JPH1076352A - Continuous casting method of ni or fe-ni alloy shins sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and continuously cast a high quality of thin sheet for a long time by feeding a Ni or Fe-Ni alloy molten metal between upper and lower cooling rolls and casting at a specified speed while feeding an ambient atmosphere gas containing a He on the surface of the molten metal. SOLUTION: The Ni or Fe-Ni alloy molten metal 6 composed of, by wt., 0-65% Fe and substantially the balance Ni is fed from a tundish 8 provided with a nozzle 7 made from a refractory material into the gap between two upper and lower cooling rolls consisting of the upper roll 1 whose surface is metallic and the lower roll 2 whose surface is ceramic to continuously cast a Ni or Fe-Ni alloy thin sheet 5. In the twin-roll lateral pouring type continuous casting equipment, casting is executed at the casting speed of 20-50m/min while feeding the ambient atmosphere gas 9 containing, by vol., 30% He or more via a feeding means 11 to the molten metal surface in a contact starting point 10 between the molten metal 6 and the upper roll 1. By this way, the thin sheet 5, having a uniform structure in both upper and lower surfaces 5U, 5L, without defects such as wrinkles, wave-like ruggedness or the like and with an excellent surface property, is stably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting a thin plate directly from a molten Ni or Fe--Ni alloy by a twin-roll horizontal casting continuous casting apparatus.

[0002]

2. Description of the Related Art A continuous casting method using a twin roll has a merit that manufacturing costs can be reduced as compared with a conventional continuous casting method because a hot rolling step can be omitted. A method has been 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.
The roll arrangement includes an oblique upper pouring method in which the rolls are inclined with respect to the horizontal direction) and the twin roll horizontal pouring method in which two rolls are arranged in the vertical direction and hot water is supplied from the horizontal direction (the two rolls are arranged in the vertical direction) (Including the oblique horizontal pouring method).

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 high-temperature strength can be cast stably without cracking or breaking of the thin plate.

In the continuous sheet casting method using twin rolls,
Since the rolling ratio in the lower process after casting is smaller than that of the conventional method, high quality is required for the thickness variation and the surface properties. For this reason, high-quality thin plate manufacturing method and manufacturing equipment,
In particular, various studies have been made on the material and surface properties of the roll surface, which has an important effect on the quality of the thin plate. For example, the present inventors have proposed the following roll for continuous casting of a thin plate for obtaining a thin plate having excellent surface properties.

The surface of the roll disclosed in JP-A-8-150442 has a two-layer structure of a lower plating layer and a surface plating layer. The lower plating layer has a thickness of 10 to 50 μm.
The surface plating layer is made of Cr having a thickness of 5 to 30 μm, and has an average surface roughness of 3 to 15 μm. "Iron and Steel" (Vol.71, No.10, A245-248, 1985) shows a horizontal pouring method using different diameter twin rolls, using mild steel as the upper roll and stainless steel as the lower roll. .

As a method for improving the surface properties of a thin plate, the following twin-roll continuous casting method has been proposed.

The method disclosed in Japanese Patent Application Laid-Open No. 4-4954 is for producing a thin sheet of austenitic stainless steel with less wrinkles by properly combining the type of atmosphere gas, the molten steel component and the casting speed.

The method disclosed in Japanese Patent Laid-Open No. 4-187346 is
By supplying an atmosphere gas having an absorptive gas content of 60 vol% or more to the surface of the molten metal supplied between the rolls, a thin plate having excellent surface properties without cracks or irregularities is manufactured.

[0013]

SUMMARY OF THE INVENTION The present inventors have attempted to make use of Ni or Fe-N
For i-alloys (hereinafter referred to as alloys), research and development have been advanced on a method for improving the quality of thin sheets by this method. As a result, in the case of the alloy, even if the cooling roll as shown in the above-mentioned application is applied to the horizontal pouring method, the following problems 1) and 2) still remain, and the above-mentioned Japanese Patent Application Laid-Open No. 4-4954.
It has been found that even if the method disclosed in Japanese Patent Application Laid-Open No. 4-187346 or the method disclosed in Japanese Patent Application Laid-Open No. 4-187346 is applied to the lateral pouring method, there are the following problems 3) and 4).

1) Cooling conditions for two rolls, ie, N
Even if the conditions such as the contact time of i or Fe-Ni alloy molten metal (hereinafter, referred to as molten metal), roll shape, surface properties, and cooling water flow rate are the same, there is a difference in the growth rate of the solidified shell generated on each roll surface. .

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

3) A defect called a wrinkle occurs on the upper surface of a Ni or Fe—Ni alloy thin plate (hereinafter, referred to as a thin plate).

4) Wavy irregularities are formed on the upper surface side of the thin plate.

The present invention has been made to solve the above problems 1) to 4). An object of the present invention is to use a twin-roll horizontal pouring sheet continuous casting apparatus equipped with upper and lower rolls having specific surface conditions, to have a uniform structure on both upper and lower surfaces and to stably produce a thin sheet having a good surface texture for a long time. It is to provide a continuous casting method that can be manufactured.

[0019]

SUMMARY OF THE INVENTION The gist of the present invention is the following continuous casting method of a Ni or Fe-Ni alloy sheet.

Using a twin-roll horizontal casting continuous casting apparatus having two upper and lower cooling rolls, an upper roll having a metallic surface and a lower roll having a ceramic surface, Fe: 0 to 65 w
t%, the balance being substantially Ni or Fe-
The Ni alloy melt is supplied between the upper and lower rolls, and while supplying an atmosphere gas having a He content of 30 vol% or more to the surface of the Ni or Fe-Ni alloy melt in contact with the upper roll, 20 to 50 m / m A continuous casting method for a thin Ni or Fe-Ni alloy sheet, wherein the casting is performed at a casting speed of min.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the configuration of an apparatus for carrying out the method of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic side sectional view showing a twin-roll horizontal pouring thin plate continuous casting apparatus (roll of the same diameter, horizontal horizontal pouring) used in the method of the present invention. This apparatus comprises an upper roll 1, a lower roll 2, a refractory nozzle 7, a tundish 8
And atmosphere gas supply means 11 for supplying the atmosphere gas 9 to the surface of the molten metal 6 in contact with the upper roll 1, that is, the contact starting point 10 between the molten metal 6 and the upper roll 1.

In this case, the upper roll 1 and the lower roll 2 have the same diameter, are both horizontal in the axial direction, and vertically arranged in the vertical direction. The atmosphere gas 9 supplied to the surface (contact start point 10) of the molten metal 6 in contact with the upper roll 1
The entire surface of the melt 6 in the tundish 8 is also sealed,
The lower surface and the side surfaces of the molten metal 6 are sealed by a refractory nozzle 7 in contact with the lower roll 2.

The molten metal 6 in the tundish 8 slides on the lower roll 2 and is supplied between the rotating upper roll 1 and the lower roll 2 by a refractory nozzle 7 having a sealing function for the molten metal 6. , Cooled and pressed into a thin plate 5.

FIG. 2 is a schematic longitudinal sectional view in the lateral direction showing a twin-roll horizontal pouring thin plate continuous casting apparatus (different diameter roll, oblique horizontal pouring) used in the method of the present invention. 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.

In FIGS. 1 and 2, reference numeral 5U denotes the upper surface of the thin plate 5, and reference numeral 5L denotes the lower surface.

The apparatus used in the method of the present invention is a twin-roll horizontal casting continuous casting apparatus as described above, wherein the upper roll 1 has a metal surface 3 and the lower roll 2 has a ceramic surface 4. Equipped with

The method of the present invention is characterized in that the molten iron contains 0 to 65 wt% Fe and the balance is substantially Ni, ie, pure Ni or F
The molten metal 6 of the e-Ni alloy is supplied between the upper and lower rolls 1 and 2, and while the atmosphere gas 9 having a He content of 30 vol% or more is supplied to the surface of the molten metal 6 in contact with the upper roll 1, 20. Ni or Fe at a casting speed of ~ 50 m / min
-Cast the Ni alloy thin plate 5.

In the horizontal pouring method, it is most preferable that the upper roll 1 has a metal surface and the lower roll 2 has a ceramic surface, and these are used in combination, and the atmosphere gas and casting speed conditions are appropriately selected. By doing so, there is no difference in the roughness of the solidified structure between the upper and lower surfaces 5U and 5L, and it is possible to stably produce the thin plate 5 having excellent surface properties for a long time. The operation will be described below.

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

The surface material of each of the upper and lower rolls in the method of the present invention is based on the results of examining the solidification structure of a thin plate having the above composition obtained by applying rolls having various surface materials and comparing the roughness. It is. The dendrite primary arm spacing (μm) at a position 0.05 mm from the surface of the thin plate was used to evaluate the roughness of the solidified structure. These are shown in Table 1.
This will be described with reference to Table 3.

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

[0033]

[Table 1]

[0034]

[Table 2]

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

The necessary conditions for the material of the upper roll surface include good wettability with the molten metal, difficulty in pulling the atmosphere gas film into the molten metal together with the rotating roll, or high heat conductivity, and (Or coagulation shell) does not cause coagulation delay. Metals satisfying these conditions are as shown in Table 1.

In particular, in order to protect the roll base material under the surface layer in the upper roll, Ni plating having a thickness of 3 mm or less, or 5 to 30 μm in thickness to prevent scratches due to contact with a thin plate.
The surface hard plating of Cr may be applied. Further, in order to reduce the thermal stress at the plating layer boundary, 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 plating structure.

The necessary conditions for the material of the lower roll surface are that it has a lower thermal conductivity than the material of the upper roll surface, allows for slow cooling, and is less likely to wear even when sliding with a refractory nozzle. That is. Ceramics satisfying these conditions are as shown in Table 2.

As ceramics, ZrO ₂ ,
It is desirable to spray and spray a simple substance of ceramics such as Al ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , BN and Si ₃ N ₄ or a mixture thereof. The applied thickness of the sprayed layer is determined in the range of 50 to 500 μm so that cooling conditions equivalent to those of the solidified shell formed on the upper roll side can be obtained.

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

[0041]

[Table 3]

As shown in Table 3, the surface of the upper roll was coated with Ni plating (M1) having a thickness of 2 mm or Ni plating having a thickness of 2 mm.
The wear rate is 2 μm / hr or less even for the metal of (M2) in which hard plating is applied to the plating. On the other hand, the lower roll surface was sprayed with a ceramic spray (C1 or C1) having a thickness of 120 μm.
Only in the case of 2), the wear rate is 0.3 μm / hr. Therefore, in a combination in which the upper roll surface is made of metal and the lower roll surface is made of ceramic, the wear on the lower roll surface is reduced, and the wear speed on the roll surface is substantially uniform in the upper and lower directions.

The roll peripheral speed in the method of the present invention is determined by a horizontal pouring method using a pair of upper and lower rolls of the combination.
This is based on the results of continuously casting thin sheets at various roll peripheral speeds and comparing the surface properties of the obtained thin sheets. FIG. 3 shows the results.

FIG. 3 is a diagram showing the effect of casting speed on the occurrence of upper surface wrinkles of surface defects of a thin plate. As shown in FIG. 3, when the casting speed exceeds 50 m / min,
The generation of periodic wrinkles is observed on the upper surface side of the thin plate, and the tendency that wrinkles occur more frequently as the casting speed is higher. On the other hand, when the casting speed is 50 m / min or less, no wrinkles are generated. The cause and cycle of the wrinkle flaws are as described above. At a low casting speed of 50 m / min or less, the dynamic melt meniscus in contact with the upper roll is stable, and vibration of the melt surface does not occur. Can be prevented.

FIG. 4 is a diagram showing the effect of casting speed on the occurrence of a lower surface biting flaw of a surface defect of a Ni or Fe—Ni alloy thin plate.

As shown in FIG. 4, the casting speed is 20 m / m
When it is less than "in," a defect called a biting flaw often occurred on the lower surface side of the thin plate. The bite flaw is due to the low peripheral speed of the roll and the slow flow of molten steel in the refractory nozzle, so that a solidified shell is formed at the tip of the nozzle (triple boundary between the molten metal, the nozzle and the lower roll) in contact with the lower roll. It is a defect that is generated and adheres once to the nozzle, then is taken away from the nozzle into the thin plate, and does not occur at a predetermined casting speed of 20 m / min or more.

Therefore, the range of the casting speed capable of simultaneously preventing wrinkles on the upper surface side and biting defects on the lower surface side of the thin plate is 20 to 50 m / min.

In the method of the present invention, as the atmosphere gas supplied to the surface of the molten metal in contact with the upper roll, thin plates are continuously cast with various atmosphere gases by the horizontal pouring method using the above-mentioned combination of upper and lower rolls at the above casting speed. It is based on the result of comparing the nonuniformity of the thickness of the obtained thin plate in the casting direction. FIG. 5 shows the results.

FIG. 5 is a view showing the influence of the atmosphere gas on the nonuniformity of the thickness of the Ni or Fe—Ni alloy thin plate in the casting direction.

As shown in FIG. 5, when the He content in the atmosphere gas is less than 30 vol%, the nonuniformity of the plate thickness is 5%.
%. This is because wavy irregularities are generated on the upper surface side. On the other hand, when the He content is in the range of 30% or more, the nonuniformity of the plate thickness becomes 2% or less, and it can be seen that the wavy irregularities generated on the upper surface side of the thin plate can be prevented.

The cause of the occurrence of the wavy irregularities is as follows as described above. Even when there is no dynamic vibration of the molten metal surface, the atmospheric gas is constantly drawn into the molten metal with the rotation of the upper roll, and unevenly intervenes between the upper roll and the molten metal (or solidified shell) to cause thermal resistance. Causes uneven cooling. Due to the uneven cooling, the growth of the solidified shell on the upper surface side becomes uneven, and irregularities on the upper surface of the thin plate are wavy irregularities.

The cooling unevenness as described above is mitigated by using an atmosphere gas having high thermal conductivity.

In order to alleviate cooling unevenness due to gas interposed between the upper roll and the molten metal (or solidified shell), it is necessary that the thermal conductivity of the atmosphere gas be at least 0.060 W / mK or more.

The thermal conductivity of Ar and N ₂ , which are commonly used atmosphere gases, is 0.018 W / mK and 0.026 W / mK, respectively, while the thermal conductivity of He is 5 times that of Ar or N ₂ gas. 0.150 W / mK, which is twice or more. By using 100 vol% He as the atmosphere gas, the thermal resistance of the atmosphere gas is reduced, and the above-mentioned uneven cooling can be reduced.

The content of He in the atmosphere gas is 30 vol%
Even in the above range, the thermal conductivity of the atmosphere gas is substantially 0.060 W / mK or more, and the atmosphere gas interposed between the upper roll and the molten metal (or the solidified shell) does not have a large thermal resistance. In addition, wavy irregularities can be prevented.

The wavy irregularities on the upper surface of the thin plate are particularly likely to occur in alloys, and hardly occur in other steel types, for example, austenitic stainless steels represented by SUS304 steel. Although the details of this reason are not clear, the present inventors have measured the solidification shrinkage rate of various alloy types and found that the alloy has a larger solidification shrinkage rate than austenitic stainless steel represented by SUS304 steel. I understood. Therefore, in the alloy, the solidified shell formed on the upper roll surface is liable to be deformed, and a gas having an uneven thickness is interposed between the upper roll and the molten metal (or the solidified shell), causing cooling unevenness. It is presumed that irregularities occur.

The Ni or Fe—Ni alloy of the present invention
The reason for limiting the content as described above will be described.

Ni or Fe—Ni alloy is generally γ
High crack sensitivity due to single layer solidification. In addition, cracks are likely to occur due to dimensional changes due to expansion during the γ → α transformation in the cooling process. In particular, when the Fe content exceeds 65 Wt%, α ·
The γ transformation point is as high as 450 ° C. or more, and the expansion amount during transformation is also large. Therefore, since a slight crack in temperature (during the cooling process) occurs in the thin plate immediately after casting, a surface crack occurs, so the Fe content was limited to 0 to 65 Wt%.

Next, other desirable conditions will be described.

The material of the base material of each of the upper and lower rolls does not matter,
It is desirable to use a copper alloy for effective internal cooling by cooling water.

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-described ceramic sprayed material, its thermal conductivity is 2 W / mK or less. Therefore, the upper roll surface material 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 roll is 3 to 15 μm, and the range of the surface roughness Ra of the lower roll is 1.5 to 6.0 μm. Is desirable.

A desirable range of the casting speed is 25 to 40 m
/ Min. In this range, the effect of preventing generation of wrinkles on the upper surface side and biting defects on the lower surface side of the thin plate can be more reliably obtained, and continuous casting can be performed more stably for a longer time.

The desirable range of the He content of the atmosphere gas in the method of the present invention is 50 vol% or more and 100 vol% or more.
It is as follows. In this range, the effect of uniform cooling on the upper and lower surfaces of the thin plate can be obtained more reliably.

The gas species other than He constituting the atmosphere gas is not limited. However, in order to prevent a reaction such as oxidation between the molten metal and the atmosphere gas and obtain a thin plate having a better surface, the atmosphere gas is He and H. It is desirable to use a mixed gas with ₂ or Ar which is an inert gas.

A desirable range of the dimensions of the thin plate is a thickness of 1.2
The width is about 3.5 mm and the width is about 200 to 1300 mm.

The method of the present invention can be applied to any one of rolls irrespective of diagonal horizontal pouring, horizontal horizontal pouring, and irrespective of whether the diameters of the rolls are the same or different, that is, irrespective of the supply direction of the molten metal and the orientation relationship of the twin rolls and the roll diameter. The present invention can be applied to a twin roll continuous casting method in which the contact start position of the molten metal has a free surface in contact with the atmosphere gas, and the contact start position of the molten metal on the other roll slides with the refractory nozzle.

[0068]

【Example】

(Test 1) Using a twin-roll horizontal pouring continuous casting apparatus shown in FIG. 2, a 65 wt% F having a thickness of 1.7 mm and a width of 250 mm was used.
An Fe-Ni alloy thin plate containing e and substantially the remainder Ni was cast, and the shape of the thin plate, the presence or absence of surface defects, the uniformity of the solidified structure on the upper and lower surfaces, the damage on the roll peripheral surface, and the like were investigated.

As the upper roll, a copper alloy sleeve having a thickness of 20 mm was used as a base material, a Ni plating of 2 mm thickness was applied, and a roughened surface having a surface roughness Ra: 10 μm was formed by shot blasting. Using.

The lower roll is made of a copper alloy sleeve having a thickness of 20 mm as a base material, and a 50 μm thick Ni
Subjected to Ni-Cr sprayed plating and thickness 50 [mu] m, after further applying a thickness 120 [mu] m ZrO ₂ spraying -8wt% Y ₂ O _3, the surface roughness Ra by buffing: used was adjusted to 3μm .

The upper roll has a diameter of 500 mm and a body length of 25.
0mm, lower roll diameter 600mm, body length 400m
m, and the inside of each of the upper and lower rolls was water-cooled.

The temperature of the molten metal in the tundish is 50 ° C.
And the casting speed was 25 m / min.

On the surface of the molten metal in contact with the upper roll,
Using a mixed gas of 1% He and 50 vol% N ₂ ,
It was supplied at a flow rate of liter / min. The bottom and sides of the molten metal were sealed with a refractory (fused silica) nozzle sliding on the lower roll peripheral surface. The cast thin plate was excellent in plate shape with no corrugated irregularities, and had substantially uniform solidification structures on the upper and lower surfaces and no surface defects such as cracks and wrinkles, and was sound. In addition, stable casting was possible without damage to the roll peripheral surface or seizure of the thin plate.

(Test 2) Using a twin-roll horizontal casting continuous casting apparatus shown in FIG.
Fe-containing 5 wt%, the balance being substantially Ni-Fe-
Cast a Ni alloy thin plate, the shape of the thin plate, the presence or absence of surface defects,
The uniformity of the solidification structure on the upper and lower surfaces and the wear rate of the roll peripheral surface were investigated.

The upper roll is made of a 20 mm thick copper alloy sleeve coated with Ni plating of 2 mm thickness as a base material, and is subjected to a roughening process with a surface roughness Ra: 6 μm by shot blasting. 30 μm Ni-W and 10 μ thickness
Each of which had been subjected to each hard plating of m Cr was used.

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

The upper roll has a diameter of 600 mm and a body length of 25.
0mm, lower roll diameter 600mm, body length 400m
m, and the inside of each of the upper and lower rolls was water-cooled.

The temperature of the molten metal in the tundish is 30 ° C.
And the casting speed was 40 m / min.

On the surface of the molten metal in contact with the upper roll, 100 V
ol% of He gas was supplied at a flow rate of 10 liter / min. The bottom and sides of the molten metal were sealed with a refractory (fused silica) nozzle sliding on the lower roll peripheral surface.

The cast thin plate was healthy in shape and surface quality in the same manner as the inventive example of Test 1, and the solidified structures on the upper and lower surfaces were almost uniform. Stable casting was possible without damage to the roll peripheral surface or seizure of the slab.

Further, a test was carried out in which the Ni content in the molten metal, the combination of the surface materials of the upper and lower rolls, the casting speed and the atmosphere gas were variously changed, and the wear state of the roll surface and the presence / absence and shape of the sheet surface defect were determined. investigated. Table 4 shows the conditions of the upper and lower rolls, the atmosphere gas, and the casting speed, and the results of examination of the surface properties of the thin plate.

[0082]

[Table 4]

As shown in Table 4, when a combination of a metal upper roll and a ceramic lower roll is used, the casting speed range is 20 to 50 m / min, and He in the atmosphere gas is used. In the examples of the present invention in which the range of the content was 30 vol% or more, the cast thin plate was sound in both shape and surface properties. On the other hand, as shown in the comparative examples in Table 4, under the conditions outside the range of the method of the present invention, cracks on the surface of the thin plate, wrinkles on the upper surface side, or wavy irregularities occurred.

(Test 3) Using a twin-roll horizontal pouring continuous casting apparatus shown in FIG. 2, 0.2 Wt% of Fe and 99.5 Wt% of Ni were contained in a thickness of 1.6 mm × width of 250 mm, and the balance was as follows. A thin sheet of pure Ni composed of unavoidable impurities was cast, and the shape of the sheet, the presence or absence of surface defects, the uniformity of the solidified structure on the upper and lower surfaces, the damage on the roll peripheral surface, and the like were investigated.

The upper roll is formed by subjecting a copper alloy sleeve having a thickness of 20 mm to a base metal, applying a Ni plating of a thickness of 2 mm, and then performing a roughening process with a surface roughness Ra: 10 μm by shot blasting. Was used.

The lower roll is made of a copper alloy sleeve having a thickness of 20 mm as a base material.
After plating and 50-μm-thick Ni—Cr thermal spraying, and then 120 μm-thick Al ₂ O ₃ -25 Wt% ZrO ₃ thermal spraying, the surface roughness Ra is 4 μm by buffing.
m was used.

The upper roll has a diameter of 500 mm and a body length of 25.
0mm, lower roll diameter 600mm, body length 400m
m, and the inside of each of the upper and lower rolls was water-cooled.

The temperature of the molten Ni in the tundish is 5
The temperature was adjusted to 0 ° C., and the casting speed was 30 m / min.

On the surface of the Ni molten metal in contact with the upper roll, 70
Using a mixed gas of Vol% the He and 30 vol% N _2, it was fed at a flow rate 15 liters of / min. Refractory (fused silica) that slides on the lower roll peripheral surface at the lower part and side part of the Ni molten metal
It was sealed for the nozzle made.

The cast pure Ni thin plate is excellent in plate shape without wavy irregularities, and has substantially uniform solidification structures on the upper and lower surfaces.
In addition, there were no surface defects such as cracks and wrinkles, and the samples were sound. In addition, stable casting was possible without damage to the roll peripheral surface or seizure of the thin plate.

[0091]

According to the method of the present invention, the effect of equalizing the cooling rate of the upper and lower rolls, the effect of stabilizing the surface of the molten metal in contact with the upper roll, and the uniform cooling between the upper roll and the molten metal (or solidified shell) are uniform. By this effect, it is possible to prevent the occurrence of minute cracks and a difference in gloss on the upper and lower surfaces of the thin plate, wrinkles on the upper surface side, and wavy irregularities on the upper surface side, thereby enabling continuous casting of the thin plate having good surface properties and shape.

By using a lower roll having a ceramic surface, wear of the lower roll surface can be prevented, and the above effect can be maintained for a long time.

[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.

FIG. 3 is a view showing the effect of casting speed on the occurrence of upper surface wrinkles of surface defects of a Ni or Fe—Ni alloy thin plate.

FIG. 4 is a diagram showing the influence of casting speed on the occurrence of lower surface biting flaws of surface defects of Ni or Fe—Ni alloy thin plates.

FIG. 5 is a view showing the influence of an atmospheric gas on the irregularities on the upper surface side of a Ni or Fe—Ni alloy thin plate.

[Explanation of symbols]

 1: Upper roll, 2: Lower roll, 3: Upper roll surface, 4: Lower roll surface, 5: Ni or Fe-Ni alloy thin plate, 5U: Upper surface of thin plate 5, 5L: Lower surface of thin plate 5, 6: Ni or 7: Refractory nozzle, 8: Tundish, 9: Atmospheric gas, 10: Starting point of contact between Ni or molten alloy and upper roll, 11: Atmospheric gas supply means.

Claims (1)

[Claims] 1. A twin-roll horizontal casting continuous casting apparatus having two upper and lower cooling rolls, an upper roll having a metallic surface and a lower roll having a ceramic surface, Fe: 0 to 65 w
t%, the balance being substantially Ni or Fe-
The molten Ni alloy is supplied between the upper and lower rolls, and an atmosphere gas having a He content of 30 vol% or more is supplied to the surface of the molten Ni or Fe-Ni alloy in contact with the upper roll, while supplying 20 to 50 m / m. A continuous casting method for a thin Ni or Fe-Ni alloy sheet, wherein the casting is performed at a casting speed of min.