JP5326123B2 - Aluminum alloy brazing sheet manufacturing method and aluminum alloy brazing sheet - Google Patents

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 . cold rolling (including intermediate anneals whenever required), and wherein the homogenisation temperature is at least 450 °C for a duration of at least 1 hour followed by an air cooling at a rate of at least 20 °C/h and wherein the pre-heat temperature is at least 400 °C for at least 0.5 hour.

Description

Field of Invention

  The present invention relates to a method for producing an Al-Mn alloy sheet having improved liquid film migration resistance when used as a core alloy in a brazing sheet material. The present invention relates to an Al—Mn alloy sheet produced by the method and the use of the alloy sheet.

  In brazing applications, it is known that a phenomenon called “liquid film migration” or LFM causes a reduction in the overall performance of brazed products such as evaporators, radiators, heater cores, and the like. In the literature, the term “LFM” is also referred to as “core melting” or “core penetration” or “core erosion”. As used herein, the term “LFM” is intended to refer to all these technical terms. The exact mechanism that causes LFM has not been fully understood so far, but the presence of a certain amount of dislocations in the core alloy of the brazed sheet may increase the severity of LFM. The sensitivity of a material to LFM is the same for both soft and weakly cold-worked conditions of the same material, both fully annealed (O-tempering) and strain hardening, and / or stress-relieved tempered (eg, H14, H24, etc.). Is known to be relatively low. The term “weak cold work” typically refers to industrial processes applied to the manufacture of components of heat exchangers, such as evaporators, or oil cooler core plates, bent tubes, etc., such as stamping, roll forming. Or the deformation caused by tension leveling. When deforming a brazing sheet consisting of a core alloy and an Al-Si clad alloy to form a product, followed by a brazing cycle, a small amount of deformation is sufficient to induce LFM in the brazing sheet. I think that the. If the LFM progresses excessively into the core alloy, the brazeability, strength and corrosion resistance are reduced. Alloying elements that delay recrystallization, such as chromium, zirconium and vanadium, are known to increase sensitivity to LFM. Manganese dispersoids have also been found to delay recrystallization and thus increase sensitivity to LFM. The amount and size of the manganese dispersoid varies depending on the processing route of the brazing sheet.

  For brazing applications, the core alloy of the brazed sheet product requires a good combination of strength and formability. Obviously, the sensitivity to LFM needs to be low enough to ensure sufficient corrosion resistance and brazeability. High strength can be obtained by alloying with elements such as silicon, manganese, chromium, zirconium or vanadium. However, these alloying elements also increase the sensitivity to LFM. Non-O-tempering, such as H14 tempering or H24-tempering, has also been proposed to reduce sensitivity to LFM. However, these tempers effectively lower the LFM, but often sacrifice the moldability of the brazed sheet product. Other alternative processes, such as mild cold deformation, such as tension leveling, or the use of non-recrystallized surface layers, are difficult to control in mass production and are therefore reproducible and / or formable. May be damaged.

  The object of the present invention is to improve the liquid film migration resistance when used as a core alloy in a brazing sheet, and the good strength / formability combination of the alloy results in sufficiently low sensitivity to LFM and sufficient corrosion resistance. It is to provide a combined Al-Mn alloy sheet.

  It is also an object of the present invention to provide the Al—Mn alloy sheet that is easy to control and provides a reproducible product.

  Improved liquid film migration resistance in bent tubes, evaporators or oil cooler core plates, fin materials, etc., and good strength / formability combination of the alloy, low enough sensitivity to LFM, good brazing It is also an object of the present invention to provide an Al-Mn alloy sheet, which is combined with the properties and sufficient corrosion resistance.

According to the present invention, one or more of these objects is a method for producing an Al-Mn alloy sheet with improved liquid film migration resistance when used as a core alloy in a brazing sheet,
・ (By weight)
0.5 <Mn ≦ 1.7, preferably 0.6 to 1.7,
0.06 <Cu ≦ 1.5, preferably 0.2 to 1.5,
Si ≦ 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 element group consisting of 0.05 <Zr ≦ 0.25 and 0.05 <Cr ≦ 0.25 Other elements <0.05 and total <0.20
Casting a composition comprising the remainder of Al,
・ Homogenization and preheating process,
・ Hot rolling process,
-Cold rolling (including intermediate annealing if necessary), the homogenization being carried out at a temperature of at least 450 ° C for at least 1 hour, followed by a rate of at least 20 ° C / h Air-cooled and the preheating is accomplished by a method of performing at a temperature of at least 400 ° C. for at least 0.5 hours.

  Casting is performed using conventional manufacturing techniques such as DC casting or continuous casting.

  The method of the present invention can produce an Al-Mn alloy that combines a good strength / formability combination with a sufficiently low sensitivity to LFM and sufficient corrosion resistance when used as a core alloy in a brazed sheet. it can. The inventors have surprisingly found that chromium adversely affects the sensitivity of LFM to LFM due to its effect of retarding the recrystallization of the alloy, but the chemical composition and processing parameters of the alloy. It has been found that, in particular, a combination of homogenization and preheating steps gives a product with a sufficiently low sensitivity to LFM and thus with a sufficient corrosion resistance. Cr-containing and / or Zr-containing precipitates formed in the alloy by a combination of composition and processing conditions reduce the sensitivity to LFM. Chromium strengthens the alloy and recrystallization of the alloy provides sufficient formability. The present inventors have found that similar results can be obtained by alloying with V or by alloying with a combination of V and Cr and / or Zr.

  In one embodiment of the invention, the Cr and / or Zr content is at least 0.08%. The inventors have found that when a chromium content of at least 0.08% or a zirconium content of at least 0.08% or a combination thereof is combined with the above processing conditions, a higher strength is achieved with sufficient LFM resistance. It was found that a combination of

  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 deleterious effects of magnesium on the flux used during brazing in a controlled atmosphere. In one embodiment of the invention, the copper content is 0.7-1.2%.

  In one embodiment of the invention, the manganese content is 0.7-1.4%. If the manganese content exceeds 1.4%, the processing becomes more difficult, and if it is less than 0.7%, the strength of the alloy becomes insufficient. In one embodiment of the present invention, the maximum zinc content is preferably 0.4% in order to prevent the core alloy from becoming too anodic in certain applications. In one embodiment of the invention, the iron content is preferably less than 0.35% in order to prevent the formation of large iron-containing intermetallic compounds which are not preferred during industrial casting operations.

  In one embodiment of the invention, the homogenization is carried out at a temperature of about 530 ° C. to 620 ° C., preferably 530 to 595 ° C., preferably 1 to 25 hours, more preferably 10 to 16 hours, and the preheating is carried out at a temperature of about 400 C. to 530.degree. C., preferably 420 to 510.degree. C., preferably 1 to 25 hours, more preferably 1 to 10 hours. In the alloys of the present invention, the best compromise between strength, formability, sensitivity to LFM and corrosion resistance is obtained when the temperature and time of homogenization and the temperature and time of preheating are selected within specified limits. This and particularly important compromise appears to be obtained when the alloy is processed at the preferred temperatures and times described above.

  As is known to those skilled in the art, the annealing time and temperature are usually not independently selected. Most related metallurgical processes are thermally activated, and the combination of high temperature and short time results in the same result as the combination of low temperature and long time.

  The process of the present invention also comprises recrystallization annealing after cold rolling with a combination of annealing temperature-annealing time sufficient to promote substantially complete recrystallization of the Al-Mn alloy. Under this condition, the best moldability 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. Silicon has been found to increase sensitivity to LFM. Therefore, the silicon content should be chosen as low as possible. However, the inventors have found that a sufficient combination of sensitivity and strength to LFM is obtained when using silicon contents up to 0.3%, preferably up to 0.15%.

  In one embodiment of the invention, Cr ≦ 0.18%, preferably at least 0.06%, more preferably 0.08% <Cr ≦ 0.15%, and even more preferably 0.08% <Cr ≦ 0. 12%. When the Cr level exceeds 0.18%, a large intermetallic compound is formed, and as a result, casting of an Al—Mn alloy becomes very difficult. Casting Al-Mn alloys with a Cr content of less than 0.15% or less than 0.12 does not cause problems. By adding at least 0.08% Cr, the combination of its effect on LFM sensitivity and the above treatment conditions provides a sufficient combination of LFM sensitivity and strength. Precipitates formed in the alloy by a combination of composition and processing conditions reduce the sensitivity to LFM. In one embodiment of the present invention, the method comprises cladding an Al-Mn alloy at least on one side with an AA-4000 series or Al-Si brazing alloy optionally comprising up to 2.0% Zn. Comprising. The cladding can be performed by, for example, roll bonding or any other known technique, such as spray cladding or cast cladding.

  The present invention provides a process produced by the above method having an elongation before brazing of at least 18%, preferably at least 19%, more preferably at least 21% and / or an n-value of at least 0 before brazing. .270 and / or a sheet having a tensile strength after brazing of at least 140 MPa, preferably at least 150 MPa. Elongation is measured over a gauge length of 80 mm and is also referred to as A80.

  In one embodiment of the invention, when the specimen after brazing is tested according to ASTM G85A3, the SWAAT lifetime, measured in terms of the time to open the hole and expressed in days, with no holes formed is at least 15 days, preferably at least 20 days. The low sensitivity to LFM is reflected in improved corrosion resistance in heat exchanger components formed after brazing.

  In one embodiment of the present invention, the above sheet is made of a non-brazing liner or water side liner alloy in a bent tube, such as Zn in the range of 0.5-5.0%, preferably 0.5-2.5%. Used in, for use as a core in brazing sheets with or without AA7072, AA1145 or AA3005 or Al-Mn type alloys, or for use under similar conditions. The requirements regarding strength, formability, LFM sensitivity and corrosion resistance are particularly important for the application of the sheet, for example as the core of a brazing sheet for heat exchangers using folded tubes.

  The sheet material produced by the above method is used in the manufacture of parts of tube-fin heat exchangers, such as radiators, heater cores and condensers, or in plate-fin heat exchangers, such as evaporators or oil cooler core plates or radiators. It is also particularly suitable for use as a core alloy for brazing sheets when brazing fin raw materials in the manufacture of heater core tank parts.

  Specific embodiments of the invention will now be illustrated by the following non-limiting examples.

Table 1 Examples of alloys produced according to the invention

Alloy CuFeSiMnMgTiCrCrZr
1 (Standard) 0.76 0.18 0.10 1.14 0.03 0.13 <0.01 <0.01
2 0.80 0.21 0.09 1.15 0.05 0.13 0.05 0.05
3 0.78 0.21 0.09 1.20 0.03 0.13 0.11 <0.01
4 0.78 0.20 0.08 1.16 0.02 0.12 0.15 <0.01
5 0.72 0.20 0.07 1.21 0.01 0.14 0.08 <0.01
6 0.76 0.15 0.08 1.19 0.01 0.12 0.06 <0.01
Standard 0.5- <0.5 <0.3 0.65- <0.02 0.08---
0.7 1.0 0.10
The other elements are each <0.05, the total is <0.20, and the rest is Al.

  These alloys (Alloy 1-4) were subjected to a homogenization treatment at various temperatures for various times. Subsequently, both sides of these alloys are clad with AA4045 to 10% of the thickness on each side, followed by preheating before hot rolling at various temperatures for various times and heat to 6.5 mm. Followed by intermediate annealing at 350 ° C. for 3 hours, first cold rolling to 2.3 mm, intermediate annealing again at 350 ° C. for 3 hours, and second cold rolling to a final gauge of 0.5 mm . The alloy was subjected to a recrystallization annealing process to promote substantially complete recrystallization. In order to test LFM behavior, the material was stretched 2-10%. The extension level that showed the deepest penetration was used for the LFM data in Table 2.

Both sides of Alloys 5 and 6 are clad with AA 4045 to 10% of thickness on each side, followed by preheating prior to hot rolling, followed by 3.5 mm without intermediate annealing. Hot rolled and cold rolled to 0.41 mm. After cold rolling, the material was subjected to a recrystallization annealing process to promote substantially complete recrystallization. LFM behavior was tested as described above. The results are shown in Table 2. An alloy called “standard” is an alloy used in applications where LFM is a problem. In Table 2,
“+/−” means 50 and 60% penetration of core alloy thickness.
“+” Means 30 and 50% penetration of the core alloy thickness.
“++” means <30% penetration of core alloy thickness.

  Elongation usually exhibits large variations, so the n-value can be used as another guide for moldability. An n-value of at least 0.270 suggests good moldability for a minimum strength condition of at least 140 MPa. Compared to standard alloys used in applications where LFM is an issue, the alloys of the present invention, such as Alloy 2-6 in Table 2, have the same LFM performance but significantly higher tensile properties after brazing.

Table 2 Examples of alloys produced according to the invention (2-4, 5) and reference alloy (1) (nd = not measured)

Alloy Homogenization Preheating Before brazing After brazing SWAAT specimen LFM
℃ / h ℃ / h A80 n-value 0.2PS Resistance to UTS generation
% MPa MPa days *
1 610/8 430/24 17.4 0.264 60 133 26 +/-
2 610/8 430/24 21.2 0.276 69 152 38 +
3 610/8 490/24 19.4 0.296 63 155> 40 +
3 610/8 490/2 19.4 0.286 66 152> 40 +
3 610/24 430/24 21.7 0.285 61 153> 40 +
3 580/12 430/5 19.5 0.300 68 156 37 +
3 580/12 490/2 22.2 0.304 62 152 35 ++
3 550/12 490/24 18.6 0.307 66 157 22 +
3 550/12 490/2 24.5 0.300 65 159 29 ++
4 610/8 430/24 21.1 0.277 70 153 33 ++
5 610/10 430/1 24.0 0.282 61 155 24 ++
6 610/10 430/1 ndndndndnd ++
Standard ndnd 50 130 nd ++

Another special alloy that can be produced using the method of the present invention, in weight percent, has the following compositional range:
Si 0.8-1.0, typically about 0.9
Fe 0.25-0.4, typically about 0.35
Cu 0.25-0.45, typically about 0.40
Mn 0.55-0.9, typically about 0.85
Mg 0.1-0.22, typically about 0.15
Zn 0.06 to 0.10, typically about 0.08
Cr 0.06-0.10, typically about 0.08
Zr 0.06-0.10, typically about 0.08
Aluminum remaining and inevitable impurities This alloy can be used for tube plates, side supports and header tungsten, among others.

  Of course, the present invention is not limited to the embodiments and examples described above, but encompasses all embodiments that fall within the scope of the description and claims.

Claims (17)

A Al-Mn alloy sheet manufacturing method having the liquid film migration resistance when used as core alloy in brazing sheet,
・ (By weight)
0.5 <Mn ≦ 1.7,
0.7 <Cu ≦ 1.2,
Si ≦ 0.15,
Mg ≦ 0.05,
Ti 0.12-0.14 ,
Fe ≦ 0.5,
0.05 <Cr ≦ 0.25
<0.05 and total <0.20 for each other element
Casting a composition comprising the remainder of Al,
・ Homogenization treatment
・ Clad both sides of Al-Mn alloy with Al-Si brazing alloy,
・ Preheat,
・ Hot rolling
A step of cold rolling, wherein the homogenization is performed at a temperature of 530 ° C. to 620 ° C. for 1 to 25 hours, followed by air cooling at a rate of at least 20 ° C./h, and the preheating, The method of performing at the temperature of 400 to 530 degreeC for 1 to 25 hours.   The method according to claim 1, wherein the cold rolling is performed with intermediate annealing.   The method according to claim 1 or 2, wherein Mn is 0.7 to 1.4%.   The method according to claim 1, wherein Cr ≦ 0.18.   The method according to claim 1, wherein 0.08 <Cr ≦ 0.15.   The method according to claim 1, wherein 0.08 <Cr ≦ 0.12. AA7072, AA1145, AA3005 , wherein both sides of the Al-Mn alloy are clad with an Al-Si brazing alloy, and the Al-Mn alloy contains Zn in a range of 0.5 to 5.0%. that it has a non braze liner alloy selected from the group consisting of al-Mn type alloy, the method according to any one of claims 1-6. AA7072, AA1145, AA3005 , wherein both sides of the Al-Mn alloy are clad with an Al-Si brazing alloy, and the Al-Mn alloy contains Zn in the range of 0.5-2.5%; that it has a non braze liner alloy selected from the group consisting of al-Mn type alloy, the method according to any one of claims 1-6. It is before brazing elongation of at least 18% A method according to any one of claims 1-8. 10. A method according to claim 9 , wherein the elongation before brazing is at least 19%. The method according to claim 9 , wherein the tensile strength after brazing is at least 140 MPa. The method of claim 11 , wherein the tensile strength after brazing is at least 150 MPa. 13. A method according to any one of claims 9 to 12 , wherein the n-value prior to brazing is at least 0.270. 14. A method according to any one of claims 9 to 13 wherein the SWAAT lifetime without holes is at least 15 days when the brazed specimen is tested according to ASTM G85A3. A group consisting of a radiator, a heater core and a condenser of a sheet produced by the method according to any one of claims 1 to 8 or a sheet produced by the method according to any one of claims 9 to 14. Use of a brazed sheet as a core alloy for the manufacture of parts of a tube-fin heat exchanger selected from: An evaporator, an oil cooler core plate, and a radiator of a sheet manufactured by the method according to any one of claims 1 to 8 or a sheet manufactured by the method according to any one of claims 9 to 14. As a core alloy of brazing sheets for the production of parts of plate-fin heat exchangers selected from tanks and heater cores. A fin raw material intended for the manufacture of heat exchanger components of a sheet produced by the method according to any one of claims 1-8 or a sheet produced according to any one of claims 9-14. Use as a core alloy when attaching.