Magnetic non-destructive testing

GOST R 55612-2013 non-destructive magnetic testing. terms and definitions, GOST R dated September 6, 2013 No. 55612-2013

GOST R 55612-2013

OKS 01.040.19

19.100

Date of introduction 2015-01-01

1 DEVELOPED by the Federal State Unitary Enterprise "All-Russian Research Institute of Optical and Physical Measurements" (FSUE "VNIIOFI")

2 INTRODUCED by the Metrology Department of the Federal Agency for Technical Regulation and Metrology, Technical Committee for Standardization TC 371 “Non-Destructive Testing”

3 APPROVED AND ENTERED INTO EFFECT by Order of the Federal Agency for Technical Regulation and Metrology dated September 6, 2013 N 1029-st

4 INTRODUCED FOR THE FIRST TIME

5 REPUBLICATION. December 2018

The rules for applying this standard are established in Article 26 of the Federal Law of June 29, 2015 N 162-FZ “On Standardization in the Russian Federation” .

Information about changes to this standard is published in the annual (as of January 1 of the current year) information index “National Standards”, and the official text of changes and amendments is published in the monthly information index “National Standards”. In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the next issue of the monthly information index “National Standards”.

Relevant information, notices and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet (www.gost.ru)

1 area of ​​use

This standard establishes terms, with corresponding definitions, used in the field of magnetic non-destructive quality control of materials, semi-finished products and products.

The terms established by this standard are recommended for use in all types of documentation, scientific and technical educational and reference literature.

This standard should be used in conjunction with GOST 19880, GOST 19693, GOST 20906, GOST 16504.

2 Normative references

This standard uses normative references to the following standards:

GOST 13699 Recording and reproducing information. Terms and Definitions

GOST 15467 Product quality management. Basic concepts. Terms and Definitions

GOST 20906 Instruments for measuring magnetic quantities.

Terms and Definitions

Note - When using this standard, it is advisable to check the validity of the reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or using the annual information index "National Standards", which was published as of January 1 of the current year, and on issues of the monthly information index “National Standards” for the current year. If an undated reference standard is replaced, it is recommended that the current version of that standard be used, taking into account any changes made to that version. If a dated reference standard is replaced, it is recommended to use the version of that standard with the year of approval (adoption) indicated above. If, after the approval of this standard, a change is made to the referenced standard to which a dated reference is made that affects the provision referred to, it is recommended that that provision be applied without regard to that change. If the reference standard is canceled without replacement, then the provision in which a reference to it is given is recommended to be applied in the part that does not affect this reference.

3 Terms and definitions

3.1 Basic concepts

3.1.1 magnetic non-destructive testing: Non-destructive testing based on recording stray magnetic fields arising above defects, or on determining the magnetic properties of the test object.

Note - Defect - according to GOST 15467.

3.1.2 magnetic flaw detection: Detection of defects such as violation of the continuity of the material of the test object using magnetic non-destructive testing methods.

3.1.3 magnetic flaw detection: Measuring the geometric dimensions of defects and determining their location in the test object using magnetic non-destructive testing methods.

3.1.4 magnetic thickness gauging: Measurement of the thickness of non-magnetic coatings of the test object using magnetic non-destructive testing methods.

3.1.5 magnetic structuroscopy: Determination of the structure of the material of the test object using magnetic non-destructive testing methods.

3.1.6 applied magnetic field: An external magnetic field in which the magnetic non-destructive testing object or part thereof is located.

3.1.7 defect leakage magnetic field: Local magnetic field arising in the defect zone due to the magnetic polarization of its boundaries.

3.1.8 residual magnetic field (residual field): Magnetic field created in space by the test object after exposure to an applied magnetic field.

3.1.9 magnetic transducer: Magnetic measuring transducer designed for measuring and (or) recording, and (or) indicating a magnetic field during magnetic non-destructive testing.

Note - Terms for types of magnetic transducers not specified in this standard are in accordance with GOST 20906.

3.1.10 magnetic transducer signal: A signal (emf, voltage or resistance of the magnetic transducer) carrying information about the measured magnetic field.

Source: http://docs.cntd.ru/document/464676461

Magnetic control

Magnetic testing (MC) solves problems associated with detecting defects inside and on the surface of structures made of ferromagnetic materials (iron, cobalt, nickel). Detection of flakes, non-metallic inclusions, hairs and other damage using MC methods is feasible only when they are superficial or occur at a depth not exceeding 2-3 mm.

The method is based on the registration and analysis of magnetic stray fields formed around ferromagnetic objects after their magnetization. The presence of defects is indicated by the redistribution of magnetic fluxes and the formation of magnetic stray fields over a certain location.

Varieties of MK methods

To identify and record scattering fluxes indicating the presence of deformations and damage, several MC methods are used, which differ in accordance with GOST 24450-80 in the methods of obtaining initial data:

1. Magnetic particle is the most common and popular method. Featuring ease of use, high sensitivity and versatility, it is used to detect surface and depth deformations up to 2 mm using magnetic powder as an indicator.
2. Induction - based on the use of induction converters (coils) that capture local fluxes of field disturbances formed above damage to the magnetized test object
3. Magnetoresistive - uses magnetoresistive converters to identify and record dissipation fluxes over deformations of a magnetized test object
4. Magnetographic – the use of recording the magnetic field of the object under study on an appropriate medium. The reproduction of the received signalgram is analyzed to identify defects
5. Ponderomotive - built on the ponderomotive interaction of the fixed magnetic field of the object under study and the magnetic field of a permanent magnet, electromagnet or current-carrying frame
6. Fluxgate - the use of fluxgate converters to detect and record the scattering of magnetic fields of welds and other objects under study
7. Hall effect method - the use of the same transducers to record local field disturbances over control objects

The basis of all MC methods is the detection of local field disturbances generated by damage to a magnetized ferromagnet. The magnetic flux moves across the object under study, creating stray fields above the detected defects. Their shape and amplitude reflect the size, parameters and depth of the destruction

Detected defects

MK methods were first used in the 19th century. With their help, the strength as well as the structural condition of gun breech blocks and shells of explosive shells were assessed. Since then, three main areas of MK have been formed:

• Continuity control in ferromagnets
• Assessment of the strength and structural state of ferromagnetic steels and alloys
• Determination of phases in a specific alloy

Quality control using magnetic methods makes it possible to identify damage with the following characteristics:

• Rejection with an opening width on the surface of the examined area from 0.002 mm at a depth of 0.01 mm
• Large internal defects occurring at a depth of 2 mm
• Superficial damage up to 2 mm deep
• Defects under a non-magnetic coating up to 0.25 mm thick

Today magnetic testing is in demand in almost all industrial sectors:

• Petrochemistry
• Metallurgy
• Mechanical engineering
• Energy (CHP, NPP)
• NGK (pipelines, industrial tanks)
• Aviation, shipbuilding and automotive industries

Proper application of MC methods makes it possible to identify and eliminate superficial and deep-seated damage to ferromagnets at an early stage

Features of MK technology

The MK method does not require special preliminary preparation, since it is non-contact. Its essence lies in the analysis of the stray field formed in places where defects accumulate during the magnetization of the objects under study.

Conducting MC is regulated by national and international standards, including GOST 21105-87, RD-13-05-2006 and EN 1290:1998.

1. The magnetic permeability of the discontinuity is much lower than that of the rest of the object under study. Its presence bends magnetic lines of force. Some of them come to the surface of the affected area to bypass the damage and form a local magnetic leakage flux
2. The occurrence of disturbance fields is detected by magnetic transducers, among which the most common are the Hall sensor and its induction, fluxgate, and magnetoresistive variations
3. Control measures are completed by demagnetization of each used part in the field of a solenoid powered by alternating current

Non-contact magnetic testing is most often used in diagnostics:

• Main pipelines:
• Individual pipes with any diameter
• Rolled sheets
• Fittings
• Vertical steel tanks

Instruments and equipment

To magnetize controlled objects, stationary and portable magnetic flaw detectors are used. The former allow you to accurately detect superficial and deeper damage of any direction, the latter allow you to monitor objects in the field.

The disadvantage of diagnostic magnetic flaw detectors is their narrow focus and demanding temperature conditions. To obtain more correct results, experts recommend using a multi-channel model with an ultrasonic analysis function.

1. The operation of the device begins with its calibration, checking against standards and cleaning the surface of the controlled part.
2. Magnetization of the part in accordance with the type of magnetization and sensitivity parameters
3. Application of indicator substance
4. Visual inspection of the part with the ability to fix the indicator pattern for further analysis using a multifunctional flaw detector

Based on a comparison of the obtained drawings with standard samples, a conclusion is made about the possibility of the intended use of the object under study.

Among our clients

Source: https://www.serconsrus.ru/services/magnitnyj-kontrol/

Magnetic non-destructive testing. Magnetic inspection of welds

Magnetic non-destructive testing is a set of methods aimed at identifying defects in products made of ferromagnetic metals and alloys without compromising the integrity of the surface.

This research method is based on the interaction of a control metal powder with the fields resulting from the magnetization of the object being examined.

In the absence of defects, a uniform layer will form on the surface, but any distortion of the magnetic field will lead to the formation of characteristic accumulations of powder, which can be detected during a visual inspection using auxiliary means.

Areas of application of the magnetic testing method

Magnetic inspection of parts allows you to identify hidden defects in industrial and production equipment, utilities, land, water, aerospace transport, and in welds of critical structures.

It is relevant in heavy/light industry - in engineering production, metallurgical plants, for quality control of steel/welded products, structures, power grids, pipelines.

The method is effective in detecting defects with a width of 0.001, a depth of 0.01, but not more than 3 millimeters (subject to a hidden defect), and allows you to make a decision on replacing critical elements in order to prevent emergency situations.

What types of defects can non-destructive magnetic testing detect:

• Lack of penetration, presence of pores, cracks - magnetic testing of welds makes it possible to determine their quality directly upon acceptance of work or during operation of the structure, part, equipment
• Discontinuities, delaminations - effective quality control of products in the metallurgical industry
• Small subsurface defects of all types, inclusions of foreign substances in the thickness of metals. These defects cannot be detected using the capillary method, since there is actually no break in the continuous surface, so the test liquid will not penetrate inside, but the distortion of the magnetic field will not go unnoticed

The method is effective only for surfaces without non-magnetic protective coatings (chrome, etc.). Otherwise, it is necessary to resort to conducting an examination using the method of a constant (applied) magnetic field, but with less productivity.

Magnetic luminescent method

Magnetic control equipment in combination with magnetic luminescent powder (with the addition of a phosphor) allows for more effective visual control of results. Ultraviolet light can more effectively detect defects on dark-colored surfaces in low-light conditions.

The essence of the technique does not change - the part is cleaned, magnetized, if necessary, moistened with water, coated with powder or a suspension based on it. The only difference is visual inspection - UV lamps are used to identify defects.

The phosphor contained in the mixture provides a high-brightness glow precisely in areas of hidden defects, forming clearly visible spots and grooves.

At the POVERKON company you can buy magnetic testing equipment with quality guarantees at competitive prices. At the top of the page there are contact phone numbers for direct communication with our competent specialists who will answer your additional questions.

Source: http://povercon.ru/product-category/magnitnyj-metod-kontrol/

Magnetic flaw detectors: design and application. Unbrakable control

In production and construction, non-destructive testing is one of the most popular methods of diagnosing materials. Using this method, builders evaluate the quality of welded joints, check the density in individual sections of structures, identifying deep-seated defects and flaws. Diagnostic magnetic flaw detectors can detect both surface and subsurface damage with a high degree of accuracy.

Device structure

The basis of the segment of magnetic thickness gauges and flaw detectors are hand-held devices equipped with magnetized working parts - usually in the form of pliers. Externally, these are small devices, the filling of which is an electromagnet that regulates the poles of the wave action. The middle class allows you to work with magnetic permeability, the coefficient of which is above 40.

The body is equipped with an ergonomic handle, thanks to which the device can be used in hard-to-reach places. To supply electric current, the devices are also provided with a cable connected either to a generating station (if work is carried out outdoors) or to a 220 V household power supply. More complex non-destructive testing equipment has a stationary base connected to a computer.

Such diagnostic tools are more often used to check the quality of manufactured parts in production. They perform quality control, recording the smallest deviations from standard indicators.

A type of magnetic devices aimed at identifying defects at a depth of up to 10 mm. In particular, they are used to detect discontinuities in the structure of structures and parts. These can be sunsets, shells, cracks and hairlines. The fluxgate method is also used to assess the quality of welds.

After completing the working session, magnetic flaw detectors of this type can also determine the level of demagnetization of the part as part of a comprehensive diagnostics. In terms of application to parts of different shapes and sizes, the devices have virtually no restrictions.

But, again, we should not forget about the maximum depth of structure analysis.

Magnetographic and eddy current flaw detectors

With the help of magnetographic devices, the operator can detect defects in products at a depth of 1 to 18 mm. Once again, the target signs of deviations in the structure are discontinuities and defects in welded joints. The features of eddy current testing technology include the analysis of the interaction of the electromagnetic field with the waves generated by eddy currents, which are supplied to the subject of control.

Most often, an eddy current flaw detector is used to inspect products made of electrically conductive materials. Devices of this type show highly accurate results when analyzing parts with active electrophysical properties, but it is important to consider that they operate at a shallow depth - no more than 2 mm. As for the nature of the defects, the eddy current method makes it possible to identify discontinuities and cracks.

Such devices also focus primarily on surface defects, which can be recorded at a depth of 1.5-2 mm.

At the same time, it is possible to conduct research to identify a wide range of defects - from weld parameters to detecting signs of delamination and microcracks. The operating principle of such non-destructive testing equipment is based on the activity of powder particles.

Under the influence of electric current they are directed towards the inhomogeneity of magnetic oscillations. This allows you to record imperfections in the surface of the target object of study.

The greatest accuracy in determining defective areas using this method will be present if the plane of the defective area forms a 90-degree angle with the direction of the magnetic flux. As you deviate from this angle, the sensitivity of the device decreases.

When working with such devices, additional tools are used to record defect parameters. For example, the Magest 01 magnetic flaw detector is equipped with a double magnifying glass and an ultraviolet flashlight in its basic configuration.

That is, the direct determination of a flaw on the surface is carried out by the operator through visual inspection.

Preparing for work

Preparatory activities can be divided into two groups. The first will involve directly preparing the working surface, and the second will include setting up the device. As for the first part, the part must be cleaned of rust, various types of lubricants, oil stains, dirt and dust. High-quality results can only be obtained on a clean and dry surface.

Next, the flaw detector is configured, in which the key stage will be calibration with testing against standards. The latter are samples of materials with defects, against which the correctness of the instrument’s analysis results can be assessed. Also, depending on the model, you can fix the working depth range and sensitivity. These indicators depend on the tasks of identifying defects, the characteristics of the material being examined and the capabilities of the device itself.

Modern high-tech flaw detectors allow automatic adjustment according to specified parameters.

Part magnetization

The first stage of work operations, during which the magnetization of the object being examined is performed. Initially, it is important to correctly determine the direction of flow and the type of magnetization with sensitivity parameters. For example, the powder method allows you to perform pole, circular and combined effects on the part.

In particular, circular magnetization is carried out by passing an electric current directly through the product, through the main conductor, through the winding or through a separate section of the element with the connection of electrical contactors. In pole mode, magnetic flaw detectors provide magnetization using coils, in a solenoid environment, through a portable electromagnet, or using permanent magnets.

Accordingly, the combined method allows you to combine two methods by connecting additional equipment during the process of magnetizing the workpiece.

Application of a magnetic indicator

Indicator material is applied to the previously prepared and magnetized surface. It allows you to identify defects in a part under the influence of an electromagnetic field. It has already been said that powders can be used in this capacity, but some models also work with suspensions.

In both cases, before work, it is important to consider the optimal conditions for using the device. For example, the magnetic flaw detector “MD-6” is recommended to be used at temperatures from -40 to 50 ° C and at air humidity up to 98%. If conditions meet the operating requirements, then application of the indicator can begin.

The powder is applied over the entire area, so that a small coverage of areas not intended for research is also provided. This will allow you to get a more accurate picture of the defect. The suspension is applied by jet using a hose or aerosol. There are also methods for immersing a part in a container with a magnetic indicator mixture.

Then you can proceed directly to troubleshooting the product.

Part Inspection

The operator must wait until the activity of the indicator, whether powder particles or suspension, is complete. The product is checked visually with the above-mentioned devices in the form of optical devices. At the same time, the magnifying ability of these devices should not exceed x10.

Also, depending on the requirements for the examination, the operator can take pictures for more accurate computer analysis. Multifunctional magnetic flaw detector stations have in their basic equipment equipment for deciphering replicas with powder deposits.

The drawings obtained during sorting are subsequently checked against standard samples, which allows us to make a conclusion about the quality of the product and its suitability for the intended use.

Conclusion

Magnetic flaw detection instruments are widely used in various fields. But they also have disadvantages that limit their use. Depending on the operating conditions, these may include temperature requirements, and in some cases, insufficient accuracy. As a universal inspection tool, experts recommend using a multichannel magnetic flaw detector, which is also capable of supporting the ultrasonic analysis function.

The number of channels can reach 32. This means that the device will be able to maintain optimal flaw detection parameters for the same number of diverse tasks. Essentially, channels refer to a number of operating modes tailored to specific characteristics of the target material and environmental conditions.

Such models are not cheap, but they provide correct results when identifying surface and internal structure defects of various kinds.

Source: https://FB.ru/article/347911/magnitnyie-defektoskopyi-ustroystvo-i-primenenie-nerazrushayuschiy-kontrol

Our prices

The magnetic quality control technique is applied to ferromagnetic materials.

The method of magnetic non-destructive testing consists in analyzing the interaction between the magnetic field and the object being tested. The result of this interaction is changes in the magnetic characteristics of the material used. Specialists of NGSC LLC provide services for magnetic and radiation monitoring in Yekaterinburg and other cities of the Ural Federal District.

Types of MK

The magnetic method can be of the following types:

• Induction
• Fluxgate
• Magnetographic
• Magnetoresistor
• Magnetic particle

MK control, together with all of the above methods, are based on the detection of all local electromagnetic disturbances occurring due to the formation of flaws in a magnetized ferromagnet. The method requires a procedure for magnetizing the object, which is followed by the formation of a scattering field. Moreover, the amplitude and shape of these fields indicate the size, depth, and nature of the flaw present on the part.

Magnetic testing copes with the detection of the following defects:

• Surface defect Parameters: surface opening width at least 0.002 mm or more, depth at least 0.01 mm;
• Internal damage

Parameters: large defects located at a depth of at least 2 mm;

Parameters: depth reaches 2 mm;

Parameters: the thickness of the non-magnetic coating reaches 0.25 mm.

Application

The magnetic method is used for flaw detection of various areas (surface and subsurface) of ferromagnetic materials (magnetic particle method), obtaining data on magnetic permeability, as well as its change when changing the magnetic field strength (induction method), and of course, for various measurements, including the thickness of the non-ferromagnetic layer covering the ferromagnetic base;

The most common of all of the above is the magnetic particle method. Obtaining results using this method is simple and easy. The low labor intensity of MTD, its sensitivity and versatility are properties that make this method widely applicable in various fields of industry.

MTD allows you to identify surface and subsurface defects, for example: cracks, delaminations, lack of welding of butt joints, sunsets, as well as hairlines, etc.

It is used to control a product of any shape and size if the magnetic properties of the material used in it allow it to be magnetized to a level that is sufficient to form a defect scattering field that attracts ferromagnetic particles.

In the defect-free part of the metal product, the direction of the magnetic flux does not change. When defects (cracks, foreign inclusions, etc.) are encountered along its path.

), that is, areas with low magnetic permeability, some field lines exit and enter the part, creating a magnetic field above the flaw. Magnetic particles that enter this field are exposed to a force that tends to attract them to the defect.

Magnetic particles in the flaw area form chains that are oriented along the magnetic field lines.

The maximum probability of detecting flaws is an angle of 90° with the direction of the magnetic flux. As the angle decreases, sensitivity decreases, so the likelihood of detecting defects is significantly reduced.

SENSITIVITY OF IVD is determined:

• residual magnetization (Br);
• the voltage of the magnetizing field, as well as its orientation relative to the plane of the defect;
• magnetic permeability at the maximum level (µmax);
• roughness of the controlled surface;
• magnetic characteristics of the material (magnetic induction (B));
• coercive force (H0);
• the quality of flaw detection tools and the illumination of the surface being monitored.

FIELD OF APPLICATION OF MTD – almost all industry, including:

• auto and aviation industry;
• metallurgy;
• machine and shipbuilding;
• construction (pipelines, steel structures);
• transport industry (air, rail and road transport).

Types of MTD:

• “Dry” (differs in the method used to apply the indicator to the test object);
• “Wet” (different in the method used to apply the indicator to the test object);
• Fluorescent (color) indicator (used for testing in daylight or ultraviolet rays).

Part preparation

This stage includes:

• cleaning the surface of the part being tested from various dirt or rust, from lubricants or technical oils (when testing is carried out using dry powder or using an aqueous suspension);
• coating the part with the thinnest layer of white paint (if the part has a dark surface on which black magnetic powder is difficult to see).

The effectiveness of MTD is ensured by the following preparatory work:

• Dismantling/installation;
• Elimination of moisture;
• Cleaning from contaminants;
• Ensuring the dryness of the internal cavities of the parts being tested;
• Removing paint and varnish coating from the surface;
• Painting the surface of the product with white paint;
• Cleaning areas where electrical contacts were made;
• Cleaning the product from electrostatic charges.

Part magnetization

This is one of the main verification operations. The quality of testing for defects depends on several factors, including the correctness of the method used, the type of magnetization and its direction.

Magnetic particle testing involves the following types of magnetization:

• Longitudinal (pole) is performed: - in the solenoid; - using coils; - using portable and stationary electromagnets; - using permanent magnets; — using “moving the electromagnetic pole across the object.”

• Circular is carried out by conducting current: - through the part; - along a toroidal winding; — along the central conductor; — across the product area using electrical contacts; — excitation of current (induction) in the product.

• The combined effect is carried out by conducting current: - through the object and using an electromagnet; - by object and using a solenoid; - through the object of 2 currents in directions perpendicular to each other; - according to the object, as well as the solenoid of currents that have a 90° phase shift.

Application of a magnetic indicator

The most optimal method is considered to be one in which the suspension is first applied to the product by dipping the part into a special tank with a thoroughly mixed solution, and then slowly removed from it. However, more often the suspension is applied using a shower, hose or aerosol.

The jet pressure cannot be strong, since in this case the magnetic powder will be washed away from the defective areas. When diagnosing using the dry method, the same requirements apply to the pressure of the air stream used as a tool for applying magnetic powder.

The process of draining a viscous dispersed medium (for example, transformer oil) from a product takes time, which reduces the productivity of a flaw detection specialist.

Part Inspection

Inspection of the part by a flaw detection specialist should be carried out after the powder deposits acquire a permanent appearance, that is, after the suspension has drained from the part.

The part is checked visually, although in cases of doubtful defects, decoding of defects is carried out using optical instruments. The technical characteristics of the optics, its type or magnification are established by regulatory documentation. The optics can have a maximum of ten times magnification.

Continuity irregularities often help to recognize the shape and appearance of the magnetic roller, as well as magnetic powder (luminescent).

Sorting of parts should be carried out based on the results of inspection by an experienced flaw detector. The specialist must have photographs of flaws or defectograms, as well as control templates, that is, samples with minimal defect sizes.

Demagnetization and checking its quality

Magnetic fields of products that have not been demagnetized can lead to undesirable consequences during operation. Because of this, the parts must undergo thorough demagnetization, the quality of which must be checked.

The main methods used for demagnetization:

1. An increase in the temperature of the product to the Curie point, when the material loses its magnetic properties. Such heating may be accompanied by a change in the mechanical properties of the material, which is unacceptable in many cases, so this method is used quite rarely.

2. The passage of a part through a magnetic field zone (alternating or constant).

3. The part is demagnetized as a result of a decrease in the magnetic field.

4. Exposure of the product to a magnetic field (alternating or constant) with an amplitude decreasing from the maximum value to zero, with a simultaneous change in its polarity.

Magnetic particle testing is performed on the following equipment:

• Magnetic particle flaw detectors (stationary, mobile, and portable)

• Magnetic powder complexes
• Universal manual magnetizing devices (pincers)
• Tunnels, solenoids, and demagnetization coils
• Mobile power units
• Magnetic indicator

• Degaussing devices

• Handheld devices
• Stationary installations
• Tabletop demagnetizers
• Special installations

• Hinged inspection panel (cabin)
• Magnetometer

• Universal sample
• Electromagnet
• Magnetic field indicator
• Test ring
• Dry Powder Sprayer
• Portable metal spray bottle
• Indicator strips
• Electromagnetic coil
• Horseshoe permanent magnet
• Berthold penetrometer
• Quantitative and qualitative indicators (QQI)
• Digital light and ultraviolet meter

Source: http://xn--80ace2afj3a.xn--p1ai/metody-kontrolya/magnitnyy-kontrol/

Magnetic method

Magnetic flaw detection is a set of non-destructive testing methods used to detect defects in ferromagnetic metals (iron, nickel, cobalt and a number of alloys based on them).

Defects detected by the magnetic method include such defects as: cracks, hairlines, non-metallic inclusions, lack of fusion, flakes.

Detection of defects is possible if they come to the surface of the product or lie at a shallow depth (no more than 2-3 mm).

What are magnetic methods based on?

Magnetic methods are based on the study of magnetic stray fields around products made of ferromagnetic materials after magnetization. At the locations of defects, a redistribution of magnetic fluxes and the formation of magnetic stray fields are observed. Various methods are used to identify and record scattering fluxes over defects.

Magnetic particle testing method (magnetic particle flaw detection, MPD)

The most common method of magnetic flaw detection is the magnetic particle method . When using the magnetic particle flaw detection (MPD) method, magnetic powder or a magnetic suspension, which is a fine suspension of magnetic particles in a liquid, is applied to a magnetized part.

Particles of ferromagnetic powder that fall into the zone of action of the magnetic stray field are attracted and settle on the surface near the locations of discontinuities. The width of the strip along which the magnetic powder settles can significantly exceed the actual width of the defect. As a result, even very narrow cracks can be detected by settled powder particles with the naked eye.

Registration of the resulting indicator patterns is carried out visually or using image processing devices.

The sensitivity and quality of the magnetic particle method depends on several factors

• on the magnetic characteristics of the material used to manufacture the part;
• magnetizing field strength;
• mutual direction of the magnetizing field and the defect;
• parametric characteristics: size, shape and surface roughness of the part;
• method and conditions for registration, analysis and documentation of the indicator pattern of the detected defect.
• size, shape, location and orientation of the defect;
• properties of the flaw detection material used for testing;
• a method for applying flaw detection material to the surface of a part;  

The magnetic particle method detects defects in the following parameters

• superficial with an opening width at the surface of 0.002 mm or more, a depth of 0.01 mm or more;
• subsurface, located at a depth of up to 2 mm;
• internal (large sizes), lying at a depth of more than 2 mm;
• under various types of coatings, but provided that the thickness of the non-magnetic coating is no more than 0.25 mm.

Application of magnetic non-destructive testing method

Magnetic testing is used today in almost all sectors of heavy and light industry: the petrochemical industry, ferrous metallurgy, mechanical engineering and aviation industry, power and chemical engineering (state district power plants, thermal power plants, nuclear power plants), the automotive industry and shipbuilding, construction (pipelines, steel structures, industrial tanks), transport (aviation, railway, motor transport).

Magnetic testing equipment

When carrying out magnetic testing, Etalon LLC specialists use materials and equipment from leading European manufacturers Magnaflux and Helling.

Source: http://etalon-rk.ru/magnitnyj-metod/

Non-destructive testing methods

 What is this article about?

Almost every area of ​​production needs control that does not destroy the source material.
Each method of non-destructive testing is good in its own way and has its own subtleties and features of implementation. The article provides examples of the most popular of them. You can also look at other articles. For example, “Overview of non-destructive testing devices” or “The principle of operation of gas analyzers.”

Non-destructive testing (NDT), in the language of regulatory documents, is control that does not destroy (this is the definition given in GOST 16504-81 “System of state testing of products. Testing and quality control of products. Basic terms and definitions”).

A concept that seems incomplete and vague takes on clear forms once you sort it out “on the shelves.” Thus, the word “control” means “measuring the values ​​of operating parameters and properties of an object and checking them for compliance with acceptable values.”

“Non-destructive” means “not requiring dismantling or stopping the operation of the object”, “not implying direct intervention in the environment under study.” We have an article on our website - non-destructive testing, which discusses this term in more detail.

The methods by which NDT is implemented are called non-destructive testing methods (hereinafter referred to as NDT).

MNCs, which are based on similar physical principles, are conditionally grouped into types and within them classified according to three criteria:

• by the nature of the interaction of the controlled object with a physical field or substance;
• according to the primary informative parameter (characteristic of the penetrating substance or physical field, which is recorded after its interaction with the control object);
• by the method in which primary information is obtained (primary information is a set of characteristics of a penetrating substance or physical field recorded after interaction with a controlled object).

The definition of each control method - there are more than a hundred of them - can be found in GOST 18353-79 “Non-destructive testing. Classification of types and methods."

In this article, MNCs will be considered in groups (the basis for their unification is their belonging to a particular species or, as noted earlier, the commonality of physical principles realized during the application).

Magnetic non-destructive testing methods

Magnetic MNCs are based on the analysis of the interaction of a controlled object with a magnetic field and are used, as a rule, to detect internal and surface defects in objects made of ferromagnetic materials.

The main magnetic NDT methods include magnetic particle, fluxgate, induction and magnetographic methods. The most common and reliable among MNCs of its type is magnetic particle - based on the occurrence of inhomogeneity of the magnetic field above the defect site.

Fig. 1 – Magnetic particle MNC

To implement the method, it is necessary to prepare the surface of the controlled object, magnetize it and treat it with a magnetic suspension. Metal particles caught in a non-uniform magnetic field that arises above the damage are attracted to each other and form chain structures (Fig. 1), which are revealed during inspection of the parts.

The remaining magnetic control methods that have not been considered are similar. The only difference is that instead of magnetic powder and subsequent visual inspection, an inductive coil (induction method), magnetic tape and a sensor equipped with a magnetic head (magnetographic method), and a fluxgate sensor that records stray fields (fluxgate method) are used.

Electrical non-destructive testing methods

Electrical MNCs are based on recording and analyzing the parameters of the electric field that interacts with the test object or arises in it as a result of external influence. The primary informative parameters are potential and capacity.

Let us consider the essence of electrical methods using the example of the electropotential method, based on recording and analysis of potential drop.

If an electric voltage is applied to a metal body (shown in Fig. 2), then an electric field will arise in it, and points with the same potential form equipotential lines. In places of defects, a voltage drop will occur, which can be measured using electrodes and conclusions can be drawn about the nature and extent of the damage.

Fig. 2 – Electropotential MNC

In addition to the electropotential method used to control the quality of conductor materials, the following electrical methods are used:

• capacitive (control of semiconductors and dielectrics);
• thermoelectric (control of the chemical composition of the material);
• electronic emissions;
• electric spark;
• electrostatic powder (method similar to magnetic powder).

Eddy current non-destructive testing methods

Eddy current MNCs are based on the study of the interaction of the electromagnetic field of an eddy current transducer with the electromagnetic field of eddy currents induced in the test object, having a frequency of up to 1 million Hz.

In practice, this method is used to control objects that are made of electrically conductive materials. With its help, information is obtained about the chemical composition and geometric size of the product, about the structure of the material from which the object is made, and defects located on the surface and in the subsurface layer (at a depth of 2-3 mm) are detected. A typical device used by this method is an eddy current flaw detector.

The principle of control is as follows. With the help of inductance coil 1, eddy currents 2 are excited in the control object 3, which are recorded by a receiving meter, which is the same or another coil. Based on the intensity of the current distribution in the controlled object, one can judge the size of the product, the properties of the material, and the presence of discontinuities.

Fig. 3 – Eddy current MNC (passage)

Figure 3 shows the eddy current transmission method (the exciting coil and the receiver are located on two sides of the object). The main methods of eddy current testing also include

• scattered radiation method (registration of scattered waves or particles reflected from a defect);
• echo method or reflected radiation method (fields and waves reflected from the defect are recorded).

Radio wave methods of non-destructive testing

Radio wave MNCs are based on recording and analyzing changes in parameters possessed by electromagnetic radio waves interacting with the control object (their length ranges from 0.01 to 1 m). These methods can be used to control objects made of materials that do not “dampen” radio waves - dielectrics (ceramics), semiconductors, magnetodielectrics and thin-walled metal objects.

It would not be a mistake to compare radio wave methods with eddy current methods. As in the case of eddy current MNCs, the equipment for implementing the radio wave method consists of a generator 1 and a wave receiver 3.

An example of the relative position of the generator, the control object and the wave receiver is shown in Figure 4.

Fig. 4 – Radio wave method NMC (transmission)

Based on the nature of the interaction of the object with the wave, radio wave methods of transmission, reflection and dispersion are distinguished; according to the primary informative parameter - phase, geometric, amplitude-phase and polarization least squares.

Thermal methods of non-destructive testing

Thermal MNCs use thermal energy propagating in the test object as test (information-carrying) energy. The temperature field directly depends on the heat transfer processes occurring in the object, the features of which depend on the presence of defects (both internal and external).

The main informative parameter of thermal LSM is the temperature difference between defect-free and defective areas of the object. Temperature can be measured by contact and non-contact methods.

Depending on the nature of the interaction between the controlled object and thermal energy, active (Fig. 5) and passive methods of thermal least squares are distinguished.

The active method is as follows: the controlled object 6 is cooled or heated using an external source 1, and then the temperature on its surface is measured using the control device 5. Areas of increased or decreased heating correspond to defects 4.

Fig. 5 – Active thermal NDT method

When using the passive method (called the self-radiation method), heat sources are not used. Instead, the heat flows of working objects are recorded, assigning malfunctions and defects to places of increased heating.

Thermal methods are widely used not only in monitoring technological processes and product quality; They are also used in medicine, astronomy, and monitoring (forest fires, for example).

Optical methods of non-destructive testing

Optical least squares are based on registration and analysis of parameters inherent in optical radiation interacting with an object (this includes electromagnetic waves with a length of 10-5 to 10-3 μm).

Using optical MNCs, voids, pores, delaminations, cracks, foreign inclusions, geometric deviations and internal stresses in test objects are detected. The information parameters of the methods are the integral and spectral photometric characteristics of the radiation.

External optical testing can be applied to objects made of any materials. Detection of internal defects (inhomogeneities, stresses) is only possible in relation to transparent objects. To control diameters and thickness, optical methods based on the phenomenon of diffraction are used, to control roughness and sphericity - on the phenomenon of interference.

Optical testing can be performed by methods of intrinsic (a), reflected (b) and transmitted (c) radiation.

Rice. 6 – Test schemes for optical MNCs

The receiving device can record the following informative parameters - amplitude, degree of polarization and phase of the wave, time of its passage through the object, frequency or frequency spectrum of the radiation.

Radiation methods of non-destructive testing

Radiation least squares are based on recording penetrating ionizing radiation interacting with an object and its subsequent analysis. Depending on the type of ionizing radiation, the word “radiation” in the name of the methods can be replaced by “X-ray”, “neutron” and others.

Most often, gamma and X-ray radiation is used for control, which allows identifying almost any defect (both internal and surface).

A diagram of the application of radiation monitoring by the transmission method (it is worth noting that the reflection method is practically not used) is shown in Figure 7.

Source: http://www.DeviceSearch.ru.com/article/metody_nerazrushayuschego_kontrolya

Unbrakable control. Methods

Non-destructive testing (translated from English - NDT, nondestructive testing) is checking, monitoring, assessing the reliability of the parameters and properties of structures, equipment or individual components, without disabling (operating) the entire facility.

The main difference, and an absolute advantage, of non-destructive testing (NDT) from other types of diagnostics is the ability to evaluate the parameters and operating properties of an object using control methods that do not involve stopping the operation of the entire system, dismantling, or cutting out samples. The research is carried out directly under operating conditions.

This makes it possible to partially eliminate material and time costs and increase the reliability of the controlled object.

Thanks to non-destructive testing, dangerous and minor defects are revealed: manufacturing defects, internal stresses, cracks, micropores, voids, delaminations, inclusions and many others, caused, among other things, by corrosion processes.  

Classification of non-destructive testing methods (according to GOST 18353-79)

Depending on the physical phenomena underlying non-destructive testing, there are nine main types:

— radio wave method;

- electric;

— acoustic method;

— eddy current method;

- magnetic;

— thermal;

— radiation method of non-destructive testing;

— penetrating substances;

— optical NDT method.

Each type of non-destructive testing may include several methods.

Classification of NDT methods by characteristics:

— primary informative parameters;

— the nature of interaction with the controlled (studied) object;

— method of obtaining initial information.

It is possible to use several methods that are classified according to several criteria, several or one type of non-destructive testing.

Radio wave method of non-destructive testing

Primary informative parameter: phase, time, amplitude, polarization, frequency, geometric.

Interaction with a controlled object of physical fields: resonant, scattered, reflected, transmitted radiation.

Classification of radio wave non-destructive testing according to the method of obtaining initial information: thermistor, thermoluminescent, diode (detector), calorimetric, liquid crystal, bolometric, semiconductor photocontrolled wafers, holographic, thermal paper and interference.

The essence of radio wave NDT is to record changes in the indicators of radio magnetic waves that interact with the structure (object) under study.

Electrical non-destructive testing method

Primary informative parameter: electrical capacitance, electropotential.

Interaction with a controlled object of physical fields: thermoelectric, electric, triboelectric.

Classification of the electrical method according to the method of obtaining initial information: contact potential difference, electroparametric, exoelectronic emission, powder electrostatic, recombination radiation, noise, electric spark.

The basis of the electrical method of non-destructive testing is the registration of indicators of the electric field, which, as a result of external influence, arises in the test (monitoring) object or interacts with it.

Acoustic method

Primary informative parameter: time, spectral, amplitude, frequency, phase.

Interaction with the controlled object of physical fields: resonant, free vibrations, transmitted, reflected (echo method) radiation, impedance, acoustic emission.

Classification of acoustic non-destructive testing according to the method of obtaining initial information: powder, piezoelectric, microphone, electromagnetic-acoustic.

This type of monitoring, such as acoustic, consists of recording the parameters of elastic waves that arise and (or) are excited in the object being monitored. The use of ultrasonic elastic waves (whose frequency is more than 20 kHz) makes it possible to call this type of NC no longer acoustic, but ultrasonic.

Eddy current non-destructive testing method

Primary informative parameter: frequency, amplitude, multi-frequency, phase, spectral.

Interaction with a controlled object of physical fields: reflected and past healing.

Classification of eddy current non-destructive testing according to the method of obtaining initial information: parametric, transformer.

The essence of the eddy current method is the study and subsequent analysis of the interaction of the electromagnetic field of eddy currents (which are induced in the object under study) and the field of the eddy current transducer.

Magnetic non-destructive testing method

Primary informative parameter: magnetic permeability, coercive force, intensity of the Barkhausen Effect, remanent induction, magnetization.

Interaction with a controlled object of physical fields: magnetic.

Classification of magnetic non-destructive testing according to the method of obtaining initial information: fluxgate, magnetoresistive, magnetographic, induction, ponderomotive.

The magnetic NDT method is based on analyzing the interaction of the structure under study with a magnetic field.

Thermal method

Primary informative parameter: thermometric, thermometric.

Interaction with the controlled object of physical fields: convective, contact thermal, self-radiation.

Classification of thermal NDT according to the method of obtaining initial information: calorimetric, temperature-dependent parameters, thermal papers, pyrometric, thermal paints, optical, liquid crystals, interference, thermoluminophores.

The thermal method of non-destructive testing consists of detecting defects based on the analysis of the temperature or thermal fields of the structure. The method is used when there are heat flows in the controlled structure or object.

Radiation non-destructive testing method

Primary informative parameter: spectral, energy flux density.

Interaction with the controlled object of physical fields: activation analysis, field emission, transmitted radiation, characteristic radiation, scattered radiation.

Classification of radiation non-destructive testing according to the method of obtaining initial information: secondary electrons, radioscopic, scintillation, radiographic, ionization.

The essence of the radiation NDT method is the study of penetrating radiation (neutron, x-ray, etc.).

Penetrant non-destructive testing method

Primary informative parameter: gas, liquid.

Interaction with a controlled object of physical fields: molecular.

Classification of non-destructive testing of penetrating substances according to the method of obtaining initial information: bubble, chromatic (color), filtering particles, luminescent, achromatic (brightness), manometric, luminescent-color, mass spectrometric, halogen, radioactive, chemical, acoustic, stable residual deformations, high-frequency discharge, katharometric.

Defects are detected using substances that fill the pores and cavities of defects, after which they can be visually examined (in person or with the help of special instruments) and the degree of damage can be judged.

Depending on the substance used and the type of defects detected (through, surface), the name of the control method may change from “penetrating substances” to “leak detection”, “capillary”, etc.

Optical non-destructive testing method

Primary informative parameter: frequency, polarization, amplitude, spectral, phase, geometric, time.

Interaction with a controlled object of physical fields: induced, scattered, transmitted, reflected radiation.

Classification of optical NDT according to the method of obtaining initial information: visual-optical, holographic, interference, reflexometric, nephelometric, refractometric.

The method is based on recording and analyzing optical radiation indicators.

Depending on the goals and objectives, one or another non-destructive testing method is used. In some cases, to obtain a more complete and informative picture, several NDT methods are used.

Source: https://www.okorrozii.com/nerazrushayushchij-kontrol-metody.html

Popular non-destructive testing methods - magnetic and electrical

The quality of products made from ferromagnetic materials is checked primarily by magnetic NDT methods. Testing methods are based on analysis of the interaction of the test item with a magnetic field and are most effective for identifying internal and surface flaws in objects.  

Basic magnetic non-destructive testing methods:

• magnetic particle;
• fluxgate;
• induction;
• Magnetographic.

The first of the listed methods - magnetic particle - is recognized as the most reliable and therefore is very widespread. The essence of the method: a non-uniform magnetic field appears above the defect site.  

How this method of non-destructive testing of metal works:

• First, prepare the surface of the controlled object.
• It is magnetized and treated with a magnetic suspension.
• As a result, a non-uniform magnetic field is created over the damage. Metal particles are attracted to each other, the chain structures they form are revealed during inspection of parts.

All other methods of magnetic NDT work in a similar way. Although there are still some differences. Magnetic powder and optical control are changed to:  

• inductor (with the induction method);
• magnetic tape and sensor with a magnetic head (with magnetographic);
• fluxgate sensor for recording scattering fields (with fluxgate), etc.

Electrical non-destructive testing methods

Electrical MNCs are based on the principle of constant recording and analysis of the properties of the electric field, which:

1. interacts with a controlled object;
2. arises in the object itself as a result of external influence.

Potential and capacity are taken as initial informative characteristics.

The essence of electric MNCs is perfectly demonstrated by the electropotential method, in which it is necessary to clearly record and analyze the potential drop.

How the method works:

• Electrical voltage must be applied to the metal body. 
• As a result, an electric field arises in it, with points with the same potential creating equipotential lines. 
• The voltage drops at the point of manufacturing defect or damage to the item during operation. 
• The voltage is measured using electrodes and, based on the information obtained, conclusions are drawn about the property and size of the defect. 

To control the quality of products made of solid conductive materials (metal and alloys of various modifications), other electrical methods are used:

1. capacitive (for monitoring semiconductor and dielectric standards);
2. thermoelectric (to control the chemical composition of the material);
3. electronic emissions;
4. electric spark;
5. electrostatic powder (method similar to magnetic particle).

Eddy current non-destructive testing methods

Eddy current MNCs are used to test the qualities and properties of objects made from materials that conduct electric current. 

Eddy current methods of non-destructive testing of metal are based on the study of the interaction of two electromagnetic fields:

1. external field created by an eddy current transducer;
2. field of eddy currents induced by an inductive coil in the test object (OC).

As a rule, eddy currents with a frequency of up to 1 million Hz occur in an electromagnetic object.

Basic methods of eddy current testing: 

1. scattered radiation method;
2. echo method, or reflected radiation method. 

Their essence is that it is necessary to register scattered waves, particles, fields, etc. reflected from the defect.

How control is carried out:

Inductor 1 excites eddy currents 2 in the test object 3.

At this time, the receiving meter (the same or an additional coil) registers eddy currents, namely the intensity of their distribution in the OK. Based on these data, conclusions can be drawn about the dimensions of the product, the properties of the material, and the presence of shortcomings.

The exciting coil and the receiver are located on both sides of the object.

Use this method to obtain information about:

• chemical composition of the product;
• geometric size of the object;
• the structure of the material from which the OK is made;
• the presence of defects on the surface or in the subsurface layer (investigation depth - 2-3 mm).

Source: https://speranza-ua.com/news/populyarnye-metody-nerazrushayushhego-kontrolya/