EP1370702A1 - Alliage d'aluminium coule par refroidissement intense et direct (dc) - Google Patents

Alliage d'aluminium coule par refroidissement intense et direct (dc)

Info

Publication number
EP1370702A1
EP1370702A1 EP02706958A EP02706958A EP1370702A1 EP 1370702 A1 EP1370702 A1 EP 1370702A1 EP 02706958 A EP02706958 A EP 02706958A EP 02706958 A EP02706958 A EP 02706958A EP 1370702 A1 EP1370702 A1 EP 1370702A1
Authority
EP
European Patent Office
Prior art keywords
alloy
heating
present
interannealing
ingot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02706958A
Other languages
German (de)
English (en)
Inventor
Alan Gray
Andrew David Howells
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rio Tinto Alcan International Ltd
Original Assignee
Alcan International Ltd Canada
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcan International Ltd Canada filed Critical Alcan International Ltd Canada
Publication of EP1370702A1 publication Critical patent/EP1370702A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon

Definitions

  • This invention relates to an aluminium alloy, particularly one which has been DC cast and is used for finstock in heat exchangers.
  • the automotive heat exchanger market requires finstock alloys that offer, at low cost, a balance of physical and chemical properties, i.e. strength, formability, sag resistance, corrosion resistance, thermal conductivity and brazeability.
  • Aluminium alloy heat exchangers provided with header plates, tank units, tubes for coolant (water based) and fins for improved heat exchange, are very widely used in the automobile industry and elsewhere.
  • the fins are joined to the tubes by brazing.
  • WO-A-00/05426 discloses a high conductivity aluminium fin alloy.
  • the invention disclosed therein relates to continuous strip casting of an AI alloy, where the finstock has a conductivity after brazing of greater than 49.0% IACS. During continuous casting a thin strip is produced which cools quickly.
  • Al-Fe-Si alloys are disclosed in, for example, the following documents: GB 1524355, GB 1524354, WO-A-00/05426, JP-A-2000169926, JP-A- 080218143, JP-A-060145861, JP-A-040154931, JP-A-010195257.
  • the compositions of the alloys exemplified in these documents varies, but there is no disclosure of DC cast alloys.
  • the alloy could, for example, be used in header plate, or side support applications, and may have other uses, but it is primarily intended as a finstock alloy for heat exchangers.
  • Cu is present in the range 0.05 - 0.2, even more preferably 0.1 - 0.15.
  • Cu is included as a solid solution strengthening component.
  • Mg is preferably present as a strengthening component. At high concentrations, an undesired MgO deposit is formed on the metal surface during brazing. The Mg concentration is controlled at levels where this is not a problem. Higher levels of Mg will, in the presence of K 3 AIF 6 and KAIF 4 flux mixtures, lead to the formation of high melting point aluminium fluorides which have a deleterious effect on clad fluidity.
  • Mg is present in the range 0.05 - 0.2, even more preferably 0.1 - 0.15.
  • Fe is preferably present in the range 0.8 - 1.4, although an even more preferred upper limit of the range is 1.35. Higher levels cause the formation of excessively large intermetallic particles.
  • Si above the upper limit of 0.95% reduces the solidus of the alloy to below 610°C which is unacceptable as it is too close to the brazing temperature.
  • the lower limit is determined by the amount of Si necessary to achieve the required post braze strength.
  • Mn if present in amounts more than 0.5% has a deleterious effect on the thermal conductivity. Below 0.2%Mn there is insufficient strengthening effect.
  • Zn is added to make the finstock more electro-negative than, and sacrificial to, the tube material of the heat exchanger. Above 0.8%Zn, the fin becomes too electro-negative. Such high levels of Zn are detrimental to the thermal conductivity of the fin. Below 0.2%Zn, the fin is not sufficiently electro-negative to be sacrificial. The preferred range is 0.5 to 0.7%Zn.
  • a DC cast aluminium alloy finstock having a composition (in wt%):
  • the finstock sheet may be clad with a layer of aluminium alloy that is rich in silicon. Suitable alloys are AA4343 and AA4045 although other silicon rich alloys may be used.
  • the silicon rich layer may optionally contain additions such as Zn or Sn or In that render the fin more electronegative.
  • This finstock may have the above-mentioned preferable or optional features.
  • the finstock has a conductivity after brazing of at least 45% IACS.
  • aluminium alloys of this invention are DC cast, and the reasons for this are described in further detail below.
  • brazed heat exchanger having fins of the above- mentioned alloy.
  • AI balance which method comprises DC casting the alloy to form an ingot.
  • the present invention is therefore aimed at producing the ingot by conventional DC casting, thereby avoiding the need for continuous casting (for example belt casting or twin roll casting).
  • DC casting produces a thick ingot that cools slowly during solidification.
  • Continuous casting produces a thin, 3 - 20mm strip that cools quickly.
  • the difference in cooling rate has a profound effect on the metallurgical structure of the cast product. These differences remain even after processing the ingot down to very thin gauge foil.
  • the process of the present invention produces a material that has properties comparable to those of continuous cast material.
  • the control of the particle size of the DC cast material is important in obtaining these properties.
  • the cooling rate is approximately 1 - 5°C per second depending on the ingot thickness.
  • Finstock derived from the alloy should have high thermal conductivity after brazing (which typically occurs at 595°C to 605°C for times of about 2 - 10 minutes) combined with good strength (UTS) and corrosion potential.
  • the thermal conductivity is usually implied by measuring the electrical conductivity. Both are reduced by elements in solution so there is a need to reduce the amount of soluble elements going into solution during brazing. This is achieved by controlling the particle size of the intermetallics and the dispersoids in the rolled sheet and the chemical composition of the sheet.
  • the high strength achieved by the DC cast material allows downgauging, to below 100 ⁇ m, for example below 75 ⁇ m, thus providing the ability to achieve new and improved lightweight fins. Additionally, the composition of the alloy has been chosen to maximise the absorption of brazing sheet scrap to ensure a low-cost production route, and maximise recyclability.
  • the method further comprises the steps of heating or homogenising the DC cast ingot, hot rolling, cold rolling, and (inter)annealing, and may further comprise the step of cold rolling after the interannealing step.
  • the final thickness reduction during cold rolling is preferably between 25 and 45%.
  • the homogenising step may be a two-stage homogenisation comprising heating the ingot to 580 - 620°C, holding for up to 8 hours, cooling to 460 - 500°C and holding for up to 8 hours.
  • the heating step may be a simple heat to roll step comprising heating to 460 - 540°C, and holding for up to 8 hours.
  • This simple heat to roll step is not sufficient to bring about complete homogenisation of the ingot. It is intended to bring the ingot to a uniform temperature to facilitate hot rolling.
  • the hot rolling is preferably performed to 2.5 to 5.0mm, with an exit temperature from the hot mill of typically 280 - 360°C. Where an interannealing step is present, subsequent cold rolling to 50 - 700 ⁇ m is preferred. Cold rolling to final gauge without an intermediate anneal is followed by a final anneal.
  • the (inter)annealing step may be a single stage process at 250 - 450°C, preferably holding at this temperature for 2 to 4 hours. Alternatively, it may be a two-stage process comprising heating at 300 - 500°C (preferably holding for up to 4 hours) and subsequently cooling to 200 - 350°C (preferably holding for up to 4 hours).
  • annealing may be carried out in a continuous annealing furnace with the strip being fed through as a single strand to greatly increase the heating rates and reduce the holding times required. Higher annealing temperatures and shorter annealing times may thus be achieved.
  • the method may further comprise the step of brazing, wherein the particle size of the intermetallics and/or dispersoids present in the rolled product is sufficiently large such that the reduction in IACS is less than 5% units during brazing.
  • dispersoids dissolve readily and increase the solute level. Rapid cooling after brazing retains substantially all of the solute in solution and this reduces the IACS value and the thermal conductivity.
  • Increasing the mean dispersoid size reduces the amount dissolved during the brazing cycle and hence reduces the reduction in IACS and thermal conductivity.
  • Dispersoid size is increased by using special homogenising and/or annealing treatments that coarsen the alpha AI(Fe, Mn)Si dispersoids and probably also coarsen some of the intermetallic particles.
  • the homogenising treatment preferably comprises consecutive treatments at two temperatures, a first high temperature treatment followed by a lower temperature treatment. Annealing treatments may follow the same pattern.
  • the dispersoids present in the sheet generally have a mean size substantially below one micron (as determined by the mean linear intercept method).
  • the special homogenising and annealing treatments increase the mean dispersoids size, for example to greater than 0.5 microns preferably greater than 1 ⁇ m and ideally greater than 2 ⁇ m but less than 10 ⁇ m. Thermodynamic calculations reveal that these particles are unlikely to transform during the brazing cycle.
  • the intermetallic particles (containing Fe Mn and Si together with other elements) are substantially larger than the dispersoids; their size is determined during solidification and possible break up during rolling.
  • an aluminium alloy finstock from an alloy comprising (in wt%):
  • AI balance which method comprises DC casting the alloy, heating or homogenising, hot rolling, cold rolling, and annealing or interannealing.
  • FIG. 1 is a flow diagram showing various processes of the present invention
  • Figure 2 is a graph showing post-brazed strength trends
  • Figure 3 is a graph showing corrosion potential trends (the left hand column of each pair relates to interannealed, and the right hand column relates to back annealed, i.e. annealed after cold rolling to final gauge);
  • Figure 4 is a graph showing post-brazed mechanical properties
  • Figure 5 is a graph showing corrosion potentials
  • Figure 6 is a graph showing the relationship between post-brazed UTS and grain size.
  • One ingot (route 1 , Figure 1 ) was heated to 520°C and held for about 4 hrs before hot rolling to 3.0mm, with an exit temperature of approximately 325°C.
  • the coil was then cold rolled to a transfer gauge of 400 ⁇ m and then cold rolled to a gauge of 95 ⁇ m, interannealed at 270°C for 2 hours at temperature, and further cold rolled to a final gauge of 63 ⁇ m (final reduction of about 34%).
  • Post-brazed strength trends are shown in Figure 2 - interannealed route.
  • Corrosion potential trends are shown in Figure 3 - interannealed route.
  • material at transfer gauge was cold rolled directly to 63 ⁇ m and given a partial anneal (back anneal) at temperatures between 200 and 400°C.
  • Conductivity is about 45% IACS.
  • Interanneal gauge is varied to maximise post-brazed grain size which benefits sag resistance during the braze cycle. For example, the thicker the interanneal gauge the smaller the grain size after brazing. Furthermore, the aspect ratio of the grains (length in the cold working direction to the thickness direction) increases as the interanneal gauge is reduced.
  • Example 2 Material produced according to the composition noted in Example 1 was taken and heated to 460°C and held for approximately 4 hours before hot rolling to 3.0mm gauge. The coil was then cold rolled to a transfer gauge of 400 ⁇ m and subsequently cold rolled and interannealed at 360°C, to a final gauge of 63 ⁇ m. The final pass reductions were in the range 45 to 25%.
  • Figure 6 shows the relationship between post-brazed UTS and grain size.
  • the average grain size needs to be less than 50 ⁇ m. However, reducing the post-brazed grain size does reduce the sag resistance of the material.
  • a balance between post-brazed grain size, UTS and sag resistance can be achieved by selecting specific combinations of:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Continuous Casting (AREA)

Abstract

L'invention concerne un alliage coulé par DC de composition (en % en pds): Fe 0,8 à 1,5 ; Si 0,7 à 0,95 ; Mn 0,2 à 0,5 ; Zn 0,2 à 0,8 ; Mg jusqu'à 0,2 ; Cu jusqu'à 0,2 ; Ti ∫0,1 ; B ∫0,01 ; C ∫0,01 ; impuretés inévitables jusqu'à 0,05 chacun ; 0,15 au total, le reste étant constitué d'Al. L'invention concerne un procédé de coulage de l'alliage par DC permettant de former un lingot.
EP02706958A 2001-03-22 2002-03-18 Alliage d'aluminium coule par refroidissement intense et direct (dc) Withdrawn EP1370702A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0107208 2001-03-22
GBGB0107208.1A GB0107208D0 (en) 2001-03-22 2001-03-22 "Al Alloy"
PCT/GB2002/001275 WO2002077307A1 (fr) 2001-03-22 2002-03-18 Alliage d'aluminium coule par refroidissement intense et direct (dc)

Publications (1)

Publication Number Publication Date
EP1370702A1 true EP1370702A1 (fr) 2003-12-17

Family

ID=9911337

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02706958A Withdrawn EP1370702A1 (fr) 2001-03-22 2002-03-18 Alliage d'aluminium coule par refroidissement intense et direct (dc)

Country Status (6)

Country Link
US (1) US20040182482A1 (fr)
EP (1) EP1370702A1 (fr)
JP (1) JP2004523657A (fr)
CA (1) CA2440691A1 (fr)
GB (1) GB0107208D0 (fr)
WO (1) WO2002077307A1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004094679A1 (fr) * 2003-04-24 2004-11-04 Alcan International Limited Alliages a base de dechets d'aluminium recycles a haute teneur en fer et en silicium
JP4702797B2 (ja) * 2006-02-20 2011-06-15 住友軽金属工業株式会社 犠牲陽極材面のろう付けによる面接合性に優れたアルミニウム合金クラッド材の製造方法
WO2008058708A1 (fr) * 2006-11-14 2008-05-22 Aleris Aluminum Duffel Bvba Alliage d'aluminium résistant au fluage pour tubes multicouches
CN101660883B (zh) * 2009-09-04 2011-10-26 东莞市奥达铝业有限公司 一种汽车铝合金散热片的生产方法
KR102033820B1 (ko) 2011-12-16 2019-10-17 노벨리스 인코퍼레이티드 알루미늄 핀 합금 및 그 제조 방법
JP6154225B2 (ja) * 2013-07-05 2017-06-28 株式会社Uacj 熱交換器用アルミニウム合金フィン材およびその製造方法
JP6154224B2 (ja) * 2013-07-05 2017-06-28 株式会社Uacj 熱交換器用アルミニウム合金フィン材およびその製造方法
JP6751713B2 (ja) 2014-08-06 2020-09-09 ノベリス・インコーポレイテッドＮｏｖｅｌｉｓ Ｉｎｃ． 熱交換器フィンのためのアルミニウム合金
CN114606414B (zh) * 2022-03-11 2022-12-02 北京理工大学 一种高导电率再生铝合金导线及其制备方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AR206656A1 (es) * 1974-11-15 1976-08-06 Alcan Res & Dev Metodo para producir un producto en hoja de aleacion de aluminio a partir de una aleacion de al-fe
US6592688B2 (en) * 1998-07-23 2003-07-15 Alcan International Limited High conductivity aluminum fin alloy
US6165291A (en) * 1998-07-23 2000-12-26 Alcan International Limited Process of producing aluminum fin alloy

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO02077307A1 *

Also Published As

Publication number Publication date
WO2002077307A1 (fr) 2002-10-03
CA2440691A1 (fr) 2002-10-03
GB0107208D0 (en) 2001-05-16
US20040182482A1 (en) 2004-09-23
JP2004523657A (ja) 2004-08-05

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