Hydrogen absorption prevention sample preparation and detection method for titanium alloy hydrogen content detection

Abstract

The application discloses a kind of titanium alloy hydrogen content detection's anti-hydrogen absorption sample preparation and detection method, belong to metallurgical material detection technical field.The application includes: titanium alloy sample is processed into block, after ultrasonic cleaning in acetone is dried in humidity ≤24% environment, and in 4 hours detection or vacuum sealing preservation;Select tin sheet as dissolvent, tin sheet and sample mass ratio is 1:2;Graphite crucible is carried out empty burning pretreatment;Inert gas melting thermal conductivity method detection parameter is set as analysis power 2.7KW, degassing power 4.5KW, analysis time 120 seconds, cooling water temperature ≤28 ℃;Tin sheet is placed in the bottom of crucible, after adding sample, detection is carried out.The application is through anti-hydrogen absorption combined process, tin sheet high-efficiency fluxing and crucible empty burning pretreatment, effectively suppresses titanium alloy hydrogen absorption, realizes sample complete melting, eliminates crucible residual interference, the relative standard deviation of detection result is ≤3%, significantly improves detection accuracy and repeatability, applicable to the precision quality control of hydrogen content in titanium alloy and special steel.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical material testing technology, specifically relating to a method for detecting hydrogen content in titanium and titanium alloys, and more particularly to a method for accurately determining hydrogen content in titanium alloys through hydrogen absorption-preparation treatment, optimization of flux selection and detection parameters. Background Technology

[0002] Titanium and titanium alloys are widely used in aerospace, marine engineering, biomedicine, and special equipment due to their excellent specific strength, corrosion resistance, and biocompatibility. Hydrogen content is one of the key indicators affecting the mechanical properties of titanium alloys (such as plasticity, toughness, and resistance to hydrogen embrittlement), therefore, accurate detection of its content has important engineering significance.

[0003] Currently, the determination of hydrogen content in titanium alloys mainly follows the national standard GB / T 4698.15-2011 "Determination of Hydrogen Content in Sponge Titanium, Titanium and Titanium Alloys by Chemical Analysis Methods," employing the inert gas melting thermal conductivity method. This method involves melting the sample at high temperature to release hydrogen, which is then quantitatively analyzed using a thermal conductivity detector. Commonly used testing equipment is the Steel Research Institute NACK ONH series oxygen, nitrogen, and hydrogen analyzer. Tin granules or nickel baskets are typically used as fluxes. Samples are directly tested after machining, without special protective measures against hydrogen absorption. The detection power is generally set within the range of 2.1~2.8 kW.

[0004] However, this method has the following prominent problems in practical applications: 1. The sample easily absorbs hydrogen, leading to higher test results: The oxide film on the surface of the titanium alloy has microscopic defects. In a humid environment (such as relative humidity ≥50%), water molecules dissociate and generate H+. + It easily penetrates the matrix, forming TiH2, which leads to a significant increase in hydrogen content and poor repeatability of detection results (RSD can reach 9.47%).

[0005] 2. Incomplete melting of the sample and insufficient hydrogen release: Titanium alloy has a high melting point (about 1668℃), and the melting effect of traditional fluxing agents (such as tin granules and nickel baskets) is limited. The sample still has a grainy feel on the surface after testing, and the hydrogen is not completely released, which affects the accuracy of the test.

[0006] 3. Residual impurities in the crucible interfere with the detection signal: Before treatment, the graphite crucible adsorbs hydrogen, water vapor and organic matter, which are released during the high-temperature detection process, introducing background interference and causing large fluctuations in the detection results (RSD reaches 7.45% when not empty-fired).

[0007] In summary, existing methods for detecting hydrogen content in titanium alloys have significant shortcomings in terms of preventing hydrogen absorption, improving fluxing efficiency, and ensuring proper crucible pretreatment, making it difficult to meet the requirements for high precision and repeatability. Therefore, it is necessary to develop a method for detecting hydrogen content in titanium alloys that can effectively suppress hydrogen absorption, achieve complete melting, and eliminate crucible interference, in order to improve the accuracy and stability of the detection results. Summary of the Invention

[0008] The present invention aims to overcome the technical defects in existing methods for detecting hydrogen content in titanium alloys, and to provide a method for detecting hydrogen content in titanium alloys that can effectively suppress hydrogen absorption in the sample, achieve complete melting of the sample, and eliminate interference from crucible residues, so as to improve the accuracy and repeatability of the detection results, and make the relative standard deviation (RSD) ≤3%, thus meeting the requirements of high-precision detection.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for hydrogen absorption-resistant sample preparation and detection of hydrogen content in titanium alloys includes the following steps: Step 1: Sample preparation and hydrogen absorption prevention treatment Titanium alloy samples are machined into blocks, with a single sample mass of 0.1000 g to 0.3000 g, more preferably 0.18 g to 0.23 g, with an accuracy of ±0.0001 g. Grinding is prohibited to avoid surface hydrogen absorption. The machined samples are then cleaned in an organic solvent to remove surface oil and adsorbates, and then air-dried in an environment with a relative humidity ≤24%. The organic solvent cleaning is preferably performed using acetone followed by ultrasonic cleaning 1-2 times, each time for 5-10 minutes. The dried samples must be tested within 4 hours, or stored under vacuum with a vacuum degree ≤10 Pa, or sealed after argon purging to prevent hydrogen absorption.

[0010] Step 2: Crucible Pretreatment A high-purity graphite crucible (purity ≥ 99.99%) was used and subjected to a dry-burning treatment before detection. The dry-burning conditions were: degassing power 4.5 KW, at least one dry-burning, until the instrument hydrogen signal baseline stabilized (e.g., equivalent hydrogen content below 0.1 ppm), in order to remove residual hydrogen, water vapor and organic matter in the crucible.

[0011] Step 3: Preparation of cosolvent Tin sheet was selected as the sole flux, and the mass ratio of tin sheet to sample was 1:2. Preferably, when the sample mass was 0.18~0.23g, the tin sheet mass was approximately 0.36~0.46g.

[0012] Step 4: Instrument Calibration The inert gas melting thermal conductivity analyzer is calibrated using titanium alloy standard materials (such as GBW(E)020186 and GBW(E)020189) to establish a working curve or perform single-point calibration to ensure detection accuracy.

[0013] Step 5: Setting detection parameters The inert gas melting thermal conductivity method was adopted, and the detection parameters were set as follows: analysis power 2.7 KW, degassing power 4.5 KW, analysis time 120 seconds, and cooling water temperature ≤28℃.

[0014] Step 6: Sample loading and testing Place the weighed tin sheet at the bottom of the graphite crucible, then add the sample, ensuring full contact between the sample and the tin sheet. Place the crucible into the analyzer, start the detection according to the set parameters, determine the hydrogen content using a thermal conductivity detector, and calculate the result using a bridge balance.

[0015] Furthermore, when the ambient humidity exceeds 24%, the sample processing and loading process should be carried out in a glove box or dehumidified environment with a humidity of ≤10%.

[0016] Furthermore, the detection instrument is a Steel Research Institute NAK ONH-3000 or ONH-5500 oxygen, nitrogen, and hydrogen analyzer or an inert gas melting analyzer of the same type.

[0017] Furthermore, the method is applicable to the quality control and detection of hydrogen content in titanium alloy raw materials, semi-finished products, finished products, and special steel production processes.

[0018] Compared with existing technologies, the present invention has the following advantages: The present invention adopts a combined process of "acetone ultrasonic cleaning + vacuum sealing and preservation + low humidity environment (≤24%)" to prevent hydrogen absorption, thus blocking H +The channels penetrating into the titanium alloy matrix inhibited the formation of TiH2. Experiments showed that, under 24% relative humidity, the relative standard deviation (RSD) of the detection results was only 2.96%, far superior to the 9.47% of the prior art (50% humidity). This invention uses tin sheet as a flux. Tin's melting point is only 232℃, forming a low-melting-point eutectic alloy with the titanium alloy, which can rapidly reduce the melting temperature of the titanium alloy. Simultaneously, the tin sheet can encapsulate the sample, breaking the surface oxide film and promoting the full release of internal hydrogen. Combined with a 1:2 flux-to-sample mass ratio, this ensures complete melting of the sample, with no residual particles, and the detection result deviation meets the national standard's allowable range. This invention adds a graphite crucible empty-fire pretreatment step, empty-fired at a degassing power of 4.5 kW until the baseline stabilizes, effectively removing adsorbed hydrogen, water vapor, and organic matter from the crucible, avoiding interference from the release of external impurities on the detection signal. Compared to the unfired crucible (RSD 7.45%), the detection repeatability of this invention is significantly optimized. Furthermore, the method of this invention does not require complex equipment modifications and can be adapted to commonly used inert gas melting analyzers such as the Steel Research Institute NACK ONH-3000. It can also be extended to other oxygen and hydrogen analyzers and the detection of hydrogen content in hydrogen-sensitive metallic materials (such as zirconium alloys and nickel-based alloys), and has broad application prospects. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0020] Example 1 This embodiment provides a method for hydrogen absorption-resistant sample preparation and detection of hydrogen content in titanium alloys. The specific steps are as follows: 1. Sample preparation and hydrogen absorption prevention treatment Take the titanium alloy rod to be tested (grade TC4) and process it into block samples using wire cutting, with each sample weighing 0.2000g. Do not use grinding or sandpaper polishing to avoid surface hydrogen absorption. Place the processed sample in acetone and clean it with an ultrasonic cleaner for 10 minutes. After removal, allow it to air dry in a clean environment with a relative humidity of 20%. Immediately after drying, place the sample into a vacuum-sealed bag, evacuate to a vacuum degree ≤10 Pa, seal the bag, and complete subsequent testing within 2 hours.

[0021] 2. Crucible Pretreatment A high-purity graphite crucible (purity ≥99.99%) was placed in the degassing station of a Steel Research NAK ONH-3000 oxygen, nitrogen, and hydrogen analyzer and fired twice at a degassing power of 4.5 kW, each firing lasting 120 seconds. The instrument's hydrogen signal baseline was observed, and the crucible was removed for later use once the baseline drift was less than 0.1 ppm equivalent.

[0022] 3. Preparation of cosolvents First, experiments were conducted to investigate the effects of different fluxes on the melt characteristics, release characteristics, and relative standard deviation of the measurement results of the samples. The results are shown in Table 1 below: Table 1. Effect of different fluxes on experiments During the experiment, using tin granules as a flux resulted in slight splattering and a noticeably grainy surface on the heated sample. In contrast, using tin sheets produced a smooth sample surface, and the RSD of the melted sample was lower than that of the tin granules. Therefore, tin sheets were selected as the optimal flux (0.0020% hydrogen release, 5.44% relative standard deviation, smooth melt, and good peak shape). In this embodiment, the ratio of tin sheet mass to sample mass was 1:2, i.e., 0.1000 g of tin sheet and 0.2000 g of sample.

[0023] 4. Instrument Calibration Using the titanium alloy hydrogen content standard material GBW(E)020188 (standard value 0.0025%), three repeated measurements were performed under the same testing conditions as the sample to establish a single-point calibration coefficient. Before calibration, the instrument cooling water temperature was confirmed to be 25℃.

[0024] 5. Setting detection parameters The analyzer parameters were set as follows: analysis power 2.7 KW, degassing power 4.5 KW, analysis time 120 seconds, cooling water temperature ≤28℃, and carrier gas (high-purity argon, purity ≥99.999%) flow rate 150 mL / min.

[0025] 6. Sample loading and testing Place the pretreated graphite crucible onto the lower electrode holder of the analyzer. Use tweezers to place the weighed tin sheet at the bottom of the crucible, then carefully add the sample, ensuring full contact between the sample and the tin sheet. Close the furnace and start the detection program. The instrument automatically completes the melting, hydrogen release, and thermal conductivity detection and result calculation according to the set parameters.

[0026] 7. Result Calculation The instrument automatically outputs the hydrogen content mass fraction (%). Repeat the measurement seven times and calculate the relative standard deviation (RSD).

[0027] Test results: The same titanium alloy sample (1#) was repeatedly measured 7 times. The average hydrogen content was 0.0027%, the standard deviation (SD) was 0.0001%, and the relative standard deviation (RSD) was 2.96%. The sample melt was smooth and the peak shape was good.

[0028] Comparative Example 1 TC4 titanium alloy samples from the same batch were tested according to the conventional methods in GB / T 4698.15-2011: after machining, the samples were not vacuum-sealed and were exposed to an environment with a relative humidity of 50% for 4 hours; tin granules (0.2000g) were used as the flux; the graphite crucible was not pre-treated by dry firing; and the detection power was set to 2.5KW. All other conditions were the same as in Example 1.

[0029] Test results: The RSD of 7 repeated measurements was 9.47%. The sample melt surface was rough, with some areas showing a grainy texture, and the peak shapes were inconsistent. This indicates that without hydrogen absorption prevention and crucible dry-firing treatment, the test repeatability was poor and the melting effect was unsatisfactory.

[0030] Example 2 Following the steps of Example 1, with other conditions fixed, only the analysis power was changed during the experiment. The results are shown in Table 2.

[0031] Table 2. Results of hydrogen content detection in titanium alloys at different analytical powers. As shown in Table 1, the melt state and peak shape are optimal when the power is 2.7KW. Although the RSD (11.14%) is not the lowest, it is determined to be the optimal power based on melt integrity, peak shape stability and actual release efficiency.

[0032] Example 3 Following the steps in Example 1, the same titanium alloy sample was tested using both air-fired and non-air-fired graphite crucibles, and the results are shown in Table 2.

[0033] Table 2 Comparison of crucible firing results (both empty and not empty) The results show that the crucibles that have undergone air-firing treatment have more stable test results, significantly reduced RSD, and the measured values ​​are closer to the true values ​​(the results of crucibles that have not undergone air-firing treatment are generally higher, indicating that additional hydrogen interference has been introduced).

[0034] Example 4 Following the steps in Example 1, the treated titanium alloy samples from the same batch were exposed to environments with relative humidity of 50% and 24% for the same period of time before being tested. The results are shown in Table 3.

[0035] Table 3. The Influence of Different Humidity Environments on the Test Results The results show that a low humidity environment (≤24%) is a key condition for ensuring accurate and stable test results and can effectively inhibit hydrogen absorption by titanium alloys.

[0036] Example 5 The same titanium alloy sample was tested using the method of this invention on two different models of oxygen, nitrogen and hydrogen analyzers, namely ONH-3000 and ONH-5500. The results are shown in Table 4.

[0037] Table 4 Comparison Test Results of Different Instruments The results show that the method of the present invention can achieve good consistency on different models of instruments, and the repeatability meets the requirements of the national standard GB / T 4698.15-2011 (the repeatability is 0.0005% when the hydrogen mass fraction is 0.0027%), indicating that the method has strong versatility.

[0038] As can be seen from the above embodiments and comparative examples, the present invention significantly improves the accuracy and repeatability of hydrogen content detection in titanium alloys through the synergistic effect of multiple technical measures, such as "low humidity environment + vacuum sealing" to prevent hydrogen absorption during sample preparation, tin sheet as a flux, graphite crucible for dry burning pretreatment, and optimal analytical power of 2.7KW. The sample is completely melted, and the RSD of the detection result can be stably controlled within 3%, which is superior to existing technical methods.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention, based on the technical essence of the present invention, shall fall within the protection scope of the present invention.

Claims

1. A method for hydrogen content detection in titanium alloys, characterized in that, Includes the following steps: Sample preparation and hydrogen absorption prevention treatment: The titanium alloy sample is processed into a block shape, cleaned with organic solvent, and then naturally dried in an environment with a relative humidity of ≤24%. The test is completed within 4 hours or it is vacuum sealed and stored. Crucible pretreatment: Before testing, the graphite crucible is subjected to dry firing to remove residual hydrogen, water vapor and organic matter; Co-solvent preparation: Tin sheet was selected as the co-solvent, and the mass ratio of the tin sheet to the sample was 1:2; Detection parameter settings: The inert gas melting thermal conductivity method is adopted, with the analysis power set at 2.7 KW, the degassing power at 4.5 KW, the analysis time at 120 seconds, and the cooling water temperature at ≤28℃. Testing steps: Place the tin sheet at the bottom of the graphite crucible after it has been calcined in the air, add the sample, and then send it into the testing instrument to detect the hydrogen content according to the set parameters.

2. The method according to claim 1, characterized in that, The samples are processed into blocks, with a single sample mass of 0.1000 g to 0.3000 g and an accuracy of ±0.0001 g. Grinding is prohibited.

3. The method according to claim 1, characterized in that, The organic solvent cleaning involves ultrasonic cleaning with acetone 1-2 times, each time for 5-10 minutes.

4. The method according to claim 1, characterized in that, The vacuum seal is maintained at a vacuum level of ≤10 Pa, or sealed after argon gas purging.

5. The method according to claim 1, characterized in that, The aforementioned dry-burning process refers to performing at least one dry-burning operation on a high-purity graphite crucible at a degassing power of 4.5 kW until the instrument's hydrogen signal baseline stabilizes.

6. The method according to claim 1, characterized in that, The testing instrument is the ONH-3000 or ONH-5500 oxygen, nitrogen, and hydrogen analyzer or an inert gas melting analyzer of the same type as the Steel Research Institute NAK.

7. The method according to claim 1, characterized in that, Before conducting sample testing, the instrument is calibrated using titanium alloy standard materials to establish a working curve or perform single-point calibration.

8. The method according to claim 1, characterized in that, When the ambient humidity exceeds 24%, the sample processing and loading process shall be carried out in a glove box or dehumidified environment with a humidity of ≤10%.

9. The method according to claim 1, characterized in that, The mass ratio of the tin sheet to the sample is precisely controlled at 1:2, and when the sample mass is 0.18~0.23g, the tin sheet mass is 0.36~0.46g.

10. The method according to any one of claims 1 to 9, characterized in that, The method is applicable to the quality control and detection of hydrogen content in titanium alloy raw materials, semi-finished products, finished products, and special steel production processes.

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