KR100494105B1 - A casting roll of twin roll strip caster - Google Patents

Abstract

The present invention relates to a casting roll mounted on a twin roll sheet caster.

The present invention is equipped with a pair of casting rolls, an edge dam provided on both sides of the left and right sides and an immersion nozzle for supplying molten steel with a roll summ formed between the casting roll and the edge dam to rotate the casting rolls in the direction of engagement with each other. In a double roll type sheet casting machine for casting, an annular dam contact portion protrudes from both side edges of the casting roll correspondingly to the inner surface of the edge dam, and an effective contact area between the edge dams on the entire contact surface of the dam contact portion. To reduce the heat transfer from the preheated edge dam to the cooled casting roll side is formed by forming a plurality of grooves on the circular cross-section.

According to the present invention, the unevenness formed by the etching process is formed on the side surface of the roll in contact with the edge dam, so that the heat transfer to the roll side cooled from the preheated edge dam before the initial casting molten steel is supplied to the roll sump. By suppressing, the effect of minimizing the formation and attachment of the skull to the edge dam at the beginning of casting is obtained.

Description

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

The present invention relates to a casting roll mounted in a twin roll sheet casting machine, and more particularly, to form an unevenness formed by an etching process on a side surface of the roll in contact with an edge dam, and to supply the initial molten steel to a roll sump. The present invention relates to a casting roll of a twin roll sheet casting machine, which has been improved to minimize heat transfer from the preheated edge dam to the cooled roll side to minimize the formation of the skull on the edge dam at the beginning of casting.

In general, the twin roll sheet caster 100 is a tundish (5) between the pair of casting rolls (1) rotated in different directions and the edge dam (2) mounted on both left and right ends thereof, as shown in FIG. The molten steel is supplied through the immersion nozzle 3 attached to the roll 1 to form a roll sump 4 surrounded by the roll 1 and the edge dam 2, and thus, between the casting rolls 1 rotating in different directions. Pass the molten steel to manufacture the cast directly.

One of the requirements required to ensure the quality of the cast steel in such a thin caster 100 should be the shape of the cast steel edge.

The edge dam 2 is a major facility for sealing the both side portions of the double roll 1 to form a roll sump 4, and when the edge dam 2 is not able to maintain airtightness, the molten steel edges momentarily. If the leaked molten steel continues to rotate while being solidified in contact with the rotating roll 1, the sealing by the edge dam 2 becomes more difficult.

If the leaked molten steel is solidified on the roll, a small gap is continuously formed between the roll 1 and the edge dam 2 to continuously make a pin on the cast iron edge. This leads to a situation in which the casting operation is inevitably stopped, and even when a pin is formed at the edge of the cast, it causes a lot of obstacles in the casting process such as the winding of the cast being impossible.

Therefore, there have been many studies on the edge dam loading method and the material improvement aspect of the edge dam to completely seal between the roll (1) and the edge dam (2), and at present, the casting work of 240 tons or more in a commercial factory is completely sealed. Almost all problems have been solved, at least in terms of airtightness of the edge dams.

Meanwhile, another side of the edge dam 2 related to the quality of the cast steel is related to the skull formed on the inner surface of the edge dam in contact with the molten steel, and sculls are generated and grown in the edge dam 2 and mixed into the cast steel. In this case, excessive roll locality (RSF, Roll Separating Force) is applied in the roll width direction, and the roll gap is momentarily pushed back, which not only causes a change in cast thickness in the casting direction, but also a large amount of mixed skull. May damage the surface of the roll 1 or the edge dam 2 is pushed away from the roll 1, causing a gap between the edge dam 2 and the roll 1, thereby causing molten steel to leak. It can cause casting instability.

The phenomenon that the scull is generated in the edge dam (2) is a temperature difference between the molten steel and the edge dam occurs when the molten steel having a high temperature is in contact with the surface of the relatively low temperature edge dam (2), In the large case, solidification of molten steel occurs in the edge dam 2, which is unavoidable.

In general, the temperature of the edge dam (2) is cast for a long time, when the heat from the molten steel reaches the edge dam (2) sufficiently to reach the thermal equilibrium tends to reduce the occurrence of the skull much, but casting Initially, the skull is more likely to occur because of the large temperature difference.

Therefore, in order to prevent sculling in the edge dam 2, it is essential to maintain the temperature of the edge dam 2 in advance as high as possible, and much effort has been made to this end.

That is, the edge dam 2 is preheated at a temperature such that a skull is not formed even when it is in contact with molten steel through a sufficient heat source supply, but is in contact with the roll 1 at the start of casting. It is known that the preheating effect is significantly reduced.

That is, the preheating operation of the edge dam 2 is preheated in a state in which the edge dam 2 is spaced apart from the roll 1 to maximize the preheating efficiency, thereby securing a high preheating temperature. In this case, the edge dam must be sealed in contact with the roll before the molten steel is injected between the two rolls, and the edge dam 2 preheated to a high temperature is brought into contact with the cold casting roll 1 where the water is cooled. There is a problem that the temperature is rapidly lowered.

That is, as a method for maximizing the preheating of the edge dam 2, it is essential to first secure a preheating means sufficient to raise the temperature above the target temperature of the edge dam 2. 2) An electric heating element (not shown) was placed in the rear portion, and a heating element was generated through a current, and the heat was transferred to the edge dam surface to increase the temperature. In addition, a method of preheating the temperature of the edge dam surface portion to a higher temperature by heating the surface portion of the edge dam 2 directly with an existing gas burner or the like is also widely used.

However, even though the preheating of the edge dam 2 is secured above a desired target temperature through this method, the preheated edge dam 2 eventually comes into contact with the roll in the actual casting state and loses heat in this process. Is inevitable.

FIG. 2 is a plan view showing a state in which the edge dam and the roll are in contact with each other in a conventional twin roll sheet caster, and FIG. 3 is a perspective view showing a casting roll used in a typical twin roll sheet caster, as shown in FIG. By forming a ring-shaped dam contact portion 9 of a predetermined area on both side edges of the casting roll 1 for the purpose of minimizing the rapid decrease of the surface temperature of the edge dam 2 through contact with the roll, Only the dam contact portion 9 was in contact with the edge dam 2.

However, despite the efforts to minimize the contact area between the edge dam 2 and the roll 1 by forming the annular dam contact portion on both sides of the roll, the temperature of the edge dam surface occurring in the contact state once occurs. It did not reach the level to completely eliminate the scull phenomenon at the beginning of casting.

Accordingly, the present invention has been proposed to solve the conventional problems as described above, and an object thereof is to form grooves in the dam contact portions on both sides of the roll in contact with the edge dam, thereby greatly reducing the effective contact area between the edge dam and the roll side. To reduce the amount of heat transfer from the dam to the roll, greatly reduce the amount and frequency of skulls generated at the initial casting edge dams, and to provide casting rolls for twin roll sheet casting machines that can more stabilize the operation of the initial castings with large skulls. do.

As a technical configuration for achieving the above object, the present invention,

A pair of casting rolls, edge dams installed on both left and right sides thereof, and an immersion nozzle for supplying molten steel with roll sums formed between the casting rolls and the edge dams are used to cast cast pieces by rotating the casting rolls in an interlocking direction. In the twin roll sheet casting machine,

The ring-shaped dam contact portion protrudes from both side edges of the casting rolls correspondingly contacting the inner surface of the edge dam, and the effective contact area between the edge dams is reduced on the entire contact surface of the dam contact portion. In order to minimize the heat transfer to the casting roll side by providing a cooling roll of the twin-roll sheet caster, characterized in that the formation of a plurality of grooves on the circular cross-section.

Hereinafter, the present invention will be described in more detail.

Figure 4 is an enlarged perspective view showing the groove formed in the casting roll of the twin roll sheet caster according to the present invention, Figure 5 is a detailed view showing the groove formed in the casting roll of the twin roll sheet casting machine according to the present invention. .

As shown in Figures 4 and 5, the casting roll 10 of the present invention is a roll sump by bringing the roll body and the surface of the casting roll (1) in close contact with each other by the edge dam and the cooling water preheated at a predetermined temperature or more. (4) to minimize the heat transfer from the preheated edge dam (2) to the cooled casting roll (1) at the beginning of casting to form a cast slab, the temperature difference between the edge dam (2) and the casting roll (1) It is to reduce the effective contact area between the casting roll (1) and the edge dam (2) so as to minimize the generation of skull by.

That is, dam contact portions 19 are formed to protrude in an annular shape, respectively, on both side edges of the casting rolls corresponding to the inner surface of the edge dam 2, respectively, and are upper surfaces of the dam contact portions 19. In the entire contact surface, the groove 11 on the circular cross section is formed in the etching process so as to reduce the effective contact area between the edge dams 2 so as to minimize heat transfer from the preheated edge dams 2 to the cooled casting roll 1 side. To form a plurality of compounds.

Here, the reason why the groove 11 is formed in the dam contact portion 19 to minimize heat transfer is that the edge dam 2 and the dam contact portion 19 of the roll 1 come into contact with each other. Is generated and is represented by Equation 1 as follows.

<Equation 1>

Q = htc x (T ₁ -T ₂ ) x A

htc = coefficient of heat transfer between the edge dam surface and the dam contact of the roll (W / m ² K)

T ₁ = edge dam surface layer temperature (K)

T ₂ = roll side temperature (K)

A = area of contact between the edge dam and the roll (m ² )

In order to reduce the heat transfer amount from the edge dam 2 to the casting roll 1 side, as shown in Equation 1, the heat transfer coefficient htc or the temperature difference T ₁ -T ₂ is reduced or the area is reduced. (A) must be reduced.

For each item, first, the biggest influence on the htc value is the contact force (loading force) in which the edge dam 2 contacts the roll, which is simply used for sealing the edge dam 2. ) Is not enough to be placed on the side of roll, and it is necessary to apply external force more than a certain force to the side. Therefore, proper contact force should be given to achieve effective sealing according to the characteristics of each equipment. Accordingly, it cannot be used as a method for reducing heat transfer from the edge dam 2 to the roll 1 side.

In addition, when looking at the surface temperature difference T ₁ -T ₂ between the edge dam 2 and the side of the roll 1, the edge dam 2 corresponds to a temperature preheated by a predetermined temperature or more by a separate preheating means. The temperature of the side surface of the casting roll 1 is made of a material having a good thermal conductivity such as copper, and is cooled by a coolant flowing in the body before casting before contacting the edge dam 2. Since it has a low surface temperature corresponding to the cooling temperature of, the surface temperature difference T ₁ -T ₂ is to be large.

Accordingly, the surface temperature difference may be reduced by only locally increasing the temperature of the side surface of the cooled roll, but this may cause damage and deformation of the roll made of copper material, so that the roll is kept above a certain temperature in terms of facility protection to protect the roll. It is difficult to raise the temperature.

Accordingly, the present invention has been directed to reducing the contact area between the edge dam 2 and the roll 1, wherein in this case, it is possible to unilaterally reduce the contact area itself between the edge dam 2 and the roll 1; ), The contact area itself is maintained and the corresponding dam contact portion 19 has a constant inner diameter (D) and a constant depth (H). The recesses 11 are formed regularly or randomly by an etching process to substantially reduce the effective contact area where the edge dam 2 and the roll 1 come into contact with each other during casting, thereby cooling from the preheated edge dam 2. It is possible to minimize the heat transfer to the roll (1) side to minimize the occurrence of the skull near the edge dam.

That is, forming the groove 11 on the circular cross section through the etching process of forming the groove 11 in the dam contact portion 19 formed in the annular ring on both sides of the casting roll 1 to reduce the effective contact area Most effective at having

At this time, the cross-sectional shape of the groove 11 is preferably formed in a circular or elliptical, the inner diameter (D) size is preferably formed in a 100 ~ 200㎛ based on the circular, which is small if the inner diameter is small This is because the effective contact area between the edge dam 2 and the dam contact portion 19 of the roll is small, so that the amount of heat transfer is small. If the inner diameter is large, molten steel penetration during casting can occur.

On the other hand, the hole area ratio of the groove 11 is preferably as large as possible, but due to the limitation of the etching process for forming this, it is formed to 30 to 60% of the total surface area of the upper surface of the dam contact portion 19. If the hole area ratio of the groove 11 is small, it is preferable that the effective contact area is similar to the surface area of the dam contact portion 19, thereby limiting the amount of heat transfer. If the hole area ratio is too large, the edge is too large. When the friction between the dam 2 and the roll is locally applied, a problem arises in that the inlet of the groove 11 is locally damaged.

Therefore, as shown in Tables 1 and 2, the hole area ratio of the groove 11 is preferably formed to 30 to 60% of the total surface area of the upper surface of the dam contact portion 19.

In addition, even if the depth (H) of the groove 11 is formed to a few μm size, the heat transfer is significantly delayed, but wear of the edge dam 2 is mixed in the groove 11 to delay heat transfer due to friction during casting. Since the effect to be made can be reduced, it is good to form a thing in 50-200 micrometers.

In addition, the inlet corner of the groove 11 has a rounded portion by a secondary etching process so as to reduce abrasion damage caused by friction between the stationary edge dam 2 and the dam contact portion 19 of the rotating roll 1. 12).

Here, the primary etching to form the inner diameter (D) of the groove (11) to 100 to 200 ㎛, the depth (H) of 50 to 200 ㎛ containing a photosensitive liquid on the surface of the dam contact portion 19 on both sides of the target casting roll After coating uniformly to a certain thickness, mask the film with the desired dimple pattern on the whole surface, perform ultraviolet photosensitive work, and if the photoresist is cured selectively, spray the etching solution for a suitable time to selectively corrode the dam contact of the casting roll. The secondary etching to form the round portion 12 in the inlet corner of the groove 11 is that more corrosion occurs at the corners when the etching solution is chemically contacted with the metal surface to be corroded. By using the principle, after removing the cured photoresist remaining in the dam contact portion 19 of the casting roll after the primary etching is completed, the etching solution is sprayed on the dam contact portion 19 for a short time. It is achieved in this way.

<Example>

The cast steel of 3.4 mm thickness is cast using a large twin roll sheet caster 100 having a roll diameter of 1250 mm and a roll width of 1300 mm, wherein the height of the roll sump 4 is 450 mm and the cast steel is STS 304 steel. The casting roll 10 and the groove of the present invention in which the groove 11 is formed in the dam contact portion 19 on both sides of the roll 1 and the round part 12 is formed at the inlet of the groove 11 under such casting conditions. Table 11 and Table 3 show the experimental results obtained by performing the casting operation using the conventional casting roll (1) having no 11).

Correlation between Skew Formation at the Dam Contact Area on Both Sides of Roll and Skull Mixing at Edge Dam during Initial Jog Edge Dam Wear Skull mix during initial casting Conventional If there is no groove normal Quite a lot Invention 30% of hole area of groove normal usually 40% of hole area of groove normal littleness 50% of hole area of groove greatness littleness 60% of hole area of groove Fairly large Very small 70% of hole area of groove Quite large (no casting) Very small Groove diameter: 200 μm, groove depth: 50 μm, round part: none

Correlation between Skew Formation at the Dam Contact Area on Both Sides of Roll and Skull Mixing at Edge Dam during Initial Jog Edge Dam Wear Skull mix during initial casting Conventional If there is no groove normal Quite a lot Invention 30% of hole area of groove normal usually 40% of hole area of groove normal littleness 50% of hole area of groove normal littleness 60% of hole area of groove normal Very small 70% of hole area of groove Slightly larger Very small Groove diameter: 200 µm, groove depth: 50 µm, round part: Yes

Correlation between Skew Formation at the Dam Contact Area on Both Sides of Roll and Skull Mixing at Edge Dam during Initial Jog Edge Dam Wear Initial skull mixing degree Conventional If there is no groove normal Quite a lot The present invention Groove depth 10㎛ normal plenty Groove depth 30㎛ normal usually Groove depth 50㎛ normal littleness Groove depth 60㎛ normal Very small Groove depth 100㎛ normal Very small Groove depth 200㎛ normal Very small Groove diameter: 200㎛, Groove hole area ratio: 60%, Round part: Yes

According to the present invention as described above, a groove is formed in the entire upper surface of the pair of cast roll dam contact portions in contact with the inner surface of the edge dam so as to form a roll sump in which molten steel is stored. By reducing the effective contact area formed between the contact portions, it is possible to minimize heat transfer from the preheated edge dam before casting to the cooled cooling roll side, thereby significantly reducing the amount of scull generation around the edge dam at the beginning of casting. The effect which can manufacture a cast steel is acquired.

While the invention has been shown and described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit or scope of the invention as set forth in the claims below. I would like to clarify that knowledge is easy to know.

1 is a schematic view showing a typical twin roll sheet casting machine,

Figure 2 is a plan view showing a state in which the edge dam and the roll contact before the main tissue in a typical twin roll sheet caster,

3 is a perspective view showing a casting roll employed in a general twin roll sheet caster,

Figure 4 is an enlarged perspective view showing the groove formed on the casting roll of the twin-roll sheet caster according to the present invention,

Figure 5 is a detailed view showing the groove formed in the casting roll of the twin-roll sheet caster according to the present invention.

Explanation of symbols on main parts of drawing

1, 10 ... casting roll 2 ...... edge dam

3 ...... Immersion nozzle 4 ...... Roll sump

9,19 ... Dam contact 11 ..... Groove

12 ..... Round 100 .... Double Roll Laminating Machine

Claims (4)

A pair of casting rolls, edge dams installed on both left and right sides thereof, and an immersion nozzle for supplying molten steel with roll sums formed between the casting rolls and the edge dams are used to cast cast pieces by rotating the casting rolls in an interlocking direction. In the twin roll sheet casting machine, The ring-shaped dam contact portion protrudes from both side edges of the casting rolls correspondingly contacting the inner surface of the edge dam, and the effective contact area between the edge dams is reduced on the entire contact surface of the dam contact portion. A casting roll of a twin roll sheet casting machine, characterized by forming a plurality of grooves on a circular cross section so as to minimize heat transfer to the casting roll side. The method of claim 1, The hole area ratio of the groove is cast roll of the twin-roll sheet caster, characterized in that formed in 30 to 60% of the total surface area of the upper surface of the dam contact. The method of claim 1, The depth of the groove is a casting roll of the twin-roll sheet caster, characterized in that formed in 50 to 200㎛. The method of claim 1, The inlet edge of the groove is a casting roll of the twin-roll sheet caster, characterized in that to form a round portion to reduce the wear damage caused by friction between the stationary edge dam and the rotating contact of the dam.