JPH07204790A - Roll for continuously casting strip - Google Patents

Abstract

PURPOSE:To reduce the thermal crown and to obtain a strip having good shape by making a roll for continuous casting to the double sleeve structure making the inner layer sleeve to longer than the outer layer sleeve and making the part of the inner layer sleeve fitted by the outer layer sleeve to thick. CONSTITUTION:The roll for casting used to an apparatus for continuously casting a strip directly from molten steel is made to be the double sleeve structure. In this roll, the inner layer sleeve 2 covered with the outer layer sleeve 1 is supported with the flange 5 at the roll shaft core. The inner layer sleeve 2 is made to be longer than the outer layer sleeve 1 and the thickness of the part 21 contacting with the outer layer sleeve 1 is made to be thicker than the end part 22. It is desirable to use the material of the inner layer sleeve 2 having higher heat conductivity than the outer layer sleeve 1. By this constitution, the thermal crown can be reduced without making the roll structure complicate, and the strip product having good flatness is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll used in an apparatus for producing a thin plate of various steels such as carbon steel and alloys such as stainless steel directly from a molten metal by a continuous casting method.

[0002]

2. Description of the Related Art FIG. 4 is a view showing a method for directly producing a thin plate from molten metal (hereinafter, simply referred to as molten metal) by continuous casting, R is a roll, M is a molten metal, N is a casting nozzle, and D is a side dam. , S are thin cast pieces. FIG. 1A shows a method called a single roll method, in which the molten metal M is supplied from a casting nozzle N provided on the side surface of the roll to one continuously rotating roll R to cast a thin slab S. Is. Figure (b) and
(c) is a method called a twin roll method, in which the molten metal M is supplied between two rolls R, (b) the molten metal is supplied from above the roll, and (c) is the molten metal from the side of the roll. Supply
It is a casting.

Rolls used in these continuous casting methods often have a structure in which a copper or copper alloy sleeve is fitted to the shaft core and a refrigerant is passed between the shaft core and the sleeve in order to increase the amount of heat removal. However, when this is used for casting a thin slab, a phenomenon occurs in which the cooling ability is too large and the flatness and cracking of the thin plate occur.

In order to solve this problem, it has been attempted to use carbon steel or stainless steel, which has a lower thermal conductivity than that of copper alloy and cools the cast slab, as a sleeve material, but the cooling capacity is too small. As a result, the temperature of the roll becomes higher, and the thermal crown (a phenomenon in which the diameter of the central portion of the roll increases due to thermal expansion) increases.

When the thermal crown is increased by the twin roll method,
The cross-sectional shape of the slab at right angles to the casting direction may have a concave crown that becomes thinner in the widthwise central part, or the central part in the thickness direction of the end part may be unsolidified and pulled out, resulting in two cracks. . Since these defects are difficult to repair in the next process, they deteriorate the quality of the product.

In the case of the single roll method or the twin roll method of supplying the molten metal from the side of the roll, the casting nozzle for holding the molten metal is in contact with the long body of the roll. There will be a gap between and, and the molten metal will leak from it, making casting impossible.

Various methods have been proposed as methods for reducing the thermal crown.

FIG. 3 is a view showing the structure of a conventional two-layer sleeve, 1 is an outer layer sleeve, 2 is an inner layer sleeve, 3 is a roll shaft core, 4 is a core, and 5 is a flange provided on the shaft core. , 6 are cooling water passages, D is a side dam, and S is a slab.

For example, two layers (or multiple layers) as described above
In the sleeve structure, the inner layer sleeve 2 is made of a material having a coefficient of thermal expansion larger than that of the outer layer sleeve 3 (see Japanese Patent Application Laid-Open No. 3-133550), or the sleeve has a multi-layer structure, and the outer layer sleeve and the inner layer contacting the slab are formed. A roll has been proposed in which a step portion is provided between the sleeves and a predetermined portion of the outer layer sleeve is thin (see Japanese Patent Laid-Open No. 64-44252). Further, it has a negative (concave) roll crown, and by applying internal pressure to the central portion to deform the sleeve outward, a roll that keeps the sleeve flat (Japanese Patent Publication No.
62-27905 and JP-A-60-33857) have been proposed.

[0010]

The roll disclosed in Japanese Unexamined Patent Publication No. 3-133550 is effective when the inner layer sleeve and the outer layer sleeve have the same temperature, but actually contacts with a high temperature molten metal. The temperature of the outer layer sleeve becomes higher, and the amount of thermal expansion of the outer layer sleeve becomes larger than that of the inner layer sleeve. In particular, when carbon steel or stainless steel having a low thermal conductivity, which makes the cooling moderate, is used for the outer layer, the temperature of the outer layer becomes high, and the effect of reducing the thermal crown is not recognized so much.

The roll disclosed in JP-A-64-44252 has a thin sleeve thickness at the center of the roll width where the bending moment is large, and therefore has low strength (rigidity) and is easily bent. Therefore, the thermal crown is reduced to about half that of the conventional one, but the effect is small.

JP-B-62-27905 and JP-A-60-33
Although the roll disclosed in Japanese Patent No. 857 can correct a small thermal crown, the thermal crown becomes large when the outer layer is made of carbon steel, stainless steel, or the like, which cools the slab gently. A large internal pressure is required to correct the above, and the device becomes complicated.

An object of the present invention is to provide a thin casting continuous casting roll capable of significantly reducing the thermal crown even when carbon steel, stainless steel, or the like, which cools the slab gently, is used for the outer layer sleeve. To provide.

[0014]

The present inventors have confirmed that the cause of the thermal crown is the restraint of the shaft core flange portion and the temperature difference in the width and thickness directions of the sleeve. completed.

As shown in FIG. 1, the gist of the roll of the present invention is that "in a casting roll used in an apparatus for continuously producing thin plates directly from molten metal, the inner layer sleeve 2 covered with the outer layer sleeve 1 is a roll shaft. The inner layer sleeve 2 supported by the core flange 5 has a length longer than that of the outer layer sleeve 1, and the thickness of the portion 21 in contact with the outer layer sleeve is the end portion.
Continuous casting roll thicker than 22. "It is in.

The inner layer sleeve is preferably made of a material having a higher thermal conductivity than the outer layer sleeve.

[0017]

When the casting nozzle is installed in the roll body as in the single roll method, the body length of the casting roll is longer than or equal to the width of the slab, and the side dam is the same as in the twin roll method. The width is the same as the width of the slab when it is closely attached to the side surface of the roll.

In the roll structure as shown in FIG. 3, the outer layer sleeve becomes hot and thermally expands regardless of the width of the cast slab and the body length of the outer layer sleeve, but the inner surface of the inner layer sleeve is cooled and the temperature is low. Since it is fitted to the flange of the shaft core, expansion in the axial direction is restricted, and thermal expansion does not occur.
Further, at both ends of the outer layer sleeve, axial deformation of the flange of the roll shaft core is restrained via the inner layer sleeve. As a result, the diameter of the central portion of the outer layer sleeve is increased, and a thermal crown is generated.

This thermal crown becomes remarkable when carbon steel or stainless steel having a small thermal conductivity is used for the outer layer sleeve. In order to prevent this, the axial deformation of the outer layer sleeve is released from the restraint of the flange, and the trunk length of the inner layer sleeve is made longer than that of the outer layer sleeve as shown in FIG. Further, in order to suppress thermal deformation of the outer layer sleeve, the portion 21 where the inner layer sleeve contacts the outer layer sleeve is made thick. Also, the inner sleeve end
22 has a thin portion 23 that is not restrained by the flange,
We tried to ease the restraint of the flange.

It is desirable to select a material having a higher heat transfer coefficient than that of the outer layer sleeve so that the inner layer sleeve itself does not become thermally deformed due to high temperature.

As described above, in the double-sleeve structure roll, the inner layer sleeve is longer than the outer layer sleeve, and the wall thickness of the portion in which the outer layer sleeve is fitted is thicker, so that the roll has a thermal crown higher than that of the conventional roll. It was confirmed that it could be suppressed.

The structure and operation of the roll of the present invention will be specifically described with reference to the drawings.

1A and 1B are views showing an example of the structure of the roll of the present invention, wherein FIG. 1A is a longitudinal sectional view and FIG. 1B is a sectional view perpendicular to the axis. Reference numeral 1 is an outer layer sleeve, 2 is an inner layer sleeve, 3 is a roll shaft core, 4 is a core, 5 is a roll shaft core flange, 6 is a cooling water passage, D is a side dam, and S is a cast piece. The outer layer sleeve 1 is made of a material (alloy steel or stainless steel) having a heat conductivity of 8 to 60 W / (m · K) and excellent heat resistance for gently cooling the cast slab S.
Has a thermal conductivity of 300-400W /
A material (copper or copper alloy) having an excellent (m · K) cooling capacity is used.

The inner layer sleeve is thicker than the outer layer,
In addition, the thickness of the portion 21 in contact with the outer layer is made larger than that of the end portion 22 in contact with the flange 5 to increase the heat transfer and rigidity in the radial direction. This makes it possible to prevent thermal deformation.
Further, the length of the inner layer sleeve is made larger than that of the outer layer sleeve, and the portion 23 from the end portion of the outer layer to the inner side surface of the flange is made thin so that the restraint of the flange portion and the thermal crown are absorbed. As a result, the thinned portion 23 of the inner layer sleeve is deformed, but if casting is disabled,
It was confirmed that the cross-sectional shape of the cast piece was not adversely affected.

The roll of the present invention having such a structure can greatly reduce the thermal crown without complicating the structure. It is particularly effective when alloy steel or stainless steel, which has a low thermal conductivity and can cool the slab slowly, is used for the outer layer sleeve. A thin plate product with good properties is obtained,
With the single roll method, stable casting can be performed without the accident that the molten metal leaks.

FIG. 2 is a view showing another embodiment of the roll of the present invention, (a) is a view showing a state of applying the single roll method for casting, N is a casting nozzle, and (b) [Fig. 4] is a diagram showing a mode in which the thickness of a portion of the inner layer sleeve which is in contact with the outer layer is increased, and is a case where a thick portion is provided on the inner surface side of the inner layer sleeve.

[0027]

The effects of the present invention will be described in more detail with reference to the following examples.

The casting roll of the present invention has the shape shown in FIG.
It was made as follows.

The outer layer sleeve has an outer diameter of 600 mm and a length of 240 mm.
, With a wall thickness of 6 mm, Inconel 718 (trade name, 52% Ni, 1
9% Cr, 5% Nb, 3% Mo, 0.9% Ti, 0.5% Al, balance F
e, thermal conductivity 11.2 W / (m · K) (room temperature)) was used. The inner layer sleeve has an inner diameter of 468 mm, a length of 440 mm (the thickness of the thick part at the center of the width is 240 mm), the thickness of the thick part at the center of the width is 60 mm, and the thickness of the thin part at the end is 20 mm. 1.2%
Cr, 0.13% Zr, balance Cu, thermal conductivity 352 W / (mK) (
Room temperature)) was used. The roll shaft and core are made of carbon steel (JIS
SS41) was used.

In the comparative example, a casting roll having the shape shown in FIG. 3 was used. The outer layer sleeve has an outer diameter of 600 mm, a length of 240 mm, and a wall thickness of 6 mm. The inner layer sleeve has an inner diameter of 468 mm and a length of 240 m.
The thickness was 6 mm, the thickness was 6 mm, and other conditions were the same as those of the above-mentioned invention.

The casting test was carried out from an austenitic stainless steel (SUS304) 1520 ° C molten metal (about 2 tons) with a width of 240 mm and a thickness of
2.3 mm slabs were cast at a casting speed of 30 m / min. The flow velocity of the cooling water in the casting roll was 5.2 m / s (flow rate 0.04 m ³ / s).

(Example 1) The casting rolls of the present invention and the comparative rolls described above were applied to the twin roll method shown in FIG. 4 (b), and casting was performed at 10 charges for each, and the plate crown of the obtained thin cast piece was obtained. It was measured.

When the casting roll of the example of the present invention is used, FIG.
On the other hand, the average was 0.18 mm as shown in, whereas it was 0.59 mm when the casting roll of the comparative example was used.

FIG. 6 is a diagram showing the amount of deformation (calculation result) at the roll closest position during casting. The finite element is the deformation amount generated at the roll closest position during casting under the above casting conditions. It is the result of analysis by the method. From the figure, the deformation (crown amount) of the casting roll of the present invention was 0.11 mm, whereas the deformation amount of the conventional casting roll was 0.32 mm, which was confirmed to be almost similar to the test result. .

Example 2 The casting roll used in Example 1 was applied to the single roll method shown in FIG. 4 (a), a casting test was conducted, and the casting amount until the casting was interrupted by the heat crown was measured.

The casting roll of the present invention tested 18 charges and was able to fully cast 15 charges as shown in FIG. The three charges that interrupted casting were interrupted due to defective winding of the slab and lowering of the molten metal temperature, and were not due to roll deformation.

On the other hand, the conventional casting roll was tested for 9 charges, and succeeded in casting 2 charges as shown in the figure. However, at 7 charges, molten metal leak occurred between the casting roll and the casting nozzle, and Interrupted. This is due to the thermal deformation of the roll.

[0038]

EFFECTS OF THE INVENTION By using the casting roll of the present invention, it is possible to reduce roll deformation during casting, reduce the plate crown of the cast slab (the center of the plate width is depressed), and reduce the gap between the roll and the casting nozzle. It is possible to reduce leakage of molten metal from the inside. As a result, a thin plate product having a good plate shape can be stably manufactured.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of a casting roll of the present invention,
(a) is a sectional view parallel to the axis, and (b) is a sectional view perpendicular to the axis.

FIG. 2 is a view showing a cross section of another embodiment of the casting roll of the present invention, (a) is a view showing an embodiment when used in a single roll method, and (b) is a thick portion of an inner layer sleeve. It is a figure which shows the aspect at the time of providing in the inside of a sleeve.

FIG. 3 is a view showing a cross section of a conventional casting roll.

FIG. 4 is a diagram for explaining a mode for producing a thin cast product by a roll cooling method, in which (a) is a single roll method, and (b) and (c) are twin roll methods.

FIG. 5 is a view showing a crown amount of a thin cast piece by a twin roll method.

FIG. 6 is a diagram showing a roll deformation amount (calculation result) at a roll kiss point in the twin roll method.

FIG. 7 is a diagram showing a casting amount by a single roll method.

[Explanation of symbols]

1. Outer sleeve 2. Inner layer sleeve
3. Roll axis 4. Core 5. Shaft core flange
6. Cooling water passage D. Side Dam N.A. Casting nozzle
S. Slab R. Casting roll M. Molten metal 21. Thick part of inner layer sleeve 22. End of inner sleeve 23. Thin part of inner layer sleeve

Claims (2)

[Claims] 1. In a casting roll for use in an apparatus for continuously producing thin plates directly from molten metal, an inner layer sleeve covered with an outer layer sleeve is supported by a flange of a roll shaft core, and the inner layer sleeve has a long length. Is longer than the outer layer sleeve, and the thickness of the portion in contact with the outer layer sleeve is thicker than that of the end portion. 2. The roll for continuous casting of thin plates according to claim 1, wherein the inner layer sleeve is made of a material having a higher thermal conductivity than the outer layer sleeve.