JPH063240A - Detecting device for hardness abnormal part of steel strip - Google Patents

Abstract

PURPOSE:To precisely detect a hardness abnormal part by stretching a steel strip by an elongation percentage giving device having an elongation percentage control means, and detecting the tension fluctuation of the steel strip. CONSTITUTION:A steel strip 12 after finish annealing is passed through a tension leveler to regulate the form. At this time, the tension of the steel strip 12 between inlet side and outlet side bridles 16, 18 is detected by a tensiometer 20, converted by a tension converter 22, and outputted to a tension change quantity computing element 28 and a recording system 30. On the other hand, a speed computing element 24 operates the line speed of the steel strip 12 on the basis of the signal from a PLG 32 corresponding to the feed quantity of the steel strip 12 in the bridle 18, and outputted to the computing element 28 and the recorder 30. The output signal of the PLG 32 and the actual elongation percentage of an elongation percentage computing element 26 are also inputted to the recorder 30. The computing element 28 calculates a tension change quantity on the basis of the input signals from the converter 22 and the computing element 24, and inputs it to the recorder 30. The recorder 30 continuously records them on a recording paper. From these records, the change of tension and tension change quantity in steel strip 12 is observed, and when it is abnormal, a hardness abnormality in this position is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormal hardness portion of a steel strip online.

[0002]

2. Description of the Related Art Conventionally, a steel strip has a hardness within a standard measured by off-line measuring the hardness of a test piece taken from the steel strip with a Vickers hardness tester, a Rockwell hardness tester or the like. It was judged whether or not. On the other hand, as a method of measuring the hardness online, a grain size meter or a magnetic hardness measuring device can be considered.

[0003]

When the hardness of a steel strip is measured off-line with a Vickers hardness tester or the like, a specimen is taken from a part of the steel strip. The leading and trailing ends of the strip are not necessarily stable in quality, so it was hard to say that the measurement results represent the hardness of the steel strip.

Further, when the measurement result shows a hardness out of the standard, conventionally, a test piece is again taken from the steel strip and the measurement is carried out. From which part of the steel strip should the test piece be taken? Was only estimated from the history of annealing such as the furnace temperature and sheet temperature chart, and the estimation accuracy was poor, and as a result, the steel strip was cut off extra and the yield was reduced. In addition, when the line stops during annealing even in the central portion of the steel strip, abnormal hardness may occur, but this cannot be measured by the conventional method.

Furthermore, the above-mentioned on-line measuring method has problems that not only the equipment cost is high, but also that data to be the reference of the material to be measured must be prepared, and it is difficult to put it into practical use.

The present invention has been made in view of the above-mentioned conventional problems, and an abnormal portion of the hardness of the steel strip is generated online, even if the abnormal portion occurs in the central portion of the steel strip. Accurate detection, as a result, the optimum sampling position of the test piece can be clarified, pre-annealing conditions, early control defects can be detected, and the product yield can be further improved. An object is to provide a detection device.

[0007]

The present invention relates to a tension leveler or a skin pass mill for adjusting the shape at the end of a rolling process, in which a steel strip is stretched when a predetermined elongation is applied, and at this time, Focusing on the fact that the tensile force applied to the steel strip changes when the hardness changes, the hardness abnormal portion of the steel strip is detected by measuring this change in tension. Therefore, the present invention includes an elongation rate control device, which continuously applies a predetermined elongation rate to a running steel strip, and a tension of the steel strip pulled by the elongation rate imparting device. The above object is achieved by a device for detecting an abnormal hardness portion of a steel strip, which comprises a tensiometer for detecting fluctuations.

[0008]

In the present invention, a steel strip is pulled by an elongation rate imparting device including an elongation rate control means such as a tension leveler or a skin pass mill, and changes in the steel strip tension force when the hardness of the steel strip changes. By detecting, the abnormal hardness portion of the steel strip can be detected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

A hardness abnormality detecting device 10 according to this embodiment.
Is a tension leveler for adjusting the shape of the steel strip 12 after finish annealing. In FIG. 1, reference numeral 14 is a leveler roll, and 16 and 18 are leveler rolls 14.
2 shows an entrance bridle and an exit bridle arranged on the entrance side and the exit side.

The leveler roll 14 and the entrance side bridle 1
At a position between 6 and 6, a tensiometer 20 for detecting the tension applied to the steel strip 12 is arranged. The hardness abnormality detecting device 10 further includes a tension converter 22 and a speed calculator 2
4, an elongation rate calculator 26, a tension change amount calculator 28, and a recorder 30.

The tension change amount calculator 28 is the tension meter 20.
Is to convert the output signal of the steel strip tension F to the steel strip tension F, and the speed calculator 24 calculates the line based on the signal L from the PLG 32 that is output according to the feed amount of the steel strip 12 at the position of the outlet bridle 18. The speed V _D is calculated and output.

The elongation rate calculator 26 calculates and outputs the substantial elongation rate ε'of the steel strip 12 from the speed difference between the entrance side bridle 16 and the exit side bridle 18.

The tension change amount calculator 28 receives the steel strip tension signal F from the tension converter 22, the line speed signal V _D from the speed calculator 24, the elongation rate set value ε and the set elongation rate set value ε. The tension change amount ΔF of the steel strip 12 is calculated based on the input value of the material correction value M.

The recorder 30 includes a tension change amount calculator 2
8 output signal ΔF, tension converter 22 output signal F, speed calculator 24 output signal V _D , PLG 32 output signal L,
Further, the output signal ε'of the elongation rate calculator 26 is inputted to correspond the feed amount of the recording paper to the steel strip length L, and the line speed V _D , the steel strip tension F, and the elongation rate are applied to the recording paper. ε'and the amount of change in steel strip tension ΔF are recorded.

Next, the operation of the hardness abnormality detecting device according to the above embodiment will be described.

Generally, the steel strip 12 after finish annealing is passed through a tension leveler for adjusting the shape. At this time, a predetermined elongation rate ε between the entrance side bridle 16 and the exit side bridle 18 in the tension leveler, that is, Speed difference (V _D −
Shape adjustment is performed by giving V _E ).

In this embodiment, the tension of the steel strip 12 between the entrance-side bridle 16 and the exit-side bridle 18 is detected by the tensiometer 20, and this is converted into the tension signal F by the tension converter 22 to obtain the tension change amount. Output to the calculator 28 and the recorder 30.

On the other hand, the steel strip 1 in the exit bridle 18
The speed calculator 24 calculates the line speed V _D of the steel strip 12 based on the signal L from the PLG 32 corresponding to the feed amount of 2 and outputs it to the tension change amount calculator 28 and the recorder 30. The output signal L of the PLG 32 is the recorder 30
Is also output. On the other hand, the signal of the actual elongation rate ε'of the elongation rate calculator 26 is also output to the recorder 30.

The tension change amount calculator 28 is based on the tension signal F from the tension converter 22 and the line speed signal V _D from the speed calculator 24, the material correction value M set and input, and the set elongation rate ε. The amount of change in tension ΔF is calculated using the recorder 30
Output to.

In the recorder 30, in synchronization with the feed amount signal L from the PLG 32, the line speed V _D , tension F,
The amount of change in tension ΔF and the actual elongation ε ′ are recorded as shown in FIG. This recording is performed continuously for each steel strip.

When a predetermined elongation rate ε is given to the steel strip 12 by the entrance side bridle and the exit side bridle 18, the steel strip 1
2, a tension is applied, and this tension varies depending on the material of the steel strip 12, the elongation rate ε to be set, or the speed.

Therefore, in the same steel strip 12, when the set value ε of elongation and the line speed V _D are constant, the tension F should be constant, but a part of the steel strip 12 is When the hardness becomes different from that of the portion, the tension F changes at that portion and is obtained as the tension fluctuation amount ΔF.

For example, as indicated by reference numeral A in FIG.
The phenomenon that the tension F changes with the front and rear ends of the steel strip 12 is seen.
Examining the concrete properties of the steel strip 12 in this changed portion, FIG.
It was found that in the case of the symbol A, the hardness was high in this portion, whereas the tension F of the steel strip 12 was increased in order to obtain a constant elongation.

Therefore, whether or not there is a change in the steel strip tension F and the tension change amount ΔF within the range in which the line speed V _D and the elongation ε ′ do not change from the recording on the recording paper as shown in FIG. If there is a change as indicated by the symbol A in FIG. 2, it is determined that there is an abnormality in hardness in that portion of the steel strip 12, and the abnormal hardness portion is cut off and eliminated in the next step.

Here, the steel strip tension F changes according to the line speed V _D in the central portion of the horizontal axis of FIG. 2, but this is due to the change in strain rate of the steel strip 12 and the like. If correction is added or operation is performed at a constant speed so that the change does not occur like ΔF in FIG. 2 and ΔF changes only due to hardness abnormality, the abnormality determination becomes easier. .

According to the experiments conducted by the present inventor, the material SUS41
0, thickness 2.0 mm, width 1245 mm steel strip, elongation 1.
Skin pass rolling at 0% and speed 50m / min, steel strip tension F
When (Kg) was recorded and observed, it was about 300 at the rear end of the steel strip.
0kg Tension increased.

The test pieces of the tension-increased portion and other portions were sampled, and the hardness was measured by a Rockwell hardness tester. HR _(B) = 85 at the portion where the tension F increased, and the other portion It was confirmed that HR _(B) = 72, the change in hardness of the steel strip was changed to the change in tension, and the tension became large in the high hardness portion.

In the above embodiment, the present invention is applied to a tension leveler or a skin pass mill, but the present invention is not limited to this. As long as it is equipped with an elongation imparting device that continuously imparts a predetermined elongation to the steel strip inside,
It can be generally applied.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a hardness abnormality detecting device for a steel strip according to the present invention.

FIG. 2 is a diagram showing an example of tension change detection by the apparatus of the embodiment.

[Explanation of symbols]

 10 ... Abnormality hardness detection device 12 ... Steel strip 16 ... Incoming bridle 18 ... Outgoing bridle 20 ... Tensiometer 28 ... Tension change amount calculator 30 ... Recorder

Claims (1)

[Claims] Claim: What is claimed is: 1. An elongation-applying device including elongation control means for continuously giving a predetermined elongation to a running steel strip, and a tension fluctuation of the steel strip pulled by the elongation-applying device. And a tension meter for detecting the hardness of the steel strip.