JP3055591B2 - Cooling drum for twin-drum continuous casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling drum for a twin drum type continuous casting apparatus, and more particularly to a cooling drum peripheral surface shape.

[0002]

2. Description of the Related Art As an apparatus for manufacturing a thin metal plate, a molten metal is poured into a pool formed by a pair of cooling drums and a pair of side weirs pressed on both end surfaces of the cooling drum to form a thin cast slab. There is a twin-drum type continuous casting device that performs continuous casting. According to this apparatus, the rolling process and the equipment can be simplified since a hot rolling process in multiple stages is not required and the rolling for obtaining the final product shape can be light.

FIG. 1 shows an example of the twin drum type continuous casting apparatus. In this apparatus, a pair of cooling drums 1 and 1 rotating in opposite directions are arranged at appropriate intervals, and side dams 2 and 2 formed of refractory or the like on both end surfaces of the cooling drum (only the near side is indicated by a chain line). Is formed by pressure bonding to form the pool 3.

When molten metal is injected into the pool 3 by the pouring nozzle 4, the injected molten metal comes into contact with the cooling drums 1 and 1, and solidified shells 5 and 5 are formed on the surface of the cooling drum.

The solidified shells 5 and 5 are joined at the closest point of the drum and pressed down to form a thin cast piece 6 having a predetermined thickness, and the thin cast piece 6 is continuously fed out below the cooling drum.

One of the problems in the twin drum type continuous casting apparatus is to make the thickness of the thin cast slab uniform in the width direction. That is, the cooling drums 1 and 1 are heated by the retained heat of the injected molten metal, and the drum profile changes due to thermal expansion, so that the drum gap 9 becomes uneven in the axial direction of the cooling drum. When the solidified shells 5 and 5 are rolled down while the drum gap 9 is uneven, the rolling force applied to the solidified shells 5 and 5 becomes uneven,
The thickness of the cast thin-walled slab 6 becomes uneven in the width direction and causes defects such as cracks and wrinkles.

Therefore, in order to maintain the drum profile during casting in a predetermined shape, a method of forming the cooling drums 1 and 1 in a drum shape with a concave central portion so as to cancel thermal expansion is disclosed in Japanese Patent Application Laid-Open No. H10-163,873. It is disclosed in JP-A-61-037354.

[0008]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 61-0373
In the case of casting with a cooling drum having a drum-shaped profile according to the technique disclosed in Japanese Patent Publication No. 54-54, the growth of solidified shell at the end of the cooling drum is delayed, the thickness of the end of the thin cast slab is reduced, and the shape is reduced. In addition to the worsening, defects such as cracks and wrinkles caused by uneven solidification may occur, and further, breakout may occur.

The cause will be described. As shown in FIG. 2, when the solidified shell 5 is formed on the surface of the cooling drum 1 and grows, the solidified shell 5 contracts in the direction of the arrow S parallel to the axes 7 and 7 of the cooling drum 1 as the temperature decreases. I do. At this time, in the twin-drum continuous casting apparatus, the molten metal height H (FIG. 1) in the pool is low and the pressure of the molten metal acting to press the solidified shell 5 against the surface of the cooling drum 1 is small. As shown in the figure, the solidified shell 5 easily rises from the surface of the cooling drum 1 by solidification shrinkage in the direction of the arrow S at the end of the cooling drum 1.

Further, in the twin-drum continuous casting apparatus, since the molten metal M is rapidly cooled on the surface of the cooling drum 1, the contraction stress in the direction of arrow S is remarkable. Further, the strength of the solidified shell 5 is low because the thickness is small and the temperature is high. Due to these, the above-mentioned lifting is remarkably exhibited. Further, the lift increases in proportion to the width of the cooling drum 1, that is, the width of the slab.

When both ends of the solidified shell 5 are lifted off the cooling drum 1 in this manner, air gaps 8, 8 are formed between the cooling drum 1 and the solidified shell 5, and the air gaps 8, 8 increase the heat transfer resistance. And heat removal failure occurs,
The growth of the solidified shell 5 is delayed.

Since the thickness of the end portion of the slab decreases due to the delay in the growth of the solidified shell, a large amount of trimming is required to obtain a product having a uniform thickness in the width direction, which complicates the process and reduces the yield. Problems occur. In addition, the slab ends may break or break out,
Casting may stop.

An object of the present invention is to make the thickness and shape of a thin cast slab to be cast by a twin-drum continuous casting apparatus uniform over the slab width direction.

[0014]

According to the present invention, a pair of cooling drums arranged in parallel with each other , and a pair of side dams crimped on both end surfaces of the cooling drum are provided.
And a molten drum in a twin-drum continuous casting apparatus that continuously injects and solidifies a molten metal into the pool formed by the above process to continuously cast a thin-walled slab, and both ends of the cooling drum are shafts. It is characterized in that it has a cylindrical shape with a predetermined diameter over a predetermined length in the direction, and has a central portion formed in a drum shape with a minimum diameter at the center position of the drum width.

[0015]

As shown in FIG. 4, the solidified shell 5 formed on the surface of the cooling drum 1 shrinks in the direction of the arrow S parallel to the axes 7, 7 of the cooling drum 1 as the temperature decreases during growth.
Since both ends of the cooling drum 1 of the present invention are cylindrical over a predetermined length in the axial direction of the cooling drum, the solidified shell 5 only slides in a direction parallel to the axes 7, 7 of the cooling drum 1,
The tight contact between the surface of the cooling drum and the solidified shell 5 is maintained, and no air gap occurs between the solidified shell 5 and the cooling drum 1. Therefore, the heat removal is kept constant even at the end of the cooling drum, and the growth of the solidified shell 5 is not delayed.
The thickness of the solidified shell 5 becomes uniform in the width direction of the cooling drum,
A thin cast piece having a uniform thickness in the width direction can be obtained.

As described above, according to the present invention, it is possible to cast a thin cast piece having a good thickness and shape by improving the formation of the solidified shell at the end of the cooling drum.

[0017]

An embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 4, both ends a, a of the cooling drum 1
Is formed in a cylindrical shape having a radius A over a predetermined length in the axial direction, and the central portion b of the cooling drum 1 is formed in a drum shape such that the radius B at the center position of the drum width is minimized. That is, the radius B is smaller than the radius A, and the central portion b is formed in a drum shape that cancels the thermal expansion.

The dimensions of a, a, b, A, and B are determined in consideration of the steel type, width and thickness of the thin cast slab to be cast, the cooling structure and material of the cooling drum, and the like. . For example, when the diameter of the cooling drum is 1000 mm and the width is 1200 mm, the length a of the cylindrical portion is preferably 2 to 50 mm, and the difference between A and B, that is, the drum crown amount is preferably 30 μm to 500 μm. In this embodiment, a = 25 mm, b = 1150 mm, A
= 500 mm, B = 499.7 mm.

Next, the main casting conditions for continuous casting of thin cast slabs using the cooling drum of this embodiment will be described. The rotation speed of the cooling drum is 60 m / min, which represents the casting speed and 1 m / sec.
become. The molten steel used was stainless steel, and the thickness of the thin cast slab was 3 mm.

Next, the casting result and the shape of the obtained thin cast piece will be described. When casting was performed using the cooling drum described above, the central portion of the width of the cooling drum, that is, the drum-shaped portion, protruded due to thermal expansion, and became almost flat with a slight crown. The cylindrical portions at both ends of the cooling drum also receive heat, but the deformation due to thermal expansion was very small, so that the cylindrical shape in the cold state was almost maintained. As a result, the solidified shell does not rise at the end of the drum, and since the heat removal is kept good, it has a good surface property without cracks and wrinkles, and a thin slab with uniform material in the width direction. No trouble such as breakout at the end of the slab occurred, and stable casting was achieved.

Further, since the plate thickness is uniform in the slab width direction and there is no burr generation or chipping at the end, edge trimming for a post-process is unnecessary.

[0022]

As described above, according to the cooling drum of the twin-drum continuous casting apparatus of the present invention, heat can be prevented from being removed at the end of the cooling drum by a simple means of changing the peripheral surface shape of the end of the cooling drum. The uniformity of the solidified shell thickness can be eliminated by eliminating the uniformity, the end shape of the thin cast slab is improved, and it is possible to cast a thin cast slab whose thickness and material are uniform in the slab width direction. Become. As a result, casting troubles such as breakouts are prevented and casting is stabilized, and edge trimming is not required, so that steps can be omitted and the yield can be improved.

[Brief description of the drawings]

FIG. 1 shows a cross section perpendicular to a drum axis of a twin drum type continuous casting apparatus.

FIG. 2 shows the twin-drum continuous casting apparatus shown in FIG.
3 shows a cross section taken along line XX parallel to the drum axis.

FIG. 3 shows a cross section parallel to a drum axis of a twin drum type continuous casting apparatus.

FIG. 4 shows a cross section parallel to the drum axis of the twin-drum continuous casting apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cooling drum 2 ... Side weir 3 ... Hot water pool part 4 ... Pouring nozzle 5 ... Solidified shell 6 ... Thin cast piece 7 ... Cooling drum shaft 8 ... Air gap between cooling drum and solidified shell 9 ... Drum gap a ... width of both ends of the cooling drum b ... width of the center of the cooling drum A ... radius of both ends of the cooling drum B ... radius at the center of the width of the cooling drum S ... shrinkage direction of the solidified shell M ... molten metal

Continuing from the front page (72) Inventor Chihiro Yamaji 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Headquarters No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Keiichi Yamamoto 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory (56) References JP, A) JP-A-7-51809 (JP, A) JP-A-6-344084 (JP, A) JP-A-61-37354 (JP, A) JP-A-2-123343 (JP, U) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) B22D 11/06 330

Claims (1)

(57) [Claims] 1. A pair of cooling drums arranged in parallel with each other , and a pair of side crimped to both end surfaces of the cooling drum.
A cooling drum in a twin-drum continuous casting device for continuously injecting and solidifying molten metal into a pool formed by a weir to solidify and continuously cast thin-walled slabs,
A twin drum characterized in that both ends of the cooling drum are cylindrical with a predetermined diameter over a predetermined length in the axial direction, and a center portion is formed in a drum shape having a minimum diameter at a drum width center position. Cooling drum for continuous casting equipment.