JPH08150442A - Roll for continuously casting metallic strip - Google Patents

Abstract

PURPOSE: To provide a cooling roll for stable continuous casting by preventing the deterioration such as crack and, burning of the metallic strip. CONSTITUTION: The roll for continuous casting the strip, having 3-15μm the average surface roughness Ra on the roll surface is used. The roll surface has double structure of the plating lower layer and a plating surface layer, and the plating lower layer is made of Ni base alloy having 10-50μm thickness and the plating surface layer is made of Cr having 5-30μm thickness and the average surface roughness Ra of the plating surface layer is 3-15μm. The generation of meandering of the strip caused by the uneven solidification and fine recessed parts on the strip surface caused by the thermal deformation of the solidified shell are prevented and also, the deterioration such as softening, crack and burning on the roll surface during operation is prevented by hardened plating of the surface layer part and therefore, the strip having good surface characteristic can stably and continuously be cast.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling roll used when continuously casting a thin metal sheet directly from a molten metal.

[0002]

2. Description of the Related Art In a continuous casting method for a thin metal plate such as a twin roll method or a single roll method, the hot rolling step can be omitted, so that the manufacturing cost can be reduced as compared with the conventional continuous casting method. There is. However, in the thin plate slab,
Compared with conventional slabs produced by continuous casting, the rolling rate in the lower step after casting is small, so high quality is required for variations in plate thickness and surface properties. Therefore, various manufacturing methods and manufacturing apparatuses for high-quality thin plate slabs have been studied.

For example, in JP-A-60-184449, a drum-type continuous casting using a cooling drum in which unevenness having a depth of 4 μm or more is evenly distributed on the surface in order to make the solidified shell thickness uniform in the width direction of the thin plate. Machine is shown.

Japanese Unexamined Patent Publication (Kokai) No. 62-254953 discloses a twin roll using a cooling roll having a surface with unevenness of 10 to 200 μm in order to manufacture a strip without dents, casting lines and fine cracks. A roll caster is shown.

Japanese Unexamined Patent Publication (Kokai) No. 64-83340 discloses a method for producing a thin cast piece which is free from cracks and fluctuations in wall thickness.
Shown is a cooling drum with circular or oval openings of diameter 0.1-1.2 mm, with pits of depth 5-100 μm evenly distributed on the surface without touching each other.

Japanese Patent Laid-Open No. 2-160145 has a two-layer plating layer of a base and a surface on the peripheral surface of a roll cylinder made of copper or copper alloy in order to obtain a quenched ribbon having excellent surface properties. A chill roll is shown. For this roll, the thickness is 0.1-0.
The base plating layer having a thickness of 4 mm is made of Ni, Ni-W alloy or Ni-W-Fe alloy, and the surface plating layer having a thickness of 0.01 to 0.03 mm is Cr.

The inventors of the present invention have disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-154616 a cooling roll for continuous casting which uses a sleeve made of a material having low thermal conductivity and excellent high temperature strength for the purpose of slow cooling of a thin plate.

[0008]

The cooling drum or cooling roll as described above still has the following problems.

Defects due to surface irregularities of metal thin plates and cracks due to irregularities Deterioration of cooling roll surface The forms of surface irregularities and surface cracks that occur during casting of the above metal thin plates are classified into the following A to C.

A: Large unevenness with uneven solidification thickness and large vertical cracks.

B: 10 to 50 mm with uneven solidification thickness
The undulations at intervals have undulations of about 50 to 100 μm and are accompanied by vertical cracks and microcracks.

C: Solidification thickness is almost uniform, but 2 to 5
Minute recesses with a depth of 20 to 30 μm in mm pitch are formed in a hexagonal shape and are accompanied by minute cracks.

According to the research conducted by the present inventors, the morphology of these defects changes depending on the cooling conditions on the roll side. The stronger the cooling from the roll, the greater the thermal stress on the surface of the solidified shell, and the deformation of the solidified shell begins to occur in the early stages of solidification, resulting in uneven cooling between the roll and the solidified shell, resulting in non-uniform solidification. It is promoted, and the depth and interval of the unevenness are increased.

When the cooling from the roll is alleviated, the thermal stress on the surface of the solidified shell becomes small and the start of deformation of the solidified shell is delayed, so that the uneven solidification is suppressed and both the depth and the interval of the unevenness are reduced. Get smaller. That is, when casting is performed with a cooling roll having a smooth surface, in the initial stage of solidification, the roll and the solidification shell are in close contact with each other, resulting in strong cooling and nonuniformity of solidification. Unevenness and vertical cracks occur. This form A defect is eliminated by performing a moderate cooling to a certain extent so that the interval between the unevenness of the thin plate surface due to the non-uniform solidification becomes narrower.
Waviness with vertical cracks and micro cracks occurs. The defect of form B can be eliminated by further cooling slowly so that the solidified thickness becomes almost uniform.

The above-mentioned prior art (JP-A-60-184449,
Japanese Unexamined Patent Publication (Kokai) No. 62-254953) discloses that unevenness or dents are distributed on the surface of a cooling roll to partially generate thermal resistance using an air gap as a medium.
The method of Japanese Patent No. 16 is to perform gentle cooling by using a roll of a material having a low thermal conductivity and excellent in high temperature strength, and to prevent defects of the forms A and B by these methods. Is possible.

However, in these prior arts, the form C is used.
Sufficient effect cannot be obtained to prevent the hexagonal pit defect associated with micro cracking. Form C turtle-shaped dents have a depth of 20-3
At 0 μm, there is almost no problem in terms of shape and appearance, but the quality of the product is remarkably impaired due to minute cracks locally generated in a part of the recessed part, so prevention thereof is an important issue.

The problems caused by the deterioration of the surface of the cooling roll are as follows.

In order to stably and continuously cast a metal thin plate having a good surface quality, it is important to maintain a predetermined cooling roll surface state, but the above-mentioned conventional measures for roll surface deterioration are still insufficient. is there. For example, in the embodiment of JP-A-64-83340, Ni is not formed on the sleeve surface.
A plating layer is formed and a dent is formed on the surface, but since the Ni plating layer is soft, the dent on the roll surface disappears due to contact with the thin metal plate during operation, and the effect is not only lost. However, the roll surface may be scratched in the circumferential direction, and the surface quality of the thin metal plate may be impaired.

The double-layer plating cooling roll disclosed in JP-A-2-160145 can prevent roll surface deterioration and improve steel strip surface properties when casting a high silicon thin steel strip.
In the case of casting a stainless steel plate having a thickness of more than 1 mm, the cooling from the roll is strong cooling, so that the form A is used.
Or a defect of B occurs.

The object of the present invention is to prevent the occurrence of Form C defects on the surface of a thin metal plate and the deterioration of the softening, cracking, and seizure of the cooling roll surface during operation, and to realize stable continuous casting. It is to provide a cooling roll.

[0021]

The present invention provides the following (1),
The gist is the roll for continuous casting of thin metal plate in (2).

(1) A cooling roll used when solidifying a molten metal on the peripheral surface of a roll to continuously cast a thin metal plate, characterized in that the roll surface has an average surface roughness Ra of 3 to 15 μm. Roll for continuous casting of thin plate slabs.

(2) The cooling roll of (1) above, wherein the roll surface has a two-layer structure of a lower plating layer and a surface plating layer, the lower plating layer being a Ni-based alloy having a thickness of 10 to 50 μm,
The surface-plated layer is made of Cr having a thickness of 5 to 30 μm, and the average surface roughness Ra of the surface of the surface-plated layer is 3 to 15 μm.

The Ni-based alloy of the lower plating layer is Ni-
It is desirable to use any one of W alloy, Ni-P alloy, Ni-B alloy, and Ni-WB alloy.

The base material of the roll of the present invention is not limited,
It is preferable to use copper, a copper alloy, copper plated with Ni, or a copper alloy.

[0026]

An example of the structure of a continuous casting apparatus for thin metal plates using the roll of the present invention will be described with reference to FIGS.

FIG. 1 is a vertical cross-sectional view in a side direction showing a single roll type continuous casting machine. Molten steel 6 in a tundish 5 provided adjacent to a cooling single roll 4 rotating in the direction of the arrow
Is continuously supplied at a speed at which a metal thin plate 7 having a predetermined thickness is obtained, and the metal thin plate 7 is continuously cast while being poured onto a cooling type single roll 4 rotating at a speed having a constant relationship with this speed.

FIG. 2 is a vertical cross-sectional view in a side direction showing a twin roll horizontal pouring type continuous casting machine. In this system, the molten steel 6 is supplied from the tundish 5 to a constant gap between the upper cooling roll 8 and the lower cooling roll 9 and cooled by both rolls.

FIG. 3 is a vertical sectional view in a side direction showing a twin roll top pouring type continuous casting machine method. In this method, the molten steel 6 is directly supplied to the constant gap between the cooling rolls 10 having the same diameter without passing through the tundish, and is cooled by both rolls.

The roll of the present invention may be a twin-roll method or a single-roll method as long as it is a continuous casting apparatus for thin metal plates using a cooling roll, and a method of supplying molten metal (top pouring, bottom pouring, side pouring, It can be applied to any of the above types, such as obliquely upward pouring and obliquely downward pouring.

Next, the reason why the roll of the present invention is limited as described above and its function and effect will be explained.

The starting point of surface irregularities and waviness of the thin metal plate is that thermal stress is generated in the surface layer of the solidified shell due to cooling from the cooling roll side and the solidified shell is deformed. That is,
Non-uniform contact between the roll and the deformed shell results in non-uniform solidification. In the convex part of the surface of the thin metal plate that is in close contact with the roll, solidification progresses further to form a thick shell, but in the concave part of the surface of the thin metal plate that is away from the roll, solidification is delayed and the shell thickness becomes thin. Non-uniformity occurs. In addition, the recessed portion of the surface of the thin metal plate is fragile at high temperatures, and cracks easily occur due to stress concentration.

The size and shape of the irregularities on the surface of the thin metal plate depend on the cooling conditions of the roll, and the forms and causes of these defects are as described above.

One of the objects of the present invention is to prevent the occurrence of the above-mentioned form C defect. To this end, it is effective to set the range of the average surface roughness Ra of the roll surface to 3 to 15 μm. That is, the surface of the roll is roughened to a predetermined roughness, and the gentle cooling effect by forming the air gap of the roll surface concave portion, and the roll surface convex portion is applied to the metal thin plate surface at an interval narrower than the hexagonal concave interval of the metal thin plate. The C defect can be prevented by the effect of suppressing thermal deformation based on the uneven transfer that positively imparts fine unevenness.

The reason why the range of the average surface roughness Ra of the roll surface is set to 3 to 15 μm as described above will be explained in detail with reference to FIG.

First, a continuous casting test was conducted using rolls having various average surface roughness, and the relationship between the average surface roughness of the roll surface and the average surface roughness of the metal thin plate was examined. FIG. 4 is a diagram showing this relationship.

On the roughened roll surface, the molten steel does not completely penetrate because of the air gap of the recess.
That is, the uneven shape of the roll surface is not directly transferred to the surface of the thin metal plate. Assuming that the average surface roughness of the roll surface is Ra (x) and the average surface roughness of the metal thin plate surface is Ra (y), there is a relation of the following equation between them.

Ra (y) = (a / 100) × Ra (x) + b where a represents the degree to which the surface roughness of the roll is transferred to the surface roughness of the thin metal plate, that is, the transfer rate (%). , B are roughnesses (μm) due to minute irregularities on the surface of the thin metal plate caused by thermal contraction of the surface of the solidified shell. As shown in FIG. 4, the transfer rate a is 20 to 30% and the roughness b is 1.0 μm. Further, the above-mentioned morphology C defect on the surface of the metal thin plate, that is, the microcracks associated with the hexagonal recess, is the average surface roughness R of the surface of the metal thin plate.
It does not occur when a (y) is 1.8 μm or more. On the other hand, when the average surface roughness Ra (y) of the metal thin plate surface exceeds 5.0 μm, minute cracks are generated in some of the dents on the metal thin plate surface caused by the transfer of irregularities on the roll surface. Therefore, the range of the average surface roughness Ra (y) of the appropriate metal thin plate surface where no microcracks are generated is 1.8 to 5.0 μm.

As a result of further detailed investigation, the surface of these sound metal thin plates has a depth of 10 to 20 at intervals of about 0.5 mm.
It was found that there were microscopic depressions of μm. This minute depression does not deteriorate the surface quality of the thin metal plate,
The unevenness of the roll surface was positively transferred, and the recess interval of about 0.5 mm corresponds to 1/4 to 1/10 of the glaze-like recess interval of the defect form C. That is, if minute recesses having a depth of 10 to 20 μm are positively provided on the thin metal plate side at intervals of about 0.5 mm, which corresponds to 1/4 to 1/10 of the interval of the hexagonal recesses in the C defect, the hexagonal recesses will be formed. In addition to suppressing deformation, the gap between the recesses transferred to the thin metal plate is sufficiently narrow, so that stress concentration on the minute recesses on the surface of the thin metal plate is suppressed. In addition, the hexagonal dent caused by thermal deformation locally recovers heat from the roll and becomes a fragile high temperature part, and minute cracks are likely to occur in this dent, but the surface of the metal thin plate transferred from the rough surface of the roll The minute dents are well-cooled because they are in close contact with the convex portions on the roll surface, and there is no local recuperation and no minute cracks occur.

In order to positively transfer the minute recesses from the rough surface of the roll, it is important to adjust the average surface roughness on the roll side and provide the metal thin plate with recesses having a predetermined interval and depth. As shown in FIG. 4, since the transfer rate a of the surface roughness from the roll to the thin metal plate is about 20 to 30%, the average surface roughness Ra of the roll surface is preferably 3 to 15 μm.

If the average surface roughness Ra is less than 3 μm, the effect of sufficiently preventing the hexagonal dents formed on the surface of the thin metal plate cannot be obtained. On the other hand, when Ra exceeds 15 μm, the unevenness of the roll surface is transferred to the surface of the metal thin plate, the surface roughness of the metal thin plate becomes large, which is not desirable in terms of quality, and the dent on the surface of the metal thin plate caused by the transfer of the rough surface of the roll In some cases, microcracks may start from the part.

As shown in FIG. 4, since the transfer rate a of the average surface roughness of the roll has a range of 20 to 30%, the average of the roll surface which is particularly desirable in order to stably obtain the hexagonal depression prevention effect. The surface roughness Ra is in the range of 5 to 10 μm.

FIG. 5 is a diagram showing the roughness of the roll surface having an average surface roughness Ra of 5 μm as an example of the present invention. The irregularities on the surface of the roll of the present invention have a shape as illustrated, regardless of the circumferential direction or axial direction of the roll.

In order to prevent the hexagonal dents, it is effective to positively give the dents of the hexagonal dents 1/4 to 1/10 of the pitch of 2 to 5 mm at intervals of about 0.5 mm to the surface of the metal sheet. However, in consideration of the transfer rate, it is desirable that the interval between the protrusions and protrusions on the roll surface is about 0.05 to 0.25 mm.

Next, lower layer plating and surface layer plating on the roll surface will be described.

In order to stably continuously cast a metal thin plate having a good surface condition, it is important to maintain the predetermined roll surface state. However, if the roll surface is soft,
During operation, not only the surface condition of the roll changes and its effect is lost, but also the surface of the roll is scratched in the circumferential direction, which may impair the surface quality of the thin metal plate. In order to prevent deterioration such as softening, cracking, and seizure of the roll surface during operation, it is effective to perform the following hard plating treatment.

FIG. 6 is a longitudinal sectional view of the roll surface layer showing the hard plating layer on the surface of the cooling roll.

In the figure, reference numeral 1 is a surface plating layer, 2 is a lower plating layer, and 3 is a roll base material.

The hard plating layer on the roll surface is composed of two layers, a lower plating layer 2 and a surface plating layer 1. The lower plating layer 2 is one of P, B, Fe, Co, Cu and W.
A Ni-based alloy containing two elements is used to plate one layer or multiple layers to a thickness of 10 to 50 μm. Among these Ni-based alloys, Ni-W alloy, Ni-P alloy, Ni-B alloy, Ni
One of the -WB alloys is preferable because it has high hardness even at high temperatures. The surface plating layer 1 is Cr-plated and has a thickness of 5 to 30 μm.

The above Ni-based alloy of the lower plating layer 2 has high hardness at high temperature, is effective in preventing softening of the roll surface and maintaining a predetermined average surface roughness Ra. Its thickness is 1
If it is less than 0 μm, the effect of preventing softening cannot be obtained and the surface irregularities are deformed. On the other hand, if it exceeds 50 μm, the temperature of the surface Cr plating layer rises because the lower plating layer is too thick, the thermal stress on the surface of the Cr plating layer increases, and cracks occur on the surface of the plating layer.

The lower plating layer 2 may be a single layer,
For example, if the Ni-B alloy and the Ni-W alloy are formed into two layers, the thermal stress in the plating layer is relaxed, and the roll life is further improved.

Cr in the surface plating layer prevents the Ni-based alloy in the lower plating layer from sticking to the thin metal plate. Its thickness is 5
If it is less than μm, the anti-seizure effect cannot be obtained. on the other hand,
If it exceeds 30 μm, the temperature of the Cr plating layer rises, the thermal stress on the surface of the Cr plating layer increases, and cracks occur on the surface of the plating layer.

Therefore, it is appropriate that the total thickness of the hard plating layer is 15 to 80 μm. The preferred total thickness range is 20-70 μm.

As the base material of the roll of the present invention, a sleeve made of a heat-resistant alloy material such as stainless steel or Ni-base alloy, which is usually used for rolls, can be used. It is best to use a superior copper or copper alloy sleeve. In addition to this, in order to protect the surface of the copper or copper alloy and adjust the cooling ability, a Ni plating layer may be previously provided as a base plating on the surface of the base material of the roll. The upper limit of the desirable Ni plating layer thickness when performing undercoating is 3 mm. Since copper, a copper alloy, or Ni is soft, it is easy to perform a predetermined surface roughening on the roll surface, for example, a mechanical method such as shot blasting.

When the above heat-resistant alloy material is used as the roll base material, the sleeve thickness is preferably 20 to 40% of that of the copper-based material in order to make the degree of slow cooling equal to that of the copper-based material. .

The hard plating treatment of the surface layer portion is preferably carried out after a predetermined surface roughening treatment in advance. Rough surface processing is not impossible after hard plating treatment, but it is difficult to process because it is hard, and it may cause damage such as cracks on the surface layer plating, or cracks occur during use due to residual stress during processing There is a fear.

When applying hard plating after roughening the surface of the roll, pay attention to the change in surface roughness before and after construction,
The final finish roughness of the roll surface is a predetermined average surface roughness Ra 3
It is important that the thickness is in the range of -15 μm.
The average surface roughness after the hard plating treatment with a total thickness of 15 to 80 μm is about 10% larger than the average surface roughness before the treatment. Therefore, it is necessary to roughen the surface in advance so that the average surface roughness Ra before the hard plating treatment is 2.7 to 13.5 μm.

As an example of the surface roughening method of the roll of the present invention, a Ni alloy-plated copper alloy roll is mechanically mechanically shot-blasted so that the average surface roughness Ra becomes 2.7 to 13.5 μm. Roughen. Next, thickness 10-50
A Ni alloy plating having a thickness of 5 μm is applied, and a Cr plating having a thickness of 5 to 30 μm is applied. In this way, the roll of the present invention has an average surface roughness Ra of the final finished surface within a predetermined range of 3 to 15 μm.

For cooling the roll of the present invention, it is desirable to apply an internal water cooling system. Further, during operation, in order to maintain the effect of the roll of the present invention, the roll surface may be brushed. The roll of the present invention is not limited to stainless steel, but also carbon steel, high alloys, non-ferrous metals and the like,
The same effect can be expected.

[0060]

【Example】

(Test 1) Using the single roll type continuous casting machine shown in FIG. 1, a thin metal plate of stainless steel SUS304 having a thickness of 1.0 mm and a width of 250 mm was manufactured at a casting speed of 50 m / min. The cooling roll was made of a copper alloy sleeve (thickness: 30 mm) plated with Ni having a thickness of 2 mm, roughened by shot blasting, and subjected to predetermined hard plating shown in Table 1 by shot blasting. The roll has a diameter of 600 mm, a body length of 400 mm, and a water-cooled structure inside the roll. The roll was cooled by flowing water at a flow rate of 8 m / s into a cooling groove provided on the inner surface side of the sleeve. Table 1 shows the properties of the thin metal plate and the damage on the roll surface.

[0061]

[Table 1]

The non-uniformity CV and dents on the surface of the metal thin plate shown in Table 1 are defined as follows.

CV (%) = [(standard deviation of thickness) / (average of thickness)] × 100 Good: CV <10 Slightly bad: 10 ≦ CV <15 Bad: 15 ≦ CV Metal thin plate surface dent Classification A: Large unevenness with vertical cracks B: 10 to 50 mm pitch, undulation of 50 to 100 μm undulation C: 2 to 5 mm pitch, 20 to 30 μm depth hexagonal recesses As shown in Table 1, determined by the present invention. Under the roll surface roughness and hard plating conditions in the ranges, there was no dent or microcrack on the surface of the thin metal plate, and there was no damage on the roll surface after use.

The surface roughness of the roll is the average surface roughness Ra of 2.
In the comparative example in which the thickness is 5 μm or less, the thickness of the thin metal plate is not uniform and the surface is dented. Further, in the comparative example in which Ra was 20 μm, the roughness of the surface of the metal thin plate was increased due to the uneven transfer of the rough surface of the roll, and minute cracks starting from the recessed portion of the surface were generated and the surface quality was deteriorated. Furthermore, in the comparative examples in which the thickness of the hard plating layer is outside the range of the present invention, surface scratches, seizures, softening, cracks and the like occur during operation, the roll surface deteriorates, and stable effects were not obtained. .

(Test 2) Using the twin roll lateral pouring type continuous casting machine shown in FIG. 2, a thin metal plate of stainless steel SUS304 having a thickness of 1.7 mm and a width of 250 mm was produced at a casting speed of 50 m / min. The cooling roll is made of Ni-plated copper alloy sleeve with a thickness of 2 mm as the base material, roughened by shot blasting, then Ni-W with a thickness of 30 μm and Cr with a thickness of 10 μm.
Hard plating was applied. The final finished surface roughness of the roll surface was three kinds of average surface roughness Ra of 3 μm, 5 μm and 8 μm.

The upper roll has a diameter of 500 mm and a body length of 250
mm, the diameter of the lower roll is 600 mm, the body length is 400 mm, and the sleeve thickness is 15 mm. Upper and lower roll cooling
Water was applied at a flow rate of 5 m / s to the cooling groove provided on the inner surface of the sleeve.

All the metal thin plates obtained by using the rolls having the above-mentioned three types of average surface roughness were sound and had no dents or microcracks. Also, stable casting was possible without damage to the peripheral surface of the roll or seizure of the thin metal plate.

(Test 3) Using a twin roll top pouring type continuous casting machine shown in FIG. 3, a thin metal plate of stainless steel SUS304 having a thickness of 1.8 mm and a width of 400 mm was manufactured at a casting speed of 50 m / min. For the cooling roll, a copper alloy sleeve with a thickness of 2 mm Ni is used as the base material, and after roughening the surface by shot blasting, hard plating of Ni W with a thickness of 30 μm and Cr with a thickness of 10 μm is applied. Finished surface roughness is the average surface roughness R
It was 6 μm for a. The twin rolls have a diameter of 600 mm, a body length of 400 mm, and a sleeve thickness of 15 mm. The twin rolls are cooled with a flow velocity of 5 m in the cooling groove provided on the inner surface of the sleeve.
Water was run at / s.

The cast metal sheet is sound, dented,
There were no microcracks. In addition, stable casting was possible without damage to the roll surface or seizure of the thin metal plate.

[0070]

According to the roll of the present invention, due to the synergistic effect of gentle cooling of the roll surface and suppression of thermal deformation by the transfer of unevenness,
It is possible to prevent waviness of a thin metal plate due to uneven solidification and generation of minute dents on the surface of the thin metal plate due to thermal deformation of the solidified shell, and to perform stable continuous casting of a thin metal plate having a good surface property. In addition, the above effect can be maintained by preventing the softening, cracking, and seizure of the roll surface during the operation by the hard plating of the surface layer portion.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view in a side direction showing a single roll type continuous casting machine to which a roll of the present invention can be applied.

FIG. 2 is a vertical cross-sectional view in a side direction showing a twin roll horizontal pouring type continuous casting machine to which the roll of the present invention can be applied.

FIG. 3 is a vertical cross-sectional view in a side direction showing a twin roll top pouring type continuous caster to which the roll of the present invention can be applied.

FIG. 4 is a diagram showing the relationship between the average surface roughness of the roll surface and the average surface roughness of the metal thin plate.

FIG. 5 is a diagram showing an example of roughness of a roll surface having an average surface roughness Ra of 5 μm.

FIG. 6 is a vertical cross-sectional view of a roll surface layer portion showing a hard plating layer on the roll surface.

[Explanation of symbols]

1: surface plating layer, 2: lower plating layer,
3: base material roll, 4, 8, 9, 10: cooling roll, 5: tundish, 6: molten steel, 7: thin metal plate

Claims (2)

[Claims] 1. A cooling roll used for continuously casting a thin metal plate by solidifying a molten metal on a peripheral surface of a roll, wherein the roll surface has an average surface roughness Ra of 3 to 15 μm. Roll for thin sheet continuous casting. 2. A cooling roll used when solidifying a molten metal on a peripheral surface of a roll to continuously cast a thin metal plate, the roll surface having a two-layer structure of a lower plating layer and a surface plating layer, and a lower layer. The plating layer is made of a Ni-based alloy having a thickness of 10 to 50 μm, and the surface plating layer is made of Cr having a thickness of 5 to 30 μm.
A roll for continuous casting of a thin metal plate, characterized in that the average surface roughness Ra of the surface of the surface plating layer is 3 to 15 µm.