JP2017137581A - Aluminum-made clad tube and manufacturing method therefor - Google Patents
Aluminum-made clad tube and manufacturing method therefor Download PDFInfo
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本発明は、ルームエアコンの配管、自動車用熱交換器の配管、自動車及び各種産業用機器の配管に用いられ、耐食性に優れたアルミニウム製クラッド管に関する。 The present invention relates to an aluminum clad pipe having excellent corrosion resistance, which is used in piping for room air conditioners, piping for heat exchangers for automobiles, piping for automobiles and various industrial equipment.
従来のアルミニウム製クラッド管としては、３０００系の母材にＺｎ溶射により犠牲防食層を付与する方法（特許文献１）、或いは、Ａｌ−Ｚｎ合金クラッドにより犠牲防食層を付与する方法等（特許文献２）によって、Ｚｎにより耐食性を向上させたものが提案されている。 As a conventional aluminum clad tube, a method of providing a sacrificial anticorrosion layer by spraying Zn on a 3000 series base material (Patent Document 1), a method of applying a sacrificial anticorrosion layer by Al-Zn alloy cladding, etc. (Patent Document) According to 2), a material whose corrosion resistance is improved by Zn is proposed.
しかしながら、これら先行技術において用いられるＺｎは、腐食速度を速めるために早期に犠牲防食層が消費されてしまい、目標とする寿命が得られない問題があった。また、Ｚｎは将来的に枯渇するとされており、Ｚｎを用いない防食手法の確立が求められている。 However, the Zn used in these prior arts has a problem that the sacrificial anticorrosive layer is consumed at an early stage in order to increase the corrosion rate, and the target life cannot be obtained. In addition, Zn is supposed to be depleted in the future, and establishment of a corrosion prevention method that does not use Zn is required.
本発明は上記問題等に鑑みてなされたものであり、Ｚｎを用いずに耐食性に優れたアルミニウム製クラッド管を提供することを目的とする。 The present invention has been made in view of the above problems, and an object thereof is to provide an aluminum clad tube excellent in corrosion resistance without using Zn.
上記課題を解決するため、本発明者等は、犠牲陽極材層中におけるＭｇ−Ｓｉ系晶出物の面密度に注目し、これを所定以下とすることにより十分な防食効果が発揮できることを見出した。更に、本発明者等は、犠牲陽極材層中においてマトリックスより電位の卑な金属間化合物である微細なＭｇ−Ｓｉ系析出物に着目した。具体的には、Ｚｎが存在しない状態においても、この所定の大きさの析出物の体積密度を所定範囲とすることによる防食効果によって十分な耐食性が発揮されることを見出し、本発明を完成するに至った。 In order to solve the above-mentioned problems, the present inventors have found that a sufficient anticorrosion effect can be exerted by paying attention to the surface density of the Mg—Si-based crystallized material in the sacrificial anode material layer, and making it below a predetermined value. It was. Furthermore, the present inventors paid attention to fine Mg—Si-based precipitates, which are intermetallic compounds having a lower potential than the matrix in the sacrificial anode material layer. Specifically, even in the absence of Zn, the present inventors have found that sufficient corrosion resistance is exhibited by the anticorrosion effect by setting the volume density of precipitates of a predetermined size within a predetermined range, and the present invention is completed. It came to.
本発明は請求項１において、アルミニウム管の心材と、当該心材の内面及び外面の少なくとも一方にクラッドされた犠性陽極材層を備えるアルミニウム製クラッド管において、前記犠性陽極材層が、Ｓｉ：０．１０〜１．５０ｍａｓｓ％、Ｍｇ：０．１０〜２．００ｍａｓｓ％を含有し、Ｚｎ：０．０５ｍａｓｓ％以下に規制され、残部Ａｌ及び不可避的不純物からなるアルミニウム合金からなり、前記犠性陽極材層に存在する円相当直径１．０〜１０μｍのＭｇ−Ｓｉ系晶出物が３００００個／ｍｍ２以下であり、１７５℃で５時間の増感処理後に、前記犠牲陽極材層表面から５μｍまでの深さの領域において観察され、当該犠牲陽極材のマトリックスより電位が卑な長さ１０〜１０００ｎｍのＭｇ−Ｓｉ系析出物が１０００〜５００００個／μｍ３であることを特徴とするアルミニウム製クラッド管とした。 According to a first aspect of the present invention, in the aluminum clad tube comprising the core material of the aluminum tube and the sacrificial anode material layer clad on at least one of the inner surface and the outer surface of the core material, the sacrificial anode material layer is Si: Containing 0.10 to 1.50 mass%, Mg: 0.10 to 2.00 mass%, Zn: regulated to 0.05 mass% or less, consisting of an aluminum alloy composed of the balance Al and unavoidable impurities, the sacrificial property 30000 pieces / mm 2 or less of Mg—Si based crystals having an equivalent circle diameter of 1.0 to 10 μm existing in the anode material layer, and after sensitizing treatment at 175 ° C. for 5 hours, from the surface of the sacrificial anode material layer observed in the depth of the region of up to 5 [mu] m, the potential from the matrix of the sacrificial anode material is Mg-Si based precipitate of less noble length 10 to 1000 nm 1,000 to 50,000 / Was aluminum cladding tube, characterized in that μm 3.
本発明は請求項２では請求項１において、前記犠牲陽極材層のアルミニウム合金が、Ｆｅ：０．０５〜１．００ｍａｓｓ％、Ｎｉ：０．０５〜１．００ｍａｓｓ％、Ｃｕ：０．０５〜１．００ｍａｓｓ％、Ｍｎ：０．０５〜１．５０ｍａｓｓ％、Ｔｉ：０．０５〜０．３０ｍａｓｓ％、Ｚｒ：０．０５〜０．３０ｍａｓｓ％、Ｃｒ：０．０５〜０．３０ｍａｓｓ％及びＶ：０．０５〜０．３０ｍａｓｓ％から選択される１種以上を更に含有するものとした。 According to a second aspect of the present invention, in the first aspect, the aluminum alloy of the sacrificial anode material layer includes Fe: 0.05 to 1.00 mass%, Ni: 0.05 to 1.00 mass%, Cu: 0.05 to 1.00 mass%, Mn: 0.05 to 1.50 mass%, Ti: 0.05 to 0.30 mass%, Zr: 0.05 to 0.30 mass%, Cr: 0.05 to 0.30 mass%, and V : One or more selected from 0.05 to 0.30 mass%.
本発明は請求項３では請求項１又は２において、前記アルミニウム管の心材の内面及び外面の一方に犠性陽極材層がクラッドされており、他方にろう材層がクラッドされているものとした。 According to a third aspect of the present invention, in the first or second aspect, the sacrificial anode material layer is clad on one of the inner surface and the outer surface of the core of the aluminum tube, and the brazing material layer is clad on the other. .
また本発明は、請求項１〜３のいずれか一項に記載のアルミニウム製クラッド管の製造方法であって、前記犠牲陽極材層用のアルミニウム合金を半連続鋳造する半連続鋳造工程と；犠牲陽極材層用の鋳塊をアルミニウム管の心材の内面及び外面の少なくとも一方に組み合わせてビレットとする組み合わせ工程と；前記ビレットを押出成形する押出成形工程と；を備え、前記半連続鋳造工程における鋳塊表面の冷却速度を１℃／秒以上とし、前記押出成形工程前にビレットを４５０〜５７０℃に加熱する加熱工程と；前記押出成形工程後にクラッド押出管を０．１〜１０００℃／秒の速度で冷却する冷却工程と；を更に備えることを特徴とするアルミニウム製クラッド管の製造方法とした。 Moreover, this invention is a manufacturing method of the aluminum clad pipe | tube as described in any one of Claims 1-3, Comprising: The semi-continuous casting process which semi-continuously casts the aluminum alloy for the said sacrificial anode material layers; A casting step in the semi-continuous casting step, comprising: a combination step of combining an ingot for an anode material layer with at least one of an inner surface and an outer surface of a core material of an aluminum tube to form a billet; and an extrusion molding step of extruding the billet. A heating step in which the cooling rate of the lump surface is set to 1 ° C./second or more, and the billet is heated to 450 to 570 ° C. before the extrusion molding step; A cooling step of cooling at a speed; and a method of manufacturing an aluminum clad tube.
更に本発明は上記アルミニウム製クラッド管の製造方法において、前記冷却工程後に、クラッド押出管を１００〜３００℃で５分間以上熱処理する熱処理工程を更に備えるものとした。 Furthermore, the present invention further includes a heat treatment step of heat-treating the clad extruded tube at 100 to 300 ° C. for 5 minutes or more after the cooling step in the method for producing the aluminum clad tube.
本発明に係るアルミニウム製クラッド管は、ルームエアコンの配管、自動車用熱交換器の配管、自動車及び各種産業用機器の配管として、大気環境、塩害環境、海水環境、酸性やアルカリ性の特殊環境等においても良好な耐食性を発揮することができる。 The aluminum clad pipe according to the present invention is used as piping for room air conditioners, piping for heat exchangers for automobiles, piping for automobiles and various industrial equipment, in atmospheric environment, salt damage environment, seawater environment, acidic or alkaline special environment, etc. Can exhibit good corrosion resistance.
１．アルミニウム製クラッド管
１−１．構造
本発明に係るアルミニウム製クラッド管は、ルームエアコンの配管、自動車用熱交換器の配管、自動車及び各種産業用機器の配管などに好適に用いられる。このような配管は、アルミニウム管の心材の内面及び外面のいずれか一方に犠牲陽極材層をクラッドした二層クラッド管として構成される。例えば、犠牲陽極材層側が外部環境に曝される配管外面となるように管状に成形される。管内部が、フロンなどの冷媒の流路となる。
1. 1. Aluminum clad tube 1-1. Structure The aluminum clad pipe according to the present invention is suitably used for piping for room air conditioners, piping for heat exchangers for automobiles, piping for automobiles and various industrial equipment, and the like. Such a pipe is configured as a two-layer clad pipe in which a sacrificial anode material layer is clad on either the inner surface or the outer surface of the core material of the aluminum tube. For example, the sacrificial anode material layer side is formed into a tubular shape so as to be an outer surface of a pipe exposed to the external environment. The inside of the tube serves as a flow path for a refrigerant such as chlorofluorocarbon.
これに代わって、犠牲陽極材層側が配管内面になるように成形してもよい。また、犠牲陽極材層／心材／ろう材層の三クラッド管（犠牲陽極材層が配管の内面又は外面のいずれでもよい）、或いは、犠牲陽極材層／心材／犠牲陽極材層の三層クラッド管を用いて配管を構成してもよい。 Instead of this, the sacrificial anode material layer side may be formed to be the inner surface of the pipe. Also, a sacrificial anode material layer / core material / brazing material layer three-clad tube (the sacrificial anode material layer may be either the inner surface or the outer surface of the pipe) or a sacrificial anode material layer / heart material / sacrificial anode material layer three-layer clad You may comprise piping using a pipe | tube.
アルミニウム合金製クラッド管の犠牲陽極材層の厚さは特に限定されるものではないが、１０〜３００μｍとするのが好ましい。犠牲陽極材層の片面クラッド率は、５〜３０％とするのが好ましい。また、犠牲陽極材層／心材／ろう材層の三層クラッド管において、ろう材層の厚さは特に限定されるものではないが、１０〜３００μｍとするのが好ましい。ろう材の片面クラッド率は、５〜３０％とするのが好ましい。 The thickness of the sacrificial anode material layer of the aluminum alloy clad tube is not particularly limited, but is preferably 10 to 300 μm. The single-sided cladding rate of the sacrificial anode material layer is preferably 5 to 30%. Further, in the sacrificial anode material layer / core material / brazing material layer three-layer clad tube, the thickness of the brazing material layer is not particularly limited, but is preferably 10 to 300 μm. The single-sided cladding rate of the brazing material is preferably 5 to 30%.
１−２．合金組成
次に、本発明に係るアルミニウム製クラッド管における各構成材の組成について説明する。
1-2. Alloy Composition Next, the composition of each component in the aluminum clad tube according to the present invention will be described.
（ａ）犠牲陽極材層
犠牲陽極材層は、Ｓｉ：０．１０〜１．５０ｍａｓｓ％（以下、単に「％」と記す）、Ｍｇ：０．１０〜２．００％を含有し、残部Ａｌ及び不可避的不純物からなるアルミニウム合金からなる。すなわち、これらＳｉ及びＭｇを必須元素とする。Ｓｉ及びＭｇは、犠牲陽極材層中にＭｇとＳｉを主成分とする微細なＭｇ−Ｓｉ系析出物を形成する。このＭｇ−Ｓｉ系析出物は、ろう付後の冷却中や室温においても析出する。
(A) Sacrificial anode material layer The sacrificial anode material layer contains Si: 0.10 to 1.50 mass% (hereinafter simply referred to as “%”), Mg: 0.10 to 2.00%, and the balance Al. And an aluminum alloy composed of inevitable impurities. That is, these Si and Mg are essential elements. Si and Mg form fine Mg—Si based precipitates containing Mg and Si as main components in the sacrificial anode material layer. This Mg—Si-based precipitate is deposited during cooling after brazing and also at room temperature.
このＭｇ−Ｓｉ系析出物は、針状のβ’’相（Ｍｇ２Ｓｉ）であり、Ｃｕが添加されている場合は同一形状のＱ’’相（Ａｌ−Ｍｇ−Ｓｉ−Ｃｕ）である。Ｍｇ−Ｓｉ系析出物は、マトリックスよりも孔食電位が卑であるために優先的に溶解するので、Ｚｎを用いることなく犠牲防食効果を発現できる。また、Ｍｇ−Ｓｉ系析出物には、その溶解時にＭｇが優先的に溶出して表面にＳｉ濃縮層を形成する働きもあり、これによって耐食性が更に向上する。 This Mg—Si based precipitate is a needle-like β ″ phase (Mg 2 Si), and when Cu is added, it is a Q ″ phase (Al—Mg—Si—Cu) having the same shape. . Since Mg-Si-based precipitates are preferentially dissolved because the pitting potential is lower than that of the matrix, the sacrificial anticorrosive effect can be expressed without using Zn. Further, the Mg—Si based precipitate also has a function of preferentially eluting Mg at the time of dissolution to form a Si concentrated layer on the surface, thereby further improving the corrosion resistance.
Ｓｉ含有量とＭｇ含有量の少なくともいずれか一方が０．１０％未満の場合には、強度が低下し、クラッド管製造時に犠牲陽極材層の不均一な伸びが発生し、犠牲陽極材層のクラッド率が不均一となる。Ｓｉ含有量が１．５０％を超えると融点が低下するため、ろう付加熱時に犠牲陽極材層の一部又は全体が溶融してしまう。Ｍｇ含有量が２．００％を超えると犠牲陽極材層表面の酸化膜厚さが厚くなり、心材との良好なクラッド板を得るのが困難となる。以上により、犠牲陽極材層のＳｉ含有量を０．１０〜１．５０％、Ｍｇ含有量を０．１０〜２．００％と規定する。好ましいＳｉ含有量は０．２０〜１．００％であり、好ましいＭｇ含有量は０．３０〜１．００％である。 When at least one of the Si content and the Mg content is less than 0.10%, the strength is lowered, and the sacrificial anode material layer is unevenly stretched during the production of the clad tube. The cladding rate becomes non-uniform. Since melting | fusing point will fall when Si content exceeds 1.50%, a part or all of a sacrificial anode material layer will fuse | melt at the time of brazing addition heat. If the Mg content exceeds 2.00%, the oxide film thickness on the surface of the sacrificial anode material layer becomes thick, and it becomes difficult to obtain a good clad plate with the core material. Thus, the Si content of the sacrificial anode material layer is defined as 0.10 to 1.50%, and the Mg content is defined as 0.10 to 2.00%. A preferable Si content is 0.20 to 1.00%, and a preferable Mg content is 0.30 to 1.00%.
犠牲陽極材層のアルミニウム合金は選択的添加元素として、Ｆｅ：０．０５〜１．００ｍａｓｓ％、Ｎｉ：０．０５〜１．００ｍａｓｓ％、Ｃｕ：０．０５〜１．００ｍａｓｓ％、Ｍｎ：０．０５〜１．５０ｍａｓｓ％、Ｔｉ：０．０５〜０．３０ｍａｓｓ％、Ｚｒ：０．０５〜０．３０ｍａｓｓ％、Ｃｒ：０．０５〜０．３０ｍａｓｓ％、Ｖ：０．０５〜０．３０ｍａｓｓ％から選択される１種以上を更に含有するのが好ましい。 The aluminum alloy of the sacrificial anode material layer has, as selective additive elements, Fe: 0.05 to 1.00 mass%, Ni: 0.05 to 1.00 mass%, Cu: 0.05 to 1.00 mass%, Mn: 0 0.05 to 1.50 mass%, Ti: 0.05 to 0.30 mass%, Zr: 0.05 to 0.30 mass%, Cr: 0.05 to 0.30 mass%, V: 0.05 to 0.30 mass It is preferable to further contain one or more selected from%.
ＦｅとＮｉは、耐食性の向上に寄与する。これらの元素はＡｌの腐食速度を増大させる作用があるが、Ｆｅ系化合物やＮｉ系化合物を均一に分布させると腐食が分散し、結果として貫通寿命が向上する。ＦｅとＮｉの含有量が０．０５％未満では、貫通寿命の向上効果が不十分となる。一方、ＦｅとＮｉの含有量が１．００％を超えると、腐食速度の増大が著しくなる。以上により、ＦｅとＮｉの含有量は、０．０５〜１．００％とするのが好ましく、０．１〜０．５％とするのが更に好ましい。 Fe and Ni contribute to improvement of corrosion resistance. These elements have the effect of increasing the corrosion rate of Al. However, when the Fe-based compound and Ni-based compound are uniformly distributed, the corrosion is dispersed, and as a result, the penetration life is improved. If the content of Fe and Ni is less than 0.05%, the effect of improving the penetrating life is insufficient. On the other hand, if the content of Fe and Ni exceeds 1.00%, the increase in corrosion rate becomes significant. As described above, the content of Fe and Ni is preferably 0.05 to 1.00%, and more preferably 0.1 to 0.5%.
Ｃｕが含有されることによって、上記Ｍｇ−Ｓｉ系析出物がＱ’’相（Ａｌ−Ｍｇ−Ｓｉ−Ｃｕ）となり、この析出物をより微細に分散させることができる。そのためには、Ｃｕ含有量を０．０５％以上とするのが好ましい。但し、Ｃｕ含有量が１．００％を超えると、腐食速度の増大が著しくなる。以上により、Ｃｕ量の含有量は、０．０５〜１．００％とするのが好ましく、０．１〜０．５％とするのが更に好ましい。 By containing Cu, the Mg—Si based precipitate becomes a Q ″ phase (Al—Mg—Si—Cu), and the precipitate can be more finely dispersed. For this purpose, the Cu content is preferably 0.05% or more. However, when the Cu content exceeds 1.00%, the increase in corrosion rate becomes significant. Accordingly, the Cu content is preferably 0.05 to 1.00%, more preferably 0.1 to 0.5%.
ＭｎはＡｌ−Ｍｎ系金属間化合物として晶出又は析出して、強度の向上に寄与する。また、Ａｌ−Ｍｎ系金属間化合物はＦｅを取り込むために、不可避的不純物としてのＦｅ及び耐食性を向上させる目的で添加するＦｅによる腐食速度増大作用を抑制する働きを有する。これらの効果を得るためには、Ｍｎ含有量を０．０５％以上とするのが好ましい。但し、Ｍｎ含有量が１．５０％を超えると、巨大な金属間化合物が晶出して製造性を阻害する場合がある。以上により、Ｍｎ量の含有量は、０．０５〜１．５０％とするのが好ましく、０．１〜１．０％とするのが更に好ましい。 Mn crystallizes or precipitates as an Al—Mn intermetallic compound and contributes to the improvement of strength. Further, since the Al—Mn-based intermetallic compound takes in Fe, it has a function of suppressing the corrosion rate increasing action by Fe added as an inevitable impurity and Fe added for the purpose of improving the corrosion resistance. In order to obtain these effects, the Mn content is preferably 0.05% or more. However, if the Mn content exceeds 1.50%, a huge intermetallic compound may be crystallized to hinder manufacturability. As described above, the Mn content is preferably 0.05 to 1.50%, and more preferably 0.1 to 1.0%.
Ｔｉ、Ｚｒ、Ｃｒ及びＶは、耐食性、特に耐孔食性の向上に寄与する。アルミニウム合金中に添加されたＴｉ、Ｚｒ、Ｃｒ、Ｖは、その濃度の高い領域と濃度の低い領域とに分かれ、それらが犠牲陽極材層の板厚方向に沿って交互に積層状に分布する。ここで、濃度の低い領域は、濃度の高い領域よりも優先的に腐食することにより腐食形態が層状となる。その結果、犠牲陽極材層の板厚方向に沿った腐食に部分的に遅速が生じ、全体として腐食の進行が抑制されて耐孔食性が向上する。このような耐孔食性向上の効果を十分に得るためには、Ｔｉ、Ｚｒ、Ｃｒ、Ｖの含有量を０．０５％以上とするのが好ましい。一方、Ｔｉ、Ｚｒ、Ｃｒ、Ｖの含有量が０．３０％を超えると、鋳造時に粗大な化合物が生成されて製造性を阻害する場合がある。以上により、Ｔｉ、Ｚｒ、Ｃｒ、Ｖの含有量は０．０５〜０．３０％とするのが好ましく、０．１〜０．２％とするのが更に好ましい。 Ti, Zr, Cr and V contribute to the improvement of corrosion resistance, particularly pitting corrosion resistance. Ti, Zr, Cr, and V added to the aluminum alloy are divided into a high concentration region and a low concentration region, and they are alternately distributed in the thickness direction of the sacrificial anode material layer. . Here, the low-concentration region corrodes preferentially over the high-concentration region, and the corrosion form becomes layered. As a result, the corrosion along the thickness direction of the sacrificial anode material layer is partially slowed, and the progress of the corrosion is suppressed as a whole and the pitting corrosion resistance is improved. In order to sufficiently obtain such an effect of improving the pitting corrosion resistance, the content of Ti, Zr, Cr, V is preferably 0.05% or more. On the other hand, if the content of Ti, Zr, Cr, and V exceeds 0.30%, a coarse compound may be generated during casting, which may impair manufacturability. As described above, the content of Ti, Zr, Cr, and V is preferably 0.05 to 0.30%, and more preferably 0.1 to 0.2%.
以上述べた必須元素及び選択的添加元素の他に不可避的不純物として、Ｆｅ、Ｚｎ、Ｎａ、Ｃａ、Ｓｒ等を単独で０．０５％以下、合計で０．１５％以下含有していても、犠牲陽極材層の作用を損なうことはない。なお、不可避的不純物としてのＦｅは、選択的添加元素として積極的に含有させない場合に、地金に不純物として存在するものである。 In addition to the essential elements and selective additive elements described above, as unavoidable impurities, Fe, Zn, Na, Ca, Sr, etc. may be contained alone by 0.05% or less, and in total 0.15% or less, The function of the sacrificial anode material layer is not impaired. Note that Fe as an unavoidable impurity exists as an impurity in the base metal when not actively contained as a selective additive element.
（ｂ）心材
本発明に係るアルミニウム製クラッド管の心材の材質は、アルミニウム材であれば特に限定されるものではない。ここで、アルミニウム材とは、純アルミニウムとアルミニウム合金をいう。純アルミニウムとは、純度９９％以上のアルミニウムであって、例えば１０００系のアルミニウム材が挙げられる。アルミニウム合金としては、例えばＡｌ−Ｃｕ系（２０００系）、Ａｌ−Ｍｎ系（３０００系）、Ａｌ−Ｓｉ系（４０００系）、Ａｌ−Ｍｇ系（５０００系）、Ａｌ−Ｍｇ−Ｓｉ系（６０００系）、Ａｌ−Ｍｇ−Ｚｎ系（７０００系）等のアルミニウム材が好適に用いられる。
(B) Core Material The material of the core material of the aluminum clad tube according to the present invention is not particularly limited as long as it is an aluminum material. Here, the aluminum material means pure aluminum and an aluminum alloy. Pure aluminum is aluminum having a purity of 99% or more, and examples thereof include 1000 series aluminum materials. Examples of the aluminum alloy include Al—Cu (2000), Al—Mn (3000), Al—Si (4000), Al—Mg (5000), and Al—Mg—Si (6000). Type) and Al-Mg-Zn type (7000 type) aluminum materials are preferably used.
（ｂ）ろう材層
ろう材層に用いられるアルミニウム材は特に限定されるものではないが、通常のろう付において用いられるＡｌ−Ｓｉ系合金ろう材が好適に用いられる。例えば、ＪＩＳ４３４３、４０４５、４０４７の各アルミニウム合金（Ａｌ−７〜１３％Ｓｉ）を用いるのが好ましい。
(B) Brazing material layer The aluminum material used for the brazing material layer is not particularly limited, but an Al-Si alloy brazing material used in normal brazing is preferably used. For example, it is preferable to use each aluminum alloy (Al-7 to 13% Si) of JIS 4343, 4045, and 4047.
１−３．犠牲陽極材層中に存在するＭｇ−Ｓｉ系晶出物の面密度
本発明に係るアルミニウム製クラッド板の犠牲陽極材層には、円相当直径１．０〜１０μｍのＭｇ−Ｓｉ系晶出物が面密度として３００００個／ｍｍ２以下存在する。Ｍｇ−Ｓｉ系晶出物とは、基本的にＭｇとＳｉが原子個数比２対１で構成されるものである。この晶出物には、犠牲陽極材層に選択的添加元素としてＦｅやＣｕが含有される場合には、Ｍｇ２Ｓｉの他にＭｇ−Ｓｉ−Ｆｅ、Ｍｇ−Ｓｉ−Ｃｕの３元組成や、Ｍｇ−Ｓｉ−Ｆｅ−Ｃｕの４元組成も含まれる。
1-3. Surface density of Mg—Si based crystallized material existing in sacrificial anode material layer The sacrificial anode material layer of the aluminum clad plate according to the present invention has a Mg—Si based crystallized material having a circle equivalent diameter of 1.0 to 10 μm. The surface density is 30000 pieces / mm 2 or less. The Mg—Si based crystallized product is basically composed of Mg and Si in an atomic number ratio of 2: 1. In this crystallized product, when the sacrificial anode material layer contains Fe or Cu as a selective additive element, in addition to Mg 2 Si, a ternary composition of Mg—Si—Fe, Mg—Si—Cu A quaternary composition of Mg-Si-Fe-Cu is also included.
粗大なＭｇ−Ｓｉ系晶出物は、腐食の集中を招き、耐食性を低下させる。この粗大なＭｇ−Ｓｉ系晶出物は、熱間押出し以降の工程では再固溶できない場合がある。そのため、熱間押出し工程までに晶出物を減少させておく必要がある。 Coarse Mg—Si-based crystallized substances cause concentration of corrosion and reduce corrosion resistance. This coarse Mg-Si crystallized product may not be re-dissolved in the steps after hot extrusion. Therefore, it is necessary to reduce the crystallized product before the hot extrusion process.
本発明者らが種々検討したところ、犠牲陽極材層中に存在する粗大Ｍｇ−Ｓｉ系晶出物の面密度を所定範囲に規定することにより、上述の犠牲防食層としての機能低下を防止できることを見出した。通常、犠牲陽極材層中に存在するＭｇ−Ｓｉ系晶出物の大きさは、円相当直径として０．１〜１０μｍであるが、犠牲防食機能を低下させる粗大なＭｇ−Ｓｉ系晶出物の大きさは、円相当直径として１．０〜１０μｍであることが判明した。円相当直径が１．０μｍ未満のＭｇ−Ｓｉ系晶出物は、犠牲防食機能を低下させるものではない。また、円相当直径が１０μｍを超えるＭｇ−Ｓｉ系晶出物は、均質化処理などの熱処理によって再固溶するため殆ど存在しない。詳細な検討の結果、このような円相当直径１．０〜１０μｍの粗大Ｍｇ−Ｓｉ系晶出物の面密度が３００００個／ｍｍ２を超えると、腐食が晶出物に集中して犠牲防食機能を大きく低下させることが判明した。なお、この面密度は小さい程好ましく、０個／ｍｍ２が最も好ましい。 As a result of various studies by the present inventors, it is possible to prevent the above-described deterioration of the function as the sacrificial anticorrosive layer by defining the surface density of the coarse Mg-Si-based crystallized material present in the sacrificial anode material layer within a predetermined range. I found. Usually, the size of the Mg—Si based crystallized substance present in the sacrificial anode material layer is 0.1 to 10 μm as the equivalent circle diameter, but a coarse Mg—Si based crystallized substance that deteriorates the sacrificial anticorrosive function. Was found to be 1.0-10 μm in terms of equivalent circle diameter. Mg-Si based crystals having an equivalent circle diameter of less than 1.0 μm do not lower the sacrificial anticorrosive function. Further, Mg—Si based crystals having an equivalent circle diameter exceeding 10 μm hardly exist because they are re-dissolved by heat treatment such as homogenization. As a result of detailed examination, when the surface density of such a coarse Mg-Si based crystallized material having an equivalent circle diameter of 1.0 to 10 μm exceeds 30000 pieces / mm 2 , corrosion concentrates on the crystallized material and sacrifice corrosion prevention It has been found that the function is greatly reduced. In addition, this surface density is so preferable that it is small, and 0 piece / mm < 2 > is the most preferable.
上記Ｍｇ−Ｓｉ系晶出物の面密度は、犠牲陽極材層の任意の部分を顕微鏡観察することによって測定される。例えば、厚さ方向に沿った断面や板材表面と平行な断面を観察するものである。簡便性の観点から、厚さ方向に沿った断面について測定するのが好ましい。なお、面密度は、複数個所の測定値の算術平均値として規定される。 The surface density of the Mg—Si-based crystallized product is measured by observing an arbitrary portion of the sacrificial anode material layer with a microscope. For example, a cross section along the thickness direction or a cross section parallel to the plate material surface is observed. From the viewpoint of simplicity, it is preferable to measure a cross section along the thickness direction. The surface density is defined as an arithmetic average value of measured values at a plurality of locations.
１−４．犠牲陽極材層中のＭｇ−Ｓｉ系析出物の体積密度
本発明に係るアルミニウム製クラッド管では、犠牲陽極材層表面から所定の深さ領域に存在する微細なＭｇ−Ｓｉ系析出物の体積密度を所定範囲に規定する。本発明者らは、本発明に係るアルミニウム製クラッド管の犠牲陽極材層がＺｎを含有しないにも拘わらず犠牲防食効果を発揮することを見出した。これは、犠牲陽極材層に、母材よりも卑な相や生成物が存在することを示唆するものである。検討の結果、顕微鏡観察では視認するのが難しい極めて微細なＭｇ−Ｓｉ系析出物が、犠牲防食効果発現の要因であることが判明した。このようなＭｇ−Ｓｉ系析出物はＴＥＭなどの顕微鏡観察では視認するのが難しいが、１７５℃で５時間の増感処理を施すことにより顕微鏡観察が容易なサイズの針状のＭｇ−Ｓｉ系析出物が観察された。このことは、元々存在する極めて微細なＭｇ−Ｓｉ系析出物が増感処理により大きく成長したものと考えられる。本発明者らの更なる検討により、上記の増感処理後において、犠牲陽極材表面から５μｍまでの深さの領域で観察される１０〜１０００ｎｍの長さを示す針状のＭｇ−Ｓｉ系析出物の体積密度と犠牲防食効果との間に相関関係があることが判明した。なお、本発明者らの分析によれば、このような微細なＭｇ−Ｓｉ系析出物の増感処理前の元々の長さは、数ｎｍ〜５０ｎｍであるものと推定される。
1-4. Volume density of Mg-Si-based precipitates in the sacrificial anode material layer In the aluminum clad tube according to the present invention, the volume density of fine Mg-Si-based precipitates existing in a predetermined depth region from the surface of the sacrificial anode material layer. Is defined within a predetermined range. The present inventors have found that the sacrificial anode material layer of the aluminum clad tube according to the present invention exhibits a sacrificial anticorrosive effect even though it does not contain Zn. This suggests that the sacrificial anode material layer has a base phase and a product that are lower than the base material. As a result of the examination, it was found that extremely fine Mg—Si-based precipitates that are difficult to visually recognize by microscopic observation are the cause of the sacrificial anticorrosive effect. Such Mg-Si-based precipitates are difficult to visually recognize with a microscope such as TEM, but a needle-like Mg-Si-based size that can be easily observed with a microscope by performing sensitization treatment at 175 ° C for 5 hours. Precipitates were observed. This is considered that the very fine Mg-Si-based precipitate that originally existed is greatly grown by the sensitization treatment. According to further studies by the present inventors, acicular Mg-Si-based precipitation having a length of 10 to 1000 nm observed in a region having a depth of 5 μm from the surface of the sacrificial anode material after the above sensitization treatment. It was found that there is a correlation between the volume density of objects and the sacrificial anticorrosive effect. According to the analysis by the present inventors, the original length of such fine Mg—Si based precipitates before the sensitization treatment is estimated to be several nm to 50 nm.
そこで、更に検討を重ねたところ、上記増感処理後において長さ１０〜１０００ｎｍの針状のＭｇ−Ｓｉ系析出物の体積密度が１０００〜５００００個／μｍ３の場合に、良好な犠牲防食効果が得られることが判明した。体積密度が１０００個／μｍ３未満では、Ｍｇ−Ｓｉ系析出物の析出量が少な過ぎるため犠牲防食効果が不十分であった。一方、体積密度が５００００個／μｍ３を超えると、Ｍｇ−Ｓｉ系析出物の析出量が多過ぎるために腐食速度が速くなり過ぎて十分な耐食寿命が得られなかった。 Accordingly, further investigations have been made, and when the volume density of the needle-like Mg—Si-based precipitates having a length of 10 to 1000 nm after the sensitization treatment is 1000 to 50000 / μm 3 , a good sacrificial anticorrosive effect is obtained. Was found to be obtained. When the volume density was less than 1000 / μm 3 , the amount of Mg—Si-based precipitates was too small, and the sacrificial anticorrosive effect was insufficient. On the other hand, when the volume density exceeds 50000 / μm 3 , the amount of Mg—Si-based precipitates is too large, so that the corrosion rate is too high and sufficient corrosion resistance life cannot be obtained.
ここで、上記増感処理後に犠牲陽極材表面から５μｍまでの深さの領域において観察されるＭｇ−Ｓｉ系析出物が１０ｎｍ未満のものについては、増感処理後においても存在を明確に確認できないために対象としなかった。一方、１０００ｎｍを超えるものについては、腐食が集中して腐食速度が増大し、耐食性が悪化することが判明した。 Here, the presence of Mg—Si-based precipitates observed in the region of a depth of 5 μm from the sacrificial anode material surface after the sensitization treatment of less than 10 nm cannot be clearly confirmed even after the sensitization treatment. Was not targeted for. On the other hand, it has been found that for those exceeding 1000 nm, corrosion concentrates, the corrosion rate increases, and the corrosion resistance deteriorates.
Ｍｇ−Ｓｉ系析出物の上記体積密度は、ＦＩＢ（Ｆｏｃｕｓｅｄ Ｉｏｎ Ｂｅａｍ）で作製した厚さ１００〜２００ｎｍ程度の試験片の１００面における５０万倍程度のＴＥＭ像を任意に複数箇所（５〜１０箇所）撮影し、表面から５μｍまでの深さの領域において１００方向に沿って３方向に析出している長さ１０〜１０００ｎｍの針状析出物の数を画像処理により測定し、測定体積で割ることで各測定箇所の密度を求めた。そして、複数個所の算術平均値をもって試料の密度分布とした。 The volume density of the Mg—Si-based precipitates can be obtained by arbitrarily setting a TEM image of about 500,000 times on a 100-side surface of a test piece having a thickness of about 100 to 200 nm manufactured by FIB (Focused Ion Beam) at multiple locations (5 to 10). The number of needle-like precipitates having a length of 10 to 1000 nm deposited in three directions along 100 directions in a region having a depth of 5 μm from the surface is measured by image processing and divided by the measurement volume. The density of each measurement location was determined. And the arithmetic average value of several places was made into the density distribution of the sample.
２．アルミニウム製クラッド管の製造方法
次に、本発明に係るアルミニウム製クラッド管の製造方法について説明する。この製造方法では、犠性陽極材層用のアルミニウム合金を半連続鋳造する半連続鋳造工程と；犠性陽極材層用の鋳塊をアルミニウム管の心材の内面及び外面の少なくとも一方に組み合わせてビレットとする組み合わせ工程と；ビレットを押出成形する押出成形工程と；を備え、半連続鋳造工程における鋳塊表面の冷却速度を１℃／秒以上とすることを特徴とする。そして、押出成形工程前にビレットを４５０〜５７０℃に加熱する加熱工程と；押出成形工程後にクラッド押出管を０．１〜１０００℃／秒の速度で冷却する冷却工程と；を更に備えることが好ましい。また、この冷却工程後に、クラッド押出管を１００〜３００℃で５〜６００分間熱処理する熱処理工程を更に備えるのが更に好ましい。
2. Next, a method for manufacturing an aluminum clad tube according to the present invention will be described. In this manufacturing method, a semi-continuous casting process in which an aluminum alloy for a sacrificial anode material layer is semi-continuously cast; and an ingot for the sacrificial anode material layer is combined with at least one of an inner surface and an outer surface of a core material of an aluminum tube to form a billet And an extrusion molding step of extruding a billet; and a cooling rate of the ingot surface in the semi-continuous casting step is 1 ° C./second or more. And a heating step of heating the billet to 450 to 570 ° C. before the extrusion molding step; and a cooling step of cooling the clad extruded tube at a rate of 0.1 to 1000 ° C./second after the extrusion molding step. preferable. Further, it is more preferable to further include a heat treatment step of heat treating the clad extruded tube at 100 to 300 ° C. for 5 to 600 minutes after the cooling step.
２−１．犠牲陽極材層用鋳塊の半連続鋳造工程における鋳塊表面の冷却速度
犠牲陽極材層用鋳塊は、半連続鋳造工程により製造される。この半連続鋳造工程において、犠性陽極材層用のアルミニウム合金の鋳塊表面の冷却速度を１℃／秒以上とする。冷却速度が１℃／秒未満の場合は、犠牲陽極材中に粗大なＭｇ−Ｓｉ系晶出物が生成し、Ｍｇ−Ｓｉ系晶出物の適切分布が得られない。冷却速度は鋳塊組織を観察し、デンドライトアームスペーシングから算出することができる（軽金属学会研委員会著 「アルミニウムとデンドライトアームスペーシングと冷却速度の測定法」）。ここで鋳塊表面とは、最表面から３０ｍｍまでの範囲を言うものとする。
2-1. Ingot surface cooling rate in the semi-continuous casting process of the sacrificial anode material layer ingot The sacrificial anode material layer ingot is manufactured by the semi-continuous casting process. In this semi-continuous casting process, the cooling rate of the ingot surface of the aluminum alloy for the sacrificial anode material layer is set to 1 ° C./second or more. When the cooling rate is less than 1 ° C./second, coarse Mg—Si based crystals are generated in the sacrificial anode material, and appropriate distribution of Mg—Si based crystals cannot be obtained. The cooling rate can be calculated from the dendrite arm spacing by observing the ingot structure ("Method of measuring aluminum and dendrite arm spacing and cooling rate" by the Institute of Light Metals, Japan). Here, the ingot surface refers to a range from the outermost surface to 30 mm.
２−２．心材
アルミニウム材の心材は、常法に従ってＤＣ鋳造法等によって鋳造される。心材の鋳塊は、必要に応じて均質化処理と面削を施してその所定の板厚とするか、或いは、熱間圧延や冷間圧延を更に施して所定の板厚とする。
2-2. Core Material The aluminum core material is cast by a DC casting method or the like according to a conventional method. The ingot of the core material is subjected to homogenization treatment and chamfering as necessary to obtain a predetermined plate thickness, or is further subjected to hot rolling or cold rolling to a predetermined plate thickness.
２−３．ろう材層
ろう材は、常法に従って連続鋳造法等によって鋳造される。ろう材の鋳塊は、必要に応じて面削、熱間圧延、冷間圧延を施して所定の板厚の圧延板とする。
2-3. Brazing material layer The brazing material is cast by a continuous casting method or the like according to a conventional method. The ingot of the brazing material is subjected to chamfering, hot rolling, and cold rolling as necessary to obtain a rolled plate having a predetermined thickness.
２−４．組み合わせ工程
２層クラッド管の場合には心材鋳塊の内面又は外面の一方に犠牲陽極材用鋳塊を配し、３層クラッド管の場合は他方に犠牲陽極材用鋳塊又はろう材用鋳塊を更に配して組み合わせてビレットとする。
2-4. Combining process In the case of a two-layer clad tube, a sacrificial anode material ingot is disposed on one of the inner surface or the outer surface of the core material ingot, and in the case of a three-layer clad tube, the other is a sacrificial anode material ingot or brazing material casting. A lump is further arranged and combined to form a billet.
２−６．押出成形工程前の加熱工程
次いで、上記ビレットを、押出成形工程前に４５０〜５７０℃に加熱される加熱工程にかけるのが好ましい。この加熱工程により、金属組織を均一にする均質化効果が得られるとともに、粗大なＭｇ−Ｓｉ系晶出物を再固溶させる。この効果を得るためには、熱処理温度が４５０℃とするのが好ましい。一方、熱処理温度が５７０℃を超えると、犠牲陽極材層が溶融するおそれがある。上記効果を得るためには、熱処理工程の保持時間は５分間以上とするのが好ましい。５分間未満では、十分な金属組織均一効果と粗大Ｍｇ−Ｓｉ系晶出物の再固溶効果が得られない場合がある。生産性や経済性の観点から、この保持時間は２０時間以下とするのが好ましい。
2-6. Heating step before the extrusion step Next, the billet is preferably subjected to a heating step heated to 450 to 570 ° C before the extrusion step. By this heating step, a homogenizing effect for making the metal structure uniform is obtained, and a coarse Mg-Si-based crystallized product is dissolved again. In order to obtain this effect, the heat treatment temperature is preferably 450 ° C. On the other hand, if the heat treatment temperature exceeds 570 ° C., the sacrificial anode material layer may be melted. In order to acquire the said effect, it is preferable that the holding time of a heat treatment process shall be 5 minutes or more. If it is less than 5 minutes, a sufficient metal structure uniform effect and a re-solution effect of coarse Mg-Si based crystals may not be obtained. From the viewpoint of productivity and economy, the holding time is preferably 20 hours or less.
２−７．押出成形工程
次いで、間接押出機によってビレットを押出してクラッド押出管を得る。押出成形には、通常の間接押出機を使用した押出成形法を用いることができる。
2-7. Next, the billet is extruded by an indirect extruder to obtain a clad extruded tube. For extrusion molding, an extrusion molding method using a normal indirect extruder can be used.
２−８．押出成形工程後の冷却工程
押出成形されたクラッド押出管を、０．１〜１０００℃／秒の速度で冷却する冷却工程にかけるのが好ましい。Ｍｇ−Ｓｉ系析出物は冷却中や室温において析出するが、冷却速度が０．１℃／秒未満ではこの析出物が粗大化する場合があり、１０００℃／秒を超えると析出が微細になり過ぎる場合がある。なお、この冷却速度は、１〜１００℃／秒が更に好ましい。
2-8. Cooling step after extrusion molding It is preferable to subject the extruded clad extruded tube to a cooling step of cooling at a rate of 0.1 to 1000 ° C / second. Mg-Si-based precipitates are deposited during cooling or at room temperature, but when the cooling rate is less than 0.1 ° C / second, this precipitate may become coarse, and when it exceeds 1000 ° C / second, the precipitate becomes fine. It may be too much. The cooling rate is more preferably 1 to 100 ° C./second.
２−９．冷却工程後の熱処理工程
上記冷却工程後に、クラッド押出管を１００〜３００℃で５分間以上熱処理する熱処理工程を更に備えるのが好ましい。この熱処理工程により、Ｍｇ−Ｓｉ系析出物の析出を促進させることができる。熱処理温度が１００℃未満の場合や熱処理時間が５分未満の場合には、Ｍｇ−Ｓｉ系析出物の析出促進効果が不十分となる場合がある。一方、熱処理温度が３００℃を超える場合には、Ｍｇ−Ｓｉ系析出物が再固溶してしまう場合がある。熱処理時間が６００分を超えることは、経済的な観点などから好ましくない。１５０〜２５０℃で１０分間以上熱処理するのが更に好ましい。
2-9. Heat treatment step after cooling step It is preferable to further comprise a heat treatment step of heat treating the clad extruded tube at 100 to 300 ° C for 5 minutes or more after the cooling step. By this heat treatment step, precipitation of Mg—Si based precipitates can be promoted. When the heat treatment temperature is less than 100 ° C. or when the heat treatment time is less than 5 minutes, the effect of promoting the precipitation of Mg—Si based precipitates may be insufficient. On the other hand, when the heat treatment temperature exceeds 300 ° C., the Mg—Si based precipitate may be re-dissolved. It is not preferable that the heat treatment time exceeds 600 minutes from the economical viewpoint. More preferably, heat treatment is performed at 150 to 250 ° C. for 10 minutes or more.
２−１０．抽伸加工工程
以上のようにして得られるクラッド押出管を、所定の外径と肉厚になるように抽伸加工にかけるのが好ましい。この抽伸加工には、生産性の高いドローブロック式連続抽伸機を使用するのが望ましい。
2-10. Drawing process It is preferable to subject the clad extruded tube obtained as described above to a drawing process so as to have a predetermined outer diameter and thickness. For this drawing process, it is desirable to use a draw block type continuous drawing machine with high productivity.
次に、本発明を実施例に基づいてさらに詳細に説明する。なお、これらの実施例は、本発明を説明するための例示に過ぎず、本発明の技術的範囲を限定するものでない。 Next, the present invention will be described in more detail based on examples. In addition, these Examples are only the illustrations for demonstrating this invention, and do not limit the technical scope of this invention.
本発明例１〜３６、４１〜４７及び比較例１〜１３、３７〜４０
犠牲陽極材層には、表１に示す組成の合金を用いた。これらの合金を表１に示す鋳塊表面冷却速度で半連続鋳造法により鋳造し面削を施した。心材には、表２に示す組成の合金を用いた。これら心材用合金を半連続鋳造法により鋳造した。心材用鋳塊は、５２０℃で６時間の均質化処理を行い、所定の厚さに面削した。なお、犠牲陽極材層用鋳塊の板厚及び面削後の心材用鋳塊の厚さは、犠牲陽極材層の片面クラッド率が１０％となるように調整した。
Invention Examples 1-36, 41-47 and Comparative Examples 1-13 , 37-40
An alloy having the composition shown in Table 1 was used for the sacrificial anode material layer. These alloys were cast by the semi-continuous casting method at the ingot surface cooling rate shown in Table 1 and faced. As the core material, an alloy having the composition shown in Table 2 was used. These core alloys were cast by a semi-continuous casting method. The ingot for the core material was homogenized at 520 ° C. for 6 hours and chamfered to a predetermined thickness. The plate thickness of the sacrificial anode material layer ingot and the thickness of the core material ingot after chamfering were adjusted so that the single-sided cladding ratio of the sacrificial anode material layer was 10%.
次に、心材用鋳塊の片面に犠牲陽極材層用鋳塊を重ねて表３、４に示すように組み合わせてビレットを作製した。表３、４に示す条件で、これらのビレットを押出成形工程前の加熱工程にかけた。次いで、加熱処理したビレットを用いて、間接押出機によって外径４７ｍｍ、肉厚３．５ｍｍのクラッド押出管を成形した。得られたクラッド押出管を、表３、４に示す条件で押出成形工程後の冷却工程にかけた。更に、冷却したクラッド押出管を表３、４に示す冷却工程後の熱処理工程にかけた。最後に、クラッド押出管をドローブロック式連続抽伸機により抽伸加工を施し、外径１０ｍｍ、肉厚０．８ｍｍ、クラッド率１０％の２層クラッド押出管試料を作製した。 Next, a billet was prepared by overlapping the ingot for sacrificial anode material layer on one side of the ingot for core material and combining them as shown in Tables 3 and 4. Under the conditions shown in Tables 3 and 4, these billets were subjected to a heating step before the extrusion molding step. Next, a clad extrusion tube having an outer diameter of 47 mm and a wall thickness of 3.5 mm was formed by an indirect extruder using the heat-treated billet. The obtained clad extruded tube was subjected to a cooling process after the extrusion molding process under the conditions shown in Tables 3 and 4. Further, the cooled clad extruded tube was subjected to a heat treatment step after the cooling step shown in Tables 3 and 4. Finally, the clad extruded tube was drawn by a draw block type continuous drawing machine to prepare a double-layer clad extruded tube sample having an outer diameter of 10 mm, a wall thickness of 0.8 mm, and a clad rate of 10%.
以上のようにして作製した２層クラッド押出管試料の特性を、以下のようにして評価した。 The characteristics of the two-layer clad extruded tube sample produced as described above were evaluated as follows.
（ａ）犠牲陽極材層中のＭｇ−Ｓｉ系晶出物の面密度
２層クラッド板試料の犠牲陽極材層からミクロ組織観察用試験片を切出し、厚さ方向の断面におけるＭｇ−Ｓｉ系の晶出物分布を測定した。ＳＥＭ（Ｓｃａｎｎｉｎｇ Ｅｌｅｃｔｒｏｎ Ｍｉｃｒｏｓｃｏｐｅ）を用い、２５００倍の組成像を観察し、５視野選択し、黒く観察されるＭｇ−Ｓｉ系の晶出物を画像処理により抽出して円相当直径１．０〜１０μｍの面密度を測定し、５視野の算術平均値を求めた。
(A) Surface density of Mg—Si based crystallized material in sacrificial anode material layer A specimen for microstructural observation was cut out from the sacrificial anode material layer of the two-layer clad plate sample, and the Mg—Si based cross section in the thickness direction was cut. The crystallized product distribution was measured. Using SEM (Scanning Electron Microscope), observe 2500 times composition image, select 5 fields of view, extract Mg-Si-based crystallized material observed in black by image processing, and equivalent circle diameter of 1.0-10 μm The surface density was measured, and the arithmetic average value of 5 fields of view was obtained.
（ｂ）犠牲陽極材層中のＭｇ−Ｓｉ系析出物の体積密度
２層クラッド板試料を、１７５℃で５時間熱処理した。次いで、犠牲陽極材表面からＦＩＢ（Ｆｏｃｕｓｅｄ Ｉｏｎ Ｂｅａｍ）で厚さ１００〜２００ｎｍ程度の試験片を作製した。試料片の表面から５μｍまでの深さの領域において、アルミニウムマトリックスの１００面に沿って３方向に析出する針状の析出物を、５０万倍の倍率で透過型電子顕微鏡（ＴＥＭ）を用いて任意に５箇所観察した。各箇所の画像中において、長さ１０〜１０００ｎｍを有する針状のＭｇ−Ｓｉ系析出物数を計測した。更に、この針状析出物と直行する点状析出物（針状のものを正面から観察するので点状に見える）のうち１００ｎｍ以下のものの数も計測し、これらを針状析出物の数と合計したものを、測定体積で割って各観察箇所におけるＭｇ−Ｓｉ系析出物の体積密度とした。最後に、各観察箇所における体積密度の算術平均値を算出して、試料におけるＭｇ−Ｓｉ系析出物の体積密度とした。ここで、点状析出物（針状のものを正面から観察するので点状に見える）の数も合計している理由は以下である。すなわち、針状のＭｇ−Ｓｉ系析出物はアルミニウムマトリックス中の１００面に沿って３方向に同様に析出しており、点状に見える析出物も直角方向から見れば長さ１０〜１０００ｎｍを満たす可能性がある。長さ１０ｎｍ未満のＭｇ−Ｓｉ系析出物は透過型電子顕微鏡（ＴＥＭ）では観察が難しく正面から見ても明確には点として認識・計測できない。長さが１０００ｎｍを超える針状のＭｇ−Ｓｉ系析出物は正面から見た場合、太さが１００ｎｍを超えるのでそれは計測から除外した。また、Ｍｇ−Ｓｉ系晶出物が点として見える場合にも直径が２００ｎｍ以上なのでそれも計測から除外した。
(B) Volume density of Mg—Si based precipitate in sacrificial anode material layer A two-layer clad plate sample was heat-treated at 175 ° C. for 5 hours. Next, a test piece having a thickness of about 100 to 200 nm was produced from the surface of the sacrificial anode material by FIB (Focused Ion Beam). Using a transmission electron microscope (TEM) at a magnification of 500,000 times, needle-like precipitates precipitated in three directions along the 100 plane of the aluminum matrix in a region having a depth of 5 μm from the surface of the sample piece. Five points were observed arbitrarily. In the image of each location, the number of acicular Mg-Si based precipitates having a length of 10 to 1000 nm was measured. Furthermore, the number of the needle-like precipitates perpendicular to the needle-like precipitates (which look like dots because the needle-like ones are observed from the front) was also counted, and these were totaled with the number of needle-like precipitates. This was divided by the measurement volume to obtain the volume density of the Mg—Si based precipitates at each observation location. Finally, the arithmetic average value of the volume density at each observation location was calculated and used as the volume density of the Mg—Si based precipitate in the sample. Here, the reason why the number of point-like precipitates (which look point-like as the needle-like object is observed from the front) is also summed up is as follows. That is, acicular Mg-Si-based precipitates are similarly deposited in three directions along the 100 plane in the aluminum matrix, and the precipitates that appear to be dot-like satisfy a length of 10 to 1000 nm when viewed from a right angle direction. there is a possibility. An Mg—Si-based precipitate having a length of less than 10 nm is difficult to observe with a transmission electron microscope (TEM) and cannot be clearly recognized and measured as a point even when viewed from the front. When the needle-like Mg-Si based precipitate having a length exceeding 1000 nm was viewed from the front, the thickness exceeded 100 nm, and thus it was excluded from the measurement. Further, even when the Mg-Si-based crystallized substance was seen as a point, the diameter was 200 nm or more, and it was excluded from the measurement.
（ｃ）ＳＷＡＡＴ試験
２層クラッド板試料を用いて、大気曝露環境を模擬したＡＳＴＭ Ｇ８５に準じたＳＷＡＡＴを１５００時間行った。ＳＷＡＡＴ試験後において、試験片の表面の腐食生成物を除去し腐食深さを測定した。測定箇所は１０箇所とし、それらの最大値をもって腐食深さとした。腐蝕深さが８０μｍ未満の場合を優良とし、８０μｍ以上の場合と貫通の場合を不良とした。
(C) SWAAT test Using a two-layer clad plate sample, SWAAT according to ASTM G85 simulating atmospheric exposure environment was performed for 1500 hours. After the SWAAT test, the corrosion product on the surface of the test piece was removed and the corrosion depth was measured. The number of measurement points was 10, and the maximum value was taken as the corrosion depth. The case where the corrosion depth was less than 80 μm was determined to be excellent, and the case where the corrosion depth was 80 μm or more and the case of penetration were determined to be poor.
（ｄ）循環サイクル試験
更なる耐食性の評価として、水系冷媒環境を模擬した循環サイクル試験を行った。Ｃｌ−：１９５ｐｐｍ、ＳＯ４ ２−：６０ｐｐｍ、Ｃｕ２＋：１ｐｐｍ、Ｆｅ２＋：３０ｐｐｍを含有し温度８８℃の水溶液を、上記熱処理した試料片の試験面に対して比液量６ｍＬ／ｃｍ２、流速２ｍ／秒で８時間流通し、その後、試料片を１６時間放置した。このような加熱流通と放置からなるサイクルを３ヶ月間行った。循環サイクル試験後において、試験片の表面の腐食生成物を除去し腐食深さを測定した。測定箇所は１０箇所とし、それらの最大値をもって腐食深さとした。腐蝕深さが７８μｍ未満の場合を優良とし、７８μｍ以上の場合と貫通の場合を不良とした。なお、心材表面にはマスキングを施し、試験水溶液に触れないようにした。
(D) Circulation cycle test As a further evaluation of corrosion resistance, a circulation cycle test simulating an aqueous refrigerant environment was conducted. An aqueous solution containing Cl − : 195 ppm, SO 4 2− : 60 ppm, Cu 2+ : 1 ppm, Fe 2+ : 30 ppm and having a temperature of 88 ° C. was measured at a specific liquid amount of 6 mL / cm 2 with respect to the test surface of the heat-treated sample piece. The sample was allowed to flow for 8 hours at a flow rate of 2 m / second, and then the sample piece was left for 16 hours. Such a cycle consisting of heating and leaving was performed for 3 months. After the circulation cycle test, corrosion products on the surface of the test piece were removed and the corrosion depth was measured. The number of measurement points was 10, and the maximum value was taken as the corrosion depth. The case where the corrosion depth was less than 78 μm was determined to be excellent, and the case where the corrosion depth was 78 μm or more and the case of penetration were determined to be poor. The core material surface was masked to avoid contact with the test aqueous solution.
以上の（ａ）〜（ｄ）の各評価結果を、表５、６に示す。 Tables 5 and 6 show the evaluation results of the above (a) to (d).
表５に示すように、本発明例１〜３６では、Ｍｇ−Ｓｉ系晶出物の面密度及びＭｇ−Ｓｉ系析出物の体積密度が規定範囲内であり、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍ未満で、犠牲陽極材層を貫通するものではなかった。 As shown in Table 5, in Examples 1-36 of the present invention, the surface density of the Mg—Si based crystallized material and the volume density of the Mg—Si based precipitate are within the specified ranges, and corrosion after SWAAAT and by the cyclic cycle test The depth was less than 80 μm and did not penetrate the sacrificial anode material layer.
比較例３７〜４０では、Ｍｇ−Ｓｉ系晶出物の面密度は規定範囲内であるが、Ｍｇ−Ｓｉ系析出物の体積密度が規定範囲外であるため、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍ程度となって、耐食性が不良であった。 In Comparative Examples 37 to 40, the surface density of the Mg—Si based crystallized material is within the specified range, but the volume density of the Mg—Si based precipitate is outside the specified range, and therefore, corrosion after SWAAAT and cyclic cycle test. The depth was about 80 μm and the corrosion resistance was poor.
本発明例４１〜４６では、押出成形後の冷却工程を経たクラッド押出管を熱処理することにより、Ｓｉ系析出物の体積密度が増大しており、ＳＷＡＡＡＴ後及び循環サイクル試験による耐食性に更に優れていた。 In Invention Examples 41 to 46, the volume density of the Si-based precipitates is increased by heat-treating the clad extrusion tube that has undergone the cooling step after extrusion, and is further excellent in corrosion resistance after SWAAAT and by the cyclic cycle test. It was.
本発明例４７では、熱処理時間が短いために、Ｓｉ系析出物の体積密度の増大効果が低く、ＳＷＡＡＡＴ後及び循環サイクル試験による耐食性は未熱処理品と同等であった。 In Invention Example 47, since the heat treatment time was short, the effect of increasing the volume density of the Si-based precipitates was low, and the corrosion resistance after SWAAAT and the cyclic cycle test was equivalent to that of the unheated product.
これに対して、表６に示すように比較例１では、犠牲陽極材層用鋳塊の半連続鋳造工程において鋳塊表面の冷却速度が遅かったため、Ｍｇ−Ｓｉ系晶出物の面密度が多かった。その結果、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍを大きく超え、犠牲陽極材層を貫通して心材の一部まで腐食した。 On the other hand, as shown in Table 6, in Comparative Example 1, the cooling rate of the ingot surface was slow in the semi-continuous casting process of the sacrificial anode material layer ingot, so the surface density of the Mg—Si-based crystallized product was low. There were many. As a result, the corrosion depth after SWAAAT and the cyclic cycle test greatly exceeded 80 μm, and the sacrificial anode material layer was penetrated to part of the core material.
比較例２では、犠牲陽極材層のＳｉ含有量が少なかったため、犠牲陽極材層の強度が不足し、クラッド管製造時に犠牲陽極材層の不均一な伸びが発生し、犠牲陽極材層のクラッド率が不均一となり、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 2, since the Si content of the sacrificial anode material layer was small, the strength of the sacrificial anode material layer was insufficient, and the sacrificial anode material layer was unevenly stretched during the manufacture of the clad tube. The rate was not uniform, and each of the evaluations (a) to (d) could not be performed.
比較例３では、犠牲陽極材層のＳｉ含有量が多かったため、押出成形工程後に犠牲陽極材層が溶融した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 3, the sacrificial anode material layer melted after the extrusion molding process because the sacrificial anode material layer had a high Si content. As a result, each of the evaluations (a) to (d) could not be performed.
比較例４では、犠牲陽極材層のＭｇ含有量が少なかったため、犠牲陽極材層の強度が不足し、クラッド管製造時に犠牲陽極材層の不均一な伸びが発生し、犠牲陽極材層のクラッド率が不均一となり、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 4, since the Mg content of the sacrificial anode material layer was small, the strength of the sacrificial anode material layer was insufficient, and the sacrificial anode material layer was unevenly stretched during the production of the clad tube. The rate was not uniform, and each of the evaluations (a) to (d) could not be performed.
比較例５では、犠牲陽極材層のＭｇ含有量が多かったため、押出成形工程において犠牲陽極材層と心材が一部接合されなかった。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 5, since the Mg content in the sacrificial anode material layer was large, the sacrificial anode material layer and the core material were not partly joined in the extrusion process. As a result, each of the evaluations (a) to (d) could not be performed.
比較例６では、犠牲陽極材層のＦｅ含有量が多かった。その結果、腐食速度が増大し、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍを大きく超え、犠牲陽極材層を貫通して心材の一部まで腐食した。 In Comparative Example 6, the sacrificial anode material layer had a high Fe content. As a result, the corrosion rate increased, the corrosion depth after SWAAAT and by the cyclic cycle test greatly exceeded 80 μm, and the sacrificial anode material layer was penetrated to part of the core material.
比較例７では、犠牲陽極材層のＣｕ含有量が多かった。その結果、腐食速度が増大し、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍを大きく超え、犠牲陽極材層を貫通して心材の一部まで腐食した。 In Comparative Example 7, the content of Cu in the sacrificial anode material layer was large. As a result, the corrosion rate increased, the corrosion depth after SWAAAT and by the cyclic cycle test greatly exceeded 80 μm, and the sacrificial anode material layer was penetrated to part of the core material.
比較例８では、犠牲陽極材層のＭｎ含有量が多かったため、鋳造時に割れが発生した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 8, since the Mn content of the sacrificial anode material layer was large, cracks occurred during casting. As a result, each of the evaluations (a) to (d) could not be performed.
比較例９では、犠牲陽極材層のＴｉ含有量が多かったため、鋳造時に割れが発生した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 9, cracks occurred during casting because the Ti content of the sacrificial anode material layer was large. As a result, each of the evaluations (a) to (d) could not be performed.
比較例１０では、犠牲陽極材層のＺｒ含有量が多かったため、鋳造時に割れが発生した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 10, since the Zr content of the sacrificial anode material layer was large, cracks occurred during casting. As a result, each of the evaluations (a) to (d) could not be performed.
比較例１１では、犠牲陽極材層のＣｒ含有量が多かったため、鋳造時に割れが発生した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 11, cracks occurred during casting because the Cr content of the sacrificial anode material layer was large. As a result, each of the evaluations (a) to (d) could not be performed.
比較例１２では、犠牲陽極材層のＮｉ含有量が多かった。その結果、腐食速度が増大し、ＳＷＡＡＡＴ後及び循環サイクル試験による腐食深さが８０μｍを大きく超え、犠牲陽極材層を貫通して心材の一部まで腐食した。 In Comparative Example 12, the Ni content of the sacrificial anode material layer was large. As a result, the corrosion rate increased, the corrosion depth after SWAAAT and by the cyclic cycle test greatly exceeded 80 μm, and the sacrificial anode material layer was penetrated to part of the core material.
比較例１３では、犠牲陽極材層のＶ含有量が多かったため、鋳造時に割れが発生した。その結果、（ａ）〜（ｄ）の各評価を行なうことができなかった。 In Comparative Example 13, cracks occurred during casting because the V content of the sacrificial anode material layer was large. As a result, each of the evaluations (a) to (d) could not be performed.
本発明により、ルームエアコンの配管、自動車用熱交換器の配管、自動車及び各種産業用機器の配管として、大気環境、塩害環境、海水環境、酸性やアルカリ性の特殊環境等においても良好な耐食性を発揮するアルミニウム製クラッド管が提供される。 According to the present invention, as a piping for room air conditioners, piping for heat exchangers for automobiles, piping for automobiles and various industrial equipment, it exhibits good corrosion resistance even in atmospheric environments, salt damage environments, seawater environments, acidic and alkaline special environments, etc. An aluminum clad tube is provided.
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| JPH06228694A (en) * | 1993-02-04 | 1994-08-16 | Furukawa Alum Co Ltd | High strength and high corrosion resistant aluminum alloy composite for heat exchanger |
| JPH1180871A (en) * | 1997-09-08 | 1999-03-26 | Sumitomo Light Metal Ind Ltd | Aluminum alloy clad material for heat exchanger, excellent in corrosion resistance |
| US20050095447A1 (en) * | 2003-10-29 | 2005-05-05 | Stephen Baumann | High-strength aluminum alloy composite and resultant product |
| JP2008266738A (en) * | 2007-04-20 | 2008-11-06 | Furukawa Sky Kk | Three-layer clad aluminum tube, and method for manufacturing internally grooved tube made of aluminum |
| JP2010095758A (en) * | 2008-10-16 | 2010-04-30 | Mitsubishi Alum Co Ltd | Brazing sheet for automotive heat exchanger for brazed tube making |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06228694A (en) * | 1993-02-04 | 1994-08-16 | Furukawa Alum Co Ltd | High strength and high corrosion resistant aluminum alloy composite for heat exchanger |
| JPH1180871A (en) * | 1997-09-08 | 1999-03-26 | Sumitomo Light Metal Ind Ltd | Aluminum alloy clad material for heat exchanger, excellent in corrosion resistance |
| US20050095447A1 (en) * | 2003-10-29 | 2005-05-05 | Stephen Baumann | High-strength aluminum alloy composite and resultant product |
| JP2008266738A (en) * | 2007-04-20 | 2008-11-06 | Furukawa Sky Kk | Three-layer clad aluminum tube, and method for manufacturing internally grooved tube made of aluminum |
| JP2010095758A (en) * | 2008-10-16 | 2010-04-30 | Mitsubishi Alum Co Ltd | Brazing sheet for automotive heat exchanger for brazed tube making |
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