Hydrogen content on-line detection method suitable for aluminum casting process

Abstract

The invention provides a hydrogen content online detection method suitable for an aluminum casting process, and relates to the technical field of hydrogen content detection, the hydrogen content online detection method comprises the following steps: S1, determining solubility constants A and B related to alloy components; s2, measuring the temperature T of the aluminum melt; s3, the hydrogen partial pressure PH2 in the melt is measured; s4, calculating the hydrogen content in the melt according to a solubility formula; according to the method, only solubility constants A and B related to alloy components need to be found from related data, the melt temperature T is measured through the thermocouple, the hydrogen partial pressure PH2 in the melt is measured, the hydrogen content in the melt can be calculated in cooperation with a solubility formula, the measurement precision is high, operation is easy, multi-point measurement is convenient, the melt temperature T is measured through the thermocouple, and the hydrogen content in the melt can be calculated. The thermocouples are selected and calibrated in the process, the accuracy is improved, the whole measurement process comprises interval measurement and continuous measurement, and hydrogen measurement data are more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen content detection, and in particular to an online hydrogen content detection method suitable for an aluminum smelting and casting process. Background Art

[0002] It is inevitable for aluminum and aluminum alloys to absorb hydrogen during the melting and casting process, and the solubility of hydrogen in aluminum increases with the increase of temperature. When liquid aluminum and solid aluminum coexist in equilibrium, the solubility of hydrogen in solid aluminum is nearly twenty times smaller than that of liquid aluminum at the same temperature. When liquid aluminum and aluminum alloys solidify, the hydrogen precipitated has no time to diffuse and escapes quickly, causing defects such as pores and looseness in the ingot, destroying the continuity of the metal, thereby reducing the mechanical properties of the ingot. These defects cannot be eliminated in the subsequent pressure processing, thereby reducing the performance of the processed material. The hydrogen content of aluminum and aluminum alloys is generally measured by a hydrogen meter. The purpose of the measurement is to predict the hydrogen content in the melt and then reduce the hydrogen content in the melt through some corresponding process means to below the critical value of pores and looseness, thereby ensuring the quality of the cast ingot;

[0003] At present, there are more than 20 methods for measuring hydrogen in aluminum melt in the world, among which the "closed loop circulation method" (also known as the Telegas method) is relatively good, but it also has certain limitations and errors, such as the measurement is not convenient and fast enough, and the error range fluctuates greatly. Therefore, the present invention proposes an online detection method for hydrogen content in the aluminum casting process to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the present invention proposes an online detection method for hydrogen content in the aluminum casting process. The online detection method for hydrogen content in the aluminum casting process only needs to find out the solubility constants A and B related to the alloy composition from relevant data, measure the melt temperature T by thermocouple, and measure the hydrogen partial pressure PH2 in the melt. The hydrogen content in the melt can be calculated by combining with the solubility formula. The method has high measurement accuracy, simple operation, and is convenient for multi-point measurement.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: an online detection method for hydrogen content in an aluminum casting process, comprising the following steps:

[0006] S1: Determine the solubility constants A and B related to the alloy composition;

[0007] S2: Measure the temperature T of the aluminum melt;

[0008] S3: Determine the hydrogen partial pressure PH2 in the melt;

[0009] S4: Calculate the hydrogen content in the melt according to the solubility formula.

[0010] A further improvement is that the solubility CH of hydrogen in the aluminum melt is related to the partial pressure PH2 of hydrogen in the melt at this temperature, and the relationship is:

[0011]

[0012] Where ES is the gram molecular heat of solution of hydrogen, K is a constant, T is the Fahrenheit temperature of the melt, CH is the solubility of hydrogen in the melt ml / 100gAl, and PH2 is the hydrogen partial pressure in the melt in mpa.

[0013] Further improvement is: It can be expressed as Sievert's law:

[0014] logCH2=0.5logPH 2 -A / T+B

[0015] Where A and B are solubility constants related to the alloy composition. The hydrogen content in the melt can be calculated by determining A, B, T in the formula and measuring PH2.

[0016] A further improvement is that in S1, the solubility constants A and B are parameters related to the composition of aluminum or aluminum alloy, which are used to describe the relationship between the solubility of hydrogen in aluminum melt and the hydrogen partial pressure and temperature in the melt. The constants are used to be obtained from online databases and academic materials.

[0017] A further improvement is that in S2, the temperature T of the aluminum melt is directly measured using a thermocouple, comprising the following steps:

[0018] According to the temperature range and accuracy requirements of the aluminum casting process, select the thermocouple, calibrate the thermocouple, place the thermocouple and the high-precision thermometer in the same standard temperature environment, compare the readings of the two, and record the deviation value to correct the subsequent data;

[0019] Drill a hole at a suitable location of the aluminum casting equipment, slowly insert the measuring end of the thermocouple into the melt, make sure the measuring end is completely immersed in the melt and does not contact the inner wall or other parts of the equipment, and at the same time, fix the wiring end of the thermocouple and connect it to the measuring instrument;

[0020] Connect the thermocouple to the data acquisition device, start the data acquisition system, collect the voltage signal output by the thermocouple in real time, and convert the voltage signal into the corresponding temperature value according to the thermocouple graduation table to obtain the melt temperature T.

[0021] A further improvement is to filter the collected temperature data to remove noise data.

[0022] A further improvement is that: S3 comprises the following steps:

[0023] A cylindrical porous graphite probe connected to a pressure measuring instrument through a gas-tight ceramic tube is directly immersed in the aluminum melt to be measured;

[0024] Quickly remove the air in the probe to make the probe a "bubble" for hydrogen diffusion;

[0025] The hydrogen in the melt diffuses into the "bubbles" until the hydrogen partial pressure in the "bubbles" reaches equilibrium with the hydrogen partial pressure in the melt;

[0026] The hydrogen partial pressure in the probe is measured to obtain the hydrogen partial pressure PH2 in the melt.

[0027] A further improvement is that the entire measurement process includes interval measurement and continuous measurement. When interval measurement is used, the number of measurements and the interval time are customized according to accuracy requirements and work needs.

[0028] A further improvement is that when continuous measurement is adopted, after obtaining the first hydrogen measurement data, an interval time x is set for continuous measurement, and the process parameters are adjusted according to the hydrogen content fed back.

[0029] A further improvement is that in the interval measurement and the continuous measurement, multi-point measurement is performed.

[0030] The beneficial effects of the present invention are:

[0031] 1. The present invention only needs to find out the solubility constants A and B related to the alloy composition from relevant data, measure the melt temperature T by thermocouple, and measure the hydrogen partial pressure PH2 in the melt. The hydrogen content in the melt can be calculated by combining with the solubility formula. The measurement has high accuracy, simple operation, and is convenient for multi-point measurement.

[0032] 2. The present invention measures the melt temperature T by means of a thermocouple, during which the thermocouple is selected and calibrated to improve accuracy. The entire measurement process includes interval measurement and continuous measurement, and the hydrogen measurement data is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a front view of the present invention;

[0034] Figure 2 It is a schematic diagram of the probe structure of the present invention;

[0035] Figure 3 It is a schematic diagram of the gas circuit principle of the present invention. DETAILED DESCRIPTION

[0036] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0037] Embodiment 1

[0038] According to Figure 1 、 2 As shown in 3, this embodiment proposes an on-line detection method for hydrogen content applicable to the aluminum melting and casting process, including the following steps:

[0039] S1: Determine the solubility constants A and B related to the alloy composition; The solubility constants A and B are parameters related to the composition of aluminum or aluminum alloy, and are used to describe the relationship between the solubility of hydrogen in the aluminum melt, the partial pressure of hydrogen in the melt, and the temperature. These constants are obtained from on-line databases and academic materials; Consult professional books: Professional books in the fields of metal materials science, metallurgy, etc. will contain information on the solubility constants of aluminum and aluminum alloys. These books will provide detailed experimental data and theoretical explanations, which are helpful for understanding the source and calculation method of the solubility constants. Search academic journals: Academic journals are important platforms for publishing the latest research results. By searching relevant academic journals, find the latest research results on the solubility constants of aluminum and aluminum alloys. These studies will provide more accurate and detailed solubility constant data, as well as the corresponding experimental methods and theoretical bases. Refer to industry standards: Industry standards will stipulate the range of solubility constants of aluminum and aluminum alloys under specific conditions. These standards provide guidance for actual production to ensure the stability and consistency of product quality. Utilize on-line databases: With the development of information technology, more and more on-line databases provide information on the solubility constants of aluminum and aluminum alloys. These databases contain a large amount of experimental data and theoretical models, and can be queried and downloaded as needed. Consult experts or institutions: When the required solubility constant data cannot be directly found, consult experts or institutions in related fields. Provide the latest research results or experimental data, as well as suggestions on how to calculate and use these constants.

[0040] S2: Measure the temperature T of the aluminum melt; the temperature T of the aluminum melt is directly measured using a thermocouple, including the following steps: select a thermocouple according to the temperature range and accuracy requirements of the aluminum casting process, calibrate the thermocouple, place the thermocouple and a high-precision thermometer in the same standard temperature environment, compare the readings of the two, and record the deviation value to correct subsequent data; open a hole at a suitable position of the aluminum casting equipment, slowly insert the measuring end of the thermocouple into the melt, ensure that the measuring end is completely immersed in the melt, and does not contact the inner wall or other components of the equipment, and at the same time, fix the wiring terminal of the thermocouple and connect it to the measuring instrument; connect the thermocouple to the data acquisition device, start the data acquisition system, collect the voltage signal output by the thermocouple in real time, and convert the voltage signal into a corresponding temperature value according to the thermocouple graduation table to obtain the melt temperature T. Filter the collected temperature data to remove noise data; Specifically: Thermocouple selection: The temperature of the aluminum casting process is usually 600-900℃. For the case where the accuracy requirement is within ±1℃, the K-type thermocouple has good linearity and stability within this temperature range and is relatively low in cost, so it is a more suitable choice; if the accuracy requirement reaches ±0.5℃, the S-type thermocouple is more expensive, but it can meet the high-precision measurement requirements. When selecting, consider the size of the thermocouple to ensure that its measuring end can be smoothly inserted into the aluminum casting equipment and will not cause significant interference to the melt flow in the equipment. Thermocouple calibration: Put a high-precision thermometer (with an accuracy of up to ±0.1℃) and the thermocouple to be calibrated into the constant temperature box. Set the temperature of the constant temperature box to the common temperature points in the aluminum casting process, such as 700℃ and 800℃. After the temperature in the constant temperature box stabilizes, record the readings of the high-precision thermometer and thermocouple every 5 minutes, for a total of 10 times. Calculate the difference between the thermocouple reading and the high-precision thermometer reading in each measurement, and take the average value as the deviation value at that temperature point. For example, at 700°C, the deviation values ​​of 10 measurements are 0.3°C, 0.25°C, 0.32°C, etc., and the average deviation value is calculated to be 0.3°C. When measuring near this temperature later, the thermocouple measurement data can be corrected according to this deviation value. Thermocouple installation: Select a hole on the furnace wall of the aluminum casting equipment away from the inlet and outlet, stirring device, etc. to ensure that the measured temperature can represent the overall temperature of the melt. Use a special installation fixture to slowly insert the measuring end of the thermocouple into the melt. The insertion depth should reach 2 / 3 of the melt depth to ensure that the measuring end is completely immersed in the melt. At the same time, wrap the thermocouple terminal with high-temperature resistant insulating material to prevent it from short-circuiting with the equipment casing, and then connect the terminal to the measuring instrument to ensure a firm connection to avoid looseness during the measurement process, resulting in abnormal signal transmission. Data acquisition and processing: Connect the output end of the thermocouple to the data acquisition device, and set the sampling frequency of the data acquisition device to 10 times per second to ensure that the slight change in temperature can be captured in time. After turning on the data acquisition system, the voltage signal output by the thermocouple is collected in real time.According to the graduation table of the selected thermocouple, the voltage signal is converted into the corresponding temperature value through the linear interpolation algorithm. For example, the output voltage of the thermocouple is 20mV. In the graduation table, the temperature corresponding to 20mV is between 750℃-755℃. The accurate temperature value is calculated by linear interpolation. The collected temperature data will be affected by equipment vibration, electromagnetic interference, etc., resulting in noise data. The sliding average filter method is used to set the filter window to 5 data points, that is, the average calculation is performed on every 5 consecutive collected temperature data to obtain a new temperature value, thereby removing the noise data and obtaining the accurate melt temperature T.

[0041] S3: Determine the hydrogen partial pressure PH2 in the melt; specifically includes the following steps: directly immerse a cylindrical porous graphite probe connected to a pressure measuring instrument through an airtight ceramic tube into the aluminum melt to be measured; quickly remove the air in the probe to make the probe a "bubble" for hydrogen diffusion; the hydrogen in the melt diffuses into the "bubble" until the hydrogen partial pressure in the "bubble" reaches equilibrium with the hydrogen partial pressure in the melt; measure the hydrogen partial pressure in the probe to obtain the hydrogen partial pressure PH2 in the melt; specifically: the selected cylindrical porous graphite probe must have a porosity of 30%-40% to ensure that hydrogen can quickly diffuse into the probe while preventing a large amount of aluminum melt from infiltrating. The inner diameter of the airtight ceramic tube must be compatible with the connection port of the graphite probe and the pressure measuring instrument to ensure a tight connection without gas leakage. Before connection, the airtight ceramic tube and the graphite probe are tested for airtightness, placed in a sealed container filled with helium, and the change in the helium concentration in the container is detected to determine whether there is a leak. The pressure gauge needs to be calibrated in advance, and the calibration range should cover the possible hydrogen partial pressure range during aluminum casting, such as 0-100kPa, and the calibration accuracy should reach ±0.1kPa. Probe immersion: When the aluminum casting equipment is running stably and the melt is in a uniform state, a specially designed mechanical arm is used to slowly and vertically immerse the cylindrical porous graphite probe connected to the airtight ceramic tube and the pressure gauge into the aluminum melt to be measured. The immersion depth is controlled at 20-30cm below the surface of the melt. This position can better represent the overall hydrogen partial pressure of the melt. During the immersion process, keep the probe stable and avoid shaking to prevent the diffusion balance of hydrogen from being affected by local disturbances. Pumping operation: When the probe is immersed to the specified depth, immediately start the vacuum pump connected to the airtight ceramic tube to quickly remove the air in the probe within 3-5 seconds, so that a negative pressure environment is formed inside the probe, which becomes a "bubble" for hydrogen diffusion. During the vacuuming process, by observing the reading of the pressure gauge, ensure that the pressure in the probe is quickly reduced to a near-vacuum state, and control the pressure value to be less than 0.1kPa. Diffusion equilibrium: Hydrogen in the melt diffuses into the "bubbles" under the action of concentration difference. During the diffusion process, record the reading of the pressure gauge every 10 seconds. As hydrogen continues to enter the probe, the pressure gradually increases. When the pressure value recorded for three consecutive times changes less than 0.05kPa, it is judged that the hydrogen partial pressure in the "bubbles" is in equilibrium with the hydrogen partial pressure in the melt. This process takes 2-5 minutes, depending on the initial concentration and diffusion rate of hydrogen in the melt. Partial pressure measurement: After confirming that equilibrium has been reached, read the pressure value displayed by the pressure gauge at this time, which is the hydrogen partial pressure in the probe, that is, the hydrogen partial pressure PH2 in the melt. To ensure the accuracy of the measurement, the pressure gauge needs to be zeroed after each measurement to prevent the instrument drift from affecting the next measurement result.

[0042] S4: Calculate the hydrogen content in the melt according to the solubility formula. The entire measurement process includes interval measurement and continuous measurement. When interval measurement is used, the number of measurements and the interval time are customized according to the accuracy requirements and work needs. When continuous measurement is used, after obtaining the first hydrogen measurement data, set the interval time x for continuous measurement, and adjust the process parameters according to the feedback of hydrogen content. In interval measurement and continuous measurement, multi-point measurement is performed.

[0043] The solubility of hydrogen in aluminum melt, CH, is related to the partial pressure of hydrogen in the melt at this temperature, PH2, and the relationship is:

[0044]

[0045] Where ES is the gram molecular heat of solution of hydrogen, K is a constant, T is the Fahrenheit temperature of the melt, CH is the solubility of hydrogen in the melt ml / 100gAl, and PH2 is the hydrogen partial pressure in the melt in mpa.

[0046] Will It can be expressed as Sievert's law:

[0047] logCH2=0.5logPH 2 -A / T+B

[0048] Where A and B are solubility constants related to the alloy composition. The hydrogen content in the melt can be calculated by determining A, B, T in the formula and measuring PH2.

[0049] Embodiment 2

[0050] according to Figure 1 , 2 As shown in FIG. 3 , this embodiment proposes an online detection method for hydrogen content in an aluminum casting process, which realizes multi-point measurement, has accurate hydrogen measurement data, high measurement accuracy, and simple operation, and includes the following steps:

[0051] The solubility of hydrogen in aluminum melt, CH, is related to the partial pressure of hydrogen in the melt at this temperature, PH2. The relationship is: Where ES is the molecular heat of solution of hydrogen, K is a constant, T is the Fahrenheit temperature of the melt, CH is the solubility of hydrogen in the melt ml / 100gAl, and PH2 is the hydrogen partial pressure in the melt mpa. The above formula can also be expressed by Sievert's law as logCH2=0.5logPH 2 -A / T+B, where A and B are solubility constants related to alloy composition, which can be found from relevant data. After A, B, and T in this formula are determined and PH2 is measured, the hydrogen content in the melt can be calculated.

[0052] PH2 is determined using the Happel hydrogen meter. Compared with AlsconⅡ and ELH-IV hydrogen meters, the Happel hydrogen meter has the advantages of objective and accurate hydrogen pressure data, hydrogen partial pressure values ​​can be read at any time, single-point test time is fully automated, increase, decrease or equilibrium of hydrogen content is dynamically displayed, and it can be quickly compared with the set value.

[0053] The method for measuring PH2 is to immerse a cylindrical porous graphite probe connected to a pressure measuring instrument through an airtight ceramic tube directly into the aluminum melt to be measured, and quickly remove the air in the probe. At this time, the probe is like a "bubble" made by a person, and the hydrogen in the melt diffuses into the "bubble" until the hydrogen partial pressure in the "bubble" reaches equilibrium with the hydrogen partial pressure in the green leaves. At this time, you only need to measure the hydrogen partial pressure in the probe to know the hydrogen partial pressure PH2 in the melt. At the same time, the melt temperature T is measured by a thermocouple, and the hydrogen content in the melt can be calculated according to the formula.

[0054] Technical data:

[0055] Measuring range: 0.02-9.99ml / 100g

[0056] Measuring accuracy ±0.015ml / 100g

[0057] Repeatability: 0.01ml / 100g

[0058] Serial port RS232

[0059] Weight Approximately 18.7kg

[0060] Dimensions: 445x350x310mm

[0061] Power supply 230VAC or 115VAC

[0062] Thermocouple Xx Nickel-Chromium-Nickel (Ni-Cr-Ni)

[0063] Applicable aluminum alloy components Si, Cu, Mg, Mn

[0064] Measurement method: 1. Interval measurement: The number of measurements depends on the accuracy, requirements and work needs, and the interval time is a few minutes

[0065] 2. Continuous measurement: Get the interval x of the first hydrogen measurement data and feedback the hydrogen content.

[0066] The method for online detection of hydrogen content in the aluminum casting process only needs to find out the solubility constants A and B related to the alloy composition from relevant data, measure the melt temperature T by thermocouple, and measure the hydrogen partial pressure PH2 in the melt, and the hydrogen content in the melt can be calculated by combining with the solubility formula, with high measurement accuracy, simple operation, and convenient multi-point measurement. At the same time, the present invention measures the melt temperature T by thermocouple, selects and calibrates the thermocouple in the process, improves accuracy, and the entire measurement process includes interval measurement and continuous measurement, and the hydrogen measurement data is more accurate.

[0067] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for online detection of hydrogen content in aluminum casting process, characterized in that: The following steps are involved: S1: Determine the solubility constants A and B related to the alloy composition; S2: Measure the temperature T of the aluminum melt; S3: Determine the hydrogen partial pressure PH2 in the melt; S4: Calculate the hydrogen content in the melt according to the solubility formula.

2. The method for online detection of hydrogen content in aluminum casting process according to claim 1 is characterized in that: The solubility of hydrogen in aluminum melt, CH, is related to the partial pressure of hydrogen in the melt at this temperature, PH2, and the relationship is: Where ES is the gram molecular heat of solution of hydrogen, K is a constant, T is the Fahrenheit temperature of the melt, CH is the solubility of hydrogen in the melt ml / 100gAl, and PH2 is the hydrogen partial pressure in the melt in mpa.

3. The method for online detection of hydrogen content in aluminum casting process according to claim 2 is characterized in that: Will It can be expressed as Sievert's law: logCH2=0.5logPH2-A / T+B Where A and B are solubility constants related to the alloy composition. The hydrogen content in the melt can be calculated by determining A, B, T in the formula and measuring PH2.

4. The method for online detection of hydrogen content in aluminum casting process according to claim 3 is characterized in that: In S1, the solubility constants A and B are parameters related to the composition of aluminum or aluminum alloy, and are used to describe the relationship between the solubility of hydrogen in aluminum melt and the hydrogen partial pressure and temperature in the melt. The constants are used to be obtained from online databases and academic materials.

5. The method for online detection of hydrogen content in aluminum casting process according to claim 1 is characterized in that: In S2, the temperature T of the aluminum melt is directly measured using a thermocouple, comprising the following steps: According to the temperature range and accuracy requirements of the aluminum casting process, select the thermocouple, calibrate the thermocouple, place the thermocouple and the high-precision thermometer in the same standard temperature environment, compare the readings of the two, and record the deviation value to correct the subsequent data; Drill a hole at a suitable location of the aluminum casting equipment, slowly insert the measuring end of the thermocouple into the melt, make sure the measuring end is completely immersed in the melt and does not contact the inner wall or other parts of the equipment, and at the same time, fix the wiring end of the thermocouple and connect it to the measuring instrument; Connect the thermocouple to the data acquisition device, start the data acquisition system, collect the voltage signal output by the thermocouple in real time, and convert the voltage signal into the corresponding temperature value according to the thermocouple graduation table to obtain the melt temperature T.

6. The method for online detection of hydrogen content in aluminum casting process according to claim 5 is characterized in that: The collected temperature data is filtered to remove noise data.

7. The method for online detection of hydrogen content in aluminum casting process according to claim 1 is characterized in that: The S3 comprises the following steps: A cylindrical porous graphite probe connected to a pressure measuring instrument through a gas-tight ceramic tube is directly immersed in the aluminum melt to be measured; Quickly remove the air in the probe to make the probe a "bubble" for hydrogen diffusion; The hydrogen in the melt diffuses into the "bubbles" until the hydrogen partial pressure in the "bubbles" reaches equilibrium with the hydrogen partial pressure in the melt; The hydrogen partial pressure in the probe is measured to obtain the hydrogen partial pressure PH2 in the melt.

8. The method for online detection of hydrogen content in aluminum casting process according to claim 1 is characterized in that: The entire measurement process includes interval measurement and continuous measurement. When interval measurement is used, the number of measurements and interval time are customized according to accuracy requirements and work needs.

9. The method for online detection of hydrogen content in aluminum casting process according to claim 8, characterized in that: When continuous measurement is used, after the first hydrogen measurement data is obtained, an interval time x is set for continuous measurement, and the process parameters are adjusted according to the fed-back hydrogen content.

10. The method for online detection of hydrogen content in aluminum casting process according to claim 9, characterized in that: In interval measurement and continuous measurement, multi-point measurement is performed.

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