JP3423353B2 - Roll thickness control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the plate thickness in the rolling direction when hot rolling a metal material such as a copper alloy by a reverse type rolling mill.

[0002]

2. Description of the Related Art When a metal material such as a slab is hot-rolled by using a reverse type rolling mill, the plastic deformation resistance is different between the front end and the rear end of the material, so that the plate thickness is not uniform. ,
Disperses in the rolling direction. Various plate thickness control methods have been conventionally proposed in order to make the plate thickness uniform in the rolling direction. For example, a thickness gauge is installed on the outlet side of the rolling mill to detect the plate thickness immediately after rolling, and to eliminate the deviation between the predetermined reference signal corresponding to the target plate thickness and the detected signal, a roll reduction device or tension control is performed. Feedback control of the device during rolling.

However, in general, a hot rolling mill for copper elongation or the like is not provided with a thickness gauge or an automatic plate thickness control device. In such a case, in the hot-rolled sheet, the distribution of the plasticity coefficient according to the temperature gradient occurs in the rolling direction near the final pass where the temperature drop due to air cooling becomes large. As a result, the plate thickness of the rolled material gradually increases from the front end portion where the air cooling time is relatively short to the rear end portion where the air cooling time is long.

[0004]

In the conventional rolling pass schedule design, the amount of reduction in the final rolling pass is also increased in order to improve the work efficiency. However, since the rolling amount in the final rolling pass is too large, the rolling direction thickness distribution of the hot-rolled strip has a small plasticity coefficient and a large inlet side thickness. A problem occurs that the thickness gradually increases toward the rear end of the thin rolling final pass.

In order to eliminate such variations in strip thickness in the rolling direction, it is conceivable to install an automatic strip thickness control device such as a reduction control device and a tension control device, or a thickness gauge on an existing rolling mill. A large amount of equipment modification is required, and the equipment modification requires high cost.

[0006] The present invention has been made to solve the above problems, and is intended to control the thickness gauge on the delivery side of a rolling mill and the plate thickness control when hot rolling a metal material with a reverse type rolling mill. It is intended to provide a method capable of appropriately controlling the strip thickness in the rolling direction without using an automatic strip thickness control device such as a rolling reduction device or a tension control device.

[0007]

The method for controlling the plate thickness in the rolling direction according to the present invention is a method for controlling the thickness of a material to be rolled in the final pass when hot rolling the material to be rolled by a reverse type rolling mill. The plastic characteristic curve corresponding to the strip thickness and the elastic characteristic line of the rolling mill are also grasped, and the plastic characteristic curve corresponding to the leading end sheet thickness and the plasticity corresponding to the rear end portion thickness of the rolled material are grasped. It is characterized in that the intersection with the characteristic curve is obtained, the roll gap in the unloaded state is obtained from the elastic characteristic line of the rolling mill passing through this intersection, and the roll gap of the final pass is set based on this.

In this case, instead of the plastic characteristic curves corresponding to the front and rear plate thicknesses of the material to be rolled, two approximate straight lines approximate to these are adopted, the intersections of the two are found, and the intersections are determined. You may obtain | require the approximate solution of a roll gap setting value from the elastic characteristic line of the rolling mill which passes.

The plastic characteristic curve is obtained from the relationship between the rolling load and the strip thickness at the leading end and the trailing end of the material to be rolled at that time, when a plurality of materials are rolled with the roll gaps tightened in order. Ask.

[0010]

The procedure for obtaining the roll gap set value from the relationship between the roll gap and the strip thickness on the delivery side of the rolling mill and the rolling load will be described with reference to FIGS. 1 and 7.

First, a simple method using the approximate straight line of the plastic characteristic shown in FIG. 7 will be described. Rolling load at the leading end of the final pass (9 passes) is P _9S , rolling load at the trailing end of the final pass is P _9E , exit side plate thickness at the end of the final pass is h _9S , exit side plate thickness at the end of the last pass is h _Assuming that the exit side plate thickness of the leading end of the pass (8 passes) immediately before the final pass is h _8S and the exit side plate thickness of the trailing end of the pass immediately before the final pass is h _8E , the plasticity coefficient M _{9S of the} leading end of the final pass is _9E .
Both the plasticity coefficient M _9E of the rear end portion and the plasticity coefficient M _9E of the rear end portion can be simply expressed by the following equations (1) and (2).

M _9S = P _9S / (h _8E −h _9S ) ... (1) M _9E = P _9E / (h _8S −h _9E ) ... (2) The above formula (1) corresponds to the straight line C 1 shown in FIG. The above equation (2) represents the inclination of the straight line C2 shown in FIG. 7, and the plasticity coefficient M _9S of the tip portion is set to P _{9S by} using these approximate equations (1) and (2), respectively. , H _8E , h _9S, and the plasticity coefficient M _9E at the rear end is P _9E , h _8S , h _9E
Can be obtained from

Here, each of the _delivery side plate thicknesses h _8S and h _8E can be obtained by using the measured value of the rolling load and the following gauge meter formula (3).

H = S ₀ + (P / K) (3) where h is the exit side plate thickness, S ₀ is the roll gap when there is no load, P is the rolling load, and K is the mill rigidity coefficient.

Further, in the method of the present invention, the following formula (4)
By setting the reduction amount so as to satisfy (5) and (5), it is possible to obtain a hot-rolled sheet having a uniform sheet thickness distribution in the rolling direction.

P ₉ = Δh _9S × M _9S = Δh _9E × M _9E = constant (4) h ₉ = h _8E −Δh _9S = h _8S −Δh _9E = constant (5) However, Δh _9S is the final path. Indicates the amount of reduction at the tip, Δh
_9E represents the amount of reduction at the rear end of the final pass.

Thus, the above equations (4) and (5) are obtained.
Δh _9S and Δh _9E that satisfy the equation are obtained, respectively. Then, the elastic characteristic line A ₀ is determined from the two points on the coordinates obtained from the _delivery side plate thicknesses h _9S and h _9E and the rolling loads P _9S and P _9E , while further two plasticity coefficients (slopes) M _9S , Approximate plastic characteristic lines C1 and C2 passing through the above two points are entered using _M9E , and the intersection point N between them is determined. The rolling load P _{9 of the} final pass is obtained from the intersection point N, and the elastic characteristic line A1 of the rolling mill passing through the intersection point N (the elastic characteristic line parallel to the line A0) is entered. The elastic characteristic line A1 is given by the mill coefficient of the rolling mill. The roll gap setting value S ₁ is obtained from the position where the elastic characteristic line A1 crosses the horizontal axis.

For the plate thickness distribution in the rolling direction of the material on the inlet and outlet sides of the final rolling pass, thickness gauges using X-rays and gamma rays are provided on the inlet side and outlet side of the rolling mill, respectively. The plate thickness may be directly measured, but in a hot rolling mill without a thickness gauge, it can be calculated from the distribution of the rolling load P in the rolling direction using a gauge meter formula (3) or the like.

Next, a formal method using the true curve (exact curve) of the plastic characteristic shown in FIG. 1 will be described.

First, E0, Q0, E1, Q1 shown in the figure
4 points are obtained by the above procedure. Then, after rolling a plurality of ingots in the same process up to the pass immediately before the final pass, rolling is performed by sequentially inserting the roll gap in the final pass, and the rolling load and plate thickness at the leading end and the trailing end at that time Are sequentially measured. Four points E2, Q2, E3 and Q3 are sequentially obtained based on the rolling load and the measured plate thickness. Then, the plastic characteristic curve B1 is obtained by connecting the four points E0, E1, E2, and E3. In addition, 4 of Q0, Q1, Q2, Q3
By connecting the points, a plastic characteristic curve B2 is obtained. Then, the intersection M of the curves B1 and B2 is obtained.

Then, an elastic characteristic line A1 passing through the intersection M is entered. The elastic characteristic line A1 is given by the mill coefficient of the rolling mill. The point where the elastic characteristic line A1 cuts the horizontal axis corresponds to the roll gap setting value S ₁ . The required rolling load at this time is P ₉ . By the way, in the conventional method, since the roll gap setting value S ₀ is determined from the point where the elastic characteristic line A0 crosses the horizontal axis, the rolling load is P _9S , P
_9E , which is significantly larger than the required rolling load P _{9 of the} method of the present invention.

That is, according to the method of the present invention, the strip thickness distribution in the rolling direction of the material on the entry side of the final rolling pass, which occurs in the rolling before the final final pass, and the distribution of the plasticity coefficient of the material during the final pass rolling are mutually The pass schedule can be set to obtain a final pass reduction that offsets.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 2, a reverse type rolling mill 3 is provided in the rolling line 2 so that the slab 8 is hot-rolled. An up coiler 4, a reheating furnace (WFC) 5 and a water cooling zone 6 are provided on the east side of the rolling line 2. Reverse type rolling mill 3 has a work roll diameter of 5
This is a four-stage hot rolling mill with 00 mm, backup roll diameter 1000 mm, roll barrel 1500 mm, and mill rigidity coefficient 300 tonf / mm.

(Example 1) The slab 8 has a thickness of 180 mm,
It is tough pitch copper with a width of 1000 mm and a length of 5500 mm.
Two such slabs 8 are prepared and about 85 in WFC5.
After each reheating to 0 ° C., 9 passes were rolled according to the pass schedule shown in Table 1. One pass schedule is according to the conventional method, and the other pass schedule is according to the method according to the embodiment of the present invention. Both teams performed the same schedule up to the 8th pass, but in the final 9th pass, the roll gap of the latter was made larger than that of the former. The roll gap is shown in FIG.
Was set using. By the way, the roll gap of the 9th pass in the conventional method is 11.0 mm, while that of the 9th pass in the method of the present invention is 17.4 mm.

Table 2 details the pass schedules of the 8th pass and the 9th pass of the conventional method and the method of the present invention. In the former, a difference in plate thickness is seen between the slab front end and the rear end, but in the latter, the plate thickness is substantially equal between the slab front end and the rear end.

As shown in FIG. 3, the odd-numbered paths feed the slab 8 from the east side to the rolling mill 3, and the even-numbered paths feed the slab 8 from the west side to the rolling mill 3. As shown in Table 1 and Table 2, the roll gap setting value and rolling load were changed for each pass.

The case of obtaining the plastic characteristic curve will be described with reference to FIG. Initial plate thickness 1.0mm to 0.7mm
It is assumed that a load of 100 tons is required for rolling in one pass, and a load of 120 tons is required for rolling in an initial plate thickness of 1.0 mm to 0.6 mm. The plasticity coefficient M can be obtained from these results. That is, the plasticity coefficient M can be calculated as (120-100) / (0.7-0.6) = 200 ton / mm. Such a plasticity coefficient M
Corresponds to the gradient of the plastic characteristic curve in the section of the rolled sheet having a thickness of 0.6 to 0.7 mm. In this way, the plastic characteristic curve of the material can be obtained by sequentially obtaining the gradient (plasticity coefficient M) of each section. By the way, the approximate straight line of the plastic characteristic for obtaining the approximate solution described later is the plate thickness 1.0 mm
It is given by a straight line connecting two points of (no load) and a plate thickness of 0.6 mm (load of 120 tons). Plasticity coefficient M in this case
Is 120 / (1.0-0.6) = 300 ton / mm.

FIG. 5 shows the rolling direction of a tough pitch copper sheet rolled by the sheet thickness control method according to the first embodiment of the present invention, with the horizontal axis representing the distance from the end of the last pass rolling and the vertical axis representing the sheet thickness. It is a plate thickness distribution map of.

FIG. 6 is a plate thickness distribution diagram in the rolling direction of a tough pitch copper plate rolled by a conventional method, with the horizontal axis representing the distance from the tip of the final pass rolling and the vertical axis representing the plate thickness.

Both results were obtained by rolling with the pass schedule shown in Tables 1 and 2 above, cooling the slab 8 with water, and then measuring the plate thickness using an ultrasonic thickness gauge. As is clear from FIG. 6, in the case of the conventional method, the thickness gradually increases from the front end to the rear end of the plate by about 0.25 mm. On the other hand, as is apparent from FIG. 5, according to the method of the present invention, it was possible to obtain a substantially uniform thickness from the front end to the rear end of the plate.

In the above embodiment, the case where the tough pitch copper slab is hot-rolled has been described, but the method of the present invention is not limited to this, and can be used for other metal materials such as steel materials and aluminum. You can

FIG. 7 is a graph showing another embodiment in which the roll gap is set by using an approximate straight line for the plastic characteristics of the material to be rolled.

Outgoing plate thickness h _9S (load P _9S ) at the leading end of the final pass and outgoing plate thickness h _{8E at the} trailing end of the pass immediately before the final pass.
An approximate straight line C1 of plastic characteristics is obtained from (no load). Further, a plastic characteristic approximation straight line C2 is obtained from the exit side plate thickness h _9E (load P _9E ) at the rear end of the final pass and the exit side plate thickness h _8S (no load) at the end of the pass immediately before the final pass. And both straight lines C1 and C
Find the intersection point N of 2.

Then, an elastic characteristic line A1 passing through the intersection point N is entered. The elastic characteristic line A1 is given by the mill coefficient of the rolling mill. The point where the elastic characteristic line A1 cuts the horizontal axis corresponds to the roll gap setting value S ₁ . The required rolling load at this time is P ₉ . (By the way, in the conventional method, since the roll gap setting value S ₀ is determined from the point where the elastic characteristic line A ₀ crosses the horizontal axis, the rolling load is P _9S ,
P _9E , which is significantly larger than the required rolling load P _{9 of the} method of the present invention. (Example 2) In the second example, a 65/35 brass slab was hot-rolled using the same four-stage hot rolling mill 3 as in the first example. The slab 8 has a thickness of 180 mm, a width of 750 mm, and a length of 60.
It is a 65/35 brass of 00 mm. Two such slabs 8 were prepared and reheated in the WFC 5 to about 820 ° C., respectively, and then 15 passes were each rolled according to the pass schedule shown in Table 3. One pass schedule is according to the conventional method, and the other pass schedule is according to the method according to the embodiment of the present invention. Both teams performed the same pass schedule until the 14th pass, but in the final 15th pass, the roll gap of the latter was made larger than that of the former. The roll gap was set using FIG. 1 described above. By the way, the roll gap of the 15th pass in the conventional method is 10.5 mm, whereas that of the 15th pass in the method of the present invention is 13.1 mm.

Table 4 shows 14 of the conventional method and the method of the present invention.
It shows in detail the pass schedule of the pass and the 15th pass. In the former, a difference in plate thickness is seen between the slab front end and the rear end, but in the latter, the plate thickness is substantially equal between the slab front end and the rear end.

FIG. 8 is a 65/35 brass sheet rolled by the sheet thickness control method according to the second embodiment of the present invention, in which the horizontal axis represents the distance from the tip of the final pass rolling and the vertical axis represents the sheet thickness. FIG. 3 is a plate thickness distribution diagram in the rolling direction of FIG.

FIG. 9 is a plate thickness distribution diagram in the rolling direction of a 65/35 brass plate rolled by the conventional method, with the horizontal axis representing the distance from the tip of the final pass rolling and the vertical axis representing the plate thickness.

Both results were obtained by rolling with the pass schedule shown in Tables 3 and 4 above, cooling the slab 8 with water, and then measuring the plate thickness using an ultrasonic thickness gauge. As is apparent from FIG. 9, in the case of the conventional method, the thickness gradually increases from the front end to the rear end of the plate by about 0.20 mm. On the other hand, as is apparent from FIG. 8, according to the method of the present invention, it was possible to obtain a substantially uniform thickness from the front end to the rear end of the plate.

[0040]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0041]

According to the present invention, when a metal material is hot-rolled in a plurality of passes using a reverse type rolling mill, the rolling direction plate thickness distribution and the plasticity coefficient distribution of the material on the entry side of the final rolling pass cancel each other out. By setting the amount of reduction in the final pass as described above, hot rolling with a uniform thickness distribution in the rolling direction can be performed without using an automatic thickness control device such as a thickness gauge, reduction control device or tension control device. The board can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing a plastic characteristic curve and an elastic characteristic line of a rolling mill respectively corresponding to the plate thicknesses of the front end portion and the rear end portion of a material to be rolled.

FIG. 2 is a diagram showing an outline of a rolling line of a reverse type rolling mill.

FIG. 3 is a diagram showing front and rear lines of a reverse type rolling mill for explaining a case of rolling a slab.

FIG. 4 is a graph showing an example of a correlation between load and plate thickness.

FIG. 5 is a plate thickness distribution diagram in the rolling direction of a plate rolled by the method of the first embodiment of the present invention.

FIG. 6 is a plate thickness distribution diagram in the rolling direction of a plate rolled by a conventional method.

FIG. 7 is a graph showing straight lines and elastic characteristic lines of a rolling mill that approximate the plastic characteristics corresponding to the plate thicknesses of the front end portion and the rear end portion of the material to be rolled, respectively.

FIG. 8 is a plate thickness distribution diagram in the rolling direction of a plate rolled by the method of the second embodiment of the present invention.

FIG. 9 is a plate thickness distribution diagram in the rolling direction of a plate rolled by a conventional method.

[Explanation of symbols]

3 ... Reverse type rolling mill, 8 ... Slab

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Sasaki 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (56) Reference JP-A-60-238010 (JP, A) JP-A 5-69021 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (2)

(57) [Claims] 1. In a final pass when hot rolling a material to be rolled by a reverse type rolling mill, the plastic characteristic curves corresponding to the plate thicknesses of the leading end portion and the trailing end portion of the rolled material are grasped and the rolling mill is operated. The elastic characteristic line of the rolling material is also grasped, the intersection point of the plastic characteristic curve corresponding to the front end plate thickness of the material to be rolled and the plastic characteristic curve corresponding to the rear end plate thickness is obtained, and the elastic characteristic of the rolling mill passing through this intersection point is determined. A method for controlling the plate thickness in the rolling direction, which comprises determining a roll gap in an unloaded state from a line and setting a roll gap in the final pass based on the obtained roll gap. 2. In the final pass when hot rolling a material to be rolled by a reverse type rolling mill, an approximate straight line that approximates the plastic characteristics corresponding to the plate thicknesses of the leading end portion and the trailing end portion of the rolled material is grasped. While also grasping the elastic characteristic line of the rolling mill, find the intersection of the plastic characteristic approximation line corresponding to the front end plate thickness of the material to be rolled and the plastic characteristic approximation line corresponding to the rear end plate thickness, and find this intersection point. A sheet thickness control method in the rolling direction, which comprises determining a roll gap in an unloaded state from an elastic characteristic line of a passing rolling mill and setting a roll gap in a final pass based on the obtained roll gap.