Method for manufacturing an open rack type vaporizer component, and open rack type vaporizer component

Abstract

The present invention is a manufacturing method for an open rack vaporizer member, said method involving forming a thermal spray coating on a surface of a substrate composed of Al or an Al alloy by feeding Al powder or an Al alloy powder and Al2O3 powder into a high-velocity flame.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an open rack type vaporizer member and an open rack type vaporizer member. In particular, the present invention relates to a method for manufacturing an open rack type vaporizer member that uses a refrigerant containing corrosive components such as seawater, and an open rack type vaporizer member.

Background Art

[0002] An open rack type vaporizer is a device that heat-exchanges liquefied gas (e.g., LNG) in a low-temperature liquid state with a refrigerant (e.g., seawater) to vaporize the liquefied gas. FIGS. 7 and 8 are partial schematic views of a part of an open rack type vaporizer enlarged. FIG. 7 is a perspective view, and FIG. 8 is a side view. As shown in FIGS. 7 and 8, in an open rack type vaporizer, a lower header pipe 102 and an upper header pipe 104 are arranged at a distance in the vertical direction. LNG passes through a heat transfer pipe 103 that connects the lower header pipe 102 and the upper header pipe 104. The refrigerant overflowing from the refrigerant sprinkling trough 106 flows along the outside of the heat transfer pipe 103. Then, heat exchange occurs between the LNG inside the heat transfer pipe 103 and the refrigerant outside the heat transfer pipe 103. As a result, the LNG is vaporized into gas.

[0003] Vaporizer members such as the heat transfer pipe 103, header pipes 102, 104, etc. mounted on the heat exchange panel of an open rack type vaporizer are made of Al alloys (3000 series, 5000 series, 6000 series, etc.) with high thermal conductivity in order to easily absorb heat from seawater. However, when such vaporizer members are used in an environment where they are exposed to seawater as described above, there is a concern about corrosion. Therefore, it is desirable to perform anticorrosion treatment on the vaporizer members.

[0004] Conventionally, as an anticorrosion treatment for vaporizer members, for example, Patent Document 1 describes a method of performing wire-type flame spraying of an Al-2 mass% Zn alloy to form a sacrificial anode layer on the outer surface of an Al alloy base material.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-112294 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the inventors have found that the thermal spray coating described in Patent Document 1 does not have sufficient corrosion resistance and adhesion to the Al alloy substrate, and there is room for improvement.

[0007] The present invention aims to provide a method for manufacturing an open-rack type vaporizer component having a thermal spray coating with excellent corrosion resistance and adhesion to a substrate, and to provide an open-rack type vaporizer component having a thermal spray coating with excellent corrosion resistance and adhesion to a substrate. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing an open rack type vaporizer component, characterized by forming a thermal spray coating on the surface of a substrate made of Al or an Al alloy by introducing Al powder or Al alloy powder and Al2O3 powder into a high-speed flame.

[0009] A more preferred feature of the method for manufacturing the open rack type vaporizer component of the present invention is that the volume ratio of Al powder or Al alloy powder (A) to Al2O3 powder (B) is 0.1 ≤ (B) / (A) ≤ 3.5.

[0010] Furthermore, the open rack type vaporizer component of the present invention comprises a base material made of Al or an Al alloy and a thermal spray coating formed on the surface of the base material, wherein the thermal spray coating comprises a main phase made of Al or an Al alloy and Al2O3 particles dispersed in the main phase.

[0011] Three more preferred features of the open rack type vaporizer component of the present invention are as follows: (1) The Al2O3 content of the thermal spray coating is 10% or more and less than 30%. (2) The porosity of the thermal spray coating is less than 4%. (3) The adhesion of the thermal spray coating to the substrate is 25 MPa or more. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an open rack type vaporizer component equipped with a thermal spray coating that has excellent corrosion resistance and adhesion to the substrate. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic perspective view showing an example of an open-rack type vaporizer. [Figure 2] Figure 1 is a schematic perspective view showing an enlarged portion of an open-rack type vaporizer. [Figure 3] This graph shows the relationship between the volume ratio of the material powder (Al2O3 / Al) and the Al2O3 content in the coating for the test specimens of Examples 1 to 7. [Figure 4] This graph shows the relationship between the volume ratio of material powder (Al2O3 / Al) and the porosity in the coating for the test specimens of Examples 1 to 7. [Figure 5] This is a partial cross-sectional view of the thermal spray coating formed by the method of Example 3. [Figure 6] This is a partial cross-sectional view of a thermal spray coating formed by the method of Comparative Example 1. [Figure 7] This is a schematic perspective view showing a magnified portion of an open-rack type vaporizer. [Figure 8] This is a schematic side view showing an enlarged portion of an open-rack type vaporizer. [Modes for carrying out the invention]

[0014] An embodiment of the open rack type vaporizer component according to the present invention will be described below with reference to the figures.

[0015] FIG. 1 is a schematic perspective view showing an example of an open rack vaporizer. FIG. 2 is a schematic perspective view of a partially enlarged open rack vaporizer of FIG. 1. As shown in FIGS. 1 and 2, the open rack vaporizer 1 includes, for example, a lower header pipe 2, a heat transfer pipe 3, an upper header pipe 4, a refrigerant supply member 5, a refrigerant sprinkling trough 6, and a liquefied gas supply member 7. Liquefied gas flows into the lower header pipe 2. Gas obtained by vaporizing the liquefied gas flows out from the upper header pipe 4. The heat transfer pipe 3 connects the lower header pipe 2 and the upper header pipe 4. In the heat transfer pipe 3, the liquefied gas flowing in from the lower header pipe 2 vaporizes with heat from the external refrigerant as it flows upward. Then, the vaporized gas flows from the heat transfer pipe 3 into the upper header pipe 4. The refrigerant supply member 5 supplies a refrigerant for heat exchange with the liquefied gas outside the heat transfer pipe 3 in order to vaporize the liquefied gas. The liquefied gas supply member 7 supplies the liquefied gas to be vaporized.

[0016] In the open rack vaporizer 1, a plurality of lower header pipes 2 and a plurality of upper header pipes 4 are installed, and they extend in a direction parallel to the surface on which the open rack vaporizer 1 is installed. The heat transfer pipe 3 extends in a direction perpendicular to the extending direction of the lower header pipe 2 and the upper header pipe 4. Also, in order to increase the surface area where heat exchange can occur between the refrigerant and the liquefied gas, a plurality of heat transfer pipes 3 are gathered to form a panel. The refrigerant supply member 5 includes a portion extending parallel to the upper header pipe 4. The refrigerant sprinkling trough 6 is parallel to the upper header pipe 4 and is bent and extended so as to have an opening upward. The refrigerant sprinkling trough 6 is installed in the vicinity of the connection portion between the upper header pipe 4 and the heat transfer pipe 3. The refrigerant supply member 5 and the refrigerant sprinkling trough 6 are connected.

[0017] In this embodiment, LNG is used as the liquefied gas, and seawater is used as the refrigerant. Note that the refrigerant is not limited to seawater, and for example, fresh water may be used. The base materials of the lower header pipe 2, the heat transfer pipe 3, and the upper header pipe 4 are made of Al or an Al alloy with high thermal conductivity. Here, the Al alloy refers to an alloy in which the ratio of Al is the highest among the elements constituting the alloy. At this time, the Al content in the Al alloy is preferably 80% by mass or more, and more preferably 90% by mass or more. The type of the Al alloy is not particularly limited, and for example, Al-Mn based alloys, Al-Si based alloys, Al-Mg based alloys, Al-Cu based alloys, Al-Zn based alloys, Al-Mg-Si based alloys, Al-Mg-Cu based alloys, Al-Zn-Mg based alloys, etc. are used.

[0018] Next, an embodiment of a manufacturing method of an open rack type vaporizer member according to the present invention will be described.

[0019] As described above, since seawater is supplied to the vaporizer members made of Al or an Al alloy such as the lower header pipe 2, the heat transfer pipe 3, and the upper header pipe 4, there is a concern about corrosion. Therefore, a sprayed coating having an anticorrosion effect is formed on the surface of the vaporizer member.

[0020] The thermal spray coating in this embodiment is formed on the substrate surface of an open rack type vaporizer component mainly composed of Al or Al alloy by simultaneously introducing Al powder or Al alloy powder and Al2O3 powder into a high-speed flame. In this embodiment, a film formation method is employed in which Al powder or Al alloy powder and Al2O3 powder are supplied into the same high-speed flame. As a result, an Al film or Al alloy film is formed on the substrate surface, and unmelted Al2O3 particles collide at high speed with the surface of the Al film or Al alloy film immediately after formation, crushing the pores formed during film formation. By repeating this process, the entire film becomes densified, resulting in a thermal spray coating with excellent corrosion resistance and no through-pores. In particular, when the film near the substrate interface is pressed into the substrate surface and undergoes plastic deformation, the contact area between the substrate and the film increases. As a result, the anchoring effect is improved, and a thermal spray coating with superior adhesion to the substrate can be formed compared to conventional film formation methods. The high-speed flame can be generated by a commercially available high-speed flame thermal spraying apparatus. When unmolten Al2O3 particles collide with the surface of the Al alloy film, some of them are incorporated into the Al alloy film, thus forming the film. For example, as shown in the cross-sectional photograph of Figure 5, the thermal spray film formed in this embodiment is formed containing a main phase made of Al or an Al alloy, and unmolten Al2O3 particles dispersed in the main phase. In this specification, the main phase is defined as the phase whose area ratio of components in the thermal spray film is 50% or more when the thermal spray film is observed in cross-section.

[0021] In this embodiment, the material powders used to feed into the high-speed frame are Al powder or Al alloy powder and Al2O3 powder. Al and Al alloys have high thermal conductivity and readily function as a sacrificial corrosion protection layer. Examples of Al alloy powders used include Al-Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Cu alloys, Al-Zn alloys, Al-Mg-Si alloys, Al-Mg-Cu alloys, and Al-Zn-Mg alloys. The average particle size of the Al powder or Al alloy powder is preferably 20 to 100 μm, and the average particle size of the Al2O3 powder is preferably 8 to 450 μm. In this specification, "average particle size" is defined as the particle size (median diameter) at which the cumulative value of the particle size distribution is 50% when measured by laser diffraction / scattering (microtrac method).

[0022] In this embodiment, the volume ratio of Al powder or Al alloy powder (A) to Al2O3 powder (B) is preferably 0.1 ≤ ((B) / (A)), and more preferably 1.0 ≤ ((B) / (A)). Furthermore, the volume ratio of Al powder or Al alloy powder (A) to Al2O3 powder (B) is preferably ((B) / (A)) ≤ 3.5. When the volume ratio has this relationship, the adhesion of the thermal spray coating to the substrate is further improved, and the porosity can be further reduced. If the porosity of the thermal spray coating is high, the possibility of through-pores occurring in the thermal spray coating increases. If through-pores are present, seawater may penetrate from the surface of the thermal spray coating and reach the interface with the substrate. When seawater penetrates to the interface between the thermal spray coating and the substrate, corrosion progresses. Therefore, in order to suppress the progression of corrosion, the porosity of the thermal spray coating is preferably less than 4%, and more preferably 2.5% or less. Furthermore, if the particle content in the Al or Al alloy coating is too high, the inherent properties of Al or Al alloy may be impaired. However, if the Al2O3 content in the thermal spray coating is less than 30%, sufficient corrosion protection can be obtained. In fact, from the viewpoint of improving adhesion and reducing porosity, it is preferable that the Al2O3 particle content be 10% or more. Therefore, the Al2O3 content in the thermal spray coating is preferably 10% or more, and preferably less than 30%. Also, from the viewpoint of having Al or Al alloy as the main phase in the thermal spray coating, the Al or Al alloy content in the thermal spray coating is preferably 70% or more, and preferably less than 90%. The porosity of the thermal spray coating and the content of the components constituting the thermal spray coating can be determined by observing the cut surface of the coating, which is cut from a vaporizer member, after appropriate processing such as mirror polishing, under a microscope. For example, it can be determined by performing image analysis on a photograph taken at 100x magnification with a scanning electron microscope and calculating the area ratio of each part.

[0023] As described above, in this embodiment, the thermal spray coating is formed by unmelted Al2O3 particles colliding at high speed with the surface of the Al coating (Al alloy coating) immediately after deposition, and this process is repeated, resulting in a dense coating throughout. This dense coating makes it possible to form a coating that is less prone to through-pores, thus improving corrosion resistance. Furthermore, near the substrate interface of the thermal spray coating, the contact area between the substrate and the coating increases, improving the anchoring effect and making it possible to form a coating with high adhesion to the substrate.

[0024] In this embodiment, it is preferable that the adhesion force of the thermal spray coating to the substrate is 25 MPa or higher. As described above, since the open rack type vaporizer is a device that exchanges heat between a low-temperature liquefied gas located inside the vaporizer member and a refrigerant located outside the vaporizer member, the temperature gradient between the inner and outer surfaces of the vaporizer member becomes very large. Therefore, due to the temperature difference between the substrate located inside the vaporizer member and the thermal spray coating located on the outer surface of the vaporizer member, the difference in thermal expansion between the substrate and the thermal spray coating becomes large, which may cause the thermal spray coating to peel off. In addition, as the open rack type vaporizer repeatedly starts and stops, the vaporizer member is exposed to a thermal cycle, which may cause the thermal spray coating to peel off. In contrast, by setting the adhesion force of the thermal spray coating to the substrate to 25 MPa or higher, it is possible to suppress the peeling of the thermal spray coating.

[0025] Furthermore, the thermal spray coating in this embodiment is not limited to heat transfer tubes, upper header tubes, and lower header tubes, but can also be applied to other components. [Examples]

[0026] The following describes examples to which the present invention is applied. These examples are illustrative of the present invention and do not limit the scope of the invention.

[0027] [Example 1] As the substrate, an A5052 alloy (Al-Mg alloy) with dimensions of 50 x 50 x 5 mmt was prepared. Next, the substrate was blasted with WA (white alumina) F60 blasting material at a spray pressure of 0.3 MPa to roughen the surface. Then, a test specimen was formed by depositing a film on the roughened substrate in the following manner. Film deposition method: A material powder, a mixture of material 1 and material 2, is fed into a high-speed flame generated by a high-speed flame spraying apparatus. Material 1: Al powder (average particle size: 38μm) Material 2: Al2O3 powder (average particle size: 108μm) Volume ratio (Al2O3 powder / Al powder): 0.18

[0028] [Example 2] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 0.65.

[0029] [Example 3] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 1.05.

[0030] [Example 4] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 1.31.

[0031] [Example 5] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 1.98.

[0032] [Example 6] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 2.52.

[0033] [Example 7] Test specimens were prepared in the same manner as in Example 1, except that the volume ratio of the material powders (Al2O3 powder / Al powder) was 3.31.

[0034] [Example 8] Test specimens were prepared in the same manner as in Example 1, except that A5083 (Al-Mg alloy) was used as the base material, Al-3%Zn powder was used as material 1, and the volume ratio (Al2O3 powder / Al powder) was 1.05.

[0035] [Example 9] Test specimens were prepared in the same manner as in Example 1, except that A5083 (Al-Mg alloy) was used as the base material, Al-5%Mg powder was used as material 1, and the volume ratio (Al2O3 powder / Al powder) was 1.05.

[0036] [Comparative Example 1] Test specimens were prepared in the same manner as in Example 1, except that A5083 (Al-Mg alloy) was used as the substrate and the film was deposited according to the procedure described below. Film deposition method: The following materials are fed into a flame generated by a wire-type flame spraying apparatus. Material: Al wire

[0037] [Comparative Example 2] Test specimens were prepared in the same manner as in Example 1, except that only Al powder was used as the material.

[0038] After preparing test specimens using the methods described in Examples 1 to 9 and the methods described in Comparative Examples 1 and 2, the following measurements were performed on each test specimen.

[0039] [Al2O3 content] Each test specimen was cut perpendicular to the surface on which the coating was formed. The cut pieces were embedded in resin, and the resulting cross-sections were polished. Images of these coating cross-sections were then captured using a scanning electron microscope (JEOL Ltd., JSM-IT300LA). Next, these cross-sectional images were binarized using image analysis software (Mitani Corporation, WinROOF2018) to identify Al2O3 particles, and the proportion of the area of ​​Al2O3 particles within the thermal spray coating cross-section was calculated.

[0040] [Porosity] Each test specimen was cut perpendicular to the surface on which the coating was formed. The cut pieces were embedded in resin, and the resulting cross-sections were polished. Images of these coating cross-sections were then captured using a scanning electron microscope (JEOL Ltd., JSM-IT300LA). Next, these cross-sectional images were binarized using image analysis software (Mitani Corporation, WinROOF2018) to identify pores, and the proportion of the pore area to the thermal spray coating cross-section was calculated.

[0041] After preparing test specimens using the methods described in Examples 1 to 9 and the methods described in Comparative Examples 1 and 2, the following tests were performed on each test specimen.

[0042] [Adhesion Test] Adhesion tests were conducted using a method compliant with JIS H 8402, and the adhesion between the substrate and the thermal spray coating was evaluated based on the fracture surface pressure (MPa).

[0043] [Salt spray test] The salt spray test was conducted for 300 hours using a method compliant with JIS Z2371:2015. Afterward, cross-sectional observation was performed to check for the presence or absence of corrosion products at the interface between the coating and the substrate, thereby evaluating corrosion resistance. The meaning of the corrosion resistance evaluation index is as follows: ○: No corrosion products were observed after 300 hours. ×: Corrosion products were observed after 300 hours.

[0044] Table 1 summarizes the results of the measurements and tests performed on each test specimen for Examples 1-9 and Comparative Examples 1 and 2. Figure 3 is a graph showing the relationship between the volume ratio (Al2O3 powder / Al powder) and the Al2O3 content in the coating for each test specimen for Examples 1-7, and Figure 4 is a graph showing the relationship between the volume ratio (Al2O3 powder / Al powder) and the porosity in the coating for each test specimen for Examples 1-7.

[0045] [Table 1]

[0046] In the adhesion strength section of Table 1, none of the test specimens fractured between the substrate and the thermal spray coating. Fracture occurred between the thermal spray coating and the adhesive layer at a stress of less than 25 MPa. Therefore, the table shows at least the smallest adhesion strength observed. It was found that the thermal spray coatings of Examples 1 to 9 all had an adhesion strength of 25 MPa or higher. From this, it was confirmed that the adhesion strength was improved by at least three times compared to thermal spray coatings deposited by conventional wire flame spraying.

[0047] As shown in Table 1, the test specimens of Examples 1 to 9 were found to have better results than Comparative Example 1 in terms of porosity, adhesion, and corrosion resistance.

[0048] Figure 5 shows a photograph of a partial cross-sectional view of the film deposited by the method of Example 3, and Figure 6 shows a photograph of a partial cross-sectional view of the film deposited by the method of Comparative Example 1. It can be seen that the thermal spray coating of Example 3 has a dense structure throughout the entire film, while the thermal spray coating of Comparative Example 1 has a structure with many pores. Although not shown in the figures, the coatings of Examples 1 to 9 all had a dense structure throughout the entire film, as shown in Figure 5. From this, it can be inferred that the reason why the test specimens of Examples 1 to 9 showed better results in terms of porosity, adhesion, and corrosion resistance compared to the test specimen of Comparative Example 1 is because the entire film had a dense structure.

[0049] Furthermore, as shown in Figures 3 and 4, the Al2O3 content of the test specimens in Examples 3 to 7 is higher than that of Examples 1 and 2, and the porosity of the test specimens in Examples 3 to 7 is lower than that of Examples 1 and 2. In other words, it can be seen that when the Al2O3 content in the material powder or coating is above a certain level, the porosity decreases significantly. [Industrial applicability]

[0050] The open rack type vaporizer component according to the present invention can be used, for example, as a heat transfer tube, an upper header tube, or a lower header tube. [Explanation of Symbols]

[0051] 1. Open rack type vaporizer 2 Lower header pipe 3 Heat transfer tubes 4. Upper header pipe 5. Refrigerant supply component 6. Refrigerant spray trough 7. Liquefied gas supply component 102 Lower header pipe 103 Heat transfer tube 104 Upper header pipe 106 Refrigerant water spray trough

Claims

1. A method for manufacturing an open rack type vaporizer component, On the surface of a substrate made of Al or an Al alloy having an Al content of 80% by mass or more, Al powder or Al alloy powder and Al ２ O ３ A method for manufacturing an open-rack type vaporizer component, characterized by forming a thermal spray coating by introducing powder into a high-speed frame.

2. The Al powder or Al alloy powder (A) and the Al ２ O ３ A method for manufacturing a vaporizer member according to claim 1, wherein the volume ratio with powder (B) is 0.1 ≤ (B) / (A) ≤ 3.

5.

3. The invention comprises a base material made of Al or an Al alloy having an Al content of 80% by mass or more, and a thermal spray coating formed on the surface of the base material. The aforementioned thermal spray coating consists of a main phase made of Al or an Al alloy, and Al dispersed in the main phase. ２ O ３ An open-rack type vaporizer component characterized by containing particles.

4. Al of the thermal spray coating ２ O ３ The open rack type vaporizer component according to claim 3, wherein the content is 10% or more and less than 30%.

5. The open rack type vaporizer member according to claim 3, wherein the porosity of the thermal spray coating is less than 4%.

6. The open rack type vaporizer member according to claim 3, wherein the adhesion force of the thermal spray coating to the substrate is 25 MPa or more.

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