A method for detecting the primary crystallization temperature of a refining agent
By simultaneously acquiring thermocouple temperature signals and visually observing changes in the melt state, the accuracy and equipment dependence issues of primary crystallization temperature measurement of refining agents were resolved, enabling efficient and reliable measurement under different environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BAOTOU ALUMINUM CO LTD
- Filing Date
- 2026-05-26
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies for determining the primary crystallization temperature of refining agents have several drawbacks. High-precision methods are costly, complex to operate, and require expensive equipment, while low-precision methods rely on subjective experience and have poor repeatability, making it difficult to measure quickly and accurately on the production site.
A method of simultaneous acquisition and fusion of thermal and visual signals was adopted. By continuously acquiring the temperature-time signal output by thermocouples during the cooling process and combining it with visual observation of the melt state changes, a cooling curve was plotted, and the average value of the two signals was taken to determine the initial crystallization temperature.
It improves the objectivity and accuracy of measurements, reduces reliance on expensive equipment, is suitable for laboratories and production sites at different levels, and meets the needs for rapid feedback and quality control.
Smart Images
Figure CN122448899A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aluminum or aluminum alloy refining technology, and specifically relates to a method for detecting the primary crystallization temperature of a refining agent. Background Technology
[0002] Refining fluxes are white powdery, granular, or compressed fluxes prepared from various dried inorganic salts in a specific ratio. They are primarily used in the smelting of aluminum alloys and pure aluminum to remove hydrogen and floating oxide inclusions from the molten aluminum. The primary crystallization temperature of the refining flux is one of its core thermophysical parameters, directly determining its operating temperature window, refining efficiency, and process stability in the smelting of aluminum or aluminum alloys and other non-ferrous metals. Accurately determining the primary crystallization temperature of the refining flux is crucial for optimizing the refining process, ensuring melt quality, and preventing premature solidification or excessive volatilization of the flux.
[0003] Currently, the industry relies on two main measurement approaches, both of which have certain limitations. On the one hand, differential scanning calorimetry (DSC), a precision instrument method based on thermal analysis, while theoretically highly accurate, is expensive to purchase and maintain, and requires stringent laboratory conditions and highly skilled operators. Furthermore, DSC requires extremely small sample sizes, potentially leading to a lack of representativeness for samples of non-uniformly composed refining agents, and its relatively long testing cycle makes it difficult to meet the needs of rapid feedback in production settings. On the other hand, while the traditional cooling curve method is simple to operate and uses convenient equipment, its principle relies on recording the inflection point of the temperature-time curve caused by the release of latent heat of phase change during sample solidification. However, refining agents, as multi-component molten salt systems, typically have low latent heat of solidification, resulting in very broad and indistinct inflection points on the cooling curve. This makes repeatability and accuracy difficult to guarantee, failing to meet the precision requirements of quality control and formulation development.
[0004] Current technologies essentially present a dilemma: either choose high-precision but costly and complex laboratory instrumentation methods, or opt for low-cost but low-precision methods that heavily rely on subjective experience. Especially in production environments, small and medium-sized laboratories, or R&D scenarios requiring rapid screening, there is an urgent need for a measurement method that balances measurement accuracy, ease of operation, and equipment versatility. This method should be able to provide objective, reliable, and repeatable primary crystallization temperature data without excessive reliance on expensive, precision instruments, thus filling the gap in practicality, economy, and reliability in current technologies. Summary of the Invention
[0005] In view of this, the purpose of this invention is to provide a method for detecting the primary crystallization temperature of a refining agent. The method for detecting the primary crystallization temperature of a refining agent provided by this invention does not rely on a precision instrument—differential scanning calorimeter—and yields accurate and reliable results.
[0006] This invention provides a method for detecting the primary crystallization temperature of a refining agent, comprising the following steps: After grinding the sample of the refining agent to be tested, it is placed in a transparent container, and the temperature measuring end of the thermocouple is inserted into the sample. A transparent container containing the sample is placed in a heating device and heated until the sample forms a homogeneous melt. Then, the sample is cooled down. During the cooling process, the temperature-time signal output by the thermocouple is continuously acquired, and the state changes of the melt are observed. A cooling curve is plotted based on the temperature-time signal. The inflection point temperature at which the cooling curve first deviates from the linear cooling trend is recorded as the first temperature. The temperature at which the melt first appears turbid or solid particles is recorded as the second temperature. The average of the first and second temperatures is taken to obtain the primary crystallization temperature of the refining agent sample to be tested.
[0007] Preferably, the cooling rate is no higher than 0.5℃ / s.
[0008] Preferably, the cooling rate is 0.3~0.5℃ / s.
[0009] Preferably, the heating rate is 0.3~1℃ / s.
[0010] Preferably, the heating process until the sample forms a homogeneous melt includes: heating until the sample melts, then continuing to heat to 700~800℃ and holding at that temperature for 5~15 minutes.
[0011] Preferably, the grinding time is 15-30 seconds and the rotation speed is 1000-1100 rpm.
[0012] Preferably, the filling height of the sample in the transparent container is not less than 20 mm.
[0013] Preferably, the light-transmitting container is a sapphire tube or a high-temperature resistant glass tube.
[0014] Preferably, the observation of the state changes of the melt is performed using a high-speed camera or a microscopic imaging system.
[0015] Preferably, the refining agent sample to be tested is a refining agent for smelting aluminum or aluminum alloys, and the refining agent for smelting aluminum or aluminum alloys includes one or more of sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, magnesium fluoride, calcium chloride, calcium oxide, calcium fluoride, calcium sulfate, sodium fluorosilicate, potassium fluorosilicate, and potassium fluoroaluminate.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for detecting the primary crystallization temperature of a refining agent, comprising the following steps: grinding the refining agent sample to be tested and placing it in a transparent container, inserting the temperature measuring end of a thermocouple into the sample; placing the transparent container containing the sample in a heating device, heating it until the sample forms a homogeneous melt, and then cooling it down; continuously acquiring the temperature-time signal output by the thermocouple during the cooling process, and simultaneously observing the state change of the melt; plotting a cooling curve based on the temperature-time signal, and recording the inflection point temperature at which the cooling curve first deviates from the linear cooling trend as the first temperature; recording the temperature at which the melt first shows turbidity or solid particles as the second temperature, and taking the average of the first temperature and the second temperature to obtain the primary crystallization temperature of the refining agent sample to be tested.
[0017] This invention proposes for the first time a method of "synchronous acquisition and fusion judgment of thermal and visual dual signals," avoiding the subjectivity and error of single-signal judgment and significantly improving the objectivity and accuracy of the judgment. This invention abandons the traditional approach of relying on a single thermophysical signal for interpretation. By synchronously and independently acquiring two signals—thermal cooling curves and visual state changes—and establishing a precise correlation between them on the time axis, it provides evidence from two different dimensions for the initial crystallization time. When the thermal signal inflection point (T-thermal) and the visual phase transition point (T-visual) mutually corroborate each other, the reliability of the result is greatly increased; when one signal is ambiguous, the other signal can serve as a key judgment criterion. This dual-channel verification mechanism fundamentally solves the problem of relying on subjective experience for judgment due to the indistinctness of a single signal caused by the properties of refining agents, transforming the judgment process from "empirical estimation" to "data verification," enhancing objectivity and ensuring accurate and reliable results. This invention does not rely on the cooling curve as the sole criterion, but introduces an independent visual observation signal, avoiding the problem of inaccurate judgment due to the indistinctness of the cooling curve inflection point. The two complement and cross-verify each other.
[0018] The detection method of this invention has good equipment versatility: it has no special restrictions on specific equipment, only requiring controllable heating and cooling, synchronous temperature measurement, and process observation functions, making it easy to conduct in various laboratories. This invention does not require the use of dedicated and expensive integrated equipment such as DSC or hot-stage microscopes. This low dependence on hardware platforms allows the method to flexibly adapt to different levels of equipment and budget conditions, from R&D laboratories to production quality control sites, greatly improving the method's scalability.
[0019] The detection method of this invention is intuitive and visual: visual observation visualizes the phase transformation process, helping operators understand solidification behavior and detect anomalies. This invention mandates visual observation as a necessary step in the measurement process. This is not only for obtaining T-visual data (second temperature), but also brings additional technical benefits. Operators can intuitively see rich information such as the nucleation location of primary crystals, crystal growth morphology, and changes in melt transparency. This information is of significant reference value for a deeper understanding of the solidification characteristics of refining agents, assessing their homogeneity, and making preliminary judgments about their compositional stability. For example, observing abnormal segregation or non-uniform nucleation may indicate uneven sample mixing or the presence of impurities. By observing changes in the melt state, this invention enhances the intuitiveness and information content of the test, surpassing traditional tests that only obtain a temperature figure, and facilitates more in-depth process analysis and problem diagnosis. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a cooling curve diagram of refining agent JZ in Example 1; Figure 2 This is a cooling curve diagram of refining agent SX in Example 1; Figure 3 This is a cooling curve diagram of refining agent XZ in Example 1; Figure 4 This is a cooling curve diagram of the refining agent PY in Example 1; Figure 5 The cooling curve is shown in Example 2 when the cooling rate is 0.2℃ / s. Figure 6 The cooling curve is shown in Example 2 when the cooling rate is 0.5℃ / s. Figure 7 The cooling curve is shown in Example 2 when the cooling rate is 1.2℃ / s. Detailed Implementation
[0022] This invention provides a method for detecting the primary crystallization temperature of a refining agent, comprising the following steps: After grinding the sample of the refining agent to be tested, it is placed in a transparent container, and the temperature measuring end of the thermocouple is inserted into the sample. A transparent container containing the sample is placed in a heating device and heated until the sample forms a homogeneous melt. Then, the sample is cooled down. During the cooling process, the temperature-time signal output by the thermocouple is continuously acquired, and the state changes of the melt are observed. A cooling curve is plotted based on the temperature-time signal. The inflection point temperature at which the cooling curve first deviates from the linear cooling trend is recorded as the first temperature. The temperature at which the melt first appears turbid or solid particles is recorded as the second temperature. The average of the first and second temperatures is taken to obtain the primary crystallization temperature of the refining agent sample to be tested.
[0023] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.
[0024] In this invention, the sample of the refining agent to be tested is ground and placed in a light-transmitting container, and the temperature measuring end of a thermocouple is inserted into the sample.
[0025] In this invention, the refining agent sample to be tested is preferably a refining agent for aluminum or aluminum alloy smelting, and the refining agent for aluminum or aluminum alloy smelting preferably includes one or more of sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, magnesium fluoride, calcium chloride, calcium oxide, calcium fluoride, calcium sulfate, sodium fluorosilicate, potassium fluorosilicate, and potassium fluoroaluminate.
[0026] In this invention, the grinding time is preferably 10-30 seconds, specifically 20 seconds, and the rotation speed is preferably 1000-1100 rpm, specifically 1050 rpm. The particle size of the ground sample is preferably ≤150 μm.
[0027] In this invention, the light-transmitting container is preferably a sapphire tube or a high-temperature resistant glass tube; the light-transmitting container is resistant to corrosion by high-temperature molten salt. The sample filling height in the light-transmitting container is preferably not less than 20 mm, more preferably 20-30 mm, and in this specific embodiment of the invention, it is 20 mm. The temperature-sensing end of the thermocouple is preferably inserted into the middle of the sample to ensure good thermal contact.
[0028] The present invention places a light-transmitting container containing a sample in a heating device, heats the sample until it forms a homogeneous melt, and then cools it down. During the cooling process, the temperature-time signal output by the thermocouple is continuously collected, and the state changes of the melt are observed. A cooling curve is plotted based on the temperature-time signal. The inflection point temperature at which the cooling curve first deviates from the linear cooling trend is recorded as the first temperature. The temperature at which the melt first appears turbid or solid particles is recorded as the second temperature. The average of the first and second temperatures is taken to obtain the primary crystallization temperature of the refining agent sample to be tested.
[0029] In this invention, the heating device is preferably the HLT fully automatic primary crystal temperature measurement system, manufactured by Beijing Core Power Technology Co., Ltd.
[0030] In this invention, the heating rate is preferably 0.3~1℃ / s, specifically 0.8℃ / s; the heating until the sample forms a homogeneous melt preferably includes: heating until the sample melts, then continuing to heat to above 50℃ (specifically 700~800℃) of the sample's estimated melting point, and holding at that temperature for 5~15 minutes; the continued heating can make the melt composition and temperature uniform.
[0031] In this invention, the cooling rate is preferably no higher than 0.5℃ / s, more preferably 0.3~0.5℃ / s. With the cooling rate described in this invention, the transition of the melt from clarification to primary crystal precipitation is clear, and the final measured primary crystal temperature is accurate and reliable.
[0032] In this invention, the acquisition frequency of the temperature-time signal output by the thermocouple is preferably 5~10Hz.
[0033] In this invention, the observation of the melt's state changes is preferably performed using a high-speed camera or a microscopic imaging system to improve resolution and accuracy. The recording of the observations is preferably based on a unified time reference with the temperature-time signal to ensure precise temporal correlation between visual information and thermal signals, thereby enabling accurate matching of the observed physical changes instantaneously with the corresponding temperature values.
[0034] This invention achieves high-precision and high-reliability determination of primary crystal temperature through mutual verification of thermal and visual signals. By simultaneously verifying and averaging the inflection point of the thermal signal and the visual phase transition point, systematic and random errors are effectively offset, resulting in good repeatability and meeting the requirements of industrial R&D and quality control.
[0035] To further illustrate the present invention, the method for detecting the primary crystallization temperature of refining agents provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0036] The HLT fully automated primary crystallization temperature measurement system used in the following examples was manufactured by Beijing Core Power Technology Co., Ltd. The refining agents to be tested, JZ, include: MgCl2, MgF2, NaCl, Na2SO4, Na2SiF6, CaSO4, and CaCl2; SX includes: MgCl2, KCl, NaCl, KAlF4, and CaF2; XZ includes: MgCl2, KCl, NaCl, KAlF4, and K2SiF6; PY includes: MgCl2, KCl, and NaCl.
[0037] Tubular containers with good light transmittance and resistance to high-temperature molten salt corrosion: The material is transparent quartz glass with a light transmittance of not less than 90%. The outer diameter of the quartz glass tube is 12~15mm, the inner diameter is 8~10mm, and the wall thickness is 1.5~2.0mm.
[0038] Example 1 (1) Sample preparation and loading: Take the powder of the refining agent to be tested, grind it for 20s (1100rpm), and then load it into a tubular container with good light transmittance and resistance to high temperature molten salt corrosion. The loading height is 2cm. Insert the measuring end of a calibrated thin wire thermocouple into the middle of the sample to ensure good thermal contact.
[0039] (2) Melting and homogenization: The assembled sample is placed in a temperature-controlled heating device (HLT fully automatic primary crystal temperature measurement system) and heated to complete melting at a heating rate of 0.8℃ / s. Then, the temperature is increased to 700℃ and held for 5 minutes to obtain a melt with uniform composition and clear structure.
[0040] (3) Synchronous monitoring and data acquisition: Start program control to cool at a rate of 0.5℃ / s. During the cooling process, the thermal signal acquisition system and visual observation system are operated simultaneously, as follows: Thermal signal acquisition system: continuously and at high frequency records the temperature-time signal output by the thermocouple to generate a complete cooling curve dataset, as shown in Table 1; Visual observation system: Simultaneously and continuously observe and record visual information throughout the cooling process; continuously monitor the physical state changes of the sample melt and record its evolution over time; to ensure that visual information and thermal signals are accurately correlated in the time dimension, the observation records and temperature data acquisition adopt a unified time reference.
[0041] Table 1. Temperature-Time Measurement Data of Refining Agent
[0042] (4) Data Analysis: After the cooling process is completed, the collected thermal signal data and visual data are analyzed respectively. Details are as follows: The cooling curve was extracted from the temperature-time data, and the inflection point temperature at which the first deviation from the linear cooling trend was recorded as T-thermal (first temperature); the cooling curve of refining agent JZ is as follows. Figure 1 As shown, the cooling curve of refining agent SX is as follows: Figure 2 As shown, the cooling curve of refining agent XZ is as follows: Figure 3 As shown, the cooling curve of refining agent PY is as follows: Figure 4 As shown.
[0043] Identify the moment when turbidity or solid particles first appear from the visual recording, and read the corresponding temperature as T-visual (second temperature). The primary crystallization temperature of the refining agent powder sample was calculated based on the formula Tx = (T - thermal + T - visual) / 2, and the results are shown in Table 2. Table 2. Test results of the primary crystallization temperature of the refining agent in Example 1.
[0044] Table 2 shows that, using the method of this invention to measure four different refining agent samples, the average absolute deviation between the results obtained from the thermal signal system and the visual observation system was only 1.1℃, indicating that the dual-signal acquisition has high synchronization and consistency. The primary crystallization temperature values obtained through fusion determination are inherently consistent and can clearly distinguish different samples with a range of up to 59.2℃. This fully demonstrates that the method of this invention effectively overcomes the problems of fuzzy interpretation and strong subjectivity in traditional single-signal methods, and achieves objective, accurate, and reliable measurement of the primary crystallization temperature of refining agents.
[0045] Example 2 For the same refining agent sample (sample #1 includes MgCl2, KCl, NaCl, and CaCl2), three parallel experiments were conducted by varying the cooling rate of the HLT fully automated primary crystallization temperature measurement system. The consistency of the two signals under different cooling rates was evaluated by calculating the absolute deviation between T-thermal and T-visual values, thus allowing for the selection of a cooling rate that yields more stable and reliable measurement results. The results are shown in Table 3. Table 3. Test results of the refining agent in Example 2.
[0046] Based on the three sets of experiments above, it can be seen that the cooling rate is a key parameter affecting the accuracy and reliability of the "thermal-visual dual-signal fusion determination method". A cooling rate of 0.5℃ / s is the optimal condition for achieving high-precision and high-reliability measurements.
[0047] Compared with the prior art, the detection method of the present invention has the following advantages, as shown in Table 4: Table 4 Comparison results between the present invention and the prior art
[0048] This invention provides a novel measurement method that does not rely on the interpretation of a single signal. It simultaneously acquires thermal signals (temperature-time curve) and visual signals (melt state changes) during the sample cooling process, and determines the primary crystallization temperature through the fusion analysis and cross-validation of these two signals. This invention solves the problem of ambiguous interpretation of a single thermal signal: by introducing independent visual observation, it provides direct and objective physical evidence for the determination of the primary crystallization time, compensating for the lack of a clear inflection point in the cooling curve due to the low latent heat of solidification of the refining agent. This invention reduces reliance on expensive specialized equipment: the detection method of this invention has no special requirements for the specific model of the equipment used; it only needs basic controllable heating and cooling, temperature recording, and process observation functions. This allows the method to be applied in a wider range of laboratory and production environments, significantly reducing the implementation threshold and cost.
[0049] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for detecting the primary crystallization temperature of a refining agent, characterized in that, Includes the following steps: After grinding the sample of the refining agent to be tested, it is placed in a transparent container, and the temperature measuring end of the thermocouple is inserted into the sample. A transparent container containing the sample is placed in a heating device and heated until the sample forms a homogeneous melt. Then, the sample is cooled down. During the cooling process, the temperature-time signal output by the thermocouple is continuously acquired, and the state changes of the melt are observed. A cooling curve is plotted based on the temperature-time signal. The inflection point temperature at which the cooling curve first deviates from the linear cooling trend is recorded as the first temperature. The temperature at which the melt first appears turbid or solid particles is recorded as the second temperature. The average of the first and second temperatures is taken to obtain the primary crystallization temperature of the refining agent sample to be tested.
2. The detection method according to claim 1, characterized in that, The cooling rate is no higher than 0.5℃ / s.
3. The detection method according to claim 2, characterized in that, The cooling rate is 0.3~0.5℃ / s.
4. The detection method according to claim 1, characterized in that, The heating rate is 0.3~1℃ / s.
5. The detection method according to claim 1 or 4, characterized in that, The heating process until the sample forms a homogeneous melt includes: heating the sample until it melts, then continuing to heat it to 700-800°C and holding it at that temperature for 5-15 minutes.
6. The detection method according to claim 1, characterized in that, The grinding time is 15~30s, and the rotation speed is 1000~1100rpm.
7. The detection method according to claim 1, characterized in that, The filling height of the sample in the transparent container shall not be less than 20 mm.
8. The detection method according to claim 1 or 7, characterized in that, The light-transparent container is a sapphire tube or a high-temperature resistant glass tube.
9. The detection method according to claim 1, characterized in that, The state changes of the melt are observed using a high-speed camera or a microscopic imaging system.
10. The detection method according to claim 1, characterized in that, The refining agent sample to be tested is a refining agent for smelting aluminum or aluminum alloys, and the refining agent for smelting aluminum or aluminum alloys includes one or more of sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, magnesium fluoride, calcium chloride, calcium oxide, calcium fluoride, calcium sulfate, sodium fluorosilicate, potassium fluorosilicate, and potassium fluoroaluminate.