KR20120110584A - Device for controlling cooling of mold for thin slab and method therefor - Google Patents

Abstract

PURPOSE: A cooling control device and method for a thin slab mold are provided to obtain thin slab with high surface quality by automatically controlling the amount of cooling water supplied to each copper plate according to the inner state of the mold in a continuous casting process. CONSTITUTION: A cooling control device for a thin slab mold comprises a memory(110) and a control unit(160). The memory stores one or more operation parameters among the initial cooling water according to the thickness of a copper plate of a mold(30), the current casting speed, the thickness of the mold, the current cooling water amount, and the intake/drain temperature change of cooling water. The control unit calculates target heat flux according to the casting speed stored in the memory, calculates the current heat flux of each copper plate using the amount of cooling water currently supplied to each copper plate and the intake/drain temperature change of cooling water, and individually controls the amount of cooling water supplied to each copper plate using the difference between the current heat flux and the target heat flux. [Reference numerals] (110) Memory; (140) Input unit; (150) Display unit; (160) Control unit; (170) Cooling water amount adjusting unit; (AA,BB) Cooling water; (CC) Casting speed(From pinch roll)

Description

Cooling control device for thin slab mold and its method {DEVICE FOR CONTROLLING COOLING OF MOLD FOR THIN SLAB AND METHOD THEREFOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cooling control of a mold, and more particularly, to a cooling control apparatus and a method of a mold for a thin slab for appropriately controlling cooling of each copper plate of a thin slab mold in a continuous casting process.

In general, a continuous casting machine is a facility for producing cast steel of a certain size by receiving a molten steel produced in a steelmaking furnace and transferred to a ladle (Tundish) and then supplied to a continuous casting machine mold.

The continuous casting machine includes a ladle for storing molten steel, a playing mold for cooling the tundish and the molten steel discharged from the tundish for the first time to form a casting cast having a predetermined shape, and the casting cast formed in the mold connected to the mold. It includes a plurality of pinch rolls.

The molten steel tapping out of the ladle and the tundish is formed into a cast piece having a predetermined width, thickness and shape in a mold and is transferred through a pinch roll, and the cast piece transferred through the pinch roll is cut by a cutter to obtain a predetermined shape. It has a slab (Slab) or a slab (Bloom), billet (Billet) and the like.

Thin slab produced in the playing process is thin as 50 ~ 100mm in thickness, can be omitted in the rough rolling process in the hot rolling process is mainly applied to the process omission and simplification.

An object of the present invention is to provide a cooling control apparatus and method for a thin slab mold for producing thin slabs of excellent surface quality by automatically adjusting the amount of cooling water of each copper plate according to a phenomenon occurring in a mold in a continuous casting process. To provide.

The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above.

The cooling control apparatus of the mold of the present invention for achieving the above object is at least one of the initial cooling water amount, the current casting speed, the thickness of the mold, the current cooling water amount and the amount of supply / drainage temperature change of the cooling water according to the copper plate thickness of the mold A memory in which operation variable data is stored; And calculating a current heat flux of each copper plate by calculating a target heat flux according to the casting speed stored in the memory, using the current amount of cooling water supplied to each copper plate of the mold and the temperature change of the supply / drainage, and the calculated current heat flux and the target. And a controller for individually controlling the amount of cooling water supplied to each copper plate by using a heat flux deviation between heat fluxes.

Specifically, the cooling control device, the temperature detection means for measuring the temperature of the cooling water supplied to each copper plate of the mold; Quantity measuring means for measuring the amount of cooling water supplied to each copper plate; And a cooling water amount adjusting unit adjusting the amount of cooling water supplied to each copper plate under the control of the control unit, wherein the control unit calculates a temperature change amount between the supply / drainage through the measured temperature of the cooling water, and calculates the calculated temperature. The amount of change and the measured amount of coolant can be stored in the memory.

The controller may compare the calculated heat flux deviation between the current heat flux and the target heat flux with a preset reference value, and increase or decrease the amount of cooling water according to the deviation degree when the heat flux deviation is within the reference value. In addition, when the heat flux deviation exceeds the reference value, the amount of cooling water may be increased or decreased according to the deviation and the casting speed may be changed.

The controller may calculate the current heat flux using at least one operation variable among the contact area of the molten steel in the mold, the amount of cooling water, the specific heat of water, and the amount of temperature change of the cooling water.

The cooling control method of the mold of the present invention for realizing the above object comprises: a first step of detecting the current casting speed of the casting cast, and calculating the target heat flux of the mold according to the casting speed; A second step of measuring the amount of cooling water supplied to each copper plate and the temperature change amount of the cooling water, respectively; A third step of calculating a current heat flux of each copper plate by using the amount of cooling water and the temperature change measured in the above; And a fourth step of individually controlling the amount of cooling water supplied to each copper plate by using the heat flux deviation between the current heat flux and the target heat flux calculated above.

The target heat flux may be calculated differently depending on the cold and slow cooling conditions.

The fourth step may include calculating a heat flux deviation by comparing the calculated current heat flux and the target heat flux of each copper plate; Comparing the calculated heat flux deviation with a preset reference value; And increasing or decreasing the amount of cooling water of the copper plate according to the deviation when the heat flux deviation is within a reference value.

As described above, according to the present invention, by automatically adjusting the amount of cooling water of each copper plate according to the phenomenon occurring in the mold in the continuous casting process, it is possible to manufacture a thin slab of excellent surface quality, to prevent the surface cracks of the thin slab There is an advantage to this.

1 is a conceptual diagram showing a continuous casting machine according to an embodiment of the present invention mainly on the flow of molten steel.
2 is a view showing a thin slab mold and its cooling control apparatus according to an embodiment of the present invention.
3 is a flow chart showing a cooling control process of the mold for thin slab according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like elements in the figures are denoted by the same reference numerals wherever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a conceptual diagram showing a continuous casting machine according to an embodiment of the present invention mainly on the flow of molten steel.

Continuous casting is a casting process in which a molten metal is continuously cast into a bottomless mold while continuously drawing a steel ingot or steel ingot. Continuous casting is used to manufacture simple products such as squares, rectangles, circles, etc., and simple slabs, blooms, and billets.

The continuous casting machine may include a ladle 10 and a tundish 20, a mold 30, secondary cooling bands 60 and 65, a pinch roll 70, and a cutter 90, as shown .

A tundish 20 is a container for receiving molten metal from a ladle 10 and supplying molten metal to a mold 30. Ladle 10 is provided in a pair, alternately receives molten steel to supply to the tundish 20. In the tundish 20, the supply rate of the molten metal flowing into the mold 30 is controlled, the molten metal is distributed to each mold 30, the molten metal is stored, and the slag and the nonmetallic inclusions are separated.

The mold 30 is typically made of water-cooled copper and allows the molten steel to be primary cooled. The mold 30 has a pair of structurally opposed faces open to form a hollow portion for receiving molten steel. In the case of manufacturing a slab, the mold 30 includes a pair of barriers and a pair of end walls connecting the barriers. Here, the short wall has a smaller area than the barrier. The walls of the mold 30, mainly short walls, may be rotated away from or close to each other to have a certain level of taper.

The mold 30 serves to form a strong solidification angle or solidified shell 81 so that the cast steel drawn from the mold maintains a certain shape and a molten metal which is still less solidified does not flow out. Do it. The water-cooled structure includes a method of using a copper pipe, a method of drilling a water cooling groove in the copper block, and a method of assembling a copper pipe having a water cooling groove.

The mold 30 is oscillated to prevent the molten steel from adhering to the wall of the mold, and powder to prevent burning and to reduce friction between the mold 30 and the solidification shell 81 during oscillation. Lubricants such as Powder are used. The powder is added to the molten metal in the mold to become slag, as well as lubrication of the mold 30 and the solidified shell, as well as to prevent oxidation and nitriding of the molten metal in the mold, to keep warm, and to absorb non-metallic inclusions on the surface of the molten metal. do.

The secondary cooling zones 60 and 65 further cool the molten steel primarily cooled in the mold 30. The primary cooled molten steel is directly cooled by the spray means 65 for spraying water while maintaining the solidification angle by the support roll 60 not to be deformed. The solidification of the cast steel is mostly made by the secondary cooling.

The drawing device adopts a multidrive method using a pair of pinch rolls 70 and the like so as to pull out the cast pieces without slipping. The pinch roll 70 pulls the solidified tip of the molten steel in the casting direction, thereby allowing the molten steel passing through the mold 30 to continuously move in the casting direction.

Continuously produced cast pieces are cut to a certain size by a predetermined cutter (not shown).

That is, the molten steel M flows to the tundish 20 in the state accommodated in the ladle 10. For this flow, the ladle 10 is provided with a shroud nozzle 15 extending toward the tundish 20. The shroud nozzle 15 extends to be immersed in the molten steel in the tundish 20 so that the molten steel M is not exposed to air and oxidized and nitrified.

The molten steel M in the tundish 20 flows into the mold by a submerged entry nozzle 25 extending into the mold. The immersion nozzle 25 is disposed in the center of the mold 30 so that the flow of molten steel M discharged from both discharge ports of the immersion nozzle 25 can be symmetrical. The start, discharge speed, and stop of the discharge of the molten steel M through the immersion nozzle 25 are determined by a stopper 21 installed in the tundish 20 corresponding to the immersion nozzle 25. Specifically, the stopper 21 may be vertically moved along the same line as the immersion nozzle 25 to open and close the inlet of the immersion nozzle 25.

The molten steel M in the mold starts to solidify from the part in contact with the wall surface of the mold 30. This is because heat is more likely to be lost by the mold 30 in which the periphery is cooled rather than the center of the molten steel M. By the way that the periphery is first solidified, the back portion along the casting direction of the casting cast piece 80 forms a shape in which the non-solidified molten steel 82 is wrapped in the solidified shell 81.

As the pinch roll 70 pulls the front end portion 83 of the completely cast solid cast steel 80, the unsolidified molten steel 82 moves together with the solidified shell 81 in the casting direction. The uncondensed molten steel 82 is cooled by the spray means 65 for spraying the cooling water in the above movement process. This causes the thickness of the non-solidified molten steel 82 in the playing cast 80 to gradually decrease. When the cast steel 80 reaches a point 85, the cast steel 80 is filled with the solidification shell 81 of the entire thickness. The solidified cast piece 80 is cut to a certain size at the cutting point 91 is divided into slabs (P) such as slabs.

Proper cooling in the mold 30 is important for the surface quality of the slab, and the influence of mold cooling water in the production of thin slabs is greater than that of ordinary slabs.

In general, the amount of cooling water is controlled according to the thickness of the copper plate of the mold 30. As the thickness of the copper plate is reduced, the amount of cooling water is reduced to prevent overcooling. In the case of a thin slab mold, the thicknesses of the long side and the short side are also different, and accordingly, the amount of cooling water supplied to each copper plate also depends on the thickness.

Therefore, in the present invention, by controlling the amount of cooling water supplied to each copper plate of the mold 30 according to the phenomenon occurring in the mold during the continuous casting, it is intended to ensure that the appropriate level of cooling is achieved in each copper plate.

2 is a view showing a thin slab mold and its cooling control apparatus according to an embodiment of the present invention.

First, the copper plate of the mold 30 is composed of a long side and a short side, the thin slab mold 30 is formed with a different thickness of the long side and the short side.

On top of the inside of the mold, a powder layer 51 is formed by powder supplied from a predetermined powder feeder (not shown). The powder layer 51 may include a layer existing in a form in which the powder is supplied and a layer sintered by the heat of the molten steel M (sintered layer is formed closer to the unsolidified molten steel 82). Below the powder layer 51, a slag layer or a liquid fluidized layer 52 formed by melting powder by molten steel M is present. The liquid fluidized bed 52 maintains the temperature of the molten steel M in the mold and blocks the ingress of foreign matter.

On the other hand, the cooling control device includes a memory 110, temperature detecting means 120, quantity measuring means 130, input unit 140, display unit 150, the control unit 160 and the cooling water amount adjusting unit 170 and the like. do.

The memory 110 may include at least one of an initial coolant amount, a current casting speed, a thickness of the mold 30, a current coolant amount, and a supply / drainage temperature change amount of the coolant according to the thickness of the copper plate collected or input from the outside. The above operation variable data is stored.

The temperature detecting unit 120 is installed on the drain line 105 through which the coolant supplied to each copper plate of the mold 30 is discharged to detect the drainage temperature of the coolant. Here, the temperature detecting means 120 may be installed in the water supply line 101 to supply the cooling water to the mold 30, but since the water supply temperature of the cooling water supplied to the mold 30 is almost constant, it may be detected in real time. There is less need and a preset value is available.

Quantity measuring means 130 is installed on the water supply line 101, the cooling water is supplied to each copper plate of the mold 30 to measure the amount of cooling water supplied to each copper plate.

The input unit 140 receives and sets data on various operation variables from the outside.

The display unit 150 displays a GUI screen for inputting various operation variables or a heat flux deviation of each copper plate and the result in a text or graph.

The cooling water adjusting unit 170 is operated according to a predetermined control signal to adjust the amount of cooling water supplied to each copper plate.

The controller 160 calculates the temperature change amount between the supply / drainage through the amount of cooling water measured by the quantity measuring means 130 and the temperature of the cooling water measured by the temperature detecting means 120, and the calculated temperature change amount and the The amount of cooling water is stored in the memory 110, respectively.

In addition, the controller 160 calculates a target heat flux according to the casting speed stored in the memory 110 and then uses the current amount of cooling water supplied to each copper plate of the mold 30 and the temperature change amount of the supply / drainage current of each copper plate. The heat flux is calculated and the amount of cooling water supplied to each copper plate is individually controlled by using the calculated heat flux deviation between the current heat flux and the target heat flux.

Here, the controller 160 compares the calculated heat flux deviation between the current heat flux and the target heat flux with a preset reference value, and increases or decreases the amount of cooling water according to the deviation when the heat flux deviation is within the reference value. If the heat flux deviation exceeds the reference value, the controller 160 increases or decreases the amount of cooling water according to the deviation and changes the operating conditions such as the casting speed. That is, the controller 160 may control the pinch roll 70 to adjust the casting speed of the cast steel 81 discharged from the mold 30 when the heat flux deviation exceeds the reference value.

When calculating the current heat flux, the controller 160 may use at least one operation variable among the contact area of the molten steel in the mold, the amount of cooling water, the specific heat of water, and the temperature change amount of the cooling water, and the heat flux of the mold 30 ( Heat flux can increase linearly as the casting speed increases.

3 is a flowchart illustrating a cooling control process of a mold for a thin slab according to an embodiment of the present invention, with reference to the accompanying drawings.

First, the cooling control device 100 is at least of the initial cooling water amount, the current casting speed, the thickness of the mold 30, the current cooling water amount and the supply / drainage temperature change amount of the cooling water according to the copper plate thickness of the mold 30 to calculate the heat flux One or more operation variable data are collected or received through the input unit 140 and stored in the memory 110 (S11).

Subsequently, the controller 160 detects the current casting speed of the cast piece 81 through the pinch roll 70 and calculates a target heat flux of the mold 30 according to the casting speed (S12 and S13). The target heat flux may be calculated differently according to cold and slow cooling conditions, and the cold and slow cooling conditions may be determined according to the type of steel or mold powder. That is, the target heat flux Qt in the strong cooling condition may be obtained as in Equation 1, and the target heat flux Qt in the mild cooling condition may be obtained as in Equation 2.

Equation 1

Qt = 0.2 × Vc + 1.8

Where Qt is the target heat flux [WM / m ² ] and Vc is the casting speed [m / min].

Equation 2

Qt = 0.35 x Vc + 1.1

In Equation 1, 0.2 may be adjusted to a value between 0.1 and 0.4, and 1.8 may be adjusted to a value between 0 and 3. In Equation 2, 0.35 may be adjusted to a value between 0.3 and 0.5, and 1.1 may be adjusted to a value between 0 and 3.

In the state where the target heat flux is calculated as described above, the controller 160 is installed on the drain line 105 through which the coolant supplied to each copper plate of the mold 30 is discharged using the temperature detecting means 120 to drain the coolant. Measure the temperature, and calculate the temperature change between the supply and drain through the measured cooling water temperature. Here, the temperature detecting unit 120 may be installed in the water supply line 101 to which the cooling water is supplied, as well as the drainage line 105 in which the cooling water is discharged from the mold 30, but the water supply of the cooling water supplied to the mold 30. Since the temperature is nearly constant, there is less need for detection in real time. Accordingly, the controller 160 may measure the drainage temperature in real time and use the preset value of the water supply temperature of the cooling water in the memory 110. In addition, the control unit 160 measures the amount of cooling water supplied to each copper plate of the mold 30 through the quantity measuring means 130 (S14).

As described above, after measuring the amount of cooling water and the temperature change amount of the cooling water supplied to each copper plate of the mold 30, the controller 160 calculates the current heat flux of each copper plate using the measured amount of cooling water and the temperature change amount (S15). ). The current heat flux can be calculated using at least one operating variable of the contact area of the molten steel in the mold, the amount of cooling water, the density of water, the heat capacity of the water and the temperature change of the cooling water. That is, the current heat flux Qp [W / m ² ] may be calculated by Equation 3 below.

Equation 3

Where A is the molten steel contact area in the mold, d is the density of water [kg / l], w is the amount of cooling water [l / min], Cp is the heat capacity of the water, and dt is the temperature change of the cooling water.

The heat flux deviation is calculated by subtracting the current heat flux Qp calculated from the target heat flux Qt and the amount of cooling water supplied to each copper plate using the heat flux deviation is individually controlled through the cooling water amount adjusting unit 170. .

That is, the controller 160 calculates a heat flux deviation by comparing the calculated current heat flux and the target heat flux of each copper plate (S16), and compares the calculated heat flux deviation with a preset reference value (S17). Here, the reference value may be set to ± 10% of the long side of the mold 30 and ± 15% of the short side of the mold 30 based on the target heat flux.

As a result of the comparison, the controller 160 increases or decreases the cooling water amount of the copper plate according to the deviation degree when the heat flux deviation is within the reference value (S18, S19), and when the heat flux deviation exceeds the reference value, the cooling water amount of the copper plate. Increase and decrease according to the degree of deviation and at the same time control the casting speed is changed (S20). For example, the controller 160 increases the amount of cooling water because the current heat flux is less than the target heat flux when the heat flux deviation is within the reference value and is positive. Will reduce the quantity.

In addition, the controller 160 may control to output an alarm signal through a predetermined alarm means when the heat flux deviation exceeds the reference value.

The controller 160 may control the rotation speed of the pinch roll 70 to vary by 0.05 to 0.1 m / min when the casting speed is varied. The sudden change in casting speed is not preferable because the surface cracks of the cast steel 80 can be generated.

As such, when the current heat flux Qp of each mold copper plate deviates from the target heat flux Qt, the controller 160 adjusts the amount of cooling water supplied to each copper plate to return the current heat flux to the target heat flux.

Cooling control of the thin slab mold as described above is not limited to the configuration and operation of the embodiments described above. The above embodiments may be configured such that various modifications may be made by selectively combining all or part of the embodiments.

10: Ladle 20: Tundish
30: mold 51: powder layer
60: support roll 65: spray
70: pinch roll 80: performance cast
81: solidified shell 82: unsolidified molten steel
83: tip 85: solidification completion point
90: cutting machine 91: cutting point
110: memory 120: temperature detection means
130: quantity measuring means 140: input unit
150: display unit 160: control unit
170: cooling water amount control unit

Claims (11)

A memory in which at least one operation variable data among initial cooling water amount, current casting speed, mold thickness, current cooling water amount, and supply / drainage temperature change amount of cooling water according to a copper plate thickness of a mold is stored; And
After calculating the target heat flux according to the casting speed stored in the memory, using the current amount of cooling water supplied to each copper plate of the mold and the temperature change of the supply / drainage, calculate the current heat flux of each copper plate, the calculated current heat flux and target heat flux Cooling control device for a thin slab mold comprising a; control unit for individually controlling the amount of cooling water supplied to each copper plate using the heat flux deviation therebetween.
The method according to claim 1,
Temperature detecting means for measuring the temperature of the cooling water supplied to each copper plate of the mold;
Quantity measuring means for measuring the amount of cooling water supplied to each copper plate; And
Further comprising: a cooling water amount adjusting unit for adjusting the amount of cooling water supplied to each copper plate under the control of the controller,
The control unit calculates the temperature change amount between the supply and drainage through the measured temperature of the coolant, and the cooling control device of the mold for thin slabs for storing the calculated temperature change and the measured amount of cooling water in the memory.
The method according to claim 1,
And the control unit compares the calculated heat flux deviation between the current heat flux and the target heat flux with a preset reference value, and increases or decreases the amount of cooling water according to the deviation when the heat flux deviation is within the reference value.
The method according to claim 1,
The control unit compares the calculated heat flux deviation between the current heat flux and the target heat flux with a preset reference value, and when the heat flux deviation exceeds the reference value, increases and decreases the amount of cooling water according to the deviation, and simultaneously changes the casting speed of the thin slab mold. Cooling control.
The method according to claim 1,
The control unit is a cooling control device for a mold for thin slabs for calculating the current heat flux using at least one operation variable of the contact area of the molten steel in the mold, the amount of cooling water, the specific heat of water, and the temperature change amount of the cooling water.
Detecting a current casting speed of the cast piece and calculating a target heat flux of the mold according to the casting speed;
A second step of measuring the amount of cooling water supplied to each copper plate and the temperature change amount of the cooling water, respectively;
A third step of calculating a current heat flux of each copper plate by using the amount of cooling water and the temperature change measured in the above; And
And a fourth step of individually controlling the amount of cooling water supplied to each copper plate by using the heat flux deviation between the current heat flux and the target heat flux calculated in the above.
The method of claim 6,
The target heat flux is a cooling control method of the mold for thin slabs is calculated differently depending on the cold and slow cooling conditions.
The method of claim 6,
The current heat flux is a cooling control method for a mold for a thin slab is calculated using at least one operation variable of the contact area of the molten steel in the mold, the amount of cooling water, the density of water, the heat capacity of the water and the temperature change of the cooling water.
The method of claim 6,
The fourth step may include calculating a heat flux deviation by comparing the calculated current heat flux and the target heat flux of each copper plate; Comparing the calculated heat flux deviation with a preset reference value; And increasing or decreasing the amount of cooling water of the copper plate according to the deviation when the heat flux deviation is within a reference value.
The method of claim 6,
The fourth step may include calculating a heat flux deviation by comparing the calculated current heat flux and the target heat flux of each copper plate; Comparing the calculated heat flux deviation with a preset reference value; And changing and controlling the casting speed while increasing and decreasing the amount of cooling water of the copper plate according to the deviation when the heat flux deviation exceeds the reference value.
The method of claim 6,
The current heat flux (Qp) is a cooling control method of the mold for thin slabs is calculated by the following equation.
Equation

Where A is the molten steel contact area in the mold, d is the density of water, w is the amount of cooling water present, Cp is the heat capacity of the water, and dt is the temperature change of the cooling water.

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