JPS6119321B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling the dimensions of strip materials, particularly round bars such as steel bars and wire rods. Generally, in rolling mills for steel bars and wire rods, it was thought that keeping the tension constant was effective in controlling the dimensions, but when there is a temperature change in the strip, the patent application filed by the applicant Patent Application No. 51-62235
145357), even if the tension is constant, the width changes, so it has been found that it is necessary to adaptively change the tension depending on the temperature. However, small-diameter steel bars are often loop-rolled, and it is impossible to vary the tension, so an alternative method is required. On the other hand, there are Japanese Patent Publication Nos. 50-39066 and 50-39067 as methods for controlling dimensions by rolling, but these measure the dimensions of the strip at the exit side of the rolling mill, and based on this value, the two upstream machines Although this method controls rolling reduction, it is technically difficult to put it into practical use because the rolled material is twisted, making it impossible to accurately determine the vertical and width dimensions. The present invention was devised in view of these drawbacks of the conventional methods, and provides an effective dimensional control method using only the final rolling mill. The present invention will be explained below with reference to the drawings. Figure 1 shows experimental data showing the relationship between width expansion ratio and rolling temperature, and shows the exit side when an oval material with a major axis of 45.61 mm and a minor axis _b1 of 19.65 mm is rolled in a rolling mill with a round hole of 25.6 mmφ. The width dimension b ₂ is the short diameter of the entry side material b ₁
It is a relationship diagram between the width expansion ratio b ₂ /b ₁ divided by b 2 /b 1 and rolling temperature. As is clear from FIG. 1, the width increases as the rolling temperature decreases. The present invention was made by paying attention to the temperature dependence of width expansion obtained through experiments, and compensates for changes in width expansion due to temperature by rolling reduction in the final rolling mill. In the experimental data shown in Figure 1, the gap of the roll was fixed so that the vertical dimension (dimension of the point in contact with the roll) did not change, but in an actual rolling mill, the roll has multiple holes, and the roll and rolling It has been found that the mill rigidity changes due to shifting of the machine, and that the mill rigidity itself is not necessarily a large value, and it has become clear that dimensional changes in the vertical direction cannot be ignored. Due to this temperature, the dimensional change in the vertical direction has the function of alleviating the change in the width dimension, and the present invention utilizes the relationship between the rolling temperature and the dimensional change in the vertical and width directions to reduce the amount of dimensional variation and improve dimensional accuracy. This is something we aim to improve. Now, taking Figure 1 as an example, the relationship between the amount of width spread b ₂ - b ₁ and the temperature T is b ₂ - b ₁ = b ₁ {0.28 - 0.02 (T - 900) / 100}
…It can be found by equation (1), but if we only refer to the change Δb due to the rolling temperature change ΔT in the width dimension b ₂ , then Δb=−0.02b ₁・ΔT/100 =R ₁・ΔT …The relationship expressed by equation (2) can be found. , which can be determined for all rolling sizes through experiments or data analysis during actual rolling. On the other hand, regarding the vertical dimension, since the rolling load F is also a function of temperature, the mill rigidity M
(Ton/mm), the amount of change ΔH in the vertical dimension is determined by Hook's law as ΔH=ΔF/M...Equation (3). Here, ΔF is a change in rolling load due to a change in rolling temperature ΔT, and this can also be determined by experiment or data analysis of actual rolling. However, if the vertical dimension changes as shown in equation (3), the width dimension will be affected. This is due to the effect that when the incoming cross-sectional area is constant, the outgoing cross-sectional area is also kept almost constant; if the vertical dimension increases, the width dimension decreases, and vice versa. This can be approximated as shown in FIG. 2 if the change is small. In FIG. 2, the vertical axis represents the width dimension change ΔB, and the horizontal axis represents the vertical dimension change ΔH, and shows the influence on the width dimension when the vertical dimension changes, or vice versa. In the relationship in equation (2), the vertical dimension is fixed, so the change in width ΔB when the vertical dimension changes is obtained by subtracting the change in width Δb' due to the change in the vertical dimension from Figure 2 (4) It is approximately expressed by the formula. ΔB = Δb - Δb' = Δb - R ₂・ΔH = Δb - R ₂・ΔF/M ... Formula (4) where R ₂ is a positive constant, and the vertical reduction is varied in the actual rolling shown in Fig. 2. It can be determined from the change in width dimension when In this way, the vertical dimension change ΔH and the width dimension change ΔB when the rolling temperature changes by ΔT are determined. Next, the rolling reduction of the rolling mill is corrected by ΔS to equalize the above-mentioned vertical dimension change and width dimension change. Think about it. The vertical dimension change ΔH due to the current temperature change ΔT,
Let us consider two cases in which the width dimension change ΔB is ΔHΔB and ΔH<ΔB. Figure 3 shows the dimensional change on the vertical axis and the reduction change ΔS on the horizontal axis.
It shows how is affected when changing . (Case 1) Case of ΔHΔB This corresponds to the case where the mill rigidity is small as shown in Fig. 3a, and the variation in the vertical dimension is larger, but if the rolling reduction is made smaller (ΔS0)ΔH becomes smaller. At the same time, the width spread ΔB increases, so the amount of dimensional variation becomes the smallest at point P where both coincide. (Case 2) When ΔH<ΔB As shown in Figure 3b, when the mill rigidity is high, the width dimension change is larger, but if the rolling reduction is increased (ΔS>0), the vertical dimension increases and the width dimension changes at the same time. There is a point P' where both become smaller and coincide, and the amount of dimensional variation is minimized there. Therefore, the reduction correction amount ΔS that should be determined is the change ΔS in the vertical dimension due to ΔS.
Similarly, it is sufficient to satisfy the following equation by considering the change in width ΔB'.

[Table] 〓...Equation (5)
ΔF

Claims (1)

[Scope of Claims] 1. Measure the temperature of the strip at the entrance of the rolling mill in a grooved strip rolling mill, and determine the width dimension change ΔB and the vertical and vertical changes in the rolling mill caused by this temperature change ΔT. A dimensional control method for a round bar, comprising predicting a dimensional change ΔH and determining a necessary reduction correction amount so that the width dimensional change and the vertical dimensional change become equal. 2. A cross-sectional dimension measuring device that rotates around the strip material is provided downstream of the final rolling mill, and the output of the measuring device is used to correct the prediction formula for vertical and width dimension changes based on strip material temperature changes and reduction corrections. A method for controlling the dimensions of a round bar according to claim 1. 3 A cross-sectional dimension measuring device that rotates around the strip material is installed downstream of the final rolling mill, and the deviation from the target value of the vertical and horizontal dimensions is determined from the output of the measuring device, and the vertical, vertical, 2. The method of controlling dimensions of a round bar according to claim 1, wherein the reduction is corrected so that the deviations from the respective target values obtained by adding the predicted amount of change in the width dimension are equal. 4. A round bar dimension control method according to claim 3, wherein the final exit width dimension of the strip is roughly adjusted by rolling reduction correction of two rolling mills upstream of the cross-sectional dimension measuring device.