A general method for studying the corrosion behavior of structural materials in lead-bismuth alloy melts

Abstract

The present invention provides a general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt, which is characterized in that: the present invention first uses the structural material to be studied to process a hollow tube and a matching pin, seals the lead-bismuth alloy sample in the hollow tube, and welds the hollow tube and the pin together, then puts the welded sample into a quartz tube and evacuates the tube, and the obtained sample can be used to study the corrosion behavior of the structural material in the lead-bismuth alloy melt at a set temperature. The present invention can also obtain the result of the weld zone's resistance to corrosion of the lead-bismuth alloy melt, which provides a powerful means for studying the corrosion mechanism and law of the off-core structural material in the cooling system.

Description

Technical Field

[0001] The invention relates to the field of nuclear engineering corrosion experiment design, and in particular provides a general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt. Background Art

[0002] Compared with traditional energy, nuclear energy has the characteristics of high efficiency and cleanliness. When traditional fossil fuels are exhausted, nuclear energy will surely be the backbone of energy for all mankind. So far, nuclear reactor technology has developed from the first generation of low-efficiency prototype test reactor technology to the fourth generation of new nuclear energy systems. Liquid lead-bismuth alloy is recognized as an ideal material for coolant of nuclear accelerator driven subcritical system due to its excellent neutronic properties, chemical inertness, low melting point, high boiling point and good thermal conductivity. However, the corrosion problem of structural materials in lead-bismuth alloy melt is a key problem to be solved in the design and development of this type of reactor. At present, many scholars have developed a variety of nuclear reactor coolant main pipeline structural materials (such as 321, 410 and 430 stainless steel, etc.) for off-pile dynamic simulation corrosion tests, in order to find the corrosion law of structural materials in lead-bismuth alloy melt. In the prior art, the structural material and lead-bismuth alloy are sealed in a quartz tube, and then treated for a long time at a specific temperature to obtain the corrosion law. However, due to the low melting point of lead-bismuth alloy, there is a large volume change during heating and cooling, which makes the coated quartz tube easy to crack. Therefore, researchers are eager to find a universal method to study the corrosion behavior of structural materials in lead-bismuth alloy melts. Summary of the invention

[0003] In view of the shortcomings of the prior art and the urgent needs of the academic community, the present invention provides a general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt. The method has the characteristics of easy operation, low cost and significant effect. The method of the present invention can also obtain the results of the resistance of the weld zone to the corrosion of the lead-bismuth alloy melt, which provides a powerful means for studying the corrosion mechanism and law of the ex-core structural materials in the cooling system.

[0004] The present invention achieves the above object through the following technical solutions:

[0005] A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt, the method comprising the following steps:

[0006] (1) The structural material to be studied is processed into a hollow tube with one end closed (referred to as the hollow tube) and a matching pin. For a specific structural diagram, see Figure 1 and Figure 2 ;

[0007] (2) preparing lead-bismuth alloy samples;

[0008] (3) placing the lead-bismuth alloy sample obtained in step (2) into the hollow tube of step (1), inserting a pin into the hollow tube, and then welding the hollow tube and the pin together with solder, ensuring the integrity and airtightness of the weld;

[0009] (4) sealing the welded hollow tube obtained in step (3) into a quartz tube, and evacuating the quartz tube;

[0010] (5) The sample obtained in step (4) can be used for corrosion behavior research at a specific temperature.

[0011] As the preferred technical solution:

[0012] In step (1), the roughness of the inner and outer surfaces of the hollow tube is ensured to be below 0.5 μm.

[0013] The preparation method of the lead-bismuth alloy sample in step (2) is: pure lead and pure bismuth particles are mixed according to a ratio, and then the mixed materials are sealed in a quartz tube, and the quartz tube is vacuum sealed, heated to above the melting point in an atmosphere furnace at a rate of less than 1°C / min and kept warm for 0.5-1h, and then cooled to room temperature at a rate of less than 1°C / min. The specific heat treatment process is detailed in Figure 3 Finally, the impurity-rich end of the lead-bismuth alloy is cut off to obtain the purified lead-bismuth alloy sample. Since most of the current lead-bismuth alloy cooling systems use lead-bismuth eutectic alloy, the lead-bismuth eutectic alloy is generally prepared (the mass fractions of lead and bismuth are 44.5% and 55.5%, respectively, and the melting point of the alloy is 127°C), but the method of the present invention is not limited to the lead-bismuth alloy of this proportion; during the vacuum sealing treatment, the vacuum degree is kept at 10 -3 Below Pa.

[0014] Step (4) vacuum treatment is performed so that the vacuum degree is 10 -3 Below Pa.

[0015] The temperature of the corrosion test in step (5) is generally 500-550°C, and the specific temperature can also be set according to the actual temperature outside the pile.

[0016] The volume of the hollow tube of the present invention is 2-3 times the volume of the lead-bismuth alloy sample.

[0017] The optimal size of the hollow tube of the present invention is: outer diameter Φ = 15mm, inner diameter The outer cylinder has a height of H = 45 mm and a depth of h = 40 mm. The size of the hollow tube can also be set according to specific experimental requirements.

[0018] The gap between the tube wall of the hollow tube of the present invention and the lead-bismuth alloy sample is preferably 0.5-1 mm; the gap between the tube wall of the hollow tube and the tube wall of the quartz tube is preferably 1-2 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a structural material processed into a hollow tube with one end closed;

[0020] Figure 2 Schematic diagram of the pins supporting the hollow tube;

[0021] Figure 3 Purification heat treatment process of lead-bismuth alloy;

[0022] Figure 4 Schematic diagram of the apparatus used to study the corrosion behavior of structural materials in lead-bismuth alloy melt;

[0023] Figure 5 The purification heat treatment process of the lead-bismuth alloy eutectic alloy in Example 1.

[0024] Figure numerals: 1. hollow tube, 2. pin, 3. weld, 4. lead-bismuth alloy sample, 5. quartz tube. DETAILED DESCRIPTION

[0025] The present invention is explained in detail with reference to the following specific examples.

[0026] Example 1

[0027] The corrosion behavior of Ti-6Al-4V alloy in lead-bismuth eutectic alloy melt at 550°C was studied. The specific implementation steps are as follows:

[0028] (1) Use machining to process Ti-6Al-4V rods into hollow tubes and matching pins. For a detailed schematic diagram, see Figure 1 and Figure 2 , the outer diameter of the hollow tube is Φ = 15mm, the inner diameter The outer cylinder height H = 45mm, depth h = 40mm, and the roughness of the inner and outer surfaces of the hollow tube is guaranteed to be below 0.5μm;

[0029] (2) Preparation and preliminary purification of lead-bismuth alloy. Pure lead and pure bismuth particles were prepared into a lead-bismuth eutectic alloy, in which the mass fractions of lead and bismuth were 44.5% and 55.5%, respectively. The melting point of the alloy was 127°C. The prepared materials were then sealed in a quartz tube (the volume of the hollow tube was twice the volume of the lead-bismuth alloy sample) and the quartz tube was vacuum sealed (the vacuum degree was less than 10 -3 Pa), heated to 300℃ in an atmosphere furnace at a rate of 0.5℃ / min and kept at that temperature for 1h, then cooled to room temperature at a rate of 0.5℃ / min. For details of the heat treatment process, see Figure 5 Finally, the impurity-rich end of the lead-bismuth alloy is cut off to obtain the purified lead-bismuth eutectic alloy;

[0030] (3) placing the purified lead-bismuth eutectic alloy obtained in step (2) into the hollow tube obtained in step (1), inserting the pin in step (1) into the hollow tube, and finally welding the hollow tube and the pin together with solder to ensure the integrity and airtightness of the weld;

[0031] (4) sealing the welded hollow tube obtained in step (4) into a quartz tube, and evacuating the quartz tube to make the space between the hollow tube and the quartz tube a vacuum environment with a vacuum degree of less than 10 -3 Pa, the schematic diagram of the entire device is shown in Figure 4 ;

[0032] (5) The samples obtained in step (5) can be used for the study of corrosion behavior at 550°C. Specifically, a long-term (generally greater than 1000 h) heat preservation treatment is carried out at 550°C to explore whether the structural material is corroded by the lead-bismuth alloy melt at high temperature. If it is corroded, what is the corrosion rate, and a specific corrosion kinetic curve can be obtained to provide guidance for practice.

[0033] Matters not covered by the invention are known technologies.

[0034] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt, characterized in that: The following steps are involved: (1) Process the structural material to be studied into a hollow tube with one end closed and a matching pin; (2) preparing lead-bismuth alloy samples; (3) placing the lead-bismuth alloy sample obtained in step (2) into the hollow tube obtained in step (1), inserting a pin into the hollow tube, and then welding the hollow tube and the pin together with solder; (4) sealing the welded hollow tube obtained in step (3) into a quartz tube, and evacuating the quartz tube; (5) The sample obtained in step (4) can be used for corrosion behavior research at a specific temperature; The preparation method of the lead-bismuth alloy sample in step (2) is as follows: pure lead and pure bismuth particles are mixed according to a ratio, and then the mixed materials are sealed in a quartz tube, and the quartz tube is vacuum-sealed, and heated to above the melting point at a rate of less than 1°C / min in an atmosphere furnace and kept warm for 0.5-1h, and then cooled to room temperature at a rate of less than 1°C / min, and finally the impurity-enriched end of the lead-bismuth alloy is cut off to obtain the purified lead-bismuth alloy sample; Step (2) preparing a lead-bismuth eutectic alloy sample, wherein the mass fractions of lead and bismuth are 44.5% and 55.5% respectively, and the melting point of the alloy is 127° C.; during the vacuum sealing treatment, the vacuum degree is kept at 10 -3 Below Pa.

2. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt according to claim 1, characterized in that: In step (1), the roughness of the inner and outer surfaces of the hollow tube is ensured to be below 0.5 μm.

3. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt according to claim 1, characterized in that: Step (4) vacuum treatment is performed so that the vacuum degree is 10 -3 Below Pa.

4. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt according to claim 1, characterized in that: The temperature of the corrosion test in step (5) is 500-550°C.

5. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt according to claim 1, characterized in that: The volume of the hollow tube is 2-3 times the volume of the lead-bismuth alloy sample.

6. A general method for studying the corrosion behavior of structural materials in a lead-bismuth alloy melt according to claim 1 or 5, characterized in that: The outer diameter of the hollow tube is Φ=15mm, the inner diameter is φ=11, the outer cylinder height is H=45mm, and the depth is h=40mm.

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