KR100770336B1 - Method for shortening time of arrival of heat balance in twin roll strip casting process - Google Patents

Abstract

A method for shortening a thermal equilibrium arrival time in a twin roll strip casting process is provided to reduce up to 50% of heat expansion stabilization time of a steel arbor by heating the steel arbor up to a normal casting temperature before casting. A method for shortening a thermal equilibrium arrival time in a twin roll strip casting process includes the steps of: increasing a temperature of a steel arbor(120) up to 30°C+(DeltaT°C/2) by supplying casting roll(100) with cooling water which is warmer than the cooling water supplied during casting. The cooling water supplied during a predetermined time before the casting; and supplying the cooling water in a normal temperature of 30°C during the casting for shortening the thermal equilibrium arrival time.

Description

Method for shortening time of arrival of heat balance in twin roll strip casting process

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

Figure 2 is a schematic diagram showing the casting roll cooling structure and the cooling water temperature before casting in the conventional twin-roll thin plate manufacturing process,

Figure 3 is a schematic diagram showing the casting roll cooling structure and the cooling water temperature during casting in the conventional twin-roll thin plate manufacturing process,

Figure 4 is a schematic diagram showing a casting roll cooling structure and the cooling water temperature before casting in a twin roll thin plate casting process according to the present invention.

<Description of Symbols for Main Parts of Drawings>

100: casting roll 400: molten steel

110: copper sleeve 120: steel arbor

130: casting roll cooling water center hole 131: casting roll cooling water vertical distribution hole

132: casting roll cooling water inclined distribution hole 133: casting roll surface portion upper cooling water hole

140: casting roll inlet cooling water temperature according to the prior art

141: casting roll exit coolant temperature before casting according to the prior art

142: casting roll exit coolant temperature during casting according to the prior art

145: cooling water supply temperature before casting according to the present invention

146: casting roll exit coolant temperature before casting according to the present invention

The present invention relates to a method of shortening the thermal equilibrium time to reach the casting roll in a twin-roll thin plate casting process, and more particularly, to supply the cooling water supplied to the casting roll for a predetermined time before casting to be higher than the cooling water temperature supplied during the normal casting. By raising the temperature of the steel arbor and supplying the cooling water temperature to the normal temperature immediately before casting, it is possible to reduce the thermal expansion normalization time of the steel arbor during casting by about half. Casting in the double roll sheet metal casting process, which can contribute to the uniformity of cast steel, which is one of the important factors of cast steel quality, and ensure early casting stability, such as stabilization of hot rolling conditions, and increase the error rate of the cast steel. A method for shortening the thermal equilibrium arrival time of a roll.

In general, in the casting method of thin plate, a continuous casting method of manufacturing slab by continuous casting method through molten steel through tundish and rolling and finishing it into a thin plate, and a pool of molten steel directly injected between a rotating twin roll and an edge dam There is a twin-roll thin plate casting method for manufacturing a thin plate directly without rolling and finishing the slab as a casting roll. The twin roll thin plate casting method can directly manufacture a thin plate without going through various processes of continuous casting method and at the cost side. Significant cost savings are possible and the process can be reduced, so intensive research is underway.

1, there is shown a schematic diagram of a typical twin roll sheet caster.

As shown, between the two casting rolls 100 rotating at a constant speed through the immersion nozzle 300 installed to the lower side of the tundish 200, the molten steel 400 is supplied to the casting roll 100 and both sides The molten steel 400 supplied through the molten steel pool formed by the edge dam 500 of the cast roll 100 while forming the solidification shell in contact with the casting roll 100, the cast slab 450 at the closest point of the roll as the casting roll 100 rotates. ) Is to cast. The cast slab passes through the atmosphere maintaining chamber 600 installed under the casting roll while forming a loop and is hot rolled in the rolling mill 700 to be wound up in the coiler 800.

In this case, the molten steel formed between the two casting rolls is covered with a meniscus shield 900 to prevent reoxidation of the molten steel, and the casting roll 100 is important because the clean state of the casting roll 100 is important to stabilize the quality of the cast steel. A casting roll cleaning brush roll 101 is used around.

The twin roll sheet metal fabrication process has secured a good quality cast steel production process for carbon steel and stainless steel grades, and a commercial plant has already been built and operated.In order to secure the economic feasibility of the process, many efforts are made to improve the quality, error rate, and stabilize operations. ought.

In the twin-roll thin plate manufacturing process, the thickness of the cast slab is usually 0.8-6.0 mm, and the shape of the cast steel is closely related to the shape of the roll in the roll nip. In casting, the shape of the casting roll 100 is the thermal expansion of the casting roll. Depends on.

The casting roll 100 expands due to the amount of heat taken away while solidifying molten steel during casting. Since the amount of heat per unit area of the casting roll absorbed from the molten steel is larger than that of the conventional continuous casting and mini mill processes, the molten steel of the casting roll 100 The material in contact with 400) generally uses copper or copper alloy having good thermal conductivity, and the inside of the casting roll uses iron alloy due to securing rigidity and reducing manufacturing cost.

2, there is shown a schematic diagram of a casting roll cooling structure and a pre-cast cooling water temperature in a conventional twin roll type sheet manufacturing process.

Casting roll 100 is composed of a copper sleeve (110; sleeve) and a steel arbor (120; arbor), the cooling water is supplied to the casting roll cooling water center hole 130 from one side of the casting roll, and then the casting roll cooling water vertical distribution hole 131 and the casting roll cooling water inclined distribution hole 132 flows to the upper surface of the cooling water hole 133, which is responsible for cooling the casting roll, absorbs the amount of heat introduced into the casting roll surface, and then again the opposite side of the casting roll in the longitudinal direction. The casting roll coolant is distributed through the inclined distribution hole 132, the casting roll cooling water vertical distribution hole 131, the casting roll cooling water central hole 130.

Since the cooling water is not supplied with heat before casting, a temperature difference between the casting roll inlet coolant temperature 140 and the casting roll exit casting coolant temperature 141 does not occur.

3, there is shown a schematic diagram of a casting roll cooling structure and a cooling water temperature during casting in a conventional twin roll sheet metal manufacturing process.

Unlike casting, during casting, the casting roll entrance coolant temperature 140 absorbs heat as it passes through the casting roll surface, and the casting roll exit coolant temperature 142 during the casting exits the casting roll while being raised relative to the entrance cooling water temperature. Come out. This is expressed as follows.

T2 = T1 + ΔT

T1 = incoming coolant temperature

ΔT = coolant temperature rise during casting

T2 = exit coolant temperature

Therefore, since the cooling water is not supplied with heat before casting, ΔT becomes 0 ° C., so that the temperature of the entire casting roll is maintained at T1. However, as casting starts, ΔT rises and ΔT remains constant when thermal equilibrium at the casting roll surface is reached. In general, since copper or copper alloy has good heat transfer, the equilibrium of ΔT is reached within a few minutes after the start of casting. However, inside the casting roll, the temperature of the cooling water at the inlet and the outlet during the casting is different, and in particular, the rising of the cooling water temperature 142 increases the steel arbor 120 temperature. Since the steel arbor has a lower thermal conductivity than copper, it takes a long time for the steel arbor to reach the thermal equilibrium. Ultimately, the equilibrium state of the slab shape is achieved only when the thermal equilibrium reaches the steel arbor.

Under these casting conditions, the expansion of the casting roll lasts for a long time, so that the crown of the cast steel, which is directly affected by the roll shape change due to thermal expansion, continuously changes, resulting in control problems such as the continuous use of the rolling mill 700. As a result, the shape quality of the wound cast is degraded.

The thermal expansion phenomenon of the casting roll 100 is sensitive to temperature, for example, in the case where the cooling water traveling direction is one direction as shown in FIG. 3, the expansion of both ends of the roll is asymmetrical due to the difference between the temperature of the cooling water inlet and outlet. Done.

Utility Model 1998-0038078, 1999-0026813 and the like have alleviated the asymmetric thermal expansion phenomenon of the roll through the differential cooling ability inside the cooling water hole of the roll surface to solve the problems caused by the one-way cooling water flow.

The present invention is to overcome the above-mentioned conventional problems, an object of the present invention is to increase the temperature of the cast roll steel arbor for a long time by the rise of the temperature of the cooling water discharged into the casting roll during casting and thus the overall roll Provides a method for shortening the thermal equilibrium time of casting rolls in a twin roll sheet metal casting process to solve the problem that the thermal expansion takes a long time to reach an equilibrium and consequently takes a long time to stabilize the crown shape of the cast slab. It is.

The present invention relates to a method of shortening the thermal equilibrium time to reach the casting roll 100 in a twin-roll thin plate casting process in consideration of the temperature increase amount (ΔT ℃) until the casting roll reaches the thermal equilibrium in the 30 ° C before casting. After adjusting to a value of (ΔT ° C./2) and supplying for 30 minutes to 1 hour, the temperature of the cast roll steel arbor 120 is increased, and then, 30 seconds to 1 minute is supplied to 30 ° C. immediately before casting.

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

4, there is shown a schematic diagram of the casting roll cooling structure and the cooling water temperature before casting in a twin roll thin plate casting process according to the present invention.

The casting roll 100 is composed of a steel arbor 120 forming an axis and a copper sleeve 110 formed on an outer circumferential surface of the steel arbor, and a coolant center hole 130 is formed on the shaft of the steel arbor 120. The center part is formed in the casting roll length direction. The coolant vertical distribution hole 131 communicates with the coolant center hole 130 and is formed in the casting roll outer circumferential direction at the center of the steel arbor 120 shaft and communicates with the coolant gradient distribution hole 132. The coolant inclined distribution hole 132 communicates with the upper coolant hole 133 formed in the copper sleeve 110 in the casting roll length direction. The upper coolant hole 133 extends to the opposite side of the casting roll length direction, and then again coolant is inclined. It communicates with the distribution hole 132.

The cooling water is supplied from the casting roll cooling water center hole 130 from one side of the casting roll, and then is formed on the upper surface of the roll surface responsible for cooling the casting roll through the casting roll cooling water vertical distribution hole 131 and the casting roll cooling water inclined distribution hole 132. After absorbing the heat flowed into the coolant hole 133 and absorbing the amount of heat introduced into the casting roll surface, the casting roll coolant inclined distribution hole 132 opposite the casting roll length direction, the casting roll coolant vertical distribution hole 131, and the casting roll coolant center hole Exit through 130.

The coolant supply temperature 145 before casting of the present invention is a value obtained by adding half the temperature rise (at 30 ° C) and the temperature rise amount before casting start. If the cooling water temperature rise amount during casting is 20 ° C, about 30 minutes to 1 hour before casting The feed is adjusted to 30 ° C. + 20/2 = 40 ° C. for a time of. The increase in the cooling water temperature may be various methods such as installing a temperature raising device such as a heater in the casting roll cooling water supply device or using a calorific value generated by the pump circulation.

From about 30 seconds to 1 minute before the casting is started, the heat exchanger installed in the casting roll cooling water supply system is operated to lower the casting roll cooling water supply temperature back to 30 ° C. and supply it to the casting roll 100. Therefore, the casting cooling water supply temperature during the casting is 30 ℃ and the casting roll exit cooling water temperature is 50 ℃ to proceed with the casting.

In this case, due to the effect of cooling water temperature supplied at 40 ° C before casting, the inlet cooling water side of the casting roll continuously changes during the time when 40 ° C is changed back to 30 ° C in the case of steel arbor, and the exit cooling water side of the casting roll before casting is Thermal expansion changes during the time that 40 ° C. changes back to 50 ° C. Therefore, in the case of the cast roll steel arbor, the time to reach the thermal equilibrium will be as long as the temperature changes by 10 ℃.

On the other hand, in the case of using the conventional cooling water supply method, 30 ° C. is 30 ° C. in the case of the cooling water inlet side, but there is no change, but the thermal arbor portion of the cooling water exit side is changed from 30 ° C. to 50 ° C. in the end of the present invention. It is possible to cut the time to reach thermal equilibrium by half through the effect of.

When the present invention and the conventional cooling water supply method is shown in a table as follows.

Cooling water inlet / outlet temperature before casting Cooling water inlet / outlet temperature before main tissue Cooling water inlet / outlet temperature during casting Conventional Cooling Water Supply Method 30 ℃ / 30 ℃ 30 ℃ / 30 ℃ 30 ℃ / 50 ℃ Cooling water supply method of the present invention 40 ℃ / 40 ℃ 30 ℃ / 30 ℃ 30 ℃ / 50 ℃

<Example>

Hereinafter, the effects of the present invention will be described through Examples.

The casting roll 100 has a diameter of 1250 mm, a roll width of 1300 mm, and a sleeve 110 having a copper alloy and a roll surface of nickel plated with a thickness of 1 to 2 mm. mm, and the casting speed is 132 m / min, cast steel grade is STS 304 and the cooling water inlet / out temperature difference per roll during casting is 20 ℃.

In order to confirm the effect of the present invention, the following Table 2 shows a comparison with the conventional casting method when the cooling water temperature is increased in advance before casting and supplied to the casting roll.

Crown amount per casting roll before casting Cast crown amount after 5 minutes of casting Cast crown amount after 15 minutes of casting Cast crown amount after 30 minutes of casting Casting Roll Thermal Equilibrium Time Example 230 ㎛ 100 μm 80㎛ 80㎛ 15 minutes Comparative example 230 ㎛ 140 μm 110 ㎛ 80㎛ 30 minutes

As shown in Table 2, in the case of using the conventional casting termination method, the heat balance of the complete casting roll is reached after about 30 minutes, but in the case of applying the cooling water supply method of the present invention, the casting roll is about 15 minutes after casting. It can be seen that the thermal equilibrium has been reached, and the cast crown has a good effect as the crown of the casting material is normalized quickly.

As described above, in the twin roll type sheet casting process according to the present invention, the method for shortening the thermal equilibrium arrival time of the casting roll can raise the temperature of the steel arbor with the low heat transfer during the casting roll to near the normal state during casting before casting. Therefore, it is possible to reduce the thermal expansion normalization time of the steel arbor by about half, so that the shape of the cast can reach equilibrium during casting, which contributes to the uniformity of cast profile, which is one of the important factors of cast quality. In addition, there is an excellent effect that can secure early casting stability, such as stabilization of hot rolling conditions, and increase the error rate of the wound cast.

Claims (3)

delete During twin roll type sheet casting, the cooling water supplied to the casting roll 100 for a predetermined time before casting is supplied higher than the cooling water temperature supplied during normal casting to increase the temperature of the casting roll steel arbor 120, and then the cooling water temperature is immediately before casting. What is claimed is: 1. A method for reducing the time to reach thermal equilibrium of a casting roll by casting in a form of feeding at a low temperature at a normal temperature; The temperature of the cooling water is adjusted to a value of 30 ° C. + (ΔT ° C./2) before casting in consideration of the temperature increase amount (ΔT ° C.) until the casting roll reaches the thermal equilibrium, and is supplied at 30 ° C. immediately before casting. Shortening method of reaching the thermal equilibrium time of the casting roll in the twin roll sheet metal casting process, characterized in that. The method of claim 2, The predetermined time before casting is 30 minutes to 1 hour before casting, the time immediately before casting is 30 seconds to 1 minutes, the method of shortening the thermal equilibrium time of reaching the casting roll in the twin-roll thin plate casting process.

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