JPH05200496A - Twin roll type thin plate continuous casting method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a casting method for twin-roll type thin plate continuous casting, which prevents the occurrence of molten metal leakage from both end portions of the slab and the occurrence of breakout. [Structure] The inner surface temperature of the side weir is Td that satisfies the following formula.
Casting is performed by preheating to the temperature range of. 0.41 (Tl-Ts) ≥ (Td-Ts) ≥ {-1.4 (T
l-Ts) -440} where Ts: solidus temperature (° C) of cast metal Tl: liquidus temperature (° C) of cast metal

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting thin plates in twin roll type continuous casting.

[0002]

2. Description of the Related Art FIGS. 2A and 2B are explanatory views of twin roll type thin plate continuous casting. FIG. 2A is a perspective view of a main part, FIG. 2B is a sectional view taken along the line E, and FIG. Two roll-shaped molds 3-1 and 3-2 arranged horizontally and in parallel with a gap corresponding to the thickness t of the slab to be manufactured are arranged in the directions of arrows 5-1 and 5-2. Rotate. Side weirs 4-1 and 4-2 are provided on both end surfaces of the roll-shaped molds 3-1 and 3-2, respectively.
-2 is pressed against it. The inner surface of the side weir is smooth, and the end surfaces of the roll-shaped molds 3-1 and 3-2 slide on the inner surface of the side weir to rotate.

For example, the molten metal in the tundish 1 is supplied as an injection flow 2 between the roll-shaped molds 3-1 and 3-2.
Since the insides of the roll-shaped molds 3-1 and 3-2 are water-cooled, the molten metal solidifies on the surface of the roll-shaped mold to form solidification shells 6-1 and 6-2 of FIG. 2B. The solidification shells 6-1 and 6-2 move following the rotation of the roll-shaped molds 3-1 and 3-2, and are integrated in the minimum gap between the roll-shaped molds 3-1 and 3-2. , And a cast piece 7 having a thickness of tmm is taken out.

During this time, solidification of the molten metal in contact with the surface of the side dam 4-1 and the surface of 4-2 also progresses. In FIG. 2 (C), if the side weirs 4-1 and 4-2 are cooled from the outside, for example, to strengthen the cooling of the molten steel, the side weirs have solid lines 11-1,
The thick solidified shell shown by 11-2 is formed, and the thickness 8-1 in the minimum gap portion 10 is also thick. In addition, the side weir 4-1
When 4-2 is heated from the outside, for example, to cool the molten steel, thin solidified shells shown by dotted lines 9-1 and 9-2 are formed on the side weirs, and the thickness 8-2 in the minimum gap portion 10 is also formed. thin.

In FIG. 2 (B), the solidified shell formed on the surface of the side dam is fan-shaped with the upper end width t ₁ and the lower end width t. That is, following the rotation of the roll-shaped molds 3-1 and 3-2, the width of the solidified shell on the surface of the side dams 4-1 and 4-2 is compressed from t ₁ to t. When the solidification shell formed on the surface of the side dam is excessively thick, it is difficult to compress it from t ₁ to t. Therefore, in this case, the roll-shaped mold 3-1 and
3-2 moves to the left and right and the minimum gap portion becomes larger than t, but if the minimum gap portion fluctuates and becomes wide, a casting accident (breakout) is caused. When the solidified shell formed on the surface of the side dam is excessively thin, the solidified shells 9-1 and 9-2 are ruptured by the compression whose width is changed from t ₁ to t, and the molten metal is squeezed from both ends of the slab 7. It leaks and causes a leak of molten metal.

[0006]

DISCLOSURE OF THE INVENTION The present invention prevents a breakout accident due to an excessively thick solidified shell on the surfaces of the side dams 4-1 and 4-2 during casting, and prevents the slab from being too thin. An object of the present invention is to provide a casting method of twin roll type thin plate continuous casting capable of preventing the occurrence of molten metal leakage at both ends.

[0007]

The present invention is a casting method characterized in that the inner surface temperature of the side dam is preheated to a temperature range of Td (° C.) satisfying the following formula and casting is performed.

0.41 (Tl-Ts) ≥ (Td-Ts) ≥ -1.4 (Tl-Ts) -440 where Ts = solidus temperature (° C) of cast metal Tl = liquid phase of cast metal Line temperature (℃)

[0009]

The present inventors used a twin roll type thin plate continuous casting machine comprising a water-cooled copper roll mold (diameter: 400 mm, length: 350 mm) and a BN side weir with a thickness of 20 mm. , Fe-Cu based alloy (Cu: 50% by weight, balance substantially Fe), austenitic stainless steel (SUS304), Fe-Si based alloy (Si: 3% by weight, balance substantially Fe), Fe-Ni System alloy (Ni: 8
Twin-roll type thin plate continuous casting was performed by changing the preheating temperature of the side weir with a molten metal of 0% by weight and the balance substantially Fe). The casting conditions and casting results are shown in Table 1. An SiC heating element installed inside was used for preheating the side weir.

In Table 1, Nos. 1 to 6 are examples of Fe-Cu based alloys. The solidus temperature Ts of the Fe—Cu alloy used as the component in this experiment is about 1080 ° C., and the liquidus temperature Tl is about 1440 ° C. Therefore, 0.41 (T1-T
s) is 148, and also {-1.4 (T1-Ts) -440}.
Is calculated to be -944. No. 1 is an example in which the preheating temperature Td of the side dam is 1260 ° C. and (Td−Ts) is + 180 ° C. In this case, (Td-Ts) was large, exceeding the upper limit of preheating of 148 ° C., so that melt leakage occurred 3 minutes after the start of casting. For numbers 2 to 5, (Td-Ts) is the upper limit of preheating (1
Since the side weir was preheated to a temperature between 48 ° C) and the lower limit of preheating (-944 ° C), casting could be performed without any trouble. In No. 6, (Td-Ts) was smaller than the lower limit of preheating of -944 ° C and was small, so that breakout occurred during casting.

[0011]

[Table 1]

In Table 1, Nos. 7 to 12 are examples of SUS304 series stainless steel, and 0.41 (Tl-Ts) is 21,
Also, {-1.4 (T1-Ts) -440} is calculated as -510. (Td-Ts) is within this range Number 8
No. 7 could be cast without any trouble, but No. 7 (Td-T
s) was +50, which was too high, exceeding the upper limit of preheating 21, and Nos. 11 and 12 were (Td-Ts) -640 and -720, respectively, which were too small and exceeded the lower limit of preheating -510. A leak or breakout occurred.

In Table 1, Nos. 13 to 18 are examples of Fe-Si alloys, 0.41 (Tl-Ts) is 12, {-1.4.
(T1-Ts) -440} is calculated as -482. Nos. 14, 15, and 16 could be cast without trouble because (Td-Ts) was preheated so as to be between the preheating upper limit and the preheating lower limit, but No. 13 (Td-Ts) exceeded the upper limit. The numbers 17 and 18 are (Td-T) because they are too large.
Since s) is smaller than the lower limit and is too small, molten metal leakage or breakout occurs.

In Table 1, Nos. 19 to 22 are examples of the Fe-Ni system. Also in this case, since No. 20 was preheated so that (Td-Ts) was between the preheating upper limit and the preheating lower limit, casting could be performed without problems, but No. 19 (Td-Ts) exceeded the preheating upper limit. Since too large and the numbers 21 and 22 are too small (Td-Ts) beyond the lower limit of preheating,
A casting accident has occurred.

FIG. 1 shows the numbers 1 to 22 in Table 1,
It is a figure showing (Td-Ts) and the occurrence situation of a casting accident.
As shown in FIG. 1, when the preheating temperature Td of the side weir is raised to (Td-Ts)> 0.41 (Tl-Ts), molten metal leakage occurs in the initial stage of casting. The reason for this seems to be that if the side weir is preheated excessively, the solidified shell formed on the surface of the side weir becomes thin at the initial stage of casting.

On the other hand, as shown in FIG. 1, the preheating temperature of the side weir is low, and (Td-Ts) <{-1.4 (T1-Ts).
In the case of -440}, a breakout accident is likely to occur. This breakout accident also often occurs in the early stages of casting. As the casting time elapses, the side weir is heated by the molten metal being cast and its temperature rises, so the frequency of breakouts due to the temperature of the side weir being too low decreases.

In FIG. 1, a molten metal having a large (Tl-Ts), such as an Fe-Cu based alloy, has a low preheating temperature Td, and therefore a breakout accident is unlikely to occur even when (Td-Ts) is small. The reason for this is that a molten metal having a large (Tl-Ts), such as an Fe-Cu alloy, has a structure in which the solidified shell formed on the surface of the side dam has a structure in which a liquid phase and a solid phase are mixed, and is bitten by twin rolls. It is thought that the size of the minimum gap of the twin rolls does not fluctuate significantly due to this deformation.

[0018]

By implementing the present invention, it is possible to prevent the occurrence of breakout accidents and molten metal leakage during continuous casting of twin roll type thin plates.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a relationship between (Td-Ts) and the occurrence situation of a casting accident, and FIG. 2 is an explanatory diagram of twin roll type continuous casting.

[Explanation of symbols]

1: Tundish, 2: Injection flow, 3 (3-1, 3
-2): Roll-shaped mold, 4 (4-1, 4-2): Side weir, 6 (6-1, 6-2): Solidification shell on the surface of roll-shaped mold, 7: Cast slab, 8 (8 -1,8-2): Thickness of solidified shell on the surface of the side weir, 9 (9-1,9-
2): Solidification shell on the surface of the side weir, 10: Minimum gap portion, 11 (11-1, 11-2): Solidification shell on the surface of the side weir, 12: Molten metal.

Claims (1)

[Claims] 1. A twin roll type thin plate, characterized in that, in twin roll type thin plate continuous casting, casting is performed by preheating the inner surface temperature of a side dam within a temperature range of Td (° C.) satisfying the following formula. Continuous casting method 0.41 (Tl-Ts) ≥ (Td-Ts) ≥ -1.4 (Tl-Ts) -440 where Ts: solidus temperature (° C) of cast metal Tl: liquidus line of cast metal Temperature (℃)