JPH0481247A - Method for continuously casting cast bloom having unsolidified part in inner part - Google Patents

Abstract

PURPOSE:To obtain a high temp. cast bloom without defect having unsolidified part in inner part and to achieve direct rolling by forming recessed part at each expected cutting position in the cast bloom, promoting cooling at this recessed part and cutting this recessed part. CONSTITUTION:By pressing at mold side 1 to thickness direction positioned at inside of curve in bending part at about 100mm/min with thickness changing command from CPU 11, the thickness of cast bloom 8 is reduced by >= 20 mm to form the recessed part 9 having the prescribed depth. The pressing force at this time is intensity level applied with a simple equipment. As the recessed part 9 completes solidification earlier than that at the other thick part, the recessed part 9 is tracked with the CPU 11 and when the recessed part 9 reaches to position of a torch 12, the recessed part 9 completing the solidification is cut with the torch 12 under cutting command from the CPU 11. Then, drawing velocity of the cast bloom 8 is controlled so that unsolidified part 13 remains in the inner part of cut cast bloom 8.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a continuous casting method for bloom slabs, which enables cutting slabs with unsolidified parts remaining inside the solidified shell. It is.

<Conventional technology> In continuous casting equipment, in order to save energy and reduce strength, hot charging of high-temperature slabs is carried out directly to the rolling equipment that follows, or heating equipment is installed between the continuous casting equipment and the rolling equipment. The method of rolling a continuously produced slab by raising the temperature to a suitable rolling temperature is applied to thick plates, cold-rolled thin plates, large steel bars, etc.

In this case, you are subject to restrictions on factory layout, you lose flexibility in continuous casting and rolling operations, there is no guarantee that the slab temperature will always be high and constant, and it is compatible with existing continuous casting equipment. There were problems such as not being able to do so.

Now, in order to systematize the handling of slabs as described above by using the current equipment arrangement or by making slight improvements to the equipment, continuously cast slabs must be maintained at a temperature as high as possible above a certain temperature.
It is necessary to. In order to effectively utilize the sensible heat and latent heat of the spinning J1 obtained with the existing continuous casting equipment, it is effective to use the casting J1 with an unsolidified part left inside the solidified shell, and various proposals have been made in the past. being done.

For example, in JP-A-56-105856 and JP-A-56-105858'; 3, a solidified shell having an unsolidified portion inside is pulled out from a mold and is pressed at predetermined pitches using a press machine to form four parts. Then, by promoting cooling of the recesses, the unsolidified parts inside the solidified shell are solidified at predetermined pitches, and then cut by a cutting device at each recessed pitch to form a VF of a predetermined length with an unsolidified part inside.
Continuous casting of pieces has been proposed.

However, in the prior art described above, a press device is required to press the slab in order to form four parts in the slab within the continuous casting device, but when pressing, the press device must be moved in synchronization with the speed of removing the slab. There is. For this reason, it is essential that the press device be located downstream of the continuous casting device, where there is no risk of bulging occurring even if the slab is not supported by guide rolls or the like.

This is because it is necessary to secure a space on the slab road for the pressing device to move in synchronization with the slab, and it is not possible to install slab support devices such as guide rolls in this space. It is.

Pressing of slabs by a press device in the downstream region of the continuous casting device is performed when the solidified shell has grown thick, and a pressing pressure of about 100 tons is required, resulting in major damage to equipment and increased costs. Furthermore, when a concave portion is formed in the slab by pressing with a press device, tensile stress acts on the inside of the solidified shell, which tends to cause internal cracks and cause internal defects in the slab.

゛In addition, in the process of moving the slab that is continuously pulled out from below the mold in JP-A-56-148462 and JP-A-577370, the unsolidified portion inside the slab is prevented from flowing out when the slab is cut. It has been proposed that only the cut portion is cooled and solidified using a spray nozzle or the like, and the unsolidified portion is retained inside the slab other than the cut portion.

However, there is a limit to the ability to remove heat through cooling using spray nozzles, etc., and it is difficult to completely solidify only the cut section of the slab, which not only lacks reliability.
Depending on the type of steel, cracking may occur due to strong cooling, which reduces yield.

<Problems to be Solved by the Invention> The present invention solves the problems of the prior art described above, and can cut slabs using simple equipment without requiring large pressing forces while preventing defects such as internal cracks in slabs. Bruf that has an uncoagulated part inside that can completely coagulate the area. Cast J4
The aim is to provide a continuous casting method.

<Means to solve the problem> Is the inventor of the slab continuous #7? In the casting equipment, it is possible to easily change the mold width during casting using a mold width changing device, which prevents problems such as internal cracks. The present invention was achieved as a result of focusing on changing the thickness and carrying out various tests.The gist of the invention is as follows.

The present invention provides a curved bloom continuous casting mold comprising a pair of mold sides in the thickness direction and a pair of mold sides in the width direction which are disposed so as to sandwich the mold sides in the thickness direction from both sides. When continuously casting a bloom slab using the apparatus, the solidified shell that is cast into the mold and includes an unsolidified portion inside is placed on the inside of the circular arc of the curved part of the slab among the pair of mold sides in the thickness direction. The thickness is reduced by pressing only the directional mold sides perpendicularly to the slab drawing direction by a slab pressing means, and recesses are formed at each planned cutting position of the slab to promote cooling of the recesses. This method relates to a method for continuous casting of a bloom slab having an unsolidified part inside the shell, characterized in that the unsolidified part inside the shell is solidified at each planned cutting position of the slab, and then the recessed part is cut by a cutting means. .

<Operation> Of the pair of mold sides in the thickness direction, only the mold side in the thickness direction located inside the arc of the curved part of the slab is pressed during casting to reduce the thickness on one side and form a recess at the planned cutting position of the slab. do. One side, which is the outer side of the arc of the curved part of the slab, remains in a continuous and flat shape, so the slab can be pulled out without causing bulging on the lower surface.

Cooling of the concave portions of the slab is promoted, and a solidified shell wall is formed by the development of a solidified shell, thereby making it possible to obtain a slab in which other unsolidified portions are enclosed. In addition, in the part where the thickness of the slab is changed by forming a concave part, after passing through the mold, the solidified shell is not supported by rolls, so the mold width is preferably set to a predetermined width of 600 mm or less to prevent bulging.

In addition, the mold side in the thickness direction located inside the arc shape of the mold is periodically
The thickness reduction is 2 when pressing at a thickness change speed of about 1/min.
It is preferable that the thickness of the slab be 0 or more and that the thickness of the slab in the recess be 20 m or more. If the thickness is reduced to less than 20 mm, cooling of the recessed portion will be insufficient, making it difficult to reliably form a solidified shell wall.

Of course, the casting speed is controlled so that unsolidified portions remain inside the slab other than the cut portion of the slab.

In this way, the thinner concave portions complete solidification earlier than other portions, so the solidified portions are tracked and cut with a torch to obtain a slab with unsolidified portions remaining inside.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. Second
The figure shows a mold of a bloom continuous casting apparatus according to the present invention, and the mold has a pair of thicknesswise mold sides 1.1 and a pair of widths arranged to sandwich the thicknesswise mold sides 1.1 from both sides. The direction mold side consists of 2.2. Then, an upper drive cylinder 3 and a lower drive cylinder 4 are connected as pressing means behind the thickness direction mold side 1, which is located on the inside of the arc of the curved part of the slab, among the pair of thickness direction mold sides 1.1. 3.4 is activated to make one of the mold sides 1 in the thickness direction movable in the thickness direction.

FIG. 1 shows an embodiment in which the present invention is applied to a plume continuous casting apparatus, in which molten steel 5 is injected into a mold 10 consisting of a mold side 1 in the thickness direction and a mold side 2 in the width direction, and passes through a secondary cooling zone 6 to a solidification shelf. During growth, a drawn slab 8 is continuously obtained using pinch rolls (not shown).

In the present invention, when the planned cutting position of the slab 8 is cast into the mold 10, a thickness change command from a tracking computer (CPU) 11 is issued to the mold in the thickness direction, which is located inside the arc of the curved part, while casting is continued. Side 1 is 100m by upper drive cylinder 3 and lower drive cylinder 4
After reducing the thickness of the slab 8 by 20 mm or more by pressing at a speed of about m/min to form a recess 9 of a predetermined depth, the operation is immediately performed to enlarge it and return it to its original position.

Since the concave portion 9 formed in the slab 8 is thin, solidification is completed faster than other thick portions. Therefore, the concave portion 9, which is the thickness change portion, is tracked by the tracking computer 11, and the concave portion 9 is located at the position of the torch 12. When this point is reached, the recess 9 that has been solidified is cut by the torch 12 in response to a cutting command from the tracking computer 11. Needless to say, the drawing speed of the slab 8 is controlled so that the unsolidified portion 13 remains inside the slab 8 that is cut at this time.

For example, in continuous casting of a bloom with a thickness of 300+ nm and a width of 400 m, if the cutting command length is 12 m and the distance from the mold to the torch cutting is 30 m, the casting length is 12 m.
Each time, the mold side in the thickness direction located inside the arc of the curved part of the slab was pressed for 18 seconds at a thickness change rate of 100 mm/min, the thickness was reduced by 30 cylinders, and then immediately pulled back for 18 seconds.
The thickness of the slab 8 is increased by 30+ nm and returned to its original position to form a recess 9 in the slab 8. As a result, the slab 8 is expanded as shown in FIG.
Recesses 9 with a thickness of 270M are formed at a pitch of 12m, and the recesses 9 can be cut with a torch 12 as completely solidified parts.

Generally, the thickness of the solidified shelf formed in the slab 8 is d(+n
m) is expressed as d = 27J (t: elapsed time from mold casting), and in the case of a thickness of 270 mm, solidification is completed in about 25 minutes. Therefore, when the distance from the mold 10 position to the torch 12 position is 30 m, the slab drawing speed is 3.
If casting is performed at a rate of 0 m/25 min to 1.2 m/min, solidification will be completed only in the 270 mm thick portion, and an unsolidified portion will remain in the 300 mm thick portion.

Thus, if the four parts 9 with a thickness of 17+270 mm are tracked and cut by the computer 11 as described above, 30
It is possible to leave the unsolidified portion 13 in the 0+nm thick portion without causing any internal cracks.

<Effects of the Invention> As explained above, according to the present invention, a recess can be formed in a bloom slab using simple equipment without requiring a large pressing force. Since the recessed portion, which has become thinner due to the thickness change, solidifies early to form a partition wall, by cutting the recessed portion, an unsolidified portion can be left in other parts of the slab. Therefore, a defect-free high-temperature bloom slab of 1100° C. or higher can be obtained, and rolling without heating can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of a mold according to the present invention, and FIG. 3 is an explanatory diagram showing the state of a bloom slab according to the present invention. 1...Thickness direction molding 1: side, 2...Width direction molding side, 3..." two-part drive cylinder, 4...lower drive cylinder, 5...molten steel, 6...secondary Cooling zone, 7... Solidified shell, 8... Slab, 9... Four parts, 10... Mold, 11... Tracking computer, 12... Torch, 13... Unsolidified part .

Claims (1)

[Claims] A bloom slab is produced by a curved bloom continuous casting machine equipped with a mold consisting of a pair of thickness direction mold sides and a pair of width direction mold sides arranged to sandwich the thickness direction mold sides from both sides. During continuous casting, the solidified shell, which is cast into the mold and includes an unsolidified portion inside, is pressed into a slab only on the mold side in the thickness direction that is located inside the arc of the curved part of the slab among the pair of mold sides in the thickness direction. The unsolidified portion inside the solidified shell is removed by pressing at right angles to the slab drawing direction to reduce the thickness, forming recesses at each planned cutting position of the slab, and promoting cooling of the recesses. 1. A continuous casting method for a bloom slab having an unsolidified portion inside, the method comprising: solidifying the bloom slab at each planned cutting position, and then cutting the recessed portion by a cutting means.