MXPA06013571A

MXPA06013571A - Process for producing an aluminium alloy brazing sheet, aluminium alloy brazing sheet.

Info

Publication number: MXPA06013571A
Application number: MXPA06013571A
Authority: MX
Inventors: Job Anthonius Van Der Hoeven; Achim Burger; Klaus Vieregge; Scott William Haller; Sampath Desikan
Original assignee: Corus Aluminium Walzprod Gmbh
Priority date: 2004-05-26
Filing date: 2005-05-25
Publication date: 2007-03-15
Also published as: CN1973056A; CA2565978A1; EP1753885B2; EP1753885B1; KR101216246B1; EP1753885A1; JP5326123B2; KR20070058383A; HUE032303T2; CN1973056B; CA2565978C; WO2005118899A1; JP2008500453A

Abstract

The invention relates to a process for producing an Al-Mn alloy sheet with improved liquid film migration resistance when used as core alloy in brazing sheet, comprising the steps of: casting an ingot having a composition comprising (in weight percent): 0.5 < Mn <= 1.7 0.06<Cu<=1.5 Si <= 1.3 Mg <= 0.25 Ti < 0.2 Zn <= 2.0 Fe <= 0.5 at least one element of the group of elements consisting of 0.05 < Zr <=0.25 and 0.05 < Cr<=0.25 other elements < 0.05 each and total <0.20, balance Al. homogenisation and preheat hot rolling bull cold rolling (including intermediate anneals whenever required), and wherein the homogenisation temperature is at least 450 degree C for a duration of at least 1 hour followed by an air cooling at a rate of at least 20 degree C/h and wherein the pre-heat temperature is at least 400 degree C for at least 0.5 hour.

Description

PROCEDURE FOR PRODUCING A ALUMINUM ALLOY COIL WELDING PLATE AND ALLOY COIL WELDING PLATE OF ALUMINUM DESCRIPTION OF THE INVENTION The invention relates to a process for producing an Al-Mn alloy sheet with improved resistance to migration of liquid film when it is used as a core alloy in brazing sheet materials. The invention is further related to an Al-Mn alloy sheet produced according to said process and to the use of said alloy sheet. In brazing applications, the phenomenon known as "liquid film migration" or "LFM" causes a deterioration in the overall performance of brazed products such as evaporators, radiators, heater cores, and so on. In the literature, the term "LFM" is also referred to as "core dissolution" or "core penetration" or "core erosion". In the present, the term "LFM" will refer to all these terminologies. Although the exact mechanism causing LFM is not fully understood, it appears that the LFM gravity is increased by the presence of a number of dislocations in the core alloy of the brazed sheet. It is known that the sensitivity of a material to LFM is relatively low in fully annealed anneals (tempered O) and hardened by elongation or attenuated tension (such as for example H14, H24, etc.) compared to the mild condition and slightly worked on. cold of the same material. By the term "cold light work" we want to refer to the deformation resulting from the industrial process such as stamping, formed by rolling or tension leveling which are typically applied to produce heat exchanger components such as evaporator core plates or oil cooler, bent pipes, and so on. When a brazed sheet consisting of a core alloy and an Al-Si-plated alloy is deformed to form a product and subsequently subjected to a brazing cycle, the small amount of deformation appears to be sufficient to induce LFM in the brazed sheet . If the LFM progresses too much in the core alloy, then the susceptibility to brazing, toughness and corrosion resistance decreases. It is known that alloy elements which retard recrystallization such as chromium, zirconium and vanadium improve the susceptibility to LFM. It is also known that manganese dispersoids retard recrystallization and thus improve susceptibility to LFM. The amount and size of the manganese dispersoids depends on the processing path of the brazing sheet. For brazing applications, a core alloy of a brazing sheet product requires a good combination of toughness and formability. Evidently, the susceptibility to LFM needs to be at a sufficiently low level to ensure resistance to corrosion and susceptibility to 10 suitable brazing. Greater tenacity can be obtained by alloying with elements such as silicon, manganese, chromium, zirconium or vanadium. However, these alloying elements also increase the susceptibility to LFM. The use of a different tempering of 1J1 O, such as an H14 tempering or an H24 tempering have also been suggested to reduce susceptibility to LFM. However, although these temperings reduce effectively LFM, the conformability of the brazed sheet product is often compromised. Other procedures Alternative methods such as the light cold deformation process, such as tension leveling or the use of a non-recrystallized surface layer are difficult to control in mass production practice and therefore may compromise reproducibility or 25 conformability.

An object of the invention is to provide a process for producing an Al-Mn alloy sheet with improved resistance to liquid film migration when used as a core alloy in brazing sheet, where a good combination of tenacity / formability is combined with a sufficiently low susceptibility to LFM and an adequate corrosion resistance. An object is also to provide a process for producing an Al-Mn alloy sheet which is easy to control and which results in a reproducible product. An object is also to provide an Al-Mn alloy sheet with improved resistance to migration of liquid film in folded tubes, evaporator or oil cooler core plates, fin loads, etc., where a good combination of toughness / The formability of the alloy is combined with a sufficiently low susceptibility to LFM, a good susceptibility to brazing and an adequate resistance to corrosion. According to the invention, one or more of the objectives is achieved with a process for producing an Al-Mn alloy sheet with improved resistance to migration of liquid film when it is used as a core alloy in brazing sheet, comprising the stages of: • Melting a composition comprising (in% by weight): ° 0.5 <; Mn < 1.7, preferably 0.6 - 1.7, • 0.06 < Cu < 1.5, preferably 0.2 to 1.5, ° If < 1.3, preferably Si < 0.8, more preferably Si < 0.3, ° Mg < 0.25 • Ti < 0.2 ° Zn < 2.0 ° Fe < 0.5 ° at least one element of the group consisting of 0.05 < Zr < 0.25 and 0.05 < Cr < 0.25 ° other elements < 0.05 each, and a total of < 0.20, the rest of Al. • homogeinization and preheating • hot rolling • cold rolling (which includes intermediate annealing, whenever required) where the homogenization temperature is at least 450 ° C for a duration of less than 1 hour followed by cooling to air, at a rate of at least 20 ° C / h and where the preheat temperature is at least 400 ° C for at least 0.5 hours.

The casting is carried out using regular production techniques such as DC casting or continuous casting. The process according to the invention allows the production of an alloy of Al-Mn, which, when used as a core alloy in brazing sheets, combines a good combination of toughness / formability with a sufficiently low susceptibility to LFM and a resistance to proper corrosion. The inventors surprisingly found that, although chromium has been reported to have a detrimental effect on the susceptibility to LFM due to the retarding effect it has on the recrystallization of the alloy, the combination of the chemistry of the alloy and the process parameters, particularly the homogenization and preheating process result in a product with a sufficiently low susceptibility to LFM and therefore an adequate corrosion resistance. Precipitates containing Cr and or containing Zr, or both, which are formed in the alloy as a result of the combination of composition and processing conditions, reduce the susceptibility to LFM. In addition, the chromium becomes more resistant to the alloy while the recrystallization of the alloy results in an adequate formability. The inventors have found that similar results can be obtained by alloying with V or alloying with a combination of V with Cr or Zr. In one embodiment of the invention, the Cr or Zr content is at least 0.08%. The inventors found that when using a chromium content of at least 0.08% or a zirconium content of at least 0.08% or the combination thereof together with the described process conditions results in superior toughness in combination with the adequate resistance to LFM. In one embodiment of the invention, the maximum magnesium content is 0.1%, preferably the maximum magnesium content is 0.05%. The magnesium content should be as low as possible to avoid the damaging effect of magnesium on the flux used during brazing in a controlled atmosphere. In one embodiment of the invention, the copper content is from 0.7 to 1.2%. In one embodiment of the invention, the manganese content is from 0.7 to 1.4%. If the manganese content exceeds 1.4% the manufacturing difficulties are increased, and below the alloy toughness is below 0.7%. In one embodiment of the invention, the maximum zinc content is preferably 0.4% to prevent the core alloy from being excessively anodic in certain applications. In one embodiment of the invention, the iron content is preferably less than 0.35% to avoid the formation of intermetallic compounds containing undesirable large iron during industrial casting practice. In one embodiment of the invention, the homogenization temperature is between about 530 ° C and 620 ° C, preferably between 530 and 595 ° C, preferably between 1 and 25 hours, more preferably 10 between 10 and 16 hours, and wherein the preheating temperature is between about 400 ° C and 530 ° C, preferably between 420 and 510 ° C, preferably between 1 to 25 hours, most preferably between 1 and 25 hours. and 10 hours. In the alloys according to the invention, it seems that the best balance between toughness, formability, susceptibility to LFM and corrosion resistance is found when the temperature and time of homogenization as well as the temperature and time of preheating are selected within given limits Y A particularly interesting balance is obtained when processing the alloy according to the above-mentioned preferred temperatures and times. It is known to the person skilled in the art that the time and temperature of an annealing usually 3 are not selected independently. The most relevant metallurgical processes are thermally activated resulting in the situation where a high temperature coupled with a short time can have the same result as a lower temperature and a longer time. The process according to the invention also comprises annealing by recrystallization after cold rolling and an annealing temperature-annealing time combination sufficient to promote an essentially complete recrystallization of Al-Mn alloy. In this condition the greatest conformability is achieved. In one embodiment of the invention, the maximum silicon content of the Al-Mn alloy is 0.3% by weight. In a preferred embodiment of the invention, the maximum silicon content of the Al-Mn alloy is 0.15% by weight. It is known that silicon increases the susceptibility to LFM. Consequently, the silicon content is selected as low as possible. However, the inventors have found that when a silicon content of up to 0.3%, but preferably up to 0.15%, is used, an adequate combination of LFM susceptibility and toughness is obtained. In one embodiment of the invention Cr < 0.18%, preferably at least 0.06%, more preferably 0.08% < Cr < 0.15%, more preferably 0.08% < Cr < 0.12%. When the Cr concentration exceeds 0.18%, the melting of the Al-Mn alloy becomes very difficult as a result of the formation of large intermetallic compounds. The melting of Al-Mn with Cr content below 0.15% below 0.12 does not cause problems. By adding at least 0.08% Cr, the effect thereof on the susceptibility to LFM in combination with the described process conditions results in a combination of adequate susceptibility to LFM and toughness.

The precipitates that are formed in the alloy as a result of the combination of composition and processing conditions reduce the susceptibility to LFM. In one embodiment of the invention the method also comprises the plating of the Al-Mn alloy in 1 at least one side with a brazing alloy of the AA4000 or Al-Si series which optionally comprises up to 2.0% Zn. The plating can be carried out, for example by co-lamination or any other known technique such as spray-plating or cast-ironing. The invention is also constituted as a sheet produced according to the method as described above, wherein the elongation before brazing is at least 18%, preferably at least 19%, so more preferable at least 21% e J or a value n prior to brazing of at least 0.270 or a tensile strength after brazing of at least 140 MPa, preferably of at least 150 MPa. The elongation is measured over a calibrated length of 80 mm, also indicated as A80. In one embodiment of the invention, the life time based on SWAAT of a sample of material for tests after brazing, measured in terms of time to perforation in days and, when tested in accordance with ASTM G85 A3, is at least 15 days, so 10 preferable at least 20 days without perforation. The low susceptibility to LFM is reflected in an improved resistance against corrosion in a formed heat exchanger component, after brazing. In one embodiment of the invention, the sheet as 15 described above is applied as a core to a brazing sheet with or without a different brazing coating or an alloy coating on the water side such as alloys of the types AA7072, AA1145, AA3005 or the type Al-Mn containing 20 Zn in a range of 0.5-5.0%, preferably in the 0.5-2.5% range of the bent tube or for applications which are used under similar conditions. The requirements regarding toughness, formability, susceptibility to LFM and resistance to corrosion are particularly relevant for the application of the sheet as a core in a brazing sheet, for example for application in heat exchangers using bent pipes. The sheet materials produced according to the method described above are particularly suitable for use as a core alloy in brazing sheet materials designed for the manufacture of tube-fin type heat exchanger components such as radiators, core heaters and condensers and for the manufacture of plate-fin type heat exchanger components such as evaporator or oil chiller core plates or radiator tanks or heater cores as a core alloy in brazing fin load materials designed for the elaboration of components for heat exchangers. Now a specific embodiment of the present invention will be explained by the following non-limiting examples.

Table 1: Examples of alloys produced according to the invention These alloys (alloys 1-4) are subjected to a homogenization treatment at various temperatures for various times. The alloys are then veneered on both sides with 7AA4045, 10% of the thickness on each side, followed by preheating before hot rolling at various temperatures for various times, hot rolling at 6.5 mm followed by an annealed interguing at 350 ° C for 3 hours, a first cold rolled to 2.3 mm, followed again by an intercut annealed at 350 ° C for 3 hours and a second cold rolled to a final gauge of 0.5 mm. The alloy is subjected to an annealing treatment by recrystallization to promote essentially complete recrystallization. To test the behavior of LFM, materials stretch between 2 and 10%. The level of drawing that shows the deepest penetration is used for the LFM dies in table 2. Alloy 5 and 6 are veneered on both sides with AA4045, 10% of the thickness on each side, followed by preheating before rolling in hot and later they are laminated in hot to 3.5 mm and laminated in cold to 0.41 mm, without annealed interguing. After cold rolling, the material is subjected to an annealing treatment by recrystallization to promote essentially complete recrystallization. The behavior of LFM is tested as described in the above. The results are presented in Table 2. The alloy designated as "standard" is an alloy which is used for critical applications of LFM. In table 2: "+/-" means between 50 and 60% penetration of the thickness of the core alloy; • "+" means between 30 and 50% penetration of the core alloy thickness; • "++" means less than 30% penetration of the core alloy thickness Since the elongation usually shows a significant dispersion, the value n can be used as an alternative indicator of conformability.A value n of at least 0.270 indicates a good formability in view of the minimum toughness requirement of at least 140 MPa When compared with the standard alloy for critical applications for LFM, alloys according to the invention such as alloy 2-6 in table 2 provide equal LFM performance, but with subsequent tensile properties to braze significantly higher.

Table 2: Examples of alloys produced according to the invention (2-4.5) and reference alloy (1). (n.d. = not determined).

Another particular alloy which can be produced using the method according to the invention has the following compositional ranges, in% by weight: • If 0.8-1.0 and typically about 0.9 Fe 0.25-0.4 and typically about 0.35 • Cu 0.25-0.45 and typically about 0.40 Mn 0.55-0.9 and typically about 0.85 Mg 0.1 -0.22 and typically about 0.15 • Zn 0.06-0.10 and typically about 0.08 • Cr 0.06-0.10 and typically about 0.08 • Zr 0.06-0.10 and typically about 0.08 • the rest of aluminum and unavoidable impurities. The alloy can be used among other things for pipe plates, side supports and heater tanks. Of course it should be understood that the present invention is not limited to the embodiments described and the examples described in the foregoing, but covers any and all of the embodiments within the scope of the description and the following claims:

Claims

- - CLAIMS

1. Process for producing an Al-Mn alloy sheet with improved resistance to liquid film migration when used as a core alloy in brazing sheets, comprising the steps of: melting a composition comprising (in% by weight): 0.5 < Mn < 1.7; 0.06 < Cu < 1.5; Yes < 0.15; Mg < 0.25; you < 0.2; Zn < 2.0; faith < 0.5; at least one element of the group consisting of 0.05 < Zr < 0.25 and 0.05 < Cr < 0.25; other elements < 0.05 each and the total < 0.20, the rest of Al; homogeinization and preheating; hot rolled; cold rolled (which includes intermediate annealing, whenever required) and where the homogenization temperature is at least 450 ° C for a duration of at least 1 hour followed by air cooling at a speed of at least 20 ° C / h and where the preheat temperature is at least 40 ° C for at least 0.5 hours.

2. Process as described in claim 1, wherein the homogenization temperature is between about 530 ° C and 620 ° C for between 1 to 25 hours and wherein the preheating temperature is between about 400 ° C and 530 ° C - - for between 1 to 25 hours.

3. Process as described in claim 1 or 2, wherein Mn is between 0.7 and 1.4%.

4. Process as described in any of claims 1 to 3, wherein Cr < 0.18, preferably 0.08 < Cr < 0.15, more preferably 0.08 < Cr < 0.12.

5. Process as described in any of claims 1 to 4, wherein preferably Mg < 0.15%, more preferably Mg < 0.05%

6. Method as described in any of claims 1 to 5, wherein preferably Zn < 0.4%. Process as described in any of claims 1 to 6, further comprising plating the Al-Mn alloy on at least one side with an Al-Si brazing alloy which optionally comprises up to 2.0% Zn. Method as described in any of claims 1 to 7, further comprising plating the Al-Mn alloy on at least one side with an Al-Si brazing alloy which optionally comprises up to 2.0% Zn and having different brazing coating alloys such as alloys of the types AA7072, AA1145 or AA3005 or of the Al-Mn type containing Zn in a range of 0.5-5.0%, preferably in the range of 0.5-2.5%. 9. Sheet produced as described in any of claims 1 to 8, wherein the elongation before brazing is at least 18%, preferably 19%. 10. Sheet produced as described in claim 9, wherein the tensile strength after brazing is at least 140 MPa, preferably at least 150 MPa. 11. Sheet produced as described in claim 9 or 10, wherein the value n before brazing is at least 0.270. 12. Sheet produced as described in any of claims 9 to 11, wherein the SWAAT lifetime of a sample of test material after brazing, when tested in accordance with ASTM G85 A3 is at least 15 days without perforation. 13. Use of a sheet produced as described in any of claims 1 to 8 or the sheet according to any of claims 9 to 12 as a core alloy in brazing foil designed for the manufacture of heat exchanger components. of the tube-fin type such as radiators, heater cores and condensers. 14. Use of a sheet produced as described in any of claims 1 to 8 or the sheet according to any of claims 9 to 12 as a core alloy in a sheet of brazing designed for the manufacture of heat exchanger components of the plate-fin type such as evaporator or oil cooler core plates or radiator tanks or heater cores. Use of a sheet produced as described in any one of claims 1 to 8 or the sheet according to any of claims 9 to 12 as a core alloy in brazing fin loading materials designed for the manufacture of components for heat exchangers.