JPS6240082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for correcting defects in the planar shape of a finished plate during thick plate rolling. As is well known, thick plate rolling is usually performed by reverse rolling, in which the thickness of the plate is reduced from the slab and finished to a predetermined thickness. As shown by the solid line, it may take on a rhombic or parallelogram-like shape. It goes without saying that such a shape defect (hereinafter referred to as a perpendicularity defect) is a major cause of a decrease in product yield. The present invention aims to provide a rolling method that minimizes this defective finished shape during thick plate rolling. As a result of experiments conducted by the present inventors, it has been confirmed that the main cause of the above-mentioned shape defects is oblique jamming that inevitably occurs due to poor guidance of the rolled material on the entry side. One of the causes of such diagonal jamming is as follows. In thick plate rolling, when the rolled material is bitten by the rolls, the second
As shown in the figure, the rolled material 1 is moved toward the roll 3 while being guided by the side guides 2, 2, which have been set in advance to match the maximum width of the rolled material. The edges on both sides of the rolled material being guided are not maintained in a straight line during rolling, but in particular, the leading and trailing edges during the width-out pass, that is, the side edges during the finishing pass, gradually change into a convex shape. is customary. For this reason, the guidance of the rolled material 1 by the side guides 2, 2 becomes uncertain,
As a result, diagonal jamming occurs. By the way, it is widely known that the shape change of the plate before and after rolling is affected by such oblique rolling, and it has been conventionally known that shape defects such as the above-mentioned perpendicularity defects can be corrected by changing the rolling bite angle. Attempts have actually been made to correct this. Conventionally, regarding the relationship between rolling bite angle and shape change before and after rolling,
Only a few qualitative facts were recognized, such as that the corner on the side that was bitten first changed to an acute angle after rolling, and the setting of the rolling bite angle to correct shape defects was also difficult. In the past, the actual situation was that operators relied on their experiential, so to speak, intuition-based judgments, and stable results could not be expected. Therefore, if a quantitative relationship between the rolling bite angle and the change in shape before and after rolling can be found, its utilization can be expected to be highly effective in preventing the occurrence of shape defects. The present inventor carried out geometric studies in order to elucidate the quantitative relationship between the two, and as a result, succeeded in obtaining a relational expression (J) described below that is well suited to reality. The analysis method is shown below. First, as a prerequisite for the analysis, as shown in Figure 3, the planar shape before and after rolling is formed by four straight lines (a), (b), (c), (d) and (a'). , (b′), (c′),
(d′)
Let each be a quadrilateral surrounded by . For rolling rolls, width expansion is ignored and it is assumed that all rolls are stretched in the rolling direction. In the same figure, a flat rolled material shown by a solid line has one side edge (d) facing a line (f) perpendicular to the roll axis in the direction in which the obtuse corner portion 1a on the top side is bitten first. Δθ _F =θ ₃ −θ ₁ ...(A) tanθ ₃ =W ₁ /L ₃ ...(B) tanθ〓= W ₁ /L ₂ ...(C) However, Δθ _F : Deviation value from the right angle of the corner angle of the top side obtuse corner after rolling, that is, the degree of perpendicularity θ ₁ : Roll of the leading edge (a') after rolling Angle with respect to the axis θ ₃ : Angle between the side edge (d') after rolling and a line (f) perpendicular to the roll L ₂ : Projected length of the side edge (d) before rolling in the direction perpendicular to rolling L ₃ : Same length after rolling W ₁ : Projected length of the side edge (d') in the rolling direction before or after rolling Here, assuming θ ₃ and θ〓 to be minute, from (B) and (C)
When W ₁ is eliminated, θ ₃ ≒L ₂ /L ₃・θ〓 ...(D) holds true. Also, tanθ ₁ =L ₁ /W ₂ ...(E) tanθ ₂ =L ₀ /W ₂ ...(F) However, θ ₂ : Angle of front edge (a) before rolling with respect to the roll axis L ₀ : Same as above Projected length of the side in the direction perpendicular to the rolling direction L ₁ : Projected length of the leading edge side (a') after rolling in the direction perpendicular to the rolling direction. Considering θ ₁ and θ ₂ to be minute, θ ₁ ≒ L ₁ / L ₀・θ ₂ =L ₁ /L ₀・(θ〓−Δ
θ _P )... (G) Here, Δθ _P is the degree of perpendicularity of the top side obtuse corner portion 1a before rolling. Substitute the relational expressions of (D) and (G) above into (A) at the beginning. Also, L ₁ /L ₀ =L ₃ /L ₂ =H ₀ /H ₁ ...(H) where, H ₀ : Thickness before rolling H ₁ : Thickness after rolling Using the above relationship, Δθ _F =H ₀ /H ₁・Δθ _P −(H ₀ /H ₁ −H ₁ /
H ₀ )・θ〓...(I). Therefore, in order to set Δθ _F =0, In short, this relationship is based on the degree of perpendicularity Δθ after rolling.
This shows the relationship between θ〓 and Δθ _P where _F is 0. This relationship can also be applied to the obtuse corner 1C on the bottom side and the other two corners, with the same sign. Examples of experiments that prove the validity of the above analysis include the following. [Experiment example] (1) Slab Miniature lead slab with the following dimensions: 20 mm thick x 150 mm wide x 200 mm long 10 mm thick x 150 mm wide x 200 mm long (2) Rolling machine used Work roll: 105 mm diameter x 400 mm body length, back-up roll : A small 4-high rolling mill with a diameter of 330mm and a length of 400mm. (3) Rolling pass schedule

【table】

[Table] Regarding the positive and negative signs of θ〓, the slope in the direction shown in FIG. 4 is assumed to be positive. Pass directions: A and B refer to mutually opposite directions in the longitudinal direction of the slab, as shown in FIG. Rolling was carried out under the above conditions. At this time, the degree of perpendicularity of the four corners of the plate plane was actually measured after each pass. For actual measurements, the method shown in FIG. 6 was used. In other words, after rolling, each side of the sheet shape was actually curved at the end as shown in the same figure, so at this time, draw a straight line along the center of the four sides, ignoring the curved parts at the four corners. , a method was adopted in which the degree of perpendicularity was measured by assuming that the area surrounded by these straight lines was the planar shape of the plate. In addition, the sign of the degree of perpendicularity was defined as positive in the case of an obtuse angle and negative in the case of an acute angle. On the other hand, using the above formula (1), the above rolling pass schedule and the measured perpendicularity defect (Δ
From θ _P ), the degree of perpendicularity (Δθ _F ) of the four corners of the plate plane at the end of each rolling pass was predicted. From the measured squareness defects before the pass at each of the two corners on the top side and the bottom side (here, the top and bottom refer to the side that bites first in the pass as the top and the opposite side as the bottom), Calculate the average of the absolute values, give the sign of the squareness value of the right corner in the rolling direction on the top side, and the left corner on the bottom side, and calculate these values for the top side, the left corner, and the bottom side. This was represented as the degree of right angle defect on the bottom side, and this was substituted into each equation () to determine the degree of right angle defect at the top and bottom after rolling. In order to correspond to this calculated predicted value, based on the degree of perpendicularity of the four corners of the plane actually measured at the end of each pass,
Two values each for the top side and the bottom side were compiled using the same method used to determine the degree of perpendicularity before the rolling pass described above. Figure 7 shows a comparison between the calculated values and the measured values. In the figure, white symbols indicate the rolling top side of each pass,
The black symbols are on the rolling bottom side of each pass, and the shape of the symbol indicates the slab number, △: No.1, □: No.2, ◇:
No. 3, 〇: Represents No. 4, respectively. In the same figure, if a symbol lies on a straight line drawn at 45°, it indicates that the calculated predicted value and the actual measured value match, but from the same figure it can be seen that the two values agree well with a fair degree of accuracy. I understand. In other words, the validity of equation (1) was confirmed. Therefore, it can be said that Equation (J), which represents the relationship between θ〓 and Δθ _P , which makes the degree of perpendicularity Δθ _F after rolling 0, is sufficiently applicable in practice. Based on the premise of using this formula (l), the approach angle θ required to eliminate the perpendicularity defect after rolling while maintaining the planned rolling schedule is calculated based on the actual value of the planar shape of the plate during rolling.
This means that it is possible to calculate backwards predictively. That is, in the rolling of a thick plate, the present invention actually measures the degree of perpendicularity Δθ _P for all or part of the four corners of the plate plane during rolling, calculates θ〓 by the following formula based on this measured value, and A method for controlling the planar shape of a plate in thick plate rolling, characterized in that the plate is rolled in a horizontal plane with the obtuse corner portion tilted by the angle θ in the direction in which the obtuse corner portion is first bitten with respect to the normal rolling direction. Here, H ₀ : Thickness at the entrance of the rolling pass H ₁ : Expected thickness at the outlet of the rolling pass based on the rolling schedule ΔΘ _P : 1/m・Σ | Δθ _P | m: Actual number of Δθ _P (m=1 to 4) Σ|Δθ _P |: The gist is the sum of the absolute values of m actual measured values Δθ _P. Strictly speaking, the above-mentioned "regular rolling direction" is a direction in which the center line of both side edges of the plate is perpendicular to the roll axis, but in reality, any one of the side edges of the plate is perpendicular to the roll axis. There is no substantial difference in effectiveness even if the direction is defined as . Δθ
Of course, it is preferable to measure _P at all four corners of the plate plane, but even if you measure only a part of it,
The results obtained are not very different. A specific embodiment of the control method of the present invention will be described below with reference to the block diagram of FIG. First, for a specific pass of rolling, the corner angles of the four corners of the plate plane are actually measured on the entry side using, for example, an image processing device 5 using a television camera 4. At this time, the length (L) and width (W) of the board are determined at the same time.
Also measure. Next, the calculator 6 receives the output value of the corner angle and receives the absolute value of each corresponding degree of squareness |
Calculate Δθ _P | and find the average (ΔΘ _P ),
Furthermore, the value of the plate thickness H ₁ after rolling is received from the process calculator 7, which is the same as the plate thickness H ₀ before rolling, which has been set in advance based on the rolling schedule, and θ〓 is calculated using the above formula (K). , and at the same time this θ〓
Required side guide width (B) when approach angle is
is calculated using the formula below. (See Figure 8) B=L・sinθ〓+W・cos(θ〓− _ΔΘP )
...(L) Note that Figure 8 shows the case where the steel plate is a parallelogram. The values (θ〓) and (B) calculated by the computer are then input to the control device 8, and the control device 8 sends command signals to the drive devices 9 and 10. Based on this signal, one of the drive devices 9 The opening degree of the side guides 2, 2 is adjusted to match the above calculated value, and the other drive device 10 uses the turntable 11 on which the rolled plate is placed to turn the rolled plate into an obtuse angle corner by θ〓 with respect to the normal rolling attitude. In this state, the rolling plate is fed while being guided by the side guides 2, 2, and rolling is performed. The implementation stage of such inclined rolling is not particularly limited. However, in the latter half of the finishing pass, the length of the rolled plate becomes longer and the calculated value of the side guide width (B) described above may exceed the maximum value of the equipment. Or, it can be said that the first half of the finishing pass is appropriate. Needless to say, the more times rolling is performed according to the method of the present invention, the more effective it is in correcting the planar shape of the plate. Note that the method of the present invention is effective in improving crop shape when applied to, for example, hot rough rolling in addition to thick plate rolling. As explained above in detail, according to the method of the present invention, it is possible to very effectively eliminate the occurrence of squareness defects in the planar corners of finished plates during thick plate rolling, and the product yield in thick plate rolling can be significantly improved. is achieved.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the occurrence of defects in the planar shape of products during thick plate rolling, Fig. 2 is a plan view showing normal thick plate rolling conditions, and Fig. 3 explains the geometric analysis of the relational expression used in the present invention. The explanatory drawings, FIGS. 4 to 6 are schematic diagrams for explaining the embodiment of the method of the present invention. FIG. 4 shows the direction taken by the approach angle (θ〓) during rolling, and FIG. 5 shows the rolling direction. and FIG. 6 respectively show the method of measuring the squareness. FIG. 7 is a chart showing a comparison between the predicted perpendicularity according to the relational expression obtained in FIG. 3 and the actually measured perpendicularity; FIG. FIG. 9 is a plan view illustrating a method of setting the side guide width (B) in implementing the present invention. In the figure, 1: Rolled plate, 2: Side guide, 3: Roll roll, 4: Television camera, 5: Image processing device, 6: Arithmetic machine, 7: Process computer, 8: Control device, 9, 10: Drive device , 11: Turntable.

Claims (1)

[Claims] 1. In rolling a thick plate, the deviation value (Δθ _P ) of the corner angle with respect to the right angle is actually measured for all or part of the four corners of the plate plane during rolling, and based on this measured value, θ〓 is determined by the following formula. A method for controlling the planar shape of a plate in thick plate rolling, characterized in that the plate is tilted within a horizontal plane by θ〓 in a direction in which the obtuse corner portion is first bitten with respect to the normal rolling direction. Here, H ₀ : Measured plate thickness at the entrance of the relevant rolling pass H ₁ : Expected plate thickness at the exit side of the relevant rolling pass based on the rolling schedule ΔΘ _P : 1/m・Σ | Δθ _P | m: Actual measurement number of Δθ _P Σ | Δθ _P |: Sum of absolute values of m actually measured Δθ _P