JP3401429B2 - Plate rolling method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rolling method for producing a plate-shaped metal product by rolling.

[0002]

2. Description of the Related Art A warp that occurs during the rolling of a plate material has a great influence on the productivity of products, such as a reduction in rolling efficiency, an occurrence of equipment accidents, and an increase in a refining process. For example, in the adjusting step, warping needs to be corrected by a leveler, a press, etc., and in an extreme case, the defective portion may have to be cut. Further, when a larger warp occurs, the rolling equipment may be damaged due to the collision of the plates. In this case, the plate itself not only loses its product value, but also causes a great deal of damage such as production suspension and repair of rolling equipment.

Although the mechanism of rolling warpage is not completely understood, it is generally said that the following rolling conditions are the cause.

Diameter difference between upper and lower work rolls Difference in peripheral speed between upper and lower work rolls Difference in friction coefficient between work rolls and rolled material above and below Difference in geometrical deformation resistance (vertical temperature difference, etc.) above and below rolled material Therefore, if all of the above conditions are vertically symmetrical, rolling warpage will not occur, but in the actual manufacture of the plate, any of the conditions will often become vertically asymmetric, resulting in warpage. In particular, it is difficult to make the friction coefficient and temperature symmetrical in the vertical direction, and generally, it is considered that the warpage occurs mainly due to these two causes.

As one of the methods for controlling the warpage caused by the difference between the upper and lower friction coefficients and the difference between the upper and lower temperatures, there is a method of giving a difference in peripheral speed of different work rolls (different peripheral speed ratio) during rolling. It is already known that the relationship between the different peripheral speed rate and the warp is related to the shape ratio Γ (the value obtained by dividing the contact projection arc length of the rolled material and the work roll by the average value of the inlet side and outlet side plate thickness), A method of controlling the rolling warp by using the peripheral speed difference between the upper and lower work rolls (different peripheral speed rolling) after considering the shape ratio Γ is
It is disclosed in JP-A-63-132708.

In Japanese Patent Laid-Open No. 63-132708, based on the pass schedule and the amount of warp of the previous pass observed,
Select the optimum combination of 1 or 2 among the upper and lower work roll rotation speed control (different peripheral speed rolling), the lower work roll pickup amount, the upper and lower impact drop amount, and the upper and lower surface temperature difference of the thick plate. Assuming that the amount of warp of a pass continues to the next pass, a method of giving a control amount that eliminates the amount of warp is shown.

[0007]

[Problems to be Solved by the Invention] JP-A-63-1327
The method disclosed in Japanese Patent Application Laid-Open No. 08-2008 has a shape ratio Γ
In JP-132708, it is described as ld / hm. Here, ld is the contact projection arc length of the rolled material and the work rolls, hm A ₁ is a value obtained by dividing the average value of the thickness at delivery side of the inlet side) is for a given value A _1, A ₂ In the case of <Γ <A ₂ , it is assumed that the effect of warpage control by different peripheral speed rolling is small, and the warp in different peripheral speed rolling occurs only when the shape ratio Γ of each pass is Γ <A ₁ and A ₂ <Γ. When A ₁ <Γ <A ₂ , the warpage is controlled by the difference between the upper and lower temperatures of the plate thickness or the pickup amount.

However, JP-A-63-132708
In the method disclosed in No. 6, when there is no equipment for imparting a vertical temperature difference or equipment for adjusting the pickup amount, that is,
When the lower roll is fixed and the roll gap is adjusted by moving the upper roll up and down, the warp cannot be controlled by the pass schedule of A ₁ <Γ <A ₂ . Also, the predetermined value A
Regarding ₁ and A ₂ as well, there is a drawback that A ₁ and A ₂ cannot be specified because there is no quantitative disclosure and there is no description of a method for obtaining them.

In view of the above points, an object of the present invention is to provide a method for producing a plate-shaped metal product having a small rolling warp only by rolling at different peripheral speeds.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a plate rolling method in which a plate is rolled at different peripheral speeds by a rolling mill equipped with at least upper and lower work roll systems at the same different peripheral speed. A shape ratio Γ _{0 in} which the direction of warpage that occurs when rolling is performed by changing the shape ratio Γ is inverted is previously obtained, and rolling is performed at a shape ratio Γ other than Γ ₀ .

That is, the gist of the present invention is as follows.

In the plate rolling method of rolling a plate material at different peripheral speeds by a rolling mill, the shape ratio Γ _{0 in} which the direction of the warp that occurs when the shape ratio Γ is changed at the same different peripheral speed and is rolled up and down is reversed beforehand. This is a plate rolling method characterized in that rolling is performed with a shape ratio Γ other than Γ ₀ . The shape ratio Γ
Is the value obtained by dividing the contact projection arc length between the rolled material and the work roll by the average value of the inlet and outlet plate thicknesses.

Preferably, the shape ratio Γ is Γ <Γ ₀
Rolling is performed so that −0.1 and Γ ₀ +0.1 <Γ. Further, if necessary, by changing either one or both of the rolling reduction and the work roll radius at the time of rolling, a predetermined shape ratio Γ is set to perform rolling.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of a rolling mill to which the present invention is applied. Roller tables 4 and 4 are provided in front of and behind the rolling mill 7 having the upper and lower work rolls 1 and 2.
The rolled material 3 illustrated on the roller table 4 is
The upper work roll 1 and the lower work roll 2 roll to a predetermined plate thickness. The upper roll system includes an upper work roll 1 and an upper backup roll 5, and the lower roll system includes a lower work roll 2 and a lower backup roll 6.

When the rolling mill shown in FIG. 1 is warped during reverse rolling, as described above, major problems such as interruption of rolling and occurrence of a major accident occur. Different peripheral speed rolling can be considered as a method of controlling the warp, but in order to perform the warp control by the different peripheral speed rolling, it is necessary to sufficiently grasp the warp behavior generated by the different peripheral speed rolling.

Regarding the influence of the different peripheral speed rolling on the warpage, JP-A-63-132708 and JP-A-63-63708.
It is disclosed in Japanese Patent Publication No. 248506, and in the different peripheral speed rolling, even if the same different peripheral speed ratio is set, the warp direction may be reversed. However,
There is no quantitative disclosure in JP-A-63-132708, and even in JP-A-63-248506.
It only shows the results under limited conditions. Therefore, the warp behavior when the rolling conditions change has been completely unknown until now.

Therefore, the inventors have made detailed investigations on the influence of the different peripheral speed rolling on the warp occurrence behavior, and as a result,
It has been found that the shape ratio Γ _{0 in which} the warp direction is inverted up and down shows a constant value as long as the rolling is performed by the same rolling mill even if the speed and the different peripheral speed ratio are changed. The details are given below. The definitions of the different peripheral velocity ratio χ and the warp curvature κ ^* are as shown in Table 1.

[0018]

[Table 1] FIG. 2 shows an example in which the inventors have experimentally investigated the warp behavior that occurs during rolling at different peripheral speeds based on the experimental conditions in Table 2. Figure 2
FIG. 2A shows the warp behavior when the lower work roll is at high speed, and FIG. 2B is the warp behavior when the upper work roll is at high speed. Even if both upper and lower work rolls are at high speed, the absolute value of the different peripheral speed ratio χ is a certain limit value χ
_{When 0} (in this case, χ ₀ = 10%) or less, the warp direction reverses at the shape ratio Γ = 1.8, but when the absolute value of χ reaches a value of χ ₀ or more (for example, 15%). It can be seen that the behavior changes considerably.

[0019]

[Table 2] Therefore, in order to understand the warp occurrence behavior during different peripheral speed rolling in more detail, the inventors have worked roll diameter D, inlet side plate thickness H, material temperature t, roll speed V, different peripheral speed ratio χ, reduction ratio. A rolling experiment was conducted by changing r. In Table 3,
The experimental range is shown. In addition, conditions other than roll peripheral speed,
All were vertically symmetrical.

[0020]

[Table 3] As a result, the absolute value of the different circumferential velocity χ is χ ₀ (in this case, χ ₀ = 11% under condition 1 and χ ₀ = 12% under condition 2).
If the following is satisfied, χ = of FIG.
Similar to the behavior under the conditions of 3 to 10% and -3 to -10%,
It has been found that the warp occurs on the low speed side when the shape ratio is Γ ₀ or less, and the warp occurs on the high speed side when the shape ratio is Γ ₀ or more.

Next, the inventors examined the value of Γ ₀ when the absolute value of the different peripheral velocity ratio χ in Table 3 is χ ₀ or less. The behavior of Γ ₀ is shown in Table 4, and even if the plate thickness, temperature, speed, and different peripheral speed ratio change, the shape ratio Γ _{0 in which} the warp direction is reversed up and down as long as rolling is performed by the same rolling mill has a constant value. You can see that. That is, under the rolling conditions where the shape ratio of the pass is Γ ₀ , warping does not occur even if different peripheral speed rolling is performed, and warp occurs at any different peripheral speed ratio within which the absolute value of the different peripheral speed ratio is within χ _0. Will not be controllable.

[0022]

[Table 4] From the above results, the inventors previously set a constant different peripheral velocity,
If Γ ₀ is obtained by performing experiments with varying shape ratios or model calculations by the finite element method, etc., and then rolling so that Γ ≠ Γ ₀ in any of the passes, the sheet thickness It was found that the warp can be controlled only by rolling at different peripheral speeds even if the temperature, speed, and different peripheral speed ratio within a certain range change. That, | chi | In <chi _0, since warping direction is reversed at the same gamma ₀ at any of the rolling conditions including the chi, by obtaining the gamma ₀ by changing the gamma in certain that once chi, this Γ ₀ is │χ│ <as long as the rolling mills are the same.
It can be used as Γ where the warp is inverted under all conditions including χ ₀ and χ.

Regarding χ ₀ , since χ ₀ ≈10% under a wide range of conditions shown in Tables 2 and 3, it can be considered that χ ₀ ≈10% under general operating conditions. Further, in the case of controlling the normal friction coefficient or the warpage due to the difference between the upper and lower temperatures, it is considered that χ of | χ | <10% is sufficient. Therefore, normally, it is not necessary to obtain the value of χ ₀ . In rare cases, the control capability may be insufficient at | χ | = 10%, but if the control is performed at least at | χ | = 10%, the warpage is significantly reduced. If the warp is still larger than the desired warp, however, χ ₀ under the rolling conditions may be calculated as shown in Table 2 above.

From the above results, in order to control the warpage using different peripheral speed rolling, when rolling from the initial plate thickness H (for example, slab thickness) to the final plate thickness h in multiple passes, the shape of all passes By setting the rolling schedule between the passes so that the ratio Γ is Γ ≠ Γ ₀ , it can be seen that the control by the different peripheral speeds can be effectively performed in all the passes. As shown in the equation (1), the shape ratio Γ is determined only by the entrance side plate thickness, the exit side plate thickness, and the work roll radius.

Shape ratio Γ = contact projection arc length / (average value of entrance side plate thickness and exit side plate thickness) (1) = Ld / hm However, contact projection arc length Ld = [R · Δh {1-Δh /
(4 · R)}] ^0.5 Average value of inlet plate thickness and outlet plate thickness hm = (H + h) / 2 where R: Work roll radius Δh: Reduction amount (= H−h) Therefore, rolling load of each pass By changing one or both of the rolling reduction and the roll diameter of each pass in consideration of the rolling torque, the crown control capability, etc., the predetermined shape ratio Γ in each pass can be determined before the rolling is performed.

The reduction rate can be changed by changing the delivery side plate thickness, and the roll diameter can be changed, for example, by changing the roll radius.
When rolling with a mill having more than the stand, it is possible to change the stand to be rolled according to the pass. Of course, both the rolling reduction and the roll diameter may be changed to set a predetermined Γ.

It is desirable that the shape ratio Γ of the set path schedule has a difference to a certain extent or more from Γ ₀ from the viewpoint of stability of warp control. However, if the difference from Γ ₀ is increased, the constraint on the path schedule becomes stronger. According to the results in Table 4, all Γ ₀ are average values Γ ₀ ±
Since it is included within 0.1, the range is Γ ₀ ± ΔΓ ₀
, The shape ratio Γ is Γ <Γ ₀ −ΔΓ ₀ , Γ ₀ + ΔΓ ₀
It is preferable that <Γ (where ΔΓ ₀ = 0.1).

Further, even if the mill is the same, if the rolling conditions are significantly different (for example, the materials are significantly different), Γ ₀ may also change. In that case, separately, Γ ₀ Just ask for ₀ . After the reduction schedule for each pass is determined, warp control by different peripheral speed rolling may be performed during actual rolling.

Regarding the prediction of the warp curvature and the method of obtaining the different peripheral speed ratio to be applied to eliminate the warp, for example, as disclosed in Japanese Patent Application Laid-Open No. 07-132308, the material is caught. Instantaneous rolling data, for example, using the torque of the upper and lower rolls, load, the upper and lower roll speed,
A method of calculating the vertical temperature difference of the rolled material and the vertical friction coefficient difference between the rolled material and the work roll, predicting the warp curvature based on the results, and calculating the different peripheral speed ratio to be applied may be used. If the warp of each path can be predicted from the past results (for example, table or graph) or the warp of the previous path, the table value or the like is used to predict the warp to eliminate the warp. Only the different peripheral speed ratio to be given is disclosed in
The calculation may be performed by the method disclosed in Japanese Unexamined Patent Publication No. 132308. Furthermore, the rolling condition and the relationship between the different peripheral speed ratio and the warp are obtained in advance by an experiment or the finite element method, and the different peripheral speed ratio to be given is calculated based on the result (eg, tabulation or graphing). May be. Summarizing the above, FIG. 3 shows an example of a flowchart of the control procedure.

In the above description, reverse rolling was used as an example, but it goes without saying that it can be used for tandem rolling if Γ ₀ at each stand is obtained.

[0031]

[Example] Using a rolling mill equipped with a work roll system having a roll radius of 500 mm, a plate thickness of 160 mm and a plate width of 1760 m
The slab of m was rolled to a plate thickness of 20 mm. The heating conditions for the slabs were all the same.

In the first embodiment, first, Γ in this rolling mill is
_In order to check ₀ , rolling was carried out at a different peripheral speed rate χ = 4%. As a result, Γ ₀ = 1.70. Therefore, the warpage control experiment was performed after adjusting the path schedule so that the shape ratio Γ of each path was Γ ≠ Γ ₀ = 1.70.
Under condition 1 (before control), all passes were rolled at the same vertical speed (χ = 0%). The results are shown in Table 5, and in all the passes, the warpage that is estimated to be caused by the difference in the vertical temperature or the difference in the vertical friction coefficient occurred. Under condition 2 (after control), warpage control was performed by different peripheral speed rolling for each pass. Forecasting the amount of warp and calculating the peripheral speed ratio to eliminate the warp
The method disclosed in JP-A-07-132308 described above was used. As a result, the warpage control by the different peripheral speed rolling worked effectively in all the passes, and the warpage became extremely small in any of the passes.

In Example 2, rolling was performed using a two-stand rolling mill. The above-mentioned rolling mill was used for the first stand, and the rolling mill having a roll radius of 600 mm was used for the second stand. As a result of the investigation, in the case of the second stand rolling mill, Γ ₀
Was 1.70. For the purpose of comparison, the rolling reduction of each pass is the same as that of the following comparative example, and the shape ratio Γ of each pass is Γ
1 to 5 passes were reverse-rolled by the first stand rolling mill, and 6 to 9 passes were reverse-rolled by the second stand rolling mill so that ≠ Γ ₀ = 1.70. As in the case of Example 1, under condition 1 (before control), all pass rolling was performed at the same vertical speed (χ = 0%). The results are also shown in Table 5, and in all passes, the warpage that is estimated to be caused by the temperature difference between the upper and lower sides or the difference in the vertical friction coefficient occurred. In condition 2 (after control),
Warp control by different peripheral speed rolling was performed for each pass.
The prediction of the warp amount and the calculation of the different peripheral speed ratio for eliminating the warp were performed by the same method as in the first embodiment. As a result, the warpage control by the different peripheral speed rolling worked effectively in all the passes, and the warpage was extremely small in any of the passes.

On the other hand, also in the comparative example, rolling was performed in the same mill as in Example 1 in 9 passes. The pass schedule was set without considering the shape ratio. Condition 1 (Before control: Same circumferential speed above and below
(χ = 0%), as shown in Table 5, warp occurred in all passes. Under condition 2 (after control: different peripheral speed, χ ≠ 0%), warp control by different peripheral speed rolling was performed for each pass as in the example. However, Γ≈Γ ₀ = 1.70
In the 6th pass and the 7th pass which became, it became impossible to control.
The calculated values were −175.2% and 106.6%, but rolling at such a large different peripheral speed ratio was actually impossible. Furthermore, as a confirmation experiment, χ = ± 20, ±
Rolling was attempted at different peripheral speed ratios of 15, ± 10, ± 5, ± 3%, but there was no control effect, and in any case, as shown in Note 4) and Note 5) of Table 5, The warp curvature was the same as that of the case without.

[0035]

[Table 5]

[0036]

As described above, according to the present invention, since it is possible to easily manufacture a plate without warpage, there is an effect that a plate-shaped metal product having an excellent shape can be efficiently produced.

[0037]

[Brief description of drawings]

[0038]

FIG. 1 is a diagram showing an example of a rolling mill to which the present invention is applied.

[0039]

FIG. 2 is a diagram showing a relationship between a shape ratio and a warp direction in different peripheral speed rolling.

[0040]

FIG. 3 is a diagram showing an example of a flowchart of a control procedure of the present invention.

[0041]

[Explanation of symbols]

1 Top work roll 2 Lower work roll 3 Rolled material 4 roller table 5 Top backup roll 6 Lower backup roll

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-11-47812 (JP, A) JP-A-9-206810 (JP, A) JP-A-9-271819 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B21B 37/00-37/78 B21B 1/00-1/26

Claims (3)

(57) [Claims] 1. A plate rolling method in which a plate material is rolled at different peripheral speeds by a rolling mill having at least upper and lower work roll systems, which causes warpage that occurs when the shape ratio Γ is changed at the same different peripheral speed ratio. A plate rolling method characterized in that a shape ratio Γ _{0 in} which directions are reversed upside down is obtained in advance, and rolling is performed at a shape ratio Γ other than Γ ₀ . The shape ratio Γ is a value obtained by dividing the contact projection arc length between the rolled material and the work roll by the average value of the inlet and outlet plate thicknesses. 2. The shape ratio Γ is Γ <Γ ₀ −0.1, Γ ₀ +
The plate rolling method according to claim 1, wherein rolling is performed so that 0.1 <Γ. 3. The plate according to claim 1, wherein a predetermined shape ratio Γ is set by changing one or both of a rolling reduction and a work roll radius at the time of rolling. Rolling method.