JP2001335877A - Plug for manufacturing heat transfer tube with internal groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a plug for groove rolling used for manufacturing heat transfer tubes with internal grooves for deep groove type various heat exchangers. SOLUTION: The plug material is composed of cemented carbide in which the average particle size of WC is 0.4 to 0.8 μm. More preferably, the cemented carbide contains a bonding phase by 18 to 28 mass % and has the average deflective strength of >=3.5 GPa.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、内面に多数の溝状
凹凸（以下、単に「溝」と略記）を有する非鉄金属材料
製の各種熱交換機用伝熱管の製造に用いられる溝転造用
の溝付プラグに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove rolling method used for manufacturing heat transfer tubes for various heat exchangers made of a non-ferrous metal material having a large number of groove-like irregularities (hereinafter simply referred to as "grooves") on an inner surface. To a grooved plug.

【０００２】[0002]

【従来の技術】内面に多数の溝を有する非鉄金属材料製
の伝熱管の製造方法の一つに、非鉄金属の素管内に溝付
プラグを挿入し、プラグのある位置の素管に外部より押
圧して溝形状を転造する方法がある。この製造方法で用
いられる溝転造用の溝付プラグには、従来炭化タングス
テン−コバルト（ＷＣ−Ｃｏ）系超硬合金の内、比較的
靭性の高いＷＣ平均粒度が３〜５μｍで結合相金属とし
てのＣｏ量が１８〜２２質量％（以下、単に％と略記）
程度の粗粒ＷＣ高Ｃｏ合金が用いられてきた。これは、
加工応力に耐えるには、ある程度軟質で靭性が高くない
と、溝付プラグの溝間の凸部が欠損するためである。2. Description of the Related Art One of the methods for manufacturing a heat transfer tube made of a non-ferrous metal material having a large number of grooves on an inner surface is to insert a grooved plug into a non-ferrous metal tube and externally insert the plug into a tube at a position where the plug is located. There is a method of rolling the groove shape by pressing. The grooved plug for groove rolling used in this manufacturing method includes a relatively high toughness WC average particle size of 3 to 5 μm and a binder phase metal among conventional tungsten carbide-cobalt (WC-Co) cemented carbides. 18 to 22% by mass of Co (hereinafter simply abbreviated as%)
Some coarse WC high Co alloys have been used. this is,
This is because the protrusion between the grooves of the grooved plug is lost unless the material is soft to some extent and has high toughness to withstand the processing stress.

【０００３】[0003]

【発明が解決しようとする課題】近年、伝熱管内面の溝
の深さを従来より深く、かつ溝数を多くした深溝タイプ
の伝熱管の需要が増大してきた。これは伝熱管内面の表
面積を大きくして熱交換率を高めることが、省エネルギ
ーの観点から必須とされるようになってきたためであ
る。しかし、前述の比較的靭性の高いＷＣ粒度が３〜５
μｍでＣｏ量が１８〜２２％程度の粗粒ＷＣ高Ｃｏ合金
製のプラグを、深溝タイプの伝熱管の製造に用いると、
摩耗の進行が早く、生産性が従来の１／３以下に低下
し、採算性が著しく悪化するという問題点があった。In recent years, there has been an increasing demand for deep groove type heat transfer tubes in which the depth of the grooves on the inner surface of the heat transfer tubes is deeper and the number of grooves is larger than before. This is because it has become essential to increase the heat exchange rate by increasing the surface area of the inner surface of the heat transfer tube from the viewpoint of energy saving. However, the aforementioned relatively tough WC grain size is 3 to 5
When a plug made of a coarse-grained WC high Co alloy having a Co amount of about 18 to 22% in μm is used for manufacturing a deep groove type heat transfer tube,
There is a problem that the wear progresses quickly, the productivity is reduced to 1/3 or less of the conventional one, and the profitability is remarkably deteriorated.

【０００４】[0004]

【課題を解決するための手段】上記の問題点を解決する
ために、本発明者らは、深溝タイプの伝熱管への溝転造
用溝付きプラグに対する各種超硬合金の適性を詳細に検
討した。Means for Solving the Problems In order to solve the above problems, the present inventors have studied in detail the suitability of various cemented carbides for a grooved plug for groove rolling into a deep groove type heat transfer tube. did.

【０００５】まず、従来の比較的靭性の高いＷＣ粒度が
３〜５μｍでＣｏ量が１８〜２２％程度の粗粒ＷＣ高Ｃ
ｏ合金は、抗折力３．０ＧＰａ程度、シャルピー衝撃値
（以下、「衝撃値」と略記）８０〜９０ｋＪ／ｍ^２、硬
さ８３〜８５ＨＲＡの特性を有するが、この合金を深溝
タイプの伝熱管への溝転造に用いると、従来の１／３程
度の加工量で溝凸部が摩耗し、転造溝形状・寸法が所定
精度を満足しなくなる。すなわち、このような超硬合金
を用いたプラグでは、耐摩耗性が不足しているという第
１の知見を得た。[0005] First, a conventional coarse WC high C having a relatively high toughness WC particle size of 3 to 5 µm and a Co content of about 18 to 22%.
The o-alloy has characteristics of a transverse rupture strength of about 3.0 GPa, a Charpy impact value (hereinafter abbreviated as “impact value”) of 80 to 90 kJ / m ² , and a hardness of 83 to 85 HRA. When used for groove rolling into a heat pipe, the groove projection wears out with a processing amount of about 1/3 of the conventional one, and the shape and dimensions of the rolled groove do not satisfy the predetermined accuracy. That is, the first finding that the plug using such a cemented carbide has insufficient wear resistance.

【０００６】耐摩耗性を向上させるためには、一般的に
は、ＷＣ粒度を微細化させる、またはＣｏ量を減少させ
ることによって合金硬さを高めることが有効と考えられ
る。そこで、ＷＣ平均粒度を従来と同様に３〜５μｍと
変化させずにＣｏ量を１４〜１７％に減少させた、抗折
力３．０ＧＰａ程度、硬さ８５〜８７ＨＲＡの超硬合金
製プラグを使用したところ、耐摩耗性は多少改良された
が、伝熱管への転造時の異常振動による衝撃のためと思
われるが、プラグの溝が欠損して、加工量は目的の１／
２以下であった。欠損の原因は、本合金の衝撃値が７０
ｋＪ／ｍ^２以下と低いためと考えられ、プラグ用超硬合
金には、硬さばかりでなく衝撃値も高いことが必要であ
るという第２の知見を得た。In order to improve the wear resistance, it is generally considered effective to increase the alloy hardness by reducing the WC grain size or reducing the amount of Co. Therefore, a cemented carbide plug having a transverse rupture force of about 3.0 GPa and a hardness of 85 to 87 HRA, in which the Co content is reduced to 14 to 17% without changing the WC average particle size to 3 to 5 μm as in the past, is used. When used, the abrasion resistance was somewhat improved, but it is thought to be due to the impact due to abnormal vibration during rolling to the heat transfer tube.
2 or less. The cause of the fracture is that the impact value of this alloy is 70
This is considered to be due to the low kJ / m ² or less, and the second finding was obtained that the cemented carbide for plugs needs to have not only high hardness but also high impact value.

【０００７】そこで、次にＣｏ量は従来と同様に１８〜
２２％とし、ＷＣ平均粒度を１．５〜２．５μｍと細か
くして、衝撃値を９０ｋＪ／ｍ^２程度に上昇させた超硬
合金（硬さ８５〜８７．５ＨＲＡ、抗折力約２．８ＧＰ
ａ）で溝付きプラグを作って使用したところ、予想に反
して耐摩耗性はほとんど改良されず、かつ、プラグの溝
が欠損して実用に耐えなかった。欠損の原因は合金強さ
が不足したためと思われ、プラグ用超硬合金には、抗折
力のような静的強さも必要であるという第３の知見を得
た。[0007] Then, the amount of Co is 18 to 18 as in the past.
And 22%, WC average grain size finely and 1.5~2.5μm a cemented carbide increased the impact value of about 90 kJ / ^{m 2} (hardness 85～87.5HRA, transverse rupture strength of about 2. 8GP
When a plug with a groove was prepared and used in a), the abrasion resistance was hardly improved unexpectedly, and the groove of the plug was damaged, which was not practical. The cause of the defect is considered to be insufficient alloy strength, and the third finding was obtained that cemented carbide for plugs also needs static strength such as bending strength.

【０００８】ここで、上記のプラグの耐摩耗性がプラグ
材料の硬さと対応しなかった点について、詳細に検討し
た。プラグの耐摩耗性の評価は、転造後の伝熱管の溝形
状および寸法によって評価されるが、走査型のレーザー
顕微鏡を用いて、使用後のプラグの溝形状・寸法と面粗
さおよび伝熱管内面の溝形状・寸法を調べたところ、使
用後のプラグの溝形状・寸法はほとんど変化していず、
また摩耗量は最大１０μｍ程度であるにもかかわらず、
伝熱管内面の溝が浅くなっていることが分かった。さら
に、使用前後のプラグ溝凸部の面粗さを調べたところ、
従来品とこの試作品との間で大差はなく、いずれも使用
前の平均面粗さ（Ｒａ）は１μｍ以下であるのに対し、
使用後のＲａは５〜１０μｍであった。すなわち、深溝
タイプの伝熱管は従来と比べて高応力で溝が転造される
ため、プラグの溝表面に初期摩耗の状態で微細な凹凸が
発生し、伝熱管材の塑性変形が阻害され、結果としてプ
ラグの溝の底部にまで伝熱管材が流入し難くなり、短寿
命と評価されていることが分かった。このことから、プ
ラグ材料を、初期摩耗の状態で面粗さが劣化し難い合
金、すなわち、ＷＣ粒度がより微粒の合金とすることが
必要であるという第４の知見を得た。Here, it was examined in detail that the wear resistance of the plug did not correspond to the hardness of the plug material. The abrasion resistance of the plug is evaluated based on the groove shape and dimensions of the heat transfer tube after rolling.However, using a scanning laser microscope, the groove shape, dimensions, surface roughness and transmission of the used plug are determined. When the groove shape and dimensions of the inner surface of the heat tube were examined, the groove shape and dimensions of the plug after use hardly changed.
Despite the maximum wear amount of about 10μm,
It was found that the groove on the inner surface of the heat transfer tube was shallow. Furthermore, when the surface roughness of the plug groove convex part before and after use was examined,
There is no significant difference between the conventional product and this prototype, and the average surface roughness (Ra) before use is 1 μm or less,
Ra after use was 5 to 10 μm. In other words, the deep groove type heat transfer tube is rolled with higher stress than before, so fine irregularities occur on the groove surface of the plug in the state of initial wear, plastic deformation of the heat transfer tube material is inhibited, As a result, it became difficult for the heat transfer tube to flow into the bottom of the groove of the plug, and it was found that the tube was evaluated as having a short life. From this, the fourth finding was obtained that it is necessary to use a plug material which is an alloy whose surface roughness is hardly deteriorated in the state of initial wear, that is, an alloy having a finer WC particle size.

【０００９】本発明は、これらの知見に基いてなされた
ものである。すなわち、長寿命の内面溝付伝熱管製造用
プラグを得るには、まずその材料を、ＷＣ平均粒度０．
４μｍ以上、０．８μｍ以下の超微粒超硬合金とするこ
とにより、耐摩耗性を改良すると共に摩耗による面粗さ
の劣化を抑制することが必要である。ＷＣ平均粒度０．
４μｍ未満の超硬合金は、市販のＷＣ原料粉末の粒度と
の関係で製造することが困難であり、０．８μｍを超え
るとプラグ溝表面の初期摩耗によって面粗さが劣化しや
すくなる。ここで、ＷＣ粒度の調節のために、必要に応
じて従来より知られている炭化クロム、炭化バナジウ
ム、炭化タンタルなどの粒成長抑制剤を必要量添加して
もよいことはいうまでもない。The present invention has been made based on these findings. That is, in order to obtain a plug for manufacturing a heat transfer tube with an inner surface groove having a long service life, first, the material should be used with a WC average particle size of 0.1.
It is necessary to improve the wear resistance and to suppress the deterioration of the surface roughness due to the wear by using a superfine-grained cemented carbide of 4 μm or more and 0.8 μm or less. WC average particle size
It is difficult to produce a cemented carbide having a size of less than 4 μm in relation to the particle size of a commercially available WC raw material powder. If it exceeds 0.8 μm, the surface roughness tends to deteriorate due to the initial wear of the plug groove surface. Here, needless to say, a necessary amount of a conventionally known grain growth inhibitor such as chromium carbide, vanadium carbide, or tantalum carbide may be added in order to adjust the WC particle size.

【００１０】また、従来の超微粒超硬合金のＣｏ量は１
５％程度が最大であるが、この場合は硬さが約９１．５
ＨＲＡと高すぎて、衝撃値が１２０ｋＪ／ｍ^２程度とか
なり高い値を示すとはいえ、破壊靭性値（Ｋ_ＩＣ）が約
７ＭＰａ・ｍ^１／２と低く脆性であり実用に耐えない。
それゆえ、Ｃｏ量を１８％以上として衝撃値やＫ_ＩＣを
高めることが望ましいが、２８％を超えると硬さが低下
して耐摩耗性が不十分となるので、Ｃｏ量は１８％以
上、２８％以下とすることが好ましい。[0010] The amount of Co in the conventional ultrafine-grained cemented carbide is 1
The maximum is about 5%, but in this case, the hardness is about 91.5.
Although the HRA is too high, the impact value is considerably high at about 120 kJ / m ^2, but the fracture toughness (K _IC ) is as low as about 7 MPa · m ^1/2 and brittle, and is not practical.
Therefore, it is desirable to increase the impact value and K _IC the Co content as 18% or more, since the hardness exceeds 28% the wear resistance is insufficient and decreases, Co content 18% or more, It is preferable to set it to 28% or less.

【００１１】更に、異物や不純物の混入など、抗折力に
影響を及ぼす諸欠陥因子を減少させて、平均抗折力を
３．５ＧＰａ以上の合金とすると、より安定したプラグ
長寿命が得られる。Further, when an alloy having an average transverse rupture force of 3.5 GPa or more is reduced by reducing various defect factors affecting the transverse rupture force such as inclusion of foreign matter or impurities, a more stable plug long life can be obtained. .

【００１２】本発明のプラグでは、プラグの溝表面が次
第に摩耗して凹凸を生じても、その面粗さが小であるの
で伝熱管材の流れが損なわれ難く、結果として伝熱管材
の塑性変形がスムーズに行われ、かつ溝の欠損によって
寿命となることがなくなるため、実用上十分な性能を発
揮する。In the plug of the present invention, even if the groove surface of the plug gradually wears and becomes uneven, the flow of the heat transfer tube is hardly impaired because the surface roughness is small, and as a result, the plasticity of the heat transfer tube is reduced. Since the deformation is performed smoothly and the life is not lost due to the lack of the groove, practically sufficient performance is exhibited.

【００１３】一方、伝熱管への溝転造加工には、不水溶
性潤滑剤を用いることが多いが、近年は環境問題上、水
溶性潤滑剤が用いられるようになりつつある。この場
合、ＷＣ−Ｃｏ系超硬合金製のプラグでは腐食に起因し
て溝表面に凹凸が生じ、そこに伝熱管材が凝着すること
によりプラグの寿命が低下するという問題が起きやす
く、その対策としては、プラグ材料を結合相金属のＣｏ
の一部または全部をＮｉで置換した高耐食性の超硬合金
とすることが望ましい。On the other hand, a water-insoluble lubricant is often used in the groove rolling process for the heat transfer tube. However, in recent years, a water-soluble lubricant has been used due to environmental problems. In this case, in the case of a plug made of a WC-Co cemented carbide, unevenness is generated on the groove surface due to corrosion, and the problem that the life of the plug is shortened due to adhesion of the heat transfer tube material to the groove tends to occur. As a countermeasure, use a plug material such as Co
It is desirable to use a highly corrosion-resistant cemented carbide in which part or all of Ni is replaced by Ni.

【００１４】[0014]

【実施例】通常の粉末冶金法によって、表１に示したよ
うな種々のＷＣ平均粒度および結合相量を有する超硬合
金素材を焼結し、熱間静水圧プレスを経て、研削加工に
より本発明および比較用の材質のプラグを作製した。表
１には各合金の機械的性質、および内径８．２ｍｍ、肉
厚０．４ｍｍの銅管の内面に不水溶性潤滑剤を用いて溝
転造加工を施すことにより、深溝タイプの伝熱管を製造
した場合の、プラグ溝凸部の摩耗量、プラグ使用後の溝
凸部の面粗さ（Ｒａ）、溝凸部の欠損の有無および形状
保持寿命を併記した。ここで形状保持寿命とは、銅管１
コイル（重量、５トン）の加工終了時点で、伝熱管の転
造溝形状が所定の公差内にある場合を１００％として表
したプラグの寿命を示す。従来のプラグでは、摩耗量、
面粗さ共に大きく、欠損する場合もあり、形状保持寿命
は５０％に満たない。一方、本発明プラグでは、平均抗
折力がやや低いＡ、Ｂのプラグでは欠損が発生したた
め、形状保持寿命が１００％に満たないが、従来のプラ
グに比べれば２倍程度に寿命が延長され、また、これら
より平均抗折力の高いその他の本発明プラグでは、欠損
しないと共に摩耗量、面粗さも小さく、いずれも１００
％の形状保持寿命を示すことが分かる。EXAMPLE A cemented carbide material having various WC average particle sizes and various binder phase amounts as shown in Table 1 was sintered by a usual powder metallurgy method, passed through a hot isostatic press, and then subjected to a grinding process. Inventive and comparative plugs were made. Table 1 shows the mechanical properties of each alloy and the deep groove type heat transfer tube by subjecting the inner surface of a copper tube with an inner diameter of 8.2 mm and a wall thickness of 0.4 mm to groove rolling using a water-insoluble lubricant. In the case of No., the amount of wear of the plug groove protrusion, the surface roughness (Ra) of the groove protrusion after use of the plug, the presence or absence of the groove protrusion, and the shape retention life are also shown. Here, the shape retention life is defined as copper tube 1
The life of the plug is expressed as 100% when the shape of the rolling groove of the heat transfer tube is within a predetermined tolerance at the end of processing of the coil (weight: 5 tons). With conventional plugs, the amount of wear,
Both the surface roughness is large and may be broken, and the shape retention life is less than 50%. On the other hand, in the plugs of the present invention, since the A and B plugs having slightly lower average bending strengths have defects, the shape retention life is less than 100%, but the life is extended to about twice that of the conventional plug. In addition, the other plugs of the present invention having a higher average bending strength than those of the present invention do not have chipping and have a small amount of wear and surface roughness.
% Of the shape retention life.

【００１５】[0015]

【表１】 [Table 1]

【００１６】[0016]

【発明の効果】以上説明したように、本発明のプラグ
は、深溝タイプの非鉄金属材料製の各種熱交換機用内面
溝付伝熱管の製造において長寿命を示し、生産性の向上
に寄与できるので、産業上の利用価値が高い。As described above, the plug of the present invention has a long service life in the production of heat transfer tubes with internal grooves for various heat exchangers made of a non-ferrous metal material of a deep groove type, and can contribute to an improvement in productivity. High industrial value.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 中田 勲 東京都大田区下丸子２丁目17番10号 冨士 ダイス株式会社内 Ｆターム(参考） 4E096 FA23 FA30 4K018 AD06 BB04 DA11 KA14 KA19 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Isao Nakata 2-17-10 Shimomaruko, Ota-ku, Tokyo F-Die Co., Ltd. F-term (reference) 4E096 FA23 FA30 4K018 AD06 BB04 DA11 KA14 KA19

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】 炭化タングステンの平均粒度が０．４μ
ｍ以上、０．８μｍ以下である超硬合金を用いることを
特徴とする、内面溝付伝熱管製造用プラグ。1. The tungsten carbide has an average particle size of 0.4 μm.
A plug for manufacturing a heat transfer tube with an inner groove, characterized by using a cemented carbide having a diameter of not less than m and not more than 0.8 μm. 【請求項２】 炭化タングステンの平均粒度が０．４μ
ｍ以上、０．８μｍ以下で、コバルトおよび／またはニ
ッケル量を１８質量％以上、２８質量％以下とした超硬
合金を用いることを特徴とする、内面溝付伝熱管製造用
プラグ。2. The average particle size of tungsten carbide is 0.4 μm.
A plug for manufacturing a heat transfer tube with an inner groove, characterized by using a cemented carbide having a length of at least m and at most 0.8 μm and an amount of cobalt and / or nickel of at least 18 mass% and at most 28 mass%. 【請求項３】 炭化タングステンの平均粒度が０．４μ
ｍ以上、０．８μｍ以下、コバルトおよび／またはニッ
ケル量が１８質量％以上、２８質量％以下で、平均抗折
力を３．５ＧＰａ以上とした超硬合金を用いることを特
徴とする、内面溝付伝熱管製造用プラグ。3. The average particle size of tungsten carbide is 0.4 μm.
inner surface groove, characterized by using a cemented carbide having an average bending strength of 3.5 GPa or more with an amount of cobalt and / or nickel being 18% by mass or more and 28% by mass or less. Plug for heat transfer tube production.