JP4102962B2 - Grooved heat transfer tube manufacturing plug - Google Patents

Description

【０００１】
【産業上の利用分野】
本発明は、内面に多数の溝状凹凸（以下、単に溝と略記）が形成された伝熱管を製造するために用いられる、溝付きプラグに関する。
【０００２】
【従来の技術】
冷凍機、空調機等の熱交換器に使用されている銅または銅合金製伝熱管には、伝熱性能を向上させるために、その内面に多数の溝が形成されている。この溝付き伝熱管の製造方法の一つとして、図２にその概念図を示すように、溝付きプラグを素管内部に挿入して、外部から押圧し、管内面に溝形状を転写する方法が知られている。
【０００３】
伝熱管製造用プラグには、従来炭化タングステン（ＷＣ）基超硬合金のうち、比較的高強度であるＷＣ平均粒度が２〜５μｍ、結合相金属であるＣｏ量が１８〜２２質量％である合金が多く用いられてきた。
【０００４】
【発明が解決しようとする課題】
しかし、上記の溝付きプラグにおいては、プラグ溝凸部の摩耗によるプラグ交換の頻度が高く、製造コスト上昇の原因となるという問題点があった。
本発明は、従来の溝付き伝熱管製造用プラグに比べ、耐摩耗性に優れた、溝付き伝熱管製造用プラグの提供を目的としている。
【０００５】
【課題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ために、ＷＣ基超硬合金からなるプラグ基材の表面に非晶質炭素被膜を被覆したものである。非晶質炭素被膜は銅との親和性が低く、また銅や銅合金に対する摩擦係数が比較的低いことから、伝熱管製造時にプラグに被加工材が凝着しにくく、かつプラグ溝凸部の摩耗を抑えることができる。
【０００６】
非晶質炭素被膜をプラグ基材の表面に被覆するには、例えば１〜１００Ｐａ程度の低圧の炭化水素ガス雰囲気中で、高周波発振器によりガスプラズマを発生させて、炭化水素ガスを分解し、一方プラグ基材に１００〜２０００Ｖのバイアス負電圧を加えることにより被覆することができる。
【０００７】
非晶質炭素被膜の厚さは０．５〜５．０μｍ程度が望ましく、０．５μｍ未満の場合は、寿命向上の効果が低く、また５．０μｍを超えると、基材との熱膨張係数差に起因する被膜中の残留応力が大きくなり、使用時に被膜が破壊または剥離しやすくなる。被膜硬さは被覆処理時の基材温度やバイアス電圧などにより変化させることができ、硬さ値は１０００〜３０００ＨＶが望ましい。１０００ＨＶ未満では被膜は軟質であり、耐摩耗効果が低い。また３０００ＨＶを超えると、被膜そのものの靭性が低下し、使用時に被膜中にクラックが生じやすくなる。
【０００８】
一方、非晶質炭素被膜と基材超硬合金との間に中間層として炭化けい素被膜を被覆することにより、基材／中間層被膜／非晶質炭素被膜間の密着力が向上し、伝熱管製造時の被膜の耐剥離性を改善することが出来る。
【０００９】
上記炭化けい素被膜の厚さは０．２〜２．０μｍ程度が望ましく、０．２μｍ未満の場合は、密着力向上の効果が低く、また２．０μｍを超えると、基材及び非晶質炭素被膜との熱膨張係数差による被膜中の残留応力が大きくなり、使用時に被膜が剥離しやすくなる。
【００１０】
また、プラグ溝部の非晶質炭素被膜の面粗さ（Ｒａ）を０．４μｍ以下とすることにより、プラグ寿命をより延長することができる。Ｒａが０．４μｍを超えると、被膜と被加工材との間の摩擦係数が大きくなり、被加工材が凝着しやすくなる。
【００１１】
さらに、非晶質炭素被膜中に１．０質量％（以下、すべて％と略記）以上、３０％以下のフッ素を含ませることにより、被膜の銅や銅合金に対する耐凝着性を向上させることができるが、１．０％未満ではフッ素添加の効果が見られず、また３０％を超えると被膜の強度が低下し、被膜が剥離しやすくなる。
【００１２】
プラグ基材はＷＣ基超硬合金よりなるが、その結合相は合金中含有量が１０〜２８％のＦｅ、Ｃｏ、Ｎｉのうちの１種または２種以上の鉄族金属とし、ＷＣの平均粒度は０．４μｍ以上、５μｍ以下で、合金硬さを１０００ＨＶ以上、１４００ＨＶ以下とするのが望ましい。これは１０００ＨＶ未満ではプラグが加工応力により塑性変形しやすくなり、また１４００ＨＶを超える場合は靭性が低下し、プラグが欠損しやすくなるためである。
【００１３】
【実施例】
以下、本発明の好適な実施例を、図面を参照して説明する。
例１）ＷＣ−１８％Ｃｏ超硬合金（ＷＣ平均粒度２．５μｍ、硬さ１１２０ＨＶ３０）を用いて、図１の概念図に示すような外径１０．０ｍｍ、長さ２０．０ｍｍの溝付き伝熱管製造用プラグを作製した。このとき溝部はＲａを０．２μｍに仕上げ加工した。プラグの表面にはまず、反応性イオンプレーティング法により、厚さ０．５μｍの炭化けい素中間被膜を被覆した。すなわち熱電子ビーム銃にて金属けい素を蒸発させ、流量２ｍｌ／ｍｉｎ、圧力１ＰａのＣＨ_４雰囲気中、基材温度１００℃、高周波出力５０Ｗ、バイアス電圧−１０００Ｖ、被覆時間０．３ｈｒにてけい素蒸気をイオン化し、炭化物として、基材表面に生成させた。次いで、プラズマＣＶＤ法により流量８０ｍｌ／ｍｉｎ、圧力１０ＰａのＣＨ_４雰囲気中で、基材温度１００℃、高周波出力５０Ｗ、バイアス電圧−１０００Ｖにて被覆時間を変えることにより、種々厚さの非晶質炭素被膜を被覆した。得られた本発明品Ｎｏ．１〜７の非晶質炭素被膜の被膜厚さ及び硬さを表１に示した。
【００１４】
ここで被膜硬さは被覆処理後の被膜表面で、微小ビッカース硬さ計（荷重、１０ｇｆ）によって測定した。この場合の硬さ測定値には、基材の硬さの影響が避けられないが、被膜のみの硬さを正確に測定することは困難であるので、便宜上これをもって被膜硬さとした。
【００１５】
上記プラグを用いて、図２の概念図に示すような伝熱管の溝転写加工を行った。すなわち被加工材は内径１０．０ｍｍ、肉厚０．４ｍｍの銅管とし、管の内面に不水溶性潤滑剤を用いて銅管１コイル（重量６トン）の溝転写加工を行った。加工後のプラグ溝凸部のＲａ及び加工に伴う摩耗量を測定し、その結果及びプラグの形状保持寿命を被覆処理なしのプラグ（Ｎｏ．８）と比較して表１に併示した。ここで形状保持寿命とは、銅管１コイルの加工時点で転写された溝形状が、コイル全長にわたって所定の公差内にある場合を１００％としたときの公差内形状維持長さのことである。
【００１６】
表１より、非晶質炭素被膜の厚さが０．５μｍ未満または５．０μｍを超えるプラグ（Ｎｏ．６、７）は、被覆処理なしのプラグよりも優れるものの、いずれも被膜の消失や剥離により形状保持寿命が短くなることが分かる。非晶質炭素被膜の被膜厚さが０．５〜５．０μｍの範囲内にあるプラグ（Ｎｏ．１〜５）は加工後のＲａが１μｍ以下と著しく小さく、また被膜の摩耗量も少なく、さらに使用可能であった。
【００１７】
【表１】

【００１８】
例２）基材超硬合金及び中間被膜を例１と同様にし、その後被膜厚さ約２．０μｍの非晶質炭素被膜を被覆したプラグを作製した。この時、基材温度および／またはバイアス電圧を変化させて非晶質炭素被膜の硬さを種々変化させた。得られた非晶質炭素被膜の硬さ、及び例１と同様に銅管１コイルの転写加工を行った後のプラグ溝凸部のＲａ、摩耗量及びプラグの形状保持寿命を表２に示した。被膜硬さが１０００〜３０００ＨＶの範囲内にあるプラグ（Ｎｏ．９〜１２）は加工後のＲａが１μｍ以下と小さく、なお使用可能であったが、被膜硬さが低いプラグ（Ｎｏ．１３）ではＲａの劣化が速く、摩耗量も多くなり、また被膜硬さが高いプラグ（Ｎｏ．１４）では被膜の一部が剥離し、溝部への銅の付着が起こり、いずれも形状保持寿命が短くなった。
【００１９】
【表２】

【００２０】
例３）例１と同様の超硬合金を基材として、中間被膜の被覆時間を変化させ、その他の被覆条件は例１と同様にして、種々厚さの炭化けい素中間被膜及び被膜厚さ約２．０μｍの非晶質炭素被膜を被覆したプラグを作製した。得られた中間被膜の厚さ及び例１と同様に銅管１コイルの転写加工を行った後のプラグ溝凸部のＲａ、摩耗量及びプラグの形状保持寿命を表３に示した。
【００２１】
中間被膜厚さが０．２μｍ以上、２．０μｍ未満の範囲内にあるプラグ（Ｎｏ．１５〜１７）は、加工後のＲａが１μｍ以下と著しく小さく、また被膜の摩耗量も少なくさらに使用可能であった。
一方、中間被膜無しのプラグ（Ｎｏ．１８）及び中間被膜厚さが２．０μｍ以上のプラグ（Ｎｏ．１９）は、いずれも銅管１コイルに達する前に被膜が剥離し、寿命に達した。
【００２２】
【表３】

【００２３】
例４）例１と同様の超硬合金を基材として用い、基材の仕上げ面粗さ（Ｒａ）を種々変化させ、被膜面粗さ（Ｒａ）の異なるプラグを作製した。被覆条件は例１と同様とし、炭化けい素中間被膜の厚さは０．５μｍ、非晶質炭素被膜の厚さはすべて２．０μｍとした。得られた被膜のＲａとこれらを用いて例１と同様に銅管１コイルの転写加工を行った後の溝凸部のＲａ、摩耗量及び形状保持寿命を表４に示した。非晶質炭素被膜のＲａが０．４μｍ以下であるプラグ（Ｎｏ．２０〜２２）は、使用後のＲａが０．５μｍ以下と著しく小さく、なお使用可能であった。被膜Ｒａが大きい場合（Ｎｏ．２３〜２５）は、いずれもプラグ溝への被加工材の付着が起こり、溝凸部の摩耗量も多くなり、形状保持寿命も比較的短かった。
【００２４】
【表４】

【００２５】
例５）例１と同様の超硬合金を基材として、例１と同様に被膜厚さ０．５μｍの炭化けい素中間被膜を被覆した。その後続けて、ＣＨ_４及びＣＦ_４ガスを用いて例１と同様の条件で、被膜中にフッ素を含む被膜厚さ２．０μｍの非晶質炭素被膜を被覆した。この時、ＣＨ_４／ＣＦ_４比を種々変化させ、得られた非晶質炭素被膜の被膜中フッ素量被膜硬さ及び例１と同様に銅管１コイルの転写加工を行った後のプラグ溝凸部のＲａ、摩耗量及びプラグの形状保持寿命を表５に示した。被膜中フッ素量が１．０％以上、３０％以下であるプラグ（Ｎｏ．２７〜３０）は、Ｒａが０．３μｍと、フッ素を含まない例１で示した本発明品３に比べ、加工後のＲａ及び摩耗量が小さく、なお使用可能であった。被膜中フッ素量が１．０％未満であるプラグ（Ｎｏ．２６）では、Ｒａ及び摩耗量は本発明品３と同程度であった。また被膜中フッ素量が３０％を超える場合（Ｎｏ．３１）は、転写加工中に被膜の剥離が発生した。このことから、非晶質炭素被膜中に１．０％以上、３０％以下のフッ素を含ませることにより、上記プラグの耐摩耗性がさらに向上することが分かる。
【００２６】
【表５】

【００２７】
【発明の効果】
以上説明したように、超硬合金基材に非晶質炭素被膜をプラズマ被覆した本発明の伝熱管製造用溝付きプラグは、優れた溝形状転写性を示すとともに、高耐摩耗性を有することにより、被加工材の品質が向上するとともに、プラグの寿命が長くなり、工業上極めて有益である。
【図面の簡単な説明】
【図１】本発明に係わる伝熱管製造用の溝付きプラグの概念図である。
【図２】本発明に係わる伝熱管の内面溝転写加工の概念図である。
【符号の説明】
１ プラグ外周部
２ プラグ溝部
３ 溝付きプラグ
４ 銅管
５ 押圧ボール
６ ダイス
７ フローティングプラグ[0001]
[Industrial application fields]
The present invention relates to a grooved plug used for manufacturing a heat transfer tube having an inner surface formed with a large number of groove-shaped irregularities (hereinafter simply referred to as grooves).
[0002]
[Prior art]
In order to improve heat transfer performance, copper or copper alloy heat transfer tubes used in heat exchangers such as refrigerators and air conditioners have a large number of grooves formed on the inner surface thereof. As a manufacturing method of this grooved heat transfer tube, as shown in the conceptual diagram in FIG. 2, a grooved plug is inserted into the raw tube, pressed from the outside, and the groove shape is transferred to the inner surface of the tube. It has been known.
[0003]
In the plug for heat transfer tube production, among the conventional tungsten carbide (WC) based cemented carbide, the WC average particle size, which is relatively high strength, is 2-5 μm, and the amount of Co which is a binder phase metal is 18-22 mass%. Many alloys have been used.
[0004]
[Problems to be solved by the invention]
However, the above-mentioned grooved plug has a problem that the frequency of plug replacement due to wear of the plug groove convex portion is high, which causes an increase in manufacturing cost.
SUMMARY OF THE INVENTION An object of the present invention is to provide a grooved heat transfer tube manufacturing plug that is superior in wear resistance compared to a conventional grooved heat transfer tube manufacturing plug.
[0005]
[Means for Solving the Problems]
In the present invention, in order to solve the above-described problems, the surface of a plug base material made of a WC-based cemented carbide is coated with an amorphous carbon film. Amorphous carbon coating has a low affinity with copper and a relatively low coefficient of friction against copper and copper alloys, making it difficult for the work material to adhere to the plug during the manufacture of heat transfer tubes. Wear can be suppressed.
[0006]
In order to coat the surface of the plug base material with an amorphous carbon coating, for example, gas plasma is generated by a high frequency oscillator in a low pressure hydrocarbon gas atmosphere of about 1 to 100 Pa to decompose the hydrocarbon gas, It can coat | cover by applying a bias negative voltage of 100-2000V to a plug base material.
[0007]
The thickness of the amorphous carbon coating is desirably about 0.5 to 5.0 μm. When the thickness is less than 0.5 μm, the effect of improving the life is low, and when it exceeds 5.0 μm, the coefficient of thermal expansion with the base material Residual stress in the coating due to the difference is increased, and the coating is easily broken or peeled off during use. The coating hardness can be changed by the substrate temperature, bias voltage, etc. during the coating treatment, and the hardness value is preferably 1000 to 3000 HV. Below 1000 HV, the coating is soft and has a low wear resistance effect. On the other hand, if it exceeds 3000 HV, the toughness of the coating itself is lowered, and cracks tend to occur in the coating during use.
[0008]
On the other hand, by coating a silicon carbide coating as an intermediate layer between the amorphous carbon coating and the substrate cemented carbide, the adhesion between the substrate / intermediate coating / amorphous carbon coating is improved, It is possible to improve the peel resistance of the coating during the production of the heat transfer tube.
[0009]
The thickness of the silicon carbide film is preferably about 0.2 to 2.0 μm. When the thickness is less than 0.2 μm, the effect of improving the adhesion is low. Residual stress in the coating increases due to the difference in thermal expansion coefficient from the carbon coating, and the coating is easily peeled off during use.
[0010]
Moreover, the plug life can be further extended by setting the surface roughness (Ra) of the amorphous carbon coating in the plug groove to 0.4 μm or less. When Ra exceeds 0.4 μm, the coefficient of friction between the coating and the workpiece increases, and the workpiece tends to adhere.
[0011]
Furthermore, by adding 1.0% by mass (hereinafter abbreviated as “%”) to 30% or less fluorine in the amorphous carbon film, the adhesion resistance of the film to copper or copper alloy is improved. However, if it is less than 1.0%, the effect of fluorine addition is not observed, and if it exceeds 30%, the strength of the film is lowered and the film is easily peeled off.
[0012]
The plug base material is made of a WC-based cemented carbide, and the binder phase is made of one or more iron group metals of Fe, Co and Ni having a content in the alloy of 10 to 28%, and the average of WC It is desirable that the particle size is 0.4 μm or more and 5 μm or less, and the alloy hardness is 1000 HV or more and 1400 HV or less. This is because if the plug is less than 1000 HV, the plug is likely to be plastically deformed by processing stress, and if it exceeds 1400 HV, the toughness is lowered and the plug is likely to be broken.
[0013]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Example 1) Using a WC-18% Co cemented carbide (WC average grain size 2.5 μm, hardness 1120HV30), with a groove having an outer diameter of 10.0 mm and a length of 20.0 mm as shown in the conceptual diagram of FIG. A plug for manufacturing a heat transfer tube was produced. At this time, the groove was finished to Ra of 0.2 μm. The surface of the plug was first coated with a silicon carbide intermediate coating having a thickness of 0.5 μm by a reactive ion plating method. That is, metal silicon is evaporated by a thermionic beam gun, and the substrate temperature is 100 ° C., the high frequency output is 50 W, the bias voltage is −1000 V, and the coating time is 0.3 hr in a CH ₄ atmosphere at a flow rate of 2 ml / min and a pressure of 1 Pa. The elementary vapor was ionized and generated as carbide on the surface of the substrate. Next, by changing the coating time at a base material temperature of 100 ° C., a high-frequency output of 50 W, and a bias voltage of −1000 V in a CH ₄ atmosphere at a flow rate of 80 ml / min and a pressure of 10 Pa by plasma CVD, amorphous films of various thicknesses are obtained. A carbon coating was applied. The obtained product No. Table 1 shows the film thickness and hardness of the amorphous carbon coatings 1-7.
[0014]
Here, the film hardness was measured with a micro Vickers hardness meter (load, 10 gf) on the surface of the film after the coating treatment. The hardness measurement value in this case is unavoidably affected by the hardness of the base material, but it is difficult to accurately measure the hardness of only the coating film.
[0015]
Using the plug, the groove transfer processing of the heat transfer tube as shown in the conceptual diagram of FIG. 2 was performed. That is, the material to be processed was a copper tube having an inner diameter of 10.0 mm and a wall thickness of 0.4 mm, and a groove transfer process of one coil of copper tube (weight 6 tons) was performed on the inner surface of the tube using a water-insoluble lubricant. Ra of the plug groove protrusion after processing and the amount of wear accompanying the processing were measured, and the results and the shape retention life of the plug are shown in Table 1 in comparison with the plug (No. 8) without coating treatment. Here, the shape retention life is the in-tolerance shape maintaining length when the groove shape transferred at the time of machining the copper tube 1 coil is within a predetermined tolerance over the entire length of the coil as 100%. .
[0016]
From Table 1, although plugs (Nos. 6 and 7) with an amorphous carbon coating thickness of less than 0.5 μm or more than 5.0 μm are superior to plugs without coating treatment, they all disappear or peel off. It can be seen that the shape retention life is shortened. Plugs (Nos. 1 to 5) in which the film thickness of the amorphous carbon film is in the range of 0.5 to 5.0 μm are extremely small with a Ra after processing of 1 μm or less, and the amount of wear of the film is small, Further usable.
[0017]
[Table 1]

[0018]
Example 2) A base cemented carbide and an intermediate coating were prepared in the same manner as in Example 1, and then a plug coated with an amorphous carbon coating having a thickness of about 2.0 μm was prepared. At this time, the hardness of the amorphous carbon film was changed variously by changing the substrate temperature and / or the bias voltage. Table 2 shows the hardness of the obtained amorphous carbon coating and the Ra, wear amount, and plug shape retention life of the plug groove protrusion after the transfer processing of the copper tube 1 coil as in Example 1. It was. Plugs with a coating hardness in the range of 1000 to 3000 HV (Nos. 9 to 12) had a small Ra of 1 μm or less after processing and could still be used, but plugs with a low coating hardness (No. 13) In the case of plugs with high coating hardness (No. 14), a part of the coating peels off and copper adheres to the groove, and the shape retention life is short. became.
[0019]
[Table 2]

[0020]
Example 3) Using the same cemented carbide as in Example 1 as the base material, changing the coating time of the intermediate coating, and the other coating conditions were the same as in Example 1, with various thicknesses of silicon carbide intermediate coating and film thickness. A plug coated with an amorphous carbon film of about 2.0 μm was prepared. Table 3 shows the thickness of the obtained intermediate coating and the Ra of the groove of the plug groove, the wear amount, and the plug shape retention life after the copper tube 1 coil was transferred in the same manner as in Example 1.
[0021]
Plugs (No. 15 to 17) with an intermediate film thickness in the range of 0.2 μm or more and less than 2.0 μm have a very low Ra of 1 μm or less after processing, and the amount of wear on the coating is also small and can be used further. Met.
On the other hand, the plug without the intermediate coating (No. 18) and the plug with the intermediate coating thickness of 2.0 μm or more (No. 19) both reached the end of their lives because the coating peeled off before reaching the copper coil 1 coil. .
[0022]
[Table 3]

[0023]
Example 4 Using the same cemented carbide as in Example 1 as the base material, the finished surface roughness (Ra) of the base material was variously changed to produce plugs having different coating surface roughness (Ra). The coating conditions were the same as in Example 1, the thickness of the silicon carbide intermediate coating was 0.5 μm, and the thickness of the amorphous carbon coating was all 2.0 μm. Table 4 shows the Ra of the groove, the amount of wear, and the shape retention life of the groove protrusion after the obtained coating film Ra and the transfer processing of the copper tube 1 coil using these as in Example 1. The plugs (Nos. 20 to 22) in which the amorphous carbon coating had a Ra of 0.4 μm or less were extremely small, with a Ra after use of 0.5 μm or less, and were still usable. When the film Ra was large (Nos. 23 to 25), the work material adhered to the plug groove, the amount of wear of the groove convex portion was increased, and the shape retention life was relatively short.
[0024]
[Table 4]

[0025]
Example 5) A cemented carbide similar to Example 1 was used as a base material, and a silicon carbide intermediate coating having a film thickness of 0.5 μm was coated in the same manner as in Example 1. Subsequently, an amorphous carbon film having a film thickness of 2.0 μm and containing fluorine in the film was coated under the same conditions as in Example 1 using CH ₄ and CF ₄ gas. At this time, the CH ₄ / CF ₄ ratio was changed variously, the fluorine amount coating hardness in the coating of the obtained amorphous carbon coating, and the plug groove after the transfer processing of the copper tube 1 coil as in Example 1 Table 5 shows Ra, the amount of wear, and the shape retention life of the plug. Plugs (No. 27 to 30) having a fluorine content in the film of 1.0% or more and 30% or less have a Ra of 0.3 μm, compared to the product 3 of the present invention shown in Example 1 that does not contain fluorine. Later Ra and the amount of wear were small, and it was still usable. In the plug (No. 26) in which the fluorine content in the coating was less than 1.0%, Ra and the wear amount were the same as those of the product 3 of the present invention. When the fluorine content in the coating exceeded 30% (No. 31), peeling of the coating occurred during transfer processing. This shows that the wear resistance of the plug is further improved by including 1.0% or more and 30% or less of fluorine in the amorphous carbon film.
[0026]
[Table 5]

[0027]
【The invention's effect】
As explained above, the grooved plug for manufacturing a heat transfer tube according to the present invention in which a cemented carbide base material is coated with an amorphous carbon coating exhibits excellent groove shape transferability and high wear resistance. As a result, the quality of the work material is improved and the life of the plug is extended, which is extremely useful industrially.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a grooved plug for manufacturing a heat transfer tube according to the present invention.
FIG. 2 is a conceptual diagram of inner surface groove transfer processing of a heat transfer tube according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plug outer peripheral part 2 Plug groove part 3 Grooved plug 4 Copper pipe 5 Pressing ball 6 Die 7 Floating plug

Claims (5)

銅または銅合金製の管の内面に、転写加工により溝状凹凸を形成するために用いられるプラグにおいて、該プラグの外周部に非晶質炭素被膜が被覆されていることを特徴とする溝付き伝熱管製造用ＷＣ基超硬合金製プラグ。In a plug used to form groove-like irregularities on the inner surface of a copper or copper alloy tube by transfer processing, an amorphous carbon coating is coated on the outer periphery of the plug. WC-based cemented carbide plug for heat transfer tube manufacturing. 非晶質炭素被膜の厚さが０．５μｍ以上、５．０μｍ以下であり、かつ被膜の微小ビッカース硬さが１０００ＨＶ以上、３０００ＨＶ以下であることを特徴とする請求項１に記載の伝熱管製造用プラグ。2. The heat transfer tube manufacturing according to claim 1, wherein the amorphous carbon coating has a thickness of 0.5 μm or more and 5.0 μm or less, and the coating has a micro Vickers hardness of 1000 HV or more and 3000 HV or less. Plug. 非晶質炭素被膜と基材超硬合金との間に中間層として、被膜厚さが０．２μｍ以上、２．０μｍ未満である、炭化けい素被膜を被覆したことを特徴とする請求項１または２に記載の伝熱管製造用プラグ。2. A silicon carbide film having a film thickness of 0.2 μm or more and less than 2.0 μm is coated as an intermediate layer between the amorphous carbon film and the base cemented carbide. Or a plug for manufacturing a heat transfer tube according to 2; 非晶質炭素被膜表面の平均面粗さ（Ｒａ）が０．４μｍ以下であることを特徴とする、請求項１乃至３のいずれかに記載の溝付き伝熱管製造用プラグ。The plug for manufacturing a grooved heat transfer tube according to any one of claims 1 to 3, wherein an average surface roughness (Ra) of the surface of the amorphous carbon coating is 0.4 µm or less. 非晶質炭素被膜中に１．０質量％以上、３０質量％以下のフッ素を含むことを特徴とする、請求項１乃至４のいずれかに記載の溝付き伝熱管製造用プラグ。5. The grooved heat transfer tube manufacturing plug according to claim 1, wherein the amorphous carbon film contains 1.0% by mass to 30% by mass of fluorine.

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