Method for manufacturing a stainless steel sintered mesh

Abstract

This invention provides a method for manufacturing a stainless steel sintered mesh. The method includes: a step of preparing a screen comprising a plurality of metal wires made of austenitic stainless steel extending in intersecting directions; and a heat treatment step of controlling the atmosphere temperature of the screen. The heat treatment step includes: a heating step of raising the atmosphere temperature to a treatment temperature; a holding step of maintaining the atmosphere temperature at the treatment temperature; and a cooling step of lowering the atmosphere temperature. The treatment temperature is above the austenitizing temperature. The cooling step includes a rapid cooling step of lowering the atmosphere temperature at a rate of 3°C / min or higher under an argon atmosphere.

Description

Technical Field

[0001] This invention relates to a method for manufacturing stainless steel sintered mesh. Background Technology

[0002] Filters for removing foreign matter contained in hydrogen fuel are known to the public. For example, Patent Document 1 discloses the use of a stainless steel mesh as a filter. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Publication No. 2017-64699 Summary of the Invention

[0004] If a stainless steel screen is used as a filter in the acidic environment of a hydrogen fuel cell, the screen may corrode.

[0005] The purpose of this invention is to provide a method for manufacturing stainless steel sintered mesh that can effectively solve this problem.

[0006] The method for manufacturing the sintered mesh of the present invention includes: The process of preparing a screen comprising multiple metal wires made of austenitic stainless steel and extending in intersecting directions; and A heat treatment process that controls the temperature of the atmosphere around the screen. The heat treatment process includes: a heating process to raise the temperature of the atmosphere to a treatment temperature; a holding process to maintain the temperature of the atmosphere at the treatment temperature; and a cooling process to lower the temperature of the atmosphere. The processing temperature is above the austenitizing temperature. The cooling process includes a rapid cooling process in which the temperature of the atmosphere decreases at a rate of 3°C / minute or higher under an argon atmosphere.

[0007] In the holding step of the manufacturing method of the sintered mesh of the present invention, the pressure of the atmosphere is lower than atmospheric pressure.

[0008] In the cooling process of the sintered mesh manufacturing method of the present invention, the pressure of the argon gas is higher than the atmospheric pressure.

[0009] In the manufacturing method of the sintered mesh of the present invention, the processing temperature is above 980°C and below 1100°C.

[0010] In the method for manufacturing the sintered mesh of the present invention, the sintered mesh is used as a filter for hydrogen fuel.

[0011] According to the present invention, corrosion of sintered mesh can be suppressed. Attached Figure Description

[0012] Figure 1 This is a perspective view showing an example of a filter device. Figure 2 This is a perspective view showing an example of a screen filter. Figure 3 This is a top view showing an example of sintered mesh 20. Figure 4 This indicates observation from direction AA. Figure 3 A cross-sectional view of the sintered mesh 20. Figure 5 This is a diagram illustrating an example of a heat treatment process. Figure 6 This is another example of a heat treatment process. Figure 7 This is a diagram showing a roller containing a screen. Figure 8 This is a diagram illustrating an example of a heat treatment method. Figure 9 This is a diagram illustrating an example of the arrangement of rollers in a heat treatment process. Figure 10 This is a diagram used to illustrate the immersion test. Figure 11 This is a diagram used to illustrate the etching test. Figure 12 This is a graph showing the observation results of the sample from Example 1. Figure 13 This is a graph showing the observation results of the sample in Example 2. Figure 14 This is a graph showing the observation results of the sample in Example 3. Figure 15 This is a graph showing the observation results of the sample in Example 4. Figure 16 This is a graph showing the observation results of the sample in Example 5. Figure 17 This is a graph showing the observation results of the sample in Comparative Example 1. Figure 18 This is a graph showing the observation results of the sample in Comparative Example 2. Detailed Implementation

[0013] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. Furthermore, in the drawings accompanying this specification, for ease of understanding, the scale and aspect ratios have been exaggerated from the actual scale and aspect ratios of the objects.

[0014] (Filter device) Figure 1This is a perspective view showing an example of filter device 1. Filter device 1 is used, for example, as a filter for hydrogen fuel. Filter device 1 is used, for example, in the FC (Fuel Cell) stack of a hydrogen fuel cell vehicle.

[0015] The filter device 1 includes a screen filter 10 and a housing 2 that holds the screen filter 10. The housing 2 is made of, for example, resin.

[0016] Figure 2 This is a perspective view showing an example of a screen filter 10. The screen filter 10 may also include cylindrical sides and a bottom surface. The sides of the screen filter 10 are formed by sintered mesh 20.

[0017] The hydrogen fuel is, for example, compressed hydrogen gas. The hydrogen fuel flows into the interior of the screen filter 10 through the sintered mesh 20. As the hydrogen fuel passes through the sintered mesh 20, foreign matter in the hydrogen fuel is captured. The hydrogen fuel flows out from the bottom surface of the screen filter 10.

[0018] (Sintered mesh) Figure 3 This is a top view showing an example of a sintered mesh 20. The sintered mesh 20 includes: a plurality of first metal wires 21 extending along a first direction D1; and a plurality of second metal wires 22 extending along a second direction D2 intersecting the first direction D1. The first direction D1 may also be orthogonal to the second direction D2.

[0019] Figure 4 This indicates observation from direction AA. Figure 3 A cross-sectional view of the sintered mesh 20. (See diagram below.) Figure 4 As shown, the first metal wire 21 and the second metal wire 22 have circular cross-sections.

[0020] The first metal wire 21 and the second metal wire 22 are in Figure 4 The bonding is achieved through sintering in the vertical direction. Sintering is achieved by heat-treating a screen containing the first metal wire 21 and the second metal wire 22. The sintering-based bonding can be achieved with the first metal wire 21 above the second metal wire 22, as shown by reference numeral 23, or with the second metal wire 22 above the first metal wire 21, as shown by reference numeral 24.

[0021] like Figure 3 As shown, the first metal wire 21 and the second metal wire 22 can also be combined in a manner where the first contact point 23 and the second contact point 24 are alternately arranged in the first direction D1 and the second direction D2. Furthermore, the positional relationship between the first metal wire 21 and the second metal wire 22 is not limited to... Figure 3 and Figure 4 Examples.

[0022] The sintered mesh 20 includes a gap 25 surrounded by two first metal wires 21 and two second metal wires 22. When the sintered mesh 20 is used as a filter for hydrogen fuel, foreign objects with a size larger than the gap 25 are captured through the sintered mesh 20.

[0023] Reference numerals S1 and S2 denote the widths of the first metal wire 21 and the second metal wire 22, respectively. Reference numeral S3 denotes the spacing between two adjacent first metal wires 21. Reference numeral S4 denotes the spacing between two adjacent second metal wires 22. The widths S1 and S2 and the spacings S3 and S4 are determined according to the size of the foreign object to be captured. Preferably, the sintered mesh 20 is capable of capturing foreign objects with a size of 200 μm or larger.

[0024] Widths S1 and S2 can be 30μm or more, or 50μm or more, or 100μm or more. Widths S1 and S2 can be less than 500μm, or less than 300μm, or less than 200μm.

[0025] The spacing between S3 and S4 can be 50 μm or more, or 100 μm or more, or 150 μm or more. The spacing between S3 and S4 can be 500 μm or less, or 300 μm or less, or 200 μm or less.

[0026] The sintered mesh 20 is made of austenitic stainless steel. Austenitic stainless steel contains less than 0.08 wt% carbon (C), less than 1.00 wt% silicon (Si), less than 2.00 wt% manganese (Mn), less than 0.045 wt% phosphorus (P), less than 0.030 wt% sulfur (S), more than 8.00 wt% and less than 15.00 wt% nickel (Ni), more than 16.00 wt% and less than 20.00 wt% chromium (Cr), less than 3.00 wt% molybdenum (Mo), the remainder being iron (Fe), and unavoidable impurities. SUS304, SUS316, SUS316L, etc., can be used as austenitic stainless steel. Examples of the composition of SUS304, SUS316, and SUS316L are shown in Table 1. The values ​​in Table 1 are in weight percent. (Table 1)

[0027] Stainless steel is known to the public as a material that is resistant to corrosion. However, the inventors discovered that sintered mesh 20, when used as a filter for hydrogen fuel, can corrode under inappropriate heat treatment conditions. Specifically, it was found that sintered mesh 20 is prone to corrosion when heat-treated under a nitrogen atmosphere.

[0028] One of the reasons for corrosion of sintered mesh 20 can be considered as follows. During heat treatment, the sintered mesh 20 is held at a processing temperature above the austenitizing temperature for a certain period of time. When the atmosphere temperature is raised from room temperature to the processing temperature, or when the atmosphere temperature is lowered from the processing temperature to room temperature, the sintered mesh 20 is exposed to an atmosphere at which nitrides or carbides easily precipitate. Therefore, in the case of an atmosphere containing nitrogen, chromium nitrides are sometimes formed at grain boundaries due to nitrogen atoms penetrating into the interior of the sintered mesh 20. If chromium nitrides are formed, the chromium concentration in the austenite structure surrounding the chromium nitrides decreases. If the chromium concentration decreases, the resistance to corrosion decreases. As a result, the sintered mesh 20 used as a filter in the acidic environment of hydrogen fuel cells sometimes corrodes. In the following description, the austenite structure with a reduced chromium concentration is also referred to as a chromium-deficient layer. Furthermore, the above reason is merely one example. Even if the sintered mesh 20 corrodes for other reasons, the significance of this invention will not be lost.

[0029] When the sintered mesh 20 is used as a filter for hydrogen fuel, it is required to capture fine foreign matter. Therefore, the widths S1 and S2 of the first metal wire 21 and the second metal wire 22 constituting the sintered mesh 20 become smaller. The smaller the widths S1 and S2, the higher the ratio of the surface area of ​​the metal wires 21 and 22 to their volume. Therefore, a chromium-deficient layer is more likely to form during heat treatment.

[0030] To address this problem, a heat treatment method using an argon atmosphere is proposed in this invention. The manufacturing method of the sintered mesh 20 will be described below.

[0031] (Manufacturing method of sintered mesh) First, prepare a screen comprising a first metal wire 21 and a second metal wire 22. The first metal wire 21 and the second metal wire 22 may be bonded together by sintering or other means, or they may not be bonded together.

[0032] Next, a heat treatment process is performed to control the atmosphere temperature of the screen. For example, the atmosphere temperature of the furnace is controlled while the screen is placed in the furnace. The shape of the screen during the heat treatment process is arbitrary. For example, the screen sheet can be rolled into a roller and the roller can be heat treated.

[0033] Figure 5 This is a diagram illustrating an example of a heat treatment process. Figure 5 The horizontal axis represents time, the left vertical axis represents the temperature of the atmosphere, and the right vertical axis represents the pressure of the atmosphere. When the atmosphere is replaced by argon, the pressure of the atmosphere is the same as the pressure of the argon. The heat treatment process includes a heating step S10, a holding step S20, and a cooling step S30. Each step is described below.

[0034] The heating process S10 raises the atmosphere temperature from room temperature to the treatment temperature T2. Treatment temperature T2 is above the austenitizing temperature. At treatment temperature T2, the austenitic structure of the austenitic stainless steel can exist stably. Treatment temperature T2 is, for example, 980°C or higher, or 1020°C or higher. Treatment temperature T2 is, for example, 1100°C or lower, or 1060°C or lower.

[0035] Within a certain temperature range, such as above 500°C and below 800°C, chromium nitrides or carbides readily precipitate in austenitic stainless steels. This temperature range where nitrides or carbides readily precipitate is also called the precipitation temperature range. The lower limit of this precipitation temperature range is also called the precipitation temperature T1. For example, precipitation temperature T1 might be 500°C.

[0036] The heating step S10 may also include a rapid heating step S15 in which the atmosphere temperature is increased at a heating rate H1 of 5°C / min or higher. This allows for rapid passage through the precipitation temperature range. Therefore, the formation of chromium nitrides or carbides on the screen during the heating step S10 can be suppressed. The heating rate H1 is calculated by dividing the difference between the processing temperature T2 and the precipitation temperature T1 by the time required for the atmosphere temperature to rise from the precipitation temperature T1 to the processing temperature T2. The heating rate H1 can be 10°C / min or higher, or 20°C / min or higher.

[0037] The heating process S10 is carried out in an atmosphere of argon gas with a first pressure P1. The first pressure P1 can be, for example, 10 Pa or more, or 50 Pa or more. The first pressure P1 can be, for example, 1 kPa or less, or 300 Pa or less.

[0038] In the holding process S20, the atmosphere temperature is maintained at the processing temperature T2 for a certain period of time. At the processing temperature T2, elements such as chromium, nickel, carbon, and nitrogen dissolve in the austenite structure. Therefore, even if chromium nitrides or carbides are formed on the screen, the holding process S20 can cause the constituent elements of the nitrides or carbides to dissolve in the austenite structure. This suppresses the presence of a chromium-deficient layer on the screen.

[0039] The atmosphere temperature is maintained at the processing temperature T2 for a time of, for example, 30 minutes or more, or even 45 minutes or more. By setting the holding time to 30 minutes or more, elements such as chromium, nickel, carbon, and nitrogen can be dissolved in the austenitic structure. The holding time is, for example, 90 minutes or less, or even 60 minutes or less. By setting the holding time to 90 minutes or less, sintering of the sheets of the screen wound into a roll shape can be prevented.

[0040] Process S20 is carried out in an argon atmosphere with a second pressure P2. The second pressure P2 can be, for example, 10 Pa or more, or 50 Pa or more. The second pressure P2 is lower than atmospheric pressure. The second pressure P2 can be, for example, 1 kPa or less, or 300 Pa or less.

[0041] The cooling step S30 lowers the atmosphere temperature from the processing temperature T2 to room temperature. The cooling step S30 may also include a quenching step S35 that lowers the atmosphere temperature at a rate C1 of 3°C / min or higher. This allows for rapid passage through the precipitation temperature range. Therefore, the formation of chromium nitrides or carbides on the screen during the cooling step S30 can be suppressed. The cooling rate C1 is calculated by dividing the difference between the processing temperature T2 and the precipitation temperature T1 by the time required for the atmosphere temperature to drop from the processing temperature T2 to the precipitation temperature T1. The cooling rate C1 can be 5°C / min or higher, 10°C / min or higher, 20°C / min or higher, 50°C / min or higher, or 100°C / min or higher.

[0042] The cooling process S30 can also be carried out in an argon atmosphere with a third pressure P3. The third pressure P3 is higher than atmospheric pressure. For example, the third pressure P3 can be 110 kPa or higher, or 150 kPa or higher. For example, the third pressure P3 can be 600 kPa or lower, or 200 kPa or lower.

[0043] Figure 6 This is another diagram illustrating a heat treatment process. (For example...) Figure 6 As shown, the heating process S10 may also include a first heating process S11, a standby process S12, and a second heating process S13. The first heating process S11 raises the atmosphere temperature from room temperature to the standby temperature T4. The standby process S12 maintains the atmosphere temperature at the standby temperature T4 for a certain period of time. The second heating process S13 raises the atmosphere temperature from the standby temperature T4 to the processing temperature T2.

[0044] When multiple rollers are heat-treated simultaneously, their temperatures can sometimes differ depending on their positions. In such cases, the timing at which the rollers reach the treatment temperature T2 can sometimes deviate depending on their positions. By including a standby step S12 in the heating process S10, the deviation in the timing of the rollers reaching the treatment temperature T2 based on their positions can be suppressed. The standby temperature T4 is, for example, 500°C or higher and 900°C or lower.

[0045] According to this embodiment, by performing a cooling process under an argon atmosphere, the formation of chromium nitrides or carbides in the sintered mesh 20 can be suppressed. This suppresses the formation of a chromium-deficient layer in the sintered mesh 20. Therefore, corrosion of the sintered mesh 20 used as a filter in the acidic environment of a hydrogen fuel cell can be suppressed.

[0046] Furthermore, the application of the sintered mesh 20 is not limited to filters for hydrogen fuel cells. The sintered mesh 20 of this embodiment can also be used in other environments where corrosion is likely to occur. Example

[0047] The present invention will now be described in more detail through embodiments, but the present invention is not limited to the embodiments described below without departing from its spirit.

[0048] (Example 1) First, prepare a sheet of mesh comprising a first metal wire 21 and a second metal wire 22. The mesh sheet is 50 mm wide and 10 m long. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 are 50 μm. When the cross-sections of the first metal wire 21 and the second metal wire 22 are circular, the widths S1 and S2 are referred to as wire diameters. Next, as... Figure 7 As shown, the mesh sheet 26 is wound into a roller shape. SUS316L containing 0.01% by weight of carbon was used as the material for the mesh sheet 26.

[0049] Next, as Figure 8 As shown, a roller 30 with a mesh sheet 26 is disposed in the retainer 40. The retainer 40 includes a first retainer 41, a second retainer 42, a third retainer 43, and a fourth retainer 44 stacked sequentially from bottom to top. Twenty-five rollers 30 are disposed on each of the retainers 41 to 44.

[0050] Figure 9 This diagram shows the arrangement of rollers 30 in each of the retaining members 41 to 44. (See diagram below.) Figure 9 As shown, rollers 30, arranged in 5 columns × 5 rows, are positioned on each of the retainers 41–44. In the subsequent evaluation, [the following will be discussed / discussed]. Figure 9 The roller marked with reference numeral 31 is used as an evaluation roller. Furthermore, the roller marked with reference numeral 32 is used as a monitoring roller for measuring the atmosphere temperature of the furnace. The evaluation roller 31 and the monitoring roller 32 are disposed at the center of the second holder 42 and the third holder 43.

[0051] Next, with the retainer 40 placed in a furnace filled with argon gas, the furnace atmosphere temperature was controlled. This allowed the roller 30 to undergo heat treatment. The temperature profile for the heat treatment was obtained using... Figure 6 The temperature curves are shown. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Standby temperature T4 of standby process S12: 860℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Maintain argon pressure of 100 Pa during process S20. • Cooling rate C1 of cooling process S30: 100℃ / minute Argon pressure during cooling process S30: 200 kPa

[0052] Impregnation and etching evaluations were performed on the sintered mesh 20 obtained by heat treatment.

[0053] like Figure 10 As shown, in the immersion evaluation, a solution 51 was prepared and placed in container 50. Solution 51 was an acidic solution containing sulfuric acid. The pH value of solution 51 was 4.1. Next, while maintaining the temperature of solution 51 at 80°C, the sample 35 cut from the sintered mesh 20 was immersed in solution 51 for 16 hours. Afterward, the presence of discoloration in sample 35 was visually confirmed. No discoloration was observed.

[0054] In the etching evaluation, sample 35 was evaluated according to JIS G 0571:2003 "Test method for oxalic acid etching of stainless steel". Firstly, as... Figure 11 As shown, a test surface 36 is formed on the surfaces of the first metal wire 21 and the second metal wire 22 by grinding the surface of the sample 35. Next, the sample 35 is immersed in a 10% oxalic acid solution. Then, the sample 35 is electrolytically etched using the test surface 36 as the anode. Finally, the surface of the sample 35 is observed using a scanning electron microscope.

[0055] exist Figure 12 The results of the observations are shown in the figure. The first image, labeled with reference numeral 61, corresponds to... Figure 11 The state is shown. The second image, labeled with reference numeral 62, is an enlarged version of a portion of the first image 61. As shown in the second image 62, no sensitization has occurred.

[0056] (Example 2) Similar to Example 1, a roller 30 for the mesh sheet 26 was fabricated using SUS316L containing 0.01% by weight of carbon. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, similar to Example 1, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was obtained using... Figure 6 The temperature curves are shown. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Standby temperature T4 of standby process S12: 860℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Maintain argon pressure of 100 Pa during process S20. • Cooling rate C1 of cooling process S30: 65℃ / minute Argon pressure during cooling process S30: 110 kPa

[0057] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Figure 13 The image shown is from the etching evaluation. As shown in the second image 62, no sensitization occurred.

[0058] (Example 3) Similar to Example 1, a roller 30 for the mesh sheet 26 was fabricated using SUS316L containing 0.01% by weight of carbon. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, as in Example 1, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was obtained using... Figure 6 The temperature curves are shown. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Standby temperature T4 of standby process S12: 860℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Maintain argon pressure of 100 Pa during process S20. • Cooling rate C1 of cooling process S30: 3.3℃ / minute Argon pressure during cooling process S30: 110 kPa

[0059] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Figure 14 The image shown is from the etching evaluation. As shown in the second image 62, no sensitization occurred.

[0060] (Example 4) Similar to Example 1, the roller 30 for the mesh sheet 26 was fabricated using SUS316L containing 0.01% by weight of carbon. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, similar to Example 1, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was obtained using... Figure 6 The temperature curves are shown. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 10℃ / minute • Standby temperature T4 for standby process S12: 600℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1020℃ (for 30 minutes). • Maintain argon pressure of 100 Pa during process S20. • Cooling rate C1 of cooling process S30: 100℃ / minute Argon pressure during cooling process S30: 200 kPa

[0061] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Figure 15 The image shown is from the etching evaluation. As shown in the second image 62, no sensitization occurred.

[0062] (Example 5) Except for using SUS316 containing 0.04% by weight of carbon, the roller 30 of the mesh sheet 26 was manufactured in the same manner as in Example 1. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, as in Example 1, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was used... Figure 6 The temperature curves are shown. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Standby temperature T4 of standby process S12: 860℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Maintain argon pressure of 100 Pa during process S20. • Cooling rate C1 of cooling process S30: 100℃ / minute Argon pressure during cooling process S30: 200 kPa

[0063] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Figure 16 The image shown is from the etching evaluation. As shown in the second image 62, no sensitization occurred.

[0064] (Comparative Example 1) Similar to Example 1, a roller 30 for the mesh sheet 26 was fabricated using SUS316L containing 0.01% by weight of carbon. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was obtained using... Figure 6 The temperature curve is shown. The cooling process S30 is carried out in a nitrogen atmosphere. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Standby temperature T4 of standby process S12: 860℃ (maintained for 30 minutes) • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Cooling rate C1 of cooling process S30: 100℃ / minute • Nitrogen pressure during cooling process S30: 200 kPa

[0065] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Images obtained in the etching evaluation are shown below. Figure 17 As shown in the second image 62, sensitization occurred.

[0066] (Comparative Example 2) Similar to Example 5, the roller 30 for the mesh sheet 26 was fabricated using SUS316 containing 0.04% by weight of carbon. The widths S1 and S2 of the first metal wire 21 and the second metal wire 22 were 50 μm. Next, the roller 30 was heat-treated using a retainer 40. The temperature profile for the heat treatment was obtained using... Figure 5 The temperature curve is shown. The cooling process S30 is carried out in a nitrogen atmosphere. The heat treatment conditions are as follows. • Heating rate H1 of heating process S10: 20℃ / minute • Maintain the processing temperature T2 of process S20 at 1100℃ (for 60 minutes). • Cooling rate C1 of cooling process S30: 200℃ / minute • Nitrogen pressure during cooling process S30: 200 kPa

[0067] Similar to Example 1, impregnation and etching evaluations were performed on the sintered mesh 20 obtained through heat treatment. No discoloration was observed in the impregnation evaluation. Images obtained in the etching evaluation are shown below. Figure 18 As shown in the second image 62, sensitization occurred. Explanation of reference numerals in the attached figures:

[0068] 1: Filter device; 2: Housing; 10: Screen filter; 20: Sintered mesh; 21: First metal wire; 22: Second metal wire; 30: Roller; 31: Evaluation roller; 32: Monitoring roller; 35: Sample; 36: Test surface.

Claims

1. A method for manufacturing a sintered mesh, characterized in that, include: The process of preparing a screen consisting of multiple metal wires made of austenitic stainless steel and extending in directions that intersect each other. as well as A heat treatment process that controls the temperature of the atmosphere around the screen. The heat treatment process includes: a heating process that raises the temperature of the atmosphere to the treatment temperature; A holding step that maintains the atmosphere temperature at the processing temperature; and a cooling step that lowers the atmosphere temperature. The processing temperature is above the austenitizing temperature. The cooling process includes a rapid cooling process in which the temperature of the atmosphere decreases at a rate of 3°C / minute or higher under an argon atmosphere. In the cooling process, the pressure of the argon gas is higher than atmospheric pressure, specifically above 110 kPa and below 600 kPa. The heating process includes a rapid heating process that raises the temperature of the atmosphere at a rate of 5°C / minute or higher.

2. The method for manufacturing sintered mesh according to claim 1, characterized in that, In the holding process, the pressure of the atmosphere is lower than atmospheric pressure.

3. The method for manufacturing sintered mesh according to claim 1 or 2, characterized in that, The processing temperature is above 980℃ and below 1100℃.

4. The method for manufacturing sintered mesh according to claim 1 or 2, characterized in that, The sintered mesh is used as a filter for hydrogen fuel.

Images