Method for simultaneously detecting content and size distribution of insoluble zirconium in magnesium-zirconium intermediate alloy and application

Abstract

The invention provides a method for simultaneously detecting the content and size distribution of insoluble zirconium in a magnesium-zirconium intermediate alloy and application, and the method comprises the following steps: sampling the magnesium-zirconium intermediate alloy to be detected, and pretreating to obtain a clean sample; performing magnesium dissolution on the clean sample to obtain zirconium powder precipitate, and performing powder-liquid separation operation on the zirconium powder precipitate to obtain zirconium powder; removing moisture on the surface of the zirconium powder to obtain dry zirconium powder; and weighing the dried zirconium powder, calculating to obtain the content of insoluble zirconium, and measuring the particle size distribution of the zirconium powder as a judgment basis for the particle size distribution of the insoluble zirconium in the intermediate alloy. The method can be used for simultaneously detecting two indexes of the insoluble zirconium content and the insoluble zirconium particle size of the magnesium-zirconium intermediate alloy, and is simple and convenient to operate.

Description

Technical Field

[0001] The present invention belongs to the field of quality inspection of magnesium-zirconium master alloy, and particularly relates to a method and application for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy. Background Art

[0002] Magnesium-zirconium master alloy is an important additive for magnesium alloy casting, with functions such as grain refinement and melt purification, which can significantly improve the service performance of magnesium alloys such as strength, toughness, and creep resistance, and is applied in the preparation of magnesium-based materials in fields such as nuclear power, aerospace, and national defense. Currently, the most commonly used grades of magnesium-zirconium master alloy are Mg-25Zr and Mg-30Zr. Due to the significant differences in density and melting point between magnesium and zirconium (the relative density of magnesium is 1.74 g / cm 3 , melting point 648.8 °C; the relative density of zirconium is 6.49 g / cm³, melting point 1852 °C), and the solubility of zirconium in magnesium is very low (the maximum solubility is about 0.6%, 780 °C), zirconium cannot be uniformly dispersed in magnesium in atomic form by conventional metallurgical methods. The microstructure of magnesium-zirconium master alloy consists of a matrix mainly composed of magnesium and a pure zirconium second phase. Only a small amount of zirconium element is dissolved in the α-Mg matrix, and the vast majority (more than 97%) is insoluble zirconium dispersed in the magnesium matrix in the form of pure zirconium particles.

[0003] The zirconium content is a fundamental indicator of magnesium-zirconium master alloy. It serves as both the basis for determining the grade of magnesium-zirconium master alloy and the calculation basis for the feeding ratio of master alloy during the smelting of magnesium alloys. In actual production, due to the relatively high loss rate when adding zirconium element to magnesium alloys, to compensate for the addition efficiency of zirconium and improve the usage effect, most magnesium-zirconium master alloys on the market are high-concentration products with a zirconium content of 30% or more. However, a higher zirconium content does not necessarily mean a higher quality and grain refinement efficiency of the master alloy. The size distribution of undissolved zirconium particles is also a key factor affecting the usage effect of magnesium-zirconium master alloy. The research "Settling of Undissolved Zirconium Particles in Pure Magnesium Melts" by Qian Ma et al. shows that large-sized undissolved zirconium particles tend to settle rapidly in the magnesium melt (for example, the settling speed of 10 μm zirconium particles in pure magnesium melt is about 17 mm / min), aggregating at the bottom of the ingot and being difficult to fully exert their effectiveness. On the contrary, according to the research "Heterogeneous Nucleation on Potent Spherical Substrates during Solidification" by Qian Ma et al., if the equivalent particle size of undissolved zirconium particles is controlled between 1 - 5 μm, the zirconium particles can significantly reduce the critical nucleation work of the pure magnesium melt, reducing the critical nucleation undercooling to 0.14 - 0.72 °C, and remarkably enhancing the ability of the master alloy to induce nucleation and refine grains. Thus, it can be seen that simultaneously knowing the zirconium content and the size distribution of undissolved zirconium particles is very important for the quality evaluation of magnesium-zirconium master alloy.

[0004] However, there is no definite standard detection method for the above indicators of magnesium-zirconium master alloy. In the current aviation industry standard "HB6773 - 1993 Magnesium-Zirconium Master Alloy Ingot", it is only stated that "the arbitration analysis method for the chemical composition of the alloy ingot shall be agreed upon by both the supply and demand parties", and there is no requirement to detect the distribution of zirconium particles inside the master alloy ingot. In the relevant literature in this field, there are mainly 4 characterization methods for the zirconium content and distribution in magnesium alloys: spectrophotometry, chemical titration, inductively coupled plasma spectroscopy / mass spectrometry (ICP-OES / MS), and scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM&EDS).

[0005] In terms of spectrophotometry, the xylenol orange spectrophotometry and alizarin sulfonate spectrophotometry given in the national standard "GB / T 13748.7-2013 Chemical Analysis Methods for Magnesium and Magnesium Alloys", as well as the quercetin spectrophotometry given in the aviation industry standard "HB 5219.14-1998 Chemical Analysis Methods for Magnesium Alloys" can all be used to measure the zirconium element content in magnesium alloys. However, the above methods are only applicable to the zirconium content detection of magnesium alloys with a zirconium content of less than 1.0%, and cannot be used for the magnesium-zirconium master alloy with a zirconium content generally greater than 20%. In terms of chemical titration method, the "HB 5219.14-1998 Chemical Analysis Methods for Magnesium Alloys" stipulates a chemical titration method with EDTA as the zirconium ion complexing agent, but it is also only applicable to the zirconium content detection of magnesium alloys with a zirconium content of less than 1.0%. According to the report of Liu Rongli's "Determination of Zirconium in Magnesium-Zirconium Alloy", by adjusting the acid solution formula for digesting samples (a mixed system of hydrochloric acid, sulfuric acid, and hydrofluoric acid for digestion), the high-concentration magnesium-zirconium alloy can be fully dissolved, and the applicable range of the EDTA titration method for zirconium content can be broadened to 10-40%. However, in an aqueous solution system containing fluorine, there are various forms of zirconium element. When factors such as temperature, pH value, and F - concentration fluctuate, the Zr 4+ that can be complexed by EDTA is 4· easily converted into ZrF 2 xH 6 2- O, ZrF

[0006] and other forms, resulting in deviation of the titration results. Therefore, this method is relatively sensitive to the system conditions, and the result accuracy highly depends on the operation level of the experimenter. In addition, the chemical titration method has a complex process and low detection efficiency, and it is difficult to meet the needs of industrial production for rapid and convenient detection. ICP-OES / MS is also a commonly used method for determining the zirconium content in magnesium. Qian Ma et al. in the paper "Effect of Soluble and Insoluble Zirconium on the Grain Refinement of Magnesium Alloys" completely dissolved the magnesium-zirconium master alloy with a mixed acid of dilute hydrochloric acid and hydrofluoric acid, and then carried out ICP-OES testing to measure the total zirconium content. Although the theoretical testing accuracy of ICP is very high, since this method requires diluting the concentration of the sample to be tested to the μg / mL level, when the zirconium concentration is very high, the dilution factor needs to be increased synchronously, and the detection error will be significantly amplified. In addition, the sample preparation process of this method is complex and the detection cost is high, and it is also difficult to meet the requirements of industrial production for convenience and timeliness.The above three methods can only measure the zirconium content and cannot measure the size distribution of insoluble zircon particles. The SEM&EDS method is a method that can simultaneously measure the zirconium content and the size distribution of different zircon particles in the magnesium-zirconium master alloy. Its basic principle is to use SEM to observe the morphology of the sample to be tested, take pictures of multiple fields of view, and perform EDS composition detection. The zirconium content data is obtained by statistically analyzing the EDS detection results, and the particle size distribution is obtained by measuring and statistically analyzing the zircon particle sizes in the SEM photos. In patent CN116732369A, the EDS method was used to detect the elements in 20 SEM fields of view of the sample, and the total zirconium content of the master alloy was obtained after statistical averaging. Sun Ming performed image recognition and statistics on the SEM photos of three magnesium-zirconium master alloys with zirconium contents in the range of 25-33%, and obtained a columnar statistical chart of the number density distribution of insoluble zircon particles in the alloy. Although the SEM&EDS method has the advantage of intuitiveness, there are still significant deficiencies: 1) This method is a micro-area analysis and is very susceptible to the randomness of the field of view selection, resulting in insufficient representativeness and stability of the detection results; 2) The accuracy of the EDS method is only about 0.1%, and the composition data is affected by the X-ray interaction volume, resulting in poor accuracy; 3) When the zirconium content of the master alloy is high, insoluble zircon is prone to agglomeration or transformation into irregular shapes, affecting the boundary recognition effect of the image processing software and reducing the statistical accuracy of the size distribution.

[0007] In summary, the zirconium content and the size distribution of insoluble zircon particles are two important indicators for evaluating the quality of magnesium-zirconium master alloys. However, there is currently no method in the field that can simultaneously, simply, and stably measure the indicators in these two dimensions, and the feedback speed of the detection results meets the requirements of actual industrial production. Summary of the Invention

[0008] The purpose of the present invention is to provide a method and application for simultaneously detecting the content and size distribution of insoluble zircon in magnesium-zirconium master alloys, so as to solve the problem that existing detection technologies cannot simultaneously, simply, and stably measure the indicators in two dimensions.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions: A method for simultaneously detecting the content and size distribution of insoluble zircon in magnesium-zirconium master alloys, comprising: After sampling the magnesium-zirconium master alloy to be tested, it is pretreated to obtain a clean sample; The clean sample is dissolved in magnesium to obtain a zircon powder precipitate, and a powder-liquid separation operation is performed on the zircon powder precipitate to obtain zircon powder; The moisture on the surface of the zircon powder is removed to obtain dry zircon powder; The dry zircon powder is weighed and calculated to obtain the content of insoluble zircon, and at the same time, the particle size distribution of the zircon powder is measured as the basis for judging the size distribution of insoluble zircon particles in the master alloy.

[0010] Further, after sampling the magnesium-zirconium master alloy to be measured, pretreatment is carried out to obtain a clean sample, including: Sampling the magnesium-zirconium master alloy, weighing the sample, recording the sample mass and then setting it aside for later use. The sample is in the form of a block or powder. For the block sample, the surface oxide layer is polished off and ultrasonically cleaned with deionized water. For the powder sample, sawdust or drill dust is taken inside the alloy without cleaning.

[0011] Further, the sample mass range is 1 - 5 g. Further, dissolving magnesium in the clean sample to obtain zirconium powder precipitate, including: Using dilute hydrochloric acid to dissolve magnesium. Put the clean sample into deionized water, add dilute hydrochloric acid dropwise, and assist with heating and stirring to completely dissolve the magnesium in the sample. Zirconium precipitates in the form of zirconium powder until no more bubbles are released from the sample.

[0012] Further, the mass fraction range of the dilute hydrochloric acid is 5 - 20%, and the amount of deionized water is less than 10 mL. After the reaction tends to be stable, place the reaction vessel in a water bath and heat it to 40 - 80 °C. Further, performing a powder-liquid separation operation on the zirconium powder precipitate to obtain zirconium powder, including: After weighing the mass of the filter paper, use the suction filtration method to separate the zirconium powder and the solution in the container. Wash the zirconium powder repeatedly with deionized water or absolute ethanol, then place the filter cake obtained by suction filtration in a container and seal it with a breathable membrane material.

[0013] Further, during suction filtration, use a hydrophilic PTFE-PP filter paper for filtration, and the pore size of the filter paper is less than or equal to 0.45 μm.

[0014] Further, removing the moisture on the surface of the zirconium powder to obtain dry zirconium powder, including: Put the zirconium powder container into a freeze dryer. After pre-freezing, evacuate to make the moisture sublimate. After the freeze-drying timing ends, weigh the total weight of the filter paper and the zirconium powder, and then separate the filter cake from the filter paper to obtain dry zirconium powder; during the pre-freezing stage of the freeze dryer, the cold trap temperature is about -70 °C, and the pre-freezing time is 0.5 - 3 hours; during the vacuum drying stage, the vacuum degree ≤ 1 Pa, and dry the sample at room temperature for 12 - 36 hours.

[0015] Further, weighing the dry zirconium powder and calculating to obtain the insoluble zircon content, and at the same time measuring the particle size distribution of the zirconium powder and calculating the insoluble zircon particle size of the master alloy, including: Weigh the mass of the zirconium powder and calculate the insoluble zircon Zr p content of this master alloy according to the following formula;

[0016] Where: is the total weight of the filter paper and the zirconium powder, is the mass of filter paper, is the sample quality; The zirconium powder recovery rate R during separation and collection is calculated as follows:

[0017] in: is the final weight of zirconium powder, is the total weight of filter paper and zirconium powder, is the mass of filter paper; When R is greater than 95%, it is believed that the measured particle size data can better reflect the size distribution of the insoluble zirconium particles in the intermediate alloy, and the particles do not suffer significant losses during the separation and collection process.

[0018] The particle size distribution of zirconium powder is measured by a laser particle size analyzer. When using the laser particle size analyzer for measurement, the zirconium powder is fully mixed, and samples are taken at different locations and depths of the pile with a medicine spoon. Water is used as the medium and surfactants are used to assist dispersion. Before measurement, the suspension is fully mixed and ultrasonically treated for 10 minutes, or a laser particle size analyzer with built-in ultrasonic and stirring equipment in the sample pool is used; the particle size is measured under the condition of a light shielding rate of 10±3.

[0019] The application of the method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy is used for quality rating of magnesium-zirconium master alloy.

[0020] Compared with the prior art, the present invention has the following technical effects: The present invention utilizes insoluble zirconium to approximately estimate the total zirconium content, with a theoretical error within 1%, but the sample preparation method is greatly simplified, and there is no need to use highly toxic substances such as hydrofluoric acid.

[0021] The present invention adopts the weight method to determine the zirconium content, and increases the applicable zirconium content detection range to 10-50%. The detection range of chemical analysis methods in current standards is limited to about 1%. The reason is that the test objects of chemical titration and spectrophotometry are Zr in the digestion solution after magnesium-zirconium alloy is digested with acid. 4+, since the temperature, acidity, etc. of the digestion solution will affect the existence form of zirconium elements, the analysis results are prone to large fluctuations with the system conditions. Directly applying the parameters in the existing methods to samples with high zirconium content may result in situations where zirconium elements cannot be fully complexed and the titration endpoint tails, etc., rendering the method ineffective; both methods require diluting the zirconium content in the test solution to the μg / mL level. For samples with high zirconium content, a higher dilution factor is required after dissolution, resulting in an increase in the magnitude of detection error. However, the present invention adopts the gravimetric method, and the test object is insoluble zircon. The dissolution rate of zircon in dilute hydrochloric acid with a mass fraction of less than 20% and a temperature of 20 - 100 °C is approximately 0.002 mm / y. This value can be ignored compared to the severe corrosion of magnesium by dilute hydrochloric acid and does not fluctuate significantly with system parameters such as the mass ratio of hydrochloric acid to zircon and temperature, ensuring that this method is applicable to master alloys with high zirconium content and providing better result stability. In addition, when weighing the mass of insoluble zircon, the higher the zircon content in the sample, the greater the mass of the insoluble zircon to be measured, and the smaller the relative measurement error caused by the weighing instrument error. Therefore, compared with the current methods, this method can not only include master alloys with high zirconium content in the detection range but also ensure a certain numerical stability, which is a significant progress for the determination of zirconium content in magnesium-zirconium master alloys with high zirconium content.

[0022] The present invention adopts the laser particle size method to sample and conduct macroscopic statistics on the fully mixed zircon powder, effectively avoiding the influence of sampling randomness. Micro-area detection methods such as SEM may lead to result deviations due to sampling limitations, while the laser particle size method ensures the macroscopic representativeness and stability of the detection results.

[0023] Based on the difference in the corrosion resistance of magnesium and zirconium to dilute hydrochloric acid, the present invention can simultaneously measure two core indicators: the insoluble zircon content and the size distribution of magnesium-zirconium master alloys. This is an innovative test scheme that is easy to implement for the rapid quality inspection of master alloys with a zirconium content of 20% or more, filling the technical gap in this area in the industry.

[0024] The detection method of the present invention is easy to operate, the chemical raw materials are easily available, the degree of instrument automation is high, and the particle size detection is rapid. This makes this method particularly suitable for industrial rapid quality inspection and helps to improve the quality of commercially available magnesium-zirconium master alloy products.

[0025] In summary, the technical effects of this technical solution are reflected in multiple aspects, including the expansion of the detection range, the improvement of macroscopic representativeness and stability, the guarantee of accuracy and reliability, the enhancement of safety, the simplification of operation, the reduction of the cost of large-scale detection, and the filling of technical gaps. These technical effects together make the present invention an important innovation in the field of quality inspection of magnesium-zirconium master alloys. Description of the Drawings

[0026] Figure 1The distribution of insoluble zircon particles in the master alloy of Example 1. (a) is its SEM photograph, and (b) is the diameter-number density statistical chart of the insoluble zircon phase in the alloy obtained by the SEM&EDS image recognition and statistical method; Figure 2 The particle size distribution of the zircon powder obtained after dissolving the master alloy of Example 1. (a) is its SEM photograph, and (b) is the diameter-number density statistical chart of the zircon powder obtained by the SEM&EDS image recognition and statistical method; Figure 3 The detection result of the zircon powder obtained after dissolving the master alloy of Example 1 by a laser particle size analyzer (the average value is taken from 5 parallel determinations); Figure 4 The distribution of insoluble zircon particles in the master alloy of Example 2. (a) is its SEM photograph, and (b) is the diameter-number density statistical chart of the insoluble zircon phase in the alloy obtained by the SEM&EDS image recognition and statistical method; Figure 5 The particle size distribution of the zircon powder obtained after dissolving the master alloy of Example 2. (a) is its SEM photograph, and (b) is the diameter-number density statistical chart of the zircon powder obtained by the SEM&EDS image recognition and statistical method; Figure 6 The detection result of the zircon powder obtained after dissolving the master alloy of Example 2 by a laser particle size analyzer (the average value is taken from 5 parallel determinations); Figure 7 The SEM photograph of the insoluble zircon particles in the master alloy of Example 3; Figure 8 The SEM photograph of the zircon powder obtained after dissolving the master alloy of Example 3; Figure 9 The detection result of the zircon powder obtained after dissolving the master alloy of Example 3 by a laser particle size analyzer (the average value is taken from 5 parallel determinations); Figure 10 It is the overall flow chart. Specific embodiments

[0027] The present invention will be further described below with reference to the accompanying drawings: The present invention discloses a method for simultaneously quantitatively detecting the content and size distribution of insoluble zircon in a magnesium-zirconium master alloy. Through a set of detection processes, this method can obtain the content and size distribution information of insoluble zircon in the magnesium-zirconium master alloy, with convenient operation and macroscopically representative detection results.

[0028] Specifically, it includes the following steps: Step 1: Sampling the magnesium-zirconium master alloy. The sample is weighed using an electronic analytical balance, and the sample mass m is recorded 0 for later use; Further, the sample form in Step 1 can be in the form of a block or powder. For the block sample, the surface oxide layer needs to be removed by sanding and ultrasonically cleaned with deionized water for 5 minutes. For the powder sample, sawdust or drill dust can be taken from inside the alloy without cleaning. The sample mass ranges from 1 to 5 g, preferably more than 2 g, aiming to ensure that the sampling area is large enough and the zirconium content and zirconium particle distribution are representative; Step 2: Prepare a dilute hydrochloric acid with a certain mass fraction. Put the sample into deionized water, continuously add the dilute hydrochloric acid drop by drop, assisted by heating and stirring, to gradually dissolve the sample. Eventually, the magnesium in it should be completely dissolved, and zirconium should precipitate in the form of zirconium powder, and no more bubbles should be released from the sample; Further, the mass fraction range of the dilute hydrochloric acid in Step 2 is 5 - 20%, preferably 15%. The amount of deionized water added is less than 10 mL, preferably 5 mL. When the sample just starts to dissolve, the reaction is intense and heating is not required. After the reaction tends to be stable, to reduce the reaction time, the reaction container can be placed in a water bath and heated to 40 - 80°C, preferably 65°C. To ensure complete digestion of magnesium, after the solution no longer emits bubbles, use a glass rod to check whether there are any remaining blocky solids at the bottom of the container, and add about 10 mL of dilute hydrochloric acid in small amounts multiple times. After adding hydrochloric acid each time, stir well and let it stand until no more bubbles are produced in the system; Step 3: Separate the zirconium powder from the solution in the container by suction filtration. First, weigh the mass m of the dry filter paper f , conduct suction filtration, repeatedly wash the zirconium powder with deionized water or absolute ethanol, and then place the filter cake obtained by suction filtration in a container such as a glass watch glass and seal it with a breathable membrane material; Further, use a hydrophilic PTFE - PP filter paper for filtration. The pore size of the filter paper should be less than or equal to 0.45 μm, preferably 0.22 μm, which can ensure that the filtrate is basically clear. The zirconium powder should be washed 3 times with deionized water or absolute ethanol to remove the acidic and corrosive substances attached to the surface and form a firm filter cake. It is also possible to wash the zirconium powder with absolute ethanol. The filter cake after being washed and dried with absolute ethanol is looser in texture, but the adhesion of the zirconium powder to the filter paper increases, which will reduce the powder recovery rate and increase the error of the measurement result; Step 4: Send the zirconium powder container into a freeze dryer, pre - freeze it and then evacuate to sublimate the moisture. After the freeze - drying timing ends, weigh the total weight m of the filter paper and zirconium powder t , and then separate the filter cake from the filter paper to obtain dry zirconium powder; Furthermore, during the pre-freezing stage of the freeze dryer, the cold trap temperature is about -70°C, and the pre-freezing time is 0.5 - 3 hours, preferably 2 hours. During the vacuum drying stage, the vacuum degree is ≤1 Pa, and the sample is dried at room temperature for 12 - 36 hours, preferably 24 hours. To enhance the drying effect, after 6 hours or more of vacuum drying, the filter cake can be separated from the filter paper, crushed, and then continue the vacuum drying treatment. Compared with the conventional vacuum heating drying process, the freeze-drying process has a low material temperature and less contact with the atmospheric environment, which can inhibit the formation of the oxide layer on the surface of zirconium powder, reduce the weight gain caused by zirconium powder oxidation, and avoid the risk of spontaneous combustion of zirconium powder when placed in an environment of 50°C or above.

[0029] Step Five: Weigh the mass m of zirconium powder Zr , and calculate the insoluble zircon (Zr p ) content of the master alloy according to the following formula;

[0030] The insoluble zircon content in commercially available master alloys of magnesium and zirconium is usually greater than 10%. According to the literature, the highest dissolved zircon content in the magnesium-zirconium alloy is about 0.6% (appearing at the peritectic point of 780°C), and it decreases with the decrease of the temperature of the magnesium-zirconium system. Therefore, the dissolved zircon content in master alloys of magnesium and zirconium at room temperature is often lower than 0.6%. For example, Qian Ma et al. measured the highest dissolved zircon content in Mg-1Zr to be 0.48% by ICP method, and Xin Tong et al. measured the highest dissolved zircon content in Mg-30Zr alloy after solution treatment by ultra-high frequency pulsed inert gas arc welding to be 0.57% by ICP method. The vast majority of zircon in master alloys of magnesium and zirconium exists in the form of insoluble zircon. The measured result of the insoluble zircon content by this method is theoretically only about 0.5% lower than the total zircon content. Therefore, in general industrial production, it can be approximately regarded as the total zircon content.

[0031] To ensure that the collection process of zirconium powder does not cause serious errors in quality and particle size distribution, the recovery rate R of zirconium powder during the separation and collection process is calculated according to the following formula, and the recovery rate should be above 95%, more preferably above 97%.

[0032]

[0033] Step Six: Use a laser particle size analyzer to measure the particle size distribution of zirconium powder. There is a corresponding relationship between the particle size distribution of zirconium powder and the particle size of insoluble zircon in the master alloy.

[0034] Furthermore, when using a laser particle size analyzer, the zircon powder should be fully mixed, and samples should be taken at multiple points at different positions and depths of the material pile (at least 4 points) with a spatula. Using water as the medium and surfactants such as 1% sodium dodecyl sulfate to assist in dispersion, the suspension should be fully mixed and ultrasonically treated for 10 minutes before measurement. Alternatively, a laser particle size analyzer with in-built ultrasonic and stirring equipment in the sample cell can be used to reduce the influence of zircon powder agglomeration and sedimentation effects on particle size measurement. For most samples on the market, the scale of insoluble zircon particles is mostly in the range of 1 - 10 μm, and the measurement results have a higher reliability under the condition of a light obscuration rate of 10 ± 3 when measuring particle size.

[0035] Example 1 In this example, the nominal zircon concentration of the sample taken is 35%. The scale of insoluble zircon particles and the statistical histogram of particle diameter - number density under a scanning electron microscope are as Figure 1 shown.

[0036] Cut 3 samples at random positions on the magnesium - zircon master alloy and weigh their masses m 0 , and the sample mass should be above 2 g. Polish the surface with 1000# sandpaper, remove the oxide layer, and then ultrasonically clean for 5 minutes.

[0037] Prepare dilute hydrochloric acid with a mass fraction of 15% in advance. Place the 3 specimens separately in glass beakers, add 5 mL of deionized water to each beaker, and then slowly drip dilute hydrochloric acid into the beakers using a dropper to fully dissolve the magnesium in the alloy. After the reaction tends to be stable, the beakers can be transferred to a 65°C water bath to accelerate dissolution. When no more bubbles emerge from the solution, use a glass rod to check if there are any lumps remaining at the bottom of the container, and add about 10 mL of dilute hydrochloric acid in small portions multiple times. Stir well and let it stand each time after adding hydrochloric acid until no more bubbles are produced in the system. The reason for preferably using 15% dilute hydrochloric acid is that according to the research of Taylor.D. F. et al. in the article "Acid Corrosion Resistance of Tantalum, Columbium, Zirconium, and Titanium", the dissolution rate of zircon in 18% hydrochloric acid at room temperature is about 0.09 mil / y, that is, 0.002 mm / y; Golden. L. B. et al. in "Corrosion Resistance of Titanium, Zirconium, and Stainless Steel" believe that the corrosion rate of zircon in hydrochloric acid with a temperature of 35 - 100°C and a mass fraction of 1 - 20% can be ignored, and no embrittlement or fragmentation of zircon is found during corrosion. 15% dilute hydrochloric acid can not only ensure that insoluble zircon particles are not dissolved but also keep the dissolution rate of magnesium at a relatively high level, shortening the detection time. In this example, about 40 mL of dilute hydrochloric acid is used to dissolve 2.5 g of the specimen, and the dissolution time is about 1 hour.

[0038] Assemble the suction filtration device, take a hydrophilic PTFE-PP filter paper with a pore size of 0.22 μm, and record the mass m of the filter paper. f Then wet it with deionized water and place it on the filter element. Stir the liquid in the beaker thoroughly, and pour it into the filter cup under the guidance of a glass rod. The acidic solution containing magnesium enters the wide-mouth bottle, and the zirconium powder is drawn into a filter cake and remains on the filter paper. Pour about 50 mL of deionized water or absolute ethanol into the filter cup each time, wash the filter cake 3 times to remove the acidic substances attached to its surface, then carefully remove the filter paper from the surface of the filter element, place it in a glass watch glass, seal it with plastic wrap, and pierce several small holes in the film material with a needle for ventilation.

[0039] Place the glass watch glass on the pre-freezing rack and send it into the freeze dryer. Set the temperature in the pre-freezing stage to about -70 °C and the placement time to 2 hours to completely freeze the water in the zirconium powder. After the pre-freezing is completed, quickly take out the watch glass, transfer it to the freeze-drying rack, place it in the vacuum hood, set the vacuum drying stage to room temperature, the vacuum degree to 0.9 Pa, and the placement time to 24 hours to directly sublime the water under extremely low pressure. To enhance the drying effect, after 6 hours of the vacuum drying stage, separate and crush the filter cake and the filter paper, and then continue the vacuum drying treatment. After the program ends, weigh the total weight m of the filter paper and the zirconium powder. t and the mass m of the zirconium powder Zr , transfer the zirconium powder from the filter paper to a sealed container for storage.

[0040] The recovery rate R of zirconium powder during the separation and collection process is calculated according to the following formula. The recovery rate should be above 95%, more preferably above 97%, otherwise the data should be regarded as invalid.

[0041]

[0042] The content of insoluble zirconium (Zr p ) in the master alloy is calculated according to the following formula.

[0043]

[0044] When detecting the particle size, pile up the zirconium powder on the weighing paper, mix it thoroughly with a spatula, take samples at multiple points (at least 4 points) at different positions and depths in the pile, and mix them. Use a laser particle size analyzer with built-in ultrasonic and stirring in the sample cell. Add about 500 mL of deionized water, 1% dishwashing liquid, and the zirconium powder sample to the sample cell in sequence until the light shielding rate reaches within the range of 10 ± 3, more preferably within the range of 10 ± 1, and measure the particle size distribution 5 times in parallel and calculate the average value.

[0045] The dissolution experiment data of the three samples in Example 1 are shown in Table 1. The average value of the insoluble zirconium concentration in this example is 36.80%, the standard deviation is 0.24%, and the RSD is 0.64%.

[0046] Table 1 Test results of insoluble zirconium content in the samples of Example 1

[0047] The SEM photos of the zirconium powder and the particle diameter-number density statistical histogram are shown in Figure 2 .

[0048] The particle size distribution statistics obtained by five-pass parallel laser particle size analysis are shown in Figure 3 .

[0049] It should be noted that the SEM test of zirconium powder in the embodiment is to verify the results of laser particle size analysis, and it is not necessary to perform the test in actual testing. The result obtained by the laser particle size method in this embodiment is larger than the particle size in the SEM photo. The main reason may be that the particle size measured by the laser particle size method is the hydration diameter of the particle. In addition to the particle size of the particle itself, it also includes the solvent layer bound to the surface of the measured particle and other molecules adsorbed by the particle during movement. This value is affected by factors such as particle shape, surface characteristics, and particle agglomeration. The electron microscope directly measures the apparent physical size of the particle, so the particle size distribution measured by the laser method is generally larger than that of the SEM.

[0050] Example 2 The preparation and detection methods of Example 2 are basically the same as those of Example 1, except that: The nominal zirconium concentration of the sample in this example is 50%. The insoluble zirconium particle size and particle diameter-number density statistical histogram under scanning electron microscope is as follows Figure 4 shown.

[0051] The dissolution test data of the three samples of Example 2 are shown in Table 2. The mean value of the insoluble zirconium concentration in this example is 49.48%, the standard deviation is 0.65%, and the RSD is 1.31%.

[0052] Table 2 Test results of insoluble zirconium content of samples in Example 2

[0053] The SEM photos of the zirconium powder and the particle diameter-number density statistical histogram are shown in Figure 5 .

[0054] The particle size distribution statistics obtained by five-pass parallel laser particle size analysis are shown in Figure 6 .

[0055] Example 3 The preparation and detection methods of Example 3 are basically the same as those of Example 1, except that: The nominal zirconium concentration of the sample in this example is 25%. The size of the insoluble zirconium particles under the scanning electron microscope is as follows: Figure 7 As shown, the size of a single particle is about 500 nm-1 μm, but there is severe adhesion between the particles.

[0056] The dissolution experiment data of the three samples in Example 3 are shown in Table 3. The average value of the insoluble zircon concentration in this example is 24.27%, the standard deviation is 0.71%, and the RSD is 2.96%.

[0057] Table 3 Test results of insoluble zircon content in the samples of Example 3

[0058] The SEM photos of the obtained zircon powder are shown in Figure 8 。

[0059] The statistical data of the particle size distribution obtained by five parallel laser particle size methods are shown in Figure 9 。

[0060] It should be noted that, compared with Examples 1 and 2, the phenomenon of adhesion between particles in this example is relatively serious. As shown in Figure 8 , the adhesion between particles cannot be removed by physical methods such as dilution, stirring, and ultrasonic oscillation. Therefore, the measurement results of the laser particle size method are mainly the measurement results of the overall particle clusters similar to those in Figure 8 . However, when observing the zircon powder by SEM, it is found that a small amount of individual particles can be separated from the adhesion, and a small peak appears at about 750 nm in the statistical chart of the Figure 9 laser particle size method, which may reflect this phenomenon. Therefore, laser particle size analysis is not only effective for samples with larger and independent zircon particle sizes such as Examples 1 and 2, but also has reference significance for special samples with smaller zircon particle sizes and adhesion.

[0061] The detection data of the insoluble zircon content in Examples 1, 2, and 3 are compared, and the results are shown in Table 4.

[0062] Table 4 Test results of insoluble zircon content in the examples

[0063] As can be seen from Table 4, the difference between the nominal concentration and the measured concentration in Examples 1, 2, and 3 is within 2%. Considering that this method approximately regards the test result of the insoluble zircon content as the total zircon content, and there is a theoretical difference of about 0.6% between the insoluble zircon content and the total zircon content, this error is basically acceptable in industry. In the three parallel tests, the standard deviation of the measured concentration <1%, and the relative standard deviation RSD < 3%, indicating that the results of this method have high stability, reasonable sampling volume, and are not easily interfered by the uneven zircon distribution problem in commercially available magnesium-zirconium master alloy products.

[0064] The detection data of the insoluble zircon size distribution in Examples 1, 2, and 3 are compared, and the results are shown in Table 5.

[0065] Table 5 Test results of insoluble zircon size distribution in the examples

[0066] As can be seen from Table 5, comparing the SEM test results of the insoluble zircon size distribution between Example 1 and Example 2, the average particle size of the insoluble zircon particles in the alloy of Example 1 is slightly smaller than that of Example 2, and the span (SPAN=(D90-D10) / D50) is also slightly smaller than that of Example 2, that is, the distribution is narrower than that of Example 2.

[0067] SEM detection was carried out on the zircon powder obtained by this method, and it was found that for the same sample, the size of the insoluble zircon particles in the alloy structure was relatively similar to the particle size of the zircon powder. Comparing Figure 1 (b) with Figure 2 (b), Figure 4 (b) with Figure 5 (b), it was found that the trends of the particle size statistical histograms were basically the same. Therefore, selectively dissolving the magnesium matrix with dilute hydrochloric acid basically does not affect the particle size and particle size distribution of the insoluble zircon in the magnesium-zirconium master alloy.

[0068] Laser particle size analysis was carried out on the zircon powder obtained by this method and compared with the SEM detection results of the zircon powder. It was found that under the same test method in different examples, the median diameter D50 and the span in Example 1 in Table 5 were both smaller than those in Example 2. Figure 3 The particle size distribution curve of Figure 6 compared with Figure 2 (b) and Figure 3 , Figure 5 (b) with Figure 6 showed that the abscissa of the peak value was smaller and the width was narrower; under different test methods in the same example, comparing

[0069] In Example 3, due to the too small particle size and serious adhesion, the traditional SEM particle size analysis method failed because the particle boundaries were difficult to be recognized by the image processing software. Therefore, in Table 5, the SEM analysis of insoluble zircon and the SEM analysis of zircon powder could not give the measurement results of quantifiable insoluble zircon size and distribution information. It should be noted that for Example 3, laser particle size analysis could still give the quantitative measurement data of insoluble zircon. Comparing the laser particle size analysis results with those of Examples 1 and 2, it was found that this method successfully reflected the trend that the single particle size of the sample in Example 3 was smaller than that in Examples 1 and 2. Therefore, the detection results of this method for special samples can still be used as a reference for qualitative judgment of the alloy quality.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific implementation manners of the present invention, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy, characterized in that: include: The magnesium-zirconium master alloy to be tested is sampled and pre-treated to obtain a clean sample; Dissolving magnesium in the clean sample to obtain zirconium powder precipitation, and performing powder-liquid separation operation on the zirconium powder precipitation to obtain zirconium powder; removing moisture from the surface of zirconium powder to obtain dry zirconium powder; The insoluble zirconium content is calculated by weighing the dried zirconium powder, and the particle size distribution of the zirconium powder is determined at the same time, which serves as a basis for judging the particle size distribution of the insoluble zirconium in the master alloy.

2. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: The magnesium-zirconium master alloy to be tested is sampled and pre-treated to obtain a clean sample, including: The magnesium-zirconium master alloy is sampled, weighed, and the mass is recorded for later use. The sample is in block or powder form. The block sample is polished to remove the surface oxide layer and ultrasonically cleaned with deionized water. The powder sample is sawdust or drill dust inside the alloy without cleaning.

3. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 2, characterized in that: The sample mass range is 1-5 g.

4. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: The method of dissolving magnesium in the clean sample to obtain zirconium powder precipitation comprises: Use dilute hydrochloric acid to dissolve magnesium. Put the clean sample into deionized water, add dilute hydrochloric acid, and heat and stir to completely dissolve the magnesium in the sample and precipitate zirconium in the form of zirconium powder until the sample no longer releases bubbles.

5. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 4, characterized in that: The mass fraction of dilute hydrochloric acid ranges from 5-20%, and the amount of deionized water is less than 10 mL; after the reaction becomes stable, the reaction vessel is placed in a water bath and heated to 40-80°C.

6. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: The step of performing a powder-liquid separation operation on the zirconium powder precipitate to obtain zirconium powder comprises: After weighing the mass of the filter paper, the zirconium powder in the container is separated from the solution by suction filtration, the zirconium powder is repeatedly washed with deionized water or anhydrous ethanol, and the filter cake obtained by suction filtration is placed in a container and sealed with a breathable membrane material.

7. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 6, characterized in that: During filtration, hydrophilic PTFE-PP filter paper is used for filtration, and the pore size of the filter paper is less than or equal to 0.45 μm.

8. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: The step of removing moisture from the surface of the zirconium powder to obtain dry zirconium powder comprises: The zirconium powder container is sent to a freeze dryer, and after pre-freezing, vacuum is drawn to sublime the water. After the freeze drying time is over, the total weight of the filter paper and the zirconium powder is weighed, and then the filter cake is separated from the filter paper to obtain dry zirconium powder. The cold trap temperature of the freeze dryer in the pre-freezing stage is about -70°C, and the pre-freezing time is 0.5-3 hours. In the vacuum drying stage, the vacuum degree is ≤1 Pa, and the sample is dried at room temperature for 12-36 hours.

9. The method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: The method of weighing the dry zirconium powder to obtain the insoluble zirconium content, measuring the particle size distribution of the zirconium powder, and calculating the particle size of the insoluble zirconium in the master alloy comprises: Weigh the mass of zirconium powder and calculate the insoluble zirconium Zr of the master alloy according to the following formula p content; in: is the total weight of filter paper and zirconium powder, is the mass of filter paper, is the sample quality; The zirconium powder recovery rate R during separation and collection is calculated as follows: R is greater than 95%; in: is the final weight of zirconium powder, is the total weight of filter paper and zirconium powder, is the mass of filter paper; The particle size distribution of zirconium powder is measured by a laser particle size analyzer. When using the laser particle size analyzer for measurement, the zirconium powder is fully mixed, and samples are taken at different locations and depths of the pile with a medicine spoon. Water is used as the medium and surfactants are used to assist dispersion. Before measurement, the suspension is fully mixed and ultrasonically treated for 10 minutes, or a laser particle size analyzer with built-in ultrasonic and stirring equipment in the sample pool is used; the particle size is measured under the condition of a light shielding rate of 10±3.

10. Application of the method for simultaneously detecting the insoluble zirconium content and size distribution of magnesium-zirconium master alloy according to claim 1, characterized in that: Used for quality assessment of magnesium-zirconium master alloy.

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