JP2002207028A - Flaw discriminating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flaw discriminating method for accurately discriminating whether the bad effect of flaw in a material to be inspected such as a square billet or the like is present by performing ultrasonic flaw detection with respect to the flaw generated in the material to be inspected. SOLUTION: The flaw echo reflected from the flaw in the square billet and the reflected echo transmitted through the flaw and reflected from the opposed surface are received and the flaws in the lattice blocks, which are formed by dividing the cross section of the square block, are detected. When the flaw is continuously recognized in the same block in the longitudinal direction of the billet, the flaw is recognized as one flaw and the length thereof is calculated and, when the length of the flaw is a prescribed value or more or the intensity of the flaw echo at every length position of the flaw is a prescribed value or more, the flaw is discriminated as a harmful flaw and, when the length of the flaw and the intensity of the flaw echo are below prescribed values, the phase of the flaw echo is compared with the phase of the reflected echo and, when the number of the phases discriminated to be the same is more than the number of the phases discriminated to be opposite, the flaw is discriminated as a harmful one and, in the case of opposite, the flaw is discriminated as a harmless one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic pulse which is incident on a material to be inspected such as a square billet, receives an echo reflected by the material to be inspected, and harms a defect inside the material to be inspected based on the received echo. The present invention relates to a defect discrimination method for discriminating the presence or absence of a defect, and particularly to a defect discrimination method for accurately discriminating defects such as nonmetallic inclusions and porosity.

[0002]

2. Description of the Related Art Steel slabs such as blooms and billets are mainly subjected to inspection and removal of surface flaws by overheating a steel ingot in an equalizing furnace, rolling it in a blooming mill, and then shearing it with a shearing machine. It is a semi-finished product manufactured by performing partial care, and the quality of the billet directly affects the product quality. For example, when internal defects such as internal cracks, internal voids called porosity, and non-metallic inclusions are present inside the steel slab, adverse effects such as a decrease in mechanical properties and cold workability may be caused.

[0003] In the rolling process, which is a downstream process, relatively small porosity does not adversely affect the quality of a final product because it is pressed and disappears, but large porosity and non-metallic inclusions are not affected. It remains in the final product and adversely affects the quality and is harmful. Therefore, in order to keep the quality of the final product good, it is necessary to remove steel pieces having harmful internal defects during the process.

Therefore, conventionally, the defect distribution in the cross section and the longitudinal direction of the steel slab has been subjected to ultrasonic flaw detection using a saddle-shaped flaw detection head in which a plurality of probes are arranged at equal intervals. A method of discriminating the type of a defect has been carried out by performing a macro / micro microscope inspection of a cross section after cutting, or making a judgment by a skilled person using a flaw detection chart in which an ultrasonic flaw detection state is recorded.

[0005] Japanese Patent Application Laid-Open No. 1-297551 proposes a method for discriminating the type of a defect without performing a microscopic examination of a cross section of a square steel and making a judgment by a skilled person. That is, the defect distribution in the surface layer and the center of the square steel is inspected in a predetermined length unit in the longitudinal direction of the square steel, the center continuity indicating the number of continuous defects that appear continuously at the center, and the total number of defects at the center. This is a method of discriminating a defect type based on a center accumulation degree indicating the number, a surface layer cross-section density indicating the distribution of defects in the surface layer of the cross section, and a center cross-section density indicating the distribution of defects in the center portion of the cross section.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 1-297551, when defects are internal cracks and porosity, a high quality rolled structure can be obtained by crimping during rolling. Discriminated as a defect type. On the other hand, when non-metallic inclusions are present as defect species, the non-metallic inclusions are harmful because they do not reduce the size and cause a reduction in cold workability, but they cannot be accurately distinguished. .

The following method has been proposed in Japanese Patent Application Laid-Open No. 4-118555. That is, a plurality of probes are arranged around the square steel at equal intervals, and the flaw detection areas by the probes are combined to form a rectangular defect determination block in the cross section of the square steel. Then, the ultrasonic pulse is applied across the corner of the square steel 2
After entering the square steel from the direction, the echo reflected from the square steel defect is amplified, and if any of the ultrasonic pulses in the two directions has a large echo intensity, the level of the echo on the monitor device, and the ultrasonic propagation time or The propagation distance is displayed on the rectangular coordinate axis. Further, the difference between the defect echoes due to the ultrasonic pulses in two directions is obtained. If the difference is within ± 6 dB, the defect is discriminated as a harmful nonmetallic inclusion, and if it exceeds ± 6 dB,
That is, if any one of the defect echoes goes to a lower level, it is discriminated as harmless internal crack and porosity.

In the case of non-metallic inclusions, the same level of defect echo can be obtained in both directions since the defect is spherical and has no directivity. However, in the case of internal cracks and porosity, linear defect with strong directivity is obtained. Therefore, the fact that one of the levels of the defect echo is lowered is used.

[0009] In addition to the method disclosed in the above-mentioned publication, an ultrasonic pulse is incident on the square steel from a predetermined direction, and a surface echo reflected on the surface of the square steel and a defect echo reflected on an internal defect are received. There is a method of discriminating the type of defect by determining whether the phases of the received surface echo and defect echo are the same.

[0010]

SUMMARY OF THE INVENTION
In the method disclosed in JP-A-118555, when the defect is a non-metallic inclusion thinly stretched by billet rolling, the level of the defect echo becomes lower in one of the two directions in the above-described apparatus. There is a risk of mis-discrimination as being internal cracks or porosity.

A method of discriminating the type of a defect based on the phase of a defect echo has not been put to practical use because non-metallic inclusions are sometimes discriminated as having porosity.

In the method disclosed in Japanese Patent Application Laid-Open No. Hei 4-118555, when the defect is a nonmetallic inclusion thinly stretched by billet rolling, it is erroneously determined that the defect is an internal crack or porosity. To prevent discrimination,
Finding that by combining the longitudinal length of the defect and the highest echo intensity within the range, it is possible to discriminate between a practically harmless microporosity defect and a practically harmful nonmetallic inclusion or harmful porosity. I got

When the defect is a non-metallic inclusion, it can be discriminated as harmful because it extends in the longitudinal direction due to billet rolling but does not crimp, and the indicated length increases. In the case of a defect having a high echo intensity, it can be discriminated that the defect is more harmful than the fact that the porosity is not crimped even in the rolling step of the secondary processing even if the porosity is high.

Further, in the method of discriminating the type of a defect based on the phase of a defect echo, the present inventor discriminates non-metallic inclusions as porosity by using non-metallic inclusions with bubbles thinned by rolling. In the case of an object, a defect echo reflected at the bubble portion may be received depending on the flaw detection direction. At that time, since the signal of the opposite phase caused by the bubble, that is, the porosity is large, the signal of the same phase caused by the nonmetallic inclusion is received. Investigating countermeasures based on the finding that the concealment is hidden and misidentified as porosity, the ultrasonic echo is incident on the square steel from multiple directions and the defect echo is received, and the defect echo received one direction at a time It has been found that the discrimination can be made with high accuracy by judging the phase.

The present invention has been made based on the above findings, and a defect capable of accurately discriminating harmful defects based on the longitudinal length of the defect, the intensity of the defect echo, and the phase of the defect echo. The purpose is to provide a discrimination method.

[0016]

According to a first aspect of the present invention, there is provided a defect discriminating method in which an ultrasonic pulse is applied to a rectangular column-shaped material to be inspected, and a defect echo reflected by a defect inside the material to be inspected is received. A defect discrimination method for discriminating the presence or absence of harm of a defect inside a material to be inspected on the basis of the defect echo obtained, the plurality of positions distributed in the width direction of the side surface and the plurality of positions distributed in the width direction of the side material. Ultrasonic pulses are respectively incident on a plurality of positions, and for each ultrasonic pulse incident from each direction, the defect echo reflected by the defect inside the inspected material and the defect are transmitted to the inspected material and the outside. The reflected echo reflected by the interface is received, and based on the reception position and the beam path of the defect echo, the position of the defect in the cross section of the inspection material is divided into a plurality of blocks in a cross section in a grid. Specific block Detected as, the defect in the longitudinal direction in which the block is the same, calculate the length in the longitudinal direction as one defect, compare the calculated length in the longitudinal direction with a predetermined length value, The intensity of the reflected defect echo is compared with a predetermined intensity value, the phase of the defect echo reflected by the defect and the phase of the reflected echo transmitted through the defect are compared, and the length in the longitudinal direction and the predetermined length are determined. Based on the comparison result, the result of comparing the intensity and the predetermined intensity of the defect echo, and the number of phases determined to be the same phase and the number of phases determined to be the opposite phase by comparing the phases, the defect is detected. It is characterized by discriminating the presence or absence of harm.

In the defect discrimination method according to the present invention, ultrasonic pulses are incident on a plurality of positions distributed in the width direction of the side surface and a plurality of positions distributed in the longitudinal direction from a plurality of side surfaces of the material to be inspected such as a square billet. Then, based on the beam paths of the plurality of defect echoes reflected by the defect and the positional relationship of the probe receiving the defect echo, the occurrence of defects in the inspection target material in the lattice-shaped block having the cross section of the square billet divided. Detects the corresponding position, and in the longitudinal direction of the square billet,
When defects are continuously recognized in the same block, the continuous defects are recognized as one defect, and the length is calculated.

The length of the one defect is not less than a predetermined length;
Alternatively, when the intensity of the defect echo is equal to or more than a predetermined value, the defect is discriminated from the defect to be harmful. A harmful defect whose calculated length is greater than or equal to a predetermined value or whose derived defect echo intensity is greater than or equal to a predetermined value is a large non-metallic inclusion or porosity.

If the length of the one defect is less than a predetermined value and the intensity of the defect echo is less than a predetermined value, the phase of the defect echo reflected by the ultrasonic pulse and the inspection material passing through the defect and The interface with the outside, that is, the phase of the reflected echo reflected on the surface opposite to the incident surface of the ultrasonic pulse is compared with each other, and the number of phases determined to be the same phase is determined to be the opposite phase. If the number is greater than or equal to, the defect is discriminated from the defect to be harmful, and if the number of phases determined to be in phase is smaller than the number of phases determined to be opposite phase,
The defect is distinguished from the defect that should be harmless.

When the ultrasonic pulse incident on the material to be inspected is reflected by a defect caused by porosity, the phase is inverted at the interface between the metal layer of the material to be inspected and the porosity.
When reflected by a defect caused by a non-metallic inclusion, the defect echo reflected at the interface between the metal layer of the ultrasonic pulse inspection material and the non-metallic inclusion does not reverse in phase, and has the same phase as the reflection echo. Utilizing that, it is discriminated whether the defect is non-metallic inclusions or porosity, if the defect is non-metallic inclusions, the defect is determined to be harmful, if the defect is porosity, The defect is determined to be harmless.

At this time, in order to prevent the ultrasonic pulse from being reflected at the porosity for the defect caused by the non-metallic inclusion with the porosity, and to prevent the defect from being erroneously discriminated as having the porosity, the inspection target material is inspected. Ultrasonic pulses were incident from multiple directions, and the number of phases determined to be in phase as a result of comparing the number of obtained defect echoes and reflection echoes with the same phase and the number of opposite phases was compared. If the number of phases is equal to or greater than the number of phases determined to be opposite phases, the defect is discriminated as a non-metallic inclusion, thereby reducing the risk of mis-discrimination.
The accuracy of discrimination can be improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an apparatus for carrying out the method of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an apparatus to which the defect discrimination method of the present invention is applied. In the figure, reference numeral 1 denotes a cross section in a direction perpendicular to the longitudinal direction of a square billet, which is a square pillar-shaped inspection material, and the square billet 1 is conveyed at a constant speed in the longitudinal direction.

Around the angular billet 1, four sets of probe groups 2a, 2b, 2c, 4c are provided so that ultrasonic pulses can be incident on the angular billet 1 from the directions with respect to the four sides which are the side surfaces of the angular billet 1.
And 2d are arranged respectively, and each probe group 2a, 2d
Each of b, 2c and 2d is composed of a plurality of probes. Ultrasonic pulses are incident from at least two directions. In the case of the angular billet 1 in two different directions, it is desirable that the light is incident from two adjacent orthogonal side surfaces. This is because a defect having directionality in the vertical and horizontal directions can be accurately detected on the cross section of the square billet 1. Further, it is more desirable that the light is incident from two opposite side surfaces. Even when the distance from the surface of the angular billet 1 to the defect is large, the defect detection sensitivity can be increased, and when the porosity and the nonmetallic inclusion are present together, the defect detection sensitivity can be increased. Because you can.

Each of the probe groups 2a, 2b, 2c and 2d receives a transmission pulse transmitted from the pulser 3 and selectively supplies the received transmission pulse to each probe sequentially. 4 are connected, and each probe group 2
The probes constituting a, 2b, 2c, and 2d sequentially transmit ultrasonic pulses to the angular billet 1 based on the transmission pulses supplied from the demultiplexer 4.

The defect echo reflected by the defect inside the angular billet 1 with respect to the incident ultrasonic pulse and the reflection echo transmitted through the defect and reflected by the surface opposite to the incident surface which is the interface with the outside are each: Probe groups 2a, 2b, 2
The probe groups 2a, 2b, 2c, and 2d are received by the probes constituting c and 2d, and the probe groups 2a, 2b, 2c, and 2d process the received defect echoes and reflection echoes with respect to signals received from a plurality of paths. Transmitted to the multiplexer 5, the multiplexer 5 transmits the received defective echo and reflected echo to the receiver 6 which amplifies the amplitude of the attenuated defective echo and reflected echo to a reference value, and the receiver 6 amplifies the amplitude to the reference value. The defect echo and the reflected echo are transmitted to the A / D converter 7.

The A / D converter 7 converts the received defect echoes and reflection echoes into digital signals, and converts the defect echoes and reflection echoes converted into digital signals into a defect discrimination device of the present invention for performing defect discrimination processing. Sent to 10.

The defect discriminating apparatus 10 is controlled by the CPU 11 and has connection means 12 for receiving defect echoes and reflection echoes converted into digital signals from the A / D converter 7, a memory 13, and output means such as a monitor and a printer. 14
It has.

The ultrasonic pulse incident on the angular billet 1 from the pulsar 3 via the demultiplexer 4 is transmitted not only to the demultiplexer 4 but also from the pulsar 3 to the connection means 12, and if necessary. Adjustment processing for adjusting the amplitude to the reference value and A / D conversion processing are performed. In addition, the ultrasonic pulse transmitted to the defect discriminating apparatus 10 via the connection means 12 is used as a trigger signal to synchronize with the defect echo, the reflected echo, and the ultrasonic pulse.

Further, the defect discriminating apparatus 10 includes the square billet 1
Defect position calculating means 15 for calculating the position of an internal defect, defect length calculating means 16 for calculating the length of a defect in the longitudinal direction of the angular billet 1, maximum intensity among a plurality of defect echoes reflected by one defect A maximum echo intensity calculating means 17 for deriving the defective echo, and a phase calculating means 18 for comparing the phases of the defective echo and the reflected echo.

The defect discriminating apparatus 10 may be constructed by using a general-purpose computer to configure each computing means with a software program. , It is possible to improve the operation speed, and furthermore, each of the probe groups 2a, 2b, 2c and 2d, the pulsar 3, the demultiplexer 4, the multiplexer 5, the receiver 6, and the A /
All or part of the D converter 7 may be incorporated.

The defect position calculating means 15 calculates the angular billet 1 based on the beam path and the probe positional relationship for a plurality of defect echoes reflected by each ultrasonic pulse incident on one defect from a plurality of directions. The position of the internal defect is detected as a specific block in the cross section of each billet 1 divided into a plurality of grid-like blocks.

FIG. 2 is an explanatory diagram showing an example of a corresponding block on the cross section of the square billet derived by the defect position calculating means used in the defect discrimination method of the present invention. In this example,
This shows an example in which it is determined that one block indicated by oblique lines has a defect, and the leftmost pulse of the received signal waveform is
The ultrasonic pulse shows the echo reflected on the incident surface, the rightmost pulse shows the reflected echo reflected on the surface opposite to the incident surface, and the center pulse shows the defect echo reflected on the defect. As shown in FIG. 2, when a defect exists inside the angular billet 1, not only the echo reflected from the incident surface and the reflected echo but also the defect echo are detected in the received waveform, and the ultrasonic pulse incident from a plurality of directions is detected. The block in which the defect exists is identified from the defect echo for the block.

The defect length calculating means 16 calculates the length pitch L determined by the transport speed C at which the angular billet 1 is transported in the longitudinal direction and the switching period f of the demultiplexer 4.
The length of the defect in the longitudinal direction of the angular billet 1 is calculated using (L = C / f). When an ultrasonic pulse is incident by one of the probes and a defect is detected by an ultrasonic pulse incident by one of the other probes before one probe again inputs the ultrasonic pulse. The corresponding block of the defect calculated by the defect position calculating means 15 is detected by the defect block detected by the ultrasonic pulse from one probe and by the ultrasonic pulse from the other probe. When the block of the defect is at the same position, it is recognized as a series of continuous defects and the defect length is calculated,
The defect length is calculated for each block of each cross section in a predetermined interval unit in the longitudinal direction of the square billet 1.

At predetermined intervals in the longitudinal direction, the maximum echo intensity calculating means 17 detects the amplitude of the received defect echo as echo intensity, and detects a plurality of defect echoes reflected by a series of consecutively recognized defects. From among the above, the echo intensity of a defect echo whose echo intensity is a predetermined condition, for example, the maximum is derived.

Threshold values are set in advance for the defect length calculated by the defect length calculating means 16 and the echo intensity derived by the maximum echo intensity calculating means 17, respectively. If at least one of the values exceeds the threshold value, it means that the size of the defect is large. Therefore, even if the porosity is high, there is a possibility that the defect is not pressed in the rolling process, and the defect is discriminated as a harmful defect.

FIG. 3 shows the defect length calculation means 16 and the maximum echo intensity calculation means 1 used in the defect discrimination method of the present invention.
7 is a graph showing a method of discriminating a harmful defect according to FIG. In FIG. 3, the horizontal axis represents the length of the defect calculated by the defect length calculating means 16, and the vertical axis represents the maximum echo intensity calculating means 1.
7 is taken. Lo in the figure
Indicates the threshold value of the defect length, and Io indicates the threshold value of the echo intensity. The hatched portion in the drawing is a region where at least one of the defect length and the echo intensity exceeds the threshold value, and the defect located in this region is discriminated as a harmful defect. Note that the white portions in the figure are regions where defects are to be discriminated by phase.

The phase calculating means 18 calculates the defect echoes reflected by the series of consecutive defects and the defect echoes received by the four probe groups 2a, 2b, 2c and 2d, respectively. Among them, the echo intensity is determined under predetermined conditions, for example, for each defective echo having the maximum in each set, by comparing with the phase of the corresponding reflected echo to determine whether the phase is the same or the opposite, respectively. The greater of the number of determined phases and the number of phases determined to be the opposite phase derives one of them, and discriminates the presence or absence of harm of a defect based on the derived phase.

FIG. 4 is an explanatory diagram showing waveforms used by the phase calculation means 18 used in the defect discrimination method of the present invention to discriminate whether or not a defect is harmful. FIG. 4A shows a waveform of a reflected echo reflected on a surface facing the incident surface, and FIGS. 4B and 4C show waveforms of a defect echo reflected by a defect.

FIG. 4B shows a waveform of a defect echo when the defect has porosity. As shown in FIG. 4B, when the defect has porosity, the phase is inverted.
The phase is opposite to that of the reflected echo shown in FIG.

FIG. 4C shows the waveform of a defect echo when the defect is a non-metallic inclusion. When the defect is a non-metallic inclusion as shown in FIG. The phase is not inverted, and becomes the same phase as the reflection echo shown in FIG.

FIG. 5 is an explanatory view conceptually showing a method of discriminating the presence or absence of harm of a defect having a low degree of harm by the phase calculating means 18 used in the defect discrimination method of the present invention. FIG.
As shown in FIG. 7, ultrasonic pulses are incident from the probes included in the probe groups 2a, 2b, 2c, and 2d from four directions on the side surface of the angular billet 1, and reflected by defects inside the angular billet 1. Each waveform is detected as a defect echo.

FIG. 5 shows a defect echo corresponding to the reflection echo reflected on the surface opposite to the surface on which the ultrasonic pulse shown in FIG. 4A is incident. The three defect echoes received by the probes included in the probe groups 2a, 2b, and 2c have the same phase, but the defect echoes received by the probes included in the probe group 2d have opposite phases. I have.

The defect is a non-metallic inclusion with a bubble, and the defect echo received by the probes included in the probe group 2d has a large signal of the opposite phase caused by the bubble, that is, the porosity. It is presumed that the signal of the same phase caused by the metal inclusion was hidden.

In the defect discrimination method of the present invention, the larger of the number of phases determined to be the same phase and the number of phases determined to be the opposite phase is derived, and based on the derived phase, the harm of the defect is determined. In order to determine the presence or absence, in the example shown in FIG.

FIG. 6 is a diagram showing an example of the result of determining the presence or absence of harm of a defect for each predetermined length in the longitudinal direction of the square billet 1 by applying the method of the present invention. The vertical line portion in FIG.
It is determined that the defect of the block corresponding to the defect position calculated by the defect position calculating means 15 is harmful by the defect length calculated by the defect length calculating means 16 and the echo intensity calculated by the maximum echo intensity calculating means 17. It shows an example of the result obtained. The horizontal line in FIG.
The defect of the block corresponding to the defect position calculated by the defect position calculating means 15 is calculated by the defect length calculated by the defect length calculating means 15, the echo intensity calculated by the maximum echo intensity calculating means 17, and the phase calculating means 18. Shows an example of a result determined that the defect is porosity and harmless.

Next, the defect discrimination processing in the defect discrimination method of the present invention will be described. FIG. 7 is a flowchart showing the defect discrimination processing. First, an ultrasonic pulse is incident on each of the four side surfaces of the angular billet 1 by the probe groups 2a, 2b, 2c, and 2d (step S1), and the incident ultrasonic pulse is reflected by the defect to generate a defect echo. Then, a reflected echo reflected by the surface facing the incident surface is received (step S2). The ultrasonic pulse is incident on the plurality of probe groups 2a distributed at predetermined intervals in the width direction of each side surface,
This is performed for a plurality of positions distributed at predetermined intervals in the longitudinal direction, as well as the positions corresponding to 2b, 2c, and 2d.

Based on the received defect echoes, for each defect, analysis processing such as calculation of a position, calculation of a length, derivation of a defect echo having the maximum intensity, and comparison of the phase with a reflected echo are performed. That is, the defect position is detected as a specific block from the beam path of the defect echo obtained by reflection and the position of the received probe (step S3). Square billet 1
In the case where defects are continuously detected in the same block in the longitudinal direction, the continuous defects are recognized as one defect (step S4), and the defect length is calculated for each predetermined section in the longitudinal direction (step S4). Step S5), it is determined whether the calculated defect length is less than a predetermined condition, for example, less than 30 mm (Step S6), and if it is determined that it is less than 30 mm (Step S6: Y), the defect length is determined. When it is determined that among the plurality of defect echoes used in the calculation, the maximum intensity defect echo having the maximum intensity indicated by the amplitude is less than a predetermined condition, for example, less than 80% of a preset reference value. (Step S7: Y), the phase of the defective echo is compared with the phase of the reflected echo (Step S8), and if the number of phases determined to be the same is smaller than the number of phases determined to be the opposite phase ( Step S9: Y), the defect is discriminated as being harmless (step S10).

When it is determined in step S6 that the length of the defect is 30 mm or more (step S6: N), or in step S7, the defect echo having the maximum intensity is 80% of the reference value.
When it is determined that this is the case (step S7: Y), the defect is discriminated as harmful (step 11). Also,
The number of phases determined to be in phase in step S9 is
If the number of phases is equal to or greater than the number of phases determined to be opposite phases (step S9: N), the defect is discriminated as harmful (step 11). Then, the analysis processing shown in steps S3 to S11 is performed on all the defects, and the results are output.

In the above embodiment, the square billet is shown as the material to be inspected. However, the present invention is not limited to this, and any material that can discriminate defects by ultrasonic pulses may be used. Further, in the above-described embodiment, the form in which the presence or absence of a defect is discriminated based on the defect echo having the maximum intensity is described. However, the present invention is not limited to this. It can be set arbitrarily such as an echo or an average value of the first to fifth intensities.

[0050]

As described in detail above, in the defect discrimination method according to the present invention, harmful defects and harmless defects inside the corner billet can be distinguished with high accuracy, and harmful defects can be detected with high accuracy. In addition, the present invention has excellent effects such as the quality of square billets and the quality of hot-rolled products using square billets as raw materials can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus to which a defect discrimination method of the present invention is applied.

FIG. 2 is an explanatory diagram showing an example of a corresponding block on a cross section of a square billet derived by a defect position calculating means used in the defect discrimination method of the present invention.

FIG. 3 is a graph showing a method of discriminating harmful defects by a defect length calculating means and a maximum echo intensity calculating means used in the defect discriminating method of the present invention.

FIG. 4 is an explanatory diagram showing waveforms used for discriminating whether or not a defect is harmful by a phase calculating means used in the defect discrimination method of the present invention.

FIG. 5 is an explanatory view conceptually showing a method of discriminating presence / absence of harm of a defect by a phase calculation means used in the defect discrimination method of the present invention.

FIG. 6 is a diagram showing an example of a result of applying the method of the present invention to determine the presence or absence of harm of a defect for each predetermined length in the longitudinal direction of a square billet.

FIG. 7 is a flowchart showing a defect discrimination process in the defect discrimination method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 square billet 2a, 2b, 2c, 2d probe group 3 pulser 4 demultiplexer 5 multiplexer 6 receiver 7 A / D converter 10 defect discriminator 11 CPU 12 connecting means 13 memory 14 output means 15 defect position calculating means 16 defect Length calculating means 17 Maximum echo intensity calculating means 18 Phase calculating means

Claims (1)

[Claims] 1. An ultrasonic pulse is applied to a material to be inspected in the form of a prism, receives a defect echo reflected by a defect inside the material to be inspected, and damages the defect inside the material to be inspected based on the received defect echo. In the defect discriminating method for discriminating the presence or absence of the ultrasonic pulse, ultrasonic pulses are respectively incident on a plurality of positions distributed in the width direction and a plurality of positions distributed in the longitudinal direction of the side surface from the plurality of side surfaces of the material to be inspected. For each ultrasonic pulse incident from the device, a defect echo reflected by a defect inside the inspection material and a reflection echo transmitted through the defect and reflected by an interface between the inspection material and the outside are received. Based on the receiving position and the beam path, the position of the defect in the cross section of the inspection material is detected as a specific block in the cross section divided into a plurality of grid-like blocks, and the longitudinal direction in which the block is the same is detected. The length in the longitudinal direction is calculated as one defect, and the calculated length in the longitudinal direction is compared with a predetermined length.The intensity of the defect echo reflected by the defect is calculated as a predetermined intensity. Compare the phase of the defect echo reflected by the defect and the phase of the reflection echo transmitted through the defect, and compare the longitudinal length and the predetermined length with the intensity and intensity of the defect echo. Based on the result of comparing the predetermined value and the number of phases determined to be the same phase and the number of phases determined to be the opposite phase by comparing the phases, the presence or absence of harm of the defect is distinguished. How to distinguish defects.