten steel in the tundish 2.

The casting speed is controlled as usual, and the opening / closing of the sliding nozzle 2b and the driving speed of the drawing roll 9 are controlled based on the measured values of the weight meter 2a, level meter 3a, pulse generator 8 and the like. Will be done.

(Effects of the Invention) In the present invention, as described above, the preceding stop strand accurately stops at the final cutting position determined from the cutting plan. The other strands are then decelerated, preferably according to a constant velocity pattern, based on the tundish weight, and stopped shortly after the preceding stop strand stop. Therefore, it is possible to immediately respond to changes in the casting conditions. In addition, at least the strands that are stopped prior to the planned slab production plan can prevent the production of half-finished slabs. Therefore, the yield of the slab and the accuracy of ordering are improved. Also, the automation of control reduces the work load for finishing pouring.

[Brief description of drawings]

FIG. 1 is a block diagram showing an apparatus for carrying out a pouring termination method according to the present invention; FIG. 2 is a sketch of a strand showing a slab cutting plan; FIG. 3 is a slab cutting plan for a plurality of strands. FIG. 4 is a graph showing a deceleration pattern of a preceding stop strand and a remaining casting length calculated according to the pattern; and FIG. 5 is a deceleration pattern of a strand other than the preceding stop strand, and the pattern. It is a graph which shows the tundish weight calculated according to. 1: Ladle, 2: Tundish 3: Mold, 4: Strand 5: Upper CPU, 6: End method determination device 7: Pouring control device

Claims (1)

[Claims] 1. A method of terminating pouring of a continuous casting facility having a plurality of strands, comprising: a) actually measuring the amount of residual molten steel in a ladle; and b) calculating the castable length of each strand under the current casting conditions. And c) calculating the final cutting position of each strand from the castable length of each strand calculated in step b) and the slab cutting plan, and d) each calculated in step c). The respective required casting times to the final cutting position of the strand are calculated, and e) the strand having the maximum required casting time calculated in step d) is set as the preceding stop strand, and the final calculated in step c). A method of terminating the casting of a continuous casting facility, characterized by terminating the casting of each strand while decelerating with the cutting position as a target.