JPH02207909A - Method for online measuring shape of hot rolled material - Google Patents

Abstract

PURPOSE:To accurately make measurement online at the time of measuring the flatness shape of a rolled material from the transverse tension distribution thereof by correcting the tension fluctuation component occurring in the transverse temp. distributing of the rolled material and determining the flatness shape. CONSTITUTION:The tension fluctuation component occurring in the transverse temp. distribution of the rolled material is corrected. The correction of the tension fluctuation component is executed by 'correcting a change in Young's modulus by the temp. change of the rolled material'. The Young's modulus is applied not as a 'constant' but as a 'function E of the temp. T of the rolled material' to the equation for calculating the elongation at the time of determining the transverse elongation rate distribution as the flatness shape from the transverse tension rate distribution. Namely, the elongation rates are calculated by the specific equation with the respective measurement points in the transverse direction. The transverse temp. distribution of the rolled material 2 is measured by disposing, for example, radiation thermometers at suitable intervals in the transverse direction thereof. A measuring instrument of a divided roll 1 system is used for the tension. The measurement error of the sheet shape based on the temp. difference in the transverse direction of the hot rolled sheet is exactly prevented in this way and the precise shape measurement is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for accurately measuring the flatness shape of a rolled material online during hot rolling of a thin plate.

<Prior art and its issues> In recent years, the manufacturing technology for various rolled materials has made remarkable progress, but the progress in shape control technology during the manufacturing of thin sheet materials has been particularly remarkable. Satisfactory accuracy has been achieved with regard to plate thickness distribution. However, regarding the shape of rolled materials in the width direction, the flatness and shape defects are not fully understood, such as "unevenness in the thickness distribution in the width direction" and "unevenness in the elongation distribution in the width direction" of the material. Since the control effect of the flatness is still not sufficient, research continues from various viewpoints in search of accurate online flatness shape control means, and many proposals have been made.

By the way, in these online control technologies for which various proposals have been made, regardless of whether feedback or feedforward methods are adopted, "accurately measuring the shape of the rolled material online" improves control accuracy. Although it goes without saying that it is indispensable for this purpose, conventionally, the "tension distribution in the width direction of the plate that occurs in response to the longitudinal elongation of the plate" has been used as an index for grasping the flatness shape of the thin plate online. It was commonly done. To measure the "tension distribution in the plate width direction that occurs in response to the longitudinal elongation of the plate material," a split roll type shape measuring device as schematically shown in FIG. 4 has usually been used.

The split roll shape measuring device schematically shown in FIG.
A plurality of rolls 1 divided and arranged in the width direction of the rolled material
．． 1,... is pressed against the rolled material 2 online and the force applied to each roll is measured to determine the tension distribution in the width direction of the rolled material.It is highly trusted, especially in cold rolling. This is a device that is widely used.

However, when applied to cold rolling, the above method of measuring the tension distribution in the width direction of a rolled material plate to determine its shape accurately corresponds to the longitudinal elongation distribution, making it accurate. Although it is possible to measure the shape, when this method is applied to hot rolling, the accuracy of the correspondence between the tension distribution in the width direction and the elongation distribution in the longitudinal direction tends to be insufficient, and accurate shape measurement is often not possible. There were reports that it would fall into the

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned problems and provide a means for accurately measuring the online flatness shape of hot-rolled thin sheets, thereby making it possible to stably produce rolled thin sheets with excellent shape accuracy. It was placed in such a way.

<Means for Solving the Problems> As a result of repeated research and repeated numerous experiments in order to achieve the above object, the present inventors have discovered the following (a) and (b).
We were able to obtain the knowledge shown in section 2.

(al) The conventional method of determining the shape by measuring the tension distribution in the width direction of the rolled material plate is effective in cold rolling when i) the rolling environment is around room temperature.

ii) The temperature difference in the width direction of the rolled material is also small.

This is because the tension distribution corresponds accurately to the elongation distribution due to the following reasons. However, in the case of hot rolling, the above conventional method cannot accurately measure the shape because: i) The temperature of the rolled material is high in the finish rolling mill row. Even between the stands, the temperature is still as high as about 1000°C.

ii) Temperature differences in the width direction tend to occur in the rolled material due to uneven cooling of the rolled material by cooling water or the like.

For these reasons, the tension distribution includes "elements caused by temperature deviation in the sheet width direction" and does not correspond correctly to the elongation distribution. Therefore, with conventional techniques that do not take into account the above-mentioned "temperature difference in the width direction of hot rolled material" when measuring tension distribution, it is not possible to accurately grasp the elongation distribution in the longitudinal direction online, and it is not possible to accurately grasp the elongation distribution in the longitudinal direction. Shape control is not possible.

(b) By the way, in actual hot-rolled thin plates, heat radiation from the edges of the plate is large, resulting in a temperature difference of several tens of degrees Celsius between the center of the plate and the edges. However, the Young's modulus (longitudinal elastic modulus), which greatly affects the elongation rate of the rolled material, decreases as the temperature of the rolled material increases, and the degree of change is particularly significant near 1000 ° C., which is the hot rolling temperature.

For example, Figure 1 shows carbon steel (C content: 0.15wt, %
) is a graph showing "Changes in Young's modulus due to temperature", and from this figure 1, it can be seen that the change in Young's modulus due to temperature
It can be seen that in the nearby temperature range, the Young's modulus of the material decreases significantly, making it easier to stretch, and the change with temperature is also extremely large. Incidentally, if we calculate the elongation rate when a uniformly distributed tension is applied to this material, it is generally calculated by measuring the tension applied to the material and dividing it by Young's modulus. If there is a temperature deviation of 100°C within the material, the elongation error will be 1% at room temperature, but at a high temperature of about 1000°C, the elongation error will be as much as 23%. .

Therefore, in the case of hot rolling of a thin plate, it is impossible to accurately grasp the shape by simply measuring the tension distribution in the width direction of the plate, but fluctuations in the tension distribution due to elongation rate deviations caused by temperature differences in the width direction of the plate If this is also taken into consideration, it becomes possible to grasp the plate shape extremely accurately.

The present invention has been made based on the above findings, etc. [In measuring the flatness shape of the plate from the tension distribution in the width direction of the rolled material in a hot rolling line for thin sheets, By correcting the resulting tension fluctuations and determining the flatness shape, the accuracy of online shape measurement of hot-rolled materials has been further improved.

Effects> The main objective of the present invention is to correct tension fluctuations caused by the temperature distribution in the width direction of the rolled material when measuring the flatness profile from the width direction tension distribution of the rolled material in a hot rolling line. For example, the above tension fluctuation is corrected by "correcting the change in Young's modulus due to temperature change of the rolled material."

In other words, when calculating the elongation weight distribution in the width direction as a shape of plate flatness from the tension distribution in the width direction, Young's modulus is not used as a “constant” but as a “function ELT of the rolled material temperature T” in the elongation rate calculation formula. applied to.

That is, the elongation rate is calculated using the following formula for each measurement point in the board width direction.

Note that the temperature distribution in the width direction of the rolled material can be measured, for example, by arranging radiation thermometers at appropriate intervals in the width direction of the material.

By adopting such a plate shape measurement method, measurement errors in plate shape measurement due to temperature differences in the width direction of the rolled thin plate material as described above can be accurately prevented, making accurate shape measurement possible. .

Next, the present invention will be explained with reference to Examples and in comparison with Comparative Examples.

<Example> Table 1 shows carbon steel (C content:
This is a summary of the results of measuring the distribution of temperature, Young's modulus, and elongation in the sheet width direction when hot-rolling 0.15 wt, %).

For the measurement, a well-known radiation thermometer was used to measure the temperature, and a known split roll measuring device as shown in FIG. 4 was used to measure the tension. Furthermore, regarding the elongation rate, in addition to those measured by the method according to the present invention, as comparative examples, we also include the values measured by the conventional method (online measurement without temperature correction) and the offline measurement method (corrected for heat shrinkage). Indicated.

Regarding these measured values, the horizontal axis shows the position in the board width direction (
The distance from the center of the board width) is shown in Figure 2 as a graph, but in order to make it easier to compare each measurement value, the area near the mother end of the board is shown as an enlarged diagram in Figure 3. .

Of these, Figure 2 tal and Figure 3 +8) show the temperature distribution in the plate width direction. A significant temperature drop was observed. Therefore, the Young's modulus distribution associated with this temperature drop shows a considerably sharp increase near the root end compared to the center of the plate width, as shown in Figure 2) and Figure 3(b).

Young's modulus El considering this change due to temperature? The elongation distribution in the sheet width direction calculated using the method of the present invention is shown by a solid line in FIG. 2 (IC) and FIG. 3 (C).

Furthermore, the broken lines in Figure 2 (C1) and Figure 3 (C) indicate the elongation calculated by the conventional method, in which the Young's modulus based on the temperature of the rolled material at the center of the plate width is applied over the entire width when calculating the elongation rate from the tension. The -dotted chain line represents the elongation distribution measured off-line after rolling with correction for heat shrinkage.

As is clear from these figures 2 (C1) and 3 (C1), the elongation rate distribution measured by the method of the present invention almost deviates from the offline measured value even in the vicinity of the root tip where errors are likely to occur. There is no distortion, and an extremely accurate elongation distribution is obtained from the center of the plate width to the edges.

In contrast, the elongation rate distribution measured by the conventional method is
Although an accurate value is obtained near the center of the sheet width, as it approaches the edge of the sheet, it deviates significantly from the offline measured value, indicating that it does not show the correct elongation distribution.

(Summary of Effects) As explained above, according to the present invention, it is possible to accurately and accurately measure the flatness shape of a hot-rolled thin sheet material online, and based on this, the flatness shape control for flatness shape control can be performed online. This brings about extremely useful effects industrially, such as making it possible to accurately set various manipulated variables.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in Young's modulus of carbon steel depending on temperature. Fig. 2 is a graph showing the distribution diagram of various measured values in the sheet width direction on a hot rolled steel plate, Fig. 2(a) shows the temperature distribution, Fig. 2(b) shows the Young's modulus distribution, and Figure 2 (C
1 shows the elongation rate distribution. FIG. 3 is an enlarged view of a part of the graph shown in FIG. 2.
Figure 3(b) is related to Young's modulus distribution;
Figure (C1 is an enlarged view of the elongation distribution. Figure 4 is a schematic explanatory diagram of a split roll type shape measuring device. In the drawings, 1... split roll, 2... rolled material.

Claims (1)

[Claims] A method for measuring the shape of plate flatness from the tension distribution in the width direction of the rolled material on a hot rolling line for thin sheets, characterized in that the flatness shape is determined by correcting tension fluctuations caused by the temperature distribution in the width direction of the rolled material. An online shape measurement method for hot-rolled materials.