KR101264228B1 - Casting method by using twin roll for improving strip's surface after rolling - Google Patents

Abstract

The present invention relates to a twin-roll thin plate casting method having a good product surface quality after rolling, wherein molten steel is injected between two casting rolls rotating in opposite directions to form a thin plate, and the thin plate is passed through a loop fit to a rolling roll. In the twin roll type sheet casting method of manufacturing a sheet by rolling, a double roll type sheet casting method having a good surface after rolling is characterized in that the oxygen concentration in the roof pits is 10% or more. The thin plate 7 passed through) is characterized in that a large amount of oxide scale is present on the surface and is uniformly distributed.

The uniform distribution of oxidation scales promotes wear of the rolling rolls, thereby preventing the occurrence of linear flaws on the surface of the rolling rolls, thereby providing an effect of improving the roughness of the thin plate surface.

Oxidation scale, loop fit, wire flaw

Description

CASTING METHOD BY USING TWIN ROLL FOR IMPROVING STRIP'S SURFACE AFTER ROLLING}

The present invention relates to a method for managing the surface roughness of the rolling mill in a thin sheet casting process, and more particularly, after the rolling by controlling the oxygen concentration in the roof pits to generate an oxide scale to improve the roughness of the rolling roll surface. A casting method for improving the surface quality of a product.

The sheet is also continuously cast in a twin roll casting machine, in which molten metal is injected through the nozzle (2) between the two casting rolls (3) cooled while rotating in the opposite direction, solidified to form a solidified shell, It is pressed down and a thin plate is produced. At the end of the casting roll 3, there is an edge dam 5 made of ceramic to prevent the molten steel outflow to the end. The casting roll 3 has a cooling water hole therein to supply cooling water to cool the casting roll, and the casting roll is made of a good heat transfer material such as copper, and the surface is coated with nickel for wear resistance. have. The coating layer has a non-directional roughness is formed using a method such as shot blasting to improve the solidification of the steel, the shot blasting method is a method of imparting the roll surface roughness by spraying a fine metal powder on the processed roll surface. The rough sheet is roughly rolled at a temperature of about 1100 to 1200 degrees by hot rolling at a reduction ratio of 20 to 40%.

In general, in the thin plate casting process, rolling is performed with one stand, so that high pressure is reduced at high temperature. Since rolling is performed in severe conditions, management of a rolling roll is very important. To this end, the rolling roll uses a high-strength steel HSS roll, and if the surface of the rolling roll is poor, it is taken out and replaced with a new rolling roll. In this process, since the casting is in progress in the casting apparatus, a non-rolled portion that is not rolled is generated, so that there is a problem that the error rate is lowered.

Normally, the oxygen concentration in the roof pits 8 is controlled at 1 to 5%. Oxygen scales are generated on the surface of the sheet by oxygen, causing wear of the rolling rolls. In addition, due to the hardness difference between the carbide and the matrix of the rolling roll material selectively wear or hard carbide fall off, scraping the surface of the rolling roll to produce a linear flaw generated in the rolling direction. Such linear flaws are transferred to the thin plate surface during the rolling process, and linear flaws are also generated on the thin plate surface. Therefore, in order to suppress the occurrence of such linear defects, it is necessary to prevent selective wear from occurring.

However, as a means for managing the surface of the rolling rolls well, the application of hydraulic rolling and ORG or RSM grinding the surface of the rolls when the rolling rolls become poor have been practically used. There was a problem with the installation during the application.

The present invention has been made to solve the above problems, by controlling the oxygen concentration in the roof feet to 10% or more to increase the oxidation scale on the surface of the thin plate to uniformly distribute the surface of the rolling roll after rolling to improve the surface It aims at making quality favorable.

In the present invention, molten steel (4) is injected between two casting rolls (3) rotating in opposite directions to form a thin plate (7), and the thin plate (7) is passed through a loop fit (8) and rolled into a rolling roll In the twin roll type sheet casting method for producing a sheet, the product surface having a good rolling after rolling is provided, characterized in that the oxygen concentration in the roof pits 8 is 10% or more.

In addition, the present invention is characterized in that the thin plate (7) passing through the loop pit (8) is present in a large amount of oxide scale on the surface, evenly distributed.

The present invention provides the effect of improving the roughness of the thin plate surface by controlling the concentration of oxygen in the loop fit so that the wear of the rolling roll is promoted by the uniformly distributed oxidation scale so that no linear scratches are generated on the surface of the rolling roll.

The present invention is a casting method for improving the surface of the thin plate during twin roll type sheet casting by controlling the oxygen concentration in the roof pits (8) to uniformly distribute a large amount of oxide scale on the surface of the plate to promote the wear of the rolling roll surface The present invention relates to a method of preventing occurrence of linear defects on the surface of a rolling roll. At this time, the oxygen concentration in the roof pits is only 10% or more effective.

In the present invention, in order to suppress the formation of linear flaws on the surface of the rolling rolls in the sheet casting process, the wear of the rolling rolls is accelerated. Wear occurs almost irrespective of Therefore, even if linear flaws are generated due to the selective wear of the rolling rolls, since the oxide scale wears not only carbide but also the base, the linear flaw does not occur because wear by the oxide scale is dominant. In order to perform this action, a light oxidation scale must be large on the surface of the thin plate and must be uniformly distributed.

In order to achieve this object, wear of the rolling roll was promoted when the concentration of oxygen in the roof pits at the front end of the rolling mill was 10% or more, and no linear flaw occurred when the surface of the rolling roll was observed after the rolling was finished. And as a result of confirming the roughness of the thin plate surface, it maintained very favorable state.

At the front end of the rolling mill, the sheet is rolled between 1100 and 1200 ° C while cooling at 1300 ° C. When the atmospheric oxygen concentration is increased in this section, the surface of the thin plate 7 is oxidized, and a large amount of oxidizing scale is generated. The oxidized scale produced in such a large amount serves to abrasion the surface of the rolling roll during rolling, thereby eliminating the selective wear due to the rolling roll material.

2 is a photograph of the surface of the rolling roll after rolling in a twin-roll thin sheet casting process, the surface of the rolling roll after rolling is generated linear defects, such linear defects are transferred to the thin plate surface to create the linear defects on the thin plate surface, causing quality defects .

FIG. 3 is a photograph of a rolling roll surface after performing a casting experiment and a rolling test by controlling the oxygen concentration of the roof pits to 10% in a twin-roll thin sheet casting process, and it can be seen that line defects do not occur on the rolling roll surface after rolling. .

In addition, FIG. 4 is a result of measuring the surface roughness of the thin plate after performing the casting experiment and the rolling test to control the oxygen concentration of the loop fit 1 ~ 5%, 10% in the twin-roll thin plate casting process, the oxygen concentration is 1 In the case of ˜5%, the surface roughness, that is, the roughness of the thin plate increased from the beginning of rolling, and in the case of the oxygen concentration of 10%, the surface roughness of the thin plate was kept constant even when the rolling was 300 tons or more.

Therefore, on the basis of the experimental results, it can be seen that by controlling the oxygen concentration of the roof pits to 10%, rolling can improve the surface roughness of the thin plate, thereby improving the quality.

* Figure 1 is a schematic diagram of a twin roll sheet metal casting process,

* Figure 2 is a photograph of the surface of the rolling roll after rolling in a twin roll thin plate casting process,

* Figure 3 is a rolling roll surface photograph after performing a casting experiment and a rolling test by controlling the oxygen concentration of the roof feet to 10% in the twin-roll thin plate casting process,

* FIG. 4 shows the results of measuring the surface roughness of the thin plate after performing the casting test and the rolling test by controlling the oxygen concentration of the roof pits to 1 to 5% and 10% in the twin roll thin plate casting process.

 ♠ Explanation of the symbols for the main parts of the drawings ♠

1: tundish 2: nozzle

3: roll 4: molten steel

5: edge dam 6: brush roll

7: thin sheet 8: loop fit

9: meniscus shield 10: pinch roll

11: rolling mill

Claims (2)

Molten steel 4 is injected between two casting rolls 3 rotating in opposite directions to form a thin plate 7, and the thin plate 7 is rolled with a rolling roll through a loop fit 8 to produce a plate. In the twin-roll type sheet casting method, By controlling the oxygen concentration in the roof pit 8 to 10% to 100% when the thin plate 7 passes, the oxide scale is formed on the thin plate 7 to a predetermined thickness to promote wear of the rolling roll. A double roll type thin plate casting method having a good product surface after rolling, in which line flaws do not occur in the rolling roll and the thin plate (7) passing through the rolling roll. The method of claim 1, The thin plate (7) passed through the roof pits (8) has a good amount of oxide scale on the surface, it is uniformly distributed, characterized in that the product surface after rolling good bi-roll thin plate casting method.

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