JPH035898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for inserting a partition plate into a joint between different steel grades in continuous casting of molten steel in order to reduce defects at the joint.

Conventional technology When continuously casting molten steel with different compositions in a continuous casting method, a partition plate is inserted into the mold at the part where the composition changes to block the molten steel and minimize the composition mixing area. method is being done.

As shown in FIG. 5, an example of a conventional partition plate insertion method is to temporarily stop the injection of molten steel, and place iron plate partition plates 1 at both ends in the width direction of the mold on the upper surface of the molten steel.
A method in which molten steel of different steel grades is then injected to continue casting (Japanese Patent Application Laid-open No. 112431/1983, Continuous casting method for different steel grades)
However, the partition plate 1 is inserted by interrupting the casting, removing the immersion nozzle 2 from the mold 3, and then manually inserting the partition plate 1 into both ends in the width direction. This method has the major disadvantage that it requires manual insertion, which requires a considerable amount of time to handle the heavy partition plates (usually iron plates), resulting in poor workability and extremely dangerous work.

In addition, there is a high risk of deterioration of the surface quality and internal quality of the slab due to temporary interruption of casting, so the method of interruption of casting is to temporarily stop the flow of molten steel by closing the stopper 5 or the sliding nozzle. However, if the temperature of the molten steel is low (for example, below the solidification temperature +5° C.), the molten steel near the stopper or sliding nozzle solidifies when casting is interrupted, making it difficult to continue casting.

A dedicated insertion machine for partition plates (iron plates) is also known (US Pat. No. 3,534,804, etc.), but the device is complicated and expensive, and maintenance is also quite difficult.

In another method of inserting a partition plate, as shown in FIG. 6, the partition plate 7 is suspended from the bottom 12 of the molten steel container with a wire or a thin wire-like object, and as the molten steel container descends, it falls and floats on the mold. There is a method in which molten steel of a different type is injected, the weight of the molten steel pushes down the partition plate, and the hanging wire or thin wire is cut by the heat of the molten steel to complete the insertion of the partition plate.
Even with this method, the installation work is time-consuming and dangerous, it is necessary to interrupt the injection of molten steel, and the partition plate is not stable because it is not pressed sufficiently against the solidified shell in the mold. It was accompanied by drawbacks such as:

Problems to be Solved by the Invention The present invention has been made to advantageously solve the drawbacks of the prior art.

Means for Solving the Problems The present invention provides a method for fixing molten steel by attaching a jig to the lower part of a molten steel container, coupling a mounting rod to the inside of a partition plate, and rotatably locking its tip to the jig. This is a method for inserting a partition plate into a casting joint of different steel types, which is characterized by inserting the partition plate into the molten steel in a mold by pushing the partition plate into the molten steel in a mold by the movement of a container.

That is, in the present invention, during the conventional continuous casting of different steel types, the partition plate is inserted manually or by a special insertion machine, or the partition plate is placed on the mold and then the weight of the molten steel injected is used to solidify the partition plate into a solidified shell. Instead of the pressing method, an example will be explained below based on the drawings. As shown in FIG. During steady casting before inserting the partition plate, the tip of the mounting rod 20 is rotatably locked in the restraining part of the hanging jig 16, and the partition plate is tilted and placed on the mold cover 19. By raising the molten steel container 17 when inserting the partition plate, the partition plate is rotated and brought onto the mold, and by further lowering the molten steel container 17, the partition plate is placed on the mounting rod 2.
By being pressed against the coagulation shell and restrained by the shell, the partition plate is firmly fixed and the partition plate insertion is completed.

During this series of movements of the molten steel container rising and falling,
As shown in Figure 2, the mounting jig for the partition plate moves from position ○A before insertion to position ○B when the molten steel container rises, from ○RO to ○C when the molten steel container descends, stops at ○C, and then When descending, the partition plate is pressed and fixed against the solidified shell while remaining at the position of ○C, and as casting continues, the mounting rod is automatically removed from the hanging jig.

The third preferred application condition for the hanging jig is
As shown in the figure, the diameter A of the hanging arm portion 22 has a curvature greater than the diameter of the mounting rod of the partition plate, the position of the curved portion 23 is at the center in the thickness direction of the casting, and the outlet 24 of the mounting rod is located at the center of the hanging rod. It is larger than the jig diameter.

As shown in Figure 4, the shape of the partition plate used in this partition plate insertion method consists of a mounting rod 20 and a partition plate 14, and is designed to eliminate powder floating near the meniscus when inserted into the mold. It is advantageous to use a partition plate whose central portion has a convex shape such as a U shape or a V shape.

If a partition plate having a shape that does not allow powder to be removed easily is used, breakout may occur at this location during casting due to poor heat removal due to powder entrainment, which is extremely disadvantageous.

By adopting this method of inserting the partition plate, the partition plate can be inserted automatically using only the jig attached to the molten steel container and the vertical movement of the molten steel container, without using input or a special insertion machine. It is possible to effectively interrupt molten steel during continuous casting of different steel types.

Incidentally, iron is usually used as the material for the partition plate and the mounting rod, and the dimensions are as shown in Fig. 7, which covers most of the part from the mold opening 29 except for a part near the immersion nozzle 27, that is, the diagonal line in Fig. 7. Adjust so that the partition plate can be inserted into the partition plate insertion portion 28 shown by .

Regarding the width direction W of the mold, approximately
Insert the partition plate from a position 30 mm away to about 30 mm beside the immersion nozzle, and at a distance of about 15 mm from both long sides in the thickness direction T of the mold.

Therefore, the size of the partition plate is adjusted so that the ratio of the area of the blocking portion of the partition plate to the area of the mold opening is about 85 to 95%. In particular, regarding the thickness direction T of the mold, the gap between both long sides and the partition plate should be set to 20 mm or less in order to promote the coagulation shell restraining and fixing the partition plate when inserting the partition plate. is suitable.

Further, when the area of the mold opening changes due to changes in the casting width in continuous steel casting, it is advantageous to change the size of the partition plate according to the area of the mold opening.

The insertion of the partition plate is as shown in Figure 8. (A) When performing continuous casting of different steel types, insert the partition plate while a small amount of molten steel with the same composition as the front pot side remains in the molten steel container, and continue casting for a while. As shown in (B), when the partition plate is located below the discharge hole 34 of the immersion nozzle 31, molten steel of different compositions is injected from the ladle to ensure that the partition plate has a sufficient sealing effect. It is preferable to make this possible.

The length L of casting from the completion of iron plate insertion to the start of pouring into the rear pot is L = l + a + α (l: immersion depth of immersion nozzle (m), a: discharge hole diameter (m), α: allowance (m)) It is expressed as Therefore, the amount W of molten steel having the same composition as the front ladle that should remain in the molten steel container when inserting the partition plate is W = w × t × L × ρ × n (w: casting width (m), t: casting thickness ( m), ρ: specific gravity of molten steel (=
7.0t/m ³ ), n: number of outlets from the molten steel container), therefore, W=w×t×(l+a+α)×n.

Hereinafter, embodiments of the present invention will be described in comparison with conventional examples.

Examples Example 1 In a curved type (10.5R) continuous casting equipment, the casting width (mold width) is 1800 mm, the slab thickness (mold thickness)
253mm, Molten steel composition (%) C: 0.13, Mn: 1.40,
Si: 0.2, P: 0.018, S: 0.005, Sol-Al:
0.025, Fe: The remainder is 4.1t of molten steel left in the molten steel container (tandice) during casting, and the width of the partition plate is
Insert two pieces of 780mm x slab thickness 230mm x plate thickness 9mm, one on each side of the immersion nozzle, and leave it as it is.
After casting 600mm, molten steel with different compositions, ie molten steel composition (%), C: 0.45, Mn: 0.75, Si: 0.30,
P: 0.020, S: 0.005, Sol-Al: 0.025, Fe: Continue to cast the remaining parts by continuous casting of different steel types, and as shown in Figure 9, there is a remarkable effect of reducing the mixing of components compared to when no partition plate is used. It was hot.

The partition plate was inserted automatically by raising and lowering the molten steel container, and during this period, the partition plate was inserted stably at a casting speed of 0.5 m/min without stopping casting. Therefore, there were no cracks or other flaws on the surface of the slab in the partition plate insertion portion, and a good casting surface was maintained.

Example 2 In the conventional method, when inserting a partition plate, the casting speed was reduced to zero, and it took about 2 minutes to insert the partition plate and restart casting. There were many cases in which casting became impossible due to clogging or loss of control.

Ingredient range (%) C: 0.09~0.15, Mn: 0.75~
1.5, Si: 0.2~0.3, P: 0.008~0.010, S: 0.005
~0.010, Sol-Al: 0.20-0.30, Fe: the remainder. When the partition plate insertion method according to the present invention was applied to molten steel, as shown in Fig. 4, the result was good when the superheat in the molten steel container was +3℃ or higher. The workability of inserting partition plates was excellent, and we were able to insert partition plates in all cases where it was necessary (insertion rate: 100%).

[Brief explanation of the drawing]

FIG. 1 shows an example of the partition plate insertion method according to the present invention, in which 1 is an elevational view and 2 is an enlarged perspective view of the α section. FIG. 2 is an elevational view showing the operation of the mounting rod of the partition plate and the jig based on the present invention, and FIG. 3 is an explanatory diagram showing an example of preferable conditions that the hanging jig based on the present invention should have.
FIG. 4 is a perspective view showing an example of the shape of a partition plate according to the present invention, FIG. 5 is a perspective view showing an example of a conventional partition plate insertion method, and FIG. 6 is a perspective view of another conventional partition plate insertion method. FIG. 7 is a plan view illustrating the dimensions of the partition plate according to the present invention; FIG. 8 is an explanatory diagram illustrating the method of inserting the partition plate according to the present invention;
FIG. 9 is a graph showing the mixed state of different steel components according to the present invention and the conventional method, and FIG. 10 is a graph illustrating operational differences between the present invention and the conventional method. 14... Partition plate, 16... Hanging jig, 17...
Molten steel container, 20...Mounting rod.

Claims (1)

[Claims] 1 Attach a jig to the lower part of the molten steel container, connect a mounting rod to the inside of the partition plate, and rotatably lock the tip of the rod to the jig, so that the partition plate is moved into the mold by the movement of the molten steel container. A method of inserting a partition plate into a continuous casting joint of different steel types, which is characterized by inserting the partition plate into the molten steel.