JP5960672B2 - High strength copper alloy tube - Google Patents
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Description
本発明は、熱交換器等に使用することができ、かつ強度に優れた銅合金管に関するものである。 The present invention relates to a copper alloy tube that can be used in a heat exchanger or the like and has excellent strength.
一般に、熱交換器の熱媒体を流通させる管には、熱伝導率および加工性に優れる、銅管（銅または銅合金からなる管をいう）が適用される。例えば、エアコンの熱交換器は、板状のアルミニウムフィンを多数重ねて、これに蛇行する銅管を貫通させた構造である。このような熱交換器を製造するためには、まず、ヘアピン状に曲げ加工したＵ字形銅管をアルミニウムフィンの貫通孔に通し、前記銅管を治具により拡管することによって銅管とアルミニウムフィンとを密着させる。更に、銅管の開放端を拡管し、この拡管部に別のＵ字形に曲げ加工した銅管を挿入し、りん銅ろうによって銅管を拡管部にろう付けしている。
このため、熱交換器に使用される銅管には、曲げ加工、拡管・フレア加工、縮管・絞り加工の加工性が良好であることが要求される。
In general, a copper pipe (referred to as a pipe made of copper or a copper alloy) having excellent thermal conductivity and workability is applied to the pipe through which the heat medium of the heat exchanger flows. For example, a heat exchanger of an air conditioner has a structure in which a large number of plate-like aluminum fins are stacked and a copper pipe meandering is passed therethrough. In order to manufacture such a heat exchanger, first, a U-shaped copper tube bent into a hairpin shape is passed through a through-hole of an aluminum fin, and the copper tube is expanded by a jig, whereby the copper tube and the aluminum fin are expanded. And make it close. Further, the open end of the copper pipe is expanded, a copper pipe bent into another U-shape is inserted into the expanded section, and the copper pipe is brazed to the expanded section by phosphor copper brazing.
For this reason, copper pipes used in heat exchangers are required to have good workability in bending, expanding / flaring, contracting / drawing.
さらに近年は、環境問題対策から冷媒が変化し、銅管に従来以上の圧力が加わることとなった。また、銅地金の高騰に伴って、銅合金管の薄肉化による銅使用量の低減に対する要求も強くなっている。こうしたことから、より優れた破壊圧力と良好な加工性を兼備する銅合金管に対する要請が高まっている。 Furthermore, in recent years, refrigerants have changed due to measures against environmental problems, and more pressure than before has been applied to copper tubes. In addition, as copper bullion has soared, demands for reducing the amount of copper used by reducing the thickness of copper alloy tubes have also increased. For these reasons, there is an increasing demand for copper alloy tubes that have both superior fracture pressure and good workability.
銅合金の耐破壊圧力の向上のために、従来から多くの検討がなされてきている。耐破壊圧力に優れた銅合金として、析出強化型のＣｕ−Ｃｏ−Ｐ系合金やＣｕ−Ｓｎ−Ｐ系合金が知られている。特許文献１には、ＳｎとＰを添加したＣｕ−Ｓｎ−Ｐ系合金が開示されている。特許文献２には、ＣｏとＰを添加したＣｕ−Ｃｏ−Ｐ系合金が開示されている。特許文献３には、結晶粒径と析出物サイズを規定したＣｕ−Ｃｏ−Ｐ系合金が開示されている。特許文献４には、他の成分を規定して、破壊圧力／引張強さの比を増大させたＣｕ−Ｃｏ−Ｐ系合金が開示されている。特許文献５には、ろう付け後の強度増大を図ったＣｕ−Ｃｏ−Ｐ系合金が開示されている。 Many studies have been made to improve the fracture pressure resistance of copper alloys. As a copper alloy having excellent fracture pressure resistance, precipitation-strengthened Cu—Co—P alloys and Cu—Sn—P alloys are known. Patent Document 1 discloses a Cu—Sn—P based alloy to which Sn and P are added. Patent Document 2 discloses a Cu—Co—P based alloy to which Co and P are added. Patent Document 3 discloses a Cu—Co—P alloy in which the crystal grain size and the precipitate size are defined. Patent Document 4 discloses a Cu—Co—P alloy in which other components are defined to increase the ratio of fracture pressure / tensile strength. Patent Document 5 discloses a Cu—Co—P-based alloy that is intended to increase the strength after brazing.
しかしながら、特許文献１の銅合金は、Ｓｎの固溶強化により強度が向上し、ろう付け後の軟化も小さく、伝熱管に用いると管の肉厚を薄くすることが可能になるが、熱交換器とするためＵ字曲げ加工を行うときに、加工性にさらに改良する余地を有するものであった。 However, the copper alloy of Patent Document 1 has improved strength due to solid solution strengthening of Sn, and softening after brazing is small. When used in a heat transfer tube, the thickness of the tube can be reduced. When the U-shaped bending process was performed to make a container, there was room for further improvement in workability.
また、特許文献２の銅合金は、Ｃｏの燐化物による析出強化によって引張り強さを向上させているが、強度上昇の割には耐圧破壊強度が上昇せず、また前記燐化物はろう付け温度では固溶するため、ろう付け後は強度が低下する。このため、伝熱管に使用した場合、予想したほど肉厚を薄くできないという問題点がある。 In addition, the copper alloy of Patent Document 2 has improved tensile strength by precipitation strengthening with Co phosphide, but the breakdown strength does not increase for the increase in strength, and the phosphide has a brazing temperature. Then, since it dissolves, the strength decreases after brazing. For this reason, when it uses for a heat exchanger tube, there exists a problem that thickness cannot be thinned as expected.
従来のＣｕ−Ｃｏ−Ｐ系合金では、特許文献３に示すように、結晶粒径および析出物状態を制御することによって高強度化してきた。しかし従来の知見のように結晶粒径や析出物を制御して引張強さを高くしても、引張強さの上昇の割には耐圧破壊強度が上昇せず、予想したほど肉厚を薄くできないという問題点がある。そこで、特許文献４では、成分コントロールによって耐圧強度／引張強さの比を増大させて、破壊圧力を高強度化してきた。しかしながら昨今では、銅管の薄肉化要求が一層厳しいものとなり、更なる高強度化が求められている。 In the conventional Cu—Co—P based alloy, as shown in Patent Document 3, the strength has been increased by controlling the crystal grain size and the precipitate state. However, even if the tensile strength is increased by controlling the crystal grain size and precipitates as in the conventional knowledge, the pressure fracture strength does not increase for the increase in tensile strength, and the thickness is reduced as expected. There is a problem that it is not possible. Therefore, in Patent Document 4, the fracture pressure is increased by increasing the pressure-resistant strength / tensile strength ratio through component control. However, in recent years, the demand for thinner copper pipes has become more severe, and further enhancement of strength has been demanded.
本発明は、かかる状況に鑑みてなされたものであり、耐圧強度、耐圧強度／引張強さの比に優れた高強度、高加工性の銅管を提供することを目的とする。 The present invention has been made in view of such a situation, and an object thereof is to provide a high-strength, high-workability copper tube excellent in the pressure strength and the ratio of pressure strength / tensile strength.
そこで、従来以上に高強度化する方法を検討したところ、本発明者らは結晶粒径、析出物制御に加えて、結晶粒径の形状を制御することで破壊圧力を向上できることを見出した。すなわち、結晶粒の形状が等軸に近いほど、耐圧強度／引張強さの比が大きくなり、耐圧強度を高くすることができることを見出した。一方、特許文献５に示すように析出物を微細に制御するために焼鈍の繰り返しなどを行うと、結晶粒形状が伸張した組織となり、引張強さの増加の割りには耐圧強度の改良がやや不十分であることが分かった。つまり、従来の銅合金管では、析出物制御と結晶粒形状とを同時に制御することが必ずしも十分ではなかった。 Accordingly, when a method for increasing the strength higher than before is studied, the present inventors have found that the fracture pressure can be improved by controlling the crystal grain size in addition to controlling the crystal grain size and precipitates. That is, it has been found that the closer the crystal grain shape is to the equiaxed axis, the larger the pressure strength / tensile strength ratio and the higher the pressure strength. On the other hand, as shown in Patent Document 5, if annealing is repeated to finely control the precipitates, the crystal grain shape becomes a stretched structure, and the improvement of the pressure strength is slightly higher for the increase of the tensile strength. It turned out to be insufficient. That is, in the conventional copper alloy tube, it is not always sufficient to simultaneously control the precipitate control and the crystal grain shape.
そこで、本発明者らは、溶体化処理の処理条件、特に昇温速度を制御することで、析出物を微細分散させつつ、結晶粒の形状を等軸化して、従来よりも高い耐圧強度と良好な加工性を有した銅合金管を製造することができることを見出した。
本発明は、上記の検討による新たな知見を得ることによって、完成するに至ったものである。すなわち、本発明は以下の構成を有するものである。
Therefore, the present inventors controlled the solution treatment conditions, particularly the heating rate, to finely disperse the precipitates and to equiax the shape of the crystal grains. It has been found that a copper alloy tube having good workability can be produced.
The present invention has been completed by obtaining new findings from the above examination. That is, the present invention has the following configuration.
（１）本発明の高強度銅合金管は、Ｃｏ：０．１３〜０．４０質量％、Ｐ：０．０２〜０．１質量％を含有し、残部がＣｕおよび不可避的不純物である銅合金からなり、管軸方向に平行な断面におけるＳＥＭ−ＥＢＳＰ法による測定で、長手方向の平均結晶粒径をｄ１、肉厚方向の平均結晶粒径をｄ２としたときに、ｄ１が４０μｍ以下、ｄ２／ｄ１が０．６０以上であり、析出物の平均直径が３〜１５ｎｍであり、前記析出物の数密度が３０００個／μｍ３以上であることを特徴としている。 (1) The high-strength copper alloy tube of the present invention contains Co: 0.13-0.40% by mass, P: 0.02-0.1% by mass, and the balance being Cu and inevitable impurities It is made of an alloy and measured by the SEM-EBSP method in a cross section parallel to the tube axis direction. When the average crystal grain size in the longitudinal direction is d1 and the average crystal grain size in the thickness direction is d2, d1 is 40 μm or less, d2 / d1 is 0.60 or more, the average diameter of the precipitates is 3 to 15 nm, and the number density of the precipitates is 3000 pieces / μm 3 or more.
係る構成を有することによって、Ｃｕ−Ｃｏ−Ｐ系銅合金とし、長手方向と肉厚方向の平均結晶粒径の関係を所定の範囲とし、析出物の平均直径と数密度を所定の範囲とすることで、耐圧強度、耐圧強度／引張強さの比、強度および加工性に優れた銅管とすることができる。 By having such a configuration, a Cu—Co—P-based copper alloy is used, the relationship between the average crystal grain size in the longitudinal direction and the thickness direction is within a predetermined range, and the average diameter and number density of precipitates are within a predetermined range. Thus, a copper tube excellent in pressure strength, pressure strength / tensile strength ratio, strength and workability can be obtained.
（２）本発明の高強度銅合金管は、前記銅合金がさらに、Ｎｉ：０．００５〜０．１０質量％、Ｚｎ：０．００５〜１．０質量％およびＳｎ：０．０５〜１．０質量％のいずれか１種以上を含有することを特徴としている。 (2) In the high-strength copper alloy tube of the present invention, the copper alloy further includes Ni: 0.005 to 0.10% by mass, Zn: 0.005 to 1.0% by mass, and Sn: 0.05 to 1. It is characterized by containing any one or more of 0.0% by mass.
係る構成を有することによって、高強度銅管の強度をさらに向上させることができる。 By having such a configuration, the strength of the high-strength copper tube can be further improved.
（３）本発明の高強度銅合金管は、前記銅合金がさらに、Ｆｅ、Ｍｎ、Ｍｇ、Ｃｒ、Ｔｉ、Ｚｒ、Ａｇから選択された１種以上を合計で０．１０質量％未満含有することを特徴としている。 (3) In the high-strength copper alloy tube of the present invention, the copper alloy further contains one or more selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag in total less than 0.10% by mass. It is characterized by that.
係る構成を有することによって、高強度銅管の強度およびろう付け後の強度をさらに向上させることができる。 By having such a configuration, the strength of the high-strength copper tube and the strength after brazing can be further improved.
本発明によると、上記の組織を達成することにより、例えば耐圧強度が２７０ＭＰａ以上、かつ耐圧強度／引張強さの比が０．９以上の高強度、高加工性の銅管を得ることができる。 According to the present invention, by achieving the above structure, for example, a high strength and high workability copper tube having a pressure strength of 270 MPa or more and a pressure strength / tensile strength ratio of 0.9 or more can be obtained. .
以下、本発明に係る高強度銅合金管について、詳細に説明する。
本発明に係る高強度銅合金管（以下、単に高強度銅管ということもある。）は、熱交換器、例えば空調機やヒートポンプ給湯機の熱媒体を流通させる配管に適用され、平滑管、内面溝付管等の用途に応じた形状および寸法とするが、特に限定されるものではない。はじめに、本発明に係る高強度銅管を形成する銅合金について説明する。
Hereinafter, the high strength copper alloy pipe according to the present invention will be described in detail.
A high-strength copper alloy tube according to the present invention (hereinafter sometimes simply referred to as a high-strength copper tube) is applied to a heat exchanger, for example, a pipe for circulating a heat medium of an air conditioner or a heat pump water heater, Although it is set as the shape and dimension according to uses, such as an internally grooved pipe | tube, it is not specifically limited. First, the copper alloy forming the high-strength copper tube according to the present invention will be described.
〔銅合金〕
本発明に係る高強度銅管を形成する銅合金は、Ｃｏ：０．１３〜０．４０質量％、Ｐ：０．０２〜０．１質量％を含有し、残部がＣｕおよび不可避的不純物からなる。以下、この銅合金を構成する各元素について説明する。
〔Copper alloy〕
The copper alloy forming the high-strength copper tube according to the present invention contains Co: 0.13-0.40 mass%, P: 0.02-0.1 mass%, and the balance is made of Cu and inevitable impurities. Become. Hereinafter, each element which comprises this copper alloy is demonstrated.
（Ｃｏ：０．１３〜０．４０質量％）
Ｃｏは、銅合金中でＰとの化合物（適宜、Ｃｏ−Ｐ化合物という）を生成、析出させる。この化合物（析出物）は、高強度銅管の引張強さ等の強度を向上させる効果を有する。また、ろう付けのための熱処理において、結晶粒の粗大化を抑制するピンニング粒子として作用するため、熱処理による強度低下を抑制し、特に８００℃以上の高温でのろう付け処理後の強度を確保させる。また、Ｃｏ−Ｐ化合物は、熱間押出や中間焼鈍においても析出して、結晶粒の粗大化を抑制するため、ろう付け前の高強度銅管の結晶粒径を所定値以下とすることができる。これらの効果はＣｏ−Ｐ化合物の析出量が多いほど向上し、Ｃｏの含有量が０．１３質量％未満では、析出量が少なく、前記効果が十分に得られない。一方、Ｃｏの含有量が０．４０質量％を超えると、Ｃｏ−Ｐ化合物が過剰に析出するため、強度が過大となって、伸びが低下して加工性が不足したり、熱間押出等にて変形抵抗が過大となって割れを生じる虞がある。したがって、Ｃｏの含有量は０．１３〜０．４０質量％以下とする。好ましくは、０．１５〜０．３０質量％である。
(Co: 0.13-0.40 mass%)
Co produces and precipitates a compound with P (suitably referred to as a Co—P compound) in a copper alloy. This compound (precipitate) has an effect of improving the strength such as the tensile strength of the high-strength copper tube. In addition, it acts as a pinning particle that suppresses the coarsening of crystal grains in the heat treatment for brazing, so that the strength reduction due to the heat treatment is suppressed, and particularly the strength after the brazing treatment at a high temperature of 800 ° C. or higher is ensured. . In addition, the Co—P compound is precipitated even during hot extrusion and intermediate annealing, and the crystal grain size of the high-strength copper tube before brazing may be set to a predetermined value or less in order to suppress coarsening of crystal grains. it can. These effects improve as the amount of precipitation of the Co—P compound increases. When the Co content is less than 0.13% by mass, the amount of precipitation is small, and the above effects cannot be obtained sufficiently. On the other hand, when the Co content exceeds 0.40% by mass, the Co-P compound is excessively precipitated, so that the strength is excessive, the elongation is lowered and the workability is insufficient, hot extrusion, etc. There is a possibility that the deformation resistance becomes excessive and cracking occurs. Therefore, the Co content is 0.13 to 0.40 mass% or less. Preferably, it is 0.15-0.30 mass%.
（Ｐ：０．０２〜０．１質量％）
Ｐは、一般に銅合金の脱酸のために添加される。さらに本発明に係る高強度銅管においては、Ｐは銅合金中でＣｏとの化合物（Ｃｏ−Ｐ化合物）を生成、析出させ、前記の通り強度を向上させる効果を有する。Ｐの含有量が０．０２質量％未満では、Ｃｏ−Ｐ化合物の析出量が少なく、結晶粒が粗大化し、前記効果が十分に得られない。一方、Ｐの含有量が０．１質量％を超えると、加工性が低下して、熱間加工や冷間加工において割れが生じる虞がある。したがって、Ｐの含有量は０．０２〜０．１質量％とする。好ましくは、０．０３〜０．０７質量％である。
(P: 0.02-0.1% by mass)
P is generally added for deoxidation of copper alloys. Furthermore, in the high-strength copper pipe according to the present invention, P has an effect of generating and precipitating a compound with Co (Co—P compound) in a copper alloy and improving the strength as described above. When the P content is less than 0.02% by mass, the amount of Co—P compound precipitated is small, the crystal grains become coarse, and the above effects cannot be obtained sufficiently. On the other hand, when the content of P exceeds 0.1% by mass, workability is lowered, and there is a possibility that cracking may occur in hot working or cold working. Therefore, the content of P is set to 0.02 to 0.1% by mass. Preferably, it is 0.03-0.07 mass%.
本発明の銅合金は、さらに、Ｎｉ：０．００５〜０．１０質量％、Ｚｎ：０．００５〜１．０質量％およびＳｎ：０．０５〜１．０質量％のいずれか１種以上を含有することが好ましい。 The copper alloy of the present invention further includes at least one of Ni: 0.005 to 0.10% by mass, Zn: 0.005 to 1.0% by mass, and Sn: 0.05 to 1.0% by mass. It is preferable to contain.
（Ｎｉ：０．００５〜０．１０質量％）
Ｎｉは、銅合金中でＣｏ、Ｐとの三元化合物（適宜、(Ｃｏ、Ｎｉ)−Ｐ化合物という）を生成、析出させる。この(Ｃｏ、Ｎｉ)−Ｐ化合物は、Ｃｏ−Ｐ化合物と同様に、高強度銅管の強度を向上させ、また熱処理においてピンニング粒子として作用してろう付け後強度を確保する効果を有する。したがって、Ｎｉは、Ｃｏの含有量を増大させることなく、強度を一層向上させることができる。(Ｃｏ、Ｎｉ)−Ｐ化合物を十分に析出させて前記効果を得るために、Ｎｉの含有量は０．００５質量％以上とすることが好ましい。一方、Ｎｉの含有量が０．１０質量％を超えると、(Ｃｏ、Ｎｉ)−Ｐ化合物が過剰に析出するため強度が過大となって伸びが低下して、加工性が不足する。したがって、前記効果を得るためにＮｉを含有させるときは、Ｎｉの含有量は、０．００５〜０．１０質量％とする。
(Ni: 0.005 to 0.10% by mass)
Ni forms and precipitates a ternary compound with Co and P (suitably referred to as (Co, Ni) -P compound) in a copper alloy. This (Co, Ni) -P compound has the effect of improving the strength of a high-strength copper tube and ensuring the strength after brazing by acting as pinning particles in the heat treatment, like the Co-P compound. Therefore, Ni can further improve the strength without increasing the Co content. In order to sufficiently precipitate the (Co, Ni) -P compound and obtain the above effect, the Ni content is preferably 0.005% by mass or more. On the other hand, if the Ni content exceeds 0.10% by mass, the (Co, Ni) -P compound precipitates excessively, so that the strength becomes excessive and the elongation decreases, resulting in insufficient workability. Therefore, when Ni is contained to obtain the above effect, the Ni content is set to 0.005 to 0.10% by mass.
（Ｚｎ：０．００５〜１．０質量％）
Ｚｎは、銅合金の強度、耐熱性および疲労強度を向上させる効果を有する。また、Ｚｎを含有させることによって、高強度銅管のろう付けにおいてりん銅ろう等のろう材の濡れ性を向上させることができる。さらに、Ｚｎを含有させることによって、冷間圧延、抽伸、転造等に用いる工具の磨耗を低減させて、抽伸プラグや溝付プラグ等を長寿命化させる効果があり、生産コストの低減に寄与する。また、高強度銅管の熱交換器への組立てにおいても、曲げ加工時のマンドレルの磨耗を低減させ、さらにアルミニウムフィンの貫通孔のフィンカラーに密着させる際の拡管加工時の拡管ビュレットの磨耗も低減させることができる。これらの効果を得るために、Ｚｎの含有量は０．００５質量％以上とすることが好ましい。一方、Ｚｎの含有量が１．０質量％を超えると、応力腐食割れ感受性が高くなる。したがって、前記効果を得るためにＺｎを含有させるときは、Ｚｎの含有量は０．００５〜１．０質量％とする。
(Zn: 0.005 to 1.0 mass%)
Zn has the effect of improving the strength, heat resistance and fatigue strength of the copper alloy. Moreover, by containing Zn, the wettability of a brazing material such as phosphor copper brazing can be improved in brazing a high-strength copper tube. In addition, the inclusion of Zn has the effect of reducing the wear of tools used for cold rolling, drawing, rolling, etc., extending the life of drawing plugs and grooved plugs, etc., contributing to the reduction of production costs To do. In addition, when assembling a high-strength copper tube into a heat exchanger, the wear of the mandrel during bending is reduced, and the wear of the expanded burette is also increased during tube expansion when closely contacting the fin collar of the through hole of the aluminum fin. Can be reduced. In order to obtain these effects, the Zn content is preferably 0.005% by mass or more. On the other hand, when the Zn content exceeds 1.0 mass%, the stress corrosion cracking sensitivity becomes high. Therefore, when Zn is contained in order to obtain the effect, the Zn content is set to 0.005 to 1.0 mass%.
（Ｓｎ：０．０５〜１．０質量％）
Ｓｎは、銅合金中で固溶硬化によって引張強さを向上させる。また、高強度銅管の焼鈍やろう付けによる熱影響に対して、結晶粒度の粗大化が抑制されて、耐熱性を向上させる。これらの効果を得るために、Ｓｎの含有量は０．０５質量％以上とすることが好ましい。一方、Ｓｎの含有量が１．０質量％を超えると、鋳塊における凝固偏析が激しくなって、通常の熱間押出や加工熱処理において偏析が完全に解消しないことがあり、銅管の組織、機械的性質、曲げ加工性、ろう付け後の組織および機械的性質の不均一が生じる。また、熱間押出における熱間変形抵抗が高くなり、Ｓｎの含有量が１．０質量％以下の銅合金と同一の押出圧力とするためには熱間押出温度を高くする必要がある。そうすると、高温で押出材の表面酸化が増加し、生産性の低下や銅管の表面欠陥が増加する。したがって、前記効果を得るためにＳｎを含有させるときは、Ｓｎの含有量は０．０５〜１．０質量％とする。
(Sn: 0.05 to 1.0% by mass)
Sn improves the tensile strength by solid solution hardening in a copper alloy. Moreover, the coarsening of a crystal grain size is suppressed with respect to the heat influence by annealing and brazing of a high intensity | strength copper pipe, and heat resistance is improved. In order to obtain these effects, the Sn content is preferably 0.05% by mass or more. On the other hand, if the Sn content exceeds 1.0% by mass, solidification segregation in the ingot becomes severe, and segregation may not be completely eliminated in normal hot extrusion or processing heat treatment, Mechanical properties, bending workability, texture after brazing, and non-uniformity of mechanical properties occur. Moreover, in order to make hot deformation resistance in hot extrusion high, and to make it the same extrusion pressure as the copper alloy whose Sn content is 1.0 mass% or less, it is necessary to make hot extrusion temperature high. If it does so, the surface oxidation of an extrusion material will increase at high temperature, and the fall of productivity and the surface defect of a copper pipe will increase. Therefore, when Sn is contained in order to obtain the effect, the Sn content is set to 0.05 to 1.0% by mass.
（Ｆｅ、Ｍｎ、Ｍｇ、Ｃｒ、Ｔｉ、Ｚｒ、Ａｇから選択された１種以上を合計で０．１０質量％未満）
本発明の銅合金は、さらに、Ｆｅ、Ｍｎ、Ｍｇ、Ｃｒ、Ｔｉ、Ｚｒ、Ａｇから選択された１種以上を合計で０．１０質量％未満含有することが好ましい。
(Totally less than 0.10% by mass of one or more selected from Fe, Mn, Mg, Cr, Ti, Zr, Ag)
The copper alloy of the present invention preferably further contains one or more selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag in total less than 0.10% by mass.
Ｆｅ、Ｍｎ、Ｍｇ、Ｃｒ、Ｔｉ、Ｚｒ、Ａｇはそれぞれ、単体で、またはＦｅ２Ｐ、Ｍｎ３Ｐ２等のＰとの化合物として析出することで、前記のＣｏ−Ｐ化合物等と同様に、高強度銅管の強度およびろう付け後の強度を向上させる効果がある。一方、これらの元素が合計で０．１０質量％以上含有されると、熱間押出における熱間変形抵抗が高くなり、当該元素を含有しない銅合金と同一の押出圧力とするためには熱間押出温度を高くする必要がある。そうすると、高温で押出材の表面酸化が増加し、生産性の低下や銅管の表面欠陥が増加する。したがって、前記効果を得るために、Ｆｅ、Ｍｎ、Ｍｇ、Ｃｒ、Ｔｉ、Ｚｒ、Ａｇから選択された１種以上を含有させるときは、含有量は合計で０．１０質量％未満とする。 Each of Fe, Mn, Mg, Cr, Ti, Zr, and Ag precipitates as a single substance or as a compound with P such as Fe 2 P, Mn 3 P 2, etc. There is an effect of improving the strength of the high-strength copper tube and the strength after brazing. On the other hand, when these elements are contained in a total of 0.10% by mass or more, the hot deformation resistance in hot extrusion increases, and in order to obtain the same extrusion pressure as that of the copper alloy not containing the elements, It is necessary to increase the extrusion temperature. If it does so, the surface oxidation of an extrusion material will increase at high temperature, and the fall of productivity and the surface defect of a copper pipe will increase. Therefore, in order to acquire the said effect, when it contains 1 or more types selected from Fe, Mn, Mg, Cr, Ti, Zr, and Ag, content shall be less than 0.10 mass% in total.
〔高強度銅管の組織〕
本発明に係る高強度銅管は、管軸方向に平行な断面におけるＳＥＭ−ＥＢＳＰ法による測定で、長手方向の結晶粒径をｄ１、肉厚方向の結晶粒径をｄ２としたときに、ｄ１が４０μｍ以下、ｄ２／ｄ１が０．６０以上であり、析出物の平均直径が３〜１５ｎｍであり、析出物の数密度が３０００個／μｍ３以上である。
[High-strength copper tube structure]
The high-strength copper tube according to the present invention is d1 when the crystal grain size in the longitudinal direction is d1 and the crystal grain size in the thickness direction is d2 as measured by the SEM-EBSP method in a cross section parallel to the tube axis direction. Is 40 μm or less, d2 / d1 is 0.60 or more, the average diameter of the precipitates is 3 to 15 nm, and the number density of the precipitates is 3000 pieces / μm 3 or more.
（結晶粒径と形状）
本発明では、走査電子顕微鏡（Scanning Electron Microscope：ＳＥＭ）に、後方散乱電子回折像［ＥＢＳＰ：Electron Back Scattering (Scattered) diffraction Pattern］システムを搭載した結晶方位解析法を用いて、製品銅合金の管軸方向に平行な断面において測定を行なう（ＳＥＭ−ＥＢＳＰ法）。上記ＳＥＭ−ＥＢＳＰ法は、ＳＥＭの鏡筒内にセットした試料に電子線を照射してスクリーン上にＥＢＳＰを投影する。これを高感度カメラで撮影して、コンピュータに画像として取り込む。コンピュータでは、この画像を解析して、既知の結晶系を用いたシミュレーションによるパターンとの比較によって、結晶の方位が決定される。算出された結晶の方位は３次元オイラー角として、位置座標（ｘ、ｙ）などとともに記録される。このプロセスが全測定点に対して自動的に行なわれるので、測定終了時には数万〜数十万点の結晶方位データが得られる。本発明においては、隣り合う結晶粒の方位差が５°以上の結晶粒の境界を結晶粒界と定義し、結晶粒径が２μｍ以上の結晶粒のみについて評価する。
(Crystal grain size and shape)
In the present invention, a copper alloy tube is manufactured using a crystal orientation analysis method in which a scanning electron microscope (SEM) is equipped with an EBSP (Electron Back Scattering (Scattered) diffraction Pattern) system. Measurement is performed in a cross section parallel to the axial direction (SEM-EBSP method). In the SEM-EBSP method, an EBSP is projected onto a screen by irradiating an electron beam onto a sample set in an SEM column. This is taken with a high-sensitivity camera and captured as an image on a computer. In the computer, the orientation of the crystal is determined by analyzing this image and comparing it with a pattern obtained by simulation using a known crystal system. The calculated crystal orientation is recorded as a three-dimensional Euler angle together with position coordinates (x, y) and the like. Since this process is automatically performed for all measurement points, tens of thousands to hundreds of thousands of crystal orientation data can be obtained at the end of measurement. In the present invention, a boundary between crystal grains having an orientation difference of 5 ° or more between adjacent crystal grains is defined as a crystal grain boundary, and only crystal grains having a crystal grain diameter of 2 μm or more are evaluated.
その上で、本発明においては、測定エリアとして、管軸方向８００μｍ×管肉厚方向４００μｍに対して１．０μｍのピッチで電子線を照射し、結晶粒に関するデータを取得する。そして、管軸長手方向に線を５０本引き、線と交わる粒の平均切片長さＬ１を解析で求める。平均切片長さＬと平均結晶粒径ｄの間には、ｄ＝１．１３Ｌが成り立つといわれており、これらの事実は、例えば、ふぇらむVol.2、1997、P731-736などに記載されている。そこで解析で求めたＬ１から計算によって管軸長手方向の平均結晶粒径ｄ１を求める。同様にして、管肉厚方向の平均結晶粒径ｄ２を求める。 In addition, in the present invention, as a measurement area, electron beams are irradiated at a pitch of 1.0 μm with respect to a tube axis direction of 800 μm × tube thickness direction of 400 μm, and data on crystal grains is acquired. Then, 50 lines are drawn in the longitudinal direction of the tube axis, and the average section length L1 of the grains intersecting with the line is obtained by analysis. It is said that d = 1.13L is established between the average intercept length L and the average crystal grain size d, and these facts are described in, for example, Phaemu Vol.2, 1997, P731-736. ing. Therefore, an average crystal grain size d1 in the longitudinal direction of the tube axis is obtained from L1 obtained by analysis. Similarly, the average crystal grain size d2 in the tube thickness direction is obtained.
長手方向の平均結晶粒径ｄ１が４０μｍよりも大きいと、結晶粒微細化による強化量が小さくなり、強度が不足しやすくなる。また長手方向の平均結晶粒径ｄ１が４０μｍより大きいと、加工性が劣化してしまう。したがって、長手方向の平均結晶粒径ｄ１は、４０μｍ以下とする。好ましくは２５μｍ以下、より好ましくは２０μｍ以下である。長手方向の平均結晶粒径ｄ１の下限は特に存在しないが、製造上５μｍ程度が下限である。 If the average crystal grain size d1 in the longitudinal direction is larger than 40 μm, the amount of strengthening due to crystal grain refinement becomes small, and the strength tends to be insufficient. On the other hand, if the average crystal grain size d1 in the longitudinal direction is larger than 40 μm, the workability deteriorates. Therefore, the average crystal grain size d1 in the longitudinal direction is set to 40 μm or less. Preferably it is 25 micrometers or less, More preferably, it is 20 micrometers or less. There is no particular lower limit for the average crystal grain size d1 in the longitudinal direction, but about 5 μm is the lower limit in production.
結晶粒形状ｄ２／ｄ１が０．６０よりも小さいと、引張強さの割りに耐圧強度が低くなり、強度と加工性のバランスが悪くなる。したがって、結晶粒形状ｄ２／ｄ１は、０．６０以上とする。好ましくは０．７０以上、より好ましくは０．７５以上である。 When the crystal grain shape d2 / d1 is smaller than 0.60, the pressure strength is lowered with respect to the tensile strength, and the balance between strength and workability is deteriorated. Therefore, the crystal grain shape d2 / d1 is set to 0.60 or more. Preferably it is 0.70 or more, More preferably, it is 0.75 or more.
（析出物の平均直径）
析出物の直径は、透過型電子顕微鏡（ＴＥＭ）を用いて１０万倍の倍率で観察を行い、測定する。膜厚１００ｎｍのもとで、５００ｎｍ×５００ｎｍの範囲で観察される析出物について、画像解析ソフトImage Pro Plus（Media Cybernetics社製）を用いて測定し、平均値を求める。ここで、析出物の平均直径は、析出物の直径が１〜１００ｎｍのもののみを対象として測定する。
(Average diameter of precipitate)
The diameter of the precipitate is measured by observation at a magnification of 100,000 times using a transmission electron microscope (TEM). Precipitates observed in a range of 500 nm × 500 nm under a film thickness of 100 nm are measured using image analysis software Image Pro Plus (manufactured by Media Cybernetics), and an average value is obtained. Here, the average diameter of the precipitate is measured only for the precipitate having a diameter of 1 to 100 nm.
析出物の平均直径が１５ｎｍを越えて大きいと、析出物の粒子間距離が大きくなるため析出強化量が小さくなり、強度が不足しやすくなる。一方、析出物の平均直径が３ｎｍよりも小さいと、転位により切断されてしまうため、析出強化量が小さくなり、強度が不足しやすくなる。したがって、析出物の平均直径は、３〜１５ｎｍとする。 When the average diameter of the precipitate exceeds 15 nm, the distance between the particles of the precipitate increases, so that the precipitation strengthening amount decreases and the strength tends to be insufficient. On the other hand, when the average diameter of the precipitate is smaller than 3 nm, the precipitate is cut by dislocation, so that the precipitation strengthening amount becomes small and the strength tends to be insufficient. Therefore, the average diameter of the precipitate is 3 to 15 nm.
（析出物の数密度）
析出物の数密度は、透過型電子顕微鏡（ＴＥＭ）を用いて１０万倍の倍率で観察を行い測定する。膜厚１００ｎｍのもとで、５００ｎｍ×５００ｎｍの範囲で観察される析出物の個数を測定し、計算によって１μｍ３あたりの析出物の個数を求める。ここで析出物の数密度は、析出物の直径が１〜１００ｎｍのサイズのもののみを対象として測定する。このとき１００個未満は四捨五入する。
(Number density of precipitates)
The number density of precipitates is measured by observing at a magnification of 100,000 times using a transmission electron microscope (TEM). Under the film thickness of 100 nm, the number of precipitates observed in the range of 500 nm × 500 nm is measured, and the number of precipitates per 1 μm 3 is determined by calculation. Here, the number density of the precipitates is measured only for a precipitate having a diameter of 1 to 100 nm. At this time, less than 100 pieces are rounded off.
析出物の数密度が３０００個／μｍ３よりも少ないと、析出強化量が小さくなり、強度が不足しやすくなる。したがって、析出物の数密度は３０００個／μｍ３以上とする。好ましくは５０００個／μｍ３以上である。析出物の数密度に上限はないが、本合金の成分範囲では１０万個／μｍ３が限界である。 When the number density of precipitates is less than 3000 / μm 3 , the precipitation strengthening amount becomes small and the strength tends to be insufficient. Therefore, the number density of the precipitates is set to 3000 pieces / μm 3 or more. The number is preferably 5000 / μm 3 or more. There is no upper limit to the number density of precipitates, but 100,000 / μm 3 is the limit in the composition range of this alloy.
〔高強度銅管の製造方法〕
次に、本発明に係る高強度銅管の製造方法の一例を示す。本発明に係る高強度銅管は、公知の銅管と同様にして、鋳造、均質化処理、熱間押出、圧延、抽伸、溶体化処理、最終焼鈍の工程を経て製造することができる。各材料の鋳造、均質化処理、熱間押出、圧延、抽伸の各条件は、公知の常法に従って行うことができる。
[Method of manufacturing high-strength copper pipe]
Next, an example of the manufacturing method of the high intensity | strength copper pipe which concerns on this invention is shown. The high-strength copper pipe according to the present invention can be manufactured through the steps of casting, homogenization treatment, hot extrusion, rolling, drawing, solution treatment, and final annealing in the same manner as known copper pipes. Each condition of casting, homogenization treatment, hot extrusion, rolling and drawing of each material can be performed according to a known ordinary method.
但し、析出物の直径、数密度および結晶粒形状を制御するためには、最終焼鈍による析出に加えて、溶体化処理工程において再結晶、溶体化を行うことが重要であり、またこの溶体化処理工程の昇温速度が重要となる。 However, in order to control the diameter, number density and crystal grain shape of the precipitates, it is important to perform recrystallization and solution treatment in the solution treatment process in addition to the precipitation by final annealing. The rate of temperature increase in the processing process is important.
銅合金の鋳造によって製造されたビレットに対して、均質化処理、熱間押出、圧延加工、粗抽伸加工を行う。その後、溶体化処理を８００〜１０００℃で、３０秒以下にて行い、再結晶および溶体化を行う。好ましくは、８５０〜９５０℃である。このときの溶体化処理の昇温速度は５０℃／秒以上とすることが好ましい。より好ましくは、１００℃／秒以上である。 Homogenization, hot extrusion, rolling, and rough drawing are performed on billets manufactured by copper alloy casting. Thereafter, solution treatment is performed at 800 to 1000 ° C. for 30 seconds or less, and recrystallization and solution treatment are performed. Preferably, it is 850-950 degreeC. At this time, the temperature raising rate of the solution treatment is preferably 50 ° C./second or more. More preferably, it is 100 ° C./second or more.
本発明者らは、溶体化処理工程において、昇温速度を大きく、かつ高温短時間の条件で行うことによって、結晶粒形状が等軸に近づくことを見出した。具体的には、溶体化処理温度が８５０℃よりも低温の場合、溶体化処理の時点で粗大な析出物が生成してしまい、平均析出物直径が１５ｎｍより大きくなりやすく、その後の時効処理で生成する析出物が減少し、数密度が３０００個／μｍ３未満になりやすい。 The inventors of the present invention have found that in the solution treatment step, the crystal grain shape approaches the same axis by increasing the temperature rising rate and under the conditions of high temperature and short time. Specifically, when the solution treatment temperature is lower than 850 ° C., coarse precipitates are generated at the time of the solution treatment, and the average precipitate diameter tends to be larger than 15 nm. The generated precipitates are reduced, and the number density tends to be less than 3000 / μm 3 .
また、溶体化処理温度が低過ぎると、結晶粒径の形状が伸張しやすく、ｄ２／ｄ１が０．６０未満となりやすく、その結果、破壊圧力が不足しやすくなる。一方、溶体化処理温度が１０００℃よりも高温、または溶体化処理時間が３０ｓｅｃよりも長時間の場合は、長手方向の結晶粒径ｄ１が４０μｍよりも大きくなりやすく、その結果加工性が劣化しやすくなる。 On the other hand, if the solution treatment temperature is too low, the shape of the crystal grain size tends to stretch, and d2 / d1 tends to be less than 0.60. As a result, the fracture pressure tends to be insufficient. On the other hand, when the solution treatment temperature is higher than 1000 ° C. or the solution treatment time is longer than 30 seconds, the crystal grain size d1 in the longitudinal direction tends to be larger than 40 μm, and as a result, workability deteriorates. It becomes easy.
溶体化処理の昇温速度が５０℃／秒未満では、結晶粒径が伸張しやすく、破壊圧力が低くなりやすい。このメカニズムは十分には明らかではないが以下のように考えている。再結晶には新たに再結晶粒が生じる不連続再結晶と、ひずみが連続的に低下する連続再結晶があり、不連続再結晶の場合は比較的等軸粒となりやすく、連続再結晶の場合は管長手方向に伸張した結晶粒となりやすい。また高温で再結晶させるときは、不連続再結晶となりやすく、低温で再結晶するときは連続再結晶となりやすい。このため、昇温速度が小さい場合は、昇温途中の比較的低温で再結晶が開始してしまうため、結晶粒形状が管軸長手方向に伸張した組織になると考えている。 When the temperature increase rate of the solution treatment is less than 50 ° C./second, the crystal grain size is likely to expand, and the breaking pressure tends to be low. Although this mechanism is not clear enough, I think as follows. There are two types of recrystallization: discontinuous recrystallization, in which new recrystallized grains are generated, and continuous recrystallization, in which the strain decreases continuously. Tends to be crystal grains stretched in the longitudinal direction of the tube. When recrystallizing at a high temperature, discontinuous recrystallization tends to occur, and when recrystallizing at a low temperature, continuous recrystallization tends to occur. For this reason, when the rate of temperature rise is small, recrystallization starts at a relatively low temperature during the temperature rise, so that it is considered that the crystal grain shape becomes a structure extending in the longitudinal direction of the tube axis.
溶体化処理後に、抽伸加工により抽伸管（平滑管）とする。その後に行う最終焼鈍の条件が重要である。最終焼鈍は、焼鈍温度４５０〜７００℃で、焼鈍温度に応じて、焼鈍時間５分間〜１時間程度で行う。好ましくは、焼鈍温度５００〜７００℃である。 After the solution treatment, a drawing tube (smooth tube) is formed by drawing. The conditions of the final annealing performed after that are important. The final annealing is performed at an annealing temperature of 450 to 700 ° C. and an annealing time of about 5 minutes to about 1 hour depending on the annealing temperature. Preferably, the annealing temperature is 500 to 700 ° C.
抽伸管を４５０〜７００℃で５分間〜１時間程度保持して最終焼鈍を行うことによって、加工硬化した抽伸管を軟質化させて曲げ加工等を可能とすることに加え、さらに析出物を分散させることができる。 By holding the drawing tube at 450-700 ° C. for about 5 minutes to 1 hour and performing final annealing, in addition to softening the work-hardened drawing tube and enabling bending, etc., the precipitate is further dispersed. Can be made.
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
〔高強度銅管の作製〕
供試材として銅管を以下の工程により作製した。
電気銅を原料とした溶湯中に、表１に示した成分組成にしたがって、Ｎｉ等を添加した後、Ｃｕ−Ｐ合金を添加して、鋳造温度１２００℃で、直径３００ｍｍ、長さ３０００ｍｍの鋳塊を半連続鋳造した。鋳塊から長さ４７５ｍｍのビレットを切り出し、均質化処理としてビレットを６８０〜８００℃の範囲に加熱して１時間保持した。その後、熱間押出して、外径１００ｍｍ、肉厚１０ｍｍの押出素管を作製し、水冷にて表面温度が３００℃になるまで冷却速度２０℃／秒以上で急速冷却した。
[Production of high-strength copper tube]
A copper tube was produced as a test material by the following steps.
In accordance with the composition shown in Table 1, Ni or the like is added to the molten metal made of electrolytic copper as a raw material, and then a Cu-P alloy is added. The casting temperature is 1200 ° C., the diameter is 300 mm, and the length is 3000 mm. The lump was semi-continuously cast. A billet having a length of 475 mm was cut out from the ingot, and the billet was heated to a range of 680 to 800 ° C. and held for 1 hour as a homogenization treatment. Thereafter, it was hot-extruded to produce an extruded element tube having an outer diameter of 100 mm and a wall thickness of 10 mm, and rapidly cooled at a cooling rate of 20 ° C./second or more until the surface temperature reached 300 ° C. by water cooling.
この押出素管を圧延し、さらに粗抽伸した。その後、表１に記載の条件で、溶体化処理を行った。但し、供試材Ｎｏ．２５と２６は溶体化処理を行わなかった。溶体化処理後、さらに抽伸して、外径９．５２ｍｍ、肉厚０．８０ｍｍの平滑管を作製した。その後、平滑管に対して、表１に記載の条件で、最終焼鈍を行い、銅管を作製した。 The extruded element tube was rolled and further rough drawn. Thereafter, a solution treatment was performed under the conditions described in Table 1. However, the test material No. 25 and 26 did not perform solution treatment. After the solution treatment, drawing was further performed to produce a smooth tube having an outer diameter of 9.52 mm and a wall thickness of 0.80 mm. Thereafter, the smooth tube was subjected to final annealing under the conditions described in Table 1 to produce a copper tube.
銅管の作製途中の工程にて不具合により作製を中断したものは、以降の測定および評価を行わず、表２の測定値等の欄を「−」で表した。 In the case where the production was interrupted due to a defect in the process of producing the copper tube, the subsequent measurement and evaluation were not performed, and the column of measured values and the like in Table 2 was represented by “−”.
作製した銅管について、以下に記載する方法で、平均結晶粒径、析出物の平均直径と数密度を測定し、その結果を表２に示した。 With respect to the produced copper tube, the average crystal grain size, the average diameter and the number density of the precipitates were measured by the method described below, and the results are shown in Table 2.
（長手方向の平均結晶粒径ｄ１、肉厚方向の平均結晶粒径ｄ２）
ＥＢＳＰシステムを搭載したＦＥＳＥＭを使用し、結晶方位解析法を用いて、ＳＥＭ−ＥＢＳＰ法によって、銅管の管軸方向に平行な断面において測定を行なった。測定エリアとして、管軸方向８００μｍ×管肉厚方向４００μｍに対して１．０μｍのピッチで電子線を照射し、結晶粒に関するデータを取得した。そして、管軸長手方向に線を５０本引き、線と交わる粒の平均切片長さＬ１を解析で求めた。求めたＬ１から計算によって管軸長手方向の平均結晶粒径ｄ１を求めた。同様にして、管肉厚方向の平均結晶粒径ｄ２を求めた。ｄ１とｄ２の数値から、ｄ２／ｄ１を算出した。
(Average crystal grain size d1 in the longitudinal direction, average crystal grain size d2 in the thickness direction)
Using a FESEM equipped with an EBSP system and using a crystal orientation analysis method, measurement was performed on a cross section parallel to the tube axis direction of the copper tube by the SEM-EBSP method. As a measurement area, electron beams were irradiated at a pitch of 1.0 μm with respect to a tube axis direction of 800 μm × tube thickness direction of 400 μm, and data on crystal grains were obtained. Then, 50 lines were drawn in the longitudinal direction of the tube axis, and the average section length L1 of the grains intersecting with the line was obtained by analysis. The average crystal grain size d1 in the longitudinal direction of the tube axis was determined by calculation from the determined L1. Similarly, the average crystal grain size d2 in the tube thickness direction was determined. d2 / d1 was calculated from the numerical values of d1 and d2.
（析出物の平均直径）
析出物の直径は、ＴＥＭを用いて１０万倍の倍率で測定した。膜厚１００ｎｍのもとで、５００ｎｍ×５００ｎｍの範囲で観察される析出物について、画像解析ソフトImage Pro Plus（Media Cybernetics社製）を用いて測定し、平均値を求めた。ここで、析出物の平均直径は、析出物の直径が１〜１００ｎｍのもののみを対象として測定した。
(Average diameter of precipitate)
The diameter of the precipitate was measured using a TEM at a magnification of 100,000 times. Precipitates observed in a range of 500 nm × 500 nm under a film thickness of 100 nm were measured using image analysis software Image Pro Plus (manufactured by Media Cybernetics), and an average value was obtained. Here, the average diameter of the precipitate was measured only for the precipitate having a diameter of 1 to 100 nm.
（析出物の数密度）
析出物の数密度は、ＴＥＭを用いて１０万倍の倍率で測定した。膜厚１００ｎｍのもとで、５００ｎｍ×５００ｎｍの範囲で観察される析出物の個数を測定し、計算によって１μｍ３あたりの析出物の個数を求めた。ここで析出物の数密度は、析出物の直径が１〜１００ｎｍのサイズのもののみを対象として測定した。このとき１００個未満は四捨五入した。
(Number density of precipitates)
The number density of the precipitates was measured at a magnification of 100,000 times using TEM. The number of precipitates observed within a range of 500 nm × 500 nm was measured under a film thickness of 100 nm, and the number of precipitates per 1 μm 3 was determined by calculation. Here, the number density of the precipitates was measured only for a precipitate having a diameter of 1 to 100 nm. At this time, less than 100 pieces were rounded off.
〔評価〕
作製した銅管について、引張強さ、耐圧強度、耐圧強度／引張強さ、曲げ加工性、耐応力腐食割れ性を、以下に記載する方法で評価した。評価結果を表２に示した。
[Evaluation]
About the produced copper pipe, the tensile strength, the pressure strength, the pressure strength / tensile strength, the bending workability, and the stress corrosion cracking resistance were evaluated by the methods described below. The evaluation results are shown in Table 2.
（引張強さ）
銅管を切り出して、ＪＩＳ１１号引張試験片を各供試材毎に２本作製した。この試験片をＪＩＳ Ｚ２２４１に準じて引張試験を室温にて行った。詳しくは、５８８２型インストロン社製万能試験機により、試験速度１０．０ｍｍ／分、ＧＬ＝５０ｍｍで、引張強さを測定した。２本の平均値として求めた。引張強さの合格基準は、２７０ＭＰａ以上とする。
(Tensile strength)
The copper tube was cut out and two JIS No. 11 tensile test pieces were produced for each specimen. This specimen was subjected to a tensile test at room temperature according to JIS Z2241. Specifically, the tensile strength was measured at a test speed of 10.0 mm / min and GL = 50 mm using a 5882 type Instron universal testing machine. It calculated | required as an average value of two. The acceptance criterion for tensile strength is 270 MPa or more.
（耐圧強度）
作製した銅管から３００ｍｍの長さの銅管を試験用に採取した。銅管の一方の端部を金属製治具（ボルト）にて耐圧的に閉塞した。そして、もう一方の開放側端部から、ポンプにて管内に負荷される水圧を徐々に高めていき（昇圧速度：１．５ＭＰａ／秒程度）、完全に管が破裂する際の水圧（ＭＰａ）を、ブルドン管式圧力計で読み取り、伝熱管の破壊強度（耐圧強度、耐圧性能、破壊圧力）とした。この試験を各供試材に対して５回（試験管５個に対して）行い、各水圧（ＭＰａ）の平均値を破壊強度とした。また破壊強度から銅管の肉厚や外径の影響を取り除いた、換算応力を求めた。ここで耐圧強度σは、破壊強度をＰ、銅管の外径をＤ、銅管の肉厚をｔとしたとき、下記の式から求めた。
σ＝Ｐ×（Ｄ−ｔ）／（２×ｔ）
耐圧強度の合格基準は、２５０ＭＰａ以上とする。
(Pressure strength)
A copper tube having a length of 300 mm was collected from the prepared copper tube for testing. One end of the copper tube was closed in a pressure-resistant manner with a metal jig (bolt). Then, from the other open side end, the water pressure loaded into the pipe by the pump is gradually increased (pressure increase rate: about 1.5 MPa / second), and the water pressure (MPa) when the pipe completely ruptures. Was read with a Bourdon tube pressure gauge and used as the breaking strength (pressure resistance, pressure resistance, breaking pressure) of the heat transfer tube. This test was performed five times for each test material (for five test tubes), and the average value of each water pressure (MPa) was taken as the fracture strength. Moreover, the conversion stress which remove | eliminated the influence of the thickness and outer diameter of a copper pipe from fracture strength was calculated | required. Here, the pressure strength σ was determined from the following equation, where P is the breaking strength, D is the outer diameter of the copper tube, and t is the thickness of the copper tube.
σ = P × (D−t) / (2 × t)
The acceptance criteria for the pressure strength is 250 MPa or more.
（耐圧強度／引張強さ）
上記の引張強さと耐圧強度の数値から、耐圧強度／引張強さを算出した。耐圧強度／引張強さの合格基準は、０．９以上とする。
(Pressure strength / tensile strength)
The pressure strength / tensile strength was calculated from the above values of tensile strength and pressure strength. The acceptance criteria of pressure strength / tensile strength is 0.9 or more.
（曲げ加工性）
銅管を、曲げピッチ２５ｍｍ（管軸における曲げ半径が１２．５ｍｍ）のＵ字形に曲げ加工し、外側表面の曲げ部を目視にて観察した。各供試材毎に１０本について行い、割れや亀裂が観察されたものが５本以下であれば合格とし、１０本すべてに割れ等のないものを「○」、割れ等が観察されたものが１本以上５本以下を「△」、６本以上を不合格として「×」とした。
(Bending workability)
The copper tube was bent into a U shape with a bending pitch of 25 mm (bending radius at the tube axis was 12.5 mm), and the bent portion on the outer surface was visually observed. The test was conducted for 10 specimens for each specimen. If 5 or less cracks or cracks were observed, the test was accepted, and all 10 specimens were free of cracks. Of 1 or more and 5 or less were evaluated as “Δ”, and 6 or more were evaluated as “failed” as “x”.
（耐応力腐食割れ性）
銅管を長さ７５ｍｍに切り出して試験片とし、試験片を脱脂、乾燥させた。ＪＩＳ Ｋ８０８５に規定するアンモニア水を等量の純水で希釈した１１．８％以上のアンモニア水を入れたデシケーター中に、液面から５０ｍｍの距離を空けた高さ位置に、試験片を固定して収容し、アンモニア雰囲気中に常温で２時間保持した。その後、試験片を銅管の元の外径の５０％まで径方向に押しつぶした。この試験片を目視で観察して外周面の割れの有無を判定した。割れのないものを合格として「○」、割れの発生したものを「×」とした。
(Stress corrosion cracking resistance)
The copper tube was cut into a length of 75 mm to obtain a test piece, and the test piece was degreased and dried. In a desiccator containing 11.8% or more of ammonia water diluted with an equal volume of pure water as specified in JIS K8085, fix the test piece at a height of 50 mm away from the liquid surface. And kept in an ammonia atmosphere at room temperature for 2 hours. Thereafter, the test piece was crushed in the radial direction to 50% of the original outer diameter of the copper tube. The test piece was visually observed to determine the presence or absence of cracks on the outer peripheral surface. Those with no cracks were accepted as “◯”, and those with cracks were marked “x”.
表１および表２に示すように、供試材Ｎｏ．１〜１７は、銅合金の成分組成、結晶粒径（ｄ１、ｄ２／ｄ１）および析出物の平均直径、数密度がいずれも本発明の要件を満足する実施例であり、引張強さ、耐圧強度、耐圧強度／引張強さ、曲げ加工性、耐応力腐食割れ性がいずれも良好であった。 As shown in Table 1 and Table 2, the test material No. Nos. 1 to 17 are examples in which the composition of the copper alloy, the crystal grain size (d1, d2 / d1), the average diameter of the precipitates, and the number density all satisfy the requirements of the present invention. The strength, pressure strength / tensile strength, bending workability, and stress corrosion cracking resistance were all good.
これに対して、供試材Ｎｏ．１８〜２４は、銅合金の成分組成が本発明の要件を満足しない比較例である。
供試材Ｎｏ．１８は、Ｃｏの含有量が少ないため、結晶粒が粗大化し、析出物の数密度が少なくなるため、十分な引張強さや耐圧強度を得ることができなかった。供試材Ｎｏ．１９は、Ｃｏの含有量が過剰であり、析出物が過剰に析出するため、加工性が低下して、熱間押出時に割れが生じた。
供試材Ｎｏ．２０は、Ｐの含有量が少なく、結晶粒が粗大化し、十分な引張強さや耐圧強度を得ることができなかった。供試材Ｎｏ．２１は、Ｐの含有量が過剰であり、加工性が低下して、熱間押出時に割れが生じた。
供試材Ｎｏ．２２は、Ｓｎの含有量が過剰であり、鋳塊における凝固偏析が激しくなって、熱間押出ができなかった。供試材Ｎｏ．２３は、Ｚｎの含有量が過剰であり、耐応力腐食割れ性に劣るものとなった。
供試材Ｎｏ．２４は、Ｃｒの含有量が過剰であり、熱間押出温度を高くなり、表面欠陥が増大して、曲げ加工性に劣るものとなった。
On the other hand, the test material No. 18 to 24 are comparative examples in which the component composition of the copper alloy does not satisfy the requirements of the present invention.
Specimen No. In No. 18, since the Co content is small, the crystal grains are coarsened, and the number density of precipitates is reduced, so that sufficient tensile strength and pressure strength cannot be obtained. Specimen No. In No. 19, since the Co content was excessive and the precipitates were excessively precipitated, the workability was lowered and cracking occurred during hot extrusion.
Specimen No. In No. 20, the P content was small, the crystal grains became coarse, and sufficient tensile strength and compressive strength could not be obtained. Specimen No. In No. 21, the P content was excessive, the workability was lowered, and cracking occurred during hot extrusion.
Specimen No. In No. 22, the Sn content was excessive, solidification segregation in the ingot became severe, and hot extrusion could not be performed. Specimen No. No. 23 had an excessive Zn content and was inferior in stress corrosion cracking resistance.
Specimen No. In No. 24, the Cr content was excessive, the hot extrusion temperature was increased, surface defects were increased, and the bending workability was inferior.
供試材Ｎｏ．２５〜３１は、銅管の製造条件が、本発明の好ましい条件を満足していない比較例である。
供試材Ｎｏ．２５は、溶体化処理を行っておらず、かつ最終焼鈍が５５０℃と比較的低温のため、結晶粒が再結晶化せず、耐圧強度／引張強さと曲げ加工性に劣るものとなった。一方で、溶体化処理を行っていないものの、最終焼鈍が比較的低温のため、析出物は好ましい範囲となった。
供試材Ｎｏ．２６は、溶体化処理を行っていないが、最終焼鈍が６５０℃と比較的高温のため再結晶が生じ、結晶粒は好ましい範囲となった。しかし溶体化処理を行っておらず、最終焼鈍が比較的高いため、析出物の数密度が少ないものとなり、引張強さや耐圧強度が不十分なものであった。
供試材Ｎｏ．２７は、溶体化処理温度が低いため、結晶粒径の形状が伸張しやすく、ｄ２／ｄ１が０．６０未満となり、析出物の数密度も少なくなり、引張強さや耐圧強度が不十分なものであった。供試材Ｎｏ．２８は、溶体化処理温度が高温であるため、長手方向の平均結晶粒径ｄ１が過大となり、曲げ加工性に劣るものとなった。供試材Ｎｏ．２９は、溶体化処理の昇温速度が低いため、結晶粒径が伸張しやすく、耐圧強度に劣るものとなった。
供試材Ｎｏ．３０は、最終焼鈍の温度が低いため、析出物を分散させることが不十分となり、引張強さや耐圧強度が不十分なものであった。供試材Ｎｏ．３１は、最終焼鈍の温度が高いため、析出物が過大なものとなり、析出物の数密度が低下して、引張強さや耐圧強度が不十分なものとなった。
Specimen No. Nos. 25 to 31 are comparative examples in which the copper tube production conditions do not satisfy the preferred conditions of the present invention.
Specimen No. No. 25 was not subjected to solution treatment, and the final annealing was relatively low at 550 ° C., so the crystal grains were not recrystallized, and the pressure strength / tensile strength and bending workability were inferior. On the other hand, although the solution treatment was not performed, since the final annealing was relatively low temperature, the precipitate was in a preferable range.
Specimen No. No. 26 was not subjected to a solution treatment, but the final annealing was relatively high at 650 ° C., so recrystallization occurred, and the crystal grains were in a preferred range. However, since the solution treatment was not performed and the final annealing was relatively high, the number density of the precipitates was small, and the tensile strength and pressure strength were insufficient.
Specimen No. In No. 27, since the solution treatment temperature is low, the shape of the crystal grain size tends to expand, d2 / d1 is less than 0.60, the number density of precipitates is reduced, and the tensile strength and pressure resistance are insufficient. It was. Specimen No. In No. 28, since the solution treatment temperature was high, the average crystal grain size d1 in the longitudinal direction was excessive, and the bending workability was poor. Specimen No. No. 29 had a low temperature rise rate in the solution treatment, so that the crystal grain size was easily stretched and the pressure strength was inferior.
Specimen No. No. 30 had a low final annealing temperature, so that it was insufficient to disperse the precipitate, and the tensile strength and pressure strength were insufficient. Specimen No. In No. 31, since the final annealing temperature was high, the precipitates became excessive, the number density of the precipitates decreased, and the tensile strength and pressure resistance were insufficient.
Claims (3)
管軸方向に平行な断面におけるＳＥＭ−ＥＢＳＰ法による測定で、長手方向の平均結晶粒径をｄ１、肉厚方向の平均結晶粒径をｄ２としたときに、ｄ１が４０μｍ以下、ｄ２／ｄ１が０．６０以上であり、
析出物の平均直径が３〜１５ｎｍであり、
前記析出物の数密度が３０００個／μｍ３以上であることを特徴とする高強度銅合金管。 Co: 0.13-0.40% by mass, P: 0.02-0.1% by mass, with the balance being Cu and an inevitable impurity copper alloy,
In the measurement by the SEM-EBSP method in a cross section parallel to the tube axis direction, when the average crystal grain size in the longitudinal direction is d1 and the average crystal grain size in the thickness direction is d2, d1 is 40 μm or less and d2 / d1 is 0.60 or more,
The average diameter of the precipitate is 3-15 nm,
A high-strength copper alloy tube, wherein the number density of the precipitates is 3000 pieces / μm 3 or more.
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