KR20220156398A - Stress-induced metastable martensite generation measurement system and measurement evaluation method on the surface of austenite stainless steel pipe products - Google Patents

Abstract

The present invention provides a system for measuring stress-induced metastable martensite generated on a surface of an austenitic stainless steel pipe product, which comprises: a probe including a probe coil which causes eddy current on the surface of an austenitic stainless steel pipe product subjected to cold working; an oscillator for applying AC power to the probe coil; and an impedance measuring device for measuring a change in impedance formed in the probe coil when the AC power is applied to the probe coil. The probe coil uses the change in impedance due to the change in magnetic permeability among the changes in the impedance induced in the probe coil due to the eddy current formed on the surface of the pipe product while receiving the AC power, thereby measuring the location and amount of metastable organic martensite formed on the surface of the pipe product.

Description

Stress-induced metastable martensite generation measurement system and measurement evaluation method on the surface of austenite stainless steel pipe products}

The present invention relates to a measurement system and a measurement evaluation method capable of evaluating whether and how much stress-induced metastable martensite is generated on the surface of a stainless steel tube product without destroying the tube product.

Among the representative steel grades of stainless steel, STS304 material has a metastable α'-martensite phase by plastic working even at a relatively low temperature.

The α'-martensite phase has high magnetic permeability compared to γ austenite, which is non-magnetic in STS 304.

In the final process, tubular products made of stainless material manufactured through drawing or welding are plastically processed while receiving external force from external rollers, etc., and go through an intuitive process in which straightness is improved. At this time, a metastable phase such as α'-martensite may be generated by plastic working on the surface structure of the tubular product to which an external force is applied, which may cause a magnetic change in magnetic permeability locally on the surface of the tubular product.

In this way, in order to determine whether the α'-martensite phase is generated externally through the intuitive process, and the location and amount of generation, conventionally, a method such as tissue observation to destroy and analyze the product has been used.

However, since this destructive analysis method is an analysis that is possible only after the process is finished, it is difficult to measure the quality in real time, and therefore, there is a problem in that it is impossible to immediately analyze and respond when a quality variable occurs in the process.

Publication No. 10-2017-0125038 (published date: 0217. 11. 13)

Therefore, according to the present invention, the accurate evaluation of the amount and location of martensite generated during cold working of an austenitic stainless steel pipe product is evaluated immediately during the cold working process, not after the process, so that feedback can be given immediately to the cold working process. It is intended to provide a martensite measurement system and measurement evaluation method.

The martensite measurement system according to the present invention for achieving this object includes a probe including a probe coil that generates eddy current on the surface of an austenitic stainless steel tube product subjected to cold processing, and an oscillator for applying AC power to the probe coil. And, an impedance measuring device for measuring a change in impedance formed in the probe coil when the AC power is applied to the probe coil, wherein the probe coil is formed on the surface of the stainless steel tubular product while receiving the AC power Position of formation of organic martensite, a metastable phase, formed on the surface of the stainless steel tube product during the cold working process by using the change in impedance due to the change in magnetic permeability among the change in impedance induced in the probe coil due to eddy current and measure the amount produced.

The probe coil is preferably formed with a larger diameter than the outer diameter of the stainless steel tube product, and the probe coil may be fixedly installed in a member having a hole through which the stainless steel tube product passes.

The member is a plate-shaped member, and preferably may be a probe coil fixing panel manufactured to be installed in a form in which the probe coil is inserted into the inner circumferential surface of the hole.

In addition, preferably, a reference sample for comparison having the same material and the same outer diameter as the austenitic stainless steel pipe product, formed to a certain length, and artificially formed with a certain size of stress-induced martensite on a part of the outer circumferential surface is further provided. can

At this time, preferably, a comparison probe composed of a comparison coil manufactured identically to the probe coil and a comparison coil fixing panel manufactured identically to the probe coil fixing panel is further provided, and the stainless steel pipe measured by the probe is further provided. The amount and position of martensite produced can be derived by comparing the martensite detection data of the product with the data measured by the comparison probe.

In addition, the probe coil and the comparison coil are preferably differentially connected to each other, so that when the probe coil scans the surface of the austenitic stainless steel tube product and detects a change in impedance due to a change in magnetic permeability, the comparison coil The amount of induced stress martensite generated corresponding to the impedance change value detected by the probe coil is calculated by finding the impedance change values of the two reference parts that are closest to the impedance change value detected by the probe coil while scanning the reference part. It can be.

Meanwhile, preferably, a rolling member is provided on an inner circumferential surface of the hole formed in the probe coil fixing panel to be spaced apart from the probe coil, and at least three rolling members are installed along the circumferential direction of the inner circumferential surface of the hole, so that the probe coil In a state where the tube product is extrapolated from the fixed panel to the probe coil fixed panel, the distance between the probe coil and the surface of the tube product is rapidly variable along the longitudinal direction of the tube product, while the distance between the probe coil and the surface of the tube product is spread over the entire circumferential direction of the tube product. can be kept constant.

In particular, the front or rear surface of the probe coil fixing panel is preferably a block-shaped member in which a hole identical to the hole is formed, and an expansion block extending the width of the hole is coupled, and the rolling member is installed on an inner circumferential surface of the expansion block. And, the extension block is also installed on the coil fixing panel for comparison.

Meanwhile, the martensite measurement and evaluation method according to the present invention prepares a martensite measurement system composed of a probe including a probe coil, an oscillator for applying AC power to the probe coil, and an impedance measurer for measuring a change in impedance of the probe coil. a step of extracting and preparing an austenitic stainless steel tubular product subjected to cold working in a cold working process; applying AC power to the probe coil by bringing the probe coil close to the tubular product; Inducing eddy current in the tube product, measuring the impedance change generated in the probe coil due to the eddy current, and measuring the impedance change to a portion where martensite is formed on the surface of the tube product The step of inferring the position and size of martensite formed on the surface of the tubular product by evaluating the impedance change value corresponding to the change in magnetic permeability caused by the.

Here, the step of applying AC power to the probe coil is preferably by inserting the probe coil into the center of the probe coil and then varying the probe coil along the longitudinal direction of the tube product, so that the probe coil is connected to the pipe. It may be performed in the form of scanning the product.

In addition, the step of preparing the martensite measurement system preferably further includes providing a reference sample for comparison, which is a tube product having the same shape and size as the tube product, and a coil for comparison manufactured identical to the probe coil, The step of applying AC power to the probe coil preferably further includes the step of inserting the reference sample for comparison into the center of the coil for comparison, and the step of inducing eddy current in the probe preferably Inducing an eddy current in the control product with a coil, and inducing an eddy current in the reference sample for comparison with the contrast coil, wherein the step of inducing an eddy current in the control product and the eddy current in the reference sample for contrast There is no temporal precedence relationship between the steps of inducing .

In addition, in the step of preparing the reference sample for comparison and the comparison coil manufactured identically to the probe coil, preferably artificially martensitic transformation is caused on the surface of the austenitic stainless steel tube product adopted as the reference sample for comparison. Further comprising forming a reference region that can be used as a reference in measuring the size and density of the martensite formation region formed in the cold working process in the tubular product inserted into the probe coil, wherein the reference region is different from each other. It may consist of a plurality of artificial martensitic transformation bands formed in length.

Particularly preferably, in the step of inferring, when a change in impedance is detected on the surface of the control product, the degree of change in impedance detected on the surface of the control product is greater than that of a plurality of reference parts formed on the reference sample for comparison. The step of specifying the nearest upper reference part, which is a reference part that shows the impedance change value closest to the degree of change in impedance detected on the surface of the object, and the contrast criterion that is smaller than the degree of change in impedance detected on the surface of the product A step of specifying a nearest lower reference part, which is a reference part showing a change in impedance that is closest to the degree of change in impedance detected on the surface of a test product, among a plurality of reference parts formed on the sample; and Evaluating the size, range, or density of martensite formed on the surface of the observation product by comparing and evaluating the degree of change in impedance of each of the contact sub-reference regions and the degree of change in impedance detected on the surface of the observation product. .

The martensite measurement system according to the present invention accurately evaluates the amount and location of martensite generated during cold working of austenitic stainless steel pipe products immediately during the cold working process, not after the process, so that it is suitable for the cold working process. It has the effect of giving immediate feedback.

1a is a conceptual diagram of straight cold working of an austenite tube product, which is a measurement target of a martensite measuring system according to the present invention;
Figure 1b is a photograph of the microstructure of martensitic transformation generated on the surface of austenitic stainless steel;
1c is a conceptual diagram of an impedance measurement curve;
1d is an impedance comparison graph according to the frequency of austenite and martensite;
1E is a comparison graph of a noise signal according to magnetic permeability and a noise signal according to other variables;
2a is a conceptual diagram of a martensite measuring system according to the present invention;
Figure 2b is a cross-sectional side view and a front view of the probe coil fixing panel in Figure 2a;
2c is a conceptual diagram of an oscillator and an impedance meter built into the case of FIG. 2a;
Figure 3a is a conceptual diagram showing a further embodiment of Figure 2a;
Figure 3b is a perspective view of the coil for contrast in Figure 3a;
Figure 3c is a conceptual diagram showing the measurement principle of the measurement system according to Figure 3a;
Figure 4a is a perspective view showing a further embodiment of the probe coil fixing panel in Figure 2a;
Figure 4b is a front view of Figure 4a;

Specific structural or functional descriptions presented in the embodiments of the present invention are merely exemplified for the purpose of explaining embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms. In addition, it should not be construed as being limited to the embodiments described in this specification, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and scope of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The martensite measurement system according to the present invention includes a transducer 20, an oscillator 10, and an impedance measurer 30 as shown in FIG. 2A.

The transducer 20 is provided with a transducer coil 21 that generates eddy current on the surface of the austenitic stainless steel tube product P on which cold processing has been performed, such as the direct process shown in FIG. 1A, and the transducer 20 ) is a variable measuring part that is not fixed in any one position.

The oscillator 10 applies AC power to the probe coil 21, and the impedance measurer 30 measures a change in impedance formed in the probe coil 21 when the AC power is applied to the probe coil 21. The oscillator 10 and the impedance measurer 30 are embedded in the case 60 in FIG. 2A and are not directly shown, and a conceptual diagram of the oscillator 10 and the impedance measurer 30 is shown in FIG. 2C.

The probe coil 21 calculates the change in impedance caused by the change in magnetic permeability among the change in impedance induced in the probe coil 21 due to the eddy current formed on the surface of the tube product P while receiving the AC power. It is configured to measure the production position and amount of organic martensite, which is a metastable phase formed on the surface of the tubular product P during the cold working process.

Here, the magnetic properties of martensite formed on the surface of austenitic stainless steel during the cold working process of the austenitic stainless steel will be briefly described, and then how these properties are used in the present invention will be described in turn.

The tubular product P, which is a steel pipe made of austenitic stainless steel, undergoes a straightening process as shown in FIG. 1A to increase straightness. When the austenitic stainless steel pipe product (P) undergoes cold working such as a straightening process, a metastable martensite phase is formed on the surface of the pipe product (P) due to plastic working even at a relatively low temperature.

Since the roll used in the straightening process is formed in a complex shape as shown in FIG. 1a, there is inevitably a local stress difference, and at this time, the greater the force applied by the roller to the surface of the tube product P, the more austenite is transformed into martensite amount may be increased.

As shown in the photograph of FIG. 1B, when plastic deformation is applied, the γ austenite material transforms into the α'-martensite phase, which is a metastable phase. According to the results of fracture analysis known through research, the martensite phase is tens of micrometers from the surface of the austenite material. It is known to be created by distributing to the depth of

Although martensite formed on the surface of austenitic steel is not clearly distinguished on the photograph, it is partially formed along the boundary of two parallel deformed twins or intensively formed along the slip band formed as dislocations move.

As described above in the background art, conventionally, in order to measure the generation position and amount of martensite formed in cold working, destructive analysis was performed and evaluated through histological examination. However, since such analysis and evaluation take a lot of time, it is difficult to immediately recognize and evaluate the occurrence of martensite in the cold working process in real time. It was impossible to deal with.

However, martensite has a very high magnetic permeability characteristic compared to austenite, which is non-magnetic. The present applicant paid attention to the fact that this difference in magnetic permeability can be measured by impedance.

That is, in the martensite measurement system according to the present invention, the change in impedance is measured by the eddy current test method among the conventional nondestructive test methods, and the change in impedance appears as a difference in magnetic permeability. It is configured to enable immediate evaluation of generation location and generation form.

Eddy current testing is a non-destructive testing technique that analyzes the state of a test object by inducing eddy current in the test object and observing the interaction between the current and the material.

In the eddy current test, when an alternating current flows through an induction coil, an alternating magnetic field is generated at the same frequency as the applied alternating current. When the coil is placed close to the tube wall, eddy currents are generated in the tube due to the alternating magnetic field electromagnetically, and these eddy currents This test detects the deterioration point and degree of deterioration of the tube by measuring the change in impedance, that is, by using the repulsive magnetic field generated by

In eddy current inspection, high-speed inspection is possible because the transducer does not come into contact with the test object and can be varied around the test object. Therefore, it is widely applied to non-destructive testing of nuclear power plant equipment that is harmful to inspectors, such as the surrounding operating environment may be exposed to radiation.

In the martensite measurement system according to the present invention, the measurement target is an austenite stainless tube product P as shown in FIG. 3 . At this time, the impedance curve as shown in FIG. 1c is obtained in the process of the probe coil 21 spaced apart from the tube product P approaching the surface of the tube product P.

The impedance curve of FIG. 1C obtained according to frequency is a curve indicated by a solid line at the bottom of FIG. 1D. At this time, when there is a site where austenite is transformed into martensite on the surface of the tubular product (P), the permeability of the metastable α'-martensite phase is hundreds of times higher than that of the γ austenite phase. Due to this, when martensite is generated, a significant impedance change can be observed.

Therefore, in the graph of FIG. 1D, the impedance change at the martensite formation site appears as an upper dotted line curve that is much larger than the lower solid line curve expressing the impedance change for austenite.

In addition, the eddy current inspection usually requires consideration of all factors that may affect the flow of eddy current or the impedance of the transducer 20 in order to obtain a practically reliable inspection result.

At this time, as shown in the graph of FIG. 1e, other variables (conductivity, geometry) that affect the impedance value are affected by the noise signal due to lift-off and other variables as the frequency decreases, as shown in (d) (e) (f). However, in the case of permeability change, even if the frequency changes, there is no change in the spread angle of the impedance line due to the permeability change, and it is oriented in the same direction. Therefore, the change in the impedance curve due to ambient conditions or other factors and the change in permeability due to the metastable α'-martensite phase can be separately measured.

The martensite measurement system according to the present invention pays attention to the remarkable difference in permeability due to the change of martensite and austenite phases, so that the eddy current inspection system used to measure defects or deterioration of materials can detect the occurrence of martensite in the cold working process. It came to the conclusion that it can be a measurement system that can measure in real time and give feedback directly to the production line.

More specifically, the martensite measuring system according to the present invention includes a transducer 20, an oscillator 10, and an impedance measuring device 30 as shown in FIG. 2A. However, in FIG. 2a, the oscillator 10 and the impedance meter 30 are installed inside the case 60 and are not visible, but in FIG. 2c, the oscillator 10 and the impedance meter 30 are installed inside the case 60. have.

Like a normal eddy current flaw detector, the probe 20 includes a probe coil 21 that generates eddy current on the surface of the tube product P.

The oscillator 10 is a device that applies AC power to the probe coil 21, and the impedance measuring device measures the probe coil 21 by applying feedback to the probe coil 21 again by the eddy current generated on the surface of the probe P. detects the change in the impedance of

That is, the probe coil 21 uses the change in impedance due to the change in magnetic permeability among the change in impedance induced in the probe coil 21 due to the eddy current formed on the surface of the tube product P while receiving AC power. It is possible to measure the location and amount of organic martensite, which is a metastable phase, formed on the surface of the tubular product P during the cold working process.

For reference, the oscillator 10 and the impedance meter 30 are not shown in FIG. 2A because the inside of the case 60 is not shown, but the oscillator 10 and the impedance meter 30 are installed inside the case 60 through FIG. 2B. can be known to be

At this time, whether or not martensite is generated can be identified directly from the impedance measurement curve as shown in FIG. 1d. That is, the region where the upper dotted line curve is derived from the lower solid curve, which is the impedance curve of normal austenitic stainless steel, is found to be the region where martensite is formed.

In this case, the probe coil 21 is formed to have a larger diameter than the outer diameter of the tube product P, and the probe coil 21 is fixed to a member having a hole through which the tube product P passes. That is, the probe coil 21 is formed in a circular shape as shown in FIG. 2A, and the tube product P is inserted into the probe coil 21, so that whether or not martensite is formed on the surface of the tube product P is directly determined. can be figured out

At this time, the member in which the probe coil 21 is installed and the hole through which the tube product P passes is formed is the probe coil fixing panel 22 shown in FIGS. 2A and 2B. Here, the probe coil 21 is installed in a form inserted into the inner circumferential surface of a hole formed in the probe coil fixing panel 22 .

Since the probe coil 21 is installed on the member in the form of a thin plate like this, the position of the probe coil fixing panel 22 itself becomes the position of the probe coil 21, so even while the probe coil fixing panel 22 is freely varied, Martens The site where the site is detected can be accurately identified.

In addition, as shown in FIG. 3A, the martensite measuring system according to the present invention has the same material and the same outer diameter as the tubular product P, is formed by a certain length, and artificially stresses induced martensite on a part of the outer circumferential surface of a certain size. A reference sample 40 for comparison, in which a reference region 41, which is a region generated by the amount of time, is formed, is further provided, a coil for comparison 51 manufactured in the same manner as the probe coil 21, and a probe coil fixing panel 22 A comparison transducer 50 composed of a coil fixing panel 52 for comparison manufactured in the same manner as above may be further provided.

As a result, the real-time impedance data of the surface of the tube product P measured by the probe 20 is compared with the impedance data measured by the comparison probe 50, thereby increasing the amount and location of martensite generated on the surface of the tube product P. can be derived more accurately.

At this time, a plurality of reference parts 41 are provided, and each of the plurality of reference parts 41 is formed to have a different size, so that the impedance measured on the surface of the tube product P and the control among the plurality of reference parts 41 Based on the measurements of the reference portion 41 showing the impedance measurement value closest to the impedance measured on the surface of the product and the adjacent reference portion 41 having the impedance measurement value adjacent thereto, on the surface of the tube product P Estimation errors for the size, density, and position of formed martensite can be reduced.

In addition, although not shown, the probe coil 21 and the contrast coil 51 are differentially connected to each other, so that the probe coil 21 scans the surface of the tube product P while detecting a change in impedance due to a change in permeability. While the contrast coil 51 scans the reference part 41, the probe coil 21 finds the impedance change values of the two reference parts 41 that are closest to the impedance change value detected by the probe coil 21. The amount of induced stress martensite generated corresponding to the impedance change value detected in can be calculated.

Meanwhile, as shown in FIGS. 4A and 4B , a rolling member 231 spaced apart from the probe coil 21 may be provided on an inner circumferential surface of the hole formed in the probe coil fixing panel 22 .

Here, at least three rolling members 231 are installed along the circumferential direction of the inner circumferential surface of the hole, so that the probe coil fixing panel 22 quickly moves in a state where the probe product P is extrapolated to the probe coil fixing panel 22. While being variable along the longitudinal direction of the pipe product P, the distance between the probe coil 21 and the surface of the pipe product P can be kept constant over the entire circumferential direction of the pipe product P.

When the distance between the probe coil 21 and the surface of the tube product P is changed, a corresponding impedance change occurs, so the change in the distance between the probe coil 21 and the surface of the tube product P may reduce the accuracy of measurement. have. In particular, in the process of scanning the probe coil fixing panel 22 while varying it along the longitudinal direction of the tube product P, such a problem of deterioration in accuracy of measurement may occur.

Therefore, in the martensite measuring system according to the present invention, as shown in FIG. 4A to prevent this problem, the probe coil fixing panel 22 can move smoothly and smoothly along the surface of the tube product P, while the probe coil ( 21) and the rolling member 231 that always maintains a constant distance between the surface of the tube product P can be installed.

In this case, at least three or more rolling members 231 may be installed so that the distance between all points of the probe coil 21 and the surface of the tube product P is always kept the same. However, in this case, the three or more rolling members 231 need not be radially symmetrically installed, and the cross-section of the pipe product P between at least one of the straight lines connecting the rolling members 231 and the rest of the straight lines. It just needs to be centered.

In addition, as shown in FIG. 4A, an extension block 23 extending the width of the hole may be coupled to the front or rear surface of the probe coil fixing panel 22 as a block-shaped member in which a hole identical to the hole is formed. At this time, the rolling member 231 is installed on the inner circumferential surface of the expansion block 23, and the same expansion block 23 may be installed on the coil fixing panel 52 for comparison.

Meanwhile, the description of the martensite measurement and evaluation method according to the present invention will be briefly described since most of the contents of the martensite measurement system overlap with those of the martensite measurement system described above.

The martensite measurement evaluation method according to the present invention measures the impedance change of the probe 20 including the probe coil 21, the oscillator 10 for applying AC power to the probe coil 21, and the probe coil 21. Preparing a martensite measuring system composed of an impedance measuring device 30 to measure, extracting and preparing an austenitic stainless steel pipe product P in which cold working has been performed in a cold working process, and pipe product P ) approaching the probe coil 21 and applying AC power to the probe coil 21, inducing eddy current in the tube product P due to the AC power, and in the probe coil 21 due to the eddy current By measuring the impedance change that occurs and evaluating the impedance change value corresponding to the change in magnetic permeability caused by the region where martensite is formed on the surface of the tube product P in the measurement value of the impedance change, ) consists of inferring the position and size of martensite formed on the surface of

Here, the step of applying AC power to the probe coil 21 is performed by inserting the probe coil 21 into the center of the probe coil 21 and then changing the probe coil 21 along the longitudinal direction of the control product P. , It can be performed in the form of scanning the tube product (P) with the probe coil (21).

At this time, the step of preparing the martensite measurement system includes a reference sample 40 for comparison, which is a tube product P having the same shape and size as the tube product P, and a coil 51 for comparison manufactured identical to the probe coil 21. ), and applying AC power to the probe coil 21 may further include inserting the reference sample 40 for comparison into the center of the coil 51 for comparison.

In addition, the step of inducing eddy current in the pipe product P is the step of inducing eddy current in the pipe product P with the probe coil 21, and the step of inducing eddy current in the reference sample 40 for comparison with the contrast coil 51 steps may be included.

At this time, there is no temporal precedence relationship between the step of inducing eddy current in the tube product P and the step of inducing eddy current in the reference sample 40 for comparison.

In addition, in the step of preparing the reference sample 40 for comparison and the comparison coil 51 manufactured identically to the probe coil 21, the surface of the austenitic stainless steel tube product adopted as the reference sample 40 for comparison is artificially by causing martensitic transformation, and in measuring the size and density of the martensite formation part formed in the cold working process in the tube product P inserted into the probe coil 21, the reference part 41 that can be used as a reference A forming step may be further included.

In this case, the reference portion 41 may include a plurality of reference portions 41 formed with different lengths, as shown in FIG. 3B.

In particular, in the step of inferring, when a change in impedance is detected on the surface of the tube product P, a plurality of samples formed on the reference sample 40 for comparison that are greater than the degree of change in impedance detected on the surface of the tube product P. A step of specifying a nearest upper reference part, which is a reference part 41 showing a value of change in impedance closest to the degree of change in impedance detected on the surface of the product P, among reference parts; and Impedance change value that is smaller than the change in impedance detected on the surface and closest to the change in impedance detected on the surface of the control product P among a plurality of reference regions 41 formed on the reference sample 40 for contrast The step of specifying the nearest lower reference region, which is the reference region 41, showing the degree of impedance change shown by the nearest upper reference region and the nearest lower reference region, and the impedance detected on the surface of the control product P. A step of evaluating the size, range, or density of martensite formed on the surface of the tubular product P by comparing and evaluating the degree of change may be included.

The present invention described above is not limited by the foregoing embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible within a range that does not deviate from the technical spirit of the present invention. will be clear to those who have knowledge of

P: tube product 10: oscillator
20: probe 21: probe coil
22: probe coil fixing panel 23: expansion block
30: impedance meter 40: reference sample for contrast
41: reference site 50: comparison transducer
51: contrast coil 52: contrast coil fixing panel
60: case 231: rolling member

Claims (10)

a transducer including a probe coil generating eddy currents on the surface of an austenitic stainless steel pipe product subjected to cold working;
an oscillator for applying AC power to the probe coil;
An impedance measuring device for measuring a change in impedance formed in the probe coil when the AC power is applied to the probe coil; includes,
The probe coil uses the change in impedance due to the change in magnetic permeability among the change in impedance induced in the probe coil due to the eddy current formed on the surface of the pipe product while receiving the AC power. A martensite measurement system that measures the location and amount of organic martensite, a metastable phase formed on the surface of tubular products. According to claim 1,
The probe coil is formed with a larger diameter than the outer diameter of the tube product,
The martensite measuring system, characterized in that the probe coil is fixedly installed to a member in which a hole through which the pipe product can pass is formed. According to claim 2,
The martensite measurement system, characterized in that the member is a plate-shaped member and is a probe coil fixing panel manufactured to be installed in a form in which the probe coil is inserted into the inner circumferential surface of the hole. According to claim 3,
A reference sample for comparison having the same material and the same outer diameter as the tubular product, formed by a certain length, and having a reference portion, which is a portion where stress-induced martensite is artificially generated by a certain size, is formed on a portion of the outer circumferential surface; further provided ,
A comparison probe composed of a comparison coil manufactured identically to the probe coil and a comparison coil fixing panel manufactured identically to the probe coil fixing panel; is further provided,
Martensite measurement characterized in that the generation amount and generation position of martensite on the surface of the tube product are derived by comparing the real-time impedance data of the surface of the tube product measured by the probe with the impedance data measured by the comparison probe system. According to claim 4,
A plurality of reference parts are provided, and since the plurality of reference parts are formed in different sizes, the impedance measured on the surface of the tube product is closest to the impedance measured on the surface of the tube product among the plurality of reference parts. Estimation errors for the size, density and position of martensite formed on the surface of the object can be reduced based on the measurements of the reference site showing the measured impedance and the measurement of the adjacent reference site having the impedance measurement adjacent thereto. Martensite measuring system, characterized in that there is. According to claim 5,
The probe coil and the comparison coil are differentially connected to each other, so that when the probe coil detects a change in impedance due to a change in magnetic permeability while scanning the surface of the tube product, the comparison coil scans the reference portion and the probe coil Martensite measurement characterized in that by finding the impedance change value of the two reference parts closest to the detected impedance change value, the amount of organic stress martensite generated corresponding to the impedance change value sensed by the probe coil is calculated. system. According to claim 3,
A rolling member is provided on an inner circumferential surface of the hole formed in the probe coil fixing panel to be spaced apart from the probe coil,
By installing at least three or more rolling members along the circumferential direction of the inner circumferential surface of the hole,
In a state where the probe coil fixing panel is extrapolated to the probe coil fixing panel, the distance between the probe coil and the surface of the tube product is rapidly variable along the longitudinal direction of the tube product, and the distance between the probe coil and the tube product is circumferential direction of the tube product. Martensite measuring system, characterized in that it remains constant throughout. According to claim 6 or 7,
An extension block is coupled to the front or rear surface of the probe coil fixing panel to expand the width of the hole as a block-shaped member in which a hole identical to the hole is formed,
The rolling member is installed on the inner circumferential surface of the expansion block,
The martensite measuring system, characterized in that the expansion block is also installed on the contrasting coil fixing panel. preparing a martensite measurement system composed of a probe including a probe coil, an oscillator for applying AC power to the probe coil, and an impedance measurer for measuring a change in impedance of the probe coil;
Extracting and preparing an austenitic stainless steel pipe product subjected to cold working in a cold working process;
applying AC power to the probe coil by bringing the probe coil close to the tube product;
inducing eddy current in the tube product due to the AC power source;
measuring an impedance change generated in the probe coil due to the eddy current;
Inferring the position and size of martensite formed on the surface of the tube product by evaluating the impedance change value corresponding to the change in magnetic permeability caused by the area where martensite is formed on the surface of the tube product from the measured value of the impedance change. Martensite measurement evaluation method consisting of; According to claim 9,
The step of applying AC power to the probe coil is to scan the tube product with the probe coil by inserting the probe coil into the center of the probe coil and then changing the probe coil along the longitudinal direction of the tube product. Martensite measurement evaluation method, characterized in that carried out in the form.

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