JPH02280906A - Method for confirming earing of pipe rolled by mandrel mill - Google Patents

Abstract

PURPOSE:To confirm the possibility of generation of earing by detecting the state of distribution of temperature change parts of a pipe in the shape of a vertical stripe in the mandrel mill rolling of a pipe and diacriminating the presence or absence of fins causing earing in the following stage from the state of its distribution. CONSTITUTION:When a mandrel 2 is inserted into a hollow piece 8 and the hollow piece is rolled by the mandrel mill 3 to obtain a pipe 1, the distribution state of the temperature change part observed as distribution state of the vertical striped pattern generated on the pipe 1 is observed is measured by a distribution state detecting device 4 provided on the outlet side of the mandrel mill 3, the result is thrown into an arithmetic unit 16, compared with a preset criterion and whether the fins are generated or not is checked by the arithmetic unit 16 to remove parts of earing from the line. In this way, frequent occurrence of defective material by the earing can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to detecting the presence or absence of bite in a pipe rolled by a mandrel mill to determine whether or not ear cracks occur.

[Prior Art] In rolling a pipe using a mandrel mill, the inner surface of the pipe is restrained by a mandrel bar having a predetermined outer diameter, and external pressure is sequentially applied using a row of grooved rolls built into a continuous stand. This is a one-bath rolling process that reduces thickness. FIG. 7 is an explanatory diagram showing an outline of the equipment configuration related to the mandrel mill. The hollow piece 8 drilled by the punching machine 7 is inserted into the insert line 9 with a mandrel bar 2 sent in the tube axis direction before being rolled by the mandrel mill 3, and is rolled by the mandrel mill 3 to form the pipe 1. The pipe 1 is conveyed to a round strip line 10 containing the mandrel bar 2 therein. At the strip line 1°, the pipe 1 is held at one end by the shell stopper 14, and the mandrel bar
2 is pulled out in the tube axis direction by a burst stripper 17. The pulled mandrel bar 2 is cooled in the bar cooling zone 11 and then returned to the insert line 9. Further, the pipe 1 after being rolled by the mandrel mill 3 passes through a reheating furnace 21 and is then rolled to a required size in a stretch reducer 22 in the next step.

[Problems to be Solved by the Invention] However, the following problems have conventionally occurred in mandrel mill rolling. That is, in order to insert and pull out the mandrel bar 2 into the pipe 1 before and after rolling the pipe 1 with the mandrel mill 3, there is a gap in advance between the inner diameter of the pipe 1 and the outer diameter of the mandrel bar 2. Since the suitability or tolerance is set, the constraint on the inner surface of the pipe 1 has to be relatively loose. Therefore, the deformation of the pipe 1 during rolling with the mandrel mill 3 is particularly severe in the circumferential direction of the pipe 1. Metal flow tends to become unstable, resulting in overfill and underfill. Now, the deformation of the pipe 1 in the stand will be considered separately on the groove bottom side and the flange side, depending on whether or not the pipe 1 is restrained on the inner surface, that is, whether the inner surface of the pipe 1 is in contact with the mandrel bar 2. The material on the bottom side of the groove receives external pressure from the roll 13, and the material on the mandrel bar 3
Since it is rolled while receiving internal pressure from the groove, it is stretched in the axial direction and at the same time expands in width in the circumferential direction, and the material on the flange side is stretched in the axial direction due to the elongation of the material on the bottom side of the groove. At the same time, width pinching occurs in the circumferential direction. In this case, if a certain relationship is not satisfied between the widening of the groove bottom side and the width narrowing of the flange side, overfilling or underfilling will occur. If the overfill is significant, bulging occurs in the gap between the rolls.

Moreover, if bulging occurs at one stand, the rolling reduction amount at the next stand becomes excessive, causing another bulging, and this may extend to the final finishing stand as a chain reaction. This will cause ear scratches.

In this way, by the time the operator noticed that the overfill was so severe that bite occurred during the mandrel mill rolling, and that ear scratches were occurring during the next rolling process, a considerable amount of the pipe 1 had finished rolling. Even if an instruction was given to immediately suspend subsequent rolling operations, the factory would still suffer significant damage.

The present invention has been made to solve the above problems,
The purpose of this project is to provide a technology that determines whether or not ear cracks will occur in pipes that have been rolled by a mandrel mill, by determining whether or not there are bites that can cause ear cracks in the next rolling process. be.

[Means for Solving the Problems] A mandrel mill including a plurality of stands arranged in parallel as described above has caliber rolls arranged alternately orthogonally in a 45° direction. After rolling the pipe with one pass of such a mandrel mill, the mandrel bar is removed and the pipe is rolled to a required size in a rolling mill in the next step.

As shown in FIG. 4(a), the mandrel mill 3- in which the rolls arranged in the 45° direction are alternately perpendicular to each other and similar rolling is repeated in odd or even numbers is usually used. The pipe 1 is rolled without biting into the flange portion of the roll 13. However, if the overfill is significant, occlusion occurs as shown in FIG. 4(b). Then, the range between A and B and CD that is rolled by the roll 13 and the mandrel bar 2 also expands. Therefore, the areas A to B and 0 to 0 that are rolled by the roll 13 and the mandrel bar 2 are simultaneously cooled and the area where the temperature locally decreases is also expanded. As a result, the distance between the temperature change areas A and B, which is observed as a bright and dark vertical striped pattern called a black stripe, is as shown in Fig. 5 (
In Figure 0, which is uniform as shown in a), the black area indicates the temperature change area.

When observing the pipe 1 in which the above-mentioned bulging has occurred, the vertical striped pattern shows a distribution state in which the intervals change or the intervals are not constant, as shown in FIG. 5(b). ing.

The present invention analyzes the relationship between the above-mentioned bite of the pipe 1 and the distribution state of the temperature change part, stratifies this and sets a standard in advance, and then uses this preset standard and the rolled pipe 1. By detecting the distribution state of the temperature change part of the pipe 1 and comparing the detected distribution state of the temperature change part of the pipe 1, it is possible to discriminate whether there is a protrusion or not. This is based on new knowledge that it is possible to determine the probability of inducing ear lesions, that is, to determine whether or not ear lesions will occur.

FIGS. 2 and 3 are a flowchart showing the processing procedure of such an ear flaw determination method, and a block diagram showing a control circuit. The temperature of the hollow piece 8 punched by the punching machine 7 is measured by a temperature measuring device 12 . This temperature measurement is to confirm that the temperature is within the range that can be rolled by the mandrel mill 3, and the hollow piece 8 that can be rolled is placed on the insert line 9.
The mandrel bar 2 is inserted into the mandrel bar 2. The hollow piece 8 into which the mandrel bar 2 is inserted is rolled by a mandrel mill 3 to form a pipe 1. In the rolled pipe 1, the distribution state of temperature change parts having a vertical striped pattern called a black stripe as shown in FIG. 5 is detected by the temperature change part distribution state detection device 4. The above-mentioned detection result is inputted to the arithmetic unit 16 and compared with a preset discrimination criterion to determine the presence or absence and size of the bite.

The result is fed back to the rolling control of the mandrel mill, and determines whether or not to activate the alarm 18 and whether or not to activate the popping device 15. The pipe 1 whose mandrel bar 2 is not pulled out by the burst stripper 17 on the strip line 10 and whose ear cracks are determined not to occur in the next rolling process is conveyed to the next process. Further, the mandrel bar 2 pulled out from the pipe 1 is cooled in the par cooling zone 11 and then returned to the insert line 9.

[Operation] The method of determining ear flaws in a pipe rolled by a mandrel mill in the present invention detects the distribution state of temperature change parts of the pipe rolled by a mandrel mill, and compares the distribution state of the temperature change parts with a preset discrimination criterion. Then, the distribution state of the characteristic temperature change part that causes a bite is determined, and the probability of inducing ear scratches is determined. Based on the determination result, an alarm is activated to notify the operator, or a pop-up device is activated. Then, the pipe can be carried out of the line, or it can be fed back to the rolling control to prevent ear cracks from occurring frequently.

[Example 1] An example of the present invention will be described below based on the drawings. FIG. 1 is an explanatory diagram showing an embodiment of the method for determining ear flaws in a pipe rolled by a mandrel mill according to the present invention. The pipe 1 is made of a hollow piece 8 punched by a punching machine 7. This hollow piece 8 is fed into the insert line 9 of the mandrel mill 3, where its temperature is measured by a temperature measuring device 12. The temperature measurement result from the temperature measuring device 12 is input to the arithmetic unit 16 . This temperature measurement is to confirm that the temperature is within a temperature range that can be rolled by the mandrel mill 3, and the hollow piece 8 at a low temperature that is difficult to roll is discharged out of the line. A mandrel bar 2 is inserted into the rollable hollow piece 8 . After this, roll 13 of mandrel mill 3 (fourth
(see figure) to form pipe 1. Here, the so-called black stripes, which are observed as a distribution of vertical stripes that appear on the pipe 1, have their intervals changed when biting occurs in the pipe 1 due to overfilling, and the intervals are not constant. Distribution state (Figure 5 (b)
)).

The distribution state of the temperature change area where the temperature is decreasing is as follows:
The distribution state of the temperature change section is measured by the distribution state detection device 4 disposed on the outlet side of the mandrel mill 3, and the distribution state of the temperature change section is inputted to the calculation device 16 and compared with a preset discrimination standard, Arithmetic device 1 discriminates whether or not chewing has occurred.
Execute by 6. When the pipe 1 is determined to have a chewing problem and the chewing is determined to induce ear scars, the arithmetic device 16 activates the alarm 18, the operator 19 activates the popping device 15 on the strip line 10, Alternatively, the alarm 18 is activated and the jump-out device 15 is activated to carry out the work out of the line, so that the effect of interruption of the rolling operation does not spread to the entire factory and cause a major hindrance.

In addition, feedback is provided to the rolling control in order to correct overfill and prevent frequent occurrence of ear scratches due to chewing.

21, the distribution state detection device 4 of the temperature change section is suitably a scanning radiation thermometer or a combination of a linear array camera and an image processing device.

The image information of the vertical striped pattern transmitted from the distribution state detection device 4 of the temperature change section to the calculation device 16 directly or via the sub-processing device f6 is subjected to contour processing, and then the number of pixels in the contour is measured, A comparison calculation is made with a preset reference value to determine whether or not ear flaws will occur in the next rolling process.

The distribution state detection device 4 of the temperature change section is provided with an outer diameter measuring device 5 in parallel to measure the outer diameters of the pipe 1 and the mandrel bar 2. It may be possible to obtain auxiliary data for determining whether the mandrel bar 2 is the mandrel bar or the mandrel bar 2. In this case, the data obtained from both the distribution state detection device 4 and the outer diameter measuring device 5 of the temperature change section are , - The data processed by the sub-processing device 6 may be input to the processing device 16.

Furthermore, from the length of the pipe 1 (Am) and the outlet speed of the mandrel mill 3 of the pipe 1 (V / air), the observation time (T w ) of the pipe 1 can be calculated as T (crown) = A (m) / V (Teng/
It can be replaced with the outer diameter measuring device 5 by computing the period Tsec from when the tip of the pipe 1 begins to be detected by the distribution state detection device 4 of the temperature change section as the pipe 1.

FIG. 6 shows an example of the results of measuring the temperature change in the states shown in FIGS. 5(a) and 5(b) using the detection device 4. The temperature of low-temperature parts A and B, which had a vertical striped pattern, of pipe 1 was 845 to 855°C, and the maximum temperature of the other shell parts was 930''C. The temperature drop is 66° C. From the change in the interval between A and B where the temperature has decreased in this way, it is possible to determine with extremely good accuracy whether or not there is a bite.

As a result, the distribution state of the temperature change part of the pipe 1 immediately after rolling is visually judged, and if there is any cracking, the pipe 1 causing ear cracks is carried out of the line by the popping device 15, and the rolling control is carried out. In order to provide feedback and prevent the occurrence of ear scratches, we will train skilled operators.
There is no need to arrange it on the rolling line. Also,
We have been able to completely eliminate ear flaws caused by biting, which previously occurred several thousand times a month.

Note that the present invention is not limited to the above embodiments,
Any design changes can be made within the scope of achieving the object of the present invention.

[Effects of the Invention] As described above, according to the present invention, cracks that occur in a mandrel-rolled pipe and resulting in ear cracks are identified in advance, carried out of the line, and fed back to the rolling control. Therefore, it is possible to prevent the occurrence of a large number of defective materials due to ear flaws. We also train skilled operators,
It has the advantage of being used in industry, such as eliminating the need to place it on a rolling line and making it possible to rationalize factors.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the method for determining ear flaws in a pipe rolled by a mandrel mill according to the present invention, and FIGS. 2 and 3 show a flowchart showing the processing procedure of the method for determining ear flaws and a control circuit. The block diagram, Figures 4(a) and (b) are explanatory diagrams showing the state of the pipe being rolled by the mandrel bar and the rolls arranged at 45 degrees to each stand of the mandrel mill, and Figure 5 is an explanatory diagram showing the state of the pipe rolled by the mandrel bar. An explanatory diagram showing the distribution state of the temperature change part of the pipe rolled in the mill, Figure 6 is a graph showing the actual measured value of the temperature change of the pipe, and Figure 7 is an explanatory diagram showing the outline of the equipment configuration of the mandrel mill. be. DESCRIPTION OF SYMBOLS 1... Pipe, 2... Mandrel bar 13... Mandrel mill, 4... Distribution state detection device of temperature change part, 5... Outer diameter measuring device, 6... Sub-computation device, 7 ...
Drilling machine, 8 Hollow piece, 9 Insert line, 10 Strip line, 11 Bar cooling zone, 12 Temperature measuring device, 13 Roll,
14... Shell stopper, 15... Jumping gear! ,1
6... Arithmetic device, 17... Burst stripper-118
... Alarm, 19... Operator, 20... Discrimination criteria, 21... Reheating furnace, 22... Stretch reducer, 23... Cooling bed.

Claims (1)

[Claims] The distribution state of vertical striped temperature change parts present in the pipe rolled by a mandrel mill is detected, and the presence or absence of bites that may cause ear cracks in the next rolling process is determined from the distribution state of the detected vertical stripe shaped temperature change parts. A method for determining ear flaws in a pipe rolled by a mandrel mill, the method comprising determining whether or not ear flaws occur.