JPH0659488B2 - Initial setting method for continuous hole rolling - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an initial setting method for hole type continuous rolling, and in particular,
A substantially fixed rolling machine suitable for use in continuous rolling of billets, bar steel or wire rods having a square or round cross section by combining a plurality of stands such as horizontal rolls and vertical rolls having different rolling directions. Holes that determine the fine adjustment amount of the reduction distribution and the mill operation amount in order to absorb the dimensional change caused by the change of rolling conditions for each strip and obtain the strip with the target dimension under the reduction distribution among the strips. The present invention relates to an improvement in the initial setting method for continuous die rolling.

[Prior art]

For strips such as billets, steel bars or wire rods whose cross-sectional shape is square or round, generally, the rolled material is sequentially rolled in different rolling directions by a hole-type continuous rolling mill in which multiple stands with different rolling directions are alternately combined. The cross-sectional area of the rolled material is reduced, and the rolled material is gradually stretched to have a predetermined size and shape. An example of the hole-type continuous rolling mill is, for example, the first
As shown in FIG. 2, four stands (V stand, H2 stand, V3 stand from the upstream side) are alternately arranged with a stand having a vertical roll 12 (hereinafter referred to as V stand) and a stand having a horizontal roll 14 (hereinafter referred to as H stand). , H4
A combination of stands) is used. In the figure,
10 is a rolled material. The rolled material may be rotated 90 ° between the stands in the same rolling direction by the twister. When rolling a strip using such a hole-type continuous rolling mill,
Depending on the material-side disturbance such as the temperature and composition of the rolled material, and the equipment-side disturbance such as roll diameter change and hole type wear, the optimum value of the reduction amount at each stand can be set for each material in a short time. It is a difficult task to set the roll opening degree based on the above judgment, and to set the roll rotation speed optimally according to the reduction amount so that tension is not generated during rolling. Therefore, at present, it is attempted to set the rolling conditions using a computer. Normally, in continuous rolling of strips with square and round cross sections, the rolling direction of the material changes by 90 ° for each stand, but it corresponds to the height direction (vertical direction) corresponding to the rolling direction and the direction orthogonal to the rolling direction. It is necessary to roll to a predetermined size in both the width direction (oval direction). At this time, as for the control of the height direction, since the height direction coincides with the rolling direction, it can be controlled relatively easily as in the strip rolling. On the other hand, in the width direction, since it is a free surface at the time of rolling and there is a complicated width expansion phenomenon, a theoretical analysis of this width expansion has not been performed so far, and the mathematical model that is the basis of the computer has a rough approximation formula. It was. Therefore, conventionally, it has been very difficult to control the width dimension. Therefore, as seen in Japanese Examined Patent Publication No. 59-169610, the cross-sectional dimension of the strip is measured on the exit side of the final stand, and the deviation amount from the target dimension (top and bottom, oval) is obtained, and each deviation amount is a predetermined value. A method of obtaining the optimum value of the change amount of the roll gap so as to be within the dimensional tolerance is adopted. The optimum value of this change amount is obtained by obtaining an evaluation function with the influence factors of the roll gap change amount of each stand on the height and width of the material on the exit side of the final stand and the filling degree in each pass as constraints. It is decided to minimize the function. The advantage of this method is that there is no need to apply a complicated mathematical model by absorbing the entire width expansion phenomenon in the hole type without individually controlling it.

[Problems to be Solved by the Invention]

However, the method proposed in Japanese Examined Patent Publication No. 59-169610 is the feed back control to the next material based on the actual measurement result, and there is no guarantee that it will fall within the target dimensional tolerance from the first rolling. Further, the width expansion significantly changes depending on the material, temperature, etc., but has a problem that it cannot cope with a sudden change in rolling conditions.

[Object of the Invention]

The present invention has been made to solve the above-mentioned conventional problems, and it is a continuous rolling type that can roll a strip having a target size even when the first rolling or a rapid change in rolling conditions occurs. The purpose is to provide an initial setting method of.

[Means for solving problems]

The present invention, under substantially fixed rolling reduction between rolling mills,
In order to absorb the dimensional change caused by the change of rolling conditions for each strip and to obtain the strip with the target dimensions, in the initial setting method of the hole type continuous rolling that determines the fine adjustment amount of the rolling reduction and the mill operation amount, As shown in FIG. 1, the outline of each stand is determined at the time of setting the hole type, the roll rotation speed, and
The roll information including roll diameter and hole shape is used as the initial value, and the rolling distribution is finely adjusted by the rolling model formula that includes the width expansion prediction formula that at least considers the influence of the temperature and composition of the rolled material, and the rolling of each stand is performed. The object is achieved by determining the shape, load and torque, and using the data thus determined to calculate the roll rotational speed and roll opening of each stand. Further, in the embodiment of the present invention, the width expansion prediction formula is calculated by using the formula for determining the width expansion from the average projected contact length, the entrance side width, the entrance side height, the hole die exclusion area, and the entrance side cross-sectional area. A term obtained by multiplying the ratio of B ₀ and the die width B ₁ by an expression including an exponential function consisting of the temperature θ _{S of the} rolled material and the carbon content C, and the rectangle-converted entrance-side height ₀
And a term including the ratio of the rectangle-converted exit-side height of ₁ and a term including the ratio of the entrance-side width and the hole-shaped width, respectively. Further, in the embodiment of the present invention, when calculating the rolled shape of each of the stands, for each combination of stands having different rolling directions, the difference between the second stand stand-out side dimension of the combination and the initial value is within a certain range. As described above, the rolling shapes other than the final stand of the combination are also corrected.

[Operation] Generally, the set-up calculation of a mill in strip rolling is performed by an optimum distribution calculation for determining a target dimension for each pass and a set value for obtaining a mill operation amount such as a roll opening to obtain the target dimension for each pass. It is done in two stages of calculation. On the other hand, in the case of hole rolling, particularly in the case of hole continuous rolling, the optimum reduction distribution calculation is performed when setting the groove, and the groove shape of the roll is determined based on this result. Therefore, due to the restriction of the hole shape of the roll that is fixed once set, it is impossible to significantly change the reduction distribution during rolling, such as setting calculation for sheet rolling. Therefore, the set-up calculation in the hole type continuous rolling of the present invention, the reduction distribution is known, and the change of the top and bottom dimensions and the oval dimension caused by the change of the rolling conditions such as the rolling material temperature and the material is absorbed, and the target dimension (top and bottom dimensions, Oval dimensions)
In order to obtain the strip material, the fine adjustment amount of the reduction distribution between the rolling mills and the mill operation amount such as the roll opening and the roll rotation number are determined. Therefore, in the present invention, the outlet side dimensions (vertical dimension (vertical dimension), oval dimension (oval dimension)), roll rotation speed, and roll information (roll diameter, roll diameter, determined at the time of setting the hole type) The roll opening and roll speed are calculated by using various rolling model formulas with the hole shape) as an initial value. As the breadth prediction formula used for this calculation, the second formula already held from November 23 to 25, 1978
The following formula, which was announced at the 9th Plastic Working Conference, is known. (B ₁ −B ₀ ) / B ₀ = α {d / (B ₀ + 0.5H ₀ )} (Fh / F ₀ ) ...
(1) Here, as shown in FIGS. 2 to 4, B ₁ is the outlet side width (oval size), B ₀ is the inlet side width, d is the average projected contact length, and H ₀ is the inlet side height. (Top and bottom dimensions), Fh is a hole type exclusion area, F ₀ is an inlet side sectional area, α is a square rolling to a diamond rolling,
It is a constant depending on the type of rolling such as diamond rolling to square rolling, oval rolling to round rolling, and round rolling to oval rolling (hereinafter referred to as a width expansion coefficient). Further, is the roll diameter when converted into a rectangle. In the following description, the second
The output side height H ₁ , the rectangular conversion input side height ₀ , the rectangular conversion output side height ₁ , and the hole width Bk shown in FIGS. 3 to 3 are also used. The width expansion prediction formula represented by the above formula (1) is a formula having only geometrical parameters determined by the rolled material and the hole type,
The breadth prediction accuracy is ± 4 according to experiments by the inventors.
%. Since this prediction accuracy is insufficient as a model for online set-up control, the inventors investigated the influence of the temperature and components of the rolled material in order to investigate the cause. Specifically, when the rolling material temperature and the carbon content are changed and other rolling conditions such as the roll opening degree and the roll rotation number are kept constant, the oval dimension B when rolling is given by H4
The stand-out side and the V3 stand-out side were examined. This oval dimension is the dimension in the oval direction described above.
The survey results are shown in FIGS. 5 and 6. In the figure, ● indicates a carbon content of 0.47% and ○ indicates a carbon content of 0.22.
% And □ indicate 0.088%, respectively.
Note that FIG. 5 and FIG. 6 are independently obtained.
As is clear from the figure, the oval size depends on the temperature and carbon content of the rolled material. For the same composition, the higher the temperature, the greater the width spread, and the same temperature, the higher the carbon content. However, the width is getting wider. The fifth
In FIG. 6 and FIG. 6, only the carbon content C is changed to obtain it, but the same applies to the case where other components such as Si, Mn and Cr are added. This can be summarized as follows. (B) Temperature dependence of the width expansion coefficient α The higher the temperature, the larger the width expansion coefficient α. However,
Above a temperature at which all the steel materials become an austenite phase (approximately 910 ° C. or higher as described later), the value becomes constant (the temperature dependence disappears). In addition, at temperatures below the temperature at which all steel materials are in the ferrite phase (approximately 723 ° C or less as described below),
After all, it becomes a constant value (the temperature dependence disappears). (B) Carbon content C dependence of width expansion coefficient α The larger the carbon content C, the larger the width expansion coefficient α. Conventionally, the width expansion coefficient α has been represented only by geometric factors such as the entrance side width B ₀ , the exit side width B ₁ , the entrance side height H ₀ , and the exit side height H ₁ . However, considering the above factors, it is preferable to consider the rolled material temperature, the carbon content C, and the like. Considering the rolling material temperature and the carbon content C, the width expansion coefficient α can be expressed by the following equation. α = f (temperature, carbon content C, geometric factor) + g (geometric factor) (2a) Based on such experimental results, the above equation (2a) is regressed to concrete experimental data. The inventors obtained a regression equation in which the width expansion coefficient α of the above equation (1) is mathematically expressed as the following equation. ^{M = -3.333X 2 + 2.233X- 0.09001 ...} (3) X = ln (0/1) ............ (4) In addition, C alpha as used supra (2) wherein the rolled material 0,910 ° C when the surface temperature θs is less than 723 ° C
In the above case, it is 1, and between 723 ° C. and 910 ° C., it is expressed by the following equation. Here, C is the carbon content as described above. FIG. 7 shows the relationship between the measured value and the calculated value of the width expansion coefficient α, and FIG. 8 shows the relationship between the calculated value and the measured value of the oval dimension when the width expansion coefficient α is used. It is clear that good prediction accuracy is obtained in all cases.
In FIG. 7 and FIG. 8, ◯ mark indicates a sample having a diameter of 110 mm, Δ mark indicates a sample having a diameter of 175 mm, □ mark indicates a sample having a diameter of 207 mm, and ● mark indicates a sample having a diameter of 230 mm. The present invention uses the width expansion prediction formula represented by the above formulas (1) to (5) in consideration of at least the influence of the temperature and composition of the rolled material, and determines the width due to temperature change or component change during rolling. The gist is to accurately predict the change in the spread amount.By using the width spread prediction formula, the cross-sectional shape at each stand can be handled precisely, and the roll opening for rolling the strip material to the target size can be performed. Degree and roll speed are determined by rolling model formula. At this time, if two stands are paired and the number of stands is even, the outlet vertical dimensions of the odd stands should be modified so that the outlet oval dimensions of the even stands match the oval dimensions of the hole design. And, the top-bottom dimension on the delivery side of the final stand, the roll opening for finely adjusting the rolling distribution of the rolling mill so that the oval dimension becomes the target value, and further obtaining the target dimension,
Calculate the roll speed. If the number of stands is odd, the present invention may be applied from the second stand.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, as shown in FIG. 9, a process for obtaining the roll rotation speed and the roll opening is performed in all stands. First, at step 110, an initial value required for set-up calculation is set. As the initial value, for example, the vertical dimension H
₀₁ , material dimensions such as oval dimension B ₀₁ , target top-bottom dimension H _1i aim, target oval dimension B _1i aim (i is stand number), etc., target stand-out side shape, each stand roll rotation number N _i aim, roll diameter D _0i , diamond (diamond),
There is roll information including a hole shape such as oval (ellipse) and material components such as carbon content C (%). Next, at step 112, the rolled shape of the i-th stand,
The load Pi and the torque Gi are calculated. Specifically, the stand-out side dimension of each stand is determined by the rolling model formula, and the load and torque are calculated. In this calculation, in the calculation of the width expansion coefficient α, the existing model formulas are used, except that the above-described formulas (2) to (5) in consideration of the temperature, the carbon content, and the strain are used. I do not care. For example, regarding the rolling shape, reference is made to "Width expansion characteristics of wire rod / bar steel rolling and its mathematical expression (Tsunoki Shinokura / Koichi Takai," Iron and Steel "67th (1981) No. 15 pages 221-226)". Can be obtained by the method shown in. For example, the equation (10) on page 225 of this document is the same as the equation for obtaining the width expansion ratio β _i shown in FIG. 10 of the present invention. As described above, the dimension B _{1i and} the like can be obtained. For the load Pi, see “Rolling load in hot rolling (Shigeru Shida, Hitachi review,
Vol. 52, No. 8 (1970, pp. 57-62) ", especially on p. 60 (23)-(26) and (28). Regarding torque, refer to “Load characteristics of hole rolling and its mathematical expression (Tsunoki Shinokura, Akifumi Katsuyama, Proceedings of the Plastic Processing Society of Japan Spring 1979 (1979. 5.17-19 Tokyo) Proceedings, pp. 509-512”). Especially the fourth on page 512
Can be sought as in section. Further, the parameters used for the above determination may be determined according to each method. An example of a concrete calculation procedure in this step 112 is shown in FIG. In FIG. 10, ΔH _1i is the exit side thickness correction amount. The average temperatures θ ₀ mi and θ ₁ mi are
It can be calculated from the surface temperature θ ₀ si by a commonly used formula. For example, these average temperatures θ ₀ mi, θ ₁ mi,
For the surface temperature θ ₀ si, see “Steel Plate Temperature Prediction Model in Plate Rolling (Seiharu Kumano, Izumo Takahashi, Yutaka Yoshima, Terutaka Onishi, Shigeji Kajiura, Kazuhiko Higashi, Kobe Steel Technical Report / Vol. 36, N.
o.3, pp. 47-49) ", especially the item on page 48, item 3," Simplification of temperature model ", and further using p. 48, equations (7) and (8). You can also In FIG. 10, k _fmi is the average deformation resistance and B _mi is the average width. Q _i is the rolling force function, and ψ _i is the torque arm coefficient. Note that the calculation order may be slightly different depending on the parameters of the model formula used. Next, in step 114, it is judged whether or not the calculated load does not exceed the constraint of the equipment. If it exceeds the constraint of the equipment, the output thickness H _1i of the i-th stand is decreased in step 116. After that, the calculation is returned to step 112 and recalculated. When the result of the determination in step 114 is acceptable, that is, when it is determined that the load does not exceed the constraint of the equipment, the process proceeds to step 118, and the reduction in one direction and the reduction in the direction perpendicular to the direction are set. In the case of a rolling mill having a combination stand for performing the above step, it is determined whether the number of stands is an even number. If the determination result is negative, the process proceeds to step 120, the stand number i is incremented by 1, and the process returns to the previous step 112. On the other hand, when the determination result of step 118 is positive and it is determined that the latter stage stand of the combination, that is, the even stand in the case where one set is two stands, step 122 is performed.
Proceed to step 1 and the _output side oval size B _1i and the target oval size B
Compare _1i aim. If the difference is out of the allowable range ΔB _1i aim, the process proceeds to step 124, where
The outgoing side vertical dimension H _{1 i-1} of the (i-1) th stand in the previous stage is corrected by ΔH _{1 i-1} . ΔH _{1 i-1} = (B _1i aim = B _1i ) / (∂B _1i / ∂
H _0i ) (6) H _{1 i-1} = H _{1 i-1} + ΔH _{1 i-1} (7) Here, the allowable range ΔB _1i aim becomes smaller as it gets closer to the downstream stand. . If the determination result of step 122 is positive and it is determined that the difference between the outlet side oval size B _1i and the target oval size B _1i aim is within the allowable range ΔB _1i aim, the process proceeds to step 126 and the final n-th It is determined whether or not it is a stand. If the determination result is negative, step 128
To increment the stand number i by 1,
Return to step 112 above. On the other hand, when the result of the determination in step 126 is positive and it is determined that the calculation for all stands has been completed, the process proceeds to step 130, where the roll rotation speed N of the final n-th stand.
Roll rotation speed Ni of each stand based on n
Is calculated using, for example, the following equation. Ni = {(1 + Sfn) n} / {(1 + Sfi) i} (F _1n / F _1i ) × Nn
(8) Here, i is the roll diameter in the case of being converted into a rectangle. Next, in step 132, the rolling load Pi of each stand is recalculated from the finally determined material size of each stand, the number of rotations of the roll, and the like. Next, in step 134, the roll opening degree Si is determined from the model of the rolling load Pi and the mill constant Ki of each stand using the following equation, for example. Si = H _1i -2Hki- (Pi-Pi ₀ / Ki ... (9) Here, Pi ₀ is a zero adjustment load. When the number of stands is an odd number and the present invention is applied from the second stand, it is determined whether or not the number of stands is an even number sland in step 118. When a billet having a carbon content C = 0.16% and a diameter of 110 mm is continuously rolled on four stands of V1, H2, V3, and H4, a change from a standard value when a set-up calculation according to the present invention is performed. The condition is shown in Fig. 11. The temperature of the rolled material is 788 ° C (marked with ○), while the rolled material subject to this calculation has a temperature of 767 ° C (marked with ●) of 21 ° C.
Since it has decreased, the size of the oval becomes smaller, and in order to compensate for this, it can be seen that the roll opening degrees of the V1, H2, and V3 stands are larger than the reference value.

【The invention's effect】

As described above, according to the present invention, when the rolling condition is set for each strip, the rolling model formula including the width widening prediction formula considering at least the influence of the temperature and composition of the rolled strip is used. Therefore, there is an excellent effect that a strip material having a target size can be rolled even with respect to the first rolling or a rapid change in rolling conditions.

[Brief description of drawings]

FIG. 1 is a flow chart showing the gist of the initial setting method for hole-type continuous rolling according to the present invention, and FIGS. 2 to 4 are diagrams for explaining the symbols used in the present invention. FIG. 6 is a diagram showing an example of the relationship between the carbon content and the finished surface temperature and the H4 stand outlet side oval dimension for explaining the operation of the present invention. FIG. 6 is also the carbon content and the finished surface temperature. And FIG. 7 is a diagram showing an example of the relationship between the V3 stand outlet side oval dimension, and FIG. 7 is a diagram showing the correspondence between the actual measurement value and the calculated value of the width expansion coefficient used in the present invention.
Similarly, a diagram showing the error between the measured value and the calculated value of the oval dimension, FIG. 9 is a flow chart showing the calculation procedure of the embodiment of the initial setting method of hole type continuous rolling to which the present invention is adopted, and FIG. FIG. 11 is a flow chart showing in detail the procedure for calculating the rolling shape, load, and torque of the i-th stand in the above embodiment, and FIG. 11 is an example of the state of change of the roll opening with respect to the reference in each stand when the present invention is adopted. 12 is a diagram showing V.
It is process drawing which shows the structure of a H4 stand hole continuous rolling mill. B ₁ ... Outgoing width, B ₀ ... Incoming width, d ... Average projected contact length, H ₀ ... Incoming height, H ₁ ... Outgoing height, Fh ... Hole exclusion area, F ₀ …… Inlet side cross-sectional area, α …… Bread spread coefficient, Bk …… Gap width, θs …… Surface temperature, C …… Carbon content, H _1i aim …… Each stand exit side upside down dimension, B _1i aim …… Oval size of each stand exit side, N _i aim …… Each stand roll speed, Pi …… Stand rolling load, Ni …… Stand roll speed, Si …… Stand roll opening.

Claims (3)

[Claims] 1. In order to obtain a strip material having a target dimension by absorbing a dimensional change caused by a change in rolling conditions for each strip material under a substantially fixed reduction distribution between rolling mills. In the initial setting method of the continuous rolling of the groove type that determines the fine adjustment amount and the operation amount of the mill, the roll-out information including the roll-out dimension, the roll rotation speed, and the roll-out side dimension of each stand that was determined when the groove type was designed. With the initial value as the initial value, a rolling model formula including a width widening prediction formula that at least considers the influence of the temperature and composition of the rolled material is used to finely adjust the reduction distribution to determine the rolling shape, load and torque of each stand. An initial setting method for hole-type continuous rolling, characterized in that the roll rotation number and roll opening of each stand are calculated using the data determined as described above. 2. The width spread prediction formula is defined by an average projected contact length,
The exponential function consisting of the temperature of the rolled material and the carbon content in the ratio of the inlet side width to the groove type width is added to the formula for obtaining the width expansion from the inlet side width, the inlet side height, the hole die exclusion area and the inlet side cross-sectional area. Multiplied by a width expansion coefficient consisting of a term multiplied by an expression containing the term, a term containing the ratio of the rectangular converted entrance height to the rectangular converted exit height, and a term containing the ratio of the entrance side width to the hole die width. The initial setting method for hole-type continuous rolling according to claim 1. 3. When calculating the rolling shape of each stand, for each combination of stands having different rolling directions, the combination so that the difference between the stand-out stand side dimension of the combination and the initial value is within a certain range. The initial setting method for hole-type continuous rolling according to claim 1, wherein the rolling shape other than the latter stand is also corrected.