JPS61281856A - Treatment of heat exchanger tube of absorption refrigerator - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a heat exchanger tube of copper plated with nickel by diffusing the copper and nickel and hardening the tube by rolling or other method. CONSTITUTION:A heat exchanger tube of copper such as deoxidized copper for an absorption refrigerator using an aqueous soln. of lithium bromide or other salt is prepd. The surface of the heat exchanger tube is plated with nickel by electroless plating, electroplating or other method and the copper and nickel are diffused by heating or other method. The heat exchanger tube is then hardened by rolling, drawing or other method.

Description

【発明の詳細な説明】 （イ）産業上の利用分野 本発明は、臭化リチウム水溶液その他の塩類溶液を使用
する吸収冷凍機、吸収冷温水機、吸収ヒートポンプ等（
以下、これらを総称して吸収冷凍機という）に用いられ
る伝熱管の処理方法に関する。Detailed Description of the Invention (a) Field of Industrial Application The present invention is applicable to absorption chillers, absorption chillers/heaters, absorption heat pumps, etc. that use lithium bromide aqueous solution or other salt solutions.
The present invention relates to a method for treating heat exchanger tubes used in absorption refrigerators (hereinafter referred to collectively as absorption refrigerators).

（ロ）従来の技術 吸収冷凍機用の伝熱管には、通常、伝熱性能に秀れると
共に臭化リチウム水溶液に対する耐食性に秀れ、かつ、
加工もしや丁い脱酸鋼管が使用されている。また、例え
ば海水を吸収冷凍機の冷却水に用いる場合、表面にニッ
ケルメッキ処理を施すことによりニッケルを析出させて
その皮膜を生１１凸 ４７号公報、特開、５１−１１７３５０号公報など）が
、従来、使用されている。(b) Conventional technology Heat transfer tubes for absorption refrigerators usually have excellent heat transfer performance and corrosion resistance against lithium bromide aqueous solutions, and
Processed and deoxidized steel pipes are used. For example, when seawater is used as cooling water for an absorption refrigerator, nickel plating can be applied to the surface to precipitate nickel and form a film (such as Sei-11-Tou No. 47, Japanese Patent Application Laid-open No. 51-117350, etc.). , traditionally used.

し→　発明が解決しようとする問題点 吸収冷凍機用の伝熱管は、例えば１５０℃以上の高温の
臭化リチウム水溶液に長時間にわたってさらされる等、
腐食されやすい環境にあるので、脱酸鋼管の耐食性に限
度がある。また、鋼管にニッケル皮膜を生成した伝熱管
は例えばその曲げ加工によって皮膜の剥離を生じやすい
。このため、従来の伝熱管は腐食による破損事故を起こ
しやすい。それ故、例えば特願昭５８−２４６８１８号
明細書に記載されているように、ニッケルメッキの施さ
れた鋼管を真空雰囲気もしくは不活性ガス雰囲気で加熱
してニッケルと銅との拡散処理を施すことにより、銅と
ニッケルとの合金層を形成して耐食性を向上させたもの
を吸収冷凍機の伝熱管として用いることが提案されてい
る。かつまた、拡散処理後の伝熱管を徐々に冷−？ｆこ
とにより合金層が焼きなまされてその延性が向上するの
で、伝熱管を熱交換器に組立てる際に行なう拡管加工に
よる合金層のひび割れも生じない利点がある。→ Problems to be solved by the invention Heat exchanger tubes for absorption refrigerators are exposed to a lithium bromide aqueous solution at a high temperature of 150°C or higher for a long period of time, etc.
Since the environment is prone to corrosion, there is a limit to the corrosion resistance of deoxidized steel pipes. Further, in a heat exchanger tube in which a nickel film is formed on a steel pipe, the film is likely to peel off due to bending, for example. For this reason, conventional heat exchanger tubes are prone to damage due to corrosion. Therefore, for example, as described in Japanese Patent Application No. 58-246818, a nickel-plated steel pipe is heated in a vacuum atmosphere or an inert gas atmosphere to perform a diffusion treatment of nickel and copper. It has been proposed that an alloy layer of copper and nickel is formed to improve corrosion resistance and be used as a heat exchanger tube for an absorption refrigerator. Moreover, the heat transfer tube after the diffusion treatment is gradually cooled down. Since the alloy layer is annealed by f and its ductility is improved, there is an advantage that cracks do not occur in the alloy layer due to the tube expansion process performed when assembling the heat exchanger tube into a heat exchanger.

しかし、その反面、銅自体も焼きなまされて軟化し、伝
熱管がたわみやすくなるため、これを熱交換器に組立て
にくいという問題点がある。特に、ニッケルメッキを施
した脱酸鋼管においては、良好な拡散処理を施す必要上
、４００℃以上の加熱を行なうため、拡散処理後の焼き
なましによって管が過度に軟化する欠点をもっている。However, on the other hand, the copper itself is also annealed and softens, making the heat exchanger tubes more susceptible to bending, making it difficult to assemble them into a heat exchanger. In particular, nickel-plated deoxidized steel pipes are heated to 400° C. or higher in order to perform a good diffusion treatment, which has the disadvantage that the tube becomes excessively soft during annealing after the diffusion treatment.

本発明は、この問題点に鑑み、臭化リチウム水溶液その
他の塩類溶液に対する銅製伝熱管の耐食性を向上できる
と共に管の過度の軟化も防止できる吸収冷凍機用伝熱管
の処理方法の提供を目的としたものである。In view of this problem, an object of the present invention is to provide a method for treating heat exchanger tubes for absorption refrigerators, which can improve the corrosion resistance of copper heat exchanger tubes against aqueous lithium bromide solutions and other salt solutions, and can also prevent excessive softening of the tubes. This is what I did.

園　問題点を解決するための手段 本発明は、上記の問題点を解決する手段として、銅製伝
熱管表面にニッケルメッキ処理を施した扱銅とニッケル
との拡散処理を施し、さらにこの管の硬化処理を施す方
法を採用したものである。Means for Solving the Problems The present invention solves the above problems by performing a diffusion treatment of treated copper, which has been nickel-plated on the surface of a copper heat exchanger tube, and nickel, and further hardening the tube. This method employs a method of processing.

（ホ）作用 本発明によれば、拡散処理の作用として鋼製伝熱管の銅
とニッケル皮膜との境界近傍にこれらの合金層が形成さ
れるので、伝熱管の曲げ加工時や拡管加工時におけるニ
ッケル皮膜の剥離が防止され、臭化リチウム水溶液その
他の塩類溶液に対する伝熱管の防食性能が向上する。か
つまた、硬化処理の作用として銅製伝熱管の過度の軟化
が防止されるので、伝熱管の過度のたわみが解消されて
これを熱交換器に組立てることも容易となる。(E) Function According to the present invention, these alloy layers are formed near the boundary between the copper and nickel coatings of the steel heat exchanger tube as a result of the diffusion treatment, so that the alloy layer is formed in the vicinity of the boundary between the copper and nickel coatings of the steel heat exchanger tube, so that there is no problem during bending or expansion of the heat exchanger tube. Peeling of the nickel film is prevented, and the corrosion resistance of the heat exchanger tube against lithium bromide aqueous solution and other salt solutions is improved. Moreover, since excessive softening of the copper heat exchanger tubes is prevented as a result of the hardening treatment, excessive deflection of the heat exchanger tubes is eliminated, making it easier to assemble the tubes into a heat exchanger.

（へ）実施例 表１は本発明による銅製伝熱管のニッケルメッキ処理方
法の一実施例としての無電解メッキ浴の条件の具体例を
示したものである。(F) Example Table 1 shows a specific example of the conditions of an electroless plating bath as an example of the method for nickel plating a copper heat exchanger tube according to the present invention.

〈表１〉 表１のメッキ浴にリン脱酸鋼製伝熱管を２０分間浸漬さ
せて伝熱管表面に２．５μｍのニッケルメッキ皮膜を生
成させた。また、表１の具体例の他にメッキ浴の条件と
しては、硫酸ニッケル、炭酸ニッケル等のニッケル塩と
、次亜硫酸ナトリウム、無水亜硫酸ナトリウム等の還元
剤と、酢酸、プロピオン酸、乳酸、クエン酸等のアルカ
リ塩類から成る緩衝剤と夕含む浴組成のものが採用でき
る。<Table 1> A phosphorus-deoxidized steel heat exchanger tube was immersed in the plating bath shown in Table 1 for 20 minutes to form a nickel plating film of 2.5 μm on the surface of the heat exchanger tube. In addition to the specific examples in Table 1, the plating bath conditions include nickel salts such as nickel sulfate and nickel carbonate, reducing agents such as sodium hyposulfite and anhydrous sodium sulfite, and acetic acid, propionic acid, lactic acid, and citric acid. A bath composition containing a buffering agent consisting of an alkali salt such as the following can be adopted.

かつまた、一般的には浴ＰＨ４〜６、浴温度８５〜９０
℃、処理時間５分以上の条件が好ましい。In addition, generally the bath pH is 4 to 6 and the bath temperature is 85 to 90.
The conditions of temperature and treatment time of 5 minutes or more are preferable.

なお、生成されるメッキ膜厚さは少なくとも０．２μｍ
程度から臭化リチウム水溶液に対する耐食性を発揮する
が、１〜３０μｍ程度のメッキ膜厚さが好適である。Note that the thickness of the plating film produced is at least 0.2 μm.
The plating film exhibits corrosion resistance to aqueous lithium bromide solutions, but a plating film thickness of about 1 to 30 μm is suitable.

そして、無電解ニッケルメッキ処理においては、表面を
清浄にした鋼管を浴中に浸漬するだけの簡便な方法で浴
中の還元剤の還元作用によって鋼管表面にニッケルカＶ
析出てるので、処理の利便性が高いという利点も有して
いる。In electroless nickel plating, nickel is deposited on the surface of the steel pipe by the reducing action of the reducing agent in the bath, by simply immersing the surface-cleaned steel pipe in the bath.
Since it is precipitated, it also has the advantage of being highly convenient to process.

表２は本発明による鋼製被熱管のニッケルメッキ処理方
法の他の実施例としての電気メツキ条件の具体例を示し
たものである。Table 2 shows specific examples of electroplating conditions as another embodiment of the method for nickel plating a steel heat-receiving tube according to the present invention.

〈表２〉 表２の条件で、リン脱酸銅製伝熱管を浴中に浸漬して管
を回転させつつ１０分間の電解を行なうことにより、伝
熱管表面に約３μｍのニッケルメッキ皮膜を生成させた
。なお、電解条件として、一般的に、電流密度０．５〜
１．５Ａ／ｄゴ、電圧１゜５〜２．ＯＶ１温度２０〜３
０℃、Ｐ　Ｈ５，４〜６．０が採用できる。また、電気
ニッケルメッキ処理によれば、鋼管表面に純度の高いニ
ッケルが析出するので、耐食性を高め得る利点がある。<Table 2> Under the conditions shown in Table 2, a phosphorus-deoxidized copper heat exchanger tube was immersed in a bath and electrolyzed for 10 minutes while rotating the tube, thereby producing a nickel plating film of approximately 3 μm on the surface of the heat exchanger tube. Ta. Note that the electrolytic conditions are generally a current density of 0.5 to
1.5A/d, voltage 1°5~2. OV1 temperature 20-3
A temperature of 0°C and a pH of 5.4 to 6.0 can be adopted. Furthermore, electrolytic nickel plating has the advantage of increasing corrosion resistance since highly pure nickel is deposited on the surface of the steel pipe.

なお、メッキ処理は、無電解ニッケルメッキ処理や電気
ニッケルメッキ処理以外の方法も可能であり、例えば真
空蒸着メッキ処理方法を採用しても良い。Note that the plating process may be performed using methods other than electroless nickel plating or electrolytic nickel plating; for example, a vacuum evaporation plating method may be employed.

次に、ニッケルメッキ処理の施されたリン脱酸銅製伝熱
管を大気圧の窒素雰囲気において８００℃で１時間加熱
して銅とニッケルとの拡散処理ｌ施丁ことにより、これ
らの境界近傍に合金層を形成させた。なお、拡散処理は
窒素以外の不活性ガス雰囲気あるいは真空雰囲気中で行
なうこともできろ。そして、この伝熱管を窒素雰囲気中
でそのまま徐々に外気温まで冷却して拡散処理工程を完
了させる。このような拡散処理を施した伝熱管において
は、そのニッケル皮膜および合金層の延性が向上し、か
つ、二ｌ／ケル皮膜の伝熱管母伐〔銅〕への密着性も向
上する。なお、リン脱酸鋼管に無電解ニッケルメッキ処
理を施した場合、ニッケルメッキ皮膜中に少量のリンが
析出するものの、拡散処理を施すことによってこの皮膜
の延性を十分に向上させることもできた。Next, the nickel-plated phosphorus-deoxidized copper heat exchanger tube was heated at 800°C for 1 hour in a nitrogen atmosphere at atmospheric pressure to undergo a diffusion treatment of copper and nickel, thereby forming an alloy near the boundary between them. A layer was formed. Note that the diffusion treatment can also be performed in an inert gas atmosphere other than nitrogen or in a vacuum atmosphere. Then, the heat transfer tube is gradually cooled down to the outside temperature in a nitrogen atmosphere to complete the diffusion treatment process. In heat exchanger tubes subjected to such diffusion treatment, the ductility of the nickel coating and alloy layer is improved, and the adhesion of the 2L/Kel coating to the heat exchanger tube motherboard [copper] is also improved. Note that when electroless nickel plating is applied to phosphorus-deoxidized steel pipes, a small amount of phosphorus precipitates in the nickel plating film, but the ductility of this film could be sufficiently improved by performing a diffusion process.

そして、ニッケルメッキ処理と拡散処理の施されたリン
脱酸銅製伝熱管をレペラーで冷間圧延加工することによ
り硬化処理を施した。この硬化処理を施した上記伝熱管
においては、その表面硬さＨυが１００〜１２０となり
、かつまた、例えば管径１９ｍ、肉厚０．７ｍ、長さ２
ｍのものがたわまない程度の強さを保持することも目視
できた。Then, the phosphorus-deoxidized copper heat exchanger tube that had been subjected to the nickel plating treatment and the diffusion treatment was subjected to a hardening treatment by cold rolling with a repeller. The heat exchanger tube subjected to this hardening treatment has a surface hardness Hυ of 100 to 120, and has a tube diameter of 19 m, a wall thickness of 0.7 m, and a length of 2 m, for example.
It was also visually observed that the material with a diameter of m was strong enough not to bend.

したがって、この管！用いて熱交換器を組立てろことが
容易となる。また、銅製伝熱管をトリップル・コールド
・レデエーサーで圧延加工することによって硬化処理し
ても良く、これにより鋼管は１／４Ｈ〜ＩＨ程度に硬化
する。さらにまた、ダイスで冷間引抜加工することによ
って銅製伝熱管を硬化処理しても良い。Hence this tube! This makes it easy to assemble the heat exchanger. Further, the copper heat exchanger tube may be hardened by rolling with a triple cold reducer, whereby the steel tube is hardened to about 1/4H to IH. Furthermore, the copper heat exchanger tube may be hardened by cold drawing with a die.

表３はニッケルメッキ処理および拡散処理ならびに硬化
処理！施したリン脱酸銅製伝熱管（表面積６０ｄ）を臭
化リチウム水溶液（濃度５５％、温度６０℃）の中に５
００時間浸漬して銅およびニッケル皮膜の溶解性の結果
を示したものである。Table 3 shows nickel plating treatment, diffusion treatment, and hardening treatment! The treated phosphorus-deoxidized copper heat exchanger tube (surface area 60 d) was placed in a lithium bromide aqueous solution (concentration 55%, temperature 60°C) for 5 minutes.
The results show the solubility of copper and nickel films after immersion for 00 hours.

また、比較のためｆ、上記のいずれの処理も施していな
いリン脱酸銅製伝熱管（表面積６０ｄ）を臭化リチウム
水溶液中に浸漬して同じ条件で銅の溶解性を調べた結果
も併せて表３に示している。For comparison, f, we have also included the results of examining the solubility of copper under the same conditions by immersing a phosphorus-deoxidized copper heat exchanger tube (surface area 60 d) in an aqueous lithium bromide solution that has not been subjected to any of the above treatments. It is shown in Table 3.

〈表３〉 表３から明らかなように、上記処理を施したリン脱酸銅
製伝熱管は臭化リチウム水溶液に対する高い耐食性を示
てことが分かる。また、この伝熱管を曲げたり、拡管し
た場合にも、メッキ皮膜のひび割れや剥離も生じなかっ
た。さらにまた、この伝熱管外表面に水や臭化−リチウ
ム水溶液を滴下して目視したところ、液が管表面に拡が
って良好に濡れることも確認できた。<Table 3> As is clear from Table 3, the phosphorus-deoxidized copper heat exchanger tubes subjected to the above treatment exhibit high corrosion resistance against lithium bromide aqueous solutions. Further, even when this heat transfer tube was bent or expanded, the plating film did not crack or peel. Furthermore, when water or a lithium bromide aqueous solution was dropped onto the outer surface of the heat transfer tube and visually observed, it was confirmed that the liquid spread over the tube surface and wetted it well.

このように上記処理を施した鋼管は、伝熱性能に秀れ、
臭化リチウム水溶液その他の塩類ｍ液に対して高い耐食
性！発揮し、適度の柔軟さと硬さをもっていて加工しゃ
丁いため、吸収冷凍機用の伝熱管として好適である。Steel pipes subjected to the above treatment have excellent heat transfer performance,
High corrosion resistance against lithium bromide aqueous solution and other salt solutions! It is suitable as a heat transfer tube for absorption refrigerators because it has moderate flexibility and hardness and resists processing.

（ト）発明の効果 以上のとおり、本発明の伝熱管の処理方法によれば、メ
ッキ処理で鋼管表面にニッケル皮膜が生成され、かつ、
拡散処理で銅とニッケルとが相互に拡散してこれらの合
金層が形成されるためにメツキ皮膜の伝熱管母材（銅）
への密着の度合が向上すると共に拡散処理におけろ焼き
なまし作用でメッキ皮膜の延性も向上し、かつ、硬化処
理で伝熱管母材（銅）の過度の軟化も防止されるので、
伝熱性および臭化リチウム水溶液その他の塩類溶液に対
する耐食性に秀れ、かつ、塩類溶液や水などの濡れ性（
親和性）も良く、加工もしやすい伝熱管が得られるとい
う効果をもたらす。(g) Effects of the invention As described above, according to the heat exchanger tube treatment method of the present invention, a nickel film is generated on the surface of the steel tube by plating treatment, and
During the diffusion process, copper and nickel diffuse into each other to form an alloy layer.
This improves the degree of adhesion to the heat exchanger tube, improves the ductility of the plating film due to the annealing effect during the diffusion process, and prevents excessive softening of the heat exchanger tube base material (copper) during the hardening process.
It has excellent heat conductivity and corrosion resistance against lithium bromide aqueous solution and other salt solutions, and has excellent wettability (
This has the effect of providing a heat exchanger tube that has good affinity (compatibility) and is easy to process.

したがって、本発明の処理方法によって得られる伝熱管
は、塩類溶液を吸収液や冷却水に使用する吸収冷凍機の
熱交換器部材として、活用するのに好適である。Therefore, the heat exchanger tube obtained by the treatment method of the present invention is suitable for use as a heat exchanger member of an absorption refrigerator that uses a salt solution as an absorption liquid or cooling water.

Claims (1)

【特許請求の範囲】[Claims] （１）臭化リチウム水溶液その他の塩類溶液を使用する
吸収冷凍機用の銅製伝熱管表面に無電解ニッケルメッキ
処理、電気ニッケルメッキ処理等のニッケルメッキ処理
を施した後、銅とニッケルとの拡散処理を施し、かつ、
これら処理の施された伝熱管を圧延加工、引抜加工等の
加工により硬化処理することを特徴とした吸収冷凍機の
伝熱管の処理方法。(1) After applying nickel plating treatment such as electroless nickel plating treatment or electrolytic nickel plating treatment to the surface of copper heat transfer tubes for absorption refrigerators that use lithium bromide aqueous solution or other salt solutions, copper and nickel are diffused. treated, and
A method for treating heat exchanger tubes for an absorption refrigerator, which comprises hardening the heat exchanger tubes subjected to these treatments by processing such as rolling or drawing.