JPH09164454A - Continuous casting equipment of sheet metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a sheet metal with excellent surface property and uniform structure on each side, and to prevent the wear of a lower roll by providing an upper roll with metallic surface, and the lower roll with ceramics surface. SOLUTION: An upper roll 1 is provided with a metallic surface 3, and a lower roller 2 is provided with a ceramics surface 4, the upper roller 1 and the lower roller 2 are same in diameter, and horizontal in the axial direction, and are arranged longitudinal in the vertical direction. The molten metal 6 in a tundish 8 is fed between the rotating cooling upper roll 1 and lower roll 2 by a refractory nozzle 7 having the sealing function of the molten metal 6 in a slidable manner with the lower roll 2, cooled and pressed into a sheet metal 5. Because the cooling speed and the solidifying speed of the upper and lower rolls are uniform, generation of small cracks and the difference in the gloss between the upper and lower surfaces of the sheet metal can be prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a molten metal (hereinafter,
The present invention relates to a twin plate continuous casting apparatus for directly casting thin plates from molten metal or molten metal).

[0002]

2. Description of the Related Art Since a thin plate continuous casting method using twin rolls can omit a hot rolling step, it has an advantage that the manufacturing cost can be reduced as compared with the conventional continuous casting method. Proposed.

The twin roll method is a twin roll top pouring method (2 rolls) in which two rolls are arranged laterally and hot water is supplied from above the rolls, depending on the arrangement of the two rolls and the direction of hot water supply between the rolls.
And the twin-roll side-pouring method in which two rolls are arranged in the vertical direction and hot water is supplied from the horizontal direction (two-roll arrangement is in the vertical direction). Including diagonal slanting lateral pouring method) etc.

The horizontal pouring method has the following features.

[0005] Since hot water is supplied in the horizontal direction from the nozzle connected to the tundish, the level of the hot water in the tundish can be easily controlled, and a wide and uniform hot water can be supplied. Further, the operation is easy because the molten metal head is small.

[0006] The height of the equipment is low.

Since the transport of the thin plate is in the horizontal direction, the load stress due to the weight of the thin plate is small. Therefore, a material having low strength at high temperature can be stably cast without cracking or breaking of the thin plate.

Further, in the thin plate continuous casting method using a roll, since the rolling rate in the lower step after casting is smaller than that in the conventional method, a high quality is required for the variation of the plate thickness and the surface quality. For this reason, various materials, surface shapes, and the like have been studied for a manufacturing method and a manufacturing apparatus for a high-quality thin plate, especially for a roll surface that has an important influence on the quality of the thin plate. For example, the present inventors have applied for the following thin plate continuous casting roll for obtaining a thin plate having excellent surface properties.

The roll of Japanese Patent Application No. 6-293111 has a two-layer structure of a lower plating layer and a surface plating layer, the lower plating layer is a Ni-based alloy having a thickness of 10 to 50 μm, and the surface plating layer has a thickness of 5. The average roughness of the plating layer surface is 3 to 15 μm.

The roll of Japanese Patent Application No. 7-82463 is formed by forming a thermal spray coating of heat-resistant metal, cermet or ceramics having a surface roughness of 1 μm or more on the surface of the roll sliding on the refractory nozzle. .

"Iron and Steel" (Vol.71, No.10, A245-248, 198)
In (5), the horizontal pouring method using different diameter twin rolls, in which Mildsteel is used as the upper roll and Stainless steel is used as the lower roll, is shown.

[0012]

The present inventors have conducted research and development on a method for improving the quality of thin plates by this method in order to utilize the features of the twin roll lateral pouring method. As a result, it has been found that even if the cooling roll as shown in the above application is applied to the horizontal pouring method, the following problems (1) and (2) still occur.

(1) Even if the cooling conditions of the two rolls, that is, the conditions such as the molten metal contact time, roll shape, surface texture, and cooling water flow rate, are the same, the growth rate of the solidified shell formed on each roll surface is It makes a difference.

(2) The lower roll is more worn than the upper roll.

According to the research conducted by the present inventors, the problem (1) is caused by the asymmetry of the upper and lower rolls, in particular, the difference in the starting point of contact between the molten metal and the rolls on the upper and lower roll surfaces. .

That is, on the upper roll side, since the starting point of contact between the molten metal and the roll is the point of contact between the molten metal meniscus and the roll, the atmospheric gas is present at the contact starting point.
Therefore, the atmosphere gas film corresponding to the velocity boundary layer of the roll surface is drawn into the molten metal together with the rotating roll,
The gas film becomes a thermal resistance between the roll and the molten metal (or the solidified shell), which delays the growth of the solidified shell.

On the other hand, on the lower roll side, since the contact starting point is sealed by the refractory nozzle, no atmospheric gas is present and no gas film thermal resistance occurs. Therefore, the growth rate of the solidified shell is higher than that on the upper roll side.

The problems due to the difference in the growth rate of the solidified shell as described above are as follows.

The difference in the growth rate of the solidified shells on the upper and lower surfaces of the thin plate is caused by the different cooling rates during solidification.
This is accompanied by not only the difference in the thickness of the solidified shell on the upper and lower surfaces but also the difference in the roughness of the solidified structure and the crystal grain size on the upper and lower surfaces. The difference in crystal grain size between the upper and lower surfaces of the thin plate causes a difference in luster on the surface of the cold rolled product, which significantly impairs the surface quality of the thin plate.

When the cooling conditions on the upper and lower surfaces are greatly different, the temperature gradient inside the thin plate becomes asymmetric with respect to the center of the plate thickness,
There is also a risk of causing defects such as cracks due to the difference in solidification shrinkage between the upper and lower surfaces and the difference in heat shrinkage.

The difference in the solidification cooling behavior between the upper and lower roll surfaces in the horizontal pouring method is due to the cooling roll of the above-mentioned Japanese Patent Application No. 6-293111 having a two-layer plating structure and the spray coating on the surface. This is a phenomenon that can occur regardless of the surface material and surface roughness of the cooling roll of Japanese Patent Application No. 7-82463, as long as the upper and lower rolls have the same surface condition.

The wear of (2) is a phenomenon that occurs because the lower roll slides on the refractory nozzle.

The problems caused by the wear of the lower roll are as follows.

The above-mentioned Japanese Patent Application No.
When the effect of improving the surface quality of a thin plate by giving a specific surface roughness to the roll surface, like the cooling roll of 6-293111 or the cooling roll of Japanese Patent Application No. 7-82463 which has a thermal spray coating on the surface However, the effect cannot be maintained for a long time due to the abrasion of the roll surface. This is also the case with the metal rolls shown in the "Iron and Steel" report.

Further, in the twin roll method, since the surface quality of the thin plate largely depends on the surface condition of the roll, it is necessary to replace the roll regularly. If the deterioration of the lower roll is more severe than that of the upper roll, the cycle for exchanging only the lower roll is shortened, which is not only inefficient, but also the productivity is reduced and the cost is increased.

As described above, in the twin roll horizontal pouring method, due to the asymmetry of the upper and lower rolls, as long as the surface materials of the upper and lower rolls are the same, the difference in solidification rate and the difference in wear rate between the upper and lower rolls are large. Occurs.

The present invention has been made to solve the above problems. An object of the present invention is to provide a twin roll lateral pouring thin plate continuous casting device capable of producing a thin plate having a good surface quality and a uniform structure on both sides, and preventing wear of a lower roll to realize stable casting. Especially.

[0028]

DISCLOSURE OF THE INVENTION The gist of the present invention is the following thin plate continuous casting apparatus.

Two upper and lower cooling rolls are arranged in a vertical vertical direction or an oblique vertical direction so that the axes of the rolls are horizontal and the heights of the axes are different, and a thin plate is directly cast from the molten metal supplied between the rolls. A twin roll horizontal pouring continuous casting device, characterized in that it has an upper roll of metallic surface and a lower roll of ceramic surface.

The present inventors paid attention to the asymmetry of the upper and lower rolls in the horizontal pouring method and found the optimum surface condition for each roll. That is, by finding the optimum roll for each of the upper roll where the molten metal meniscus with the atmosphere gas is the starting point of molten metal contact and the lower roll having the molten metal contact starting point sealed by the sliding refractory nozzle, Succeeded in obtaining high quality thin plates stably for a long time.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION A configuration example of a device of the present invention will be described with reference to FIGS.

FIG. 1 shows a twin roll horizontal pouring method (rolls of the same diameter,
It is a schematic longitudinal cross-sectional view in a side direction showing a thin plate continuous casting apparatus using horizontal horizontal pouring). This apparatus includes an upper roll 1, a lower roll 2, a refractory nozzle 7 and a tundish 8. In this case, the upper roll 1 and the lower roll 2 have the same diameter, both are horizontal in the axial direction, and their vertical arrangement is in the vertical vertical direction. The molten metal 6 in the tundish 8 is supplied between the rotating cooling upper roll 1 and the rotating lower roll 2 by a refractory nozzle 7 that also slides on the lower roll 2 and also has a sealing function of the molten metal 6. And pressed to form the thin plate 5.

FIG. 2 shows a twin roll side pouring method (different diameter rolls,
FIG. 3 is a schematic vertical cross-sectional view in a side direction showing a thin plate continuous casting apparatus using diagonal horizontal pouring. The configuration of this apparatus and the manufacturing process of the thin plate 5 are the same as those in FIG. 1, but in this case, the diameter of the upper roll 1 is different from the diameter of the lower roll 2. These arrangement directions are inclined obliquely in the vertical direction with respect to the vertical direction as shown in the figure.

The apparatus of the present invention is a twin roll horizontal pouring continuous casting apparatus as described above, in which the upper roll 1 has a metallic surface 3 and the lower roll 2 has a ceramic surface 4 surface. It is a device.

1 and 2, reference numeral 5U is the upper surface of the thin plate 5, 5L is the lower surface of the thin plate 5, 9 is the atmospheric gas, and 10 is the meniscus of the molten metal 6 (the starting point of contact between the molten metal 6 and the upper roll 1). is there.

In the horizontal pouring method, it is most preferable that the upper roll has a metal surface and the lower roll has a ceramic surface. By using these rolls in combination, the roughness of the solidified structure on the upper and lower surfaces of the thin plate can be obtained. It is possible to stably produce a thin plate having excellent surface properties for a long time without any difference.
The operation will be described below.

In order to uniformly solidify the upper and lower surfaces without causing a difference in the texture such as the thickness of the solidified shell and the roughness of the solidified structure on the upper and lower surfaces of the thin plate, the asymmetry of the horizontal pouring method was dealt with. It is important to select the solidification cooling conditions.

The surface material of each of the upper and lower rolls in the present invention is S obtained by applying rolls having various surface materials.
It is based on the result of investigating the solidification structure of a US304 stainless steel thin plate and comparing the solidification constant and the roughness of the solidification structure. This will be described with reference to Tables 1 to 3.

The solidification constant k is a relational expression between the solidification time t (s) and the thickness d (mm) of columnar crystals grown from the roll surface: d
= K × (t / 60) ^0.5 . To evaluate the roughness of the solidified structure, dendrite 2 at 0.3 mm from the thin plate surface
The next arm spacing (μm) was used.

Table 1 shows the desirable metallic material on the surface of the upper roll and the comparative material, the conditions thereof and the roughness of the solidified structure on the upper surface of the thin plate obtained in that case. Table 2 shows desirable ceramics and comparative materials on the surface of the lower roll, the conditions thereof and the roughness of the solidified structure on the lower surface of the thin plate obtained in that case.

[0041]

[Table 1]

[0042]

[Table 2]

As shown in Tables 1 and 2, a combination of upper and lower rolls in which the surface material of the upper roll is metal plating and the surface material of the lower roll is ceramic sprayed, a uniform solidified structure can be obtained on the upper and lower surfaces of the thin plate. I understand.

The necessary conditions for the material of the surface of the upper roll are that it wets well with the molten metal and that the atmospheric gas film is difficult to be drawn into the molten metal together with the rotating roll, or that the thermal conductivity is high and the gas film is melted. Even if it is interposed between the molten metal and the molten metal (or the solidified shell), it does not cause the solidification delay. Metals satisfying these conditions are as shown in Table 1.

Particularly, in the upper roll, the thickness of Ni plating is 3 mm or less to protect the roll base material under the surface layer, or the thickness is 5 to 30 μm to prevent flaws caused by contact with a thin plate.
The surface hard plating of Cr of m may be applied. Further, in order to relax the thermal stress at the boundary portion of the plating layer, an intermediate layer plating of a Ni-based alloy having a thickness of 10 to 50 μm is further provided between the roll base material or the lower layer plating on the roll base material and the surface hard plating. It is desirable to have a multi-layered plated structure.

The necessary conditions for the material of the surface of the lower roll are that the material has a lower thermal conductivity than the material of the surface of the upper roll and that it can be cooled slowly, and that it does not easily wear when it slides on the refractory nozzle. That is. Ceramics satisfying these conditions are as shown in Table 2.

As the ceramic material, in particular, ZrO ₂ , Al
A ceramic simple substance such as ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , BN and Si ₃ N ₄ or a mixture thereof is preferably sprayed. The coating thickness of the sprayed layer is 5 so that cooling conditions equivalent to those of the solidified shell generated on the upper roll side can be obtained.
It is determined in the range of 0 to 500 μm.

Table 3 shows the wear of each roll obtained from the change in roll diameter (average value of both ends and center of the surface portion corresponding to the casting width of the thin plate) before and after use under the conditions shown in Tables 1 and 2. Indicates speed.

[0049]

[Table 3]

As shown in Table 3, in the combination of the upper roll surface made of metal and the lower roll surface made of ceramics, the wear of the lower roll surface is reduced, so that the wear rate of the roll surface is almost equal in the vertical direction. .

Next, other desirable conditions will be described.

The diameters and body lengths of the upper and lower rolls and the material of the base material are not limited, but the base material is preferably a copper alloy for effective internal cooling with cooling water or the like.

The ratio of the thermal conductivity of the upper roll surface material to the thermal conductivity of the lower roll surface material is preferably 5 or more. When the lower roll surface material is the above-mentioned sprayed ceramics, its thermal conductivity is 2 W / mK or less,
The surface material of the upper roll is preferably a metal plating material having a thermal conductivity of 10 W / mK or more.

In order to prevent defects such as cracks on the surface of the thin plate, the range of the surface roughness Ra of the upper and lower rolls is 3 to 1 respectively.
It is desirable that the thickness is 5 μm and 1.5 to 6.0 μm.

The apparatus according to the present invention is further equipped with an oblique side pouring, a horizontal side pouring, and two rolls regardless of different diameters or the same diameter.
Regardless of the arrangement of rolls and the dimensions of the rolls, one roll has a free surface where the molten metal contact start position contacts the atmospheric gas, and the other roll has the molten metal contact start position that slides on the refractory nozzle. It can be applied to all moving twin roll thin plate continuous casting processes.

The effect of using the apparatus of the present invention is the same when the target material is stainless steel, carbon steel, high alloy or non-ferrous metal.

[0057]

【Example】

(Example 1) Using a twin roll horizontal pouring continuous casting device having the configuration shown in FIG. 2, a SUS having a thickness of 1.7 mm and a width of 250 mm
304 stainless steel was manufactured at a casting speed of 50 m / min, and surface cracks, uniformity of solidified structures on the upper and lower surfaces, damage to the roll peripheral surface, and the like were investigated.

For the upper roll, a sleeve made of a copper alloy having a thickness of 20 mm was used as a base material, plated with Ni having a thickness of 2 mm, and then roughened by shot blasting to have a surface roughness Ra of 10 μm. Using.

For the lower roll, a copper alloy sleeve having a thickness of 20 mm was used as a base material, and as a base treatment, Ni having a thickness of 50 μm was used.
After plating and spraying Ni-Cr with a thickness of 50 μm, and further applying a sprayed layer of 92 wt% ZrO ₂ -8 wt% Y ₂ O ₃ with a thickness of 120 μm, the surface roughness Ra was adjusted to 3 μm by buff polishing. Was used.

The upper roll has a diameter of 500 mm and a body length of 2
50 mm, the size of the lower roll is 600 mm in diameter, and the body length is 40
The cooling of the upper and lower rolls was 0 mm, and both were water-cooled inside.
For the refractory nozzle, fused silica was used to seal the bottom and sides of the melt.

The cast thin plate was sound, had no microcracks, and had substantially the same solidification structure on the upper and lower surfaces. Stable casting was possible without damage to the roll peripheral surface or seizure of thin plates.

(Embodiment 2) As an example of the present invention, a twin roll horizontal pouring continuous casting apparatus having the structure shown in FIG.
SUS304 stainless steel with a width of 5 mm and a width of 250 mm was manufactured at a casting speed of 50 m / min, and surface cracks, uniformity of solidified structures on the upper and lower surfaces, damage to the roll peripheral surface, and the like were investigated.

For the upper roll, a copper alloy sleeve having a thickness of 20 mm and plated with Ni having a thickness of 2 mm was used as a base material. After roughening the surface roughness Ra: 6 μm by shot blasting, the thickness was further increased. 30 μm Ni-W, thickness 10
The thing which applied each hard plating of Cr (micrometer) was used.

For the lower roll, a copper alloy sleeve having a thickness of 20 mm was used as a base material, and as a base treatment, Ni having a thickness of 50 μm was used.
After plating and spraying Ni-Cr with a thickness of 50 μm, and further applying a sprayed layer of 75 wt% Al ₂ O ₃ -25 wt% ZrO ₂ with a thickness of 120 μm, the surface roughness Ra was adjusted to 4 μm by buff polishing. Was used.

The upper roll has a diameter of 600 mm and a body length of 2
50 mm, the size of the lower roll is 600 mm in diameter, and the body length is 40
The cooling of the upper and lower rolls was 0 mm, and both were water-cooled inside.
For the refractory nozzle, fused silica was used to seal the bottom and sides of the melt.

The cast thin plate was sound as in Example 1,
The roughness of the solidified structure on the upper and lower surfaces was almost uniform, and there was no difference in gloss between the upper and lower surfaces of the pickled thin plate. Stable casting was possible without damage to the roll peripheral surface or seizure of thin plates.

Further, tests were conducted in which the surface materials of the upper and lower rolls were variously changed under the same conditions as shown in Tables 1 and 2, and the above-mentioned solidification constant, roughness of solidified structure, surface properties of thin plate and wear rate of roll surface were measured. investigated. The roll conditions and results are shown in Table 4.

[0068]

[Table 4]

As shown in Table 4, the solidification constant, the roughness of the solidified structure, and the wear rate of the roll surface had the same tendency as the results shown in Tables 1 to 3 above.

That is, when the upper roll surface material is a metal material with Ni plating or further surface plating, and the lower roll surface material is ZrO ₂ --Y ₂ O ₃ or Al.
_In the thin plate obtained by using a ceramic material coated with a sprayed layer of ₂ O ₃ -ZrO ₂ , the solidification constants of the upper and lower surfaces and the roughness of the solidified structure were almost the same, and surface defects such as microcracks were also observed. There wasn't. However, in other combinations, for example, a thin plate obtained by using rolls having the same surface material on the upper and lower sides, the solidification constant on the upper surface side (see Table 1) is smaller than that on the lower surface side (see Table 2), and The solidified structure was coarse, and some thin plates had surface defects such as microcracks due to the difference in shrinkage between the upper and lower surfaces.

The wear rate of the roll surface obtained from the change in roll diameter was particularly remarkable when a metal material was used as the material of the lower roll surface, and was 3 to several tens of μm / hr.

However, as the material of the lower roll surface, ZrO ₂ --Y ₂
The wear rate when the ceramic material coated with the thermal sprayed layer of O ₃ or Al ₂ O ₃ —ZrO ₂ was suppressed to 0.3 μm / hr or less. Further, when a metal material applied with Ni plating or further surface plating is used as the surface material of the upper roll,
And ZrO ₂ −Y ₂ O ₃ or Al ₂ O ₃ as the lower roll surface material.
-When ceramics coated with a ZrO ₂ sprayed layer are used, the wear rates of the upper and lower rolls are almost the same, and the roughness of the solidified structure on the upper and lower surfaces is even and the thin plate with excellent surface properties is stable for a long time. Was able to be cast.

(Embodiment 3) Using a twin roll horizontal pouring continuous casting apparatus having the structure shown in FIG. 1, a thickness of 1.4 mm and a width of 250
mm, 60wt% Fe-40wt% Ni alloy thin plate casting speed 5
It was manufactured at 0 m / min and the surface properties were investigated. Other conditions were the same as those of the present invention example of Example 2.

The cast thin plates are those of Example 1 and Example 2.
As in Example 1 of the present invention, there were no microcracks, and it was possible to manufacture a thin plate having excellent surface properties.

[0075]

According to the apparatus of the present invention, due to the effect of equalizing the cooling rate and the solidification rate of the upper and lower rolls, fine cracks and gloss difference due to nonuniformity of the solidification structure on the upper and lower surfaces of the thin plate are prevented, and the surface texture is improved. A good thin plate can be continuously cast.

By providing the lower roll having a ceramic surface, abrasion of the surface can be prevented and the above effect can be maintained for a long time, and the operation and quality are stabilized.

[Brief description of the drawings]

[Fig. 1] Twin roll horizontal pouring method (same diameter roll, horizontal horizontal pouring)
It is an outline longitudinal section in the side direction showing an example of the thin sheet continuous casting device of the present invention using the above.

[Figure 2] Twin roll horizontal pouring (different diameter roll, oblique horizontal pouring)
It is an outline longitudinal section in the side direction showing an example of the thin sheet continuous casting device of the present invention using the above.

[Explanation of symbols]

1: Upper roll, 2: Lower roll, 3: Upper roll surface, 4: Lower roll surface, 5: Thin plate, 5U: Thin plate upper surface, 5L: Thin plate lower surface, 6: Molten metal, 7: Refractory nozzle, 8: Tan Dish, 9: Atmosphere gas, 10: Meniscus of molten metal (starting point of contact between molten metal and upper roll)

Claims (1)

[Claims] 1. A thin plate directly from the molten metal supplied between the rolls, wherein two cooling rolls are arranged vertically and vertically so that the roll axes are horizontal and the heights of the axes are different. A twin-roll horizontal casting continuous casting apparatus, characterized in that the twin-roll horizontal casting continuous casting apparatus is provided with a metallic upper roll and a ceramic lower roll.