Suspension for magnetic particle detection

Abstract

The method is used for magnetic powder detection. The core of the invention lies in that the suspension for magnetic particle detection comprises a water-based or hydrocarbon-based liquid carrier and ferromagnetic powder consisting of ferromagnetic particles obtained from iron-containing industrial waste by dispersion and / or thermochemical treatment, the initial roundness and sphericity of the powder being not less than 0.15, and the particle size of the ferromagnetic particles being not less than 10 [mu] m. The overall kinematic viscosity of the suspension at the temperature of 20 DEG C does not exceed 90 cSt (centistokes), and the suspension comprises the following components in percentage by weight: 0.05-90.0 wt% of magnetic powder and 10.0-99.95 wt% of liquid carrier. The technical effect is that the sensitivity of the ferromagnetic suspension liquid in the aspect of detecting surface and near-surface defects is improved.

Description

[0001] The present invention relates to non-destructive testing (NDT) using magnetic particle inspection (MPI).

[0002] Known MPI suspensions consist of organic solvents (such as a mixture of kerosene and mineral oil) and ferromagnetic powder [SU318861A1, IPC G01N 27 / 84, published in 1971]. To improve the quality of the suspension and the sensitivity of defect detection, 0.1% to 5% (by weight) of nitrated mineral oil is added to its formulation. Its ferromagnetic particles do not coagulate and can remain suspended for a long time because the nitrated mineral oil added to the suspension adsorbs on the surface of the powder particles, thus forming an energy barrier at the interface between the particles and the liquid, preventing the ferromagnetic particles from spontaneously aggregating into a flaky structure.

[0003] A magnetosensitive liquid for visualizing a magnetic recording field, the composition of which includes magnetite, kerosene, and oleic acid. To improve the stability of its properties during storage, the liquid also contains mineral oil, and its component ratios (volume percentages) are as follows: magnetite 18 - 20, oleic acid 2 - 3, mineral oil 40 - 47, and the rest is kerosene.

[0004] A known method for preparing a magnetosensitive liquid for visualizing a magnetic recording field and performing magnetic detection, the method includes preparing a magnetosensitive liquid containing magnetite, kerosene, and oleic acid, adding it to a kerosene-based magnetic liquid containing magnetite particles (average diameter of 15 - 17 nm), with a volume of 30 - 50 ml, adding 0.1 - 0.2 ml in batches within 10 - 15 seconds while continuously stirring until the oleic acid content reaches 10 - 12% of the initial volume of the magnetic liquid, where spontaneously magnetized quasi-solid aggregates are formed, with a size not exceeding 2 μm, and the stirring process is carried out at a temperature of 18 - 20 °C [RU2375706C1, IPC G01N 27 / 84, published in 2009]. The known method ensures an improvement in the stability and resolution of the resulting magnetosensitive liquid.

[0005] A known method for preparing a magnetic liquid, the method includes mixing a hydrochloric acid solution of electroplating sludge with waste pickling liquor by Fe 3+ / Fe 2+Mix in a ratio of 3:2, and perform dispersion treatment by adding 28% ammonia water to the solution mixture to achieve the coprecipitation and interaction of divalent and trivalent iron oxides, obtaining a magnetite suspension. Coating the surface of magnetite particles with a stabilizer of the adsorption layer in an aqueous medium, heating the suspension of magnetic particles containing the adsorption layer stabilizer, separating it from the aqueous phase, and mixing it with a non-aqueous carrier liquid. After coprecipitating divalent and trivalent iron oxides, expose the suspension to an alternating magnetic field with a frequency of 50 Hz [RU 2276420 C1, IPC H01F1 / 28, published in 2006]. The present invention aims to improve the magnetic properties of magnetic liquids.

[0006] The problem to be solved by the present invention is to develop a suspension suitable for magnetic particle inspection (MPI), which can maximize the display of defect indication patterns (magnetic patterns) under the action of a magnetic field, thereby improving the indication ability of non-destructive testing (NDT).

[0007] When implementing the present invention, this problem is solved by achieving a technical effect, which lies in improving the sensitivity of ferromagnetic suspensions in detecting surface and near-surface defects by combining ferromagnetic particles with high dispersibility (not exceeding 30 μm) in its formulation and higher values of the roundness coefficient (ranging from 0.2 to 1.0) and sphericity coefficient (ranging from 0.25 to 1.0) of ferromagnetic particles at d50 (i.e., at least 50% of the total particle mass).

[0008] The above-mentioned technical effect is achieved in the following way: The MPI suspension contains an aqueous or hydrocarbon liquid carrier and a ferromagnetic powder made of ferromagnetic particles, which are based on iron-containing artificial waste, with an initial roundness and sphericity not less than 0.15, and have undergone dispersion and / or thermochemical treatment; and at 20 degrees Celsius, the kinematic viscosity of this suspension does not exceed 90 centistokes (cSt), and its component ratio (wt.%) is as follows: ferromagnetic powder, 0.05 - 90.0; liquid carrier, 10.0 - 99.95.

[0009] The sphericity and roundness of ferromagnetic particles in the suspension increase (see according to the Krumbein-Sloss diagram, Figure 1 )), reducing the magnetic field strength required to move the particles in the liquid carrier and / or on the surface of the object to be detected, thereby reducing the magnetic field concentration in the defect detection area.

[0010] The increase in the roundness coefficient will directly contribute to reducing the influence of viscosity on magnetic particles, thereby reducing the frictional force of the carrier liquid on ferromagnetic particles. Compared with particles with lower roundness (and thus rougher surfaces), the particles with the highest roundness will be subject to the least resistance when moving in a liquid or gas medium.

[0011] The increase in the sphericity coefficient will directly contribute to reducing the influence of the surface roughness of the object under study. High surface roughness may cause ferromagnetic particles to become trapped and / or immobilized between surface depressions and / or protrusions. Under the action of an external force, the particles with the highest sphericity coefficient can move on the surface, just like a sphere rolling on the surface, and the absolute value of the external force required for this movement is lower than the force required to drag the particles on the surface.

[0012] Experiments have confirmed the influence of the roundness coefficient and the sphericity coefficient on the indication ability of non-destructive testing (NDT) tools ( Figure 2 ).

[0013] The suspension is formed through the following steps:

[0014] Add the liquid carrier to the mixing tank (a pre-calculated amount, up to 100% of the expected volume). Add the required additives to the liquid according to the formulation requirements. Mix the components until homogeneous. Add the ferromagnetic particles to the resulting solution. Mix the components until homogeneous.

[0015] An aqueous solution containing a non-ionic surfactant (SAS) and an anti-corrosion additive (corrosion inhibitor) can be used as the water-based liquid carrier.

[0016] Oils based on hydrocarbon raw materials, where the mass fraction of aromatic compounds does not exceed 20% of the total mass, including fuels based on diesel fractions, paraffins, or isoparaffins, can be used as the hydrocarbon-based oil carriers.

[0017] For example, the following components were used in the experiments: a mixture of paraffins (C1-C28), mineral oil, synthetic oil, fuel fraction hydrocarbons (C5-C20), vegetable oil, and a mixture of alcohols (C1-C18).

[0018] A highly dispersed iron-containing powder from the artificial waste of a groundwater treatment plant, prepared by the method reported in RU 2755216C1, was used as the ferromagnetic powder. The concentration of the ferromagnetic particles can vary between 0.05% and 90.0 wt.% according to the requirements of the published technologies and technical specifications (such as GOST, technical specifications, ISO, etc.). The content of the liquid carrier can reach 100% of the total components (excluding the content of the ferromagnetic particles), depending on the concentration.

[0019] Table 1 lists possible formulation examples, including the boundary values of each component. Figure 2 The defect detection ability of the non-destructive testing tool was compared by referring to the visibility of the defect indication pattern (magnetic pattern).

[0020]

[0021] The above results are achieved by using ferromagnetic particles, which are obtained by exposing iron-containing artificial waste to dispersion and / or thermochemical action, with an initial roundness and sphericity of not less than 0.15, and the sphericity and roundness are visually determined according to the Krumbein-Sloss diagram, as Figure 1 shown.

[0022] The suspension proposed in the present invention is different from the known suspensions in that it contains ferromagnetic particles, and the preparation method of these particles is as follows:

[0023] Add a carbon-containing medium to the chemical iron compound prepared from artificial raw materials (such as the wastewater from a groundwater treatment plant or other wastewater), and treat it within the temperature range of 300 °C to 900 °C to form iron oxide. Subsequently, the obtained powder is processed by screening or other classification methods to obtain classified particles with a size not exceeding 30 μm (d50), and ultrasonic treatment with a power of not less than 40 W is carried out for at least 15 minutes. The treatment medium is alcohol, mineral oil, liquid paraffin / isoparaffin, or a mixed solution of water and SAS. After such treatment, the ferromagnetic particles do not coagulate and can remain suspended for a long time because alcohol molecules or SAS are adsorbed on the surface of the powder particles, thus forming an energy barrier at the interface between the particles and the liquid, preventing the ferromagnetic particles from spontaneously aggregating into a flaky structure. This helps to improve the quality of the suspension and the sensitivity of defect detection.

[0024] The boundary values of the suspension components are determined by the following requirements: ensuring that the final (total) viscosity of the suspension at 20 °C does not exceed 90 centistokes (cSt), and within 2 minutes after the end of complete mixing, the precipitation amount of the ferromagnetic particle mass does not exceed 40%.

[0025] During the non-destructive testing (NDT) process, the high sensitivity of the ferromagnetic suspension system to detect defects is achieved by controlling the roundness coefficient and sphericity coefficient at least at the levels of 0.2 and 0.25 respectively, which effectively reduces the frictional force of the particles on the surface of the object to be detected.

[0026] Formulas 2, 3, and 4 are determined as the patentable protection combination scope of the key components. The concentration of ferromagnetic particles in these formulas is sufficient to detect defects in steel and alloy products, and their rheological properties can also meet the requirements of their technical functions.

[0027] For example, Formula 2 has the best concentration when used under static conditions, where there is sufficient light (which reduces the requirements for saturation and visibility of the magnetic-sensitive particles in the defect detection indication pattern), and the shape of the object being inspected during the defect detection process is close to a flat surface (including the welded joints of pipes). In addition, this can also reduce the consumption of ferromagnetic particles per unit detection surface area, thereby improving economic and environmental benefits.

[0028] Formulation 3 is suitable for the inspection of parts with complex shapes (such as gears and racks) because the particle concentration in the suspension is relatively high, and more distinct indication patterns can be formed at the grooves of parts with complex shapes.

[0029] Formulation 4 is most effective for defect inspection under adverse weather conditions and / or in an environment with extremely high atmospheric humidity (for example, for defect inspection of the steel structure of an offshore oil platform). In this formulation, the maximum concentration of ferromagnetic particles is sufficient to ensure that when the area to be inspected is covered by a large amount of water (including in the form of wave splashes or atmospheric precipitation, such as rain and wet snow), the indication patterns left by the magnetosensitive particles on the area to be inspected can still remain visible.

[0030] However, the concentration of ferromagnetic particles in Formulation 1 is too low, which will have a very adverse effect on the defect detection ability because the saturation of the indication pattern used to evaluate the presence of defects is small.

[0031] On the contrary, Formulation 5 will contain a very high concentration of ferromagnetic particles (so the liquid carrier component is insufficient), which will have an extremely adverse effect on the rheological properties of the suspension: the final viscosity of the suspension will increase significantly, thus reducing the mobility of the ferromagnetic particles. On the other hand, the reduction in the mobility of the ferromagnetic particles will significantly reduce the formation rate of the defect indication pattern until the particles stop moving on the surface of the object to be inspected, or the interference of the too-high concentration of ferromagnetic particles on the object to be inspected is too strong, making it impossible to visually detect any defects against the overall background of the surface to be inspected.

[0032] In summary, using ferromagnetic particles with specific roundness coefficients and sphericity coefficients can reduce the total frictional force between the particles and the surfaces of the object under test and the liquid carrier. Therefore, less magnetic field force is required for defect inspection to activate the movement of the ferromagnetic particles, or at a standard magnetic field intensity, the time required to display the defect pattern will be shortened. Thus, this will improve the resolution of defect inspection using magnetosensitive liquids.

Claims

1. A suspension for magnetic particle inspection, containing water or a hydrocarbon-based liquid carrier and ferromagnetic powder containing ferromagnetic particles, wherein the d50 size of the ferromagnetic particles does not exceed 30 μm, characterized in that, The raw materials for preparing ferromagnetic particles are derived from iron-containing artificial waste. Among them, the roundness coefficient of the ferromagnetic particles in the suspension ranges from 0.2 to 1.0, and the sphericity coefficient is from 0.25 to 1.

0. The sphericity and roundness are visually determined according to the Krumbein-Sloss diagram. The component ratio (wt.%) is as follows: 。 2. The suspension according to claim 1, wherein An aqueous solution containing SAS and an anti-corrosion additive or alcohol is used as the liquid carrier.

3. The suspension according to claim 1, characterized in that Hydrocarbyl oil is used as the hydrocarbyl liquid carrier.

4. The suspension according to claim 1, wherein, Fuel fraction hydrocarbons are used as the hydrocarbyl liquid carrier.

5. The suspension according to claim 1, wherein Paraffin or isoparaffin is used as the hydrocarbyl liquid carrier.

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