JP5144629B2 - Heat transfer tube and header tube of open rack type vaporizer - Google Patents

Heat transfer tube and header tube of open rack type vaporizer Download PDF

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JP5144629B2
JP5144629B2 JP2009269846A JP2009269846A JP5144629B2 JP 5144629 B2 JP5144629 B2 JP 5144629B2 JP 2009269846 A JP2009269846 A JP 2009269846A JP 2009269846 A JP2009269846 A JP 2009269846A JP 5144629 B2 JP5144629 B2 JP 5144629B2
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base material
sacrificial anode
anode layer
spraying
heat transfer
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JP2011112294A (en
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亘 漆原
潤一郎 衣笠
弘一 菅野
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Kobe Steel Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D3/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits
    • F28D3/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits with tubular conduits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D3/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits
    • F28D3/04—Distributing arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F28F19/004—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using protective electric currents, voltages, cathodes, anodes, electric short-circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
    • F28F19/06—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings of metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
    • F28D2021/0061—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for phase-change applications
    • F28D2021/0064—Vaporizers, e.g. evaporators

Description

本発明は、オープンラック式気化器の熱交換パネルを構成する伝熱管およびヘッダー管に関するものである。   The present invention relates to a heat transfer tube and a header tube constituting a heat exchange panel of an open rack type vaporizer.

液化天然ガス（以下、適宜ＬＮＧという）は、通常、低温高圧の液体である低温液化燃料として移送または貯蔵され、燃料として使用される前に気化される。そして、大量の低温液化燃料を効率的に気化させるために、海水の熱を利用したオープンラック式気化器（以下、適宜ＯＲＶという）が用いられる。   Liquefied natural gas (hereinafter referred to as LNG as appropriate) is usually transferred or stored as a low-temperature liquefied fuel that is a low-temperature and high-pressure liquid, and is vaporized before being used as fuel. In order to efficiently vaporize a large amount of low-temperature liquefied fuel, an open rack type vaporizer (hereinafter referred to as ORV as appropriate) using the heat of seawater is used.

図１はＯＲＶの一例を説明する部分概略図であり、（ａ）は正面図、（ｂ）は側面断面図である。図１（ａ）、（ｂ）に示すように、ＯＲＶ１０は、多数配列された伝熱管２，２，…とこれらの伝熱管２を上下端で並列に接合するヘッダー管３，４からなる熱交換パネル１をさらに複数配列して備え、これら熱交換パネル１同士の間の上部に配されて各伝熱管２の外表面に供給される海水を貯めるトラフ（堰）７、および熱交換パネル１のそれぞれのヘッダー管３，４を並列に接合するマニホールド５，６をさらに備える。低温液化燃料は、下部マニホールド５から下部ヘッダー管３を介して伝熱管２内に下端から導入される。一方、図示しない供給手段によりトラフ７に貯められた海水は、トラフ７の側縁部から溢流して伝熱管２，２，…の外表面を濡らしながら垂下する。伝熱管２内に導入された低温液化燃料は、当該伝熱管２の外部を流通する海水により加熱されて（熱交換して）気化し、伝熱管２内を上昇する。この気化した燃料は、伝熱管２の上端から上部ヘッダー管４を介して上部マニホールド６へ導出される。すなわち、ＯＲＶ１０は熱交換器の一種であり、海水との熱交換によって低温液化燃料を加熱して気化するものである。   FIG. 1 is a partial schematic diagram illustrating an example of an ORV, where (a) is a front view and (b) is a side sectional view. As shown in FIGS. 1 (a) and 1 (b), the ORV 10 is composed of heat transfer tubes 2, 2,... Arranged in large numbers and header tubes 3, 4 that join these heat transfer tubes 2 in parallel at the upper and lower ends. A plurality of exchange panels 1 are arranged, and a trough (weir) 7 is disposed in the upper part between the heat exchange panels 1 to store seawater supplied to the outer surface of each heat transfer tube 2, and the heat exchange panel 1 Are further provided with manifolds 5 and 6 for joining the respective header pipes 3 and 4 in parallel. The low-temperature liquefied fuel is introduced from the lower manifold 5 through the lower header pipe 3 into the heat transfer pipe 2 from the lower end. On the other hand, seawater stored in the trough 7 by a supply means (not shown) overflows from the side edge of the trough 7 and hangs down while wetting the outer surfaces of the heat transfer tubes 2, 2,. The low-temperature liquefied fuel introduced into the heat transfer tube 2 is heated (sealed) by seawater circulating outside the heat transfer tube 2 and vaporizes, and rises in the heat transfer tube 2. The vaporized fuel is led from the upper end of the heat transfer pipe 2 to the upper manifold 6 through the upper header pipe 4. That is, the ORV 10 is a kind of heat exchanger, and heats and vaporizes the low-temperature liquefied fuel by heat exchange with seawater.

熱交換パネル１（伝熱管２およびヘッダー管３，４）には、熱伝導性や加工性等の観点から、通常、３０００系、５０００系、６０００系等のアルミニウム合金が使用されている。しかしながら、熱交換パネル１はその外表面が海水に曝されるため、腐食し易いアルミニウム合金材では、一旦、外表面の侵食が始まるとその部分が集中的に侵されて孔食に至る虞がある。そのため、熱交換パネル１を構成するアルミニウム合金材には、その表面に防食処理を施す必要がある。特に、熱交換パネル１の下部では、内部の極低温（約−１６０℃）のＬＮＧにより外側の海水が約０℃まで冷却されているため溶存酸素濃度が高く、より厳しい腐食環境となっている。また、熱交換パネル１の外表面には、上方から大量に流れ落ちる海水が衝突し、特に熱交換パネル１の下部（伝熱管２における下部ヘッダー管３近傍）における海水の流速は４ｍ／ｓ以上と高速で、外表面を損耗させる。さらに、海水による腐食と海水の流れによるエロージョン（侵食）との相乗効果によって流れ誘起腐食（ＦＡＣ：Flow Accelerated Corrosion）が発生して、防食処理層の損耗を促進する。したがって、熱交換パネルへの防食処理は、一般的な腐食に対応する（耐食性）だけでなく、流れ誘起腐食への耐性（以下、耐ＦＡＣ性）も要求され、さらに、これらの効果がオープンラック式気化器の長時間連続運転に対応可能となるように、耐久性も要求されている。   For the heat exchange panel 1 (heat transfer tube 2 and header tubes 3 and 4), aluminum alloys such as 3000 series, 5000 series, and 6000 series are usually used from the viewpoints of thermal conductivity and workability. However, since the outer surface of the heat exchange panel 1 is exposed to seawater, in an aluminum alloy material that is easily corroded, once the erosion of the outer surface starts, the portion may be eroded intensively, resulting in pitting corrosion. is there. Therefore, the surface of the aluminum alloy material constituting the heat exchange panel 1 needs to be subjected to anticorrosion treatment. In particular, at the lower part of the heat exchange panel 1, the outer seawater is cooled to about 0 ° C. by LNG at an extremely low temperature (about −160 ° C.), so the dissolved oxygen concentration is high and the environment is more severe. . In addition, seawater flowing in large quantities from above collides with the outer surface of the heat exchange panel 1, and the flow rate of seawater in the lower part of the heat exchange panel 1 (in the vicinity of the lower header pipe 3 in the heat transfer pipe 2) is 4 m / s or more. Wear the outer surface at high speed. Furthermore, flow-induced corrosion (FAC: Flow Accelerated Corrosion) occurs due to a synergistic effect of corrosion by seawater and erosion (erosion) by the flow of seawater, thereby promoting wear of the anticorrosion treatment layer. Therefore, the anti-corrosion treatment for the heat exchange panel is required not only to cope with general corrosion (corrosion resistance) but also to resistance to flow-induced corrosion (hereinafter referred to as FAC resistance), and further, these effects are open rack. Durability is also required so that long-term continuous operation of the type vaporizer can be supported.

アルミニウム合金材への防食処理として、より電位の卑な金属を犠牲陽極として接続して、両者間の電位差によりこの犠牲陽極を優先的に金属イオンとして溶解させることでアルミニウム合金材を保護する電気防食法が挙げられる。その一例として、特許文献１に、熱交換パネルの海水に浸漬した部分にＺｎ等の電位の卑な金属を電気的に接続した流電陽極方式を用いたＯＲＶが開示されている。しかしながら、近年、ＯＲＶは、ますます高効率化が図られて装置が大型化し、長時間連続運転する傾向にある。このため、ＯＲＶを構成する部材の大型化による落下海水の流速増大や連続長時間運転に耐えるような、より高い耐食性、耐久性、信頼性が求められていて、前記従来技術の方式では海水によるエロージョンを伴うＯＲＶの熱交換パネルの防食処理としては不十分である。   As an anti-corrosion treatment for aluminum alloy materials, a metal with a lower potential is connected as a sacrificial anode, and the sacrificial anode is preferentially dissolved as metal ions by the potential difference between the two, thereby protecting the aluminum alloy material. Law. As an example, Patent Document 1 discloses an ORV using a galvanic anode method in which a base metal having a potential such as Zn is electrically connected to a portion of a heat exchange panel immersed in seawater. However, in recent years, ORV tends to operate continuously for a long period of time because the efficiency is further increased and the apparatus becomes larger. For this reason, higher corrosion resistance, durability, and reliability that can withstand the increase in the flow rate of falling seawater due to the increase in the size of the members constituting the ORV and continuous long-term operation are required. This is insufficient as an anticorrosion treatment for ORV heat exchange panels with erosion.

そこで、熱交換パネルを、アルミニウム合金材からなる基材の外表面に、より電位の卑なＡｌ−Ｚｎ合金等を被覆した構成とし、このＡｌ−Ｚｎ合金を犠牲陽極層として優先的にこの層のＺｎをイオンとして海水中に溶解させ、かつ基材を海水に接触させないことで基材を保護する熱交換パネルが開発されている。この、基材に犠牲陽極層を被覆する方法としては、基材と犠牲陽極層のクラッド材とする方法と、基材に犠牲陽極層の材料（Ａｌ−Ｚｎ合金）を溶射により被覆する方法がある。クラッド材によれば、膜厚の選択幅が大きく、強い密着性と気孔等の欠陥のない犠牲陽極層が得られる。しかしながら、組立前の板や管に形成する際にクラッド材とするため、熱交換パネルとして伝熱管とヘッダー管とを接合（溶接）する際に接合部の犠牲陽極層が除去されてしまい、接合後にこの部分に別途防食処理が必要であり、さらに、犠牲陽極層が損耗した際に修理、再生するのは困難である。一方、溶射により被覆した膜（溶射皮膜）は、組立後の複雑な構造の熱交換パネルの外表面に形成するのは容易であるが、その形成方法から、膜内部にある程度の気孔を含む構造であり、気孔を介して基材まで海水が浸入する虞がある。また、溶射皮膜は基材への密着性がクラッド材に比べて弱く、海水の流れにより剥離する虞があり、また冷却による氷結や温度差による応力で剥離や割れを生じる虞もある。さらに、犠牲陽極効果を長寿命化するべく厚膜化すると、いっそう剥離し易くなる上、１回の溶射（パス）で形成できる溶射皮膜の厚さに限界があるために、溶射パス数が増えてコストが増大する。   Therefore, the heat exchange panel has a configuration in which the outer surface of a base material made of an aluminum alloy material is coated with a lower potential Al—Zn alloy or the like, and this layer is preferentially used as a sacrificial anode layer. A heat exchange panel has been developed that protects the base material by dissolving Zn in the seawater as ions and preventing the base material from contacting the seawater. As a method of coating the sacrificial anode layer on the base material, there are a method of forming a clad material of the base material and the sacrificial anode layer, and a method of coating the base material of the sacrificial anode layer (Al—Zn alloy) by thermal spraying. is there. According to the clad material, a sacrificial anode layer having a large film thickness selection range and strong adhesion and having no defects such as pores can be obtained. However, since the clad material is used when forming the plate or tube before assembly, the sacrificial anode layer at the joint is removed when joining (welding) the heat transfer tube and the header tube as a heat exchange panel. Later, this part requires a separate anticorrosion treatment, and it is difficult to repair and regenerate the sacrificial anode layer when it is worn out. On the other hand, a film coated by thermal spraying (thermal spray coating) can be easily formed on the outer surface of a heat exchange panel having a complicated structure after assembly, but the structure includes a certain amount of pores inside the film. There is a risk that seawater may enter the base material through the pores. Further, the thermal spray coating is weaker in adhesion to the base material than the clad material, and may be peeled off by the flow of seawater, and may be peeled off or cracked by freezing due to cooling or stress due to a temperature difference. Furthermore, if the thickness of the sacrificial anode effect is increased to increase the life, it becomes easier to peel off, and the number of spraying passes increases because there is a limit to the thickness of the sprayed coating that can be formed by one spraying (pass). Cost.

その対策として、特許文献２には、溶射後に機械加工を施して溶射皮膜の表面から所定深さの領域における気孔の面積率を１０％以下に低減することにより、海水を浸入し難くして基材の腐食を抑制し、基材界面の腐食に伴う溶射皮膜の剥離を防止したＯＲＶ用のアルミニウム合金材が開示されている。また、特許文献３，４には、溶射前に基材表面をブラスト処理で所定の表面粗さに粗面化することで溶射皮膜の密着性を高くしたＯＲＶ用の伝熱管が開示されている。   As a countermeasure against this, Patent Document 2 discloses a technique that makes it difficult for seawater to enter by reducing the area ratio of pores in a region at a predetermined depth from the surface of the thermal spray coating to 10% or less by performing machining after thermal spraying. An aluminum alloy material for ORV in which corrosion of the material is suppressed and peeling of the sprayed coating accompanying corrosion at the base material interface is prevented is disclosed. Patent Documents 3 and 4 disclose ORV heat transfer tubes in which the adhesion of the thermal spray coating is increased by roughening the surface of the base material to a predetermined surface roughness by blasting before thermal spraying. .

特許第２８４３２８９号公報Japanese Patent No. 2843289 特開２００６−１８３０８７号公報JP 2006-183087 A 特開２００５−２６５３９３号公報JP 2005-265393 A 特開２００８−１１１６３８号公報JP 2008-111638 A

一般的な知見では、密着性は界面の結合状態に概ね依存し、さらに腐食環境にある場合は、腐食により界面の結合状態が劣化する。そのため、溶射法においても、前処理により界面の、すなわち基材の表面粗さを調整し、界面に隙間を形成しないこと、また腐食を促進する膜中の気孔を少なくするように、溶射皮膜が形成される。したがって特許文献２〜４に開示された従来技術によれば、耐食性や耐剥離性は向上するが、ＯＲＶ用としてそれぞれ改良の余地がある。すなわち、本発明者らは、ＯＲＶの運転環境下では、単純な腐食よりも、冷却による氷結や温度差による応力の影響が大きいことに知見した。具体的には、腐食に加えて、氷結や温度差による応力を受けることにより初期段階で溶射皮膜に微小割れが生じ、微小割れの進行と共に基材と溶射皮膜との界面割れ（局所的な剥離）が生じ、その結果、非密着領域が広がって溶射皮膜が膨れ、さらに微小割れの進行と連動して溶射皮膜の脱落に至る。   According to general knowledge, the adhesion generally depends on the bonding state of the interface, and further, in a corrosive environment, the bonding state of the interface deteriorates due to corrosion. Therefore, also in the thermal spraying method, the thermal spray coating is adjusted so that the surface roughness of the interface, that is, the surface roughness of the base material is adjusted by pretreatment so that no gaps are formed in the interface and the pores in the film that promote corrosion are reduced. It is formed. Therefore, according to the prior art disclosed in Patent Documents 2 to 4, the corrosion resistance and peel resistance are improved, but there is room for improvement for ORV use. That is, the present inventors have found that under the ORV operating environment, the influence of freezing due to cooling or stress due to a temperature difference is greater than simple corrosion. Specifically, in addition to corrosion, microcracks occur in the sprayed coating in the initial stage due to stress due to freezing and temperature differences, and as the microcracks progress, interfacial cracking between the substrate and the sprayed coating (local delamination) As a result, the non-adhesion region spreads and the sprayed coating swells, and the sprayed coating falls off in conjunction with the progress of microcracks.

本発明は、前記問題点に鑑みてなされたものであり、特にＯＲＶの運転環境下でも割れや剥離の生じ難い溶射皮膜を犠牲陽極層として被覆した伝熱管またはヘッダー管を提供することを目的とする。   The present invention has been made in view of the above-mentioned problems, and has an object to provide a heat transfer tube or a header tube in which a thermal spray coating that is not easily cracked or peeled off even in an ORV operating environment is coated as a sacrificial anode layer. To do.

本発明者らは鋭意研究した結果、溶射条件の調整にて可能な範囲で結晶子サイズや結晶配向性を制御することで、望ましい硬さとして、ＯＲＶの運転環境下でも割れや剥離の生じ難い溶射皮膜が得られることを見出した。すなわち、本発明に係るオープンラック式気化器の伝熱管またはヘッダー管は、アルミニウム合金からなる基材と、この基材の外表面の少なくとも一部に被覆されて当該基材の犠牲陽極層となるアルミニウム合金からなる厚さ１００μｍ以上の溶射皮膜とを備える。そしてこの溶射皮膜は、前記基材との界面から少なくとも１００μｍの深さまでの領域において、結晶子の長さが１８０ｎｍ以下で、Ｘ線回析法におけるアルミニウムの結晶面方位（１１１）の回析ピーク強度が結晶面方位（２００）の回析ピーク強度の１．９〜２．５倍であることを特徴とする。さらに溶射皮膜は、前記領域において、その厚さ方向の断面における気孔の面積率が１〜５％であることが好ましい。   As a result of diligent research, the present inventors have controlled the crystallite size and crystal orientation as much as possible by adjusting the thermal spraying conditions, so that cracking and peeling are less likely to occur even under an ORV operating environment as desirable hardness. It has been found that a sprayed coating can be obtained. That is, the heat transfer tube or header tube of the open rack type vaporizer according to the present invention is a sacrificial anode layer of a base material made of an aluminum alloy and coated on at least a part of the outer surface of the base material. And a sprayed coating made of an aluminum alloy with a thickness of 100 μm or more. This thermal spray coating has a diffraction peak of the crystal plane orientation (111) of aluminum in the X-ray diffraction method with a crystallite length of 180 nm or less in the region from the interface with the substrate to a depth of at least 100 μm. The intensity is 1.9 to 2.5 times the diffraction peak intensity of the crystal plane orientation (200). Furthermore, it is preferable that the area ratio of the pores in the cross section in the thickness direction of the sprayed coating is 1 to 5%.

このように、犠牲陽極層を溶射により形成して備えることで、基材を熱交換パネルに組み立てて溶接した後にその溶接部も含めて犠牲陽極層を被覆した部材とすることができる。そして、溶射皮膜の結晶組織を制御することで、ＯＲＶの運転環境下で割れや剥離の生じ難い硬さとすることができる。さらに気孔の面積率を所定範囲に限定することで、基材をいっそう腐食し難くして長寿命化の可能な犠牲陽極層となる。   Thus, by forming and providing a sacrificial anode layer by thermal spraying, it is possible to form a member that covers the sacrificial anode layer including the welded portion after the base material is assembled and welded to the heat exchange panel. And by controlling the crystal structure of the thermal spray coating, it is possible to obtain a hardness that hardly causes cracking or peeling under the ORV operating environment. Furthermore, by limiting the area ratio of the pores to a predetermined range, it becomes difficult to corrode the base material, and it becomes a sacrificial anode layer capable of extending the life.

本発明に係るオープンラック式気化器の伝熱管またはヘッダー管によれば、優れた耐食性および耐ＦＡＣ性を長期にわたって維持することができる。   According to the heat transfer tube or header tube of the open rack type vaporizer according to the present invention, excellent corrosion resistance and FAC resistance can be maintained over a long period of time.

オープンラック式気化器の一例を説明する部分概略図であり、（ａ）は正面図、（ｂ）は側面断面図である。It is the partial schematic explaining an example of an open rack type vaporizer, (a) is a front view, (b) is side sectional drawing. 本発明に係るオープンラック式気化器の伝熱管およびヘッダー管の断面の部分拡大図である。It is the elements on larger scale of the cross section of the heat exchanger tube and header tube of the open rack type vaporizer | carburetor which concerns on this invention.

以下、本発明に係るオープンラック式気化器の伝熱管またはヘッダー管を実施するための形態について、図を参照して説明する。   Hereinafter, the form for implementing the heat exchanger tube or header tube of the open rack type vaporizer | carburetor which concerns on this invention is demonstrated with reference to figures.

図１に示すように、本発明に係る伝熱管２およびヘッダー管３，４は、オープンラック式気化器（ＯＲＶ）１０の熱交換パネル１を構成するものである。熱交換パネル１（伝熱管２およびヘッダー管３，４）の外側には海水が流通し、内部にはＬＮＧ（低温液化燃料、燃料ガス）が流通する。ＯＲＶ１０のその他構造および機能は、一例として前記説明した内容と同様であるため省略する。   As shown in FIG. 1, the heat transfer tube 2 and the header tubes 3 and 4 according to the present invention constitute a heat exchange panel 1 of an open rack type vaporizer (ORV) 10. Seawater circulates outside the heat exchange panel 1 (heat transfer tube 2 and header tubes 3 and 4), and LNG (low temperature liquefied fuel, fuel gas) circulates inside. The other structures and functions of the ORV 10 are the same as those described above as an example, and are therefore omitted.

図２に示すように、伝熱管２およびヘッダー管３，４は、管形状に成形された基材２１と、この基材２１の外表面の少なくとも一部に被覆された犠牲陽極層（溶射皮膜）２２とを備える。ここで、少なくとも一部とは、ＯＲＶ１０（熱交換パネル１）において、特にＬＮＧにより低温となりかつ海水の流速が高速となる下部、すなわち下部ヘッダー管３の全体およびその近傍である伝熱管２の下部とすることが好ましい。基材２１のこの領域以外に被覆した犠牲陽極層については、後記の犠牲陽極層２２の要件を必ずしも満足しなくてもよい。そして、犠牲陽極層２２を被覆する領域において、本発明に係る伝熱管２とヘッダー管３，４とは積層構造が同じであるので、以下、適宜まとめて伝熱管２として説明する。以下に、伝熱管２を構成するこれらの要素について説明する。   As shown in FIG. 2, the heat transfer tube 2 and the header tubes 3 and 4 include a base material 21 formed into a tube shape, and a sacrificial anode layer (thermal spray coating) coated on at least a part of the outer surface of the base material 21. ) 22. Here, at least a part of the ORV 10 (heat exchange panel 1) is a lower part where the temperature of the seawater is low due to LNG and the flow rate of seawater is high, that is, the entire lower header pipe 3 and the lower part of the heat transfer pipe 2 in the vicinity thereof. It is preferable that The sacrificial anode layer coated outside this region of the substrate 21 may not necessarily satisfy the requirements for the sacrificial anode layer 22 described later. And in the area | region which coat | covers the sacrificial anode layer 22, since the laminated structure is the same as the heat exchanger tube 2 which concerns on this invention, and the header tubes 3 and 4, it is hereafter demonstrated as the heat exchanger tube 2 collectively. Below, these elements which comprise the heat exchanger tube 2 are demonstrated.

〔基材〕
基材２１は、特に限定されないが、通常、ＪＩＳ規定の３０００系、５０００系、または６０００系アルミニウム合金が用いられ、押出成形等の公知の方法で伝熱管２またはヘッダー管３，４の形状に加工される。基材２１の厚さは特に限定されないが、伝熱管２（ヘッダー管３，４）の管径や長さ等に応じて必要な強度が得られる厚さに成形される。基材２１は、伝熱管２およびヘッダー管３，４の形状にそれぞれ成形された後、溶接されて熱交換パネル１の形状に組み立てられる。なお、本発明に係る伝熱管２およびヘッダー管３，４は、それぞれ円筒形状としているが、これに限定されるものではない。 〔Base material〕
The base material 21 is not particularly limited, but usually, a JIS standard 3000 series, 5000 series, or 6000 series aluminum alloy is used, and the heat transfer pipe 2 or the header pipes 3 and 4 are shaped by a known method such as extrusion molding. Processed. Although the thickness of the base material 21 is not specifically limited, it is shape | molded by the thickness from which required intensity | strength is obtained according to the pipe diameter, length, etc. of the heat exchanger tube 2 (header pipes 3 and 4). The base material 21 is formed into the shape of the heat transfer tube 2 and the header tubes 3 and 4 and then welded to be assembled into the shape of the heat exchange panel 1. In addition, although the heat exchanger tube 2 and the header tubes 3 and 4 which concern on this invention are each made into the cylindrical shape, it is not limited to this.

また、後記の犠牲陽極層２２の形成（溶射）前に、犠牲陽極層２２との界面となる基材２１の外表面をブラスト処理等により粗面化することが好ましい。基材２１の表面が粗面化されることで、溶射皮膜である犠牲陽極層２２が剥離し難くなる。基材２１の表面性状は特に限定しないが、算術平均粗さＲａ：１５〜５０μｍ、最大高さ粗さＲｚ：１５０〜５００μｍが好ましい。   In addition, before the formation (spraying) of the sacrificial anode layer 22 described later, it is preferable to roughen the outer surface of the base material 21 serving as an interface with the sacrificial anode layer 22 by blasting or the like. When the surface of the base material 21 is roughened, the sacrificial anode layer 22 that is a sprayed coating is difficult to peel off. Although the surface property of the base material 21 is not specifically limited, Arithmetic average roughness Ra: 15-50 micrometers and maximum height roughness Rz: 150-500 micrometers are preferable.

〔犠牲陽極層〕
犠牲陽極層２２は、溶射材料として好適であり、かつ基材２１を形成するアルミニウム合金より海水中での電位が卑となる（イオン化傾向が大きい）アルミニウム合金からなる。このようなアルミニウム合金として、Ａｌ−Ｚｎ合金、Ａｌ−Ｍｇ合金、Ａｌ−Ｚｎ−Ｍｇ合金等が挙げられる。すなわち、これらの元素を単独または二種以上を添加して、基材２１を形成するアルミニウム合金の電位と比較して卑となる電位とすればよい。このようなアルミニウム合金で犠牲陽極層２２を構成することにより、犠牲陽極層２２が、腐食環境（海水中）で積極的にアノード反応（Ｍ→Ｍn+＋ｎｅ−、Ｍ：Ａｌおよび添加元素、ｎ：価数）を起こすことで、基材２１の腐食を防止する（犠牲防食）ことができる。犠牲陽極層２２は、前記成分のアルミニウム合金を、例えば線状の溶射材料（溶線材料）として、電気を熱源とするアーク溶射法やプラズマ溶射法、ガスを熱源とするフレーム溶射法等の公知の溶射方法により基材２１の表面に溶射されて形成される。 [Sacrificial anode layer]
The sacrificial anode layer 22 is made of an aluminum alloy that is suitable as a thermal spray material and has a lower potential (higher ionization tendency) in seawater than the aluminum alloy that forms the substrate 21. Examples of such an aluminum alloy include an Al—Zn alloy, an Al—Mg alloy, and an Al—Zn—Mg alloy. That is, these elements may be used alone or in combination of two or more to make a base potential as compared with the potential of the aluminum alloy forming the substrate 21. By constituting the sacrificial anode layer 22 with such an aluminum alloy, the sacrificial anode layer 22 is positively subjected to an anodic reaction (M → M n + + ne − , M: Al and an additive element, n) in a corrosive environment (in seawater). : Valence) can prevent corrosion of the base material 21 (sacrificial corrosion prevention). The sacrificial anode layer 22 is made of an aluminum alloy having the above components, for example, a linear spraying material (welding material). It is formed by thermal spraying on the surface of the substrate 21 by a thermal spraying method.

（犠牲陽極層の膜厚：１００μｍ以上）
長期にわたる犠牲防食作用を付与するために、犠牲陽極層２２の膜厚は１００μｍ以上とし、２５０μｍ以上が好ましい。一方、犠牲陽極層２２を厚くすると、熱交換効率が低下し、また剥離し易くなるため、膜厚は１０００μｍ以下が好ましく、６００μｍ以下がより好ましい。また、犠牲陽極層２２は、基材２１への密着性に特に影響の強い、基材２１との界面から少なくとも１００μｍの深さまでの領域において、以下の通り規定する。 (Sacrificial anode layer thickness: 100 μm or more)
In order to provide a sacrificial anticorrosive action for a long time, the thickness of the sacrificial anode layer 22 is set to 100 μm or more, and preferably 250 μm or more. On the other hand, if the sacrificial anode layer 22 is thickened, the heat exchange efficiency is lowered and the film is easily peeled off. Therefore, the film thickness is preferably 1000 μm or less, and more preferably 600 μm or less. The sacrificial anode layer 22 is defined as follows in a region from the interface with the base material 21 to a depth of at least 100 μm, which has a particularly strong influence on the adhesion to the base material 21.

（結晶子の長さ：１８０ｎｍ以下）
溶射皮膜である犠牲陽極層２２は多結晶膜であり、多結晶膜を構成する結晶子のそれぞれのサイズが小さいほど緻密な膜となって、冷却による氷結や温度差による応力で割れ難くなる。特に、基材２１との界面から少なくとも１００μｍの深さまでの領域において、結晶子の長さが１８０ｎｍを超えると、氷結や温度変化により犠牲陽極層２２に微小割れが生じ易い。したがって、犠牲陽極層２２は、結晶子の長さを１８０ｎｍ以下とし、１５０ｎｍ以下が好ましく、１２０ｎｍ以下がさらに好ましい。なお、結晶子の長さの下限は規定しないが、実質的には３０ｎｍ以上である。 (Crystal length: 180 nm or less)
The sacrificial anode layer 22, which is a thermal spray coating, is a polycrystalline film. The smaller the size of the crystallites constituting the polycrystalline film, the denser the film becomes, and it becomes difficult to break due to freezing due to cooling or stress due to a temperature difference. In particular, in the region from the interface with the base material 21 to a depth of at least 100 μm, if the crystallite length exceeds 180 nm, micro-cracking is likely to occur in the sacrificial anode layer 22 due to freezing or temperature change. Therefore, the sacrificial anode layer 22 has a crystallite length of 180 nm or less, preferably 150 nm or less, and more preferably 120 nm or less. In addition, although the minimum of the length of a crystallite is not prescribed | regulated, it is 30 nm or more substantially.

結晶子の大きさ（長さ）は、犠牲陽極層２２の前記深さ領域における断面または界面（表面）方向に沿った面で切断して観察面とし、Ｘ線回析法（ＸＲＤ）で解析して得られる。詳しくは、アルミニウム結晶の面方位（２００）（Ａｌ（２００））回折面で、回折プロファイルの拡がり（積分幅、ラジアン）をＸ線回折装置にて測定する。測定した回折プロファイルの拡がり（積分幅）をCauchy関数により補正し、補正した値を結晶子の大きさによる回折線の拡がり（積分幅）βとして、Scherrerの式：Ｄ＝Ｋ・λ／(β・cosθ)に導入して、結晶子の長さ（径）Ｄが算出される。なお、Ｋ：Scherrer定数、λ：測定Ｘ線波長、θ：回折線のBragg角（回折角）である。   The size (length) of the crystallite is cut by a section along the cross-section or interface (surface) direction in the depth region of the sacrificial anode layer 22 to obtain an observation surface, and is analyzed by an X-ray diffraction method (XRD). Is obtained. Specifically, the spread (integral width, radians) of the diffraction profile is measured with an X-ray diffractometer on the plane orientation (200) (Al (200)) diffraction plane of the aluminum crystal. The spread (integration width) of the measured diffraction profile is corrected by the Cauchy function, and the corrected value is defined as the diffraction line spread (integration width) β depending on the crystallite size. Scherrer's formula: D = K · λ / (β Introducing into cos θ), the length (diameter) D of the crystallite is calculated. Here, K: Scherrer constant, λ: measured X-ray wavelength, θ: Bragg angle (diffraction angle) of diffraction lines.

溶射皮膜の結晶子サイズは、溶射材料の種類、被処理物の形状、そして溶射の熱源や施工条件等に依存する。結晶子は熱に曝される時間が長いほど大きくなると考えられ、したがって、その時間を形成方法やその条件により短くすることで結晶子サイズを小さくできると考えられる。なお、熱の温度（値）の依存性すなわち材料の溶融温度の依存性は小さい。したがって、溶射皮膜においては、溶射距離（溶射装置から被処理物（基材）までの距離）が近い方が、溶射材料が高温下にある飛行時間を短縮できるため、結晶子が小さくなる。また、１回の溶射（パス）における溶射量の少ない方が、溶射材料が被処理物に接触することで早期に冷却されて熱に曝される時間が短くなるため、溶射皮膜の結晶子が小さくなる。   The crystallite size of the thermal spray coating depends on the type of thermal spray material, the shape of the workpiece, the thermal source of the thermal spray, the construction conditions, and the like. The crystallite is considered to increase as the time of exposure to heat increases. Therefore, it is considered that the crystallite size can be reduced by shortening the time depending on the forming method and the conditions. In addition, the dependence of the temperature (value) of heat, that is, the dependence of the melting temperature of the material is small. Therefore, in the thermal spray coating, the shorter the thermal spray distance (distance from the thermal spraying device to the object to be processed (base material)), the shorter the flight time when the thermal spray material is at a high temperature, the smaller the crystallite. In addition, the smaller the amount of spraying in one thermal spraying (pass), the shorter the time during which the sprayed material comes into contact with the object to be processed and is quickly cooled and exposed to heat. Get smaller.

このような知見は、通常の溶射における施工条件の考え方とは大きく異なる。溶射距離については、特に被処理物が大きく、形状が複雑な場合、例えば本発明のような熱交換パネル１の形状に組み立てられた基材２１に対しては、広い領域へ一様に溶射できることから、溶射距離を長くして、具体的には少なくとも３００ｍｍ程度とすることが一般的であった。また、近距離の溶射では被処理物に熱歪みが生じるため、溶射距離をある程度は設ける必要がある。しかし、３００ｍｍ程度またはそれ以上の溶射距離によるアルミニウム合金の溶射皮膜では、結晶子が大きくなってその長さは２００ｎｍ以上、溶射皮膜の部位やその他の施工条件によっては２５０ｎｍ以上に大きくなる。また、溶射距離を長くして一度に広い領域に溶射すると、被処理物の形状等によっては溶射領域内に溶射角度のばらつきを生じて、小さい溶射角度による溶射皮膜が形成されて好ましくない。本発明に係るＯＲＶ１０の伝熱管２およびヘッダー管３，４は、その製造について、犠牲陽極層２２（溶射皮膜）の形成における溶射条件を制限するものではないが、基材２１の熱歪みを避けつつ犠牲陽極層２２の結晶子の長さが本発明の範囲となるように、溶射距離を設定することが望ましい。具体的には溶射距離を２００ｍｍ以下とすることが好ましく、１５０ｍｍ以下とすることがより好ましく、さらに後記の他の条件を組み合わせることで、犠牲陽極層２２の結晶子の長さが本発明の範囲となるようにする。   Such knowledge is greatly different from the concept of construction conditions in normal thermal spraying. As for the spraying distance, particularly when the workpiece is large and the shape is complicated, for example, the base material 21 assembled in the shape of the heat exchange panel 1 as in the present invention can be sprayed uniformly over a wide area. Therefore, it is common to increase the spraying distance, specifically at least about 300 mm. In addition, since thermal distortion occurs in the object to be processed in short-distance spraying, it is necessary to provide a spraying distance to some extent. However, in the sprayed coating of an aluminum alloy with a spraying distance of about 300 mm or more, the crystallite becomes large and its length becomes 200 nm or more, and depending on the part of the sprayed coating and other construction conditions, it becomes 250 nm or more. Further, if the spraying distance is increased and spraying over a wide area at a time, depending on the shape of the object to be processed, the spraying angle varies in the spraying area, and a sprayed coating with a small spraying angle is formed. The heat transfer tube 2 and the header tubes 3 and 4 of the ORV 10 according to the present invention do not limit the thermal spraying conditions in the formation of the sacrificial anode layer 22 (thermal spray coating), but avoid thermal distortion of the base material 21. However, it is desirable to set the spraying distance so that the crystallite length of the sacrificial anode layer 22 falls within the range of the present invention. Specifically, the spraying distance is preferably 200 mm or less, more preferably 150 mm or less, and the crystallite length of the sacrificial anode layer 22 is within the scope of the present invention by combining other conditions described later. To be.

また、通常の溶射において１回の溶射パスでの溶射量で溶射皮膜は１５０〜２５０μｍの厚さまで形成でき、例えばそれより厚い溶射皮膜を形成する場合は、作業性やコストの観点から１回の溶射パスで膜厚が少なくとも１００μｍ程度になるような溶射量にすることが一般的であった。しかし、このような１回の溶射パスで膜厚１００μｍ程度となる溶射量では溶射皮膜の結晶子が大きくなり、例えば前記したように溶射距離を１５０ｍｍ程度に短くしても、アルミニウム合金の溶射皮膜の結晶子の長さは２００ｎｍ以上、溶射皮膜の部位やその他の施工条件によっては２５０ｎｍ以上に大きくなる。本発明に係るＯＲＶ１０の伝熱管２およびヘッダー管３，４の製造においては、所望の膜厚の犠牲陽極層２２を形成するための溶射パス数が増えて作業性が低減、またコストの増大となるものの、１回の溶射パスでの溶射量を抑えることで、犠牲陽極層２２の結晶子を小さくすることができる。したがって、前記の溶射材料の種類や被処理物（基材２１）の形状等と、溶射条件すなわち溶射距離および１回の溶射パスでの溶射量との組合せにより、犠牲陽極層２２の結晶子の大きさを本発明の範囲に抑えることが重要である。また、結晶子の大きさは、溶射皮膜（犠牲陽極層２２）において、基材２１との界面から少なくとも１００μｍの深さまでの領域で規制すればよいので、例えば、少なくとも累計１００μｍの膜厚になるまでの１〜数回目の溶射パスのみ、１回あたりの溶射量を少なく、また溶射距離を近距離として形成し、以降の溶射パスは作業性等を優先させる条件としてもよい。   Further, in normal spraying, the sprayed coating can be formed up to a thickness of 150 to 250 μm by the amount of spraying in one spraying pass. For example, when forming a thicker sprayed coating, it is possible to perform once from the viewpoint of workability and cost. Generally, the spraying amount is such that the film thickness is at least about 100 μm in the spraying pass. However, in such a spraying amount that the film thickness is about 100 μm in one spraying pass, the crystallites of the spraying coating become large. For example, even if the spraying distance is shortened to about 150 mm as described above, the spraying coating of the aluminum alloy The length of the crystallite is 200 nm or more, and increases to 250 nm or more depending on the part of the sprayed coating and other construction conditions. In the manufacture of the heat transfer tube 2 and the header tubes 3 and 4 of the ORV 10 according to the present invention, the number of spraying passes for forming the sacrificial anode layer 22 having a desired film thickness is increased, the workability is reduced, and the cost is increased. However, the crystallite of the sacrificial anode layer 22 can be reduced by suppressing the amount of spraying in one spraying pass. Therefore, the crystallites of the sacrificial anode layer 22 can be selected depending on the combination of the kind of the sprayed material, the shape of the workpiece (base material 21), and the like, and the spraying conditions, that is, the spraying distance and the spraying amount in one spraying pass. It is important to keep the size within the scope of the present invention. Further, the size of the crystallites may be regulated in a region from the interface with the base material 21 to a depth of at least 100 μm in the sprayed coating (sacrificial anode layer 22), for example, a film thickness of at least 100 μm in total. Only the first to several thermal spray passes until the spraying amount per time is small, the spraying distance is formed as a short distance, and the subsequent thermal spraying pass may be a condition for giving priority to workability and the like.

（ＸＲＤにおける結晶面方位Ａｌ（１１１）の回析ピーク強度がＡｌ（２００）の１．９〜２．５倍）
多結晶膜である犠牲陽極層２２を構成する結晶子のそれぞれは、隣接するもの同士で結晶方位が互いに異なる。アルミニウムの結晶構造は面心立方晶（ｆｃｃ）構造であるため、その結晶面方位は（１１１）および（２００）が主で、結晶配向は最緻密状態となる結晶面方位（１１１）が優先となり、その配向性が高く（結晶配向性が高く）なるほど多結晶膜の硬さが増大する。以下、アルミニウム結晶の面方位（１１１）のものをＡｌ（１１１）、面方位（２００）のものをＡｌ（２００）と表す。多結晶膜におけるＡｌ（１１１）とＡｌ（２００）の分布状態、すなわち面積比はＸＲＤにおける回析ピーク強度の比で表すことができ、前記の一般的なアルミニウム合金の溶射条件による溶射皮膜においては、Ａｌ（１１１）はＡｌ（２００）の１．７〜１．８倍の回析ピーク強度となる。本発明に係るＯＲＶ１０の伝熱管２およびヘッダー管３，４においては、溶射皮膜（犠牲陽極層２２）が従来よりも硬くなるように、Ａｌ（１１１）の回析ピーク強度をＡｌ（２００）の１．９倍以上として配向性を高くし、耐エロージョン性を向上させる。好ましくは回析ピーク強度２．１倍以上である。一方、回析ピーク強度が２．５倍を超えると、犠牲陽極層２２のＡｌ（１１１）配向性が過大となって割れ易くなるため、２．５倍以下とし、好ましくは２．４倍以下である。 (Diffraction peak intensity of crystal plane orientation Al (111) in XRD is 1.9 to 2.5 times that of Al (200))
The crystallites constituting the sacrificial anode layer 22, which is a polycrystalline film, are adjacent to each other and have different crystal orientations. Since the crystal structure of aluminum is a face-centered cubic (fcc) structure, the crystal plane orientation is mainly (111) and (200), and the crystal plane orientation (111) that gives the most dense state is preferred. The hardness of the polycrystalline film increases as the orientation becomes higher (the crystal orientation becomes higher). Hereinafter, an aluminum crystal having a plane orientation (111) is represented as Al (111) and a plane orientation (200) is represented as Al (200). The distribution state of Al (111) and Al (200) in the polycrystalline film, that is, the area ratio can be expressed by the ratio of the diffraction peak intensity in XRD. , Al (111) has a diffraction peak intensity 1.7 to 1.8 times that of Al (200). In the heat transfer tube 2 and header tubes 3 and 4 of the ORV 10 according to the present invention, the diffraction peak intensity of Al (111) is made of Al (200) so that the sprayed coating (sacrificial anode layer 22) is harder than before. 1.9 times or more increases orientation and improves erosion resistance. The diffraction peak intensity is preferably 2.1 times or more. On the other hand, if the diffraction peak intensity exceeds 2.5 times, the Al (111) orientation of the sacrificial anode layer 22 becomes excessive and easily cracked, so that it is 2.5 times or less, preferably 2.4 times or less. It is.

溶射皮膜の結晶配向性は被処理物に到達後の熱に影響されると考えられ、溶射距離を短くするとＡｌ（１１１）の配向性が高くなり、また、１回の溶射パスでの溶射量を多くすると高くなる。したがって、前記したように、溶射距離および１回の溶射パスでの溶射量の組合せにより、犠牲陽極層２２の結晶子の大きさを本発明の範囲に抑えると同時に、結晶配向性を本発明の範囲内となるように設定することが望ましい。また、溶射角度が小さいと（溶射方向を溶射面（被処理物表面）に平行に近付けると）配向性が低くなる傾向があるため、溶射角度は４５°〜９０°の範囲とすることが好ましい。   It is considered that the crystal orientation of the thermal spray coating is affected by the heat after reaching the workpiece. If the spray distance is shortened, the orientation of Al (111) increases, and the amount of thermal spray in one thermal spray pass. The more you increase, the higher. Accordingly, as described above, the crystallite size of the sacrificial anode layer 22 is suppressed within the range of the present invention by combining the spraying distance and the amount of spraying in one spraying pass, and at the same time, the crystal orientation of the present invention is reduced. It is desirable to set it within the range. Further, since the orientation tends to be low when the spray angle is small (when the spray direction is made parallel to the spray surface (surface of the workpiece)), the spray angle is preferably in the range of 45 ° to 90 °. .

（厚さ方向の断面における気孔の面積率：１〜５％）
犠牲陽極層２２は、その形成方法（溶射）から、内部にある程度の気孔２２ａを含む構造を有する。気孔２２ａは、図２の断面図ではそれぞれが分断されて示されているが、実際には他の気孔２２ａと通じているものが多い。気孔率が高い、すなわち気孔２２ａの数が多く、また１個あたりのサイズが大きくなると、複数の気孔２２ａ，２２ａ，…を介して犠牲陽極層２２の表面から基材２１との界面までが通じて、海水が基材２１の表面まで到達する虞がある。したがって、腐食の進行を抑制するために、犠牲陽極層２２は、厚さ方向の断面における気孔２２ａの面積率を５％以下とすることが好ましい。なお、この犠牲陽極層２２における気孔２２ａの面積率の上限は、基材２１との界面から１００μｍの深さまでの領域におけるものであるが、犠牲陽極層２２の全領域においてこの上限以下の面積率であることがより好ましい。一方、気孔２２ａには温度変化による犠牲陽極層２２の体積変化を緩和する働きがあるため、犠牲陽極層２２が、基材２１との界面近傍において気孔率が極度に低く、気孔２２ａの面積率が１％未満になると、氷結や温度変化により却って微小割れを生じ易くなる。したがって、犠牲陽極層２２は、基材２１との界面から少なくとも１００μｍの深さまでの領域においては、断面における気孔２２ａの面積率を１％以上とすることが好ましい。なお、犠牲陽極層２２は、形成（溶射）後に表面からエポキシ樹脂等を封孔剤として含浸させて気孔２２ａに充填してもよい。 (Area ratio of pores in cross section in thickness direction: 1 to 5%)
The sacrificial anode layer 22 has a structure including a certain amount of pores 22a inside due to its formation method (thermal spraying). In the cross-sectional view of FIG. 2, each of the pores 22a is shown as being divided, but in reality, there are many that communicate with the other pores 22a. When the porosity is high, that is, when the number of pores 22a is large and the size of each pore is large, the surface from the surface of the sacrificial anode layer 22 through the plurality of pores 22a, 22a,. Thus, there is a risk that seawater may reach the surface of the substrate 21. Therefore, in order to suppress the progress of corrosion, the sacrificial anode layer 22 preferably has an area ratio of the pores 22a in a cross section in the thickness direction of 5% or less. The upper limit of the area ratio of the pores 22 a in the sacrificial anode layer 22 is in the region from the interface with the base material 21 to a depth of 100 μm, but the area ratio below this upper limit in the entire region of the sacrificial anode layer 22. It is more preferable that On the other hand, since the pores 22a have a function of relaxing the volume change of the sacrificial anode layer 22 due to temperature change, the sacrificial anode layer 22 has an extremely low porosity in the vicinity of the interface with the substrate 21, and the area ratio of the pores 22a. If it becomes less than 1%, it becomes easy to produce a microcrack on the contrary by freezing or a temperature change. Therefore, in the sacrificial anode layer 22, the area ratio of the pores 22 a in the cross section is preferably 1% or more in a region from the interface with the base material 21 to a depth of at least 100 μm. The sacrificial anode layer 22 may be filled (filled) into the pores 22a by impregnating an epoxy resin or the like as a sealing agent from the surface after formation (thermal spraying).

犠牲陽極層２２の断面における気孔２２ａの面積率は、伝熱管２またはヘッダー管３，４を切り出した切断面を、鏡面研磨等、適宜処理して光学顕微鏡にて観察して求めればよい。気孔２２ａは空洞であっても、または封孔剤が充填されていても、犠牲陽極層２２のアルミニウム合金部分とは色調が異なって見えるため、例えば光学顕微鏡にて１００倍で撮影した写真を画像解析することによって、面積率を算出することができる。   The area ratio of the pores 22a in the cross section of the sacrificial anode layer 22 may be obtained by appropriately treating the cut surface obtained by cutting the heat transfer tube 2 or the header tubes 3 and 4 with mirror polishing or the like and observing with an optical microscope. Even if the pores 22a are hollow or filled with a sealant, the color looks different from the aluminum alloy part of the sacrificial anode layer 22, so for example, a photograph taken at 100 times with an optical microscope is taken as an image. By analyzing, the area ratio can be calculated.

溶射皮膜の気孔率も溶射条件によって変化し、例えば溶射角度を小さくすると増加する。また、溶射皮膜の表面にショットブラスト等を行って、表面近傍の気孔を機械的につぶして気孔率を低減することもできるので、１回の溶射パス後にショットブラスト等を行うことで、基材２１との界面近傍における気孔率を低減することもできる。   The porosity of the sprayed coating also changes depending on the spraying conditions, and increases, for example, when the spraying angle is reduced. In addition, by performing shot blasting etc. on the surface of the thermal spray coating, it is possible to reduce the porosity by mechanically crushing pores in the vicinity of the surface, so by performing shot blasting etc. after one spraying pass, The porosity in the vicinity of the interface with 21 can also be reduced.

以上、本発明を実施するための形態について述べてきたが、以下に、本発明の効果を確認した実施例を、本発明の要件を満たさない比較例と対比して具体的に説明する。なお、本発明はこの実施例によって制限を受けるものではなく、請求項に示した範囲で適当に変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に包含される。   As mentioned above, although the form for implementing this invention has been described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below. It should be noted that the present invention is not limited by this embodiment, and can be implemented with appropriate modifications within the scope of the claims, all of which are included in the technical scope of the present invention. The

〔供試材作製〕
伝熱管２およびヘッダー管３，４に代えて、下記の供試材を作製した。
基材として、Ａ５０８３合金の厚さ５ｍｍの板材を３５ｍｍ×１００ｍｍに切り出して用いた。基材の片面を、ショットブラスト（ブラスト粒子：アルミナ＃１６〜２０）にて算術平均粗さＲａ：２０〜４０μｍに粗面化し、この面を先端がプラスチック製のデッキブラシでこすって、目視で確認できなくなるまでブラスト粒子を除去した。この基材の粗面化された面に、Ａｌ−２％Ｚｎ合金の線材を用いて、溶線式フレーム溶射法（酸素＋プロパン炎）にて溶射皮膜を、膜厚３００μｍ程度になるように形成して犠牲陽極層とした。また、表１に示すように、溶射距離は１５０ｍｍまたは３００ｍｍ、溶射角度は９０°または４５°、１回の溶射パスで形成する溶射皮膜の膜厚は２５μｍ、５０μｍ、１００μｍとした。さらに供試材Ｎｏ．７〜９については、膜厚が１００μｍに到達するまで、１パス毎にショットブラストを実施した。１回のショットブラストにつき、１０μｍの減肉があったため、その分を考慮して溶射パス数を増やした。 [Sample preparation]
In place of the heat transfer tube 2 and the header tubes 3 and 4, the following test materials were prepared.
As a base material, a 5 mm thick plate material of A5083 alloy was cut into 35 mm × 100 mm and used. One side of the substrate is roughened with shot blasting (blast particles: alumina # 16-20) to an arithmetic average roughness Ra: 20-40 μm, and this surface is rubbed with a deck brush made of plastic and visually Blast particles were removed until no further confirmation was possible. On the roughened surface of this base material, a thermal spray coating is formed to a thickness of about 300 μm by using a wire flame spraying method (oxygen + propane flame) using an Al-2% Zn alloy wire. Thus, a sacrificial anode layer was obtained. Further, as shown in Table 1, the spraying distance was 150 mm or 300 mm, the spraying angle was 90 ° or 45 °, and the film thickness of the sprayed coating formed by one spraying pass was 25 μm, 50 μm, and 100 μm. Furthermore, sample No. For 7 to 9, shot blasting was performed for each pass until the film thickness reached 100 μm. Since there was a thickness reduction of 10 μm per shot blast, the number of thermal spray passes was increased in consideration of that amount.

（犠牲陽極層の結晶子サイズ、結晶配向性）
得られた供試材を切り出し、切断面を研磨して、この切断面から無作為に５点において、溶射皮膜（犠牲陽極層）における基材との界面から５０μｍの深さ近傍を、Ｘ線回折装置にて特性Ｘ線Ｃｕ−Ｋα（波長λ：０．１５４ｎｍ）を用いてφ１００μｍの微小部ＸＲＤ測定を実施した。Cauchy関数により補正した値を結晶子の大きさによる回折線の拡がり（積分幅）βとし、Scherrer定数Ｋを１．０５として、Scherrerの式：Ｄ＝Ｋ・λ／(β・cosθ)にて結晶子の長さＤを算出した。結晶子の長さ、およびＡｌ（１１１）／Ａｌ（２００）の回析ピーク強度比を解析し、それぞれの５点の平均値を表１に示す。 (Sacrificial anode layer crystallite size, crystal orientation)
The obtained test material was cut out, the cut surface was polished, and the surface near the depth of 50 μm from the interface with the substrate in the thermal spray coating (sacrificial anode layer) was randomly selected from the cut surface at 5 points by X-ray. Using a characteristic X-ray Cu-Kα (wavelength λ: 0.154 nm) with a diffractometer, a micro part XRD measurement of φ100 μm was performed. The value corrected by the Cauchy function is the diffraction line spread (integral width) β depending on the crystallite size, Scherrer constant K is 1.05, and Scherrer's formula: D = K · λ / (β · cosθ) The crystallite length D was calculated. The length of the crystallite and the diffraction peak intensity ratio of Al (111) / Al (200) were analyzed, and the average value of each 5 points is shown in Table 1.

（犠牲陽極層の気孔の面積率）
また、供試材の研磨した切断面を、光学顕微鏡にて１００倍で５箇所撮影した。この撮影写真に対して、画像解析ソフト（ImageJ）を用いて画像を２値化して、溶射皮膜の基材との界面から５０μｍの深さ近傍における気孔の面積率を算出し、５視野の平均値を表１に示す。 (Porosity area ratio of sacrificial anode layer)
In addition, the polished cut surface of the test material was photographed at five locations with an optical microscope at a magnification of 100 times. For this photograph, the image was binarized using image analysis software (ImageJ), and the area ratio of pores in the vicinity of a depth of 50 μm from the interface with the base material of the thermal spray coating was calculated. Values are shown in Table 1.

〔評価〕
（熱サイクル試験）
ＯＲＶとして海水中で運転した場合の熱サイクルを含めた環境を再現するため、各仕様５枚の供試材に対して以下の試験を行った。塩水噴霧試験装置にて、供試材の溶射皮膜の形成面へ、塩水の噴霧を２３時間行った後、濡れた状態でこの面を上にしてトレイに載置し、溶射皮膜が浸からない程度に液体窒素をトレイに入れて、溶射皮膜を凍結させた。次に、溶射皮膜にＯＲＶの実機温度差による圧縮応力を付加するために、圧縮試験装置にて供試材の長辺方向に０．３８％の圧縮応力を加えた状態で５分間保持するまでを１サイクルとした。その後に塩水噴霧試験装置に戻して再び塩水を噴霧する工程から繰り返し、この試験を３ヶ月間行った。試験後、供試材を切り出し、切断面を研磨して、この面を観察面として以下の評価を行った。 [Evaluation]
(Thermal cycle test)
In order to reproduce the environment including the heat cycle when operated in seawater as an ORV, the following tests were performed on five specimens of each specification. After spraying salt water for 23 hours on the spray coating surface of the test material in the salt spray test apparatus, the surface is placed on the tray in a wet state, and the spray coating is not immersed. Liquid nitrogen was put in a tray to the extent to freeze the spray coating. Next, in order to apply a compressive stress due to the actual temperature difference of the ORV to the sprayed coating, until the sample is held for 5 minutes in a state where a compressive stress of 0.38% is applied in the long side direction of the test material in the compression test apparatus Was one cycle. Thereafter, the test was repeated from the step of returning to the salt spray test apparatus and spraying salt water again, and this test was conducted for 3 months. After the test, the test material was cut out, the cut surface was polished, and the following evaluation was performed using this surface as an observation surface.

（割れの観察）
供試材の切断面を光学顕微鏡にて４００倍で観察して、割れと判別できるものの有無を評価した。直線距離１０μｍ以上の割れが存在しないものを合格とし、さらに２．５μｍ以上の割れが存在するものを△、存在しないものを○とし、また不合格を×として、表１に示す。 (Observation of cracks)
The cut surface of the test material was observed at 400 times with an optical microscope, and the presence or absence of what could be identified as a crack was evaluated. Table 1 shows a case where a crack having a linear distance of 10 μm or more does not exist as a pass, a case where a crack of 2.5 μm or more is present is Δ, a case where there is no crack is ◯, and a case where a crack is not present is ×.

（界面剥離の観察）
溶射皮膜の基材との界面を含む１ｍｍ×１ｍｍの視野範囲を、光学顕微鏡にて４００倍で観察して、間隔１０μｍの格子点法により各格子点にて界面の密着、非密着を判定した。ここで、非密着の点の３つ隣の格子点までに非密着の点が存在した場合は、この非密着の２点間における格子点も非密着点としてカウントする。非密着点数／全格子点数を非密着界面率とした。界面を視野に平行とすれば、全格子点を１００点として評価できる。各仕様について無作為の５視野を観察してその平均を表１に示す。非密着界面率が３０％を超えると、実機でも早期に剥離することがわかっていることから、非密着界面率が３０％以下を合格とする。 (Observation of interface peeling)
A field of view of 1 mm × 1 mm including the interface with the base material of the thermal spray coating was observed 400 times with an optical microscope, and adhesion / non-adhesion of the interface was determined at each lattice point by a lattice point method with an interval of 10 μm. . Here, when a non-contact point exists up to three lattice points adjacent to the non-contact point, the lattice point between the two non-contact points is also counted as a non-contact point. The number of non-adhering points / the total number of lattice points was defined as the non-adhering interface ratio. If the interface is parallel to the field of view, all lattice points can be evaluated as 100 points. Table 1 shows the average of 5 random fields observed for each specification. If the non-adhesion interface ratio exceeds 30%, it is known that the actual machine peels off early, and therefore the non-adhesion interface ratio is 30% or less.

Figure 0005144629
Figure 0005144629

表１に示すように、溶射条件を変化させることで、溶射皮膜の結晶子サイズおよび結晶配向性を制御して、本発明の要件を満足する多結晶膜の犠牲陽極層を被覆することができた。そして、このような犠牲陽極層を備えた実施例である供試材Ｎｏ．１，２，４，５，７，８は、良好な耐剥離性を示した。ただし、供試材Ｎｏ．４，５は、犠牲陽極層が気孔を多く含むため、熱サイクル試験により基材表面（界面）の腐食に至り、耐剥離性の低下が観察された。また、犠牲陽極層の基材との界面近傍における気孔を極端に少なくした供試材Ｎｏ．７は、他の実施例よりも犠牲陽極層が割れ易い傾向が見られた。これに対して、犠牲陽極層の結晶子が大きい供試材Ｎｏ．３，６，９〜１１は、熱サイクル試験により基材との界面近傍で割れを生じて剥離に至り、特に結晶配向性の低い供試材Ｎｏ．１０，１１は剥離が著しいものとなった。   As shown in Table 1, the sacrificial anode layer of the polycrystalline film satisfying the requirements of the present invention can be coated by controlling the crystallite size and crystal orientation of the sprayed coating by changing the spraying conditions. It was. And sample material No. which is an Example provided with such a sacrificial anode layer. 1, 2, 4, 5, 7, and 8 showed good peeling resistance. However, the test material No. In Nos. 4 and 5, since the sacrificial anode layer contained many pores, the thermal cycle test resulted in corrosion of the substrate surface (interface), and a decrease in peel resistance was observed. In addition, the test material No. 1 with extremely small pores in the vicinity of the interface with the base material of the sacrificial anode layer was used. No. 7 showed a tendency for the sacrificial anode layer to be more easily broken than in the other examples. On the other hand, the specimen No. with a large crystallite of the sacrificial anode layer. Nos. 3, 6 and 9 to 11 were cracked in the vicinity of the interface with the base material in the thermal cycle test, leading to peeling, and in particular, the test materials No. 2 with low crystal orientation. 10 and 11 showed remarkable peeling.

１０ ＯＲＶ（オープンラック式気化器）
１ 熱交換パネル
２ 伝熱管
２１ 基材
２２ 犠牲陽極層（溶射皮膜）
２２ａ 気孔
３ 下部ヘッダー管（ヘッダー管）
４ 上部ヘッダー管（ヘッダー管） 10 ORV (open rack type vaporizer)
1 Heat Exchange Panel 2 Heat Transfer Tube 21 Base Material 22 Sacrificial Anode Layer (Sprayed Coating)
22a Pore 3 Lower header pipe (header pipe)
4 Upper header tube (header tube)

Claims (2)

外表面に供給される海水との熱交換によって内部に流通する液化天然ガスを気化させるオープンラック式気化器の熱交換パネルを構成する伝熱管またはヘッダー管において、
アルミニウム合金からなる基材と、この基材の外表面の少なくとも一部に被覆されて当該基材の犠牲陽極層となるアルミニウム合金からなる厚さ１００μｍ以上の溶射皮膜と、を備え、
前記溶射皮膜は、前記基材との界面から少なくとも１００μｍの深さまでの領域において、結晶子の長さが１８０ｎｍ以下で、Ｘ線回析法におけるアルミニウムの結晶面方位（１１１）の回析ピーク強度が結晶面方位（２００）の回析ピーク強度の１．９〜２．５倍であることを特徴とするオープンラック式気化器の伝熱管またはヘッダー管。 In the heat transfer tube or header tube constituting the heat exchange panel of the open rack type vaporizer that vaporizes the liquefied natural gas circulating inside by heat exchange with seawater supplied to the outer surface,
A base material made of an aluminum alloy, and a thermal spray coating having a thickness of 100 μm or more made of an aluminum alloy that is coated on at least a part of the outer surface of the base material and serves as a sacrificial anode layer of the base material,
The thermal spray coating has a crystallite length of 180 nm or less in a region from the interface with the base material to a depth of at least 100 μm, and a diffraction peak intensity of the crystal plane orientation (111) of aluminum in the X-ray diffraction method. Is 1.9 to 2.5 times the diffraction peak intensity of the crystal plane orientation (200), a heat transfer tube or header tube of an open rack type vaporizer. 前記溶射皮膜は、前記基材との界面から少なくとも１００μｍの深さまでの領域において、その厚さ方向の断面における気孔の面積率が１〜５％であることを特徴とする請求項１に記載のオープンラック式気化器の伝熱管またはヘッダー管。   The area ratio of pores in a cross section in the thickness direction is 1 to 5% in a region from the interface with the base material to a depth of at least 100 μm. Heat transfer tube or header tube of open rack type vaporizer.
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