High-temperature electrochemical hydrogen charging method suitable for 316L stainless steel

Abstract

The invention belongs to the technical field of hydrogen behavior tests in metal materials, and particularly relates to a high-temperature electrochemical hydrogen charging method suitable for 316L stainless steel. The method provided by the invention is scientific and reasonable in design, and is a high-temperature electrochemical hydrogen charging method taking the mixed molten salt of NaHSO4.H2O and KHSO4 in a mass ratio of 1: 1 as the electrolyte. Compared with normal-temperature electrochemical hydrogen charging which takes H2SO4 as an electrolyte and high-temperature and high-pressure hydrogen charging which is carried out in a hydrogen environment by utilizing a high-pressure kettle in the current 316L stainless steel hydrogen embrittlement research, the method disclosed by the invention not only improves the problem of low efficiency of normal-temperature electrochemical hydrogen charging, but also solves the safety problem of high-temperature and high-pressure electrochemical hydrogen charging; according to the method, high-concentration hydrogen can be introduced into the 316L stainless steel, so that the 316L stainless steel is obviously embrittled.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen behavior testing in metallic materials, and particularly relates to a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel. Background Art

[0002] Artificially introducing a high concentration of hydrogen into 316L stainless steel to cause embrittlement has the following main research values and application advantages: 1) Material property evaluation and screening: By accelerating the hydrogen permeation experiment, the hydrogen embrittlement resistance of materials in a high-pressure hydrogen storage environment or a corrosive medium can be quickly evaluated, providing an experimental basis for the material selection of high-pressure containers; comparing the effects of different welding processes (such as argon arc welding and electron beam welding) on hydrogen embrittlement sensitivity and optimizing the design of welding parameters. 2) Failure mechanism research: Revealing the influence of microstructural changes such as nickel-depleted layers at grain boundaries and carbide precipitation on the hydrogen diffusion path; verifying the correlation between stress gradient distribution and hydrogen concentration enrichment and establishing a stress-hydrogen synergistic action model. 3) Development of protection technologies: Through the analysis of embrittlement fracture surfaces, surface treatment processes (such as the preparation of passivation layers) can be specifically developed to reduce the hydrogen permeability; verifying the synergistic effect of an alkaline environment or chloride ion concentration on hydrogen embrittlement and providing data support for corrosion protection schemes; 4) Optimization of processing technologies: Simulating the hydrogen permeation effect introduced during processing such as electroplating and pickling to guide the formulation of dehydrogenation heat treatment processes.

[0003] In the prior art, there are mainly two methods to cause hydrogen embrittlement in 316L stainless steel.

[0004] First, it is room-temperature electrochemical hydrogen charging with H2SO4 as the electrolyte. This hydrogen charging method usually requires adding a certain concentration of poison in the sulfuric acid solution. The hydrogen charging is generally carried out at room temperature, and the hydrogen charging time is generally 24-96h, which results in low hydrogen charging efficiency and unobvious hydrogen charging effect. Hydrogen can only act on the surface layer of the material with a thickness of 10-20μm.

[0005] Second, it is high-temperature and high-pressure hydrogen charging using an autoclave in a hydrogen environment. This hydrogen charging method requires equipment capable of generating high-temperature and high-pressure conditions, such as a high-temperature and high-pressure autoclave. However, the commercially available high-temperature and high-pressure autoclaves cannot simultaneously reach a high temperature of 300°C and a high pressure of 20-30MPa, and using a high-temperature and high-pressure autoclave requires special high-pressure explosion-proof equipment, which cannot be achieved by most material research laboratories. Although this method can achieve an obvious hydrogen charging effect, there are relatively large potential safety hazards in the experiment.

[0006] In view of this, the inventor expects to design a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above problems existing in the traditional technology and provide a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel.

[0008] To achieve the above technical objectives and reach the above technical effects, the present invention is realized through the following technical solutions:

[0009] The present invention provides a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel, comprising the following steps:

[0010] S1. Put NaHSO4·H2O and KHSO4 into an electrolytic cell according to a ratio, and mix them evenly to obtain a mixed salt;

[0011] S2. Place the electrolytic cell containing the mixed salt stably on a closed electric furnace, and use the closed electric furnace to melt the mixed salt in the electrolytic cell. During the melting process of the mixed salt, continuously stir it with a glass rod to make the mixed salt heat evenly until the mixed salt is completely melted into a molten salt in a clear liquid state;

[0012] S3. Connect a platinum electrode to the positive pole of a DC power supply, fix a 316L stainless steel specimen with a platinum electrode clip and then connect it to the negative pole of the DC power supply. After connecting the DC power supply, first turn on the working switch of the DC power supply, and then put the specimen and the platinum electrode into the electrolytic cell containing the molten salt, adjust the distance between the 316L stainless steel specimen and the platinum electrode, and start hydrogen charging.

[0013] Further, in step S1, the mass ratio of NaHSO4·H2O to KHSO4 is 1:1.

[0014] Further, in step S2, the preset temperature of the closed electric furnace is 150°C.

[0015] Further, in step S3, the current density of the DC power supply is set to 20 mA / cm 2 .

[0016] Further, in step S3, the 316L stainless steel specimen is a standard tensile specimen, which consists of a middle section, a connecting section and a side section. The two sides of the middle section are respectively connected to the side section through the connecting section, and the thickness of the middle section is lower than that of the side section.

[0017] Further, the thickness of the middle section is 6 mm and the length is 32 mm; the thickness of the side section is 10 mm and the length is 30 mm; the total length of the 316L stainless steel specimen is 100 mm, the connecting section is in a rounded corner structure, and the radius R corresponding to the rounded corner is 6 mm.

[0018] Further, the 316L stainless steel specimen is polished with sandpaper before hydrogen charging to remove the oxide layer on the surface.

[0019] Further, in step S3, control the distance between the 316L stainless steel specimen and the platinum electrode to be 5 - 6 cm.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention provides a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel, which is a high-temperature electrochemical hydrogen charging method using a mixed molten salt of NaHSO4·H2O and KHSO4 with a mass ratio of 1:1 as the electrolyte. Compared with the conventional room-temperature electrochemical hydrogen charging using H2SO4 as the electrolyte and the high-temperature and high-pressure hydrogen charging using an autoclave in a hydrogen environment in the current hydrogen embrittlement research of 316L stainless steel, the method of the present invention not only improves the slow efficiency of room-temperature electrochemical hydrogen charging but also solves the safety problem of high-temperature and high-pressure electrochemical hydrogen charging; by using the method of the present invention, a high concentration of hydrogen can be introduced into 316L stainless steel, thereby causing obvious embrittlement of 316L stainless steel.

[0022] Of course, it is not necessary for any product implementing the present invention to achieve all the above advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0024] Figure 1 It is a flowchart of the high-temperature electrochemical hydrogen charging method of the present invention;

[0025] Figure 2 It is a schematic diagram of the experimental device in the present invention;

[0026] Figure 3 It is a physical diagram of the experimental device in the present invention;

[0027] Figure 4 It is a schematic diagram of the size of the 316L stainless steel specimen in the present invention;

[0028] In the drawings, the reference numerals of each component are as follows:

[0029] 1 - DC power supply, 2 - closed electric furnace, 3 - thermocouple, 4 - platinum electrode, 5 - 316L stainless steel specimen, 6 - molten salt. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] The experimental device adopted in this embodiment is as shown in Figure 2 and Figure 3 and mainly consists of a DC power supply 1, a closed electric furnace 2, a thermocouple 3 and a platinum electrode 4. The thermocouple 3 is used to monitor the temperature of the mixed salt or molten salt in real time.

[0032] This embodiment provides a high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel, including the following steps:

[0033] S1. Put NaHSO4·H2O and KHSO4 into the electrolytic cell according to a mass ratio of 1:1, and mix them evenly to obtain a mixed salt. The electrolytic cell is selected as a 250 mL beaker, and the volume of the mixed salt is 200 mL.

[0034] S2. Place the electrolytic cell containing the mixed salt stably on the closed electric furnace 2. The preset temperature of the closed electric furnace 2 is 150 °C. Use the closed electric furnace 2 to melt the mixed salt in the electrolytic cell. During the melting process of the mixed salt, continuously stir with a glass rod to make the mixed salt heat evenly until the mixed salt is completely melted into a clear liquid state of molten salt 6.

[0035] S3. Connect the platinum electrode to the positive pole of the DC power supply, fix the 316L stainless steel specimen 5 with a platinum electrode clamp and then connect it to the negative pole of the DC power supply. The current density of the DC power supply is set to 20 mA / cm 2 . After connecting the DC power supply, first turn on the working switch of the DC power supply, and then put the specimen and the platinum electrode into the electrolytic cell containing the molten salt. Control the distance between the 316L stainless steel specimen 5 and the platinum electrode to be 5.5 cm, and start hydrogen charging.

[0036] In this embodiment, the 316L stainless steel specimen 5 is a standard tensile specimen, which consists of a middle section, a connecting section and a side section. The two sides of the middle section are respectively connected to the side section through the connecting section, and the thickness of the middle section is lower than that of the side section. As shown in Figure 4 , the thickness of the middle section is 6 mm and the length is 32 mm; the thickness of the side section is 10 mm and the length is 30 mm; the total length of the 316L stainless steel specimen 5 is 100 mm, the connecting section has a rounded corner structure, and the radius R corresponding to the rounded corner is 6 mm.

[0037] In this embodiment, the 316L stainless steel specimen 5 is polished with 2000-mesh sandpaper before hydrogen charging to remove the oxide layer on the surface.

[0038] Set three experimental groups and one control group without hydrogen charging treatment. Each group of specimens is polished with 2000-mesh sandpaper to remove the oxide layer on the surface. The hydrogen charging times are 8 h, 12 h, and 16 h respectively, and each group conducts the above hydrogen charging operation three times. After hydrogen charging, a slow strain tensile test is carried out on each group of specimens, and the tensile rate is 2.5×10-4 s -1 After stretching, measure the elongation after fracture of each group. The degree of hydrogen embrittlement is evaluated by the following formula.

[0039] IHE(δ) = (1 - δ H / δ0) × 100%

[0040] The higher the IHE(δ), the greater the degree of hydrogen embrittlement. When IHE(δ) > 50%, it is extremely severe hydrogen damage; when IHE(δ) > 25%, it is severe hydrogen damage; when IHE(δ) > 10%, hydrogen damage occurs; when IHE(δ) < 10%, it is low hydrogen damage.

[0041] The average elongation of the control group was 28.9%, the average elongation of the experimental group charged with hydrogen for 8 h was 13.9%, the average elongation of the experimental group charged with hydrogen for 12 h was 13.8%, and the average elongation of the experimental group charged with hydrogen for 16 h was 8.8%. Their IHE(δ) values were 51.9%, 52.2%, and 69.6% respectively. The average elongation of each experimental group decreased significantly. Extreme hydrogen damage occurred in the experimental groups charged with hydrogen for 8 h, 12 h, and 16 h. It can be seen that the method of this embodiment has a significant hydrogen charging effect on 316L stainless steel.

[0042] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel, characterized in that, It includes the following steps: S1. Put NaHSO4·H2O and KHSO4 into the electrolytic cell according to the ratio, and mix them evenly to obtain a mixed salt; S2. Place the electrolytic cell containing the mixed salt stably on a closed electric furnace, and use the closed electric furnace to melt the mixed salt in the electrolytic cell. During the melting process of the mixed salt, continuously stir it with a glass rod to make the mixed salt heated evenly until the mixed salt is completely melted into a molten salt in a clear liquid state; S3. Connect the platinum electrode to the positive pole of the DC power supply, fix the 316L stainless steel specimen with a platinum electrode clamp and then connect it to the negative pole of the DC power supply. After connecting the DC power supply, first turn on the working switch of the DC power supply, and then put the specimen and the platinum electrode into the electrolytic cell containing the molten salt, adjust the distance between the 316L stainless steel specimen and the platinum electrode, and start hydrogen charging.

2. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 1, wherein In step S1, the mass ratio of NaHSO4·H2O to KHSO4 is 1:

1.

3. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 1, characterized in that, In step S2, the preset temperature of the closed electric furnace is 150°C.

4. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 1, characterized in that, In step S3, the current density of the DC power supply is set to 20 mA / cm 2 .

5. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 1, wherein In step S3, the 316L stainless steel specimen is a standard tensile specimen, which consists of a middle section, a connecting section and a side section. The two sides of the middle section are respectively connected to the side section through the connecting section, and the thickness of the middle section is lower than that of the side section.

6. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 5, characterized in that, The thickness of the middle section is 6 mm and the length is 32 mm; the thickness of the side section is 10 mm and the length is 30 mm; the total length of the 316L stainless steel specimen is 100 mm, the connecting section has a rounded corner structure, and the radius R corresponding to the rounded corner is 6 mm.

7. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 5, characterized in that The 316L stainless steel specimen is polished with sandpaper before hydrogen charging to remove the oxide layer on the surface.

8. The high-temperature electrochemical hydrogen charging method applicable to 316L stainless steel according to claim 1, characterized in that, In step S3, control the distance between the 316L stainless steel specimen and the platinum electrode to be 5 - 6 cm.

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