KR20120072495A - Casting roll of twin roll strip caster - Google Patents

Abstract

PURPOSE: A casting roll of a twin roll strip caster is provided to prevent partial grooves formed on the seal plate of an edge dam when squeezing molten steel because an edge dimple has a larger roughness than other dimples. CONSTITUTION: A casting roll(1,1') of a twin roll strip caster comprises dimples formed on a surface thereof. An edge dimple(a) formed from edges to 10mm of the width of the casting rolls has a larger roughness than a main dimple(b) formed in the rest portions.

Description

Casting roll of twin roll sheet metal casting machine {CASTING ROLL OF TWIN ROLL STRIP CASTER}

The present invention relates to a casting roll of a twin roll thin plate casting apparatus, and more particularly, to a twin roll thin plate casting apparatus for casting a thin plate from molten steel injected from a tipped dip immersion nozzle, and a dimple is formed and processed on the surface thereof. It's about rolls.

A general twin roll type sheet casting apparatus, as shown in Figure 1, a pair of casting roll (1, 1 ') and the side of the casting roll to rotate in the opposite direction through the immersion nozzle (4) of the tundish (3) The molten steel is supplied to the roll sump 8, which is a space formed by the edge dam 2 attached to the molten steel, to form a molten steel pool, and the casting roll is cooled by water while rotating the pair of casting rolls 1 and 1 '. Through the heat flux (heat flux) to the inside of the casting roll through to rapidly solidify the molten steel to prepare a cast (7).

The edge dam 2 forming the side of the twin roll type sheet casting apparatus contacts the rotating casting rolls 1, 1 'and wears the seal plate, which is a refractory material. In consideration of this, the seal plate should be made thick. However, since refractory seal plates are expensive, it is desirable to be able to use them continuously for a long period of time while wearing a minimum thickness.

By the way, as shown in Figures 2 to 4, when casting the stainless steel grade by the twin-roll thin sheet casting apparatus, when the solidification ability of the edge portion of the casting roll is good, the molten steel is squeezing out due to the squeezing flow (squeezing flow) ), The strength of the molten steel is increased, the force to wear the seal plate is increased, and as a result, the seal plate is locally worn by the extruded reaction molten steel to generate a groove.

These grooves irregularize the shape of the edge of the cast steel, and are pressed when rolled in a later process, causing press-fitting defects on the surface of the thin plate, causing product defects.

Of course, in order to solve this problem, it can be controlled to increase the amount of wear of the seal plate of the edge dam, but the expensive seal plate to wear early, the production cost is high, and the same seal plate to be cast There is a problem that the amount can be reduced and the productivity is lowered.

According to the present invention, as the molten steel is extruded, local grooves generated in the seal plates of the edge dams are prevented from being generated, thereby making the shape of the thin plate edge portion satisfactory, thereby reducing the excessive amount of wear of the edge dams provided to remove the grooves. The purpose of the present invention is to provide a casting roll of a twin-roll thin sheet casting apparatus capable of reducing cost by increasing the casting amount to improve productivity and extending the life of the edge dam.

In order to achieve the above object, the present invention provides a casting roll of a thin-rolled sheet casting apparatus for casting a thin plate from molten steel injected from a immersion nozzle of a tundish, the dimple is formed on the surface of the casting roll, the edge of the casting roll Provided is a casting roll of a twin roll thin plate casting apparatus, characterized in that the roughness value of the edge portion dimple formed up to a point of 10 mm in the casting roll width direction is larger than the main dimple formed in the remaining portion.

In this case, the edge dimple has a feature that the roughness value is larger than Ra 5 to 30 μm than the main dimple.

In addition, the edge dimple is characterized in that it is formed from the edge of the casting roll to a point of 2 to 10 mm in the casting roll width direction.

Furthermore, the dimple is characterized by being processed by the shot blasting method.

According to the present invention, the molten steel is extruded by the compression flow near the roll nip to prevent the occurrence of local grooves generated in the seal plate of the edge dam, thereby making the shape of the thin plate edge portion satisfactory, thereby providing the removal of the grooves. To reduce the cost of the edge dam can be reduced by increasing the amount of casting to increase the productivity, and the life of the edge dam can be extended.

1 is a schematic view of a typical twin roll sheet metal casting device.
Figure 2 is a schematic diagram showing the structure of the edge dam.
Figure 3 is a schematic diagram showing the groove generation of the seal plate in the middle and top of the edge dam.
Figure 4 is a schematic diagram showing the groove generation of the seal plate in the lower portion of the edge dam.
5 is a schematic view of stochastic surface structure (a) and deterministic surface structure (b) by the shot blasting method.
6 is a schematic view showing a state of solidification shell and groove generation according to the practice of the invention and comparative examples.
7 is a photograph of the thin plate edge portion of the invention and comparative examples.

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.

The casting roll of the twin-roll thin sheet casting apparatus according to the present invention prevents the occurrence of local grooves generated in the seal plate of the edge dam while the molten steel is squeezed out by the squeezing flow near the roll nip to prevent the occurrence of local grooves in the sheet edge portion. It is characterized by making the shape good, thereby reducing the excessive amount of wear of the edge dams given to remove the grooves.

Usually, since the slab 7 produced by the twin roll sheet casting apparatus is a slab as thin as 2 to 6 mm, the initially formed solidification shell has a great influence on the surface properties of the slab. That is, since the time between the molten steel and the cast roll is very short, the thickness of the solidified shell becomes uneven, which causes defects such as cracks and overlapping defects on the surface of the cast steel, which adversely affects subsequent rolling processes. The surface gloss of the product is lowered, which lowers the product value.

Therefore, in the twin-roll thin plate casting process, the surface of the casting roll for processing dimples on the surface of the casting roll by various methods to effectively disperse the thermal stress of the cast steel to remove defects such as cracks on the surface of the cast steel. Treatment is essential. By forming dimples, a gas gap, which is an insulating layer, is formed between the cooling roll and the solidification shell to reduce the heat extraction of the cooling roll to induce gentle cooling of the solidification shell. At the same time, solidification starts from the edge of the dimple to make the thickness of the solidification shell uniform.

However, when the size of the dimple is large, the passage of heat transfer is reduced rather than when the size of the dimple is reduced, and the solidification speed of the molten steel is reduced. When the size of the dimple is small, the solidification point per unit area is increased than the case where the dimple is small, and the solidification speed of the molten steel is increased. In the present invention, since the solidification ability of the edge portion of the casting roll is increased in the present invention, the molten steel is increased during casting, so that the strength of the molten steel is increased to prevent the occurrence of grooves formed by wearing the seal plate. As shown in Fig. 6 (a), the roughness value of the edge dimple (a) formed from the edge of the casting roll to the 10 mm point in the casting roll width direction is the roughness value of the main dimple (b) formed in the remaining portion of the casting roll. The thickness of the solidification shell of the edge portion in contact with the edge dam is made thinner than the thickness of the adjacent portion by processing larger to reduce the solidification point per unit area. Allow crabs to form.

As a result, the thickness of the solidification shell becomes thinner at the top of the edge dam, thereby reducing the rigidity, thereby reducing the generation of grooves in the seal plate, and at the bottom of the edge dam, the gap of the reactor molten steel increases, thereby reducing the extrusion pressure of the reactor molten steel. Therefore, the occurrence of grooves in the seal plate is reduced.

At this time, the formation of the dimple is preferably processed by the short blast method, as shown in FIG. 5, the short blast method is advantageous in having a relatively large and deep dimple having a stochastic structure, and relatively It is more suitable than laser to process and form dimples that are larger than dimples.

At this time, the edge dimple (a) is preferably formed from the edge of the casting roll to the point of 2 ~ 10mm in the casting roll width direction, if less than 2mm using the shot blasting method to the perfect shape on the edge of the casting roll This is because it is difficult to form a dimple having a problem, and if it exceeds 10 mm, it is not preferable because it affects the shape of the thin plate except for the part to be trimmed later.

In addition, the edge portion dimple (a) is preferably Ra 5 ~ 30㎛ larger than the roughness value of the main dimple (b), the difference between the edge dimple (a) and the main dimple (b) is 5㎛ If it is less than, the effect of reducing the solidification point per unit area cannot be expected. If the difference exceeds 30 µm, the shape of the dimple remains even after rolling in a subsequent step, resulting in poor surface gloss and deterioration in corrosion resistance of stainless steel.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The cast rolls used were 1,400 mm in diameter, 1,350 mm in width, made of copper, the surface was plated with nickel, and the inside was cooled by water cooling. Then, the roughness was given to the surface of the casting roll by the shot blasting method using a steel ball, the specific conditions are as shown in Table 1 below.

In addition, the steel grade is STS 304, 100 tons cast to a 3.5mm thickness.

[Table 1]

As shown in Table 1, in the case of Comparative Examples 1 and 2 in which the roughness values of the dimples formed on the casting roll are the same or the difference is less than Ra 5 µm, as shown in FIG. 6 (b), the solidification point per unit area decreases. Since the effect was not large, there was no significant change in the amount of wear of the seal plate. As shown in FIG.

On the other hand, when the roughness value of the edge dimple is Ra 5 to 30 µm larger than the roughness value of the main dimple, as shown in FIG. 6 (a), the solidification shell thickness of the edge portion in contact with the edge dam is solidified. Since the extrusion pressure of the molten steel is reduced by being formed thinner than the shell thickness, the generation of grooves of the seal plate is reduced, and the quality of the edge portion of the casting material is good as shown in FIG.

As a result, the present invention prevents the occurrence of local grooves generated in the seal plate of the edge dam while the molten steel is extruded, thereby making the shape of the thin plate edge portion satisfactory, and thus the excessive amount of wear of the edge dam provided to remove the groove. By reducing the casting amount can be greatly increased.

100. Twin roll lamination casting device
1,1 '. Casting Roll 2. Edge Dam
3. Tundish 4. Immersion Nozzle
5. Meniscus Shield 6. Brush Roll
7. Cast 8. Rollsump
9. Molten steel 11. Solidified shell
12. High molten steel 21. Base plate
22. Seal plate 23. Groove

Claims (4)

In the casting roll of the twin-roll type sheet casting apparatus for casting a thin plate from the molten steel injected from the immersion nozzle of the tundish,
Dimples are formed on the surface of the casting roll,
The edge roll dimple formed from the edge of the casting roll to a 10 mm point in the casting roll width direction has a larger roughness value than the main dimple formed in the remaining portion. The method of claim 1,
Roughness value of the edge dimple is greater than Ra 5 ~ 30㎛ than the main dimple casting roll of the thin roll type sheet casting apparatus. The method of claim 1,
The edge portion dimple is formed in the casting roll width direction 2 ~ 10mm point from the edge of the casting roll, the casting roll of the twin roll type sheet casting apparatus, characterized in that. The method of claim 1,
The dimple is a cast roll of a twin roll thin plate casting apparatus, characterized in that processed by the shot blasting method.

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