KR20120075246A - Method and apparatus for roughing mill of thick steel sheet - Google Patents

Abstract

PURPOSE: A method and an apparatus for rough-rolling thick sheets are provided to enable pressure drop and also prevent sheets from being gammed by correcting reduction ratio based on the critical reduction ratio for each thickness after deciding the reduction ratio proper for each thickness. CONSTITUTION: A method for rough-rolling thick sheets is as follows. A reduction ratio{r0(i)} for each pass is decided based on a facility allowable range of a rolling mill(S126). The critical reduction ratio(rc) for each thickness in which jamming sheets can be occurred is decided from the reduction ratio for each pass(S130). In order to obtain a target thickness(Ht), a reduction ratio for distributing the reduction ratio of whole pass is redistributed(S142). Based on the critical reduction ratio for each thickness, the reduction ratio is corrected to prevent the sheets from jamming(S155).

Description

Method and apparatus for rough rolling of thick steel plate that can be stepped down TECHNICAL FIELD

The present invention relates to a rough rolling method and apparatus of a thick steel sheet, and more particularly, to reduce the required rolling properties of the thick steel sheet, that is, high strength, high toughness, thickening and the like, and to improve rolling productivity. The present invention relates to a rough rolling method and apparatus capable of preventing leaf jamming between rolls during rolling when the material is pushed down in a region where a pass is required (hereinafter referred to as a 'quality request pass').

In general, rough rolling of thick steel plate is performed by reversing rolling in the steelmaking process, and the rolling reduction rate and total number of passes for each pass are determined based on the equipment limit value of the rolling mill before processing the rolled material.

Specifically, as shown in Figure 1, the minimum of the loads calculated from the equipment limit value of the rolling mill, that is, the tolerance of the equipment load, the prediction of the tolerance of the equipment torque and the dent limit (tolerance of the amount of rolling reduction that can be inserted into the rolling mill), etc. The load is used to determine the reduction ratio (rolling amount / side thickness) and the total number of passes (the number of passes when the exit thickness of any path becomes smaller than the target thickness) at the thickness of each pass. For example, in Fig. 1, since the exit thickness (end thickness) becomes smaller than the target thickness in 6 passes, the total number of passes becomes 6.

Then, after adjusting the reduction ratio of each pass so that the exit thickness of the final pass becomes the target thickness, the rolled material and the rolling speed are calculated to roll the rolled material. This process is repeated until the final pass after every pass rolling.

On the other hand, in accordance with the recent long-distance economic transport of crude oil or natural gas, changes in the use environment (deep seas, cold cooling) and the enlargement of ships, thick steel plate is required to change the characteristics of high strength, high toughness, thickening furnace. In addition, the coarse grains formed during reheating are refined due to the static recrystallization due to the short interpass time (the time before the rolled material exits the previous pass rolling mill and enter the next pass rolling mill) and the high rolling temperature during the rough rolling. After being finished, it is deformed long in the rolling direction without recrystallization during finish rolling, which results in an increase in dislocation density in the grains.

The higher the dislocation density in the refined grain, the easier the nucleation of the new phase through the phase transformation process due to the strong cooling after the finish rolling, thereby satisfying the final required characteristics.

2 is a graph showing the change of the average grain size according to the reduction ratio when the rolling temperature is changed.

As shown in FIG. 2, when the size of the austenite grain before rolling is 140 μm, the rolling temperature decreases to 90 μm at a high rolling temperature of 1000 ° C. (rough rolling region) at a rolling reduction of 20%, while the rolling temperature is low. It turns out that there is almost no change in 900 degreeC (finishing rolling area | region).

Grain refinement after rough rolling process as above is an essential condition for satisfying the required characteristics of the final thick steel sheet material. For this refinement, minimizing the time between rolling passes during rough rolling and reducing the rolling in the trailing pass region of rough rolling It is necessary to increase the rate. In order to increase the reduction rate of rough rolling, thick plate mills under construction are gradually increasing in size, and the demand for using the reduction ratio close to the facility value of the existing rolling mill is increased by increasing the accuracy of the model that sets the reduction ratio for each pass. There is a situation.

As shown in FIG. 1, the rolling reduction for each pass (or rolling reduction rate) of the rough rolling process is usually determined by the prediction value for the allowable value of the facility torque. Therefore, it is essential to secure the prediction accuracy of the torque model. Therefore, in order to predict the predicted torque close to the measured torque, a torque prediction technique that can consider additional deformations occurring in the rolling region and the vicinity of the rolling region, and consider various material and rolling conditions can be considered.

However, in the case of the rough rolling process or the thick steel sheet, the length of the rolled material is short and the thickness thereof is difficult to secure the reliability of the measurement torque. If the measured torque is larger than the predicted torque, and the value is larger than the allowable value of the equipment torque, plate entanglement where the material is pinched during rolling occurs.

Therefore, in order to remove such plate bleeding and protect the rough rolling equipment, the rolling operator is adjusted to reduce the rolling reduction rate for each pass. However, the number of passes increases due to the adjustment of the reduction ratio for each pass, thus making it difficult to drop down the original quality request pass.

On the other hand, the total number of passes in the rough rolling process means the number of passes when the exit thickness of any pass is smaller than the target thickness of the rough rolling process. Conventionally, in order to secure a target thickness after the total number of passes is determined, a reduction ratio adjustment type reduction ratio redistribution method of modifying the reduction ratio is finally used by multiplying the reduction ratio by each reduction ratio determined from the facility limit.

However, the reduction ratio adjustment coefficient used in the prior art increases the reduction ratio of a pass having a small reduction ratio, and decreases the reduction ratio of a pass having a large reduction ratio, thereby lowering the reduction ratio of a pass requiring the reduction of thick steel sheet. Caused it.

That is, since the slope of the rolling reduction rate for each pass determined from the facility limit value is gradually reduced, the reduction rate in the quality request pass (rear pass), which requires an increase in the reduction rate during the rough rolling process, is lowered. There is a problem in that grain refinement after the rough rolling process for satisfying the required characteristics (high strength, high toughness, thickening) of the thick steel sheet cannot be achieved.

The present invention has been made to solve at least some of the problems of the prior art as described above, and an object of the present invention is to provide a method and apparatus for rough rolling of a thick steel sheet capable of stepping down in the quality request pass during rough rolling of the thick steel sheet. In addition, an object of the present invention is to provide a method and apparatus for rough rolling of a thick steel sheet that can be reduced in the quality request pass while preventing the plate bite.

As one aspect for achieving the above object, the present invention comprises the steps of determining the reduction rate per pass {r ₀ (i)} based on the equipment allowance of the rolling mill; Determining a limit reduction rate (r _c ) for each thickness at which plate bleeding occurs for each thickness from the reduction rates for each pass; Reduction rate redistribution process for distributing the reduction ratio of the entire path to secure the target thickness H _t : and reduction ratio for correcting the reduction ratio so that sheet bleeding does not occur based on the critical reduction ratio r _{c for} each thickness Fertilization process; It provides a rough rolling method of the thick steel plate capable of falling down including a.

Preferably, the process of determining the reduction ratio {r ₀ (i) for each pass may be determined by the following Equation 1 based on the allowable value G _a of the installation torque.

[Equation 1]

Where L _g : Learning coefficient for each path of torque, σ _g : Resistance to path-to-path deformation of thick steel plate during rolling, m: Function related to side wall thickness and thick steel plate composition for each pass, i is path number (1, 2) , 3, ..., N)

Also preferably, the step of determining the critical reduction ratio (r _c ) for each thickness is based on the entrance thickness {H (i)} and the reduction ratio {r ₀ (i)} of each path. It can be set by the polynomial function of thickness {H (i)}.

Preferably, the reduction ratio redistribution process may be configured to increase the reduction ratio slope of the entire rolling pass to have a strong reduction ratio in the quality request pass.

Also, preferably, the reduction ratio redistribution process may reduce the reduction ratio of a pass having a small reduction ratio and increase the reduction ratio of a path having a large reduction ratio based on the reduction ratio for each pass determined in the reduction ratio for each pass. It can be configured to redistribute the reduction ratio.

In this case, the reduction ratio redistribution process may use an exponential function of the thickness ratio η of [Equation 3].

[Equation 3]

Where η (i) = 1-r ₀ (i)

,

,

{Where i (pass number) = 1, 2, 3, ..., N, where H (i) is the entrance thickness, H _f = H (N + 1), H _t is target thickness, H ₀ is rolling starting thickness}

Preferably, in the reduction ratio correcting process, if the following [Formula 6] is not satisfied for the entire rolling pass, the reduction ratio may be corrected through the reduction ratio adjustment coefficient α.

[Equation 6]

At this time, the reduction rate correcting process may be configured to correct the reduction rate by using the following Equation 7 and Equation 8.

[Formula 7]

[Equation 8]

Where the number of passes i = 1, 2, 3, ..., N, H (i) is the entrance thickness, and H _t is the target thickness

On the other hand, the thickness reduction limit determination process for each thickness and the reduction ratio redistribution process may be configured in a different order.

In another aspect, the invention provides an upper and lower work roll; Upper and lower reinforcement rolls supporting the upper and lower work rolls, respectively; Lifting drive for moving the upper work roll up and down; And a control unit configured to adjust the roll gap between the upper and lower work rolls by elevating or lowering the elevating drive unit. The control unit may determine a limit reduction rate for each thickness that the plate bleeding occurs by the thickness from the set reduction rate for each pass based on the equipment allowance of the rolling mill, and redistributes the reduction ratio of the entire pass to secure the target thickness Thereafter, a rough rolling apparatus of a thick steel sheet for setting a roll gap and a rolling speed in each rolling pass is provided by modifying a rolling reduction rate so that plate bleeding does not occur based on the limit reduction rate for each thickness.

Preferably, the control unit may redistribute the reduction ratio in the direction of reducing the reduction ratio of the path having the small reduction ratio and increasing the reduction ratio of the path having the large reduction ratio based on the reduction ratio for each pass set based on the equipment allowance. have.

According to an embodiment of the present invention having such a configuration, the rolling reduction rate for each pass is obtained based on the allowable value of the rolling mill (particularly, the installation torque), and the rolling reduction rate for each thickness is determined therefrom. Therefore, by reducing the reduction rate so that plate bleeding does not occur, it is possible to obtain the effect that the plate bleeding can be prevented.

In addition, according to one aspect of the present invention, it is possible to obtain the effect that the reduction in the quality demand path is possible by reducing the reduction ratio of the pass having the small reduction ratio and increasing the reduction ratio of the pass having the large reduction ratio.

In addition, the present invention, as a aspect, by modifying the reduction rate so that plate bleeding does not occur based on the critical reduction rate for each thickness by setting the step-down rate pattern in the thick steel plate quality request path (high strength, high strength) It is advantageous for securing toughness and thickening), and the effect of improving rolling productivity can be obtained.

In addition, the present invention can implement the prevention of leaf bleeding while setting a high rolling reduction rate for each pass based on (approximately) the tolerance of the rolling mill (particularly, the facility torque), thereby reducing the total number of passes. Can be obtained.

In addition, since the present invention can reduce the number of passes while reducing the number of passes, the time between rolling passes can be minimized, and the effect of grain refinement after the rough rolling process can be obtained.

1 is a conceptual diagram for determining the reduction amount according to the thickness for each pass by the prior art.
2 is a graph showing the change of the average grain size according to the reduction ratio when the rolling temperature is changed.
Figure 3a is a conceptual diagram for determining the amount of reduction according to the thickness of each pass according to an embodiment of the present invention.
Figure 3b is a graph showing the plateable marginal pressure reduction curve for each thickness assumed in accordance with an embodiment of the present invention.
Figure 3c is a graph showing a rolling reduction method according to an embodiment of the present invention.
4 is a flowchart illustrating a rough rolling method of a thick steel plate capable of stepping down according to an embodiment of the present invention.
Figure 5a is a graph showing the difference in the amount of reduction by thickness according to an embodiment of the present invention and the prior art.
Figure 5b is a graph showing the difference between the reduction ratio for each pass according to an embodiment of the present invention and the prior art.
Figure 6 is a schematic diagram showing a rough rolling apparatus of a thick steel sheet capable of step-down according to an embodiment of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Furthermore, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise.

In this specification, the terms "comprise", "comprise", "have" and the like have the features, numbers, steps, operations, components, parts, or a combination thereof described in the specification. It is to be understood that the present disclosure is not intended to exclude, in advance, the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, components, or combinations thereof.

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

The present invention determines the critical reduction rate for each thickness that the plate bleeding occurs by the thickness from the step-down step-down rate set to approach the equipment tolerance (load and torque) of the rolling mill, and to reduce the reduction rate of the quality request path in order to secure the target thickness Distributing the reduction ratio in an increasing direction, and the reduction ratio is modified so that plate bleeding does not occur based on the limit reduction ratio for each thickness.

In order to achieve this technical feature, the thick steel sheet rough rolling method according to an embodiment of the present invention, the step of determining the rolling reduction rate {r ₀ (i)} for each pass based on the equipment allowance of the rolling mill, and the pass-by-pass Determining a critical reduction ratio (r _c ) for each thickness that causes plate bleeding from the reduction ratio; a reduction ratio redistribution process for distributing the reduction ratio of the entire pass to secure a target thickness (H _t ); It may be configured to include a reduction ratio correction process for correcting the reduction ratio so that plate bleeding does not occur based on the critical reduction ratio (r _c ) for each thickness.

First, as shown in FIG. 3A, a step (S120 of FIG. 4) of determining a rolling reduction rate {r ₀ (i) for each pass is performed based on the equipment allowance of the rolling mill.

Specifically, the rolling reduction rate for each pass is calculated in consideration of the equipment allowance of the rolling mill, that is, the tolerance limit, the equipment torque allowance, the equipment load allowance, and the like. In this case, according to an embodiment of the present invention, the step-down ratio for each pass {r ₀ (i)} (i is from 1 to the final N) based on the allowable value of the facility torque or based on a value close to the allowable value of the facility torque. Calculate the pass number).

In order to calculate such a drop-down ratio {r ₀ (i) for each pass, an allowance of the facility torque G _a may be used as shown in Equation 1 below.

[Equation 1]

Where L _g is the learning coefficient for each pass of the torque (value based on the previously performed rolling data), σ _g is the resistance to deformation per pass of the thick steel sheet during rolling (strain strength), and m is the side thickness of each pass. It is a function of {H (i)} and thick steel plate composition. I denotes a pass number (1, 2, 3, ..., N).

Next, a step (S130 of FIG. 4) is performed to determine the limit reduction rate r _{c for} each thickness at which plate bleeding occurs for each thickness from the step-down step-down ratio r ₀ (i). Specifically, as shown in [Equation 2], the critical pressure drop rate (r _c ) curve for each thickness is generated by using the side thicknesses {H (i)} and the step-down rate {r ₀ (i)} of each path. It is defined as a polynomial function of the entrance thickness {H (i)}.

[Equation 2]

In the case of [Formula 2], as a polynomial according to the number of passes, for example, if the total number of passes is 3, it may be expressed as g (H) = a1 * H ² + a2 * H + a3.

This graph through [Equation 2] is shown in Figure 3b.

Next, in order to secure the target thickness H _t , a reduction ratio redistribution process (S140 of FIG. 4) is performed to distribute the reduction ratio of the entire path.

The reduction ratio redistribution process is performed to increase the reduction ratio slope of the entire rolling pass so as to have a strong reduction ratio in the quality demand path (pass required to increase the reduction ratio in the rough rolling process, the latter pass of the rough rolling process). desirable. As the reduction rate slope increases, the reduction rate increases as the number of passes increases, as shown in the graph of FIG. 5B.

In other words, the reduction ratio redistribution process is based on the reduction ratio for each pass determined in the above-described reduction ratio for each pass, thereby reducing the reduction ratio of the front end pass having a small reduction rate and increasing the rear end pass having a large reduction ratio (that is, The redistribution rate is redistributed in the direction of increasing the reduction rate of the quality request path.

That is, in the related art, the reduction ratio of the pass requiring the lowering of the thick steel sheet is lowered by increasing the reduction ratio of a path having a small reduction ratio and decreasing the reduction ratio of a path having a large reduction ratio. In a large quality request pass, adjustment can be made to have a strong reduction ratio, and plate bleeding can be prevented through a reduction ratio correction process described later. Therefore, according to the present invention, it is possible to maintain a high reduction ratio in the quality request path, increase the amount of deformation in the center portion of the plate, and satisfy the required characteristics (high strength, toughness, thickening) of the thick steel sheet. .

This reduction ratio redistribution process may be performed by applying the following [Formula 3] to [Formula 5].

At this time, as disclosed in Equation 3, the reduction ratio redistribution for each pass may use an exponential function of the thickness ratio η defined by '1-reduction ratio {r ₀ (i)}'.

[Equation 3]

[Equation 4]

,

,

[Equation 5]

In the above formula, i (pass number) = 1, 2, 3, ..., N (N is the total number of rolling passes), H (i) is the side thickness, H _f = H (N + 1), H _t is the target thickness, H ₀ means the rolling start thickness, respectively.

Thus, since the rolling reduction rate per path was adjusted using the index of the thickness ratio, the side thickness and the reduction ratio in each rolling pass are reset for each pass.

However, the reduction ratio at this time is simply a value modified in each pass to secure the target thickness without considering whether the torque violates the allowable torque of the facility torque.

Therefore, a reduction ratio correction process (S150 of FIG. 4) is performed to correct the reduction ratio so that plate bleeding does not occur based on the limit reduction ratio r _{c for} each thickness.

To this end, as shown in Equation 6 below, it is necessary to determine whether the redistribution reduction ratio {r (i)} exceeds the critical reduction ratio r _{c for each} thickness.

[Equation 6]

가 되는 경우 판물림이 발생하지 않도록 수정된 압하율을 설정하는 것이 필요하다. If, as shown in Fig. 3c, the distributed reduction ratio exceeds the plate shear generation limit reduction ratio (r _c ), that is,

If it is, it is necessary to set the corrected reduction rate so that plate bleeding does not occur.

To this end, the reduction rate correcting step may include a step of correcting the reduction rate as shown in [Equation 7] by using the reduction rate adjustment coefficient α of [Equation 8].

At this time, the reduction ratio adjustment coefficient α has a value smaller than 1 to reduce the reduction ratio, and is a proportional constant that is multiplied by the reduction ratio determined by the facility torque.

[Formula 7]

[Equation 8]

Here, the number of passes i = 1, 2, 3, ..., N, H (i) is the side thickness, and H _t is the target thickness. [Equation 8] is related to the first pass, H1 means the exit thickness of the first pass. Therefore, in [Equation 8], it should be changed to H ₂ (outside thickness of the second pass) for the second pass, and to H ₃ (outside thickness of the second pass) for the _third pass.

The rough rolling method of the thick steel plate capable of stepping down according to an embodiment of the present invention having such a configuration will be described with reference to a flowchart shown in FIG. 4.

First, initial data for each rolling pass, for example, entry thickness / width / length, radius of the work roll, steel grade group, composition, entrance temperature, rolling mill tolerance (load, torque) are input (S110), and from the first pass The reduction ratio calculation is started (S115).

Based on the initial data, the reduction ratio for each pass is determined (S120).

First, based on the initial data described above, the learning coefficient and the deformation strength of the material stored in the operating computer are calculated (S121), and through this, the reduction ratio of the first pass from the allowable value of the facility torque is calculated by [Equation 1]. (S122).

The exit thickness is calculated from the calculated reduction ratio (S123). If the exit thickness is smaller than the target thickness (S124), the number of passes is increased (S125), and the calculated exit thickness is assumed as the entrance thickness of the next pass. To repeat the steps S121 to S124.

If the exit thickness is larger than the target thickness (S125), the number of passes is set as the total number of passes, and the rolling reduction rate for each pass is determined (S126).

Subsequently, a step (S130) of determining a limit reduction rate (r _c ) for each thickness at which plate bleeding occurs for each thickness is performed from the rate reduction for each pass. This thickness reduction rate determination process for each thickness (S130) may be performed by [Equation 2].

Next, in order to secure the target thickness H _t , a reduction ratio redistribution process (S140) of distributing the reduction ratio of the entire pass is performed. To this end, the thickness ratio index is calculated through [Equation 3] to [Equation 5] (S141), and using the thickness ratio index, redistribution rate and entrance thickness for each pass are redistributed (S142).

In FIG. 4, the reduction ratio redistribution process S140 is performed after the thickness reduction limit determination step S130, but the order of the two processes may be changed.

Next, a reduction ratio correction step (S150) of correcting the reduction ratio so that plate bleeding does not occur based on the limit reduction ratio r _{c for each} thickness is performed. This step is a step of determining whether plate bleeding occurs when the reduction rate is increased so that the reduction can be performed.

The reduction rate correcting step (S150) starts from the first pass (S151), and is the reduction rate {r (i)} corrected in the reduction rate redistribution process smaller than the critical reduction rate per thickness {r _c (i)}? The determination is made (S152), and the number of passes is increased until the end pass (S153) (S154).

If the reduction ratio {r (i)} corrected in the reduction ratio redistribution process is larger than the critical reduction ratio {r _c (i)} for each thickness, the reduction ratio adjustment coefficient (α) of [Equation 8] is used. The reduction ratio is corrected as shown in Equation 7 (S155).

As such, when the reduction can be carried out while the reduction schedule that can prevent the plate bite is determined according to the set the roll gap and the rolling speed (S160), and until the end pass (S180) to perform the rolling (S170).

However, in the step S180 of determining whether it is the end pass, since there may be a difference between the strength of the predicted material before rolling and the actual measured value after rolling, the process returns to the initial stage in order to newly calculate the reduction ratio until the end pass. The same reduction rate determination process can be performed again.

On the other hand, looks at the action of the rough rolling method of the thick steel plate can be step-down according to an embodiment of the present invention having the configuration as described above.

5A is a graph showing the rolling reduction for each pass according to the side thickness when the thick steel plate having a thickness of 300 mm is rolled to a rough rolling end thickness of 78 mm. In the present invention, 7 passes are required for the rolling reduction schedule. In this case, six passes are required, indicating that the number of passes decreases by one pass.

As such, the increase in the number of passes according to the prior art sets the rolling reduction after dispensing in the initial passes where the rolling reduction is relatively small for the rolling in the quality demanding pass, and the rolling reduction by the operator to prevent the plate crushing during rolling. This is because the number of passes has been increased by lowering. However, in the case of the present invention, it is possible to decrease the number of steps and the number of passes since the step of determining whether or not plate bleeding is caused by increasing the amount of reduction (down rate) in the quality request path as opposed to the prior art.

5B is a graph showing the rolling reduction rate (defined as rolling reduction / side thickness) according to the rolling pass, and the average rolling reduction rate in the final three passes at the rear end, which is a quality request path of the thick steel sheet, is 25.3% in the prior art. On the other hand, according to the present invention can be seen that 27.5% higher or equivalent level than the prior art. That is, according to the present invention, it is possible to obtain the effect that the strong rolling is possible in the quality request pass.

Next, with reference to Figure 6, looks at with respect to the rough rolling apparatus of the thick steel plate can be step-down according to an embodiment of the present invention.

The rough rolling apparatus according to an embodiment of the present invention, the upper and lower work rolls 110 and 120, the upper and lower reinforcement rolls 130 and 140 supporting the upper and lower work rolls 110 and 120, respectively, and the upper work roll ( Lifting unit 170 for moving up and down 110, and the control unit 180 to adjust the roll gap (G) between the upper and lower work rolls 110, 120 by raising or lowering the lifting drive 170. .

In this case, the upper work roll 110 and the upper reinforcement roll 130 are supported by the upper roll choke 150, and the lower work roll 120 and the lower reinforcement roll 140 are supported by the lower roll choke 160. do. In addition, the elevating driving unit 170 drives at least one of the upper roll choke 150 and the lower roll choke 160 to change the roll gap G between the upper and lower work rolls 110 and 120.

Then, the control unit determines the limit reduction rate for each thickness that the plate bleeding occurs by the thickness (path limit reduction for each thickness) from the rolling reduction rate for each pass (determination step for determining the reduction rate for each pass (S120)) based on the equipment allowance of the rolling mill Rate determining process (S130)}, after redistributing the reduction ratio of the entire pass to secure the target thickness (pressing rate redistribution process (S140)), the reduction rate so that plate bleeding does not occur based on the limit reduction rate for each thickness By correcting this (rolling-down rate correction process (S150)), the rough rolling apparatus of the thick steel plate which sets the roll gap and rolling speed in each rolling pass (S160) is provided.

Preferably, the controller 180 may reduce the reduction ratio in the direction of reducing the reduction ratio of the path having the small reduction ratio and increasing the reduction ratio of the path having the large reduction ratio based on the reduction ratio for each pass set based on the equipment allowance. Redistribution is possible.

Since the detailed configuration of the controller 180 has been described in detail in the rough rolling method, a detailed description thereof will be omitted.

While the invention has been shown and described with respect to particular embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I want to make it clear.

110 ... upper work roll 120 ... lower work roll
130 ... upper reinforcement roll 140 ... lower reinforcement roll
150 ... upper roll choke 160 ... lower roll choke
170. Lift drive 180 ... Control

Claims (11)

Determining the rolling reduction rate per path {r ₀ (i)} based on the equipment tolerance of the rolling mill;
Determining a limit reduction rate (r _c ) for each thickness at which plate bleeding occurs for each thickness from the reduction rates for each pass;
Reduction rate redistribution process for distributing the reduction ratio of the entire pass to secure the target thickness H _t : and
A reduction ratio correcting step of correcting a reduction ratio such that plate bleeding does not occur based on the limit reduction ratio r _{c for} each thickness;
Rough rolling method of the thick steel plate capable of falling down including a. The method of claim 1,
The step of determining the rolling reduction rate {r ₀ (i)} for each pass is determined by the following [Equation 1] based on the allowable value of the facility torque (G _a ). Rolling method.
[Equation 1]

Where L _g : Learning coefficient for each path of torque, σ _g : Resistance to path-to-path deformation of thick steel plate during rolling, m: Function related to side wall thickness and thick steel plate composition for each pass, i is path number (1, 2) , 3, ..., N) The method of claim 2,
The process of determining the critical reduction rate (r _c ) for each thickness is based on the entrance thickness {H (i)} and the reduction ratio {r ₀ (i)} of each path, and the critical reduction rate curve is measured by the entrance thickness {H ( i)}, the rough rolling method of the thick steel plate capable of stepping down, characterized in that it is set by the polynomial function. The method of claim 1,
The reduction ratio redistribution process is a rough rolling method of the steel sheet capable of falling down, characterized in that to increase the slope of the reduction ratio of the entire rolling pass to have a strong reduction ratio in the quality request pass. The method of claim 1,
The reduction ratio redistribution process reduces the reduction ratio of the pass having the small reduction ratio and increases the reduction ratio of the pass having the large reduction ratio based on the reduction ratio for each pass determined in the reduction ratio determination for each pass. A rough rolling method of a thick steel sheet capable of stepping down redistributing. The method according to claim 4 or 5,
The reduction ratio redistribution step is a rough rolling method of a thick steel sheet capable of stepping down, characterized in that using the exponential function of the thickness ratio (η) of [Equation 3].
[Equation 3]

Where η (i) = 1-r ₀ (i),

,

{Where i (pass number) = 1, 2, 3, ..., N, where H (i) is the entrance thickness, H _f = H (N + 1), H _t is target thickness, H ₀ is rolling starting thickness} The method of claim 3,
The rolling reduction method is a rough rolling method of the steel sheet capable of falling down, characterized in that for reducing the reduction ratio through the reduction ratio adjustment coefficient (α) if the following [Equation 6] for the entire rolling pass.
[Equation 6]

The method of claim 7, wherein
The rolling reduction method is a rough rolling method of a thick steel sheet capable of stepping down, characterized in that to modify the reduction ratio using the following [formula 7] and [formula 8].
[Formula 7]

Equation 8

Where the number of passes i = 1, 2, 3, ..., N, H (i) is the entrance thickness, and H _t is the target thickness The method of claim 1,
The rough rolling method of the thick steel sheet capable of stepping down, wherein the step for determining the critical reduction rate by thickness and the redistribution rate redistribution step can be changed. Upper and lower work rolls;
Upper and lower reinforcement rolls supporting the upper and lower work rolls, respectively;
Lifting drive for moving the upper work roll up and down; And
A control unit for adjusting a roll gap between the upper and lower work rolls by elevating or lowering the elevating drive unit;
Including;
The control unit determines a limit reduction rate for each thickness that the plate bleed occurs by the thickness from the reduction rate for each pass based on the equipment allowance of the rolling mill, redistributing the reduction rate of the entire pass to secure the target thickness, and then the thickness Rough rolling device for thick steel plate that sets the roll gap and rolling speed in each rolling pass by modifying the rolling reduction rate so that plate bleeding does not occur based on the critical reduction rate. The method of claim 10,
The control unit redistributes the reduction ratio in a direction to reduce the reduction ratio of a path having a small reduction ratio and to increase the reduction ratio of a path having a large reduction ratio based on the reduction ratio for each path set based on the equipment allowance. Rough rolling device of thick steel plate.

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