Method and device for extracting inclusions in low-carbon low-alloy steel weld joints and application of method and device

Abstract

The invention relates to the field of welding, in particular to a method and device for extracting inclusions in a low-carbon low-alloy steel weld joint and application of the method and device. Taking the low-carbon low-alloy steel welding seam sample as an anode, and electrolyzing in the electrolyte; after electrolysis is completed, carrying out ultrasonic treatment, and adsorbing residual iron particles in the electrolyte; performing rough filtration, centrifugation and fine filtration; and the electrolyte comprises the following components in percentage by weight: 10%-15% of acetylacetone, 0.8%-1% of tetramethylammonium chloride, 0.3%-0.5% of 8-hydroxyquinoline, 0.2%-0.3% of thiourea and the balance of methanol. 8-hydroxyquinoline and thiourea are introduced, so that the damage of easily oxidized element inclusions such as Al and Ti can be prevented, and the dissolution of inclusions such as TiN and MnS can be inhibited; and Cl <-> is not added into the electrolyte, so that the problems of Fe < 3 + > deposition on the surfaces of inclusions and dissolution of the inclusions such as TiN and MnS caused by Cl <-> are avoided.

Description

Technical Field

[0001] The present invention relates to the field of welding, and in particular to a method for extracting inclusions from a low-carbon low-alloy steel weld, a device thereof, and applications thereof. Background Art

[0002] Non-metallic inclusions are unavoidable in steel and weld metal, typically consisting of oxides, sulfides, and nitrides. Oxides predominate in low-carbon, low-alloy steel weld metal. Weld metal inclusions significantly impact the material's strength, toughness, corrosion resistance, and weld joint reliability. Therefore, accurate analysis of the inclusions' chemical composition, size, morphology, and distribution is crucial.

[0003] In the prior art, the extraction methods of weld metal inclusions mainly include chemical extraction and electrolytic extraction. Among them, the chemical extraction method uses an acidic solution (such as hydrochloric acid, nitric acid) or a halide-alcohol system to dissolve the steel matrix, but this method easily causes the dissolution or morphological changes of certain important oxides (such as Al2O3), resulting in inaccurate inclusion analysis. The electrolytic extraction method uses the weld sample as the anode to retain the inclusions through the potential difference. However, traditional aqueous electrolytes (such as chloride aqueous solutions) easily cause the dissolution or deterioration of some inclusions, especially inclusions of easily oxidized metals such as Al and Ti are significantly affected. Even if a non-aqueous electrolyte (such as methanol-hydrochloric acid-glycerol) is used, Cl - Fe on the surface of inclusions 3+ The problem of deposition and easy dissolution of inclusions such as TiN and MnS (>20%).

[0004] Furthermore, existing technologies face significant recovery challenges for ultrafine inclusions measuring only 0.1 to 2 microns. These inclusions are easily lost through filter membranes or difficult to completely separate from the matrix during filtration and recovery, resulting in low recovery rates, inclusion damage, or even loss, which severely impacts the reliability of analytical results. Therefore, there is an urgent need to develop an extraction method that can target ultrafine inclusions (0.1 to 2 microns) to ensure efficient and complete extraction and analysis.

[0005] In addition, the electrolytic devices currently used for extracting inclusions from low-carbon low-alloy steel weld metals mainly use simple constant temperature or stirring devices, which have the following problems: (1) Temperature fluctuations affect the precipitation of inclusions: Traditional electrolytic devices mostly rely on simple water bath heating or natural cooling at room temperature, with low temperature control accuracy (±2-5°C), resulting in local overheating or uneven cooling rate during the electrolysis process, affecting the precipitation and morphological stability of inclusions. (2) Oxidation causes changes in the composition of inclusions: It is difficult to effectively control the oxygen content in open electrolytic cells, which will lead to Fe 3+ Sedimentation contaminates the surface of inclusions, affecting their true composition analysis.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The first object of the present invention is to provide a method for extracting inclusions from low-carbon low-alloy steel welds. By introducing 8-hydroxyquinoline and thiourea into the electrolyte, the method can effectively prevent the damage of inclusions of easily oxidized elements such as Al and Ti, and inhibit the dissolution of inclusions such as TiN and MnS, thereby solving the problem of dissolution or deterioration of inclusions of easily oxidized metals such as Al and Ti when using traditional aqueous electrolytes. In addition, no Cl is added to the electrolyte. - , avoiding the use of Cl in non-aqueous electrolytes - Fe on the surface of inclusions 3+ Deposition and the problem of easy dissolution of inclusions such as TiN and MnS.

[0008] The second object of the present invention is to provide an electrolytic device suitable for the above-mentioned method of extracting inclusions from low-carbon low-alloy steel welds, which can effectively prevent the dissolution or deterioration of inclusions such as Al and Ti, and inhibit the dissolution of inclusions such as TiN and MnS, and can also avoid Cl - Fe on the surface of inclusions 3+ Sedimentation problem.

[0009] The third object of the present invention is to provide a method for extracting inclusions from the above-mentioned low-carbon low-alloy steel weld or the use of the above-mentioned device in the preparation of welding materials.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0011] The present invention first provides a method for extracting inclusions from a low-carbon low-alloy steel weld, comprising the following steps: using a low-carbon low-alloy steel weld sample as an anode, providing a cathode, and performing electrolysis in an electrolyte; performing ultrasonication after the electrolysis is completed, and adsorbing residual iron particles in the electrolyte; and then performing coarse filtration, centrifugation, and fine filtration to obtain inclusions; wherein the electrolyte comprises the following components in weight percentage: 10% to 15% acetylacetone, 0.8% to 1% tetramethylammonium chloride, 0.3% to 0.5% 8-hydroxyquinoline, 0.2% to 0.3% thiourea, and the balance methanol.

[0012] Furthermore, the low carbon low alloy steel weld sample is ground and ultrasonically cleaned.

[0013] Furthermore, the voltage of the electrolysis is 18-22V, the current of the electrolysis is 0.6-0.7A, and the temperature of the electrolysis is 0-10°C.

[0014] Furthermore, during the electrolysis process, the electrolyte is magnetically stirred at a rotation speed of 50 to 100 rpm, wherein the magnets used for the magnetic stirring adsorb residual iron particles in the electrolyte during the electrolysis process.

[0015] Furthermore, during the magnetic stirring process, when the mass of the residual iron particles adsorbed by the magnetic particles is greater than 5 mg, the magnetic particles are ultrasonically cleaned.

[0016] Furthermore, a permanent magnet is used to adsorb the residual iron particles in the electrolyte multiple times.

[0017] Furthermore, the coarse filtration specifically includes: using an organic nylon filter membrane, a polytetrafluoroethylene filter membrane or a polypropylene filter membrane with a pore size of 20μm to 30μm to vacuum filter the electrolyte.

[0018] Furthermore, the centrifugation specifically includes: performing the centrifugation on the filtrate obtained after the coarse filtration, wherein the centrifugation speed is 10000-12000 rpm, and the centrifugation time is 20-30 minutes.

[0019] Furthermore, the fine filtration specifically includes: ultrasonically dispersing the precipitate obtained after the centrifugation with methanol or ethanol, and then vacuum filtering it through a polypropylene filter membrane with a pore size of 0.1 μm to 0.5 μm.

[0020] Furthermore, the inclusions include Al-Mn-Si-Ti-O(S,N) type inclusions.

[0021] Furthermore, the cathode includes a platinum electrode, a titanium electrode or a stainless steel electrode.

[0022] The present invention further provides a device, which is used for electrolysis in the above-mentioned method for extracting inclusions from low-carbon low-alloy steel welds; wherein the device includes an electrolysis container and an anode, a cathode and an electrolyte arranged in the electrolysis container; the anode and the cathode are also connected to a power supply.

[0023] Furthermore, the device also includes a magnetic stirrer arranged below the electrolysis container and a magnet located inside the electrolysis container.

[0024] Furthermore, the magneton comprises a magnetic stirring bar with a coating layer of polytetrafluoroethylene and a magnetic core of neodymium iron boron.

[0025] Furthermore, the electrolysis container includes a double-layer beaker, which is connected to a constant temperature water tank, and the water circulation pipe of the constant temperature water tank is connected to the interlayer of the double-layer beaker; and the top of the double-layer beaker has a sealing cover, and the anode and the cathode pass through the sealing cover.

[0026] Furthermore, the power supply includes a constant current power supply.

[0027] The present invention also provides a method for extracting inclusions from the low-carbon low-alloy steel weld or the use of the above-mentioned device in preparing welding materials.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The method for extracting inclusions from low-carbon low-alloy steel welds provided by the present invention can effectively prevent the damage of inclusions of easily oxidized elements such as Al and Ti by introducing 8-hydroxyquinoline and thiourea into the electrolyte, and inhibit the dissolution of inclusions such as TiN and MnS, thereby solving the problem of dissolution or deterioration of inclusions of easily oxidized metals such as Al and Ti when using traditional aqueous electrolytes. In addition, no Cl is added to the electrolyte. - , avoiding the use of Cl in non-aqueous electrolytes - Fe on the surface of inclusions 3 + Deposition and the problem of easy dissolution of inclusions such as TiN and MnS.

[0030] (2) The method for extracting inclusions from low-carbon low-alloy steel welds provided by the present invention can ensure uniform dissolution of the anode by controlling the voltage and current of electrolysis, so that the inclusions can be completely separated without changing or dissolving the inclusion composition due to excessively high potential, and can effectively retain the inclusions.

[0031] (3) The method for extracting inclusions from low-carbon low-alloy steel welds provided by the present invention controls the electrolysis temperature at 0-10°C. The low-temperature electrolysis environment helps to reduce local overheating during the electrolysis process, avoids phase changes or agglomeration of inclusions due to high-temperature reactions, improves the separation effect, and can effectively inhibit Fe 3+ Deposition protects the surface characteristics of inclusions, allowing them to maintain their true morphology and composition.

[0032] (4) The method for extracting inclusions from low-carbon, low-alloy steel welds provided by the present invention performs magnetic stirring at a speed of 50 to 100 rpm during electrolysis, thereby ensuring uniform distribution of inclusions in the electrolyte and improving extraction efficiency. This avoids the problem of small-sized inclusions settling, which results in severe loss of small-sized inclusions and low extraction efficiency, as is common with traditional stirring methods (such as magnetic stirring or mechanical stirring).

[0033] (5) The method for extracting inclusions from low-carbon, low-alloy steel welds provided by the present invention achieves effective extraction of ultrafine inclusions (0.1 to 2 microns), significantly improves the extraction efficiency and integrity of tiny inclusions (especially Al-Mn-Si-Ti-O(S,N) inclusions) (no obvious pits or cracks under SEM, no loss of EDS elements), and improves the reliability of analysis results, thereby providing an innovative and efficient solution for the precise analysis of inclusions in steel welds. It solves the problem of difficulty in recovering ultrafine inclusions (0.1 to 2 microns).

[0034] (6) The device provided by the present invention for electrolysis to extract inclusions from low-carbon low-alloy steel welds can effectively prevent the dissolution or deterioration of inclusions of easily oxidized elements such as Al and Ti, and inhibit the dissolution of inclusions such as TiN and MnS, and can also avoid Cl - Fe on the surface of inclusions 3+ Sedimentation problem.

[0035] (7) The device provided by the present invention integrates magnetic stirring and magnetic separation functions for the first time, avoiding mechanical damage to inclusions and effectively improving the inclusion recovery rate. The magnetic stirrer and magnet prevent the sedimentation of solid particles in the solution during electrolysis, maintaining a uniform distribution of the electrolyte; at the same time, the magnet can absorb residual iron particles produced after electrolysis.

[0036] (8) The device provided by the present invention adopts high-strength NdFeB core magnets, which can simultaneously realize magnetic separation and removal of iron residues during the stirring process, reduce inclusion pollution, and improve extraction purity.

[0037] (9) The device provided by the present invention can achieve precise temperature control of ±0.5°C by setting a double-layer beaker, a constant temperature water tank and a sealing cover, and adopting a water circulation interlayer temperature control, thereby avoiding uneven precipitation or morphological changes of inclusions caused by temperature fluctuations; combined with the sealing design, it can effectively reduce the infiltration of oxygen, reduce the damage to easily oxidized inclusions such as TiN and MnS, improve the accuracy of analysis, and realize a high-precision temperature control and anti-oxidation integrated design.

[0038] (10) The device provided by the present invention uses a constant current power supply to ensure that the current and voltage remain stable during the electrolysis process, thereby improving the repeatability and accuracy of the electrolysis. This avoids the problem of inclusion dissolution or deposition caused by current fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 A schematic structural diagram of the device provided by the present invention;

[0041] Figure 2 The typical composite inclusion morphology and surface scanning results extracted in Example 1 provided by the present invention;

[0042] Figure 3 The typical composite inclusion morphology and surface scanning results extracted in Example 2 provided by the present invention;

[0043] Figure 4 The typical composite inclusion morphology and surface scanning results extracted in Example 3 provided by the present invention;

[0044] Figure 5 The typical composite inclusion morphology and surface scanning results extracted in Example 4 provided by the present invention;

[0045] Figure 6 The typical composite inclusion morphology and surface scanning results extracted in Example 5 provided by the present invention;

[0046] Figure 7 The typical composite inclusion morphology and surface scanning results extracted from Comparative Example 1 provided by the present invention;

[0047] Figure 8 The typical composite inclusion morphology and surface scanning results extracted in Comparative Example 2 provided by the present invention;

[0048] Figure 9 This is a morphology diagram of a typical incomplete inclusion extracted in Comparative Example 3 provided by the present invention.

[0049] Reference numerals:

[0050] 11-electrolysis container; 12-anode; 13-cathode; 14-magnetic stirrer; 15-magnet; 16-sealing cover; 2-power supply; 3-constant temperature water tank. DETAILED DESCRIPTION

[0051] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0052] Unless otherwise specified, in the present invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," "third," and "fourth" serve only as non-exhaustive enumeration and description, and should not constitute closed-ended limitations on quantity.

[0053] Unless otherwise specified, the terms "include" and "comprising" used in the present invention may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0054] Unless otherwise specified, in the present invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. Among them, "several" refers to any two or any two or more.

[0055] In a first aspect, the present invention provides a method for extracting inclusions from low-carbon, low-alloy steel welds, comprising the following steps: using a low-carbon, low-alloy steel weld sample as an anode 12, inserting the bottoms of anode 12 and cathode 13 into an electrolyte, applying power to perform electrolysis, and retaining inclusions through potential differences. After the electrolysis is complete, ultrasonication is performed to adsorb residual iron particles from the electrolyte; and then, coarse filtration, centrifugation, and fine filtration are sequentially performed to obtain the inclusions.

[0056] Ultrasound plays a key role in this process: after electrolysis, inclusion particles often adhere to the magnet 15, the beaker walls, or aggregate into clusters; it disperses these clusters, preventing flocculation and sedimentation. Compared to mechanical stirring or scrubbing, low-frequency (20-40 kHz) short-duration ultrasound, under properly controlled conditions, is gentler on inclusions and preserves their original appearance. During the electrolytic extraction process, ultrasound acts as both a "cleaner" and a "dispersant," effectively improving inclusion recovery and characterization accuracy.

[0057] The purpose of coarse filtration is to: The post-electrolysis solution often contains large, non-inclusion solids such as anode 12 debris, oxide scale, residual matrix flakes, and ferromagnetic agglomerates. If these impurities enter the 0.5μm fine filter membrane directly without coarse filtration, they can easily cause membrane blockage, leading to filtration failure or inclusion retention. Coarse filtration provides a clearer filtrate, preventing large particles from affecting the centrifugal fractionation sedimentation curve. It significantly improves the stratified sedimentation efficiency of 0.5-20μm inclusions and reduces the "crowding" of target inclusions by interfering particles. Furthermore, inclusions on the filter membrane are free of secondary dissolution risk, making them suitable for subsequent SEM observation.

[0058] Fine filtration is a key step in the inclusion extraction process to achieve the ultimate high-purity, high-integrity inclusion enrichment. Compared to coarse filtration, it is more precise and targets ultrafine inclusions of 0.1-2μm, achieving inclusion concentration and enrichment.

[0059] The electrolyte comprises the following components by weight: 10% to 15% acetylacetone, 0.8% to 1% tetramethylammonium chloride, 0.3% to 0.5% 8-hydroxyquinoline, 0.2% to 0.3% thiourea, and the balance methanol, wherein the total weight percentage of the components is 100%.

[0060] Wherein, acetylacetone includes but is not limited to any one of 10%, 11%, 12%, 13%, 14%, and 15% by weight or a range between any two of them; tetramethylammonium chloride includes but is not limited to any one of 0.8%, 0.85%, 0.9%, 0.95%, and 1% by weight or a range between any two of them; 8-hydroxyquinoline includes but is not limited to any one of 0.3%, 0.35%, 0.4%, 0.45%, and 0.5% by weight or a range between any two of them; thiourea includes but is not limited to any one of 0.2%, 0.22%, 0.23%, 0.25%, 0.28%, and 0.3% by weight or a range between any two of them.

[0061] In the electrolyte provided by the present invention, acetylacetone is used as the main complexing agent to reduce the iron dissolution potential, capture free radicals, and protect the surface integrity of inclusions; tetramethylammonium chloride ensures the conductivity of the electrolyte and forms a Helmholtz layer to inhibit the hydrogen evolution side reaction; 8-hydroxyquinoline preferentially complexes Al 3+ With Ti 4+ , and buffer the electrolyte pH to stabilize; thiourea through S 2- Competitive adsorption mechanism effectively prevents the dissolution of MnS inclusions.

[0062] The present invention innovatively introduces 8-hydroxyquinoline and thiourea into the electrolyte, which can effectively prevent the damage of inclusions of easily oxidized elements such as Al and Ti, and inhibit the dissolution of inclusions such as TiN and MnS, thus solving the problem of dissolution or deterioration of inclusions of easily oxidized metals such as Al and Ti when using traditional aqueous electrolytes. In addition, no Cl is added to the electrolyte. - , avoiding the use of Cl in non-aqueous electrolytes - Fe on the surface of inclusions 3+ Deposition and the problem of easy dissolution of inclusions such as TiN and MnS.

[0063] In some specific embodiments, the methanol is analytical grade pure methanol.

[0064] In some specific embodiments, the method for preparing the electrolyte includes: mixing the raw materials uniformly.

[0065] In some specific embodiments, the low carbon low alloy steel weld sample is ground with sandpaper and ultrasonically cleaned during the preparation process.

[0066] In some specific embodiments, the preparation method of the low-carbon low-alloy steel weld sample includes: cutting the low-carbon low-alloy steel weld into a block sample, such as a block sample with a length of 10 mm, a width of 10 mm, and a thickness of 2 mm; then grinding the surface thereof, for example, using 1500-grit sandpaper; and then ultrasonically cleaning with an organic solvent such as ethanol to completely remove contaminants on the surface of the block sample.

[0067] In some specific embodiments, the electrolysis voltage is 18-22 V, including but not limited to any one of 18 V, 19 V, 20 V, 21 V, and 22 V, or a range between any two of them.

[0068] In some specific embodiments, the electrolysis current is 0.6-0.7 A, including but not limited to any one of 0.6 A, 0.63 A, 0.65 A, 0.68 A, and 0.7 A, or a range between any two of them.

[0069] The present invention can ensure uniform dissolution of the anode 12 by controlling the voltage and current of electrolysis, so that inclusions can be completely separated without changing or dissolving the inclusion composition due to excessively high potential, thereby effectively retaining the inclusions.

[0070] In some specific embodiments, the electrolysis temperature is 0-10°C, including but not limited to any one of 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, and 10°C, or a range between any two of them.

[0071] The present invention controls the electrolysis temperature at 0-10°C. The low-temperature electrolysis environment helps to reduce local overheating during the electrolysis process, avoids phase change or agglomeration of inclusions due to high-temperature reaction, improves separation effect, and can effectively inhibit Fe 3+ Deposition protects the surface characteristics of inclusions, allowing them to maintain their true morphology and composition.

[0072] In some specific embodiments, during the electrolysis process, the electrolyte is magnetically stirred at a speed of 50 to 100 rpm, wherein the magnetic stirring magnet 15 used for the magnetic stirring adsorbs residual iron particles in the electrolyte during the electrolysis process. The speed of the magnetic stirring includes but is not limited to any one of 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, and 100 rpm, or a range of values ​​therebetween.

[0073] During the electrolysis process, magnetic stirring at a speed of 50-100 rpm ensures uniform distribution of inclusions in the electrolyte, improving extraction efficiency. This avoids the problem of traditional stirring methods (such as magnetic stirring or mechanical stirring) that causes small inclusions to settle, resulting in severe loss of small inclusions and low extraction efficiency.

[0074] In some specific embodiments, during the magnetic stirring process, when the mass of the residual iron particles adsorbed by the magnetic particle 15 is greater than 5 mg, the magnetic particle 15 is ultrasonically cleaned.

[0075] In some specific embodiments, a permanent magnet is used to adsorb residual iron particles generated in the electrolyte after electrolysis multiple times, for example, 2 times, 3 times, 5 times or more times.

[0076] In some specific embodiments, after the electrolysis is completed, the container used for the electrolysis is placed in an ultrasonic cleaning device and treated at 30-50 kHz for 10-15 minutes, with the temperature controlled below 10°C; then, the permanent magnet is attached to the wall of the container to adsorb residual iron impurities, the number of adsorptions is at least 3 times, and the adsorption time is 3-5 minutes each time.

[0077] In some specific embodiments, the coarse filtration specifically includes: using an organic nylon filter membrane, a polytetrafluoroethylene filter membrane or a polypropylene filter membrane with a pore size of 20 μm to 30 μm to vacuum filter the electrolyte.

[0078] Using the filter membrane with the above pore size for coarse filtration can effectively remove large particles of impurities >20μm, undissolved anode 12 residue, oxide scale, etc., while retaining the target particle size inclusions in the filtrate to avoid premature loss; first using a 20μm~30μm filter membrane for coarse filtration can significantly reduce the clogging risk of the subsequent 0.5μm filter membrane, extend its service life, avoid "membrane clogging loss" due to inclusions, and cooperate with centrifugation, fine filtration and other operations to achieve graded extraction of the particle size distribution of inclusions.

[0079] The above-mentioned filter membranes can be used for coarse filtration without pre-wetting and can be directly used for filtration of water systems or polar organic solvents (such as methanol), with wide compatibility. They are suitable for use in suction filtration and vacuum filtration, are not easily damaged, and are especially stable under low vacuum (<0.05MPa). They are not easy to adsorb elements on the particle surface, are suitable for subsequent SEM / EDS analysis, and retain inclusions intact.

[0080] In some specific embodiments, during the vacuum filtration process, the vacuum degree is controlled to be lower than -0.05 MPa to prevent the nylon filter membrane from being damaged.

[0081] In some specific embodiments, during the coarse filtration process, every time 80 to 100 mL of filtration is performed, the nylon filter membrane is paused and backwashed with 5 mL of methanol.

[0082] In some specific embodiments, the centrifugation comprises: performing centrifugation on the filtrate obtained after the coarse filtration, wherein the centrifugation speed is 10,000 to 12,000 rpm, the centrifugation time is 20 to 30 minutes, the centrifugation volume is ≤ 75%, and particles with a particle size of 0.5 to 20 μm can be precipitated by the centrifugation.

[0083] In some specific embodiments, the fine filtration comprises: ultrasonically dispersing the precipitate obtained after the centrifugation with methanol or ethanol, followed by vacuum filtration through a polypropylene filter membrane with a pore size of 0.1 μm to 0.5 μm. Specifically, the precipitate obtained after the centrifugation is resuspended in 10 to 20 mL of methanol and ultrasonically dispersed at 20 to 30 kHz for 3 to 5 minutes; then vacuum filtration is performed through a polypropylene filter membrane with a pore size of 0.5 μm; and then rinsing with anhydrous ethanol 3 to 5 times to concentrate the inclusions on the polypropylene filter membrane.

[0084] Fine filtration using membranes with these pore sizes effectively intercepts inclusion particles 0.5 to 2 μm and smaller, making them particularly suitable for fine inclusions such as TiO2, Al2O3, and MnS, commonly found in welds. Coarser pore sizes (e.g., 1 μm and 5 μm) result in high leakage rates when processing inclusions near the lower size limit (0.1 to 1 μm), while pore sizes of 0.5 μm significantly improve the integrity and statistical representativeness of inclusion recovery.

[0085] Polypropylene filter membrane is used for fine filtration. Polypropylene can stably tolerate methanol, common complexing agents (such as acetylacetone) and auxiliary components in electrolytes, and will not swell or release background pollution. It is not easy to adhere to or surface-bind with inclusion particles, which facilitates the concentration of inclusions on the membrane surface to form a clear deposition image. It can withstand a certain filtration pressure, is not easy to break, wrinkle or perforate, has high operational stability, and is suitable for repeated flushing.

[0086] The present invention utilizes multi-layer filtration (coarse filtration, centrifugation, and fine filtration in sequence), reduces the pore size of the filter membrane, increases the centrifugal speed, and performs magnetic separation to recover ultrafine inclusions sized 0.1 to 2 microns. This solves the problem of ultrafine inclusions easily slipping through the filter membrane or being difficult to completely separate from the substrate during the filtration and recovery process, resulting in low recovery rates, inclusion damage, and even loss.

[0087] In some specific embodiments, the inclusions include Al-Mn-Si-Ti-O(S,N) type inclusions, that is, the inclusions are mainly single or composite inclusions of the Al-Mn-Si-Ti-O(S,N) series.

[0088] In the weld metal of low-carbon low-alloy steel, oxide inclusions are the most common, mainly including Al2O3, MnO, SiO2, TiO2, etc. Sulfides (such as MnS), nitrides (such as TiN) and composite inclusions (such as Al2O3-TiO2, MnO-TiO2-SiO2, Si-Mn-Al-Ti-OS and other oxidation-sulfide composite inclusions) may also exist and have an important impact on the structure and properties of the weld metal. Therefore, the precise extraction and analysis of inclusions is not limited to a certain type, but requires comprehensive coverage of the various types that may exist in the weld metal. The inclusions include single-phase or composite-phase particles such as Al2O3, MnO-SiO2, TiO2, MnS, etc., which may be spherical, polyhedral or agglomerated. The electrolyte system and ultrafine separation process provided by the present invention can effectively inhibit the dissolution and morphological destruction of soluble inclusions, and achieve wide coverage and high-fidelity extraction of fine inclusions.

[0089] In some specific embodiments, the size of the inclusions is 0.1 to 2 microns.

[0090] This invention effectively extracts ultrafine inclusions (0.1 to 2 microns), significantly improving the extraction efficiency and integrity of tiny inclusions (especially Al-Mn-Si-Ti-O(S,N) inclusions), and enhancing the reliability of analysis results. This provides an innovative and efficient solution for the precise analysis of inclusions in steel welds, resolving the difficulty in recovering ultrafine inclusions (0.1 to 2 microns).

[0091] In some specific embodiments, the cathode 13 is a platinum electrode, a titanium electrode or a 316 stainless steel electrode.

[0092] In some specific embodiments, the pH value of the electrolyte is monitored in real time during the electrolysis process, and when the pH value exceeds the range of 6.5 to 7.0, 8-hydroxyquinoline is added to adjust the pH.

[0093] The present invention establishes a stable buffer complex system by real-time monitoring of the electrolyte pH and dynamic supplementation of 8-hydroxyquinoline, effectively inhibiting the dissolution of Al / Ti inclusions and the formation of Fe 3+ It can eliminate sediment pollution, ensure the integrity of inclusion morphology and composition, and improve extraction efficiency and analysis accuracy.

[0094] During the electrolysis process, due to Fe 2+ / Fe 3+ Oxidation-reduction, water side reactions or complexing agent consumption can cause pH drift; acidic pH (<6.5) can cause some oxide inclusions (such as Al2O3, TiO2) to partially dissolve; alkaline pH (>7.0) can cause Fe 3+ Hydrolysis precipitates Fe(OH)3 colloids, which adhere to the surface of inclusions and interfere with analysis. Therefore, the pH must be precisely controlled within a buffer range of 6.5 to 7.0 to inhibit inclusion dissolution and Fe ion deposition. In some specific embodiments, a polypropylene filter containing extracted inclusions is adhered to a copper sample holder using conductive adhesive. After gold coating, the size, morphology, and chemical composition of the inclusions are analyzed using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) system.

[0095] In a second aspect, the present invention provides a device, which is an electrolysis device, and is used to implement the electrolysis in the above-mentioned method for extracting inclusions from low-carbon low-alloy steel welds. After electrolysis, the device can dissolve iron and precipitate inclusions; wherein, the device includes an electrolysis container 11 and an anode 12, a cathode 13 and an electrolyte arranged in the electrolysis container 11; the anode 12 and the cathode 13 are also connected to a power supply 2.

[0096] See also Figure 1 , which is a schematic structural diagram of the device provided by the present invention.

[0097] It is understood that the anode 12 and the cathode 13 are at least partially located within the electrolysis container 11, for example, the bottom and middle portions of the anode 12 and the cathode 13 are located within the electrolysis container 11. The tops of the anode 12 and the cathode 13 may be exposed from the electrolysis container 11 to connect to the positive and negative electrodes of the power source 2. The electrolyte at least covers the bottoms of the anode 12 and the cathode 13.

[0098] The device provided by the present invention is used for extracting inclusions from low-carbon low-alloy steel welds, which can effectively prevent the dissolution or deterioration of inclusions such as Al and Ti, and inhibit the dissolution of inclusions such as TiN and MnS, and can also avoid Cl - Fe on the surface of inclusions 3+ Sedimentation problem.

[0099] In some specific embodiments, see Figure 1 As shown, the device further comprises a magnetic stirrer 14 disposed below the electrolysis container 11 and a magneton 15 located inside the electrolysis container 11. The magneton is also called a rotor or a stirrer.

[0100] The magnetic separation function in the prior art is usually performed as a separate step, which makes it impossible to simultaneously remove iron residue during the electrolysis process, increasing the complexity of subsequent separation. However, the magnetic stirrer 14 and magnet 15 in the present invention are used to prevent the sedimentation of solid particles in the solution during the electrolysis process, maintaining a uniform distribution of the electrolyte; at the same time, the magnet 15 can adsorb residual iron particles produced after electrolysis. In other words, the present invention has achieved the integration of magnetic stirring and magnetic separation functions for the first time, avoiding mechanical damage to inclusions and effectively improving the inclusion recovery rate.

[0101] In some specific embodiments, the magnet 15 comprises a magnetic stirring bar with a coating layer of polytetrafluoroethylene and a magnetic core of neodymium iron boron, that is, polytetrafluoroethylene is coated on the outer surface of the neodymium iron boron magnetic core.

[0102] The high-strength NdFeB core (PTFE coated) magnet 15 has a high magnetic force of ≥12N. The recovery rate of Fe particles of the magnet 15 within a distance of 1cm is >95%, and the cumulative iron slag mass can reach 5-8mg, effectively improving the filter membrane transmittance.

[0103] The present invention adopts a high-strength NdFeB core magnet 15, which can simultaneously realize magnetic separation and removal of iron residues during the stirring process, reduce inclusion pollution, and improve extraction purity.

[0104] In some specific embodiments, see Figure 1 As shown, the electrolysis container 11 includes a double-layer beaker connected to a constant-temperature water tank 3. The water circulation pipe of the constant-temperature water tank 3 is connected to the interlayer of the double-layer beaker. At the same time, the top of the double-layer beaker has a sealing cover 16, and the anode 12 and the cathode 13 pass through the sealing cover 16.

[0105] It is understandable that the anode 12 and the cathode 13 pass through the sealing cover 16 respectively, and there is no gap between the anode 12 and the sealing cover 16, and between the cathode 13 and the sealing cover 16, so as to ensure the sealing effect of the double-layer beaker interlayer and the interior.

[0106] It is understood that the double-layer beaker has a double-layer glass structure, with an outer layer of glass and an inner layer of glass from the outside to the inside. The outer and inner layers of glass form an interlayer, into which circulating water from a constant temperature water tank 3 flows to control the temperature. The anode 12, cathode 13, and electrolyte are located within the inner layer of glass.

[0107] The main function of the constant temperature water tank 3 is to maintain the temperature of the electrolyte within a set range during the electrolysis process to ensure stable experimental conditions.

[0108] The present invention adopts a water circulation interlayer temperature control by setting a double-layer beaker, a constant temperature water tank 3 and a sealing cover 16, which can achieve precise temperature control of ±0.5°C, avoiding uneven precipitation of inclusions or changes in morphology caused by temperature fluctuations; combined with the sealing design, it can effectively reduce the infiltration of oxygen, reduce the damage of easily oxidized inclusions such as TiN and MnS, and improve the accuracy of analysis, thereby realizing a high-precision temperature control and anti-oxidation integrated design. It solves the problems of local overheating or uneven cooling rate in the electrolysis process of traditional electrolysis devices, which affect the precipitation and morphological stability of inclusions, and the difficulty of effectively controlling the oxygen content in open electrolytic cells, which leads to Fe 3+ The problem of sediment contamination on the surface of inclusions.

[0109] In some specific embodiments, the power supply 2 includes a constant current power supply 2. Using a constant current power supply 2 can ensure that the current and voltage remain stable during the electrolysis process, thereby improving the repeatability and accuracy of the electrolysis and avoiding the problem of inclusion dissolution or deposition caused by current fluctuations.

[0110] The present invention proposes for the first time an integrated temperature-controlled and anti-oxidation electrolysis device that simultaneously achieves precise temperature control and a low-oxygen environment. The device has both precise temperature control (the interlayer of the double-layer beaker connected to the water circulation pipe of the constant-temperature water tank 3 has a temperature control accuracy of ±0.5°C) and a sealing function (a sealing cover 16 is provided), avoiding the analysis errors caused by temperature fluctuations and oxidation damage to inclusions in the prior art, and further ensuring the high accuracy and reliability of the inclusion analysis results.

[0111] In a third aspect, the present invention provides the aforementioned method for extracting inclusions from low-carbon, low-alloy steel welds, or the use of the aforementioned device in the preparation of welding materials. The inclusions extracted by the aforementioned method or device, after compositional analysis and correlation with the mechanical properties of the weld metal, can be used to adjust the flux alloying level or process window, thereby improving weld quality.

[0112] Among them, welding materials refer to the materials consumed during welding, including welding rods, welding wires, flux, etc.

[0113] Inclusions (especially micron-sized and submicron-sized inclusions) have a direct impact on the strength, toughness, fatigue life, fracture behavior, corrosion resistance and other properties of steel. Traditional two-dimensional observation is prone to misjudgment of inclusion size, morphology distortion and composition analysis errors due to the limitation of cutting section. Through the three-dimensional extraction method, the complete separation and pollution-free analysis of inclusions can be achieved, and their size, morphology and distribution characteristics can be truly reflected, which significantly improves the accuracy and reliability of the research on fine inclusions. The present invention can guide the design of welding materials and the strengthening of weld metal by extracting and analyzing fine inclusions. Therefore, the method for extracting inclusions in low-carbon low-alloy steel welds and the device thereof provided by the present invention have broad application prospects.

[0114] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0115] Example 1

[0116] The method for extracting inclusions from a low-carbon low-alloy steel weld provided in this embodiment comprises the following steps:

[0117] (1) Preparation of electrolyte: The electrolyte consists of the following components in weight percentage: 12% acetylacetone, 0.9% tetramethylammonium chloride, 0.4% 8-hydroxyquinoline, 0.25% thiourea, and the balance is analytical grade methanol. The electrolyte preparation process is as follows: 12g acetylacetone, 0.9g tetramethylammonium chloride, 0.4g 8-hydroxyquinoline, and 0.25g thiourea are weighed and added to a 200mL beaker in sequence; methanol is then slowly added to the mixture to a total mass of 100g, and magnetic stirring (500rpm) is performed until the mixture is completely dissolved (15min); the electrolyte is stored in a brown glass bottle in the dark, and argon gas (flow rate 0.1L / min) is introduced for deoxygenation for 10min before use.

[0118] (2) Preparation of low-carbon low-alloy steel weld specimens: Take a low-carbon low-alloy steel weld (size: length 10 mm × width 10 mm × thickness 2 mm), and polish the surface of the low-carbon low-alloy steel weld in sequence with 600-grit sandpaper, 1200-grit sandpaper, and 1500-grit sandpaper. Then, ultrasonically clean the weld with acetone three times (10 min each time), blow dry with cold air, and weigh (accuracy 0.1 mg) to obtain a low-carbon low-alloy steel weld specimen.

[0119] (3) Electrolysis: The electrolysis device includes a double-layer beaker, the low-carbon low-alloy steel weld sample obtained in step (2) is used as the anode 12, and the platinum electrode (platinum sheet, area 1cm 2, purity 99.99%) as cathode 13, the anode 12 and cathode 13 are placed in a double-layer beaker, and NdFeB magnet 15 (the coating layer is polytetrafluoroethylene, the magnetic core is NdFeB, and its magnetic force is 12N) and the electrolyte prepared in step (1) are added into the double-layer beaker, and then the sealing cover 16 is covered (the sealing cover 16 is located at the top of the double-layer beaker, and the anode 12 and cathode 13 pass through the sealing cover 16, as shown Figure 1 As shown). Place the assembled double-layer beaker on the magnetic stirrer 14, and connect the anode 12 and the cathode 13 to the constant current power supply 2. At the same time, connect the assembled double-layer beaker to the constant temperature water tank 3 (the water circulation pipe of the constant temperature water tank 3 is connected to the interlayer of the double-layer beaker). Then start electrolysis, wherein the electrolysis voltage is 20V (DC regulated power supply, accuracy ±1mV), the electrolysis current is 0.65A (constant current mode, fluctuation range ±0.5mA), and the electrolysis temperature is 5°C (circulating water bath temperature control, fluctuation range ±0.5°C). During the electrolysis process, the electrolyte is magnetically stirred at a speed of 80rpm, and the NdFeB magnets 15 adsorb residual iron particles in the electrolyte. Monitoring of the electrolysis process: The electrolysis was paused every 10 minutes, the NdFeB magnet 15 was removed, and the NdFeB magnet was ultrasonically cleaned with anhydrous ethanol for 30 seconds to remove residual iron particles adsorbed thereon (a cumulative removal of 3.5 mg). The pH value of the electrolyte was monitored in real time. When the pH value exceeded the range of 6.5 to 7.0, 8-hydroxyquinoline was added to adjust the pH value.

[0120] (4) Gradient separation:

[0121] Pretreatment: The electrolyte after electrolysis was transferred to a 50 mL polytetrafluoroethylene beaker and placed in a 40 kHz ultrasonic cleaner for 10 min (temperature 8°C). Subsequently, a permanent magnet (surface magnetic field strength 0.5 T) was attached to the outer wall of the double-layer beaker to adsorb residual iron particles. The adsorption was repeated three times, and a total of 8 mg of iron slag was removed.

[0122] Coarse filtration: Use a nylon filter membrane with a pore size of 20 μm to vacuum filter the electrolyte (vacuum degree -0.04 MPa). Pause after filtering every 100 mL of electrolyte and reversely flush the filter membrane with 5 mL of methanol to prevent clogging.

[0123] Centrifugation: The filtrate obtained after coarse filtration was transferred to a 50 mL conical bottom centrifuge tube (70% filling volume) and centrifuged at 12000 rpm for 30 min to obtain a precipitate containing inclusions of 0.5 to 18 μm.

[0124] Fine filtration: The precipitate obtained after centrifugation was ultrasonically dispersed (25 kHz × 2 min) in 15 mL of methanol, then vacuum filtered through a polypropylene filter with a pore size of 0.5 μm and rinsed four times with anhydrous ethanol to ensure that the inclusions were completely transferred to the center of the filter membrane.

[0125] Detection and Analysis: The polypropylene filter membrane with inclusions obtained in step (4) was fixed to a copper sample stage with conductive glue (silver glue) and gold-sprayed (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis (SEM, accelerating voltage 15 kV, working distance 15 mm) was then performed. The results showed that the inclusions were Al-Mn-Si-ON composite phases, ellipsoidal in shape, see Figure 2 As shown, the size distribution is below 1μm, and the inclusions are intact without corrosion pits. In addition, the significant coexistence of Ti and N elements was detected in the extracted inclusions, which were judged to be TiN nitride inclusions, indicating that this system has good protection capabilities for TiN inclusions.

[0126] Example 2

[0127] The method for extracting inclusions from low-carbon low-alloy steel welds provided in this embodiment is basically the same as that in Example 1, except that: in step (3), the electrolysis voltage is 22 V (DC regulated power supply, accuracy ±1 mV), the electrolysis current is 0.7 A (constant current mode, fluctuation range ±0.5 mA), and the electrolysis temperature is 10°C (circulating water bath temperature control, fluctuation range ±0.5°C).

[0128] Detection and Analysis: The polypropylene filter membrane with inclusions obtained in this example was fixed to a copper sample stage with conductive adhesive and gold-sprayed (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). SEM observation showed that the inclusions were ellipsoidal (see Figure 3 ); EDS surface scanning analysis showed that the main components of the inclusions were Al-Mn-Si-Ti-O(S), confirming that the sulfide (MnS) was not dissolved, proving that the corrosion inhibition effect of thiourea was effective; the particle size distribution was below 1μm, which was consistent with the typical characteristics of low-carbon steel weld inclusions.

[0129] Example 3

[0130] The method for extracting inclusions from low-carbon low-alloy steel welds provided in this embodiment is basically the same as that in Example 1, except that: in step (1), the electrolyte is composed of the following components in weight percentage: 10% acetylacetone, 0.8% tetramethylammonium chloride, 0.5% 8-hydroxyquinoline, 0.3% thiourea, and the balance is analytical grade methanol.

[0131] Testing and Analysis: The polypropylene filter membrane with inclusions obtained in this example was fixed to a copper sample stage using conductive glue (silver glue) and then gold-sputtered (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). Figure 4The morphology and surface scan results of the Al-Mn-Si-Ti-O(S) composite inclusion extracted in Example 3 are shown. The inclusion size is 1 μm and the inclusion is intact, indicating that the synergistic protection effect of increasing the 8-hydroxyquinoline and thiourea content is good, effectively stabilizing the Ti and S-containing inclusions.

[0132] Example 4

[0133] The method for extracting inclusions from low-carbon low-alloy steel welds provided in this embodiment is basically the same as that in Example 1, except that: in step (1), the electrolyte is composed of the following components in weight percentage: 15% acetylacetone, 1% tetramethylammonium chloride, 0.3% 8-hydroxyquinoline, 0.2% thiourea, and the balance is analytical grade methanol.

[0134] Testing and Analysis: The polypropylene filter membrane with inclusions obtained in this example was fixed to a copper sample stage using conductive glue (silver glue) and then gold-sputtered (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). Figure 5 The morphology and surface scan results of the Al-Mn-Si-Ti-O(S) composite inclusion extracted in Example 4 are shown. The inclusion has a regular morphology, clear boundaries, and no obvious cracks on the surface. The EDS surface scan shows that the Al, Mn, Si, Ti, and S elements are evenly distributed, indicating that no element migration or inclusion structure damage occurred during the electrolysis process. The overall composition of the inclusion is consistent with typical multi-component oxide-sulfide inclusions in low-carbon, low-alloy steel welds.

[0135] Example 5

[0136] The method for extracting inclusions from low-carbon low-alloy steel welds provided in this embodiment is basically the same as that in Example 1, except that: in step (3), the electrolysis voltage is 18 V (DC regulated power supply, accuracy ±1 mV), the electrolysis current is 0.6 A (constant current mode, fluctuation range ±0.5 mA), the electrolysis temperature is 1°C (circulating water bath temperature control, fluctuation range ±0.5°C), and the magnetic stirring speed during the electrolysis process is 50 rpm.

[0137] Testing and Analysis: The polypropylene filter membrane with inclusions obtained in this example was fixed to a copper sample holder using conductive adhesive and then gold-sputtered (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). Figure 6The morphology and surface scan results of the composite inclusions extracted in Example 5 are shown. The inclusions extracted by electrolytic extraction contain two particles of varying sizes. The larger particle is a regular spherical Al-Mn-Si-O oxide inclusion. The smaller particle contains both Ti and N, with a Ti:N signal ratio approaching 1:1. Combined with its independent distribution and dense morphology, it is identified as a typical TiN inclusion. This result demonstrates that the electrolytic method proposed in this invention is effective in extracting nitride inclusions, including TiN.

[0138] Comparative Example 1

[0139] The method for extracting inclusions from a low-carbon, low-alloy steel weld provided in this comparative example is substantially the same as that of Example 1, except that in step (1), the electrolyte does not contain (is not added with) 8-hydroxyquinoline. Specifically, the electrolyte is composed of the following components, by weight percentage: 12% acetylacetone, 0.9% tetramethylammonium chloride, 0.25% thiourea, and the balance being analytical grade methanol.

[0140] Detection and Analysis: The polypropylene filter membrane with inclusions obtained in this comparative example was fixed to a copper sample stage with conductive glue (silver glue) and gold-sprayed (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, acceleration voltage 15 kV, working distance 10 mm). The scanning electron microscopy results showed that the inclusions were Al-Mn-Si-Ti-O(S) composite phases, but some of the inclusions showed slight oxidation characteristics on their surfaces. Sulfide (MnS) was detected, but only on the left side of the inclusions. It is speculated that the sulfide (MnS) was not completely dissolved due to the lack of 8-hydroxyquinoline addition, proving that the corrosion inhibition effect of thiourea is effective (see Figure 7 shown).

[0141] Comparative Example 2

[0142] The method for extracting inclusions from a low-carbon, low-alloy steel weld provided in this comparative example is substantially the same as that of Example 1, except that in step (1), the electrolyte does not contain (is not added with) thiourea. Specifically, the electrolyte is composed of the following components, by weight percentage: 12% acetylacetone, 0.9% tetramethylammonium chloride, 0.4% 8-hydroxyquinoline, and the balance being analytical grade methanol.

[0143] Testing and Analysis: The polypropylene filter membrane with inclusions obtained in this comparative example was fixed to a copper sample holder using conductive glue (silver glue) and gold-sprayed (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). The SEM results showed that the inclusions were Al-Mn-Si-O composite phases, but the surface of the inclusions showed slight dissolution and cracking. Figure 8As shown in the figure, no sulfide was detected, presumably because no thiourea was added and MnS was decomposed during the electrolysis process.

[0144] Comparative Example 3

[0145] The method for extracting inclusions from a low-carbon low-alloy steel weld provided in this comparative example comprises the following steps:

[0146] (1) Preparation of electrolyte: The electrolyte consists of the following components by weight: 8% acetylacetone, 0.9% tetramethylammonium chloride, 0.4% 8-hydroxyquinoline, 0.5% thiourea, and the balance being analytical grade methanol. The electrolyte preparation process is essentially the same as in Example 1, with only the amounts of the components being adjusted accordingly.

[0147] (2) Same as step (2) of Example 1.

[0148] (3) The electrolysis process was basically the same as in Example 1, except that the electrolysis voltage was 0.25 V (DC regulated power supply, accuracy ±1 mV), the electrolysis current was 0.08 A (constant current mode, fluctuation range ±0.5 mA), the electrolysis temperature was 18° C. (circulating water bath temperature control, fluctuation range ±0.5° C.), and the magnetic stirring speed during the electrolysis process was 150 rpm (high speed leads to increased turbulence in the electrolyte).

[0149] (4) Gradient separation:

[0150] Pretreatment: After electrolysis, the electrolyte was transferred to a 50 mL polytetrafluoroethylene beaker and placed in a 40 kHz ultrasonic cleaner for 10 min (temperature 8 ° C). Then, a permanent magnet (surface magnetic field strength 0.5 T) was attached to the outer wall of the double-layer beaker to adsorb residual iron particles. The adsorption was repeated 3 times. Only 2 mg of iron slag was removed cumulatively, and the electrolyte was turbid, indicating that Fe 2+ Insufficient complexation.

[0151] Coarse filtration: The electrolyte was vacuum filtered (vacuum degree -0.04MPa) using a nylon filter membrane with a pore size of 20μm. The filter was paused after filtering every 100mL of electrolyte and the filter membrane was reversely flushed with 5mL of methanol. However, the nylon filter membrane was severely clogged and the nylon filter membrane with a pore size of 20μm was unable to intercept broken inclusions.

[0152] Centrifugation: The filtrate obtained after coarse filtration was transferred to a 50 mL conical bottom centrifuge tube (70% capacity) and centrifuged at 12000 rpm for 30 min to obtain a large amount of precipitate. SEM showed that the inclusions were partially detached. Figure 9 shown.

[0153] Fine filtration: The precipitate obtained after centrifugation was ultrasonically dispersed in 15 mL of methanol (25 kHz × 2 min), then vacuum filtered through a polypropylene filter membrane with a pore size of 3 μm and rinsed four times with anhydrous ethanol. It was found that there were many black attachments on the surface of the inclusions, making it difficult to extract effective inclusions.

[0154] Detection and Analysis: The polypropylene filter membrane with inclusions obtained in step (4) was fixed to a copper sample stage with conductive glue (silver glue) and gold-sprayed (thickness 5 nm, sputtering current 15 mA, time 60 s). SEM-EDS analysis was then performed (SEM, accelerating voltage 15 kV, working distance 10 mm). SEM showed that the inclusions were irregular in shape and incomplete in morphology, with pits present. Figure 9 shown.

[0155] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for extracting inclusions from low-carbon low-alloy steel welds, characterized in that: The steps include: A low-carbon low-alloy steel weld sample is used as an anode and a cathode is provided to perform electrolysis in an electrolyte; after the electrolysis is completed, ultrasonication is performed to adsorb residual iron particles in the electrolyte; and then coarse filtration, centrifugation, and fine filtration are performed to obtain inclusions; The electrolyte comprises the following components in weight percentage: 10% to 15% of acetylacetone, 0.8% to 1% of tetramethylammonium chloride, 0.3% to 0.5% of 8-hydroxyquinoline, 0.2% to 0.3% of thiourea, and the balance of methanol.

2. The method for extracting inclusions from low-carbon low-alloy steel welds according to claim 1, characterized in that: The low carbon low alloy steel weld sample is ground and ultrasonically cleaned.

3. The method for extracting inclusions from low-carbon low-alloy steel welds according to claim 1, characterized in that: The voltage of the electrolysis is 18-22V, the current of the electrolysis is 0.6-0.7A, and the temperature of the electrolysis is 0-10°C.

4. The method for extracting inclusions from low-carbon low-alloy steel welds according to claim 1, characterized in that: During the electrolysis process, the electrolyte is magnetically stirred at a rotation speed of 50 to 100 rpm, wherein the magnetic particles used for the magnetic stirring adsorb residual iron particles in the electrolyte during the electrolysis process; Preferably, during the magnetic stirring process, when the mass of the residual iron particles adsorbed by the magnetic particles is greater than 5 mg, the magnetic particles are ultrasonically cleaned.

5. The method for extracting inclusions from low-carbon low-alloy steel welds according to claim 1, characterized in that: At least one of the following conditions is met: (1) using a permanent magnet to adsorb the residual iron particles in the electrolyte multiple times; (2) The coarse filtration specifically includes: using an organic nylon filter membrane, a polytetrafluoroethylene filter membrane or a polypropylene filter membrane with a pore size of 20 μm to 30 μm to vacuum filter the electrolyte; (3) The centrifugation specifically comprises: performing the centrifugation on the filtrate obtained after the coarse filtration, wherein the centrifugation speed is 10000-12000 rpm and the centrifugation time is 20-30 min; (4) The fine filtration specifically comprises: ultrasonically dispersing the precipitate obtained after the centrifugation with methanol or ethanol, and then vacuum filtering through a polypropylene filter membrane with a pore size of 0.1 μm to 0.5 μm; (5) The inclusions include Al-Mn-Si-Ti-O(S,N) type inclusions; (6) The cathode includes a platinum electrode, a titanium electrode or a stainless steel electrode.

6. A device, characterized in that The device is used for electrolysis in the method for extracting inclusions from low-carbon low-alloy steel welds as claimed in any one of claims 1 to 5; Wherein, the device comprises an electrolysis container and an anode, a cathode and an electrolyte arranged in the electrolysis container; The anode and the cathode are also connected to a power source.

7. The device according to claim 6, characterized in that The device further comprises a magnetic stirrer disposed below the electrolysis container and a magnet located inside the electrolysis container; Preferably, the magneton comprises a magnetic stirring bar with a coating layer of polytetrafluoroethylene and a magnetic core of neodymium iron boron.

8. The device according to claim 6, characterized in that The electrolysis container includes a double-layer beaker, the double-layer beaker is connected to a constant temperature water tank, and a water circulation pipe of the constant temperature water tank is connected to the interlayer of the double-layer beaker; Furthermore, a sealing cover is provided on the top of the double-layer beaker, and the anode and the cathode pass through the sealing cover.

9. The device according to claim 6, characterized in that The power supply includes a constant current power supply.

10. Use of the method for extracting inclusions from a low-carbon low-alloy steel weld as claimed in any one of claims 1 to 5 or the device as claimed in any one of claims 6 to 9 in preparing welding materials.

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