Patent Description:
For example, in a thick plate line of a steel mill, ultrasonic testing has been performed in a correction line before shipment to ensure quality of products that have been produced. The ultrasonic testing diagnoses whether defects, such as cracks, inclusions and segregations are present in products by transmitting ultrasonic waves to the products and receiving and analyzing the ultrasonic waves reflected from the products.

During the ultrasonic testing, gaps between surfaces of products and probes are filled with water and then ultrasonic waves are transmitted. Contact media are required to transmit ultrasonic energy oscillated from the probes to the products. Among the contact media, water is a representative medium with excellent ultrasonic transmission efficiency.

Meanwhile, thick plates having various thicknesses are being produced as products in a thick plate factory of a steel mill. Ultrasonic waves are scattered or absorbed while propagating inside metal, so their energy is reduced. The degree of reduction in energy varies according to frequencies of ultrasonic waves and a type and grain structure of metal.

In consideration of such ultrasonic attenuation, a standard of ultrasonic testing is established. For example, for products with a thickness of <NUM> or less, ultrasonic waves having a frequency of about <NUM> are applied, and for products with a thickness more than <NUM>, ultrasonic waves having about <NUM> are applied.

Accordingly, there is a problem in that a <NUM> ultrasonic tester and a <NUM> ultrasonic tester are separately provided for testing all products of various thicknesses, and need to be selectively used according to thickness. Usually, since an ultrasonic tester for testing a full width of a product is very expensive as the ultrasonic tester includes hundreds of ultrasonic sensors, signal processing arrays, and defect determination software, installing two testers requires a lot of money and manpower, and maintenance costs increase as the number of devices increases.

The document <CIT> relates to a nozzle for ultrasonic testing of materials in which water is coupled to ultrasonic energy and a method for employing the nozzle.

The document <CIT> relates to a probe arrangement for coupling ultrasonic signals to a component to be inspected by the water open jet method using a probe located in a jet nozzle and having a multiplicity of ultrasonic transmitting and/or receiving elements and at least one liquid inlet as well as at least one liquid outlet, where at least two of the transmitting and/or receiving elements are assigned to a single liquid jet and where the at least two ultrasonic signals are capable of being coupled to the component by the single liquid jet.

The document <CIT> relates to the detection of internal flaws in steel plates using an ultrasonic sensor installed in a nozzle which sprays a medium towards the inspected plate so as to form a medium column, wherein a detecting unit receives information regarding the thickness of the steel plate and controls a driving unit for adjusting the distance between the sensor and the plate according to said thickness information.

As related art, there is an invention disclosed in <CIT>. Further prior art documents are <CIT>, <CIT> and <CIT>. <CIT> discloses an ultrasonic testing apparatus comprising two probes for transmitting/receiving ultrasonic waves having different frequencies set according to the desired penetration depths, and a rotatable mirror installed between said probes so that ultrasonic waves from the probes are transmitted at different angles for scanning the tested object.

An aspect of the present invention is to provide an ultrasonic testing apparatus with a variable frequency capable of detecting internal defects in objects having various thicknesses by automatically changing the frequency according to thickness.

According to the present invention which is defined in claim <NUM>, an ultrasonic testing apparatus includes: a nozzle jetting a medium towards an object to form a medium column; and a plurality of probes disposed on the nozzle to oscillate an ultrasonic wave.

The ultrasonic testing apparatus further includes an ultrasonic reflector rotatably installed in the nozzle so that an ultrasonic wave of a probe selected from the plurality of probes is transmitted to the object.

According to an embodiment which is not encompassed by the claims but is considered as useful for understanding the invention, the ultrasonic testing apparatus may include a plurality of inlet waveguides branched from the outlet waveguide and having the plurality of probes distributed to each of the plurality of inlet waveguides, in which the nozzle is formed of one outlet waveguide.

As set forth above, according to the present invention, one ultrasonic testing apparatus may detect internal defects in all products having various thicknesses, so it is possible to greatly save installation and operation costs and manpower of the ultrasonic testing apparatus.

In addition, according to the present invention, one ultrasonic testing apparatus may test all products, so it is possible to more efficiently integrate and manage internal defects in products compared to the case where a plurality of ultrasonic testers are operated, to thereby improve quality and productivity of the products.

Hereinafter, the present invention will be described in detail with reference to the exemplary drawings. It is to be noted that in giving reference numerals to components of the accompanying drawings, the same components will be denoted by the same reference numerals even though they are illustrated in different drawings. Further, in describing exemplary embodiments in the present disclosure, well-known functions or constructions will not be described in detail since they may unnecessarily obscure the understanding of the present disclosure.

<FIG> is a diagram schematically illustrating an ultrasonic testing apparatus according to a first exemplary embodiment, <FIG> is a perspective view illustrating a main part of the ultrasonic testing apparatus according to said first exemplary embodiment, and <FIG> is a diagram for describing a control process of the ultrasonic testing apparatus according to said first exemplary embodiment.

As illustrated in these drawings, the ultrasonic testing apparatus according to the first exemplary embodiment includes a nozzle <NUM> and a plurality of probes <NUM>, <NUM>, and <NUM>.

The nozzle <NUM> may be installed on a lower side of an object <NUM> such as a thick steel plate conveyed by a conveyance means, for example, a guide roll <NUM>, and jet a medium <NUM> (for example, water) toward the object to form a medium column <NUM> (for example, a water column).

Such a nozzle <NUM> should be able to form a stable medium column <NUM> in close contact with a lower surface of the object <NUM>. To this end, an inner diameter of the nozzle is limited.

When the inner diameter of the nozzle <NUM> increases, a volume and mass of the medium column <NUM> increase, so a height of the medium column suddenly decreases. In addition, since a pulsation is formed inside the medium column, it becomes difficult to stably transmit ultrasonic waves.

On the other hand, when the inner diameter of the nozzle <NUM> is too small, as a testing area becomes small and a flow rate increases, a flow of the medium <NUM> becomes unstable, so it is not possible to stably transmit ultrasonic waves.

Accordingly, the relationship between an inner diameter d of the nozzle <NUM> and a width w or diameter of a probe surface needs to satisfy the following [Equation <NUM>]. In this case, the most stable ultrasonic testing is possible. Here, the probe surface refers to a surface on which the ultrasonic waves are substantially oscillated by the probe <NUM>.

In the ultrasonic testing apparatus according to the first exemplary embodiment, frequency switching is possible using one nozzle <NUM> having the inner diameter d of a correlation as in the above Equation <NUM> with respect to the width w or diameter of the probe surface.

The medium column <NUM> may be formed to have a height of several tens of millimeters (mm) from an outlet of the nozzle <NUM>, and the transmission and reception of ultrasonic waves is possible through this medium column. Since water is employed as a medium having excellent ultrasonic transmission efficiency, the medium column may be formed of a water column.

The ultrasonic testing apparatus according to the first exemplary embodiment may further include a medium circulation unit <NUM> that forms the medium column <NUM> by jetting the medium <NUM> from the nozzle <NUM>, recovering the medium falling from the medium column, and circulating the medium back to the nozzle.

The medium circulation unit <NUM> may include a medium receiver <NUM>, a recovery pipe <NUM>, and a supply pipe <NUM>.

The medium receiver <NUM> may be installed outside the nozzle <NUM> and may be configured to receive the medium <NUM> that has fallen from the medium column <NUM>. The medium receiver may be formed in a cylindrical shape or a box shape surrounding the nozzle.

The recovery pipe <NUM> may be connected to the medium receiver <NUM> and may be configured to recover the medium <NUM> in the medium receiver. The medium falling from the medium column <NUM> and collected in the medium receiver may be supplied to the recovery pipe.

A filter <NUM> for filtering the medium <NUM> discharged from the medium receiver <NUM> may be installed in the recovery pipe <NUM>, so the medium from which impurities have been removed may be re-supplied to the nozzle <NUM>.

The supply pipe <NUM> is for supplying the medium <NUM> of the recovery pipe <NUM> to the nozzle <NUM>, and may communicate with the nozzle <NUM> and the recovery pipe <NUM>, respectively.

A circulation pump <NUM> providing jetting pressure to the nozzle <NUM> may be installed between the recovery pipe <NUM> and the supply pipe <NUM>. The medium column <NUM> may be formed by allowing the nozzle to jet the medium <NUM> at a constant pressure according to the pressure provided by the circulation pump. By controlling the circulation pump, the jetting pressure of the nozzle may be controlled.

The plurality of probes <NUM> are disposed on the nozzle <NUM> to oscillate ultrasonic waves.

Specifically, each of the plurality of probes <NUM> may be fixedly installed to be spaced apart from each other on a sidewall of the nozzle <NUM>, and may transmit and receive ultrasonic waves for detecting internal defects in the object <NUM> through the medium column <NUM>. <FIG> illustrate an example in which two probes <NUM> and <NUM> are mounted symmetrically with respect to the nozzle.

The plurality of probes <NUM> oscillate ultrasonic waves having different frequencies. For example, one probe <NUM> may oscillate an ultrasonic wave having a frequency of about <NUM>, and the other probe <NUM> may oscillate an ultrasonic wave having a frequency of about <NUM>.

Each of these probes <NUM> may be connected to, through wired and wireless communication, a defect detection unit (not illustrated) that processes and calculates an ultrasonic signal received from the object <NUM> to analyze whether internal defects are present in an object.

In addition, the ultrasonic testing apparatus according to the first exemplary embodiment includes an ultrasonic reflector <NUM> that is rotatably installed between the plurality of probes in the nozzle so that an ultrasonic wave of a probe selected from the plurality of probes <NUM> is transmitted to the object <NUM>.

The ultrasonic reflector <NUM> may be made of, for example, a metal material such as stainless steel and brass, and thus, may smoothly reflect ultrasonic waves, and may not be corroded by the medium <NUM> such as water.

The ultrasonic reflector <NUM> is fixed to a rotation shaft <NUM> installed across the inside of the nozzle <NUM>, and the rotation shaft may be exposed to the outside through a sidewall of the nozzle <NUM>. A motor <NUM> installed outside the nozzle is connected to one end of the rotation shaft, so a rotation angle of the ultrasonic reflector may be controlled.

As such, the rotation angle may be controlled by the motor <NUM>, so the ultrasonic reflector <NUM> may selectively transmit ultrasonic waves oscillated from both probes <NUM> toward the object <NUM>.

A control process for automatically switching a frequency of an ultrasonic wave in the ultrasonic testing apparatus according to the first exemplary embodiment will be described with reference to <FIG>.

For example, in a correction line of the thick plate factory of the steel mill, a product which is the object <NUM> subjected to the ultrasonic testing is conveyed to the ultrasonic testing apparatus by the guide roll <NUM>. Before an object enters the ultrasonic testing apparatus, a main controller <NUM> constituting a factory operation system may receive thickness information of the object.

The main controller <NUM> may transmit the received thickness information to an on-off controller <NUM> for probe.

The on-off controller <NUM> for probe selects one of the plurality of probes <NUM> based on the thickness information of the object <NUM> to be subjected to the ultrasonic testing according to its internal program.

When the thickness of the object <NUM> is, for example, <NUM> or less, a command is transmitted to a first pulser receiver <NUM> corresponding to one probe <NUM> that oscillates an ultrasonic wave having a frequency of about <NUM> to operate the first pulser receiver <NUM> and stop an operation of a second pulser receiver <NUM> of the other probe <NUM>.

On the other hand, when the thickness of the object <NUM> exceeds, for example, <NUM>, a command is transmitted to the second pulser receiver <NUM> corresponding to the other probe <NUM> that oscillates an ultrasonic wave having a frequency of about <NUM> to operate the second pulser receiver <NUM> and stop the operation of the first pulser receiver <NUM>.

In addition, the main controller <NUM> transmits the received thickness information to a direction controller <NUM> for an ultrasonic reflector.

The direction controller <NUM> for the ultrasonic reflector controls a rotation angle of the ultrasonic reflector by operating the motor <NUM> according to the transmitted thickness information and switches an inclination direction of the ultrasonic reflector.

In other words, when the thickness of the object <NUM> is, for example, <NUM> or less, the inclination direction of the ultrasonic reflector <NUM> so that an ultrasonic wave having a frequency of about <NUM> oscillated from one probe <NUM> is reflected toward the outlet of the nozzle <NUM> and a lower surface of the object is changed.

On the other hand, when the thickness of the object <NUM> exceeds, for example, <NUM>, the inclination direction of the ultrasonic reflector <NUM> so that an ultrasonic wave having a frequency of about <NUM> oscillated from the other probe <NUM> is reflected toward the outlet of the nozzle <NUM> and the lower surface of the object is changed.

In the ultrasonic testing apparatus according to the first exemplary embodiment, the plurality of probes <NUM> oscillating ultrasonic waves having different frequencies are symmetrically mounted on the nozzle <NUM>, and by controlling the rotation angle of the ultrasonic reflector <NUM> located between the probes so that the ultrasonic wave of the selected frequency according to the thickness of the object <NUM> is transmitted to an object, the frequency of the ultrasonic wave may be automatically switched according to the thickness of the object.

Therefore, in the ultrasonic testing apparatus according to the first exemplary embodiment, it is possible to easily switch the frequency of the ultrasonic wave and to stably transmit/receive the ultrasonic wave.

<FIG> is a cross-sectional view illustrating a main part of an ultrasonic testing apparatus according to an embodiment which is not encompassed by the claims but is considered as useful for understanding the invention, and <FIG> is a diagram for describing a control process of the ultrasonic testing apparatus illustrated in <FIG>.

The embodiment illustrated in <FIG> and <FIG> is different from the first embodiment illustrated in <FIG> described above in terms of only the shape of the nozzle without the ultrasonic reflector and the motor and the arrangement relationship of the probes, and the remaining components are the same as those of the first embodiment. Therefore, the same components as those of the ultrasonic testing apparatus according to the first embodiment will be denoted by the same reference numerals, and a detailed description for configurations and functions of these components will be omitted.

In the ultrasonic testing apparatus illustrated in <FIG>, the nozzle <NUM> may be formed of one outlet waveguide <NUM> and branched from the outlet waveguide, and the plurality of probes <NUM> may further include a plurality of inlet waveguides <NUM> distributed to each of the plurality of probes <NUM>.

Each of the plurality of probes <NUM> may be installed inside the corresponding inlet waveguide <NUM>, and may transmit and receive ultrasonic waves for detecting internal defects in the object <NUM> through the medium column <NUM>.

As in the first embodiment described above, these probes <NUM> may oscillate ultrasonic waves having different frequencies. For example, one probe <NUM> may oscillate an ultrasonic wave having a frequency of about <NUM>, and the other probe <NUM> may oscillate an ultrasonic wave having a frequency of about <NUM>.

Each of these probes <NUM> may be connected to, through wired and wireless communication, the defect detection unit (not illustrated) that processes and calculates the ultrasonic signal received from the object <NUM> to analyze whether the internal defects exist in the object.

The ultrasonic waves oscillated from the probes <NUM> in each inlet waveguide <NUM> may be propagated out of the nozzle <NUM> through the outlet waveguide <NUM>.

The medium <NUM> may also be supplied to the inlet waveguide <NUM> through a branched supply pipe (not illustrated), and then may be jetted out of the nozzle <NUM> via the outlet waveguide <NUM> through a common path.

Preferably, the total reflection condition between the ultrasonic wave and the inner interface of the waveguide needs to be satisfied so that the ultrasonic wave introduced into the inlet waveguide <NUM> is propagated without loss in the outlet waveguide <NUM>. That is, the loss of ultrasonic energy in the waveguide needs to be minimized.

To this end, as in the following Equation <NUM>, an ultrasonic velocity V<NUM> in the medium in the waveguide needs to be smaller than an ultrasonic velocity V<NUM> in the inner interface of the waveguide.

Equation <NUM> may be satisfied when the medium <NUM> such as water is filled inside the waveguide, and the inlet waveguide <NUM> and the outlet waveguide <NUM> are made of a metal material.

In addition, since a curved or bent surface is formed at a portion in which the plurality of inlet waveguides <NUM> are coupled to one outlet waveguide <NUM>, an angle between the ultrasonic wave and the inner interface of the waveguide is changed.

In the portion in which the angle is changed as described above, that is, in the portion in which the plurality of inlet waveguides <NUM> are coupled to one outlet waveguide <NUM>, when the inlet waveguide and the outlet waveguide are designed so that an angle (incident angle: θ) between a propagation direction of the ultrasonic wave traveling from the inlet waveguide to the outlet waveguide and a direction perpendicular to the inner interface of the outlet waveguide is greater than a critical angle θc, the ultrasonic waves may be transmitted through the outlet waveguide without loss.

In other words, as in the following Equation <NUM>, when the ultrasonic waves are incident on the inner interface of the waveguide at the angle θ greater than the critical angle θc, the total reflection occurs.

Here, the critical angle may be expressed as in the following Equation <NUM>.

Therefore, in the ultrasonic testing apparatus illustrated in <FIG>, one outlet waveguide <NUM> and the plurality of inlet waveguides <NUM> constituting the nozzle <NUM> may be designed under the condition satisfying the above Equations <NUM> and <NUM>, and when the plurality of probes <NUM> selectively oscillate ultrasonic waves having different frequencies, the ultrasonic testing of the object <NUM> having various thicknesses becomes possible.

A control process for automatically switching a frequency of an ultrasonic wave in the ultrasonic testing apparatus illustrated in <FIG> will be described with reference to <FIG>.

For example, in the correction line of the thick plate factory of the steel mill, the product which is the object <NUM> subjected to the ultrasonic testing is conveyed to the ultrasonic testing apparatus by the guide roll <NUM>. Before the object enters the ultrasonic testing apparatus, the main controller <NUM> constituting the factory operation system may receive the thickness information of the object.

The main controller <NUM> may transmit the received thickness information to the on-off controller <NUM> for probe.

The on-off controller <NUM> for probe may select one of the plurality of probes <NUM> based on the thickness information of the object <NUM> to be subjected to the ultrasonic testing according to its internal program.

When the thickness of the object <NUM> is, for example, <NUM> or less, a command is transmitted to the first pulser receiver <NUM> corresponding to one probe <NUM> that oscillates an ultrasonic wave having a frequency of about <NUM> to operate the first pulser receiver <NUM> and stop the operation of the second pulser receiver <NUM> of the other probe <NUM>.

In the ultrasonic testing apparatus illustrated in <FIG>, each of the probes <NUM> oscillating ultrasonic waves having different frequencies may be mounted on the plurality of inlet waveguides <NUM> of the nozzle <NUM>, and the operation of the probe <NUM> may be selectively controlled so that the ultrasonic wave of the frequency selected according to the thickness of the object <NUM> is transmitted to the object through the outlet waveguide <NUM>, so the frequency of the ultrasonic wave may be automatically switched according to the thickness of the object.

Therefore, in the ultrasonic testing apparatus illustrated in <FIG>, it is possible to easily switch the frequency of the ultrasonic wave and to stably transmit/receive the ultrasonic wave.

As described above, the frequency of the ultrasonic wave may be automatically selected according to the thickness of the object and then the ultrasonic wave may be transmitted to the lower surface of the object through the nozzle, so the internal defects in objects having various thicknesses through one ultrasonic testing apparatus may be detected.

Claim 1:
An ultrasonic testing apparatus, comprising:
a nozzle (<NUM>) jetting a medium (<NUM>) towards an object (<NUM>) to form a medium column (<NUM>);
a plurality of probes (<NUM>, <NUM>, <NUM>) disposed on the nozzle (<NUM>) to oscillate an ultrasonic wave, wherein the plurality of probes (<NUM>, <NUM>, <NUM>) oscillates ultrasonic waves having different frequencies;
an ultrasonic reflector (<NUM>) rotatably installed between the plurality of probes (<NUM>, <NUM>, <NUM>) in the nozzle (<NUM>) so that an ultrasonic wave of a probe selected from the plurality of probes (<NUM>, <NUM>, <NUM>) is transmitted to the object (<NUM>), wherein the ultrasonic reflector (<NUM>) is fixed to a rotation shaft (<NUM>) installed across an inside of the nozzle (<NUM>), and a motor (<NUM>) installed outside the nozzle (<NUM>) is connected to one end of the rotation shaft (<NUM>);
a main controller (<NUM>) receiving thickness information of the object (<NUM>);
an on-off controller (<NUM>) for selecting a probe from the plurality of probes (<NUM>, <NUM>, <NUM>) based on the thickness information of the object (<NUM>) transmitted from the main controller (<NUM>);
a first pulser receiver (<NUM>) and a second pulser receiver (<NUM>) selectively oscillating an ultrasonic wave of a corresponding probe (<NUM>, <NUM>) according to a command of the on-off controller (<NUM>) for probe; and
a direction controller (<NUM>) for controlling a rotation angle of the ultrasonic reflector (<NUM>) by operating the motor (<NUM>) based on the thickness information of the object (<NUM>) transmitted from the main controller (<NUM>).