KR100451563B1 - Width rolling method in hot strip reversing mill - Google Patents

Abstract

The present invention is characterized in that in the hot rolling rough rolling process including the blast rolling machine to increase the width of the rolling rolling by synchronizing the horizontal rolling mill and the lateral rolling mill of the exit side, and to determine the crushing load for each pass that can reach the target width of the rough rolling process A method of rolling a width of a reversible hot rolling machine comprising: a first step (21) of determining whether a width variable to be rolled exceeds a normal maximum width variable; A second step (22-25) of setting the number of the width rolling passes and the initial load reduction amount of the horizontal rolling mill exit side; A third step (26-28) of calculating the dogbone width recovery and the rough rolling width in consideration of the next pass total pressure drop; The fourth step (29-33) in which the width of the rough rolling end pass coincides with the target width is used to derive the width reduction load for the width rolling pass at the exit side of the horizontal rolling mill, and the width rolling mill at the entry side, the horizontal rolling mill, and the width rolling mill at the exit side. It is characterized by rolling in synchronization.

Description

Width rolling method of reversible hot rolling mill {WIDTH ROLLING METHOD IN HOT STRIP REVERSING MILL}

The present invention relates to a width rolling method of a reversible hot rolling mill, and more particularly, in a hot rolling rough rolling process including a width rolling mill, to increase the width rolling amount by synchronizing the horizontal rolling mill and the side rolling mill at the exit side, and the target of the rough rolling process. It is related with the width rolling method of the reversible hot rolling mill which determines the width | variety of the rolling reduction per pass which can reach | attain width.

In the general reversible hot rolling process, the rough rolling process includes a slab (1) by the width rolling mill (2, 3) arranged on the inlet and outlet side of the horizontal rolling mill (4), as shown in Figure 1 The hot slab 1 extracted from the heating furnace is rolled several times by the width rolling mills 2 and 3 and the horizontal rolling mill 4, and then rolled into a bar 5 having a target thickness and width. It is a process to do it.

At this time, the width rolling mill may be located on the front, front, or rear of the horizontal rolling mill, Figure 2a shows a rough rolling method having a rolling mill (2) in front of the horizontal mill (4), Figure 2b is a horizontal mill ( The reversible rough rolling method with the width rolling mills 2 and 3 in front and back of 4) is shown.

In general, the reversible hot rolling method of a reversible hot rolling system including a blast rolling machine is a blast rolling → horizontal rolling → horizontal rolling → horizontal rolling → horizontal rolling, as disclosed in Japanese Patents (JP 077752, JP 067098) which have a rolling mill only on its front surface. → Repeated rolling is carried out in the order of horizontal rolling, and in the rough rolling process, which consists of the width rolling mill on the front and rear sides, the rolling process is performed only by the width rolling mill on the front side of the rough rolling mill in the odd pass. The rolling process is performed in the order of width rolling → horizontal rolling → width rolling → horizontal rolling using only the rolling mill on the rear side of the rolling mill.

However, the width rolling method as described above has a problem that it is not possible to increase the width (variable range of the coil width to slab width) because the width of the rolling load is limited depending on the installation conditions.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, width-variable by performing a width rolling method in the crude rolling mill exit side in the width rolling method was carried out only in the reversible hot rolling process including a width rolling mill It is an object of the present invention to provide a method for rolling a reversible hot rolling mill that can increase the range and determine the drop-down amount of the crude rolling mill exit path that reaches the target width of the rough rolling.

1 is a view schematically showing the configuration of a hot rolling rough rolling process,

2A and 2B are views for explaining the outline of a conventional rough rolling process,

3A and 3B are views for explaining an outline of a rough rolling process to which the present invention is applied;

4 is a flowchart showing a conventional method of calculating the load reduction ratio;

5 is a flowchart illustrating a method of determining the explosion pressure according to the present invention.

Explanation of symbols on the main parts of the drawings

1: slab 2, 3: rolling mill

4: horizontal rolling mill 5: bar

In order to achieve the above object, in the present invention, in the reversible hot rolling mill including a width rolling mill, a load reduction amount for the width rolling pass of the horizontal rolling mill is derived, and the width rolling mill of the entry side and the horizontal rolling mill and the width rolling mill of the exit rolling are synchronized with each other. A rough rolling process for rolling in rolling, comprising: a first step (21) for deriving a load reduction amount for a width rolling pass on a horizontal rolling mill exit side to determine whether a width variable to be rolled exceeds a normal maximum variable amount; A second step (22-25) of setting the number of the width rolling passes and the initial load reduction amount of the horizontal rolling mill exit side; A third step (26-28) of calculating the dogbone width recovery and the rough rolling width in consideration of the next pass total pressure drop; It provides a width rolling method of the reversible hot rolling mill, characterized in that the fourth step (29-33) to match the width of the rough rolling end pass and the target width.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments.

3A shows a structure in which the width rolling mill 2 is provided only on the front side of the horizontal rolling mill 4, in the case of the odd pass, the width rolling and the horizontal rolling mill 4 by the width rolling mill 2 on the front side as in the case of rolling by a conventional rolling method. Thickness rolling by), and in the even pass, the thickness rolling is performed by the horizontal rolling mill 4 as in the case of ordinary rolling, and the width rolling by the rolling mill 2 of the front surface is carried out. In the even pass, the slabs that have already been rolled are then rolled again in order of width rolling → horizontal rolling → horizontal rolling → width rolling → width rolling → horizontal rolling .... Let's do it.

Next, in the structure with the width rolling mills 2 and 3 at the front and the rear of the horizontal rolling mill 4 as shown in FIG. 3B, the slab rolled in the rolling mill 3 at the exit of the horizontal rolling mill 4 in the case of the first odd pass. Then, in even pass pass rolling, width-variation is performed by repeating rolling in the order of width rolling → horizontal rolling → width rolling → width rolling → horizontal rolling → width rolling → width rolling ... in accordance with the usual rolling schedule. The horizontal rolling mill (4) exits the width of the horizontal rolling mill (4) as well as the entrance pass, so the roll speed of the horizontal rolling mill (3) rolls is equal to the flow rate of the slab passing through the horizontal mill, that is, the exit velocity of the slab. Must be set in synchronization.

Therefore, the width rolling mill roll speed of the horizontal rolling mill exit side is calculated in consideration of the advance rate as shown in the following equations (1) and (2).

fi = (a1 rHi + a2) + a3

Vsi = (1 + fi) Vri

Where r _Hi is i pass reduction rate, f _i is i pass advance rate, a ₁ , a _2, a ₃ , n is constant, V _ri is i pass rough rolling speed, V _si is The slab flow velocity is shown respectively.

On the other hand, in the case of using the present invention, the width rolling process is also performed in the horizontal rolling mill exit pass, so that the width reduction load of the rough rolling mill exit pass is added to the explosion loading calculated in the conventional rolling milling method to reach the target width in consideration of these effects. Detonation load of horizontal rolling mill exit path should be derived.

The width rolling method proposed in the present invention is used only when the rolling conditions exceed the maximum width-variable variable when the conventional width rolling method is used. As a guideline, it is necessary to repeat the calculation so as to reach the target width by adjusting the pressure drop of the exit pass of the crude rolling mill.

4 is a flowchart showing a conventional method of calculating the load reduction, in connection with this, first, a method of determining the load reduction in normal width rolling will be described below.

First, in the first steps 11 and 12, the number of rolling passes and the load distribution value are determined from the slab condition and the target rough rolling condition, and the width variable to be rolled is expressed by Equation 3 below.

ΔWc = Wo-WT

Where Wo is slab width, W _T is a rough rolling target width, ΔWc means pokga variance respectively.

Then, in the second step (13,14), from the sum of the width change amount and the horizontal rolling width spread for each pass, the load reduction ratio for each pass according to equations (4) to (6) by the load distribution ratio determined in the first steps (11,12). Determine

ΔWHi = {(Hi / Hi-1) CHi-1} WEi

CHi = f (Hi, WEi, LFi, RHi)

In Equations 4 to 6, I _P is the total number of rough rolling passes, H _i-1 is the inlet thickness of the (i-1) pass, H _i is the i pass inlet thickness, η _Ei is the i-pass width rolling mill load distribution, ΔW _Ei Is i pass width reduction, ΔW _Hi is width spread by i pass thickness rolling, C _Hi is width spread coefficient by i pass thickness rolling, and it is a function of entrance slab thickness, width, contact between roll and slab, horizontal roll diameter It is expressed as

Next, as the third step (15, 16), the load reduction amount calculated in the second step (13, 14) is a value that does not take into account the recovery amount of the dogbone generation portion, so these values are added to the equations (7) to (9) Calculate the load capacity by

ΔWDi = CDi

CDi = f (Hi, WEi, ΔWEi)

ΔW * Ei = ΔWEi + ΔWDi

Here, C _Di is the width spreading coefficient by i-pass dogbone rolling, and is expressed as a function of the side thickness, the side width, and the load reduction amount.

Since the method of calculating the load reduction amount as described above uses only the width rolling path at the side of the horizontal rolling mill, in the case of using the present invention, the load reduction amount of the width rolling path at the exit side of the horizontal rolling mill must be derived from a given rolling condition.

Hereinafter, with reference to the flow chart of Figure 5 will be described in detail the method of determining the explosion load in the case of using the present invention.

In the method of determining the load reduction amount shown in FIG. 5, in the first step 21, the present invention can be used only when the width variable ΔW _{C to be} rolled exceeds the maximum width variable ΔW _Cmax when the conventional width rolling method is used. The width rolling pass on the crude rolling exit side proposed in the invention is used.

Next, in the second step 22-25, it is assumed that the _{maximum number} of roll rolling passes I _d and the initial _{drop loading} amount _{ΔW DEi} at the exit side of the maximum _rough rolling mill are taken into account in the amount of bending of the camber and tip during rolling. It should be smaller than the value calculated by the conventional rolling method (ΔW _{Ei +1} ), it is assumed by the equation (10) using the adjustment coefficient (β), the initial step is assumed to be the explosion load adjustment coefficient of 1.0.

_{ΔW DEi} = βΔW _{Ei + 1}

Subsequently, in the third step (26, 27, 28), the next pass total pressure drop (ΔW _{Ei + 1} ) is added to the load reduction amount (ΔW _Ei ) and the exit pressure reduction amount determined by the conventional width rolling method, so that the mathematical It calculates the width of the recovery amount (ΔW _Di) and the rough rolling Ex cheukpok (W _i) a dog as shown in equation 11, and 12.

_{ΔW Ei + 1} = _{ΔW DEi} + _{ΔW Ei + 1}

W _i = W _i-1 + ΔW _Ei + ΔW _Hi + ΔW _Di

Where W _i-1 is the entrance width of the previous pass and W _i is the exit width of the current path.

In the fourth step 29-33, the third step 26-28 is repeatedly calculated until the rough rolling end path is reached, and the difference (α) between the width of the rough rolling end path and the target width is compared. If the value is smaller than 0, adjust it downward using the blast load reduction factor (β ₁ = 0.01). If the value is larger than 1.0, increase the number of i. Repeat the four-step process.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example

Table 3 shows the results of calculating the exit width for each pass in the case of rolling using a conventional rolling method under the rolling equipment conditions of the reversible hot rolling mill as shown in Table 1 and the rolling conditions shown in Table 2, and the pressure reduction proposed by the present invention. Table 4 shows the results of calculating the exit width for each pass of the rolling results using the rolling method.

division Motor capacity (Kw) Roll diameter (mm) Speed (mpm) Speed (mpm) Horizontal rolling mill 12000 1000 274 170 Front Rolling Mill 2240 930 274 170 Rear Rolling Mill 2240 930 274 170

Furnace temperature (℃) Slab thickness (mm) Slab Width (mm) Bar thickness (mm) Bar width (mm) Unit weight (ton) Bar temperature (℃) Carbon amount (% by weight) 1250 230 1250 34 1185 9.47 1050 0.003

Pass No. Front width rolling mill blast load (mm) Horizontal rolling mill thickness rolling capacity (mm) Back Width Rolling Mill Explosion Load (mm) Exit thickness (mm) Exit width (mm) One 49 43 - 187 1236 2 - 41 49 147 1223 3 49 39 - 108 1209 4 - 34 49 75 1196 5 33 21 - 54 1187 6 - 13 21 42 1183 7 13 8 - 34 1185

* Width variable = slab width-rough rolling end width = 1250-1185 = 65 mm

Pass No. Front width rolling mill blast load (mm) Horizontal rolling mill thickness rolling capacity (mm) Back Width Rolling Mill Explosion Load (mm) Exit thickness (mm) Exit width (mm) One 49 43 49 187 1236 2 20 41 49 147 1184 3 49 39 - 108 1149 4 - 34 49 75 1136 5 33 21 - 54 1127 6 - 13 21 42 1123 7 13 8 - 34 1125

* Width variable = slab width-rough rolling end width = 1250-1125 = 125 mm

As shown in the result of the above embodiment, when the width rolling method of the present invention is used, it is possible to increase the width variable compared with the case of using the conventional width rolling method.

Therefore, according to the present invention as described above, by performing the width rolling pass on the exit side of the horizontal rolling mill in the reversible hot rolling process, the width-variable range can be increased, thereby reducing the width constraint of the playing slab and reducing the incidence of tapered slabs. It is effective in increasing performance productivity.

Claims (1)

In the reversible hot rolling mill including a blast rolling machine, a rough rolling process for deriving the width reduction of the width rolling path on the exit side of the horizontal rolling mill and synchronizing the lateral rolling mill in synchronization with the horizontal rolling mill and the outgoing side rolling mill, A first step (21) of deriving a load reduction amount for the width rolling path on the exit side of the horizontal rolling mill to determine whether the width variable to be rolled exceeds the normal maximum width variable; A second step (22-25) of setting the number of the width rolling passes and the initial load reduction amount of the horizontal rolling mill exit side; A third step (26-28) of calculating the dogbone width recovery and the rough rolling width in consideration of the next pass total pressure drop; Width rolling method of the reversible hot rolling mill, characterized in that the fourth step (29-33) to match the width of the rough rolling end pass and the target width.