JPH02165849A - Cooling roll for reducing twin roll type rapidly cooled strip - Google Patents

Abstract

PURPOSE:To stably produce a strip having good quality without any defect by forming grooves having the specific size on Ni plating layer applied on circumferential face of a cooling roll, using the cooling roll applying Cr plating layer further on this layer an rapidly cooling and solidifying molten metal. CONSTITUTION:By using one pair of the cooling rolls, the strip having <=1mm thickness is directly produced by rapidly cooling and solidifying from the molten metal. In the above twin roll type rapidly cooled strip producing apparatus, the cooling roll is constituted of a roll shaft 2 and roll barrel 1. The Ni plating layer 6 is applied on circumferential face of copper sleeve 5 in this roll barrel 1 and the grooves 4 having 0.05-0.20mm width W, 0.05-0.15mm depth D and 0.05-2.0mm pitch P thereof, are formed on this. Further, the surface of this Ni plating layer 6 is coated with the Cr plating layer 7. By this method, the rapidly cooled strip having good quality without any surface defect and internal defect is obtd. and also generation of roll crack, breakout and entwining to the cooling roll are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a cooling roll suitable for use in a process of directly producing a ribbon from molten metal using twin rolls.

(Prior art) A well-known method for directly manufacturing metal ribbon from molten metal is to cause the molten metal to flow down from a nozzle onto the circumferential surface of a cooling roll that rotates at high speed and rapidly solidify on the circumferential surface. . Methods using this cooling roll include the single roll method and the twin roll method. For example, when manufacturing wide thin sheets with a thickness of 1 mm or less such as amorphous alloy ribbon, high silicon steel ribbon, and stainless steel ribbon, The twin roll method is considered to be advantageous in terms of the surface properties and shape of the plate, and its industrialization is progressing.

In the production of quenched ribbon using the single-roll or twin-roll process, various casting defects (hereinafter referred to as surface defects) occur on the surface of the manufactured ribbon, which is one of the obstacles to industrialization. There is.

For example, there is a thermally poor contact area between the molten metal and the cooling roll, and solidification in this area is slower than solidification in the surrounding area, so the poor contact area becomes a linear or dot-like surface defect.
In some cases, it becomes an irregular mosaic pattern of depressions, so-called dimples.

Regarding avoiding these surface defects, JP-A-63-
50mm062 proposes a method of producing a crystalline metal piece having a thickness of 10 mm or less using a cooling roll having grooves parallel to the circumference on the circumferential surface of the roll in a single roll method. Although this method is effective in preventing surface defects in the ribbon in the single roll method, the following problems remain when applied to the twin roll method.

That is, casting defects generally exist in the width direction and longitudinal direction of the ribbon in the twin roll method, and moreover, they tend to be concentrated in one location. The reason for this is that since the molten metal is solidified and rolled by two cooling rolls, the flow of the molten metal in the width direction and longitudinal direction and the deformation of the solidified layer are greater than in the single roll method. For this reason, grooves parallel to the roll circumference are effective in restraining in the width direction, but cannot prevent casting defects in the longitudinal direction.

In addition, Japanese Patent Application Laid-Open No. 63-215340 discloses that in a single roll method, a cooling roll having lattice grooves is used to
A method for producing a metal ribbon of less than mm is described.

Although this method is effective in preventing surface defects in the ribbon in the single-roll method, problems remain when applied to the twin-roll method for producing ribbons with a thickness of 1 mm or less.

In other words, when this grooved roll is applied to the twin roll method,
Internal defects such as shrinkage cavities occur in the center of the width of the thin strip that has been created,
Moreover, cracks occur at the portions that come into contact with the edges of the grooves due to solidification and shrinkage within the roll grooves.

Furthermore, a common problem with this type of roll is that the roll surface wears and deforms after a long period of casting, making it impossible to maintain the groove in its proper shape. Since the behito cycle is extremely short and cracks are likely to occur on the roll surface due to thermal fatigue, forming grooves on the roll surface may further shorten the roll life.

On the other hand, in the field of continuous casting, there are disclosures regarding means for solving these problems. For example, JP-A-55-15
No. 6642, No. 61-92756, No. 61-1292
57 and 61. -180649 and other publications describe extending the life of mold grooves.

However, when these methods are applied to the rolls of the twin roll method, grooves of the appropriate shape cannot be obtained, and the effect of the grooved rolls,
That is, uniform coagulation within the grooves and prevention of roll cranking are not achieved, and it is difficult to mass-produce ribbons without surface defects.

(Problems to be Solved by the Invention) Therefore, the present invention addresses the surface defects of the ribbon, that is, dimples caused by delayed solidification, the flow of molten metal in the width direction of the roll, or the occurrence of molten metal wrinkles due to rolling, as well as internal defects such as shrinkage cavities. It is an object of the present invention to provide a cooling roll which is advantageous in avoiding defects and producing a cold ribbon of good quality without roll cracks, breakouts and windings on the cooling roll.

(Means for Solving the Problems) The present invention provides a pair of cooling rolls used for directly producing a thin strip with a thickness of 1 mm or less from molten metal by rapid solidification, which comprises a Ni plating layer applied to the circumferential surface. , Width: 0.05~0,
20mm, depth: 0.05 to 0.15mm and pitch: 0.05 to 2.0mm grooves are formed, and the surface of the nickel plating layer is further covered with a chromium plating layer.A twin roll type quenched ribbon. This is a cooling roll for manufacturing.

Here, the term "groove" refers to something that extends obliquely, perpendicularly, or horizontally to the axis of the roll, and its shape may be a polygonal groove such as a lattice groove, a triangular groove, a hexagonal groove, or a circular groove. .

Further, in order to promote uniform solidification within the grooves, it is desirable that the groove pitches be equal.

(Function) Conventionally, the surface of the cooling roll has been polished with sandpaper equivalent to No. 400 to give a surface roughness of about 0.3 μm Ra. However, when molten metal such as aluminum, copper, silicon steel or stainless steel is rolled and solidified on smooth rolls, surface defects are likely to occur. These defects are visible to the naked eye on the surface of the thin plate as dots, lines, or mosaic-like dimples or cracks depending on the situation.

By providing grooves on the circumferential surface of the cooling roll according to the present invention, molten metal enters into the grooves at the initial stage of solidification.
The coagulated layer formed on the roll surface is restrained by the grooves.

This suppresses the flow of molten metal in the width direction and length direction, the deformation of the solidified layer, etc. Phenomena such as poor thermal contact between the molten metal and the cooling roll and shrinkage of the solidified layer due to a decrease in temperature are unlikely to occur (and even if they occur, they will not be concentrated in one location).

Therefore, casting defects on the surface of the ribbon after manufacture can be avoided.

On the other hand, as disclosed by the inventors in Japanese Patent Application Laid-Open No. 58-205655, in the production of thin plates with a thickness of 1 mm or less, it is desirable to use the kissing point solidification complete type shown in FIG. 4(a). . On the other hand, in the production of thin plates with a thickness of 1 mm or more, it is known that the rolling type solidification form shown in FIG. 4(b) is used. A board like this invention? I-1 mm or less, that is, the kissing point solidification completion type, not only the above-mentioned surface defects, but also thermal shrinkage of the solidified layer, especially non-uniform deformation of the solidified layer on the side opposite to the roll surface (free surface), occur when casting is completed. This causes a void or an unsolidified layer in the center of the cross-section of the thin plate. In order to prevent these peculiar phenomena in the production of 7-yt plates with a thickness of 1 mm or less, simply adding grooves to the roll surface is not effective, and it is necessary to carefully consider and select the groove pitch, depth, and width.

Furthermore, it is important that the grooves be formed in the nickel plating layer applied to the circumferential surface of the roll, and that the grooves be further covered with a chromium plating layer. In other words, in order to avoid solidification delay in the grooves and solidification shrinkage in the grooves, it is effective to carve grooves in the plating layer and realize uniform slow cooling. This is because the growth of the solidified layer restrained by the grooves is different between the grooves and between the grooves, with the solidified layer growing larger in the areas between the grooves that contact the roll surface (there is an air gap within the grooves and the thermal conductivity is low).

By forming grooves in the nickel plating layer, nickel plating has a lower thermal conductivity than the base copper alloy, so it reduces the variation in the growth of the solidified layer within the grooves and between the grooves, and allows uniform slow cooling. It can be achieved.

Furthermore, when the surface is plated with chromium, chromium oxide is formed on the surface, which impairs wettability with molten steel, resulting in more uniform slow cooling.

Note that if the base material copper alloy roll is grooved and then coated with nickel and chromium plating, the predetermined dimensional accuracy cannot be obtained, so it is important to groove the nickel plating layer.

Furthermore, by providing these plating layers, it is possible to suppress the occurrence of cracks and deformation on the roll surface, and the roll shape including the grooves can be maintained with high precision.

That is, the underlying nickel plating has greater hardness and elongation than the base copper alloy. Therefore, when casting for a long period of time, which is the object of the present invention, ordinary copper alloy rolls suffer from thermal fatigue due to intense heat cycles, which can be prevented by coating with a glazing layer that causes cranking and deformation.

Furthermore, chromium plating can prevent seizure and wrapping at the interface between the cooling roll and the solidified layer.

The groove here is width: 0.05~0, 20mm, depth:
0.05-0.15mm and pitch: 0.05-2
．． It is important to satisfy 0 mm.

That is, the groove has a width of less than 0.05 mm and a depth of 0.05 mm.
If the thickness is less than 0.05 mm, the surface tension of the molten metal overcomes the static iron pressure and the molten metal does not fill the groove, making it impossible to form solidification nuclei, and the uniformity of solidification is impaired, making it difficult to form solidification nuclei compared to the case of fabrication using conventional flantro rolls. Similarly, surface defects and nests and defects within the cross section occur due to uneven solidification. This phenomenon is remarkable in the case of a kiss point solidification complete type with a plate thickness of lllIn+ or less. Furthermore, if the pitch exceeds 2.0 mm, the area of the smooth portion on the roll circumferential surface increases and uneven solidification occurs between the grooves, making it impossible to obtain uniform solidification throughout.6 On the other hand, when the width is 0.21 and the depth exceeds 0.15mm,
When the pitch is less than 0.05 mm, the molten metal is deeply filled into the grooves, causing the surface of the thin plate to seize after solidification. If the plate wraps around each of the plates, breakout or wrapping will occur, and prolonged casting can lead to cranking.

Furthermore, if you apply nickel plating after forming the grooves, the precision of the grooves will deteriorate (and the plating layer will peel off due to thermal stress within the grooves, so it is important to form the grooves on the nickel plating layer. Also, since a nickel plating layer alone causes a problem of sticking to the roll, chromium plating is applied on top of the nickel plating layer.The thickness of the nickel plating layer is 0 to prevent thermal fatigue due to severe heat cycles.
．． It is preferable to set it as the range of 2-0.61, and similarly, the thickness of chrome plating is 0.61. O1 to 0.05 mm.

(Example) A preferred example of the cooling roll according to the present invention is shown in FIG.

In the figure, 1 is a roll body made of copper or copper alloy with good thermal conductivity, 2 is a roll shaft, and grooves 4 extending in a direction perpendicular to the axis 3 and parallel to each other are arranged on the circumferential surface of the roll body 1. figure(
As shown in b), a nickel plating layer 6 is formed on the circumferential surface of the sleeve 50, and a chromium plating layer 6 is further applied on top of the nickel plating layer 6.
7 is coated.

As shown in FIG. 4B, the groove 4 has a V-shaped cross section in this example, and its radius W, depth D, and pitch P are set within the above-mentioned ranges.

Further, the groove 4 is not limited to the shape shown in FIG. 1, but may have the shape shown in FIGS. 2(a) to 2(f), for example.

The groove processing method is low left processing, mainly NC.
Machining such as lathe and slotter processing, photo etching, electrical discharge machining, laser processing, etc. are preferred. It is also recommended to clean the inside of the groove with a brush wiper.

Next, we will specifically describe the manufacturing process performed by applying various cooling rolls to the twin-roll type quenched ribbon manufacturing apparatus shown in FIG. 3. In FIG. 3, reference numeral 8 indicates a supply nozzle for the molten metal 9, and reference numeral 10 indicates a ribbon.

Various cooling rolls with the specifications shown in Table 1 were applied to the equipment shown in Figure 3, and Inconel 60G (Ni near 61m
mtχ+ Cr: 15wtχ, Mn: 0.8wtX,
Square cold ribbons with a width of 500+u+ and a thickness of 0.5 mm were manufactured from molten metal of Si: 0.5 wt$, Fenia wtX), and the surface properties of the obtained ribbons were examined.

The results are also listed in Table 1. The manufacturing conditions are: roll circumferential speed: 3n/s, reduction blade: 3L, and tapping temperature. 1
The temperature was 600°C.

From the same table, no surface defects were observed in the ribbons manufactured using the cooling rolls according to the present invention with Nα1 to 6, and on the other hand, even with the cooling rolls (Nα7 to 17) having grooves on the roll circumferential surface, the present invention If the compliance conditions were not met, surface defects were observed on the ribbon, seizure of the ribbon, breakouts, or roll cranks occurred, making it impossible to continue operation.

(Effects of the Invention) When the cooling roll of the present invention is applied to the production of twin-roll quenched ribbon, it is possible to produce a ribbon without surface and internal defects without causing ribbon wrapping, breakout, or roll cranking. It is possible to realize continuous and large-scale production of high-strength ribbons using the quenching effect.

[Brief explanation of the drawing]

Figure 1(a) is a front view of the cooling roll, Figure 1(b) is a cross-sectional view of the surface layer of the cooling roll, Figures 2(a) to (f) are schematic diagrams showing the shape of the grooves, and Figure 3 is a double-sided diagram. FIG. 4 is a schematic diagram showing a roll-type quenched ribbon manufacturing apparatus. FIG. 4 is a diagram showing a twin-roll solidification mode.

Claims (1)

[Scope of Claims] 1. A pair of cooling rolls used for directly manufacturing a ribbon with a thickness of 1 mm or less from molten metal by rapid solidification, comprising a Ni plating layer applied to the circumferential surface having a width of 0. .05-0.20
mm, depth: 0.05-0.15mm and pitch: 0
．． A twin-roll type cooling roll for manufacturing a quenched ribbon formed with grooves of 0.05 to 2.0 mm and further comprising a nickel plating layer and a chromium plating layer covering the surface of the nickel plating layer.