CN114383493B - Non-contact metal surface non-conductive coating thickness measuring method - Google Patents
Non-contact metal surface non-conductive coating thickness measuring method Download PDFInfo
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- CN114383493B CN114383493B CN202210188561.3A CN202210188561A CN114383493B CN 114383493 B CN114383493 B CN 114383493B CN 202210188561 A CN202210188561 A CN 202210188561A CN 114383493 B CN114383493 B CN 114383493B
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- 239000002184 metal Substances 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 25
- 238000000576 coating method Methods 0.000 title claims abstract description 13
- 239000011248 coating agent Substances 0.000 title claims abstract description 12
- 238000005260 corrosion Methods 0.000 claims abstract description 17
- 230000007797 corrosion Effects 0.000 claims abstract description 17
- 238000005259 measurement Methods 0.000 claims abstract description 14
- 238000001514 detection method Methods 0.000 claims description 31
- 238000012360 testing method Methods 0.000 claims description 20
- 239000000758 substrate Substances 0.000 claims description 13
- 238000013461 design Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 3
- 230000003746 surface roughness Effects 0.000 abstract description 2
- 238000000441 X-ray spectroscopy Methods 0.000 description 3
- 238000006073 displacement reaction Methods 0.000 description 3
- 238000009659 non-destructive testing Methods 0.000 description 3
- 239000010953 base metal Substances 0.000 description 2
- 238000009675 coating thickness measurement Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009972 noncorrosive effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
- G01B7/08—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using capacitive means
- G01B7/085—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using capacitive means for measuring thickness of coating
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
The invention discloses a non-contact metal surface non-conductive coating thickness measuring method, which combines the principle of an eddy current ranging sensor and the principle of a capacitance ranging sensor to realize non-contact measurement of a metal surface corrosion layer, avoids the influence of surface roughness and corrosion layer porosity under different contact forces of contact measurement through non-contact measurement, and meets the use convenience of an industrial site without using high-energy rays.
Description
Technical Field
The invention relates to the technical field of thickness measurement of a non-conductive coating on a metal surface, in particular to a non-contact type thickness measurement method for the non-conductive coating on the metal surface.
Background
The non-destructive testing methods of metal surface coatings listed in GB/T6463-2005 review of metal and other inorganic coating thickness measurement methods are shown in Table 1 below, and the measurement ranges of the various instruments are also given. As can be seen from the table, the various methods have certain use limitations, and only the eddy current method and the X-ray spectroscopy are applicable for the nondestructive measurement of the thickness of the opaque loose oxide layer with the thickness ranging from 1 um to 20 um.
Table 1 method for non-destructive testing of oxide layer on surface of common metal
The problem of carrying out nondestructive testing of an oxide layer on a metal surface by an eddy current method and an X-ray spectrometry in the prior art is that:
1. although the eddy current method is a nondestructive test, the probe needs to contact the surface of the corrosion layer, if the metal substrate is a rough surface or the corrosion layer on the surface is in a loose structure, the magnitude of the operation contact force can influence the measurement result, the contact force is large, and the test value can be reduced.
2. The X-ray spectrometry is high in cost, needs radiation protection, is mostly used in laboratory scientific research, and is not suitable for industrial field use.
It is therefore desirable to develop a non-contact metal surface non-conductive coating thickness measurement method to solve the above-mentioned problems.
Disclosure of Invention
The invention aims to solve the problems and designs a non-contact metal surface non-conductive coating thickness measuring method.
The invention realizes the above purpose through the following technical scheme:
a non-contact metal surface non-conductive coating thickness measuring method comprises the following steps:
arranging a detection coil close to the surface of the metal to be detected;
testing to obtain the self inductance value L of the detection coil;
through the design of the working parameters of the detection coil, the d value and d are enabled to be within the range of the measuring range 0 In a linear relationship, the distance d between the detection coil and the metal substrate is calculated by the following equation:
d＝k·L+d 0 (1)
wherein k, d 0 The equation coefficients are obtained through engineering calibration;
the capacitance C between the detection coil and the metal substrate is the surface of the detection coil and the corrosion layerCapacitance value C of air between 2 And the capacitance value C of the corrosion layer 1 The series is obtained according to the capacitive series equation:
according to the formula of the plate capacitanceC in the above formula 1 And C 2 With thickness d of etching layer 1 And air layer thickness d 2 The expression is:
wherein ε 0 ＝8.854187818×10 -12 F/m is vacuum dielectric constant; epsilon r1 ,ε r2 Is the relative dielectric constant of the material; s is the projection area of the detection coil on the metal substrate;
according to the dimensional chain relationship, there are:
d＝d 1 +d 2 (4)
simultaneously three equations (1), (3) and (4) are respectively solved for d 1 ,d 2 In which d is expressed in L, C 1 The expression of (2) is:
preferably, the distance between the detection coil and the surface of the detected metal is smaller than 0.2mm during measurement.
Preferably, the outer diameter of the detection coil is greater than 5mm.
Preferably, the thickness of the detection coil is less than 0.3mm.
The invention has the beneficial effects that:
1. the invention adopts non-contact measurement, thereby avoiding the influence of surface roughness and corrosion layer porosity under different contact forces of contact measurement; compared with an X-ray method, the testing method does not use high-energy rays, and meets the use convenience of an industrial site.
Drawings
Fig. 1 is a schematic view of a working scenario of the present invention.
In the figure: 1. a detection coil; 2. etching the layer; 3. a metal substrate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, or the directions or positional relationships conventionally put in place when the inventive product is used, or the directions or positional relationships conventionally understood by those skilled in the art are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific direction, be configured and operated in a specific direction, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, terms such as "disposed," "connected," and the like are to be construed broadly, and for example, "connected" may be either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The following describes specific embodiments of the present invention in detail with reference to the drawings.
The invention combines the principle of the eddy current ranging sensor and the principle of the capacitance ranging sensor to realize non-contact measurement of the metal surface corrosion layer 2, and the specific technical scheme is as follows.
As shown in fig. 1, a non-contact metal surface non-conductive coating thickness measuring method includes the following steps: the corrosion layer 2 is arranged on the metal surface, and the detection coil 1 and the surface to be detected are measured in a non-contact manner; arranging the detection coil 1 close to the surface of the metal to be detected; according to the electric vortex distance measuring principle, the distance d between the coil and the metal substrate 3 can be obtained by testing the self inductance value L of the detection coil 1, and the d value and d are enabled to be within the range through the design of the working parameters of the coil 0 In a linear relationship, the distance d between the detection coil 1 and the metal base 3 is calculated by the following equation:
d＝k·L+d 0 (1)
wherein k, d 0 The equation coefficients are obtained through engineering calibration;
if the distance between the coil and the metal substrate 3 is divided into airThe layer distance and the thickness of the corrosion layer 2 can be considered that the capacitance C between the detection coil 1 and the metal substrate 3 is the air capacitance C between the detection coil 1 and the surface of the corrosion layer 2 2 And the capacitance value C of the corrosion layer 2 1 The series is obtained according to the capacitive series equation:
according to the formula of the plate capacitanceC in the above formula 1 And C 2 With thickness d of etch layer 2 1 And air layer thickness d 2 The expression is:
wherein ε 0 ＝8.854187818×10 -12 F/m is vacuum dielectric constant; epsilon r1 ,ε r2 Is the relative dielectric constant of the material; for air, ε r2 = 1.00059. For the corrosion layer 2, different corrosion layers 2 have different relative dielectric constants, which can be obtained by base material level test. S is the projection area of the detection coil 1 on the metal substrate 3;
according to the dimensional chain relationship, there are:
d＝d 1 +d 2 (4)
simultaneously three equations (1), (3) and (4) are respectively solved for d 1 ,d 2 In which d is expressed in L, C 1 The expression of (2) is:
in order to ensure the test precision, the detection coil 1 should be as close to the surface to be tested as possible so as to improve the capacitance value between the coil and the metal and the good electric vortex linearity and improve the capacitance test precision; preferably, the distance between the detection coil 1 and the surface of the metal to be detected is less than 0.2mm during measurement.
In terms of improving the test capacitance value, the coil should be designed to be as large as possible in terms of design of the detection coil 1 so as to improve the capacitance value between the coil and the metal and improve the capacitance test precision; preferably, the outer diameter of the detection coil 1 is larger than 5mm;
in addition, the test coil should be as thin as possible to reduce the effect of capacitive test edge effects on the test capacitance value; the thickness of the detection coil 1 is preferably less than 0.3mm.
The L value and the C value can be tested by a commercial high-precision impedance tester, and also can be tested by a mature transmitter, and in the test process, the test should be alternately repeated until the test value is stable, so that higher test precision can be obtained.
In practical engineering application, the specific engineering calibration method of each parameter is as follows.
k-by the principle of calibrating the eddy current displacement sensor, aiming at the test piece of the same base metal material without the corrosion layer 2, delta d is given by changing d on the displacement calibration frame, and k=delta d/delta L is found when delta L is actually measured, so that the calibration precision is improved, and the least square method can be adopted for fitting.
d 0 For a non-corrosive layer metal substrate 3, there is d 1 =0, obtainable according to formula (5):
get->Wherein C, L is obtained by actual measurement 0 ，ε r2 The method is a known physical constant, is accurate, and can be used for giving the projection area of the coil according to design parameters and engineering calibration.
S-e.g.If engineering calibration parameters are needed, the engineering parameter calibration process is as follows, and aiming at the test piece with the same base metal material and the non-corrosive layer 2, the formula (3) is simplified asChanging d on displacement calibration stand 2 Gives Δd 2 Then there isWherein C ', C' is obtained by changing the measured capacitance before and after d2, there is +.>In order to improve the fitting accuracy, the least square method can also be adopted for fitting.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the scope of the invention.
Claims (4)
1. The non-contact metal surface non-conductive coating thickness measuring method is characterized by comprising the following steps:
arranging a detection coil close to the surface of the metal to be detected;
testing to obtain the self inductance value L of the detection coil;
through the design of the working parameters of the detection coil, the d value and d are enabled to be within the range of the measuring range 0 In a linear relationship, the distance d between the detection coil and the metal substrate is calculated by the following equation:
d＝k·L+d 0 (1)
wherein k, d 0 The equation coefficients are obtained through engineering calibration;
the capacitance C between the detection coil and the metal substrate is the air capacitance C between the detection coil and the surface of the corrosion layer 2 And the capacitance value C of the corrosion layer 1 The series is obtained according to the capacitive series equation:
according to the formula of the plate capacitanceC in the above formula 1 And C 2 With thickness d of etching layer 1 And air layer thickness d 2 The expression is:
wherein ε 0 ＝8.854187818×10 -12 F/m is vacuum dielectric constant; epsilon r1 ,ε r2 Is the relative dielectric constant of the material; s is the projection area of the detection coil on the metal substrate;
according to the dimensional chain relationship, there are:
d＝d 1 +d 2 (4)
simultaneously three equations (1), (3) and (4) are respectively solved for d 1 ,d 2 In which d is expressed in L, C 1 The expression of (2) is:
。
2. the method for measuring the thickness of the non-conductive coating on the metal surface according to claim 1, wherein the distance between the detection coil and the measured metal surface is less than 0.2mm during measurement.
3. A method of measuring the thickness of a non-conductive coating on a metal surface as recited in claim 1, wherein the outer diameter of the sensing coil is greater than 5mm.
4. A method of measuring the thickness of a non-conductive coating on a metal surface as recited in claim 1, wherein the thickness of the sensing coil is less than 0.3mm.
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