Preparation method of platinum-rhodium alloy standard substance

Abstract

The invention provides a preparation method of a platinum-rhodium alloy standard substance, which comprises the following steps: S1) proportioning according to the proportion of platinum element and rhodium element in the platinum-rhodium alloy standard substance to obtain a mixed material; s2) the mixed material is subjected to induction heating, and obtained melt is subjected to heat preservation, vacuumizing and cooling at the same time; repeating the steps for at least two times; (S3) induction heating is conducted on the refined material obtained in the step (S2) again, the obtained melt is subjected to heat preservation, vacuumizing is conducted at the same time, atomization powdering is conducted after heat preservation, and platinum-rhodium alloy powder is obtained; s4) drying the platinum-rhodium alloy powder and then sintering the platinum-rhodium alloy powder; (S5) the sintered platinum-rhodium alloy is pressed, and then hot forging is conducted; s6) sequentially carrying out cold rolling and heat treatment on the platinum-rhodium alloy ingot subjected to hot forging, and repeating for multiple times; and (S7) the platinum-rhodium alloy obtained in the step (S6) is subjected to homogenizing heat treatment. According to the preparation method provided by the invention, the platinum-rhodium alloy standard substance with stable and uniform components and low segregation can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of standard samples, and particularly to a method for preparing a platinum-rhodium alloy reference material. Background Art

[0002] Platinum and rhodium both belong to the platinum group of precious metal elements. They are scarce in resources and expensive in price. Due to their unique properties such as high reliability, high stability, irreplaceability, and renewable recyclability, they have become key materials in certain fields. Platinum-rhodium alloys have the advantages of high melting point, strong catalytic activity, stable thermoelectricity, moderate resistivity, strong high-temperature oxidation resistance and corrosion resistance, excellent high-temperature creep rupture strength and anti-creep performance, and are widely used in various high-precision and high-tech fields of modern industry.

[0003] When detecting and analyzing the components of platinum-rhodium alloy raw materials and products, it is necessary to first obtain platinum-rhodium alloy reference materials of various components, and then establish a standard working curve on the corresponding detection and analysis instruments before the incoming materials can be effectively detected and analyzed. Therefore, the stability and homogeneity of the components of platinum-rhodium alloy reference materials are particularly important, otherwise it will affect the authenticity and accuracy of the detection and analysis results. In the process of preparing platinum-rhodium alloy standard samples, ensuring the stability and homogeneity of the components is crucial for obtaining high-quality reference materials.

[0004] Currently, when detecting and analyzing the main components of platinum and rhodium in platinum-rhodium alloy materials, ICP chemical analysis method and X-ray fluorescence detection analysis method are mainly used. If the ICP analysis method is adopted, standard solutions can be directly purchased to establish a standard working curve, while if the X-ray fluorescence analysis is adopted, platinum-rhodium alloy reference materials (fixed standard samples) with different components are required to establish a standard working curve. For platinum-rhodium alloy solid standard samples, due to insufficient market demand (a set of reference materials can be used for a long time), it is difficult to directly purchase in the market, and they are basically self-made by units with detection needs; however, the process methods for preparing platinum-rhodium alloy reference materials by each unit are inconsistent, and the reference materials prepared by the existing conventional process of "vacuum induction melting → casting → forging → rolling → heat treatment" have problems such as unstable composition, poor homogeneity, and segregation of platinum-rhodium alloy. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a method for preparing a platinum-rhodium alloy reference material. The platinum-rhodium alloy reference material prepared by the preparation method provided in the present application has a precise chemical composition and excellent homogeneity.

[0006] In view of this, the present application provides a method for preparing a platinum-rhodium alloy reference material, including the following steps:

[0007] S1) Weigh materials according to the ratio of platinum element and rhodium element in the platinum-rhodium alloy reference material to obtain a mixed material;

[0008] S2) Inductively heat the mixed material, keep the obtained melt at a certain temperature while evacuating to a vacuum, and then cool it; repeat the above steps at least twice;

[0009] S3) Inductively heat the refined material obtained in step S2) again, keep the obtained melt at a certain temperature while evacuating to a vacuum, and then atomize the melt after heat preservation to obtain platinum-rhodium alloy powder;

[0010] S4) Dry and then sinter the platinum-rhodium alloy powder;

[0011] S5) Press the sintered platinum-rhodium alloy and then perform hot forging;

[0012] S6) Perform cold rolling and heat treatment on the platinum-rhodium alloy ingot obtained after hot forging in sequence, and repeat multiple times;

[0013] S7) Perform homogenization heat treatment on the platinum-rhodium alloy obtained in step S6).

[0014] In some specific embodiments, in step S1), when formulating the ingredients, if the raw material rhodium is added in the form of metal rhodium powder, the addition amount of the raw material rhodium is 0.02 - 0.03 wt% higher than the actual composition; if the raw material rhodium is added in the form of platinum-rhodium alloy, the addition amount of the raw material rhodium is 0.005 - 0.006 wt% higher than the actual composition.

[0015] In some specific embodiments, in step S2), the temperature for heat preservation is 50 - 100 °C above the melting point temperature of the melt, and the time for heat preservation is 10 - 20 min; and / or, the vacuum degree for evacuating to a vacuum is below 50 Pa.

[0016] In some specific embodiments, in step S2), stirring is also included during the heat preservation, and the stirring includes inductive heating stirring and mechanical stirring.

[0017] In some specific embodiments, in step S3), the temperature for heat preservation during the re-inductive heating is 50 - 100 °C above the melting point temperature of the melt, the time for heat preservation is 10 - 20 min, and the vacuum degree for evacuating to a vacuum is below 50 Pa.

[0018] In some specific embodiments, in step S3), the atomization for powder making is specifically as follows:

[0019] Raise the temperature of the melt after heat preservation to 150 - 200 °C above the melting point, and at the same time inject high-purity argon gas into the furnace body;

[0020] Start the high-pressure atomization powder making equipment, inject the platinum-rhodium alloy melt into the tundish crucible, and the platinum-rhodium alloy melt enters the atomization channel through the tundish crucible for atomization;

[0021] The atomized atomizing medium is high-purity deionized water, the temperature of the atomizing medium is 0-10°C, the pressure of atomization is 50-100 MPa, and the flow rate of the atomizing medium is 50-150 L / min; the diameter of the leakage hole of the tundish crucible is 3-10 mm; the wall of the atomizing cylinder for atomization is cooled by passing water through a sandwich, and the temperature of the water passing through the sandwich is 0-10°C; the tundish crucible is heated and kept warm by induction stirring using electromagnetic induction.

[0022] In some specific embodiments, in step S4), the sintering specifically is:

[0023] Starting from room temperature, the temperature is raised at a rate of 5°C-10°C / min to 800-900°C, held at 800-900°C for 300 min-400 min, and then the temperature is raised from 800-900°C to 1200-1300°C at a heating rate of 10°C-15°C / min and held for 60 min-80 min; finally, it is cooled with the furnace; during the sintering process, the furnace is evacuated and then filled with argon;

[0024] And / or, in step S5), the pressing includes pre-pressing and re-pressing, the pressure of the pre-pressing is 250-300 MPa, and the pressure of the re-pressing is 450-500 MPa; annealing is also included between the pre-pressing and the re-pressing, the temperature of the annealing is 1000-1200°C, and the time of the annealing is 60-100 min;

[0025] And / or, in step S5), the temperature of the hot forging is 1000-1500°C, and the density of the platinum-rhodium alloy ingot after hot forging is not less than 99.5% of the theoretical density.

[0026] In some specific embodiments, in step S6), the cold rolling deformation amount > 200%, and / or the temperature of the heat treatment is 1300-1400°C, and the time is 40-60 min.

[0027] In some specific embodiments, in step S7), the temperature of the homogenization annealing is 1300-1500°C, and the time is 50-60 h.

[0028] In some specific embodiments, in the platinum-rhodium alloy reference material, the content of rhodium is 1-30 wt%, and the content of platinum is 70-99 wt%.

[0029] The present application provides a method for preparing a platinum-rhodium alloy reference material, which includes, in sequence, batching, induction refining (multiple times), atomization powder making, powder sintering, pressing forming, hot forging, cold rolling / heat treatment (multiple times), and homogenization treatment; during the preparation process of the platinum-rhodium alloy reference material, multiple refinements are initially carried out in the present application, which is beneficial to improving the uniformity of the components. The platinum-rhodium alloy powder is prepared by the rapid cooling method of atomization powder making, and the platinum-rhodium alloy sintered material is prepared by combining the powder sintering process, controlling the component segregation generated during the cooling and solidification process of the platinum-rhodium alloy. Finally, the intragranular segregation is eliminated through the homogenization treatment, significantly improving the accuracy, uniformity, and stability of the components of the platinum-rhodium alloy reference material; further, during the batching process, the addition amount of the raw materials is reasonably controlled according to different forms of raw material addition; during the refining process, the combined action of mechanical stirring and electromagnetic stirring makes the temperature inside the melt more uniform, ensuring the uniform distribution of platinum elements and rhodium elements in the melt, and finally improving the uniformity and stability of the platinum-rhodium alloy reference material.

[0030] The experimental results show that the range of the contents of platinum elements and rhodium elements in the platinum-rhodium alloy reference material prepared by the preparation method provided by the present application is less than 0.015, and the standard deviation is less than 0.007. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the preparation process of the platinum-rhodium alloy reference material of the present invention. Detailed Embodiments

[0032] To further understand the present invention, the preferred implementation embodiments of the present invention will be described below in conjunction with the embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0033] In view of the problems of unstable components, poor uniformity, and segregation of platinum-rhodium alloy in the existing preparation method of platinum-rhodium alloy reference materials, the present application provides a method for preparing a platinum-rhodium alloy reference material. The schematic diagram of the process is as Figure 1 shown. It uses a unique ratio scheme and mixing technology to achieve uniform mixing of platinum and rhodium at the atomic level, and then with the help of a precisely temperature-controlled melting process to ensure the full progress of alloying. Then, through a carefully designed forming process, a platinum-rhodium alloy reference material with precise chemical composition, excellent uniformity, and high stability is created. Specifically, the embodiments of the present application provide a method for preparing a platinum-rhodium alloy reference material, including the following steps:

[0034] S1) Batching according to the proportional relationship between platinum elements and rhodium elements in the platinum-rhodium alloy reference material to obtain a mixed material;

[0035] S2) Inductively heat the mixed material, keep the obtained melt at a certain temperature while evacuating the air, and then cool it; repeat the above steps at least twice;

[0036] S3) Inductively heat the refined material obtained in step S2) again, keep the obtained melt at a certain temperature while evacuating the air, and then atomize the melt after heat preservation to obtain platinum-rhodium alloy powder;

[0037] S4) Dry and then sinter the platinum-rhodium alloy powder;

[0038] S5) Press the sintered platinum-rhodium alloy and then perform hot forging;

[0039] S6) Successively perform cold rolling and heat treatment on the hot-forged platinum-rhodium alloy ingot for multiple times;

[0040] S7) Perform homogenization heat treatment on the platinum-rhodium alloy obtained in step S6).

[0041] In the process of preparing the platinum-rhodium alloy reference material, the present application first prepares a mixed material according to the ratio of platinum and rhodium elements in the platinum-rhodium alloy reference material; during the preparation process, considering the loss of raw rhodium in the subsequent smelting process, if the raw rhodium is added in the form of powder, the nominal addition amount of raw rhodium needs to be 0.02-0.03 wt% higher than the actual composition; if the raw rhodium is added in the form of platinum-rhodium alloy, the nominal addition amount of raw rhodium needs to be 0.005-0.006 wt% higher than the actual composition. For example, when preparing the Pt-10wt%Rh alloy reference material and rhodium is added in powder form, the nominal addition amount should be calculated as 10.02 wt%. Requirements for raw material purity: platinum purity ≥ 99.99 wt%, rhodium purity ≥ 99.99 wt%; the impurity content in pure platinum ingots and rhodium powder raw materials shall comply with the national first-class standards for platinum and rhodium.

[0042] The present application then inductively heats and melts and refines the above-prepared mixed material. The weighed mixed material can be placed in a zirconia crucible in an intermediate-frequency induction furnace and melted and refined by intermediate-frequency induction heating, which is specifically carried out according to the following steps:

[0043] 1) Take a new ZrO2 crucible, soak it in a 13% hydrochloric acid solution, boil it for 20 min - 30 min, and control the solution temperature at 80°C - 100°C; dry / pour the ZrO2 crucible to remove refractory material impurities on the inner wall;

[0044] 2) Place the mixed material in the ZrO2 crucible and inductively heat it to melt the melt; after the material is completely melted, keep the melt temperature 50°C - 100°C above the melting point and hold for 10 min - 20 min; during the heat preservation period, evacuate the air in the furnace body at the same time, and keep the vacuum degree below 50 Pa; after the heat preservation is completed, stop heating and let the melt cool naturally in the crucible;

[0045] 3) After the melt is completely solidified, induction heating is started again to melt the metal. Repeat the above steps twice, that is, "induction heating and melting → vacuum pumping / heat preservation → natural furnace cooling and solidification" is repeated at least twice;

[0046] During the above-mentioned melting and heat preservation period, in addition to being stirred by electromagnetic induction heating itself, the melt is also stirred by a mechanical stirring device to improve the uniformity of the melt composition; the above "induction heating and melting → vacuum pumping / heat preservation → natural furnace cooling and solidification" is repeated to ensure the uniformity of the melt material composition.

[0047] When the above-mentioned refining steps of the mixed material are completed, atomization powder making is carried out. Before atomization powder making, the material after secondary solidification is melted again by induction heating, and "induction heating and melting → vacuum pumping / heat preservation" is repeated, and then the atomization powder making step is carried out. The specific steps are as follows:

[0048] 1) Induction heat the mixed material after the above secondary refining. After melting, the melt temperature is maintained at 50°C to 100°C above the melt melting point; the furnace body is evacuated, and the vacuum degree is maintained below 50 Pa, and heat preservation is carried out for 10 min to 20 min;

[0049] 2) After the above heat preservation time ends, raise the melt temperature to 150°C to 200°C above the melt melting point; at the same time, inject high-purity argon gas into the furnace body to make the pressure in the furnace higher than the atmospheric pressure in order to open the atomization channel valve;

[0050] 3) Start the high-pressure atomization powder making equipment, and inject the refined platinum-rhodium alloy melt into the tundish crucible. The alloy melt flows into the atomization channel through the tundish crucible, and the alloy melt is instantly broken into powder by high-pressure atomized water, and the atomized platinum-rhodium alloy powder material is collected;

[0051] During the atomization powder making process, the atomization medium is high-purity deionized water, the temperature of the atomization medium is 0°C to 10°C, the atomization pressure is 50 MPa to 100 MPa, the flow rate of the atomization medium is 70 L / min to 150 L / min, and the diameter of the tundish crucible leakage hole is 3 mm to 8 mm; the atomization cylinder wall is cooled by passing water through the sandwich, and the temperature of the cold water in the sandwich is 0°C to 10°C; the tundish crucible uses electromagnetic induction to stir, heat and keep warm the melt.

[0052] In the process of atomization powder making in this application, first "induction heating and melting → vacuum pumping / heat preservation" and then atomization powder making. This rapid cooling method can avoid the composition segregation of the platinum-rhodium alloy.

[0053] According to the present invention, the atomized platinum-rhodium alloy powder is then dried and sieved; the drying is carried out in a manner well-known to those skilled in the art, and no special limitation is imposed on this application. In a specific embodiment, the collected powder material can be laid flat in a titanium alloy tray and placed in a drying oven, with a drying temperature of 150°C to 200°C and a drying time of 10h to 15h; the sieving is a sieving means well-known to those skilled in the art. In a specific embodiment, the dried powder can be sieved using a 200-mesh sieve, and the powder below 200 meshes is collected and fed into the next process.

[0054] In this application, the platinum-rhodium alloy powder is then sintered. The sintering is specifically carried out in a vacuum sintering atmosphere. In some specific embodiments, the sintering is to first place the platinum-rhodium alloy box on a mullite refractory brick, and then load the platinum-rhodium alloy powder below 200 meshes into the platinum-rhodium alloy box, and the whole is placed in a vacuum sintering atmosphere furnace for sintering treatment; in some embodiments, the sintering process is specifically as follows: starting from room temperature, the temperature is raised to 800 - 900°C at a rate of 5°C to 10°C / min, held at 800 - 900°C for 300min to 400min, and then the temperature is raised from 800 - 900°C to 1200 - 1300°C at a rate of 10°C to 15°C / min and held for 60min to 80min; finally, it is cooled with the furnace. During the sintering process, after the furnace is evacuated, argon is filled. The staged heating sintering is used to improve the density of the sintered body and reduce the residual gas inside the sintered body.

[0055] If no subsequent forming process is carried out after the above sintering, a solid sheet-like standard sample that meets the requirements cannot be obtained and cannot be used; and subsequent processes such as cold rolling and repeated annealing can further improve the compositional uniformity of the platinum-rhodium alloy reference material. In this application, the sintered platinum-rhodium alloy sintered body is then pressed into shape, and the pressing into shape includes pre-pressing and re-pressing carried out in sequence; in some specific embodiments, the pressure of the pre-pressing is 250MPa to 300MPa, and the pressure of the re-pressing is 450MPa to 500MPa; an annealing treatment is also included between the pre-pressing and the re-pressing to reduce the residual internal stress after the pre-pressing. The annealing temperature of the annealing treatment is 1100°C to 1200°C, and the annealing time is 60min to 100min.

[0056] According to the present invention, the pressed platinum-rhodium alloy ingot is then repeatedly hot forged to further increase the density of the platinum-rhodium alloy ingot and eliminate the internal defects of the platinum-rhodium alloy ingot; in some specific embodiments, the temperature of the hot forging is controlled between 1100°C and 1400°C and repeatedly hot forged; after the hot forging is completed, the density of the platinum-rhodium alloy ingot is tested. The actual density value of the platinum-rhodium alloy ingot is not less than 99.5% of the theoretical density. Only in this way can the density of the platinum-rhodium alloy ingot be ensured. If the density value fails to reach the above value, there will be defects such as pores and cavities inside the platinum-rhodium alloy ingot.

[0057] This application then subjects the pressed platinum-rhodium alloy ingot to cold rolling and heat treatment. The deformation amount of the cold rolling is controlled above 200%. After cold rolling, the sheet is subjected to high-temperature annealing. The annealing temperature is 1300°C to 1350°C, and the annealing time is 40 min to 60 min. After reaching the annealing time, the sheet is quickly taken out and placed in ice water for rapid cooling. Such operations are repeated until the platinum-rhodium alloy sheet is rolled to 1.5 mm to 3.5 mm to ensure that the platinum-rhodium alloy sheet meets the detection requirements and improve the compositional uniformity of the platinum-rhodium alloy. Before cold rolling, in some embodiments, it is preferred to machine the platinum-rhodium alloy ingot after hot forging to remove surface dirt. Specifically, the upper and lower surfaces of the hot-forged ingot are milled to remove surface contamination caused by hot forging, rolling and other processes. The milling depth is 2 mm to 3 mm.

[0058] Finally, this application conducts homogenization treatment. According to the difference in the rhodium content in the platinum-rhodium alloy reference material, a suitable heat treatment process is selected, with a temperature of 1300°C to 1500°C and a time of 50 h to 60 h. When the reference sample reaches the specified holding time, the sample is quickly taken out and placed in cold water at 5°C for rapid cooling.

[0059] In some specific embodiments, according to the requirements of the detection analyzer for the size of the reference sample, a mold of the corresponding size is selected to blank the platinum-rhodium reference material. Generally, a mold with a diameter of 33.5 mm is used to blank the reference sample to obtain a reference material sample with a diameter of 33 mm. At the same time, samples are taken around the mother material of the blanked reference sample material for subsequent ICP detection and analysis to calibrate the platinum and rhodium contents in the reference material.

[0060] After completing the above steps, the preparation of the platinum-rhodium alloy reference material is achieved in this application. The subsequent steps are to conduct compositional detection of the platinum-rhodium alloy reference material, including grinding and polishing - reference sample value determination - establishment of the standard in sequence.

[0061] Among them, the grinding and polishing is specifically as follows: The platinum-rhodium alloy reference material after homogenization heat treatment is pickled. The pickling is to place the reference material in a beaker containing 13% dilute hydrochloric acid, heat it to 80°C and keep it warm for 60 min to eliminate residual impurity elements on the surface of the reference material. After pickling the reference material, the upper and lower surfaces of the reference material are ground and polished with a grinding and polishing machine until a mirror surface is polished.

[0062] The reference sample value determination includes ICP-OES chemical value determination and reference material uniformity detection. Among them, the ICP-OES chemical value determination is specifically as follows:

[0063] According to relevant standards, chemical determination detection and analysis are carried out on samples taken around the standard mother material. Different mother materials for each mass fraction sample are selected, cut into pieces and mixed evenly. A certain mass of sample is weighed, and after high-pressure microwave digestion with aqua regia, it is transferred into a volumetric flask of a certain volume and fixed to volume with deionized water; the platinum-rhodium standard solution and the standard sample solution are tested on an ICP-OES spectrometer to determine the mass concentration of the rhodium element, and then the mass fraction of rhodium is determined according to relevant methods.

[0064] The homogeneity test of the standard substance is specifically as follows:

[0065] The prepared standard material samples are randomly selected and the uniformity of the standard samples of each mass fraction is tested. According to the national standard material uniformity test requirements, the platinum-rhodium alloy standard material is non-destructively tested using an X-ray fluorescence spectrometer.

[0066] Furthermore, the same piece of standard material is subjected to multiple non-destructive tests on different areas using an X-ray fluorescence spectrometer to evaluate the uniformity of the distribution of platinum and rhodium components in the same sample. Based on the above test and analysis results, the prepared platinum-rhodium alloy standard material is calibrated.

[0067] The standard establishment specifically includes: using the prepared standard platinum-rhodium alloy material, testing on an X-ray fluorescence spectrometer, a spark direct reading spectrometer or an electron probe instrument to establish a standard curve.

[0068] The present invention provides a method for preparing a platinum-rhodium alloy standard substance, wherein a platinum-rhodium alloy powder material is prepared by an extremely rapid cooling method, and then a platinum-rhodium alloy standard substance is prepared by a powder metallurgy process, and the component segregation generated by the platinum-rhodium alloy during the cooling and solidification process is controlled, and the intracrystalline segregation is eliminated by homogenization heat treatment, thereby significantly improving the stability and uniformity of the components of the platinum-rhodium alloy standard substance; further, the mechanical stirring and electromagnetic stirring of the platinum-rhodium alloy during the refining process are used to ensure that the platinum and rhodium elements in the original alloy solution are evenly distributed. The present invention provides a method for preparing a platinum-rhodium alloy standard substance, and the main component content range of the prepared standard substance is less than 0.015, and the standard deviation is less than 0.007. Therefore, the present method can be used to prepare a platinum-rhodium alloy standard substance with uniform organizational structure and small component segregation.

[0069] According to the preparation method provided in this application, a platinum-rhodium alloy standard material with stable components, uniform composition and low segregation can be prepared. The standard sample is suitable for use as a standard material for rapid detection analyzers such as X-ray fluorescence spectrometers, spark direct reading spectrometers, and micro-electron probe analyzers, and is used for the establishment and correction of the standard curve of the detection instrument. After the standard curve is established, the platinum-rhodium alloy material can be rapidly detected and analyzed for the main components of platinum and rhodium.

[0070] To further understand the present invention, the following describes in detail the preparation method of the platinum-rhodium alloy reference material provided by the present invention in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0071] Example 1

[0072] 1. Batching

[0073] Prepare a Pt-10wt% Rh alloy reference material: Weigh 6750.00 g of platinum ingots with a purity of 99.99wt% and 751.50 g of rhodium powder with a purity of 99.99wt%. The impurity content in the pure platinum ingots and rhodium powder raw materials shall comply with the national first-class standards for platinum and rhodium.

[0074] 2. Induction refining

[0075] Place the weighed materials in a ZrO2 crucible of an intermediate-frequency induction furnace for induction heating, melting, and refining. The operation steps are as follows:

[0076] 1) Take a new ZrO2 crucible and soak it in a hydrochloric acid solution with a concentration of 13% and a temperature of 85°C for 30 minutes.

[0077] 2) Dry and pour the ZrO2 crucible to remove the refractory impurities on the inner wall of the crucible.

[0078] 3) Place the weighed platinum and rhodium powder in the ZrO2 crucible, and inductively heat and melt the pure platinum ingots and rhodium powder. After the materials are melted, keep them at 1960°C (the melting point of the Pt-10wt% Rh alloy is 1860°C) for 20 minutes. During the heat preservation period, evacuate the furnace body at the same time, and maintain the vacuum degree at 5 Pa. Stop heating and let the melt cool naturally.

[0079] 4) When the melt is completely solidified, start inductively heating and melting the metal again, and repeat the above steps twice, that is, "inductive heating and melting → vacuum pumping / heat preservation → natural furnace cooling and solidification" for two times.

[0080] 5) During the melting and heat preservation period, in addition to being stirred by electromagnetic induction, the melt is also stirred by a mechanical stirring device to improve the uniformity of the melt composition.

[0081] 3. Atomization powder making

[0082] When the materials complete the above refining steps, inductively heat and melt the solidified materials again, evacuate the air and fill with argon to prepare Pt-10wt% Rh alloy powder. The specific steps are as follows:

[0083] 1) Inductively heat the materials refined twice as described above again. After melting, keep the temperature of the melt at 1960°C, evacuate the furnace body, the vacuum degree is 5 Pa, keep warm for 20 minutes, and mechanically stir the melt during the heat preservation period.

[0084] 2) After the heat preservation time ends, raise the melt temperature to 2060 °C; meanwhile, inject high-purity argon gas into the furnace body to make the pressure in the furnace higher than the atmospheric pressure in order to open the atomization channel valve;

[0085] 3) Start the high-pressure atomization powder-making equipment, and inject the refined Pt-10wt% Rh alloy melt into the tundish crucible. The alloy melt flows into the atomization channel through the tundish crucible, and the high-pressure atomized water is used to instantly break the alloy melt into powders;

[0086] High-pressure water atomization powder-making process parameters: The atomization medium is high-purity deionized water; the temperature of the atomization medium is 5 °C; the flow rate of the atomization medium is 100 L / min; the water pressure is 90 MPa; the leakage hole of the tundish crucible is 5 mm; the inner wall of the atomization cylinder is provided with a sandwich layer for water cooling, and the temperature of the cooling water is 5 °C; the tundish crucible uses electromagnetic induction to perform induction stirring heating and heat preservation on the melt;

[0087] 4) Collect the atomized powder-making platinum-rhodium alloy powder material;

[0088] 4. Dry and screen the powder

[0089] Lay the powder material collected in step 3 flat on a titanium alloy tray and place it in a drying oven. The drying temperature is 150 °C and the drying time is 15 h;

[0090] Screen the dried powder with a 200-mesh sieve, and collect the powder below 200 mesh to enter the next process;

[0091] 5. Powder sintering

[0092] First, place the platinum-rhodium alloy box on the mullite refractory brick, then load the Pt-10wt% Rh powder below 200 mesh into the platinum-rhodium alloy box, and place the whole in a vacuum sintering atmosphere furnace for sintering treatment; Sintering process: Start from room temperature and heat up to 800 °C at a rate of 10 °C / min, hold at 800 °C for 400 min, then heat up from 800 °C to 1200 °C at a heating rate of 15 °C / min, and hold for 80 min; Finally, cool with the furnace; During the sintering process, evacuate the furnace and then fill it with argon;

[0093] 6. Compression molding

[0094] Place the sintered Pt-10wt% Rh alloy sintered pellets in the inner cavity of the mold, and perform pre-pressing and re-pressing on it: The pre-pressing pressure is 300 MPa. After pressing, place the formed body in an annealing furnace and anneal it at 1200 °C. After holding for 80 min, perform secondary re-pressing on the annealed ingot, and the re-pressing pressure is 500 MPa;

[0095] 7. Hot forging

[0096] The Pt-10wt% Rh alloy ingot after pressing is repeatedly hot forged to further increase the density of the ingot and eliminate internal defects; the hot forging temperature is controlled between 1100 °C and 1400 °C, and hot forging is repeated; after hot forging, the density of the ingot is tested to be 19.91 g / cm 3 ;

[0097] 8. Repeated cold rolling - heat treatment

[0098] The upper and lower surfaces of the hot forged ingot are milled to remove surface contamination caused by hot forging, rolling and other processes, and the milling depth is 2.5 mm; then cold rolling is started, and the rolling deformation is 250%; after cold rolling, the sheet is annealed at a high temperature, the annealing temperature is 1350 °C, and the annealing time is 60 min; after the annealing time is reached, the sheet is quickly taken out and placed in ice water for rapid cooling; such operations are repeated until the alloy sheet is rolled to 2 mm;

[0099] 9. Punching and shearing specimens

[0100] According to the requirements of the detection analyzer for the size of the specimen, a die of the corresponding size is selected to punch and cut the specimen; a die with a diameter of 33.5 mm is used to punch and cut the specimen to obtain a standard Pt-10wt% Rh substance sample with a diameter of 33 mm;

[0101] At the same time, samples are taken around the mother material of the punched and sheared specimen for ICP detection and analysis to calibrate the platinum and rhodium contents in the reference material;

[0102] 10. Homogenization heat treatment

[0103] The punched reference material is placed in a platinum-rhodium alloy annealing pan and homogenized and annealed in a vacuum atmosphere furnace; the homogenization annealing temperature is 1400 °C, and the holding time is 50 h. When the specified holding time is reached, the sample is quickly taken out and placed in cold water at 5 °C for rapid cooling;

[0104] 11. Grinding and polishing the specimen

[0105] The platinum-rhodium alloy reference material after homogenization heat treatment is pickled. The reference material is placed in a beaker containing 13% dilute hydrochloric acid and heated to 80 °C and held for 60 min to eliminate the base metal elements on the surface of the reference material;

[0106] After pickling the reference material, the upper and lower surfaces of the reference material are ground and polished with a grinding and polishing machine until a mirror surface is polished;

[0107] 12. Value determination of the specimen

[0108] 1) Chemical value determination by ICP-OES

[0109] According to relevant standards, the samples taken around the standard parent material are tested and analyzed for chemical value: the parent materials with different mass fractions are selected, cut into pieces and mixed evenly, a certain mass of samples are weighed, digested with aqua regia high-pressure microwave, transferred into a volumetric flask of a certain volume, fixed to volume with deionized water, and the platinum-rhodium standard solution and the standard sample solution are tested on an ICP-OES spectrometer to determine the mass concentration of the rhodium element, and then the mass fraction of rhodium is determined according to relevant methods;

[0110] 2) Homogeneity test of standard materials

[0111] Randomly select the prepared standard material samples, conduct uniformity test on the standard samples of each mass fraction, and use X-ray fluorescence spectrometer to conduct non-destructive test on platinum-rhodium alloy standard materials in accordance with the national standard material uniformity test requirements;

[0112] Furthermore, the same piece of standard material was non-destructively tested in the area using an X-ray fluorescence spectrometer to evaluate the uniformity of the distribution of platinum and rhodium in the same sample; the results are shown in Table 1;

[0113] According to the aforementioned test and analysis results, the prepared platinum-rhodium alloy standard material is valuated;

[0114] 13. Standardization

[0115] Use standard samples to test and establish a fair curve on an X-ray fluorescence spectrometer or electron probe, determine appropriate test parameters, and thus determine that the porcelain sleeve standard can be used as a marking material for establishing a fair curve for non-destructive testing.

[0116] Example 2

[0117] 1. Ingredients

[0118] Preparation of Pt-5wt% Rh alloy standard material: weigh 7600.00g of platinum ingot with a purity of 99.99wt% and 401.60g of rhodium powder with a purity of 99.99wt%. The impurity content in the pure platinum ingot and rhodium powder raw materials shall be in accordance with the national first-level standard for platinum and rhodium;

[0119] 2. Induction refining

[0120] Place the weighed material in a ZrO2 crucible of a medium frequency induction furnace for induction heating, melting and refining. The operation steps are as follows:

[0121] 1) Take a new ZrO2 crucible and immerse it in a 13% hydrochloric acid solution at 90°C for 20 minutes;

[0122] 2) Drying and pouring the ZrO2 crucible to remove impurities from the refractory material on the inner wall of the crucible;

[0123] 3) Place the weighed pure platinum ingot and rhodium powder in a ZrO2 crucible, and melt the platinum and rhodium powder by induction heating; after the materials are melted, keep them at 1880 °C (the melting point of Pt-5wt% Rh alloy is 1826 °C) for heat preservation for 20 min; during the heat preservation period, evacuate the furnace body at the same time, and maintain the vacuum degree at 5 Pa; stop heating and let the melt cool naturally;

[0124] 4) When the melt is completely solidified, start induction heating and melting the metal again, and repeat the above steps twice, that is, "induction heating and melting → evacuation / heat preservation → natural furnace cooling and solidification" are carried out twice;

[0125] 5) During the melting and heat preservation period, in addition to being stirred by electromagnetic induction, the melt is also stirred by a mechanical stirring device to improve the uniformity of the melt composition;

[0126] 3. Atomization powder making

[0127] After the materials complete the above refining steps, induction heating and melting the solidified materials again, evacuate and fill with argon to prepare Pt-5wt% Rh alloy powder. The specific steps are as follows:

[0128] 1) Induction heat the above-mentioned secondary refined materials again. After melting, keep the melt temperature at 1800 °C, evacuate the furnace body, the vacuum degree is 10 Pa, keep it warm for 30 min, and mechanically stir the melt during the heat preservation period;

[0129] 2) After the heat preservation time ends, raise the melt temperature to 2000 °C; at the same time, inject high-purity argon into the furnace body to make the pressure in the furnace higher than the atmospheric pressure in order to open the atomization channel valve;

[0130] 3) Start the high-pressure atomization powder making equipment, and inject the refined Pt-5wt% Rh alloy melt into the tundish crucible. The alloy melt flows into the atomization channel through the tundish crucible, and the alloy melt is instantly broken into powder by high-pressure atomized water;

[0131] High-pressure water atomization powder making process parameters: the atomization medium is high-purity deionized water; the atomization medium temperature is 5 °C; the atomization medium flow rate is 70 L / min; the water pressure is 100 MPa; the tundish crucible leakage hole is 4 mm; the inner wall of the atomization cylinder is cooled by water through a sandwich, and the cooling water temperature is 5 °C; the tundish crucible uses electromagnetic induction to stir, heat and keep warm the melt;

[0132] 4) Collect the atomized powder platinum-rhodium alloy powder material;

[0133] 4. Drying and screening the powder

[0134] Lay the powder material collected in step 3 flat on a titanium alloy tray and place it in a drying oven. The drying temperature is 200 °C and the drying time is 10 h;

[0135] Screen the dried powder through a 200-mesh sieve, and collect the powder below 200 mesh for the next process;

[0136] 5. Powder sintering

[0137] First, place the platinum-rhodium alloy box on the refractory brick, then load the Pt-5wt%Rh powder below 200 mesh into the platinum-rhodium alloy box, and place the whole in a vacuum sintering atmosphere furnace for sintering treatment; Sintering process: Start heating from room temperature at a rate of 7°C / min to 800°C, hold at 800°C for 350 min, then heat from 800°C to 1200°C at a heating rate of 10°C / min, and hold for 60 min; Finally, cool with the furnace; During the sintering process, evacuate the furnace and then fill it with argon;

[0138] 6. Compression molding

[0139] Place the sintered Pt-5wt%Rh alloy sintered pellets in the inner cavity of the mold, and perform pre-pressing and re-pressing on it: The pre-pressing pressure is 280 MPa. After pressing, place the formed body in an annealing furnace for annealing treatment at 1150°C. After holding for 70 min, perform secondary re-pressing on the annealed ingot, and the re-pressing pressure is 480 MPa;

[0140] 7. Hot forging

[0141] Perform repeated hot forging on the Pt-5wt%Rh alloy ingot after compression molding to further increase the density of the ingot and eliminate internal defects of the ingot; Control the hot forging temperature between 1100°C and 1400°C and perform repeated hot forging; After hot forging, test the density of the ingot to be 20.35 g / cm 3 ;

[0142] 8. Repeated cold rolling - heat treatment

[0143] Milling the upper and lower surfaces of the hot-forged ingot to remove surface contamination caused by hot forging, rolling and other processes, and the milling depth is 1.5 mm; Then start cold rolling, and the rolling deformation is 300%; After cold rolling, perform high-temperature annealing on the sheet, the annealing temperature is 1300°C, and the annealing time is 40 min; After reaching the annealing time, quickly take out the sheet and place it in ice water for rapid cooling; Repeat the operation until the alloy sheet is rolled to 2 mm;

[0144] 9. Punch and shear the standard sample

[0145] According to the requirements of the detection analyzer for the size of the standard sample, select a mold of the corresponding size to punch and shear the standard sample; Select a mold with a diameter of 33.5 mm to punch and shear the standard sample to obtain a Pt-5wt%Rh standard substance sample with a diameter of 33 mm;

[0146] Meanwhile, samples are taken around the mother material of the punched and sheared standard sample for ICP detection and analysis to calibrate the platinum and rhodium contents in the reference material;

[0147] 10. Homogenization heat treatment

[0148] The punched reference material is placed in a platinum-rhodium alloy annealing pan and subjected to homogenization annealing treatment in a vacuum atmosphere furnace; the homogenization annealing temperature is 1350 °C, and the holding time is 55 h. When the specified holding time is reached, the sample is quickly taken out and placed in cold water at 5 °C for rapid cooling;

[0149] 11. Grinding and polishing the standard sample

[0150] The platinum-rhodium alloy reference material after homogenization heat treatment is pickled. The reference material is placed in a beaker containing 13% dilute hydrochloric acid, heated to 80 °C and held for 60 min to remove the base metal elements on the surface of the reference material;

[0151] After pickling the reference material, the upper and lower surfaces of the reference material are ground and polished with a grinding and polishing machine until a mirror surface is polished;

[0152] 12. Value determination of the standard sample

[0153] 1) Chemical value determination by ICP-OES

[0154] Chemical value determination and detection analysis are carried out on the samples taken around the mother material of the standard sample according to relevant standards: different mother materials of each mass fraction sample piece are selected, cut and mixed evenly, a certain mass of the sample is weighed, digested by high-pressure microwave with aqua regia, transferred into a volumetric flask of a certain volume, made up to the mark with deionized water, and the platinum-rhodium standard solution and the standard sample solution are tested on an ICP-OES spectrometer to determine the mass concentration of rhodium element, and then the mass fraction of rhodium is determined according to relevant methods;

[0155] 2) Homogeneity detection of the reference material

[0156] Randomly select the prepared reference material sample pieces, and conduct homogeneity tests on the standard sample pieces of each mass fraction. According to the requirements of the national standard for homogeneity inspection of reference materials, the platinum-rhodium alloy reference material is tested nondestructively using an X-ray fluorescence energy spectrometer:

[0157] Furthermore, the same reference material sample piece is tested nondestructively in the area using an X-ray fluorescence energy spectrometer to evaluate the homogeneity of the distribution of platinum and rhodium in the same sample piece; the results are shown in Table 1;

[0158] According to the above test and analysis results, the prepared platinum-rhodium alloy reference material is value-determined;

[0159] 13. Establishing the standard

[0160] Use the reference sample to test on the X-ray fluorescence spectrometer or electron probe to establish a calibration curve, determine appropriate test parameters, and thus determine that the porcelain sleeve reference sample can be used as a reference substance for establishing a calibration curve in non-destructive testing.

[0161] Comparative Example 1

[0162] The preparation method of the conventional platinum-rhodium alloy reference substance is as follows:

[0163] 1) Vacuum induction refining: Mix platinum and rhodium powder that meet the purity requirements according to the Pt-10wt%Rh alloy, then place the materials in a ZrO2 crucible, and melt and refine the platinum-rhodium alloy by vacuum induction heating according to the conventional melting process.

[0164] 2) Pouring / Hot forging: After the metal melts, keep it warm for a period of time, pour the melt into a water-cooled copper mold; then heat the ingot and perform hot forging.

[0165] 3) Plate rolling: Perform surface milling on the hot-forged metal, and then perform the "cold rolling - annealing - cold rolling - annealing" treatment, and finally roll the plate into a 2-mm-thick plate.

[0166] 4) Punching the reference sample: Select a suitable mold to punch the reference sample.

[0167] 5) Value determination of the reference sample: Perform ICP-OES and X-ray fluorescence spectroscopy on the prepared reference sample to detect and calibrate the rhodium and platinum contents in the sample. The results are shown in Table 1.

[0168] Table 1 Data table of ICP-OES test results of platinum-rhodium reference samples prepared in the examples and comparative examples

[0169]

[0170]

[0171] Table 1 Data table of ICP-OES test results of platinum-rhodium reference samples prepared in the examples and comparative examples (continued table 1)

[0172]

[0173]

[0174] As can be seen from Table 1, the contents of Pt element and Rh element in the platinum-rhodium reference sample prepared in Example 1 are both highly close to the contents of Pt element and Rh element in the PtRh 10 substance. The contents of Pt element and Rh element in the platinum-rhodium reference sample prepared in Example 2 are both highly close to the contents of Pt element and Rh element in the PtRh5 substance, and both the standard deviation and the range are low; compared with Comparative Example 1, for PtRh 10Preparation of standard sample. The average values of Pt element and Rh element in the standard sample prepared in Example 1 are closer to those of PtRh 10 in terms of the content of substances. Therefore, the standard deviation and range are also excellent. At the same time, by detecting the contents of Pt element and Rh element at each point of the platinum-rhodium standard samples prepared in Example 1 and Example 2, the experimental results show that the uniformity of Pt element and Rh element at each point of the platinum-rhodium standard samples prepared in Example 1 and Example 2 is high, and no segregation problem occurs. Compared with Comparative Example 1, the uniformity of the platinum-rhodium standard sample prepared in Example 1 is also more excellent. Therefore, the preparation method of the platinum-rhodium alloy substance provided in this application can control the contents of Pt element and Rh element more accurately and has better uniformity.

[0175] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0176] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a platinum-rhodium alloy reference material, comprising the following steps: S1) According to the ratio of platinum element and rhodium element in the platinum-rhodium alloy reference material, charge materials to obtain a mixed material; S2) Inductively heat the mixed material, keep the obtained melt at a certain temperature while evacuating to vacuum, and then cool it; Repeat the above steps at least twice; S3) Inductively heat the refined material obtained in step S2) again, keep the obtained melt at a certain temperature while evacuating to vacuum, and after insulation, perform atomization to produce powder to obtain platinum-rhodium alloy powder; S4) Dry the platinum-rhodium alloy powder and then sinter it; S5) Press the sintered platinum-rhodium alloy and then perform hot forging; S6) Successively perform cold rolling and heat treatment on the hot-forged platinum-rhodium alloy ingot for multiple times; S7) Perform homogenization heat treatment on the platinum-rhodium alloy obtained in step S6).

2. The preparation method according to claim 1, wherein, In step S1), when charging materials, if the raw material rhodium is added in the form of metallic rhodium powder, the addition amount of the raw material rhodium is 0.02 - 0.03 wt% higher than the actual composition; if the raw material rhodium is added in the form of platinum-rhodium alloy, the addition amount of the raw material rhodium is 0.005 - 0.006 wt% higher than the actual composition.

3. The preparation method according to claim 1, characterized in that, In step S2), the temperature for insulation is 50 - 100 °C above the melting point temperature of the melt, and the time for insulation is 10 - 20 min; and / or, the vacuum degree for evacuating to vacuum is below 50 Pa.

4. The preparation method according to claim 3, characterized in that, In step S2), stirring is also included during the insulation, and the stirring includes inductive heating stirring and mechanical stirring.

5. The preparation method according to claim 1, characterized in that, In step S3), the temperature for insulation during the re-inductive heating is 50 - 100 °C above the melting point temperature of the melt, the time for insulation is 10 - 20 min, and the vacuum degree for evacuating to vacuum is below 50 Pa.

6. The preparation method according to claim 5, characterized in that, In step S3), the atomization to produce powder is specifically as follows: Raise the temperature of the melt after insulation to 150 - 200 °C above the melting point, and at the same time inject high-purity argon gas into the furnace body; Start the high-pressure atomization powder production equipment, inject the platinum-rhodium alloy melt into the tundish crucible, and the platinum-rhodium alloy melt enters the atomization channel through the tundish crucible for atomization; The atomization medium for atomization is high-purity deionized water, the temperature of the atomization medium is 0 - 10 °C, the pressure for atomization is 50 - 100 MPa, and the flow rate of the atomization medium is 50 - 150 L / min; the diameter of the leakage hole of the tundish crucible is 3 - 10 mm; the atomization cylinder wall for atomization is cooled by passing water through the sandwich layer, and the temperature of the water passing through the sandwich layer is 0 - 10 °C; the tundish crucible is inductively stirred and heated and insulated by electromagnetic induction.

7. The preparation method according to claim 6, characterized in that, In step S4), the sintering is specifically as follows: Start heating from room temperature at a rate of 5 °C - 10 °C / min to 800 - 900 °C, keep the temperature at 800 - 900 °C for 300 min - 400 min, and then heat from 800 - 900 °C to 1200 - 1300 °C at a heating rate of 10 °C - 15 °C / min and keep the temperature for 60 min - 80 min; finally, cool with the furnace; during the sintering process, evacuate the furnace and then fill it with argon; And / or, in step S5), the pressing includes pre-pressing and re-pressing. The pressure of the pre-pressing is 250 - 300 MPa, and the pressure of the re-pressing is 450 - 500 MPa; annealing is also included between the pre-pressing and the re-pressing. The temperature of the annealing is 1000 - 1200 °C, and the time of the annealing is 60 - 100 min; And / or, in step S5), the temperature of the hot forging is 1000 - 1500 °C, and the density of the platinum-rhodium alloy ingot after hot forging is not less than 99.5% of the theoretical density.

8. The preparation method according to claim 7, wherein, In step S6), the deformation amount of the cold rolling > 200%, and / or, the temperature of the heat treatment is 1300 - 1400 °C, and the time is 40 - 60 min.

9. The preparation method according to claim 7, characterized in that, In step S7), the temperature of the homogenization annealing is 1300 - 1500 °C, and the time is 50 - 60 h.

10. The preparation method according to any one of claims 1 to 9, characterized in that, In the platinum-rhodium alloy reference material, the content of rhodium is 1 - 30 wt%, and the content of platinum is 70 - 99 wt%.

Images