JPS6230065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for supplying slabs in continuous casting, and more particularly to a method for supplying slabs that does not directly interfere with rolling.

As is well known, in recent years, for the purpose of energy saving and high productivity, high-temperature slabs obtained by continuous casting are either used as they are, or they are lightly heated by the edge induction heating method and passed through a heating furnace. The so-called direct rolling method has been proposed and has been implemented on an industrial scale, in which the cast slab is immediately sent to the hot rolling process without any rolling process, or the slab is charged into a heat retention furnace, lightly heated, and then sent to the hot rolling process to form a product. I started to do that.

By the way, if this direct rolling method is adopted, there is no function to adjust the rolling schedule between the continuous casting process and the hot rolling process by temporarily placing the material to be rolled, for example, a slab or charging it into a heating furnace. cannot be re-edited, and the order of strips in the continuous casting process must be configured to immediately satisfy the hot rolling schedule.

Normally, there is a difference in production capacity between the continuous casting method and the hot rolling method due to technical constraints.Therefore, for one hot rolling process line, the continuous casting process requires 2 to 8 lines.
A method of casting with multiple strands called strands has been adopted.

Conventionally, a measuring plan has been fixed for each strand, and the cutting dimensions and cutting order of each strand have been determined. Therefore, in order to carry out the direct rolling smoothly, operational efforts are made to ensure that the order of strips satisfies the rolling schedule (hereinafter referred to as roll schedule) by maintaining the casting speed optimally for each strand. However, if casting speed fluctuations occur or quality abnormalities occur, all slabs that do not meet the rolling schedule are temporarily placed and sent to the cold working process or warm heating process. Ta.

However, with such means, the energy saving effect is significantly lost and the productivity is also reduced. Therefore, the present inventors cut a plurality of strand slabs obtained by continuous casting in a planned manner and directly rolled them. In the direct rolling method of supplying slabs sequentially in the order of the roll schedule, when a casting abnormality occurs in a particular strand, the slab cutting allocation plan for all strands including the strand is re-edited, and each slab is given priority in the order of the roll schedule. We have developed a method for supplying slabs in continuous casting, which is characterized by carrying out cutting assignments of the strands and directly feeding the slabs to the rolling process, and succeeded in maintaining the specified energy-saving effect and high productivity.

The method of the present invention will be explained in more detail below.

Now, in the initial stage of casting, a slab cutting plan is once assigned to each strand on the premise that a plurality of strands are cast in parallel in the same casting state. However, as casting progresses, if an abnormality occurs in the casting condition of any of the strands, if the abnormality is a serious defect, the slab containing the abnormality will be scrapped, and if the abnormality is minor, it will be discarded. As the material is of a lower grade, it becomes impossible to perform the planned cutting of normally ordered slabs, such as transferring to demoted slabs of different specifications, and the cutting order is reversed.

In addition, the solidification state on both sides of the slab changes,
When expansion called bulging occurs, the casting speed of the strand is reduced to create a strong solidified thickness, but this causes the casting speed of the strand to be inconsistent with the others. A reversal occurs in the cutting order.

As mentioned above, the casting condition may have been disturbed and the strands may have been cut in the cutting order assigned to each strand at the beginning of casting.
If a situation occurs in which the roll schedule cannot be satisfied, the allocation of details of uncut slabs is canceled once, and the slabs corresponding to the abnormal area are reassigned in the order in which they are delivered, avoiding the abnormal area. A strand that can be secured is searched for, and a new cutting plan for the slab is assigned to that strand. Along with this, for all slabs following this slab,
Reallocation is performed so that the predetermined order of dispatch can be maintained.

As described above, in the present invention, when a change in the order of the pieces to be ejected due to disturbances in the casting condition is known, a new cutting plan is created to avoid this, and the roll schedule of rolling is always guaranteed.

An embodiment of the present invention will be described in which a specific roll schedule is secured in the case where a casting abnormality occurs with respect to the cutting plan of a two-strand continuous casting machine.

Figure 1 shows molds M ₁ and M ₂ with strands S ₁ and S ₂
In this example, slabs 1 to 8 (slabs in this example) to be cut to each strand S ₁ and S ₂ of specified dimensions are cast for each strand according to the roll schedule according to the manufacturing plan in advance. Allocate and distribute. FIG. 1 is a schematic diagram showing the situation where the casting is progressing and slabs 7 and 8 are being cast. In the figure, m indicates a meniscus.

By the way, as shown in Fig. 2, when the scheduled casting of the slab 7 is completed, if for some reason a sudden change in the melt level occurs and the slab 7 becomes stepped, it is necessary to place the slab 7 as it is on the roll scheduler. It becomes necessary to consider whether or not it is possible. That is, since the slab 7 is given the shortest allowable length lmin and the longest allowable length lmax, the length l from the planned cutting line 5a of the slab 5 to the abnormal start point 7a can be calculated by avoiding the abnormal area Δl. First, it is determined whether lmin<l<lmax is satisfied. In the case of l<lmin, a surplus material slab (an unplanned slab with the most general length specified) is allocated instead of the slab 7. The surplus material slab is sent, for example, to a cold piece treatment process, and maintenance treatment is performed in response to the abnormality.
Therefore, as a matter of course, slab 7 becomes a missing number, resulting in a hole in the roll schedule. Therefore, in the present invention, the slab allocation plan for slab 7 and thereafter is immediately re-edited.

Now, assuming that the casting speeds v ₁ and v ₂ of the strands S ₁ and S ₂ are maintained in Fig. 2, the scheduled cutting completion time of one strand is (l ₁ +l′+l ₇ )/v ₀ ……(1) and the expected cutting completion time of the slab to be cut next to slab 6 of strand S ₂ (i.e. slab 7) (l ₂ +l ₇ )/v ₂ ...(2) where l ₁ : slab 1 among uncut slabs; Total slab length of slab 3 and slab 5 l ₂ : Total slab length of slab 2, slab 4 and slab 6 in the uncut slab l ₇ : Cutting length of slab 7 l': Compare with surplus slab length, For strands that can be cut quickly,
At the same time as the slab 7 is newly allocated, the slab cutting allocation plan after the slab 7 is re-edited. In this way, when a casting abnormality occurs, the slab cutting allocation plan is re-edited to ensure that the roll schedule is satisfied.

Further, different embodiments of the reediting according to the present invention will be explained.

Even if casting is proceeding smoothly, there is a risk that the next charge of molten steel may arrive late in the continuous casting process, trouble may occur in the cutting process, or bulging may occur in the cast slab. In this case, the casting speed must be reduced.

In that case, a difference in casting speed occurs between strand S ₁ and strand S ₂ . FIG. 3 is a schematic diagram showing an example, _where the casting speeds v ₁ and v 2 of strands S ₁ and S ₂ are v ₂
> v ₁ , for the slab 2 being cut and the slab being measured at positions 30 and 31, the order of the pieces coming out of the immediately adjacent slabs 3 and 4 is already fixed and does not change.
The allocation of the next slab 5 is determined by the following procedure. In the figure, C of strand S ₁ indicates the cutter position (uncut), and C of strand S ₂ indicates the cutter position (cutting).

The expected time to complete cutting of slab 5 in strand S ₁ is calculated as (△l ₁ ′+l′ ₃ +l ₅ )/v _1. Next, the expected time to complete cutting slab 5 in strand S ₂ is calculated as (l′ ₄ +l ₅ )/v ₂ , compare the two, and allocate slab 5 to the strand whose expected cutting completion time comes earlier, and at the same time re-edit the slab cutting allocation plan for slab 5 and beyond.
l' ₃ , l' ₄ , l' ₅ indicate the lengths of slabs 3, 4, and 5.

As explained in detail above, according to the present invention, it is possible to significantly improve the productivity of direct rolling.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are schematic diagrams showing cutting assignments of strands according to the present invention. _S1 , _S2 ...Strand, _M1 , _M2 ...Mold.

Claims (1)

[Claims] 1. In the method of supplying slabs in direct rolling, in which multiple strand slabs obtained by continuous casting are cut in a planned manner and sequentially supplied in the order of the roll schedule in the direct rolling process, when a casting abnormality occurs in a specific strand, the casting of each strand is stopped. The method is characterized in that the cutting speed is determined, the cutting completion time of each strand to the slab to be cut is determined, the slab to be cut is assigned to the strand with the earliest cutting completion time, and the slab cutting assignment plan for all strands is re-edited. A method of supplying slabs in continuous casting.