EP0801141A1 - Procédé de fabrication d'une feuille en alliage d'aluminium - Google Patents

Procédé de fabrication d'une feuille en alliage d'aluminium Download PDF

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Publication number
EP0801141A1
EP0801141A1 EP97201122A EP97201122A EP0801141A1 EP 0801141 A1 EP0801141 A1 EP 0801141A1 EP 97201122 A EP97201122 A EP 97201122A EP 97201122 A EP97201122 A EP 97201122A EP 0801141 A1 EP0801141 A1 EP 0801141A1
Authority
EP
European Patent Office
Prior art keywords
sheet
alloy
amount
heat treatment
temperature
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.)
Ceased
Application number
EP97201122A
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German (de)
English (en)
Inventor
Jan Bottema
Paul Hendrikus Theodorus Kaasenbrood
Peter De Smet
Linzhong Zhuang
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.)
Alvance Aluminium Duffel BV
Original Assignee
Hoogovens Aluminium BV
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 Hoogovens Aluminium BV filed Critical Hoogovens Aluminium BV
Publication of EP0801141A1 publication Critical patent/EP0801141A1/fr
Ceased legal-status Critical Current

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    • 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
    • C22F1/05—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 of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions
    • 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
    • C22F1/043—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 of alloys with silicon as the next major constituent

Definitions

  • the invention relates to a method for the manufacture of a sheet of an AlMgSi alloy of the AA6xxx type. Such sheet is suitable for example for forming into automotive body parts.
  • Heat-treatable AlMgSi alloys of the AA6xxx type are being used increasingly for automotive body parts in which, besides good formability of the aluminium sheet, the strength after undergoing a painting cycle plays an important role.
  • the requirements imposed on the aluminium sheet used for the automotive body parts include good formability, a low and stable yield point, a high surface quality including among other things that no stretcher strains are present following shaping or deforming into a bodywork panel.
  • such aluminium sheet is produced by cold-rolling to final thickness, followed by solution heat treatment and quenching from solution heat treatment temperature so as to cool to below 150'C at a cooling rate of at least 100°C/min. Following this cooling the aluminium sheet is then aged to obtain the desired level of properties.
  • the aluminium sheet following shaping by for example pressing at room temperature, is provided with one or more paint layers. In this manner good corrosion resistance is obtained.
  • Such a paint layer is fast-cured by maintaining it for some time at an elevated temperature, for example 20-40 min at approximately 190-200°C.
  • Such a treatment is often designated by the terms 'paint-bake' or 'paint-baking'. Going through such a treatment is designated by the term 'paint-bake cycle'.
  • WO 96/07768 discloses a method for AlMgSi and AlMgSiCu alloys in which, after quenching from solution heat treatment and before any substantial age hardening has taken place, at least one subsequent heat treatment is performed by heating to a peak temperature in the range 100-300°C, preferably 130-270°C and holding this peak temperature for less than 1 minute, most preferably for 1 second or less. When one such heat treatment only is performed, the peak temperature selected is 190-300°C.
  • US-A-3 135 633 proposes an ageing process of wrought products of AlMgSi alloy in which, within 10 minutes of quenching from solution heat treatment, a preliminary ageing temperature of 100 to 250°C is reached and maintained for 1 to 10 minutes as part of a continuous process, and a final ageing is thereafter performed of for example 10 hours at 160°C.
  • the example of preliminary ageing temperature is 140°C.
  • the alloy composition is not specified.
  • An object of the present invention is to provide a method of manufacturing an aluminium sheet of the AA6xxx type which, after the paint-bake cycle according to the trend described above, has the desired properties, while the addition of copper is unnecessary.
  • Another object of the invention is to provide a method by which the aluminium sheet may be manufactured on an existing production line without too many modifications.
  • Yet another object of the invention is that the disadvantageous effect of the natural ageing on the mechanical properties after the paint-bake cycle can be reduced.
  • the method according to the invention is set out in claim 1.
  • This method achieves the effect that during a paint-bake cycle for example according to the trend described above, the aluminium sheet artificially ages adequately to allow the desired properties to be obtained at an adequate level.
  • the sheet is heated to a predetermined holding temperature in the range of 165-185°C, there is achieved the effect that the ageing response during the paint-bake cycle is optimal for the sheet of the composition specified.
  • the holding time of the aluminium sheet in this holding temperature is between 60-300 s, and more preferably is between 60-180 s. If the holding time is too long, then so-called over-ageing will occur. This makes the strength increase to an inadmissible level while the ductility decreases. If the holding time is too short, then during the paint-bake cycle there will still be an incubation time, and inadequate ageing will be likely to occur during that cycle.
  • step (iv) the aluminium sheet is held at a temperature below 50°C for a time period preferably of no more than 15 min before being heated directly to the holding temperature of steps (v) and (vi). In a continuous process, this time period may be only a few seconds.
  • the aluminium sheets of the type of this invention are sensitive to natural ageing. If the holding time during step (iv) is too long, then large Mg-Si clusters can form which essentially are responsible for the incubation time during the paint-bake cycle.
  • An advantage of the heat treatment in accordance with the invention directly following the quenching from heat treatment for improving the ageing response of the aluminium sheet during the paint-bake cycle is that it is simple to apply in existing continuous production lines for the aluminium sheet because the holding time at the holding temperature in the range 165-185°C is relatively short. It is alternatively possible to carry out the method in accordance with the invention batchwise.
  • the heat treatment of steps (v) and (vi) in the invention is the sole heat treatment between the solution heat treatment and the paint-bake following shaping of the sheet into the desired shape.
  • the sheet is cooled to room temperature and is ready for storage, transport and shaping as appropriate.
  • Considerable time may elapse before the sheet is shaped and subjected to paint-bake, without loss of the desired properties both in shaping and following the paint-bake.
  • the desired mechanical properties are obtained, and the aluminium sheet also forms well, has good corrosion resistance, good paintability, good weldability especially for spot welding and a good surface quality.
  • the aluminium sheet used in the invention has the composition in weight percent as follows: 0.4-1.7 Si, 0.2-0.9 Mg, 0.25 Mn (maximum) , 0.2 Cu (maximum), 0.5 Fe (maximum), the balance essentially aluminium and unavoidable impurities.
  • the Si content is 0.8-1.5 wt%. This achieves the effect of improving the mechanical properties. More preferably the Si content is 1.0-1.3 wt%. This achieves the effect of optimizing the mechanical properties and formability for application of the aluminium sheet in automotive body parts.
  • the Mg content is preferably 0.2-0.6 wt%. Cooperation with the Si allows Mg-Si clusters or precipitates to form which contribute to the mechanical properties of the aluminium sheet. More preferably the Mg content is 0.25-0.45 wt% because an optimum formability is achieved when the Si/Mg ratio is approximately 3.
  • the Mn content is preferably 0.05-0.20 wt%.
  • the ductility reduces to an unacceptable level as the Mn content increases.
  • the Mn content is too low, for example lower than 0.05%, the Mn may not contribute sufficiently to an effective grain refinement during the solution heat treatment as a consequence of the formation of too few so-called dispersoids.
  • the optimum combination for the desired contribution to the grain refinement effect following solution heat treatment and the decreasing elongation as the Mn content increases is obtained at 0.05-0.20 wt% Mn.
  • dispersoid-forming alloying elements other than Mn can also be used for this purpose, such as for example Cr or Zr. If Cr or Zr is added at 0.05-0.25 wt%, then virtually identical results are achieved in respect of grain size following solution heat treatment as with Mn in that range. This is because the formed dispersoids are of the same order of size as when Mn is added, which is a consequence of the interaction of Zr or Cr with the Si and Mg. Adding Zr or Cr to an AA6xxx type alloy produces a significant improvement with respect to the grain size, but the costs for alloys containing Zr or Cr will be higher than if Mn is added in the same range. Moreover the value and usefulness of scrap material containing Zr or Cr is low. For this reason Zr or Cr is preferably not present to the aluminium sheet used in the invention other than any which is coincidentally or unavoidably present in the recycled scrap being used.
  • the Fe content has a great influence on the formability of the aluminium sheet. With a high Fe content, for example over 0.5 wt%, relatively large intermetallic compounds form which greatly reduce the formability. A low Fe content is therefore desirable.
  • the Fe present also contributes to the control of the grain size in the sheet during solution heat treatment.
  • the intermetallic compounds containing iron can favourably affect the nucleation process during solution heat treatment so that a small grain size occurs.
  • Good results are achieved in the aluminium sheet in accordance with the invention with an Fe content not more than 0.3 wt%. More preferably the Fe content is 0.15-0.30 wt%. In this range the best compromise is obtained between a good formability and the favourable contribution to the grain size during solution heat treatment.
  • the alloying element Cu can make a considerable contribution to the increase in the mechanical properties of the aluminium sheet. It may be generally known that as Cu content in the aluminium sheet increases, the corrosion resistance greatly decreases. Bearing in mind the applications of the aluminium sheet in for example automotive body parts, good corrosion resistance is especially important. Therefore the Cu content in the aluminium sheet in this invention should generally be low. For an optimum corrosion resistance the Cu content must preferably be lower than 0.1 wt%. Cu therefore preferably is deliberately not added to the alloy and is not present other than that coincidentally or unavoidably present in recycled scrap being used.
  • the invention also consists in a sheet, e.g. one suitable for application in automotive body part manufacture, made in accordance with the invention.
  • the invention further consists in such a sheet which is in shaped non-planar form and is optionally painted by a paint-bake process.
  • the heat treatments IV and V were both performed within 30 minutes of the quenching from solution heat treatment temperature, and were followed by cooling again to room temperature.
  • Fig. 2 which specifies the time [min] and temperature [°C] of the paint-bake cycles.
  • the heat treatment V in the range in accordance with the invention contributes to a higher strength following subjection to a paint-bake cycle. It can also be seen that natural ageing prior to the heat treatment in accordance with the invention results in lower strength following subjection to the paint-bake cycle. It can further be seen that the duration and the temperature of the paint-bake cycle has a great influence on the final strength of the aluminium sheet. In particular good results are obtained with the heat treatment V in accordance with the invention in the case of the relatively short duration and low temperature of the paint-bake cycle. A holding time shorter than 1 min in a temperature range of 165-185°C is inadequate for obtaining sufficient strength following the paint-bake cycle.
  • the short duration heat treatment of the invention is economical and is easily carried out in a continuous production line.
  • Specimens suitable for mechanical testing in a laboratory were taken from cold-rolled coils and were solution heat treated at 570°C for 10 sec and then quenched in water. Then the specimens were naturally aged for 12 days and tested at room temperature. Aluminium sheets comprising the alloying elements as set out in Table 1 below were tested.
  • the sheets containing 0% of the alloying elements Mn, Zr or Cr are identical to sheet 2 of Table 1.
EP97201122A 1996-04-15 1997-04-15 Procédé de fabrication d'une feuille en alliage d'aluminium Ceased EP0801141A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1002861A NL1002861C2 (nl) 1996-04-15 1996-04-15 Werkwijze voor het vervaardigen van een goed vervormbare aluminiumplaat.
NL1002861 1996-04-15

Publications (1)

Publication Number Publication Date
EP0801141A1 true EP0801141A1 (fr) 1997-10-15

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EP97201122A Ceased EP0801141A1 (fr) 1996-04-15 1997-04-15 Procédé de fabrication d'une feuille en alliage d'aluminium

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EP (1) EP0801141A1 (fr)
NL (1) NL1002861C2 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1195449A2 (fr) * 2000-09-14 2002-04-10 Aluminium Ranshofen Walzwerk Gesellschaft mbH Durcissement par précipitation d'un alliage d'aluminium
FR2835533A1 (fr) * 2002-02-05 2003-08-08 Pechiney Rhenalu TOLE EN ALLIAGE Al-Si-Mg POUR PEAU DE CARROSSERIE AUTOMOBILE
FR2841568A1 (fr) * 2002-07-01 2004-01-02 Corus Aluminium Nv TOLE D'ALLIAGE AlMgSi
US7491278B2 (en) * 2004-10-05 2009-02-17 Aleris Aluminum Koblenz Gmbh Method of heat treating an aluminium alloy member and apparatus therefor
WO2010112698A1 (fr) * 2009-04-03 2010-10-07 Alcan International Limited Alliage d'aluminium de décolletage de la série aa 6xxx

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3135633A (en) * 1959-09-08 1964-06-02 Duralumin Heat treatment process improving the mechanical properties of aluminiummagnesium-silicon alloys
JPH02209457A (ja) * 1989-02-09 1990-08-20 Kobe Steel Ltd 再加熱装置を組込んだ連続焼鈍炉
JPH0544000A (ja) * 1991-08-12 1993-02-23 Mitsubishi Alum Co Ltd 溶体化焼入れ処理したのち放置されて自然時効硬化したアルミニウム合金板の復元処理方法
JPH05279822A (ja) * 1992-04-01 1993-10-26 Sumitomo Light Metal Ind Ltd 塗装焼付硬化性、成形性、形状凍結性に優れた成形加工用アルミニウム合金材の製造法
WO1996007768A1 (fr) * 1994-09-06 1996-03-14 Alcan International Limited Procede de traitement thermique destine a une feuille d'alliage d'aluminium

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3135633A (en) * 1959-09-08 1964-06-02 Duralumin Heat treatment process improving the mechanical properties of aluminiummagnesium-silicon alloys
JPH02209457A (ja) * 1989-02-09 1990-08-20 Kobe Steel Ltd 再加熱装置を組込んだ連続焼鈍炉
JPH0544000A (ja) * 1991-08-12 1993-02-23 Mitsubishi Alum Co Ltd 溶体化焼入れ処理したのち放置されて自然時効硬化したアルミニウム合金板の復元処理方法
JPH05279822A (ja) * 1992-04-01 1993-10-26 Sumitomo Light Metal Ind Ltd 塗装焼付硬化性、成形性、形状凍結性に優れた成形加工用アルミニウム合金材の製造法
WO1996007768A1 (fr) * 1994-09-06 1996-03-14 Alcan International Limited Procede de traitement thermique destine a une feuille d'alliage d'aluminium

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 014, no. 505 (C - 0775) 5 November 1990 (1990-11-05) *
PATENT ABSTRACTS OF JAPAN vol. 017, no. 345 (C - 1077) 30 June 1993 (1993-06-30) *
PATENT ABSTRACTS OF JAPAN vol. 018, no. 068 (C - 1161) 4 February 1994 (1994-02-04) *
W.HUFNAGEL: "ALUMINIM-SCHLÜSSEL", 1983, ALUMINIUM VERLAG, DÜSSELDORF, DE, XP002038066 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1195449A2 (fr) * 2000-09-14 2002-04-10 Aluminium Ranshofen Walzwerk Gesellschaft mbH Durcissement par précipitation d'un alliage d'aluminium
EP1195449A3 (fr) * 2000-09-14 2003-12-17 Aluminium Ranshofen Walzwerk Gesellschaft mbH Durcissement par précipitation d'un alliage d'aluminium
FR2835533A1 (fr) * 2002-02-05 2003-08-08 Pechiney Rhenalu TOLE EN ALLIAGE Al-Si-Mg POUR PEAU DE CARROSSERIE AUTOMOBILE
WO2003066919A2 (fr) * 2002-02-05 2003-08-14 Pechiney Rhenalu Tole en alliage al-si-mg pour peau de carrosserie automobile
WO2003066919A3 (fr) * 2002-02-05 2004-04-08 Pechiney Rhenalu Tole en alliage al-si-mg pour peau de carrosserie automobile
FR2841568A1 (fr) * 2002-07-01 2004-01-02 Corus Aluminium Nv TOLE D'ALLIAGE AlMgSi
US7491278B2 (en) * 2004-10-05 2009-02-17 Aleris Aluminum Koblenz Gmbh Method of heat treating an aluminium alloy member and apparatus therefor
WO2010112698A1 (fr) * 2009-04-03 2010-10-07 Alcan International Limited Alliage d'aluminium de décolletage de la série aa 6xxx
FR2944029A1 (fr) * 2009-04-03 2010-10-08 Alcan Int Ltd Alliage d'aluminium de decolletage de la serie aa 6xxx

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Publication number Publication date
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