JP2006231392A - Method for producing cast slab - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw detection scanning method and a method for producing a cast slab by using this flaw detection scanning method with which the optimum cutting-off position is decided from starting of the flaw detection with one sensor and the time till cutting off is made to drastically high speed. <P>SOLUTION: When the flaw of a cast steel material is detected, the flaw detection is performed from a prescribed starting position of the flaw detection to the longitudinal direction toward the inside from the end surface of the steel material, and at the position in the longitudinal direction that a shrinkage-pipe is not detected, the flaw detecting direction is changed into the width direction perpendicular to the longitudinal direction to perform the flaw detection. At the position in the width direction which detects the shrinkage pipe, the flaw detection is repeatedly performed by changing the flaw detecting direction into the longitudinal direction, and the longitudinal directional position where the shrinkage pipe is not detected over the whole width in the width direction, is decided as the cutting-off position and the steel material is cut off at this decided cutting-off position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a slab, and in particular, a method for manufacturing a slab for performing cutting by determining a cutting position where an internal defect (hereinafter referred to as a pipe) does not appear on the cut surface and the cutting amount is minimized. It is.

  Holes called pipes or mechanical pipes are formed in the uppermost part of the cast slab (the rearmost end part of the continuously cast slab, and the tip part is called the bottom) and the continuous joints of different steel types. FIG. 1 is a diagram schematically showing the topmost portion and the cutting position of a cast slab. The L direction is a longitudinal direction from the end face of the slab to the inside, and the C direction represents a direction orthogonal to the L direction, that is, a width direction of the slab. The large pipe 2 that can be the topmost portion 1 of the cast slab is called a primary pipe, and the pipe 3 that can be made elsewhere is called a secondary pipe. Since the primary pipe has large pores and causes cracks in the rolling process, the primary pipe is removed by cutting off the top portion. The space in the secondary pipe is vacuum, and is crimped and detoxified by hot rolling.

  In the current cutting operation of the top part, since the distribution state of the pipe is not known before cutting, the primary pipe or the secondary pipe often opens on the cut surface. The pipe portion 5 appearing on the cut surface 4 is oxidized, thereby causing a double crack during rolling. Therefore, when a pipe appears on the cut surface, the cutting is repeated until the pipe no longer appears on the cut surface.

  FIG. 1 (B) is a diagram schematically showing a case of cutting at the cutting position A1 shown in FIG. 1 (A). Since part of the primary pipe 2 remains and the pipe 5 appears on the cut surface, it is cut again. When the second cutting position is A3, the pipe does not appear on the cut surface, and the cutting operation is completed. However, in addition to the portion where the primary pipe is located, many good pieces are cut off, resulting in a decrease in yield. Furthermore, when the second cutting position is set to A4, the secondary pipe 3 appears on the cut surface. Therefore, the reason described above (the pipe portion appearing on the cut surface is oxidized, so that two sheets are rolled during rolling. This will cause re-cutting. Therefore, the yield is further lowered than the cutting at A3.

  For example, if the distribution situation of the pipe as shown in FIG. 1 can be known in advance, the cutting at A2 in FIG. It can be determined that it is the cutting position of the best vest. Furthermore, it is possible to cut off the primary pipe portion by a single cut without performing a plurality of cuts.

In order to solve such a problem, methods for measuring the presence or absence of a slab pipe as disclosed in Patent Document 1, Patent Document 2, and Non-Patent Document 1, for example, have been disclosed and developed so far. . In Patent Document 1, ultrasonic waves are transmitted to the slab by coupling by a local water immersion method after the slab is rolled into pieces, and the reflected wave from the bottom surface of the slab and the reflected wave from the inside are received to receive the pipe. In this method, the presence or absence is determined, the optimum cutting position is determined, and cutting is performed. Patent Document 2 and Non-Patent Document 1 transmit an ultrasonic wave to a slab using an electromagnetic ultrasonic probe, and receive a reflected wave from the inside of the slab by a reflection method or a transmission method. This is a method of flaw detection on pipes.
Japanese Patent Laid-Open No. 62-181817 JP-A-60-45372 Akihiro Kawashima; Electromagnetic Ultrasound Technology and its Applications, Nishiyama Memorial Technology Course, Japan Iron and Steel Institute, 76, 1981, p.229

  In the method described in Patent Document 1, the sensor is installed at an arbitrary position in the width direction as an example, and the length direction at an arbitrary position is obtained by scanning in the length direction or moving the slab in the length direction. The method of flaw detection is taken.

  FIG. 2 is an example of the result of investigating the shape of the pipe part of a continuous cast slab and its distribution in a front image by ultrasonic flaw detection, and the pipe part shapes of (A) and (B) are greatly different. Two types are given as examples. If the pipe has a flat shape in the C direction as shown in FIG. 2 (B), the cutting position can be determined by the method of Patent Document 1, but in practice the C direction as shown in FIG. 2 (A). There are also pipes that are so shaped that the so-called corners are elongated, and the flaw detection scanning method of Patent Document 1 is insufficient, and an optimal cutting position cannot be determined.

  Therefore, as disclosed in Patent Document 2, it is conceivable to apply a method of flaw-detecting the entire surface with one or a plurality of sensors. However, in the whole surface flaw detection method using one sensor, the flaw detection range is wide and the flaw detection time until the cutting position is determined may become long, resulting in a decrease in yield. Further, in the method of flaw detection using a plurality of sensors, although the flaw detection time can be shortened, there is a problem that the equipment burden for installing a plurality of sensors increases.

  If flaw detection is performed with one sensor and the time from the start of flaw detection to the cutting position and cutting can be dramatically increased, the equipment load can be reduced and the yield can be improved.

  As described above, many methods for detecting a pipe have been studied and developed. However, it is difficult to say that these are optimum flaw detection scanning methods for determining a cutting position.

  The present invention has been made in view of the above circumstances, and a flaw detection scanning method for determining the optimum cutting position from the start of flaw detection with a single sensor and dramatically speeding up the time until cutting, and this flaw detection scanning method. It aims at providing the manufacturing method of the slab using this.

  The invention according to claim 1 of the present invention uses a sensor for detecting a pipe having an internal defect generated at the topmost part of the slab, and at the position where the pipe is detected by the sensor, the slab is moved from that position. The sensor is moved toward the center of the longitudinal direction, which is the casting drawing direction, and at a position where the pipe is not detected by the sensor, the sensor is moved from that position to the slab width direction perpendicular to the longitudinal direction, and measurement is performed. When the pipe is not detected over the entire width of the slab when measuring by moving the sensor in the width direction, the longitudinal position is determined as the cutting position of the slab, and the cutting position is A slab manufacturing method comprising cutting a slab in a width direction to manufacture the slab.

  The invention according to claim 2 of the present invention is the casting slab manufacturing method according to claim 1, wherein the position at which measurement is started is determined from the relationship between the casting operating conditions and the pipe elongation position. It is a manufacturing method of a piece.

  The invention according to claim 3 of the present invention is the method for manufacturing a slab of claim 1, wherein the position in the width direction at which measurement is started is set to a position within 1/4 of the slab width from both sides of the slab. A method for manufacturing a slab characterized by being set.

  According to a fourth aspect of the present invention, in the method for producing a slab according to the first aspect, the measurement start position is determined from the shape of the crater end at the time of casting the slab. It is a manufacturing method.

  Further, according to a fifth aspect of the present invention, in the method for producing a cast piece according to any one of the first to fourth aspects, the sensor transmits a rectangular or elliptical ultrasonic beam to the steel material. And using an ultrasonic probe that receives a reflected wave from the inside of the steel material, scanning the ultrasonic probe in the long axis direction of the rectangular or elliptical ultrasonic beam, This is a method for producing a slab, which is a sensor that receives the reflected wave at different positions and detects the internal defect by delay-combining the reflected wave with a delay time corresponding to the received position.

  Since the present invention can use a single sensor to minimize the amount of good mass cutting and determine the cutting position at which the pipe does not appear on the cutting surface at high speed, the equipment load is reduced and the yield can be improved. It becomes possible.

A processing procedure example from the flaw detection scanning method to cutting according to the present invention is shown in the flowchart of FIG.
First, a flaw detection scanning start position is determined (S100). The starting position in the longitudinal direction (L direction) and the width direction (C direction) orthogonal to the longitudinal direction is preferably the position where the primary pipe is the longest. For this reason, for example, it is preferable to make a database beforehand regarding the relationship between the casting operating conditions and the pipe elongation position, and determine the position where the pipe is most likely to extend from the casting operating conditions by determining with a computer.

  Or you may determine from the shape of the crater end which is an unsolidified part in a slab. This is because the pipe generated at the top is caused by the fact that static pressure is not easily applied to the pipe when solidified in casting, and is based on the knowledge of the present inventors that the pipe has a close relationship with the crater end shape.

  In the crater end shape obtained from the heat transfer calculation or the crater end detection sensor, the flaw detection start position is defined as the direction position orthogonal to the longitudinal direction in which the unsolidified portion extends most to the bottom side (see FIG. 9). In order to prevent the search from converging on the secondary pipe 3 shown in FIG. 1, the flaw detection start position in the longitudinal direction is preferably detected from the position closest to the top as much as possible.

  When the flaw detection scanning start position is determined, the sensor is moved to this position (S101), and preparation for flaw detection is performed. Then, flaw detection is started in the longitudinal direction from this flaw detection start position (S102), the presence or absence of a pipe is determined (S103), and the process of returning to S102 is repeated until there is no pipe.

  Then, flaw detection is performed in the direction perpendicular to the longitudinal direction at the position where the pipe disappears (S104). Here again, as in the longitudinal direction, the presence or absence of a pipe is determined (S105), and the process of returning to S102 is repeated until there is no pipe. As a result of flaw detection in the direction orthogonal to the longitudinal direction, if no pipe is detected in the full width, the longitudinal position is determined as the cutting position (S106).

  After the cutting position is determined, this cutting position is output to the output device (S107), and the slab is cut with a cutting machine (not shown) at the previous cutting position (S108), from cutting position search to cutting. A series of processing ends.

  As a flaw detection method, when a pipe is detected by performing a flaw detection scan in the width direction (C direction) perpendicular to the longitudinal direction at a longitudinal position where the pipe is not detected, the specimen is detected in the longitudinal direction. Any flaw detection method that repeats flaw detection in the longitudinal direction may be used. Depending on the method of flaw detection scanning in the C direction, that is, sensor movement and flaw detection scanning, for example, there are methods as shown in FIGS. FIG. 5A shows a method in which priority is given to flaw detection scanning on the right side in the C direction. FIG. 5B shows a method in which the full width flaw detection scanning is performed once returning to the left end, and FIG. 5C returns to the closer end. In this method, flaw detection scanning is performed in the opposite direction (inner side), where 6 indicates a flaw detection start position and 7 indicates a cutting position. As shown in the figure, it can be seen that the flaw detection path on the way is different even when starting from the same start position and finally reaching the same cutting position.

  In the above description, the top portion of the slab has been described as an example. However, the present invention can be applied to the bottom portion, more specifically, a cut portion in the middle. In the best mode for carrying out the present invention, the measurement is started from the scanning in the longitudinal direction. However, the measurement may be started from the scanning in the width direction, and the present invention is not limited to this.

  FIG. 6 is a schematic diagram illustrating an example of a specific configuration of the flaw detection apparatus. An arbitrary waveform is created by the pulser 10 whose pulse repetition frequency can be arbitrarily changed, and an ultrasonic wave is incident on the subject from the probe 15. The pulse repetition frequency is set so that reverberation remains in the subject and the measurement waveform is not affected.

  A signal reflected from the surface or the inside of the subject is received by the probe 15, filtered and signal amplified by the receiver 11, converted into digital information by the A / D converter 12, and taken into the computer 13. The probe 15 is attached to a scanning mechanism 14 having a rectangular sound wave transmission / reception surface and capable of scanning in a direction parallel to the short side. The scanning mechanism 14 operates in response to a signal from the computer 13, scans the subject while transmitting and receiving ultrasonic waves, and receives the ultrasonic waveform received at a set time or position interval to the computer 13. take in. The computer 13 synthesizes the acquired ultrasonic waveform by correcting the propagation time so as to obtain the same effect as that measured by the probe having the set aperture synthesis width and focal length. The ultrasonic probe and the subject are acoustically coupled by the water column ultrasonic method (local water immersion method). In addition, the calculator 13 is connected to an input interface 16 for inputting flaw detection conditions and a display unit 17 for displaying flaw detection results, cutting positions, and the like.

  FIG. 7 is a flowchart showing a series of processing flow from flaw detection scanning to cutting. The basic processing flow is the same as that shown in FIG. 4, but an example is shown in which the method shown in FIG. 5C is adopted for flaw detection in the C direction. Hereinafter, the L direction is the longitudinal direction, the C direction is a direction orthogonal to the longitudinal direction, W is the slab width, Lo is the flaw detection start position in the L direction (length direction), Xo is the flaw detection start position in the C direction (width direction), dy represents the flaw detection pitch in the L direction, dx represents the flaw detection pitch in the C direction, Ys represents the flaw detection position in the L direction, and Xs represents the flaw detection position in the C direction.

  First, the flaw detection start position is determined. FIG. 3 shows a summary of the positions of the longest end of the primary pipe in the L direction and the C direction by the inventors examining the shape of the pipe. From FIG. 3, it can be seen that the pipe longest end position in the C direction is divided into two quarters of the slab from both sides except for one point. Based on this result, in the example, the C direction flaw detection start position Xo was set to a position of 1/4 W or 3/4 W of the slab width. As for the L direction flaw detection start position Lo, the longest pipe position exists in a wide range in the L direction, so it is preferable to perform flaw detection from the top as much as possible.

  When the flaw detection start position is determined, flaw detection is started. First, (1) flaw detection scanning is performed for every dy in the L direction from the flaw detection start position (Xo, Lo) until no pipe is detected. When the pipe is exhausted, the flaw detection scanning in the L direction is stopped, and (2) the flaw detection in the C direction is started at the current L direction position. At this time, the flaw detection in the width direction starts the flaw detection in the C direction by moving the sensor to the closer slab end. For example, assuming that the position where the pipe disappears in (1) is (Xp1, Yp1), and if the following expression (1) is satisfied, −Xp1 is moved in the C direction and flaw detection is started in the + C direction. If the expression (1) is not satisfied, it is moved by W−Xp1 in the C direction, and flaw detection is started in the −C direction.

Xp1 ≦ W−Xp1 (1)
The flaw detection scanning is performed until the pipe is detected every dx in the C direction. If a pipe is detected, the position (Xo, Yo) is set as (Xo, Yo) and the above processes (1) and (2) are performed.

  (3) If the pipe is not detected for the entire width, the flaw detection position in the L direction at this time is determined as the cutting position where the amount of good mass cutting is minimized and the pipe does not appear on the cut surface. It becomes.

  (4) Output this cutting position to an operator or an automatic cutting machine to cut the slab.

  It becomes possible to determine the optimum cutting position at high speed at high speed by the procedures (1) to (4) described above, and to remove the topmost part by one cut-off.

  A sensor was attached to a scanning mechanism capable of scanning in the L direction and the C direction, and flaw detection scanning and cutting position determination were performed according to the flowchart of FIG. In this example, a sensor for detecting the presence or absence of a pipe by transmitting and receiving sound waves to and from the slab by a local water immersion ultrasonic method was attached.

  The ultrasonic probe used in this example has the same effect as that measured by a probe having a transducer shape of 50 mm × 10 mm, a frequency of 1 MHz, a transducer shape of 50 mm × 50 mm, and a focal point of 115 mm. The aperture synthesis calculation was performed so that

  For a cast slab having a width of 1360 mm and a thickness of about 230 mm, the flaw detection start position was 350 mm in the L direction and 340 mm corresponding to 1/4 W in the C direction. The flaw detection speed was 100 mm / sec in both the L and C directions, and the flaw detection scanning pitch was dx = 1 mm and dy = 10 mm. FIG. 8A shows the flaw detection scanning trajectory and the determined cutting position. Here, 6 indicates a flaw detection start position and 7 indicates a cutting position. As a result, a position of 670 mm in the L direction from the topmost part was determined as the optimum cutting position.

  FIG. 8 (B) shows the result of examining the distribution status of the pipes by flaw detection on the entire surface. It can be seen from FIG. 8B that the amount of good mass cut can be minimized from the optimum cutting position. As a result of cutting at the determined position, it was possible to cut off the top part by one cutting without the pipe appearing on the cut surface.

It is the figure which represented typically the top part of the casting slab. It is the figure which represented typically the front image by the ultrasonic flaw which shows the shape of the pipe part of a continuous cast slab, and its distribution condition. It is the figure which put together the position of the L direction of the primary pipe longest end, and the C direction. It is a figure which shows the example of a process sequence from a flaw detection scanning method to cutting | disconnection. It is a figure which shows the difference in a flaw detection scanning method. It is a block diagram which shows an example of the specific structure of a flaw detection apparatus. It is a figure which shows a series of processing flows in an Example. It is a figure which shows the result of having investigated the locus | trajectory of a flaw detection scanning, the determined cutting position, and the distribution condition of a pipe. It is a figure explaining the flaw detection start position by a crater end shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Top part 2 Primary pipe 3 Secondary pipe 4 Cutting surface 5 Open pipe 6 Flaw detection start position 7 Cutting position 10 Pulsar 11 Receiver 12 A / D converter 13 Computer 14 Scanning mechanism 15 Probe 16 Input interface 16
17 Display

Claims (5)

Using a sensor that detects pipes with internal defects that occur at the top of the slab,
At the position where the pipe is detected by the sensor, the sensor is moved from that position toward the center in the longitudinal direction that is the casting drawing direction of the slab, and at the position where the pipe is not detected by the sensor, the position is Move the sensor in the slab width direction perpendicular to the longitudinal direction and repeat the measurement,
When measuring by moving the sensor in the width direction, when the pipe is not detected over the entire width of the slab, the longitudinal position is determined as the cutting position of the slab,
A method for producing a slab, comprising producing a slab by cutting the slab in the width direction at the cutting position. In the manufacturing method of the slab of Claim 1,
A method for producing a cast slab, characterized in that a position to start measurement is determined from a relationship between a casting operating condition and a pipe elongation position. In the manufacturing method of the slab of Claim 1,
A method for manufacturing a slab, characterized in that the position in the width direction at which measurement is started is set to a position within ¼ of the slab width from both sides of the slab. In the manufacturing method of the slab of Claim 1,
A method for producing a slab, characterized in that a position to start measurement is determined from a shape of a crater end at the time of casting the slab. In the manufacturing method of the slab in any one of Claim 1 thru | or 4,
The sensor transmits a rectangular or elliptical ultrasonic beam to the steel material, and uses an ultrasonic probe that receives a reflected wave from the inside of the steel material. The ultrasonic probe is scanned in the long axis direction, the reflected wave at a different position in the scanning direction is received, and the reflected wave is delayed and synthesized by a delay time corresponding to the reception position to eliminate internal defects. A method for producing a slab characterized by being a sensor for detection.