KR20100049813A - Continuous casting method for reducing width deviation of ferritic stainless steel first-slab - Google Patents

Abstract

PURPOSE: A continuous casting method for reducing the width deviation of a ferritic stainless steel first slab is provided to reduce the slab edge faults of a hot rolled coil by reducing the width deviation of a first slab during a continuous casting process. CONSTITUTION: A continuous casting method for reducing the width deviation of a ferritic stainless steel first slab is as follows. Molten steel flows into a mold through a ladle-tundish. The molten steel flowing into the mold is first cooled. The molten steel is second cooled. The rising acceleration of a first slab is controlled less than 0.06m/min∧2. The maximum width deviation of the first slab is less than 10mm.

Description

Continuous casting method for reducing width deviation of ferritic stainless steel first-slab

The present invention relates to a continuous casting method of ferritic stainless steel, and more particularly, to a continuous casting method for improving slab edge defects of hot rolled coils by reducing the width deviation of the ultra cast steel by controlling the speed of acceleration of the initial casting of the continuous casting. It is about.

In general, the slab edge defects due to the width rolling in the hot rolling process originate from the cast steel, and when the width of the cast steel is excessively large compared to the width of the final product, there is a problem that the width depth of the slab edge defect increases. . Thereafter, a slitting process is performed, and even though the slitting process is performed, defects remain in the final product.

On the contrary, if the width of the cast steel is excessively small compared to the width of the final product, it cannot be offset by the width spread in the hot rolling process, resulting in a problem that the width of the product is finally insufficient.

Conventional known techniques for solving this problem have been solved by adjusting the width of the slab through the variable width of the mold during continuous casting, but there is a problem that can not be applied to this technique where there is no variable width equipment.

In addition, a method of changing the shape of the short side of the mold in order to reduce the width deviation on the upper and lower surfaces of the cast is proposed, but this technique is also a concept different from the longitudinal width deviation of the cast.

In other words, the present invention for reducing the width deviation of the initial casting of the continuous casting is proposed a control method of the playing conditions for minimizing the width deviation of the ultra cast without the need for a width-variable equipment, the patent has not been reported yet.

For reference, the slab width deviation means a difference between the actual slab width and the indicated slab width, and the ultra slab means a slab that is first cast after starting a continuous casting. Part and last casting can be defined as the end cast.

The present invention has been made to improve the above-mentioned problems. In the continuous casting process, slab edge defects of hot rolled coils can be eliminated by reducing the width deviation of the ultra casts by controlling the speed of acceleration of the initial cast of the continuous cast without the need for variable width of the mold. It is an object of the present invention to provide a continuous casting method of ferritic stainless steel that can be improved.

In order to achieve the above object, the continuous casting method of the present invention includes a primary cooling, a circumferential acceleration acceleration section, and a secondary cooling process after molten steel flows into a mold through a ladle-tundish to cast the initial casting of the continuous casting. In the continuous casting method of ferritic stainless steel comprising a,

It includes controlling the circumferential speed rising acceleration of the ultra-thin piece to 0.06m / min ² or less.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention, while exploring a method for suppressing the phenomena of the increase in the initial casting of the continuous casting early casting causing the slab edge defect of the hot rolled coil, if appropriately controlling the speed of acceleration of the continuous casting initial casting, the formation of the solidification cell It was found that it is possible to suppress the phenomena of the increase in the width of the cast by improving the resistance to deformation.

First, Figure 1 shows a schematic diagram of a stainless steel continuous casting apparatus, the present invention is the molten steel 4 is introduced into the mold (5) through the ladle (1)-tundish (2) according to the conventional continuous casting method When the solidification starts in the mold 5, a solidification cell is formed, and then the solidification cell becomes thicker toward the lower side of the secondary cooling stand 7 so that the solidification is finally completed, and thus, the cast piece 8 may be obtained.

At this time, when the steel solidifies, volume shrinkage occurs due to a temperature drop, thereby reducing the width of the cast steel. However, when the coagulation cell is weak, the amount of shrinkage due to temperature drop is reduced by the iron static pressure 6 generated in the cast itself by high heat, and in some cases, the expansion occurs more than the width of the mold.

As a result, the width of the final cast steel is determined by the interaction between the iron static pressure and the volume shrinkage due to the temperature drop. By adjusting the shrinkage correction factor, it is possible to produce casts with small width deviations.

However, as can be seen in Figure 2, it can be seen that the width deviation is different depending on the length direction of the cast in the ultra cast. Looking in detail, it can be seen that the head portion (Head) of the ultra-thin piece has a relatively large width deviation, and finally the tail portion (Tail) of the ultra-thin piece is equal to the normal width.

Figure 3 shows the internal flow schematic diagram of the middle cast and ultra cast during continuous casting, the cause of this phenomenon, as shown in Figure 3, in the case of ultra cast (symbol F) due to the dummy bar (symbol C) due to the dummy bar It can be seen that the molten steel flow zone is active due to the short molten steel flow zone (V _c <V _F ).

As a result, the temperature is higher in the vicinity of the solidification cell of the ultrathin slab than the middle cast (T _c <T _F ), and the thickness of the solidification cell becomes relatively thin (S _c > S _F ), thereby weakening the deformation resistance against the positive static pressure. This is caused by a big explosion.

Thus in the present invention, in order to suppress the ferritic stainless steel, when continuous casting Chaozhou convenience pokjeungga phenomenon, continuous by controlling the peripheral speed of rise acceleration to secure Chaozhou solidification cells strength during casting, the peripheral speed of the rising acceleration 0.06m / min or less ² To control. At this time, the circumferential speed increase acceleration can be controlled in the interval from the start of the casting to the target circumferential speed from the zero circumferential speed.

When the circumferential ascending acceleration exceeds 0.06 m / min ² , the maximum variance value due to the decrease in solidification cell formation of the ultra cast may increase, which may affect the slab edge defects of the final product. It is preferable to control to min ² or less.

 The maximum width deviation of the ultrathin sheet satisfying the present invention is preferably controlled to 10 mm or less, which is a range that does not affect slab edge defects.

As described above, according to the present invention, it is possible to manufacture ferritic stainless steel in which slab edge defects of the hot rolled coil are improved by reducing the width deviation of the ultra cast steel in the continuous casting process without the need for the mold width changing equipment.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

The width deviation of the ultra cast steel was measured while changing the initial circumferential acceleration in the range of 0.06 to 0.20 m / min ² in the ferritic stainless steel containing 11 to 13% chromium, and the results are shown in Table 1 and FIG. 4. In this case, the second cooling non-aqueous condition of the ultra cast is a condition where the non-aqueous quantity is 120 to 105% in a section of 55 to 78% of the circumferential speed of the middle cast compared to the non-amount at the circumferential speed of the middle cast.

TABLE 1

Classification Main speed ascent acceleration (m / min ² ) Average Width Deviation (mm) Maximum Width Deviation (mm) Comparative Example 1 0.20 14.3 23 Comparative Example 2 0.10 12.0 20 Comparative Example 3 0.08 8.5 21  Inventive Example (1-4) 0.06 0.6 7 0.06 5.5 9 0.06 4.6 8 0.06 3.8 9

Figure 4 is a graph showing the effect of reducing the width of the ultra-thin slab in the invention and comparative examples of the present invention, as shown in Figure 4 and Table 1, the maximum width deviation and in the case of the invention examples of the initial circumferential speed increase acceleration 0.06m / min ² It can be seen that the average width deviation is reduced to satisfy the maximum width deviation targeted by the present invention.

On the other hand, in case of Comparative Examples (1-3) that do not satisfy the circumferential ascending acceleration of the present invention, the maximum width deviation is 20 to 23 mm, and the slab edge defect problem exceeds 10 mm, which may affect the slab edge defect. I can see that there is.

1 shows a schematic view of a continuous casting apparatus.

Figure 2 is a graph showing the width deviation along the longitudinal direction of the continuous casting ultra-thin casting.

Figure 3 shows the internal flow schematic diagram of the middle cast and ultra cast during continuous casting.

4 is a graph showing the effect of reducing the width of the ultra-thin slab in the invention and comparative examples of the present invention.

<Description of the symbols for the main parts of the drawings>

1: ladle 2: tundish

3: immersion nozzle 4: molten steel

5: mold 6: iron positive pressure

7: 2nd cooling stand 8: cast

Claims (2)

In the continuous casting method of the ferritic stainless steel comprising the first cooling, circumferential acceleration acceleration section and the second cooling process after the molten steel flows into the mold through the ladle-tundish to cast the initial casting of continuous casting, Continuous casting method for reducing the width deviation of the ultra-thin slab of ferritic stainless steel comprising the control of the circumferential ascension acceleration of the ultra-thin cast to 0.06m / min ² or less. The continuous casting method of claim 1, wherein the maximum width deviation of the ultra cast steel is 10 mm or less.

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