SURFACE TREATMENT METHOD AND CASTING ROLL MANUFACTURED BY THE SAME

Abstract

A surface treatment method capable of preventing a surface defect by improving a surface shape determining surface roughness of a casting roll and a casting roll manufactured by the surface treatment method, are provided. A surface treatment method includes a concave-convex pattern forming operation of forming a concave-convex pattern on a surface of a casting roll; and an electrolytic polishing operation of electrolytically polishing so that a plurality of convex portions and concave portions of a concave-convex pattern formed in the concave-convex pattern forming operation are treated to be rounded.

Claims

1. A surface treatment method comprising: a concave-convex pattern forming operation of forming a concave-convex pattern on a surface of a casting roll; and an electrolytic polishing operation of electrolytically polishing so that a plurality of convex portions and concave portions of a concave-convex pattern formed in the concave-convex pattern forming operation are treated to be rounded.

2. The surface treatment method of claim 1, wherein in the concave-convex pattern forming operation, a surface of the casting roll is surface-treated using a shot blasting process.

3. The surface treatment method of claim 2, wherein in the shot blasting process of the concave-convex pattern forming operation, when the casting roll is surface-treated, a shot ball having a diameter of at least 2.8 mm is projected.

4. A casting roll comprising: a casting roll main body; and a surface treated part formed on a surface of the casting roll main body and formed so that a plurality of convex portions and concave portions of a concave-convex pattern are treated to be rounded by the surface treatment method according to claim 1.

5. The casting roll of claim 4, wherein convex portions of the concave-convex pattern may be smoothly connected to concave portions of the concave-convex pattern adjacent thereto at an angle of less than 30 degrees.

6. The casting roll of claim 4, further comprising a coating layer formed on the surface of the casting roll main body.

Description

DESCRIPTION OF DRAWINGS

[0021] FIG. 1 is a schematic view illustrating a twin roll thin plate caster.

[0022] FIG. 2 is a perspective view illustrating a casting roll according to the related art.

[0023] FIG. 3 is a cross-sectional view illustrating a process in which a casting cast by a casting roll according to the related art is pressed as a thin plate.

[0024] FIG. 4 is a cross-sectional view taken along line I-I of FIG. 3.

[0025] FIG. 5 is a cross-sectional view taken along line II-II of FIG. 3.

[0026] FIG. 6A is a drawing illustrating a hook defect formed on a surface of a thin plate, FIG. 6B is a drawing illustrating a cross section of a hook defect, FIG. 6C is a drawing illustrating a concave-convex pattern of a thin plate surface in which a hook defect occurs, and FIG. 6D is a graph illustrated by a height/a width of a concave-convex pattern of a casting roll.

[0027] FIG. 7 is a perspective view illustrating a casting roll according to an exemplary embodiment.

[0028] FIG. 8 is a cross-sectional view illustrating a method of manufacturing a casting roll according to an exemplary embodiment.

[0029] FIG. 9 is a cross-sectional view illustrating a process in which a casting cast by a casting roll according to an exemplary embodiment is pressed as a thin plate.

[0030] FIG. 10 is a cross-sectional view taken along line III-III of FIG. 9.

[0031] FIG. 11 is a cross-sectional view taken along line IV-IV of FIG. 9.

BEST MODE FOR INVENTION

[0032] Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. An exemplary embodiment of the present disclosure may be modified to have various other forms, and the scope of the present disclosure is not limited to an exemplary embodiment described hereinafter. A shape, a size or the like of the elements in drawings may be exaggerated for clarity of description, and elements represented by the same reference numerals in the drawings are the same.

[0033] FIG. 7 is a perspective view illustrating a casting roll according to an exemplary embodiment, FIG. 8 is a cross-sectional view illustrating a method of manufacturing a casting roll according to an exemplary embodiment, and FIG. 9 is a cross-sectional view illustrating a process in which a casting cast by a casting roll according to an exemplary embodiment is pressed as a thin plate. In addition, FIG. 10 is a cross-sectional view taken along line III-III of FIG. 9, and FIG. 11 is a cross-sectional view taken along line IV-IV of FIG. 9.

[0034] With reference to FIGS. 7 to 11, a surface treatment method according to an exemplary embodiment may include a concave-convex pattern forming operation and an electrolytic polishing operation.

[0035] In an exemplary embodiment, in the concave-convex pattern forming operation, a concave-convex pattern 114 may be formed on a surface of a casting roll 110.

[0036] In detail, in the concave-convex pattern forming operation, a surface of a casting roll main body 112 configuring the casting roll 110 may be surface-treated using a shot blasting process, thereby forming the concave-convex pattern 114 through the shot blasting process.

[0037] The shot blasting process is used to treat a surface by projecting a shot ball B to a surface of the casting roll main body 112 of the casting roll 110. Here, the shot ball B described above may be a shot ball used in a shot blasting process according to the related art. Preferably, a shot ball B having a diameter of at least 2.8 mm is projected at high pressure to form a concave portion of the concave-convex pattern 114 in a concave form corresponding to a ball shape. In this case, a central part of the concave portion of the concave-convex pattern 114, pressed by the shot ball B, may be formed to be concave, and a pretreatment convex portion 114a, a part connected to another concave portion of the concave-convex pattern 114 adjacent thereto, may protrude sharply to be connected thereto.

[0038] For example, a convex portion of the concave-convex pattern 114 may be connected to a concave portion of the concave-convex pattern 114 adjacent thereto at an angle R of 30 degrees or more.

[0039] When the concave-convex pattern 114 is formed in the concave-convex pattern forming operation, the electrolytic polishing operation may be performed.

[0040] In the electrolytic polishing operation, a plurality of convex portions and concave portions of a concave-convex pattern 114 formed in the concave-convex pattern 114 forming operation are treated to be rounded.

[0041] In detail, in the electrolytic polishing operation, in which the casting roll 110 is immersed in an electrolytic polishing solution to be polished while being electrochemically dissolved, smoothing of fine concave and convex portions of 0.01 m to 0.1 m and removal of relatively large concave and convex portions of tens of m may be performed simultaneously, and polishing may be performed simultaneously.

[0042] An electrolyte used in the electrolytic polishing operation is mostly an acid solution. In addition, acetic anhydride, alkali, and phosphoric acid are used, and perchloric acid and chromic acid having strong oxidizing power are added thereto.

[0043] In the electrolytic polishing operation, the pretreatment convex portion 114a, a protruding part, is relatively quickly dissolved, thereby allowing the convex portion of the concave-convex pattern 114 after surface treatment of the casting roll 110 to be smoothly formed.

[0044] When the electrolytic polishing operation is performed for a total of 4 hours while a current is provided with a voltage of 7 V to 8 V, polishing of the pretreatment convex portion 114a, a sharply protruding part of the concave-convex pattern 114, is quickly performed. Thus, a convex portion of the concave-convex pattern 114 may be connected to a concave portion of the concave-convex pattern 114 adjacent thereto at an angle of less than 30 degrees to allow an entirety of the concave-convex pattern 114 to be smoothly formed.

[0045] In this case, electrolytic polishing conditions in the electrolytic polishing operation will be described in Table 1.

TABLE-US-00001 TABLE 1 Starting temperature Roll surface Electrolyte Voltage (V) Current (A) Minutes 35.6 35 7.9 1249 120 35.8 45 7.8 1200 60 42 46 7.7 986 40 43 51 7.4 250 20

[0046] The casting roll 110 manufactured in the surface treatment method described above may include a surface treated part formed by being treated to be rounded overall while the plurality of convex portions and concave portions of a concave-convex pattern 114 on a surface of the casting roll main body 112 are electrolytically polished.

[0047] As described above, in an exemplary embodiment, while the casting roll 110 passes through the electrolytic polishing operation to be surface-treated, a convex portion and a concave portion of the concave-convex pattern 114 are smoothly connected to each other, and thus, a surface of the casting Y passing through the casting roll 110 to be manufactured, may have a convex portion and a concave portion of a concave-convex pattern 114, which is smooth, corresponding to a surface treated part of the casting roll 110. Thus, a foreign substance such as oxide scale or the like is prevented from being inserted into convex portions adjacent thereto.

[0048] Even when a portion of a foreign substance is attached to a surface of the casting Y, the portion of a foreign substance may be easily eliminated by rolling oil L or the like in a process of being pressed by a rolling roll 130. Thus, a foreign substance is prevented from being inserted in a process of being rolled as the thin plate S. The rolling oil L allows frictional resistance between the casting Y and the rolling roll 130 to be reduced, thereby reducing insertion of a foreign substance.

[0049] Preferably, a convex portion of the concave-convex pattern 114 formed on the casting roll 110 may be connected at a smooth angle of less than 30 degrees when the convex portion thereof is connected to a concave portion adjacent thereto. In addition, a convex portion of the concave-convex pattern 114 formed on the casting Y cast by the casting roll 110 described above may be connected at a smooth angle of less than 30 degrees when the convex portion thereof is connected to a concave portion adjacent thereto.

[0050] In an exemplary embodiment, a coating layer formed using a material such as nickel or the like may be formed on the casting roll 110 to improve wear resistance of a surface of the casting roll main body 112. In addition, a surface treated part may be directly formed on the casting roll main body 112, or may be formed on the coating layer.

Example

[0051] In the casting roll 110 configured as described above, a convex portion of the concave-convex pattern 114 on a surface treated part is formed to be rounded. In addition, an angle in which a convex portion of the concave-convex pattern 114 of the casting Y manufactured using the casting roll 110 according to an example is connected to a concave portion adjacent thereto was measured, and a defect of the thin plate S manufactured in the form of a finished product by rolling the casting Y thereafter was measured.

[0052] With reference to Table. 2, an angle between a convex portion and a concave portion of the concave-convex pattern 114 formed on a surface of the casting Y cast by the casting roll 110 was measured.

[0053] When the casting roll 110 according to the related art was used, the number, in which an angle between a convex portion and a concave portion of a concave-convex pattern formed on the casting Y is 25 degrees or more, was 30 per area of 100 mm.sup.2, and the number, in which an angle between a convex portion and a concave portion thereof formed on the casting Y, is 30 degrees or more, was 10 per area of 100 mm.sup.2.

[0054] A hook defect H may occur in the thin plate S in the form of a final product in which the casting Y is rolled. In this case, a hook defect index representing the number of hook defects H formed in an area of 1 m.sup.2 was measured as 10.

[0055] When the casting roll 110 according to an exemplary embodiment was used, the number in which an angle between a convex portion and a concave portion of a concave-convex pattern formed on the casting Y is 25 degrees or more was 20 per area of 100 mm.sup.2, and the number in which an angle between a convex portion and a concave portion thereof formed on the casting Y is 30 degrees or more was 0.

[0056] In an exemplary embodiment, a hook defect H does not occur in the thin plate S in the form of a final product in which the casting Y is rolled.

TABLE-US-00002 TABLE 2 Angle between convex portion Rolling and concave portion on cast material strip surface surface 25 degrees or 30 degrees or hook more more H index (ea/100 mm.sup.2) (ea/100 mm.sup.2) (ea/m.sup.2) Note Before 30 10 10 Related art electrolytic polishing After 20 0 0 Exemplary electrolytic embodiment polishing

[0057] As described above, a convex portion and a concave portion of the concave-convex pattern 114 having an angle of 30 degrees or more on a surface of the casting Y may form a hook defect H in a rolling process. In an exemplary embodiment, a convex portion of the concave-convex pattern 114 is formed on a surface of the casting roll 110 to be rounded by electrolytic polishing to allow roughness to be an angle of less than 30 degrees, thereby preventing a hook defect H from being generated in a rolling process.

[0058] While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure as defined by the appended claims.