JP3370476B2 - Winding method of twin-drum continuous cast slab - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon steel sheet slab by a twin-drum type continuous casting machine.

[0002]

2. Description of the Related Art FIG. 1 is an explanatory view of an example of twin drum type continuous casting. In twin-drum continuous casting, two horizontal casting drums 1-1 and 1-2 are arranged close to each other in parallel on the left and right, and side weirs 2-1 and 2-2 are provided on the front and rear end faces of the casting drum. Is placed in close contact with the end surface of the casting drum. Both end faces of the casting drum rotate in the directions of arrows 4-1 and 4-2, respectively, while rubbing the side weirs.

Molten steel 3 is poured into a basin formed by the upper surface of the casting drum and the side dam. The molten steel in the pool is cooled by the casting drum and forms solidified shells 5-1 and 5-2 on the surface of the casting drum. Solidification shells 5-1 and 5-
No. 2 grows while moving following the rotation of the casting drum, and is joined to each other at the minimum gap 7 between the drums to form a slab 6 and is sent downward.

In the figure, 8 is a guide, and 9 is a conveying roller group, for example. The slab 6 sent out from the casting drum is guided by the guide 8 to reach the conveying roller group 9,
It is transported by the transport roller group 9, reaches the take-up reel 10, and is wound up by a coil.

According to this twin-drum type continuous casting method, a thin plate slab of carbon steel having a plate thickness of, for example, 0.5 mm can be manufactured. However, since this thin plate slab has a sufficiently thin plate thickness, it is hot-rolled or cold-rolled. It is preferable because the container and other products can be manufactured by performing the forming process without performing hot rolling. However, according to the knowledge of the present inventors, since the thin plate slab has poor adhesion of the scale, there is a problem that the scale peels off and scatters during the molding process to impair the working environment.

That is, in FIG. 1, the cast piece 6 is a casting drum 1.
Immediately after leaving -1, 1-2, the temperature is extremely high, and thus a thick scale is generated on the slab while reaching the take-up reel 10. Japanese Unexamined Patent Publication No. 61-222611 describes a device in which shots are sprayed onto a slab and then hot-rolled with an in-line mill. However, because of the hot rolling, the manufacturing cost of the thin plate is higher than that in the case where the thin plate slab is directly formed.

Japanese Unexamined Patent Publication No. 63-26240 describes an apparatus in which the entire structure from the twin drum to the take-up reel is covered with a casing in an unoxidized atmosphere. However, in this device, the casing becomes extremely large, and a large amount of gas for adjusting the atmosphere is required to maintain the interior in a non-oxidizing atmosphere, resulting in high operating cost. Also, Japanese Patent Application No. 6-092852 describes a method of reducing the amount of scale generated by shutting off the slab from the oxygen source until the temperature reaches 800 ° C. However, as will be described later, unless special measures are taken in the winding temperature, a scale with insufficient adhesion occurs.

[0008]

DISCLOSURE OF THE INVENTION In the production of a low carbon steel thin plate slab by twin drum type continuous casting, the present invention is a method of winding a thin slab that does not cause the scale to peel off when used for forming. The challenge is to provide a method of collecting.

[0009]

Means and Actions for Solving the Problems The present invention is
(1) A method for winding a twin-drum type continuous cast slab, which comprises descaling a carbon steel slab cooled to 400 ° C to 700 ° C and winding it on a coil. (2) Temperature is 70
Descaling of carbon steel sheet slabs above 0 ° C, immediately 400
A twin-drum continuous cast slab winding method, which comprises forcibly cooling to ˜700 ° C. and winding the coil.

The present inventors have used a twin-drum type continuous casting machine having a drum width of 350 mm and a drum diameter of 400 mm to rotate the drum at a peripheral speed of 40 m / min, and aluminum-killed steel having a carbon content of 0.05 wt%. The molten metal of No. 1 was poured to produce a thin plate slab having a plate thickness of 1.0 mm. Soso Drum 1-
The total length of the thin plate slabs from 1, 1-2 to the take-up reel 10 is about 25 m, and the temperature of the thin plate slabs on the take-up reel 10 when forced cooling is not performed during this period is 1000 m.
~ 1100 ° C.

First, the invention (1) will be described. The present inventors arranged a bending type descaler on the entrance side of the take-up reel 10 of FIG. 1 at a position 5 m away from the take-up reel 10. A cold air nozzle was arranged between the twin drums 1-1 and 1-2 and the bending type descaler. The inventors of the present invention sprayed cold air from a cold air nozzle onto a thin plate slab to adjust the temperature of the thin plate slab as shown in Table 1, descaled with a bending type descaler, and wound the coil with a winding reel 10.

The wound coil was removed from the winding reel 10, cooled to room temperature, then rewound and a sample was taken therefrom to test the adhesion of the scale formed after descaling.

The adhesiveness of the scale formed after descaling was determined by marking the surface of the sample with a knife so as to form a 10 mm-cornered crevice with a depth reaching the substrate, and bending it to 90 ° with a bending radius of 20 mm to obtain an adhesive tape. Was attached, peeled off, and the area of the scale attached to the peeled off adhesive tape was measured to evaluate. That is, the ratio of the area of the scale attached to the adhesive tape to the total surface area is shown in Table 1 as the adhesion of the scale formed after descaling. Table 1
Where ⊚ has a scale adhesion of less than 0 to 5%, and ○ means 5
% Is less than 10%, Δ is less than 10% to less than 30%, and X is more than 30%.

[0014]

[Table 1]

As shown in Table 1, when the temperature during descaling exceeds 700 ° C., even after descaling, the scale formed on the surface of the thin plate slab (scale formed after descaling) adheres The sex is insufficient. On the other hand, when descaling was performed at 700 ° C. or less, the scale adhered to the adhesive tape was slight, and the adhesion of the scale formed after descaling was good. The scales that had good adhesion and were formed after descaling were investigated in detail. All of them had a thickness of 15 μm or less, and the structure thereof was so thin that Fe ₂ O ₃ in the outermost layer was not observable. Fe ₃ O ₄ 70% between steel
It was a mixed layer of FeO and Fe ₃ O _{4 described} above. This scale was a uniform black skin film and densely covered the surface of the thin plate slab.

The present inventors have found that the C content is 0.02 to 0.08 wt.
% For various low carbon steels, the plate thickness is 0.5 to 2.0 mm
Various thin plate casts were prepared and the same test as in Table 1 was repeated, but in any case, when descaling was performed at more than 700 ° C., the adhesion of the scale formed after descaling was insufficient. By setting the temperature to 700 ° C. or lower, a scale obtained after descaling with good adhesion was obtained.

On the other hand, when descaling is performed at less than 400 ° C., the reaction temperature of winding and unwinding the thin slab becomes large due to the low temperature, and the surfaces of the thin slab rub against each other, resulting in co-deviation flaws. There is a problem that it easily occurs. If the descaling temperature is lower than 400 ° C and the temperature is low, there is no problem with the adhesion of the scale after descaling, but descaling should be performed at 400 ° C or higher to prevent the occurrence of co-deviation defects. Is preferred.

Based on the above findings, in the invention of (1) above, a thin plate cast piece of carbon steel cooled to 400 to 700 ° C. is descaled and wound into a coil.

Next, the invention (2) will be described. The present inventors used the apparatus described in Table 1 and further arranged a quenching apparatus between the bending type descaler and the take-up reel 10. This quenching device sprays cooling water from a nozzle onto a thin plate slab running between the bending descaler and the take-up reel 10 to quench it.

[0020]

[Table 2]

The inventors of the present invention have used this apparatus to obtain an aluminum-killed steel having a carbon content of 0.05 wt% and a plate thickness of 1.0 m.
m thin plate slab was manufactured. The peripheral speed of the twin drum is 40m.
/ Min. At this time, the thin plate slab was descaled at 900 to 1000 ° C., immediately thereafter it was rapidly cooled to the temperature shown in Table 2 by a quenching device, and wound on a coil by a winding reel 10.

The wound coil is removed from the winding reel,
After cooling to room temperature and then rewinding, a sample was taken from this and the adhesion of the scale formed after descaling was tested. The adhesion of scales produced after descaling was investigated by the same method as described in Table 1.

As shown in Table 2, when the coiling temperature is higher than 700 ° C., even if descaling is performed, the adhesion of the scale on the surface of the thin plate slab formed thereafter is insufficient. Meanwhile, 700 ° C
When wound up below, the adhesion of the scale produced after descaling was very good. The scale produced after descaling, which has good adhesion, was investigated in detail. In this case as well, the thickness is 15 μm or less, and the structure is shown in Table 1.
As described above, Fe ₃ O ₄ contains 70% or more of FeO and Fe.
It was a mixed layer of ₃ O ₄ . The scale had a uniform black skin film and uniformly covered the surface of the thin plate slab.

The present inventors have found that C is 0.02 to 0.08 wt.
% For various low carbon steels, the plate thickness is 0.5 to 2.0 mm
Although various thin plate casts were prepared and the same test as in Table 2 was repeated, in any case, when the coil was wound at more than 700 ° C, the adhesion of the scale formed after descaling was insufficient, By setting the temperature to 700 ° C. or less, a scale having excellent adhesion and formed after descaling was obtained. It should be noted that winding at 400 ° C. or lower is not preferable because of the occurrence of misalignment flaws.
Therefore, the winding temperature is preferably 400 ° C to 700 ° C.

Based on the above findings, in the invention of the above (2), the thin plate cast piece of carbon steel having a temperature higher than 700 ° C. is descaled,
Immediately forcibly cool to 400 to 700 ° C. and wind on a coil.

The present inventors carried out descaling using a sand blaster of carborundum particles instead of the bending scaler.
In the case of a thin plate slab cooled to 0 to 700 ° C, the adhesion of the scale formed after descaling is excellent, and similarly to Table 2, when it is forcibly cooled to 400 to 700 ° C immediately after descaling, it can be formed after descaling. The adhesion of the scale was good. Further, instead of the quenching device that blows cooling water from the nozzle, a quenching device that blows cold air was used, but the same results as in Table 2 were obtained.

Although the thin plate slab produced by the method of the present invention was subjected to the forming process without hot rolling or cold rolling, the scale splattered as compared with the conventional thin plate slab. The work environment was able to be improved greatly because there was no.

[0028]

EFFECTS OF THE INVENTION According to the present invention, it is possible to manufacture a thin plate slab in which scale is difficult to peel off. Therefore, it is possible to significantly reduce problems in the work environment such as scatter of scales in the subsequent process.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of twin-drum type continuous casting.

[Explanation of Codes] 1 (1-1, 1-2): Casting drum, 2 (2-1, 2)
-2): Side weir, 3: Molten steel, 4 (4-1, 4-
2): Drum rotation direction, 5 (5-1, 5-2): Solidified shell, 6: Thin plate cast, 7: Drum gap minimum part,
8: Guide guide, 9: Conveying roller, 10: Take-up reel.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Imamura Akira Imamura 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Technology Development Department (72) Inventor Yoshikatsu Nohara 20-1 Shintomi, Futtsu City, Chiba Prefecture (56) Reference JP-A-5-154652 (JP, A) JP-A-61-206507 (JP, A) JP-A-61-222611 (JP, A) JP-A Sho 63-26240 (JP, A) JP 8-294749 (JP, A) JP 7-276005 (JP, A) JP 3-42151 (JP, A) JP 1-138013 (JP , A) JP 61-219448 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/06 330 B22D 11/12 B22D 11/124 B22D 11/22

Claims (2)

(57) [Claims] 1. A method for winding a twin-drum type continuous cast slab, which comprises descaling a thin plate slab of carbon steel cooled to 400 to 700 ° C. and winding it on a coil. 2. A twin-drum type continuous cast slab, characterized in that a thin slab of carbon steel having a temperature of more than 700 ° C. is descaled, immediately cooled to 400 to 700 ° C. and wound into a coil. How to take.