TW201809319A - Member formed from aluminum alloy and lng vaporizer - Google Patents

Abstract

A heat transfer pipe (13) (a member formed from an aluminum alloy) comprises a base (21) that is formed from an aluminum alloy and a coating film (22) that is formed on the surface of the base (21). The coating film (22) comprises: an outer layer (26) which is formed from an aluminum alloy that contains from 1% by mass to 20% by mass (inclusive) of magnesium; and an inner layer (25) which is formed between the base (21) and the outer layer (26) and is formed from an aluminum alloy that contains from 1% by mass to 20% by mass (inclusive) of zinc. An LNG vaporizer according to the present invention is provided with this heat transfer pipe (13), a lower header pipe (14) (a member formed from an aluminum alloy) and a trough (12) (a member formed from an aluminum alloy).

Description

Aluminum alloy components and LNG gasifier

The present invention relates to an aluminum alloy component and a liquefied natural gas (LNG) gasifier. In particular, the present invention relates to aluminum alloy members and various gasifiers, heat exchangers, and the like that are excellent in corrosion resistance under corrosive environments such as seawater environments and are used in gasification members such as liquefied natural gas and liquefied petroleum gas, A liquefied natural gas (LNG) gasifier provided with this component.

Conventionally, as a heat transfer member used in a liquefied natural gas (hereinafter also referred to as LNG) gasifier, various heat exchangers, and other heat transfer tubes, and a gas collecting tube, an aluminum alloy member having good thermal conductivity has been mostly used. Such an aluminum alloy member may cause local corrosion (pitting corrosion) to progress due to long-term exposure to the atmosphere, water, or the like, and as a result, the member may be penetrated.

Therefore, it is necessary to take some anti-corrosion measures for aluminum alloy members. As one of the countermeasures, cathodic corrosion prevention methods are mostly used. In this method, a substrate made of an aluminum alloy is brought into contact with a sacrificial anticorrosion film, fin, or the like of an Al-Zn alloy or the like having a lower corrosion potential than the substrate, thereby obtaining an anticorrosive effect of the substrate. In addition, it is also used in closed systems such as the inner surface of heat transfer tubes of heat exchangers, and the method of adding corrosion inhibitors to circulating water law.

In recent years, LNG has attracted attention as a clean energy source, and is generally stored and transported in a state where it is liquefied at an extremely low temperature of -162 ° C or lower. In an open-frame gasifier (ORV), LNG is gasified before use by using seawater as a heat source for heat exchange. In general, an ORV structure-based aluminum alloy heat transfer tube is arranged in a thin sheet, LNG flows from the lower side to the upper side inside the heat transfer tube, and seawater flows down from the upper side to the lower side of the outside of the sheet. Therefore, the outer surface of the ORV heat transfer tube is exposed to seawater, so that the progress of corrosion becomes a problem.

In particular, a very small amount of copper ions contained in seawater will precipitate out of the surface of the aluminum alloy and act as a cathode, and thus significantly promote corrosion of the aluminum alloy. Therefore, the corrosion life of the heat transfer tube is extremely shortened in a sea area with a large amount of copper ions. Therefore, an effective corrosion reduction method is further required. In addition, in the case of an ORV heat transfer tube, when a countermeasure against corrosion on the outer side of the pipe is required, it is difficult to use a corrosion inhibitor. Therefore, a countermeasure against corrosion from a material side is required. On the other hand, in Patent Document 1 described below, it is proposed that a film made of an aluminum alloy having a larger Mg content than the base material of the heat transfer tube be formed on the surface of the base material as a sacrificial anticorrosive film.

In the ORV heat transfer tube, seawater enters the unavoidable pores in the sacrificial anticorrosion coating, so that corrosion occurs preferentially at the interface between the sacrificial anticorrosion coating and the substrate. Corrosion products generated by this corrosion, volume expansion due to freezing of seawater entering the pores, etc., cause expansion and peeling of the sacrificial corrosion-resistant film. As a result, there is a problem that the service life of the heat transfer tube is shortened. In contrast, in the following specialty It is proposed in Literary Document 2 to adjust the roughness of the interface between the sacrificial anticorrosive film and the substrate made of Al-Zn alloy or Al-Mg alloy to prevent the sacrificial anticorrosive film from expanding and peeling.

As proposed in the following Patent Documents 1 and 2, by forming a sacrificial anticorrosion coating composed of an Al-Zn alloy, an Al-Mg alloy, etc., it is possible to make the ORV exposed to a corrosive medium such as seawater to some extent Durability of heat transfer tubes. However, the anti-corrosion effect of these previous countermeasures is not sufficient. From the viewpoint of stable energy supply, in order to improve the safety of liquefied natural gas (LNG) gasifiers and various heat exchangers, further corrosion reduction and Extended life.

Specifically, as described in Patent Document 1 below, when a film made of an aluminum alloy containing Mg is formed on the surface of a base material of a heat transfer tube, the corrosion point of Mg is lower than that of Al, and sacrificial corrosion prevention can be obtained. The effect is, however, that the pitting of the film progresses and the substrate surface of the heat transfer tube is easily reached. Therefore, seawater easily enters the interface between the film and the substrate through the holes, and corrosion occurs at the interface. Therefore, there is a problem that the film swells due to corrosion generation, and the film becomes easily peeled. In addition, as in Patent Document 2 described below, by adjusting the interface roughness between the sacrificial anticorrosive film and the substrate, the film swelling, peeling, and the like can be suppressed to some extent, but the effect is not sufficient.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-78237

[Patent Document 2] Japanese Patent Laid-Open No. 2014-157009

An object of the present invention is to provide an aluminum alloy member having excellent sacrificial corrosion resistance and capable of more effectively suppressing expansion of a film formed on a surface of a substrate, and a liquefied natural gas (LNG) gasifier having the same.

One aspect of the present invention includes an aluminum alloy member including: a base material made of an aluminum alloy; and a film formed on a surface of the base material. The coating system includes an outer layer composed of an aluminum alloy containing 1% by mass to 20% by mass of magnesium, and an inner layer composed of an aluminum alloy containing 1% by mass to 20% by mass of zinc.

In another aspect of the present invention, a liquefied natural gas (LNG) gasifier is provided with the aforementioned aluminum alloy member.

12‧‧‧slot

13‧‧‧ heat transfer tube

14‧‧‧lower gas collector

21‧‧‧ substrate

22‧‧‧ capsule

25‧‧‧ inner layer

26‧‧‧ Outer

FIG. 1 is a schematic diagram showing a structure viewed from the side of an open-rack gasifier (ORV) according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional structure of an ORV.

Fig. 3 is a schematic view showing a cross-sectional structure of a heat transfer tube constituting an ORV.

FIG. 4 is a schematic diagram for explaining the local corrosion progress of the sacrificial anti-corrosion film caused by seawater in the comparative example.

FIG. 5 is a schematic diagram for explaining the local corrosion progress of the sacrificial anti-corrosion film caused by seawater in this embodiment.

Fig. 6 is a schematic view showing a cross-sectional structure of a lower header constituting an ORV.

FIG. 7 is a schematic view showing a cross-sectional structure of a groove constituting an ORV.

FIG. 8 is a schematic diagram showing the structure of an intermediate medium-type LNG gasifier (IFV) according to Embodiment 2 of the present invention.

FIG. 9 is a schematic diagram showing a cross-sectional structure of a heat transfer tube constituting an IFV.

FIG. 10 is a schematic diagram showing a test material for evaluating the swelling resistance of a film.

FIG. 11 is a schematic diagram showing a test material for evaluating the sacrificial corrosion resistance of a film.

(Outline of the embodiment of the present invention)

First, the outline of the aluminum alloy member and the liquefied natural gas (LNG) gasifier concerning embodiment of this invention is demonstrated.

The aluminum alloy member according to this embodiment includes a base material made of an aluminum alloy, and a film formed on a surface of the base material. The coating system includes an outer layer composed of an aluminum alloy containing 1% by mass to 20% by mass of magnesium, and an inner layer composed of an aluminum alloy containing 1% by mass to 20% by mass of zinc.

The present inventors have targeted exposure to seawater containing copper ions, etc. The durability of aluminum alloy members made of corrosive solutions is being examined intensively. Specifically, measures for preventing the initial deterioration of the sacrificial anticorrosive film, that is, the swelling of the film, and ensuring the anticorrosiveness of the substrate even after the substrate is exposed due to the deterioration of the film, have been carefully reviewed. As a result, the present inventors have found that the formation of an outer layer composed of an Al-Mg alloy and an inner layer composed of an Al-Zn alloy can be formed on the surface of the substrate as a coating, the composition of which is adjusted to an appropriate range. The present invention has been developed by suppressing the expansion of the film that has initially deteriorated, and improving the corrosion resistance of the substrate after the substrate is exposed.

The said aluminum alloy member is formed with the outer layer which consists of an aluminum alloy containing 1 mass% or more and 20 mass% or less of magnesium. Since magnesium has an element with a lower corrosion potential than aluminum, the sacrificial corrosion resistance of the film can be improved by including magnesium in the outer layer exposed to seawater. That is, even after the corrosion progresses and the surface of the base material is exposed, the outer layer is preferentially corroded over the base material to ensure the corrosion resistance of the base material.

In order to obtain such an effect, the magnesium content of the outer layer is adjusted to 1% by mass or more. However, if the magnesium content in the outer layer is excessive, the rate of consumption of the film will increase, making it difficult to obtain a desired service life. Therefore, the magnesium content in the outer layer is adjusted to 20% by mass or less. The magnesium content in the outer layer is preferably 1.2% by mass or more, and more preferably 1.5% by mass or more. The magnesium content in the outer layer is preferably 19% by mass or less, and more preferably 18% by mass or less.

As described above, the sacrificial corrosion resistance of the film can be improved by forming an outer layer whose magnesium content is appropriately adjusted. In the case of a single-layer coating, there are the following problems. That is, when a single-layer coating composed of only the outer layer is formed on the surface of the substrate, if local corrosion such as pitting occurs in the coating, the pH at the bottom of the pores decreases and the chloride is concentrated. Etc., causing the corrosion rate in the depth direction to increase. As a result, local corrosion easily reaches the substrate. In this case, the seawater entering from the hole of the film will reach the interface between the substrate and the film, so that corrosion occurs at this interface. Therefore, there is a problem that the volume of the film is expanded due to corrosion products generated at the interface portion, and the film is expanded.

On the other hand, the present inventors have obtained the insight that by forming an appropriate amount of an inner layer containing zinc with a corrosion potential in the middle of magnesium and aluminum between the substrate and the outer layer, it is possible to suppress such a locality as described above. Corrosion proceeds. The zinc-based corrosion potential is lower than that of the aluminum of the substrate, but the corrosion potential is higher than that of the outer layer of magnesium. Therefore, it has the ability to suppress the local corrosion of the outer layer made of the Al-Mg alloy. Therefore, by forming the inner layer, it is possible to prevent seawater from reaching the interface between the substrate and the film, and as a result, it is possible to suppress the expansion of the film caused by the progress of the interface corrosion. In addition, since the corrosion potential of the inner layer is lower than that of the base material, it can function as a sacrificial anticorrosive film in the same manner as the outer layer after the base material is exposed.

In order to obtain such an effect, the zinc content of the inner layer is adjusted to 1% by mass or more. However, if the content of zinc in the inner layer is excessive, the rate of consumption of the film will increase, making it difficult to obtain a desired service life. Therefore, the zinc content in the inner layer is adjusted to 20% by mass or less. The content of zinc in the inner layer is preferably 1.2% by mass or more, and more preferably 1.5% by mass or more on. The zinc content in the inner layer is preferably 19% by mass or less, and more preferably 18% by mass or less.

In the aforementioned aluminum alloy member, the outer layer may further contain a smaller amount of zinc than magnesium. The aforementioned inner layer may further contain a smaller amount of magnesium than zinc.

In this way, the outer layer also contains zinc which is the same as the element contained in the inner layer, and the inner layer also contains magnesium which is the same as the element contained in the outer layer, thereby improving the affinity between the inner layer and the outer layer. As a result, the adhesion between layers can be improved.

In the aforementioned aluminum alloy member, the magnesium content in the outer layer may be greater than the magnesium content in the inner layer.

As described above, since magnesium is an element that lowers the corrosion potential of the film and improves the sacrificial corrosion resistance, it is desirable to contain more in the outer layer exposed to seawater than in the inner layer.

The aluminum alloy member may be a layer of at least one of the outer layer and the inner layer, further containing from 0.01% by mass to 1.0% by mass of silicon, 0.01% by mass to 1.0% by mass of iron, and 0.01. At least 1.0% by mass of copper, 0.01% by mass of 1.0% by mass of manganese, 0.01% by mass of 1.0% by mass of chromium, and 0.01% by mass of 1.0% by mass of titanium An element.

Silicon, iron, copper, manganese, chromium, and titanium have the effect of reducing the anode reaction rate of aluminum and reducing the consumption rate of the film. However, if the content of these elements is excessive in the film, the corrosion potential will increase. High, resulting in reduced sacrificial corrosion resistance. Therefore, the content of these elements in the outer layer or the inner layer is preferably from 0.01% by mass to 1.0% by mass.

In the aforementioned aluminum alloy member, the aforementioned substrate system may be composed of one of the 3000 series, the 5000 series, and the 6000 series. Here, [3000 series, 5000 series, and 6000 series] refer to the international aluminum alloy names.

The aluminum alloy member is made of an aluminum alloy having a good thermal conductivity and no brittle fracture at low temperatures, and a good toughness. Among aluminum alloys, from the viewpoint of strength, 2000-series, 3000-series, 5000-series, 6000-series, or 7000-series aluminum alloys are preferably used. However, it is particularly desirable to use 3000-series, 5000-series, and 6000-series aluminum alloys. Aluminum alloy. By using these types of aluminum alloys, good strength and corrosion resistance can be obtained. Specifically, A3003, A3203, A5052, A5154, A5083, A6061, A6063, or A6N01 can be used. In addition, heat treatments such as quenching, tempering, and artificial aging can be used as needed.

The aluminum alloy member may be a user in a low temperature environment of 0 ° C or lower. Since the aforementioned aluminum alloy member is formed on the surface of the substrate with a film having excellent sacrificial corrosion resistance, it can be used continuously for a long life even when it is used in a low temperature environment of 0 ° C or lower.

The aluminum alloy member may constitute a heat transfer pipe or a gas collecting pipe as a liquefied natural gas (LNG) gasifier.

The aforementioned aluminum alloy member has excellent sacrificial corrosion resistance A film that is formed on the surface of a base material. Therefore, even in the case of using heat transfer pipes and gas collecting pipes of liquefied natural gas (LNG) gasifiers, which are exposed to seawater of corrosive media and subjected to temperature changes of low and normal temperature, high corrosion resistance can be obtained. .

The liquefied natural gas (LNG) gasifier of the present invention includes the aforementioned aluminum alloy member. As mentioned above, the said aluminum alloy member is an excellent aluminum alloy member, and can suppress the expansion of a film. Therefore, by including the aforementioned aluminum alloy member, the life of a liquefied natural gas (LNG) gasifier can be further increased.

(Details of the embodiment of the present invention)

Hereinafter, an aluminum alloy member and a liquefied natural gas (LNG) gasifier according to embodiments of the present invention will be described in detail with reference to the drawings. In the following description, each element is represented by one of an element name and a chemical symbol.

<Embodiment 1> [Liquefied natural gas (LNG) gasifier]

First, the structure of a liquefied natural gas (LNG) gasifier 1 according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 schematically shows the structure viewed from the side of a liquefied natural gas (LNG) gasifier 1. FIG. 2 schematically illustrates a cross-sectional structure of a liquefied natural gas (LNG) gasifier 1 along a line segment II-II in FIG. 1.

Liquefied natural gas (LNG) gasifier 1 series open rack Vaporizer (ORV). This liquefied natural gas (LNG) gasifier 1 uses seawater as a heat source (fluid), and uses the LNG of the liquefied gas at a very low temperature (below -162 ° C) flowing through the heat transfer pipe 13 and the heat transfer Heat exchange is performed between seawater at the outside temperature of the tube 13 to vaporize LNG. The liquefied natural gas (LNG) gasifier 1 includes a plurality of heat transfer tube panels 11 that perform heat exchange between LNG and seawater, and a tank 12 that supplies seawater to the heat transfer tube panels 11. Seawater can also contain trace amounts of copper ions.

As shown in FIG. 2, the heat transfer tube panels 11 are arranged in a vertical posture, and are arranged at intervals in the horizontal direction. As shown in FIG. 1, the heat transfer tube panel 11 is provided with: a plurality of heat transfer tubes 13 arranged at intervals from each other; a lower gas collecting tube 14 connected to the lower end of each heat transfer tube 13; and each heat transfer tube 13 的 上 上 上部 气管 15。 15 upper part of the upper gas collecting tube 15. An inlet manifold 16 is connected to the lower header 14 to communicate therewith. An outlet manifold 17 communicating with the upper header 15 is connected to the upper header 15.

The heat transfer tube 13 and the lower gas collecting tube 14 are heat transfer members, and are used in a low-temperature environment of 0 ° C or lower in order to allow extremely low-temperature LNG to flow. The heat transfer tube 13 and the lower gas collecting tube 14 are each constituted by an aluminum alloy member according to this embodiment, and details thereof will be described later.

The tank 12 is composed of an aluminum alloy member according to the present embodiment, and is formed of a container that is opened at the top and can be stored in seawater. As shown in FIG. 2, the groove 12 is disposed between the adjacent heat transfer tube panels 11 on the upper side (lower side than the upper header 15) of the heat transfer tube panel 11. The tank 12 stores seawater supplied from a seawater header (not shown). Again, like the arrows in Figure 2 As shown by the symbol, the seawater overflowing from the tank 12 flows on each heat transfer tube panel 11 and flows along the outer surface of the heat transfer tube 13. The details of the groove 12 will be described later.

The gasification procedure of LNG by the aforementioned liquefied natural gas (LNG) gasifier 1 will be described. First, LNG flows into the inlet manifold 16 and the lower header 14 in this order, and then it is divided into the heat transfer tubes 13. Then, as shown in FIG. 2, in the flow path 7 inside each heat transfer tube 13, LNG flows from the lower side to the upper side, and the seawater supplied from the tank 12 to the heat transfer tube panel 11 is along the outside of the heat transfer tube 13. Exile. In this process, LNG is formed into NG by heat exchange (sea heat absorption) with seawater via the heat transfer tube 13 and gasification. Then, NG accumulates in the upper header 15 and is discharged through the outlet manifold 17 as, for example, normal temperature gas.

In the aforementioned liquefied natural gas (LNG) gasifier 1, a member for allowing seawater to flow or a member for storing seawater, such as a heat transfer pipe 13, a lower gas collecting pipe 14, and a tank 12, constituted by an aluminum alloy member is included in the aforementioned LNG During the gasification process, it was exposed to seawater in a corrosive medium. Specifically, the outer surface of the heat transfer tube 13 and the lower header 14 and the inner surface of the tank 12 are exposed to seawater. Therefore, if an anti-corrosion coating is not formed, during the operation of the aforementioned liquefied natural gas (LNG) gasifier 1, local corrosion such as pitting and the like due to aluminum corrosion progresses due to prolonged exposure to seawater. In particular, when the seawater contains copper ions, corrosion progresses remarkably, and the heat transfer tube 13 and the lower gas collecting tube 14 undergo a temperature change between low temperature and normal temperature. Therefore, corrosion becomes easier to proceed. On the other hand, the heat transfer tube 13, the lower gas collecting tube 14, and the groove 12 constituted by the aluminum alloy member of this embodiment. It is to form a sacrificial anti-corrosion film with excellent anti-corrosion property on the surface of each base material (base material), thereby effectively preventing the progress of corrosion. The following is a detailed description of each of the heat transfer tube 13, the lower gas collecting tube 14, and the tank 12.

[Heat transfer tube]

FIG. 3 shows a cross-sectional structure of the heat transfer tube 13 along the radial direction. The heat transfer tube 13 is a flow path 7 in which an LNG flow is formed. The heat transfer tube 13 includes a base material 21 made of an aluminum alloy, and a coating film 22 formed on the outer surface of the base material 21.

The substrate 21 is provided with a hollow cylindrical tube body 23 having a flow path 7 formed thereon, and a plurality of (ten in this embodiment) fins 24 protruding from the outside of the tube body 23 toward the outside in the radial direction. . The fins 24 are for increasing the heat transfer area of the heat transfer tube 13 and have the same shape and the same size, respectively. As shown in FIG. 3, the fins 24 are formed on the outside of the tube body 23 and are formed at equal intervals along the circumferential direction. In addition, the form of the fins 24 is not limited to this, and the plurality of fins 24 may be different in shape and size from each other, or may be formed at different intervals along the circumferential direction.

The base material 21 is composed of an aluminum alloy having excellent heat transfer properties in order to improve the heat exchange efficiency between LNG and seawater. From the viewpoint of strength and corrosion resistance, one of the 3000 series, 5000 series, and 6000 series is used. Made of alloy. More specifically, the substrate 21 is made of an aluminum alloy such as A3003, A3203, A5052, A5154, A5083, A6061, A6063, or A6N01.

The coating film 22 is a sacrificial anti-corrosion coating film for preventing corrosion of the base material 21, and is formed on the outer surface of the base material 21 so as to follow the shape of the tube body 23 and the fins 24. The characteristic point of the heat transfer tube 13 constituted by the aluminum alloy member according to this embodiment is that the coating layer 22 is composed of an outer layer 26 made of an Al-Mg-based alloy and an inner layer 25 made of an Al-Zn alloy. Layer structure.

As shown in FIG. 3, since the outer layer 26 is a layer including the outermost surface 22A of the film 22, it is mainly in contact with the seawater overflowing from the groove 12 (FIG. 2). The outer layer 26 is composed of an aluminum alloy formed by containing Mg of 1% by mass or more and 20% by mass or less, and the remaining portion is aluminum and unavoidable impurities. Here, [unavoidable impurities] means an amount that does not hinder the corrosion resistance of the outer layer 26, and examples thereof include elements such as H, O, C, and B.

Mg is an element having a lower corrosion potential than Al, and by making the corrosion potential of the outer layer 26 lower than that of the substrate 21, the sacrificial corrosion resistance is improved. That is, even in a state where the surface of the base material 21 is exposed while the corrosion progresses, the outer layer 26 is preferentially etched (sacrifice corrosion prevention) over the base material 21 to prevent the base material 21 from being corroded. In order to enhance such a sacrificial corrosion prevention effect, the Mg content of the outer layer 26 is adjusted to 1% by mass or more. On the other hand, if the Mg content of the outer layer 26 is excessive, the consumption rate of the film will increase and it will be difficult to obtain a desired life. Therefore, the Mg content of the outer layer 26 is adjusted to 20% by mass or less. The Mg content of the outer layer 26 is preferably 1.2% by mass or more and 19% by mass or less, more preferably 1.5% by mass or more and 18% by mass or less, and more preferably 4% by mass or more and 6% by mass or less. Ideally, it is about 5 mass%. Also, as mentioned above, since the outer layer 26 is the layer containing the outermost layer 22A of the film 22 and is required to have a higher sacrificial corrosion resistance than the inner layer 25, the Mg content of the outer layer 26 is higher than the Mg content of the inner layer 25 many.

Here, as shown in FIG. 4, as shown in the comparative example, in the case where the coating film 22 is composed of a single-layer coating film of the outer layer 26 formed of only an Al-Mg-based alloy, the corrosion rate in the depth direction of the outer layer 26 Since it is large, the hole 26A easily reaches the base material 21. In this case, seawater enters through the hole 26A formed in the outer layer 26, and corrosion progresses at the interface 21A between the substrate 21 and the outer layer 26. Therefore, there is a problem that the volume of the coating film 22 is expanded due to the corrosion product 21B generated at the interface 21A, and the problem of the expansion of the coating film 22 arises.

On the other hand, in the heat transfer tube 13 of this embodiment, an inner layer 25 made of an aluminum alloy containing a proper amount of Zn is formed between the base material 21 and the outer layer 26. As shown in FIG. 3, the inner layer 25 is formed in contact with the outer surface of the base material 21 (the tube body 23 and the fins 24), and the outer layer 26 is formed in contact with the outer surface of the inner layer 25.

The inner layer 25 is composed of an aluminum alloy formed by containing zinc in an amount of 1% by mass or more and 20% by mass or less, and the remaining portion is aluminum and unavoidable impurities. The Zn-based corrosion potential of the inner layer 25 is lower than that of Al of the substrate 21, but the corrosion potential is higher than the Mg of the outer layer 26. Therefore, the corrosion potential of the inner layer 25 is higher than that of the outer layer 26. Therefore, as shown in FIG. 5, even when the hole 26A is formed by the local corrosion of the outer layer 26, the corrosion potential of the inner layer 25 is higher than that of the outer layer 26, so that the hole 26A can be prevented from reaching the surface of the substrate 21. surface. That is, the inner layer 25 functions as a film layer for preventing pitting of the film 22 from reaching the substrate 21. Therefore, the progress of corrosion at the interface 21A between the film 22 and the substrate 21 as described with reference to FIG. 4 can be suppressed, and the expansion of the film 22 can be suppressed. As a result, peeling of the coating film 22 can be suppressed. In order to obtain such an effect, the Zn content of the inner layer 25 is 1 mass% or more and 20 mass% or less, preferably 1 mass% or more and 3 mass% or less, and most preferably about 2 mass%.

As described above, in the heat transfer tube 13 of this embodiment, the corrosion potential of the inner layer 25 is lower than that of the base material 21, and the corrosion potential of the outer layer 26 is lower than that of the inner layer 25. That is, in the heat transfer tube 13, the corrosion potential is lowered in the order of the base material 21, the inner layer 25, and the outer layer 26 (the order of the outer layer 26, the inner layer 25, and the base material 21 is high). To explain from another point of view, the heat transfer tube 13 has a first anti-corrosion film (inner layer 25) and a second anti-corrosion film (outer layer 26). The first anti-corrosion film is formed closer to the substrate than the second anti-corrosion film. In addition, the corrosion potential of the first corrosion protection film is lower than the corrosion potential of the substrate, and is higher than the corrosion potential of the second corrosion protection film.

The film 22 (the inner layer 25 and the outer layer 26) is formed on the outer surface of the base material 21 by, for example, a thermal spray method. As the thermal spraying method, a general method such as flame thermal spraying, high-speed flame thermal spraying, burst thermal spraying, arc thermal spraying, plasma thermal spraying, or laser thermal spraying can be adopted. As the fuel for flame thermal spraying, a mixed gas of propane and oxygen, a mixed gas of acetylene and oxygen, and the like can be used. In addition, as the thermal spray material, an aluminum alloy wire having the same composition as that of the film 22 (the inner layer 25 and the outer layer 26), Powder etc.

Here, before the construction of forming the inner layer 25 by thermal spraying, the appropriate adhesion of the base material 21 and the inner layer 25 can be improved by performing appropriate pretreatment on the outer surface of the base material 21. Specifically, the surface roughness of the outer surface of the base material 21 is adjusted to an appropriate range by a shot blast process, a grid blast process, or the like. The surface roughness of the substrate 21, for example, the average roughness Ra can be 1 μm or more and 30 μm or less, and the maximum roughness Rmax can be 10 μm or more and 100 μm or less. At this time, if the abrasive cleaning material used for the blasting process remains on the outer surface of the base material 21, when the inner layer 25 is formed by thermal spraying, the adhesion between the inner layer 25 and the base material 21 is reduced. Therefore, after performing the blasting treatment, it is preferable to remove the abrasive cleaning material by scrubbing or the like.

The thickness T of the coating film 22 (the sum of the thickness T1 of the outer layer 26 and the thickness T2 of the inner layer 25) can be adjusted according to the conditions at the time of thermal spraying, but the range is formed to be 100 μm or more and 1000 μm or less. If the thickness T of the coating film 22 is too small, it is difficult to sufficiently suppress the entry of corrosive substances such as chloride ions and oxygen into the substrate 21. In addition, since the film 22 is dissolved early, it is difficult to obtain a sufficient anticorrosive effect over a long period of time. On the other hand, if the thickness T of the coating film 22 is too large, peeling of the coating film 22 may occur due to a change in temperature between low temperature and normal temperature, and cracks may occur in the coating film 22, making it difficult to obtain a sufficient anticorrosive effect. Therefore, the thickness T of the coating 22 is adjusted to a range of 100 μm to 1,000 μm, more preferably 980 μm or less, and even more preferably 950 μm or less. The thicknesses T1 and T2 of the outer layer 26 and the inner layer 25 are adjusted to 50 μm or more and 500 μm or more. The lower range is preferably 60 μm or more, and more preferably 70 μm or more.

[Lower header, trough]

FIG. 6 shows a cross-sectional structure of the lower header 14 in the radial direction. FIG. 7 shows a cross-sectional structure of the groove 12. As shown in FIG. 6, the lower header 14 includes a hollow cylindrical substrate 31 having a flow path 33 through which LNG flows, and a film formed on the entire outer surface of the substrate 31 by a method such as thermal spraying. 32. As shown in FIG. 7, the groove 12 includes a base material 41 and a coating film 42 formed on the entire outer surface of the base material 41 by a method such as thermal spraying. The base material 41 is constituted by a container in which an opening portion 43 is formed.

The base materials 31 and 41 are made of an aluminum alloy having excellent thermal conductivity in the same manner as the base material 21 constituting the heat transfer tube 13. The coatings 32 and 42 are the same as those of the coating 22 constituting the heat transfer tube 13. That is, the coatings 32 and 42 are formed on the surfaces of the substrates 31 and 41, and include the inner layers 34 and 44 formed of an aluminum alloy containing 1% by mass or more and 20% by mass or less of Zn and the inner layers. The surface of 34 and 44 is formed by a two-layer structure of an outer layer 35 and 45 composed of an aluminum alloy containing Mg of 1% by mass or more and 20% by mass or less. Therefore, similar to the heat transfer tube 13 described above, excellent sacrificial corrosion resistance can be exhibited, and peeling from the surfaces of the substrates 31 and 41 due to expansion of the films 32 and 42 can be prevented.

[Summary of Embodiment 1]

As described above, the aluminum alloy member (heat transfer tube) of Embodiment 1 13. The lower headers 14 and the grooves 12) are formed by coatings 22, 32, and 42 on the surfaces of the base materials 21, 31, and 41 made of aluminum alloy. In addition, the coatings 22, 32, and 42 include outer layers 26, 35, and 45 composed of Mg containing 1% by mass to 20% by mass, the remainder being aluminum and unavoidable impurities, and 1% by mass. % And 20% by mass or less of Zn, and the remaining portion is formed by the two-layer structure of the outer layers 25, 34, and 44 composed of aluminum and unavoidable impurities. With this feature, the outer layers 26, 35, and 45 can exhibit excellent sacrifice corrosion resistance even when they are used in an environment exposed to a corrosive medium such as seawater when subjected to temperature changes of low temperature and normal temperature. Therefore, since the corrosion deterioration of the base materials 21, 31, and 41 becomes difficult, the life of the members can be extended, and the number of periodic maintenance can be reduced. Therefore, the safety of the liquefied natural gas (LNG) gasifier 1 can be improved, and the maintenance management cost can be reduced. In addition, the inner layers 25, 34, and 44 prevent pitting of the coatings 22, 32, and 42 from reaching the substrates 21, 31, and 41 (FIG. 5), and the corrosion of the interface 21A can also be performed to prevent the coatings 22, 32, and 42 inflated. As a result, peeling of the films 22, 32, and 42 from the surfaces of the base materials 21, 31, and 41 can be suppressed.

[Modification of Embodiment 1]

Next, a modification of the first embodiment will be described.

The outer layers 26, 35, and 45 may be composed of Mg containing 1% by mass or more and 20% by mass or less and Zn less than Mg, and the remaining portion is aluminum and unavoidable impurities. In this case, the Zn content of the outer layer 26 is, for example, 0.01% by mass or more and 1.2% by mass or less. And the inner layer 25, 34, 44 may be composed of Zn containing 1% by mass or more and 20% by mass or less and Mg in a smaller amount than Zn, and the remainder is aluminum and unavoidable impurities. In this case, the Mg content of the inner layers 25, 34, and 44 is, for example, 0.01% by mass or more and 0.52% by mass or less. In this way, the outer layers 26, 35, 45 also contain the same Zn as the elements contained in the inner layers 25, 34, 44 and the inner layers 25, 34, 44 also contain the same elements as the outer layers 26, 35, 45. With Mg, the affinity of the inner layers 25, 34, 44 and the outer layers 26, 35, 45 can be made. This improves the adhesion between the inner layers 25, 34, and 44 and the outer layers 26, 35, and 45, and improves the durability of the aluminum alloy member.

At least one of the outer layers 26, 35, 45 and the inner layers 25, 34, 44 may be formed of the following aluminum alloy, which further contains Si and 0.01 mass% from 0.01% by mass to 1.0% by mass Fe above 1.0% by mass, Cu above 0.01% by mass and 1.0% by mass Cu, 0.01% by mass and 1.0% by mass Mn, 0.01% by mass and 1.0% by mass Cr, and 0.01% by mass and 1.0% by mass At least one element selected from the group consisting of Ti. That is, the outer layers 26, 35, and 45 may include Mg of 1% by mass to 20% by mass, and element M (at least one of Si, Fe, Cu, Mn, Cr, and Ti) of 0.01% by mass to 1.0% by mass. Element) and the remainder is composed of aluminum and unavoidable impurities. In addition, the inner layers 25, 34, and 44 may be composed of Zn containing 1% by mass to 20% by mass and the aforementioned element M of 0.01% by mass to 1.0% by mass, and the remaining portion is aluminum and unavoidable impurities. By. Also, the outer layers 26, 35, 45 and the inner layers 25, 34, and 44 may contain one element of the aforementioned group, or may contain plural elements.

These elements added to the outer layers 26, 35, 45 and the inner layers 25, 34, 44 reduce the anode reaction rate of aluminum, thereby reducing the consumption rate of the films 22, 32, and 42. However, if the content of these elements is excessive, the corrosion potential will increase, and as a result, the sacrificial corrosion resistance of the coatings 22, 32, and 42 may decrease. Therefore, the content of Si, Fe, Cu, Mn, Cr, and Ti is adjusted to 0.01 mass% or more and 1.0 mass% or less.

In the first embodiment, the case where the aluminum alloy member of the present invention is applied to the members such as the heat transfer tube 13, the lower header 14 and the groove 12 has been described. However, it is not limited to this, and at least one of the members may be used. The aluminum alloy member to which the present invention is applied. That is, one of the members in the heat transfer tube 13, the lower gas collecting tube 14, and the groove 12 includes an outer layer formed of an Al-Mg-based alloy (Mg: 1 to 20% by mass) and an Al-Zn-based alloy. (Zn: 1 to 20% by mass) The film formed of the two-layer structure of the inner layer may be formed on the surface of the substrate.

In the first embodiment, the thickness of the coating films 22, 32, and 42 may be less than 100 μm, and may be slightly more than 1,000 μm.

In the first embodiment, the case where the substrates 21, 31, and 41 are composed of 3000-series, 5000-series, or 6000-series aluminum alloys has been described. However, other types such as 2000-series and 7000-series may be used. Made of aluminum alloy.

In the first embodiment described above, with regard to thermal spraying, In the case where the films 22 and 32 are formed on the surfaces of the substrates 21 and 31 to produce the heat transfer tube 13 and the lower gas collecting tube 14, the method is not limited to this, and a method of forming a clad tube by extrusion or the like may be used. In this way, in the case of manufacturing by a clad tube, the adhesion between the substrates 21 and 31 and the coatings 22 and 32 can be further improved.

In addition, in the case where the heat transfer tube 13 and the lower gas collecting tube 14 are separately produced by a clad tube, and the tubes are combined to manufacture the heat transfer tube panel 11, it is necessary to collect the heat transfer tube 13 and the lower portion by welding or the like. The trachea 14 is joined. In this case, at the lower end of the heat transfer tube 13, it is necessary to remove the fins 24, and at this time, the film 22 is also removed. Therefore, after the lower end of the heat transfer tube 13 is joined to the lower gas collecting tube 14 by welding, it is necessary to further form a coating 22 (inner layer 25 and outer layer 26) on the welded portion by thermal spraying.

<Embodiment 2>

Next, a liquefied natural gas (LNG) gasifier 2 according to Embodiment 2 of the present invention will be described with reference to FIG. 8. The liquefied natural gas (LNG) gasifier 2 is an intermediate medium gasifier (IFV) that performs heat exchange through an intermediate medium 61 having a boiling point and a freezing point between the temperature of the seawater as the heating source and the temperature of the LNG. The liquefied natural gas (LNG) gasifier 2 includes an intermediate medium evaporation section 51, a gasification section 52, and an NG heating section 53.

The intermediate medium evaporation portion 51 is a bottom portion in the casing 70 and includes a plurality of (three in this embodiment) heat transfer tubes 71 arranged in the casing space on the bottom side. The intermediate medium evaporation portion 51 is a seawater 72 flowing inside the heat transfer tube 71 and collected on the bottom of the casing 70 Heat exchange of the liquid intermediate medium 61. By this heat exchange, the liquid intermediate medium 61 is evaporated, and an intermediate medium gas 61A is generated. That is, the heat transfer tube 71 is a heat transfer member for performing heat exchange between the seawater 72 and the intermediate medium 61.

The gasification unit 52 is an upper portion in the casing 70 and includes an LNG pipe 73 including a flow path through which LNG flows as shown by an arrow in FIG. 8. The gasification unit 52 performs heat exchange between the LNG flowing through the LNG pipe 73 and the intermediate medium gas 61A. As a result, LNG is gasified to produce NG. The NG is sent to the NG heating section 53 through the NG pipe 74. In addition, the intermediate medium gas 61A is condensed by heat exchange with LNG, and is collected as a liquid intermediate medium 61 on the bottom inside the casing 70.

The NG warming unit 53 is a heat transfer tube 81 having a plurality of (three in this embodiment) seawater flowing through a micro-heating source. The NG heating unit 53 is transported from the gasification unit 52 through the NG pipe 74, and the NG exchanges heat with the seawater 72 flowing inside the heat transfer pipe 81. Then, the NG heated by the seawater is discharged as a normal temperature gas. That is, the heat transfer tube 81 is a heat transfer member for performing heat exchange between the seawater 72 and NG.

In the aforementioned liquefied natural gas (LNG) gasifier 2, the inner surfaces of the heat transfer tubes 71 and 81 are exposed to seawater 72 of a corrosive medium. Therefore, if an anti-corrosion film is not formed, there are problems such as the occurrence of pitting corrosion due to the progress of corrosion. Here, the heat transfer tubes 71 and 81 are constituted by the aluminum alloy member of this embodiment. That is, the heat transfer tubes 71 and 81 are formed on the surface of the substrate in the same manner as in the first embodiment, and a film composed of a two-layer structure including an outer layer having an appropriate amount of Mg and an inner layer having an appropriate amount of Zn By. Specifically, as shown in the cross-sectional view of FIG. 9, the heat transfer tubes 71 and 81 include a hollow cylindrical base material 91 in which a flow path 91A through which seawater flows is formed inside; The inner surface is formed on the entire coating film 92 in the circumferential direction. In addition, the coating film 92 includes an inner layer 93 formed to be in contact with the inner surface of the base material 91 and formed of an Al-Zn-based alloy (Zn: 1 to 20% by mass), and an inner layer formed to the inner layer 93 The two-layer structure of the outer layer 94 which is in surface contact and is formed of an Al-Mg-based alloy (Mg: 1 to 20% by mass). Therefore, even if corrosive seawater flows through the flow path 91A, the substrate 92 can be prevented from being corroded by the coating film 92, and peeling of the coating film 92 can also be prevented. Therefore, the life of the heat transfer tubes 71 and 81 can be further increased. In addition, members other than the heat transfer tubes 71 and 81 that may be corroded by being exposed to the seawater 72 may form a sacrificial anticorrosive film composed of the above-mentioned two-layer structure in the same manner as the heat transfer tubes 71 and 81.

<Other embodiments>

Next, another embodiment of the present invention will be described. In the aforementioned first and second embodiments, the case where the aluminum alloy member of the present invention is used as the heat transfer tubes 13, 71, 81, the lower gas collecting tube 14, and the tank 12 of the liquefied natural gas (LNG) gasifiers 1 and 2 has been described. , But not limited to this. For example, the aluminum alloy member of the present invention can also be used as a heat transfer member of a liquefied petroleum gas (LPG) gasifier, and can also be used as a heat transfer panel of a plate heat exchanger or a plate of a finned tube heat exchanger. A plate-like heat transfer member such as a fin is used.

In addition, such a plate-like aluminum alloy member can be produced by cladding rolling. Specifically, first, a base material made of aluminum alloy and a substrate Membrane materials are separately dissolved and cast, and if necessary, a homogenization heat treatment is performed to obtain respective ingots. Next, the ingot is rolled (hot rolled or cold rolled) or cut off as a whole to obtain a sheet having a desired size. Then, these sheets are stacked, and they are pressed and fixed by hot rolling to form an integrated sheet. Then, cold rolling is performed until a desired final sheet thickness is obtained, thereby producing a plate-shaped aluminum alloy with a film formed on the surface of the substrate. member. At this time, the thickness of the film can be controlled by adjusting the plate thickness of the plate corresponding to the film and the reduction ratio of hot rolling.

[Example] [Production of test materials]

The evaluation for confirming the effect of the present invention was performed on the swelling resistance and sacrificial corrosion resistance of the film of an aluminum alloy member. First, two kinds of test materials 100 and 101 shown in FIG. 10 and FIG. 11 are prepared. FIG. 10 is a test material for evaluating the swelling resistance of a coating film. It is assumed that a robust member of an aluminum alloy member is used to evaluate the initial deterioration during use. FIG. 11 is a test material for the evaluation of the sacrificial corrosion resistance, assuming that the deterioration of the aluminum alloy member progresses to some extent and the base material is exposed.

First, as a base material, those made of various aluminum alloys having a size of 50 mm (L1) x 50 mm (L2) x 20 mm (thickness) were prepared. Then, in the production of any one of the test materials 100 and 101, as a pretreatment for forming a film, a surface of 50 mm (L1) x 50 mm (L2) was oxidized so that the average roughness Ra was 10 ± 2 μm. Aluminum as The abrasive cleaning material is subjected to bead blasting treatment, and then the abrasive cleaning material is removed by brushing. In addition, by flame thermal spraying using a mixed gas of propane and oxygen, an inner layer and an outer layer were sequentially formed on the surface of the base material subjected to beading, and test materials 100 and 101 were produced. The component composition (mass%) of each element of the inner layer and the outer layer, the thickness (μm) of the inner layer and the outer layer, and the type of aluminum alloy used for the substrate are shown in Table 1 below. The composition of the inner layer and the outer layer is adjusted by the composition of the thermal spray material used.

In the production of the test material 101 (FIG. 11) for sacrificial corrosion resistance evaluation, a substrate exposed portion 100A having a circular hole with a size of 20 mmΦ was formed by cutting. In addition, on all test materials 100 and 101, the surface other than the surface forming the film with a size of 50 mm (L1) x 50 mm (L2) was sealed with Teflon (registered trademark) tape, and then supplied to the next thermal cycle Corrosion test.

[Thermal cycle corrosion test]

The following thermal cycle corrosion test was performed as a test for evaluating the corrosion resistance of members made of aluminum alloys against changes in the temperature between low and normal temperatures and the effect of corrosion on seawater. The following processes are performed once a day for a total of 6 months, that is, the surface of the test materials 100 and 101 on which the thermal spray coating is formed is subjected to artificial seawater spray adjusted to a liquid temperature of 35 ° C, and only the test material 100 The process of cooling the base material part of 101 and 101 by immersing it in liquid nitrogen. As artificial seawater, copper (II) chloride was added to aquamarine for metal corrosion test made by Yashima Co., Ltd., and the Cu ²⁺ ion concentration was 1 ppm. After the end of the corrosion test, the appearance of the test material 100 for evaluation of the swelling resistance was photographed, and the area of the expanded portion of the film was measured by image analysis.

With respect to the test material 101 for sacrificial corrosion resistance evaluation, a corrosion product was removed by immersing in 30% nitric acid at room temperature. Then, the exposed portion 100A of the substrate was observed with a laser microscope, and the depth of the local corrosion was measured by the focal depth method to obtain the deepest local corrosion depth. The corrosion consumption of the test material 101 for the evaluation of the sacrificial corrosion resistance was measured based on the weight change before and after the corrosion test. The weight after the corrosion test is the weight after removing corrosion products. The evaluation criteria of each measurement item are as follows.

[Evaluation criteria for swelling area]

：: The ratio of the expansion area to No. 1 is less than 50%.

○: The ratio of the expansion area to No. 1 is 50% or more and less than 75%.

△: The ratio of the expansion area to No. 1 is 75% or more and less than 100%.

×: The ratio of the expansion area to No. 1 is 100% or more.

[Evaluation Criteria for Corrosion Depth of the Substrate Exposed Area]

：: Local corrosion of the exposed portion of the base material was not found.

：: The maximum value of local corrosion of the exposed portion of the base material is less than 10 μm.

Δ: The maximum value of local corrosion of the exposed portion of the substrate is 10 μm or more and less than 30 μm.

×: The maximum value of local corrosion of the exposed portion of the substrate is 30 μm or more.

[Evaluation Criteria for Corrosion Consumption]

(Double-circle): The ratio of corrosion consumption to No. 1 is less than 50%.

(Circle): The ratio of corrosion consumption to No. 1 is 50% or more and less than 75%.

△: The ratio of corrosion consumption to No. 1 is 75% or more and less than 100%.

×: The ratio to the corrosion consumption of No. 1 is 100% or more.

[test results]

The results of the thermal cycle corrosion test are described in Table 1. As shown in Table 1, the Mg content in the outer layer is 1 to 20% by mass and the Zn content in the inner layer is No. 2 to 5 compared to the No. in the inner layer where only Al-Mg is formed. .1, the swelling area becomes smaller. In addition, the corrosion depth of the exposed portion of the substrate is also reduced, and the consumption of corrosion is also reduced. In addition, No. 6 to 12 containing a proper amount of Zn in the outer layer or a suitable amount of Mg in the inner layer can reduce the swelling area, suppress the depth of corrosion of the exposed portion of the substrate, and reduce the consumption of corrosion. Further improvement. In addition, No. 13 to 22 containing an appropriate amount of one or two elements of Si, Fe, Cu, Mn, Cr, and Ti in either of the outer layer and the inner layer can suppress the swelling area. The effect of reducing and reducing the consumption of corrosion is further enhanced.

The aforementioned Nos. 1 to 22 are cases where a base material made of a 7000-series aluminum alloy (A7072) is used. In Nos. 23 to 34 using a base material composed of any one of the 3000 series (A3003), 5000 series (A5083), and 6000 series (A6063), the expanded area is larger than the aforementioned Nos. 1 to 22. The effect of reducing the corrosion depth, suppressing the depth of corrosion, and reducing the consumption of corrosion are all greater.

In addition, even when a 3000-series, 5000-series, and 6000-series substrate is used, it can be obtained in the same manner as when a 7000-series substrate is used. The effect achieved by Mg and the effect achieved by containing any one of Si, Fe, Cu, Mn, Cr, and Ti in the outer layer or the inner layer. that is, The effects achieved by No. 26 to 28 containing a proper amount of Zn in the outer layer and Mg in the inner layer were greater than those of Nos. 23 to 25, respectively. Furthermore, No. 29 to 34 containing one or two elements of Si, Fe, Cu, Mn, Cr, and Ti in an appropriate amount in the outer layer or the inner layer can obtain a more excellent effect of improving corrosion resistance.

It can be known from the aforementioned thermal cycle corrosion test that even if a temperature cycle is provided in a seawater environment (1 ppm) containing a large amount of copper ions, if the aluminum alloy member according to this embodiment is used, corrosion deterioration can be prevented. . This shows that it is possible to increase the life of a liquefied natural gas (LNG) gasifier, a heat exchanger, and the like, and to reduce the maintenance load.

7‧‧‧flow

13‧‧‧ heat transfer tube

21‧‧‧ substrate

22‧‧‧ capsule

22A‧‧‧ the outermost

23‧‧‧ tube body

24‧‧‧ fins

25‧‧‧ inner layer

26‧‧‧ Outer

Claims (10)

An aluminum alloy member, comprising: a base material composed of an aluminum alloy; and a coating film formed on a surface of the base material, the coating film system comprising: an outer layer containing 1% by mass or more and 20% by mass or less And an inner layer formed between the aforementioned substrate and the aforementioned outer layer and composed of an aluminum alloy containing 1% by mass to 20% by mass of zinc. For example, the aluminum alloy member according to item 1 of the patent application scope, wherein the outer layer further contains a smaller amount of zinc than magnesium, and the inner layer further contains a smaller amount of magnesium than zinc. For example, the aluminum alloy member of item 2 of the patent application scope, wherein the magnesium content in the outer layer is greater than the magnesium content in the inner layer. For example, the aluminum alloy member according to any one of claims 1 to 3, wherein the layer of at least one of the outer layer and the inner layer further contains silicon from 0.01% by mass to 1.0% by mass, 0.01 Mass% to 1.0% by mass of iron, 0.01% by mass to 1.0% by mass of copper, 0.01% by mass to 1.0% by mass of manganese, 0.01% by mass to 1.0% by mass of chromium, and 0.01% by mass to 1.0% by mass At least one element selected from the group consisting of titanium below. For example, the aluminum alloy member according to any one of claims 1 to 3, wherein the base material is made of any one of 3000 series, 5000 series, and 6000 series aluminum alloys. For example, the aluminum alloy member according to item 4 of the patent application scope, wherein the base material is made of any one of 3000 series, 5000 series, and 6000 series aluminum alloys. For example, the aluminum alloy member according to any one of claims 1 to 3 and 6, wherein the aluminum alloy member is used in a low temperature environment of 0 ° C or lower. For example, the aluminum alloy member of the fourth item of the patent application scope, wherein the aluminum alloy member is used in a low temperature environment of 0 ° C or lower. For example, the aluminum alloy member according to any one of claims 1 to 3, 6, and 8, wherein the aluminum alloy member constitutes a heat transfer tube or a gas collecting tube as a liquefied natural gas (LNG) gasifier. A liquefied natural gas (LNG) gasifier is characterized in that it is provided with an aluminum alloy member as in any one of claims 1 to 3, 6, and 8 of the scope of patent application.