JP4109178B2 - Method for producing aluminum alloy fin material for brazing - Google Patents

Description

  The present invention relates to a method for manufacturing a fin material for a heat exchanger for automobiles, which is subjected to press molding or corrugated molding and subjected to brazing.

  In general, aluminum heat exchangers for automobiles are manufactured by a brazing method, and the fin material is assembled to a member such as a tube material or a plate material after press molding, roll molding, or corrugated molding and brazed. Examples of the casting method for the aluminum heat exchanger fin material include a thin plate continuous casting method typified by a twin roll caster, a belt or block type thick plate continuous casting method, and a direct chill method. In addition, several methods for producing fin materials by continuous casting and cold rolling with low equipment costs have been proposed.

  In the thin plate continuous casting method, a cast plate having a thickness of less than 10 mm is usually produced, and the cast plate is cold rolled without hot rolling to obtain a fin material. In recent years, in the twin roll caster method, reduction by a solidification roll is considered, and a pressure load of several thousand to several tens of thousands N (per 1 mm of plate-shaped ingot width) is applied. There is an example in which casting conditions, annealing conditions, and the like are defined (for example, Patent Document 1).

  On the other hand, in the thick plate continuous casting method, a cast plate having a plate thickness of 10 mm or more is manufactured with almost no load applied to the molten metal during casting, and the cast plate is usually subjected to hot rolling and cold rolling, Used for fin material. As an example of the thick plate continuous casting method, there is an example in which an Al—Fe—Si—Mn alloy is continuously cast at a cooling rate exceeding 10 ° C./second (for example, Patent Document 2).

JP-A-2002-241910 Special table 2002-521564

  By the way, the aluminum heat exchanger has been made lighter, that is, thinner, for the purpose of reducing fuel consumption of automobiles. In order to reduce the thickness of the fin material, it is essential to improve the strength of the fin material after brazing in order to maintain the pressure resistance of the heat exchanger. Further, as the strength is improved, the stretchability and stretch flangeability are deteriorated and cracking defects and dimensional variations are increased. Therefore, it is desired that the fin material be improved in formability. However, there is a problem that formability decreases when the amount of addition of alloy elements such as Fe, Si, and Mn is increased to improve the strength of the heat exchanger after brazing.

  The improvement of formability is dealt with by changing the alloying elements and tempering conditions to adjust the material strength and adjusting the molding machine. Currently, almost no countermeasures are taken.

  The present invention was made on the basis of the results of various investigations on the relationship between alloy composition and casting conditions, and the relationship between hot rolling conditions, metal structure, and formability for thinning aluminum alloy fin materials for heat exchangers. The purpose is to provide a method for producing an aluminum alloy fin material for brazing that has good formability for various processes while having sufficiently high strength after brazing for thinning. is there.

  According to a first aspect of the present invention, a molten aluminum or aluminum alloy is continuously cast into a plate-shaped ingot having a thickness of 10 mm or more and 20 mm or less, the pressure load of the molten metal being regulated to 1000 N or less per 1 mm of ingot width, and then the plate It is a manufacturing method of the aluminum alloy fin material for brazing characterized by cold-rolling a cylindrical ingot.

  According to a second aspect of the present invention, a molten aluminum or aluminum alloy is continuously cast into a plate-shaped ingot having a thickness of 10 mm or more and 20 mm or less, the pressure load of the molten metal being regulated to 1000 N or less per 1 mm of ingot width, and then the plate A method for producing an aluminum alloy fin material for brazing, characterized in that a hot ingot is rolled at a reduction rate of less than 50% and then cold rolled.

  A third aspect of the present invention is the method for producing an aluminum alloy fin material for brazing according to the first or second aspect, wherein the continuous casting method is a belt caster method.

  A fourth aspect of the present invention is the method for producing an aluminum alloy fin material for brazing according to any one of the first to third aspects, wherein a release agent is used in the continuous casting method.

  The invention according to claim 5 is characterized in that the aluminum alloy contains Fe of more than 0.1 mass% and 2.2 mass% or less, Si of more than 0.1 mass% and 2.0 mass% or less, and Mn of more than 0.2 mass% and 2.5% mass% or less. Containing, if necessary, containing 0.05 mass% to 0.5 mass% or less of Ni, 0.05 mass% to 0.5 mass% or less of Cu or one or two of Cu, and 0.3 mass% or less of Cr, Contains one or more of 0.3 mass% or less of Zr, 0.3 mass% or less of Ti, 4 mass% or less of Zn, 0.3 mass% or less of In, 0.3 mass% or less of Sn, or 1 mass% or less of Mg. 5. The method for producing an aluminum alloy fin material for brazing according to any one of claims 1 to 4, wherein the balance is an aluminum alloy comprising inevitable impurities.

  In the present invention, a predetermined composition of aluminum or an aluminum alloy is cast by a continuous casting method by defining casting conditions to obtain a plate-shaped ingot having a rapidly solidified structure in the vicinity of the surface layer. No hot rolling is performed, or hot rolling is performed at a rolling rate of less than 50%, and the rapidly solidified structure is brought to the fin material after cold rolling, so that the obtained fin material has high strength and is formed. The fin material can be thinned. Further, when a mold release agent is applied to the inner surface of the mold by the continuous casting, the mold release agent adheres to the ingot surface as particles having a lubricating effect, and the fin material is further improved in moldability by remaining on the fin material. .

  When the inventors of the present invention variously study the thinning of the fin material, if the alloy concentration is increased for thinning, a coarse compound crystallizes during casting, and this coarse crystallized phase tends to be a starting point of cracking during molding. It has been found that this crack is particularly likely to occur when the alloy element is Fe, Si, Mn or the like. Further investigation has been carried out, and the occurrence of cracks due to the crystallization phase is caused by making the ingot surface a fine rapidly solidified structure, suppressing the rolling rate in hot rolling low, and the coarse crystallization phase inside the ingot during cold rolling. It was clarified that it can be prevented by splitting.

In the present invention, in order to obtain a fine rapidly solidified structure in the vicinity of the ingot surface, the ingot thickness needs to be 10 mm or more. If the ingot thickness is less than 10 mm, the rolling rate up to the final fin material is small and the crystallization phase is not sufficiently divided. As a result, the strength of the fin material is insufficient, and the crystallization phase of the size that will be the starting point of fracture The number increases and the moldability decreases. On the other hand, if the ingot thickness exceeds 20 mm, the cooling rate becomes slow and the crystallization phase becomes coarse.
Therefore, in the present invention, the ingot thickness is specified to be 10 mm or more and 20 mm or less. The ingot thickness is particularly preferably from 10 mm to 15 mm.

  In the present invention, in order to make the vicinity of the ingot surface a fine rapidly solidified structure, it is necessary to cast the molten metal with a pressure load of 1000 N or less per 1 mm of the ingot width. This is because the inventors conducted experiments under various casting conditions, and when the pressure load of the molten metal is larger than 1000 N per 1 mm of ingot width, the fine structure near the surface is destroyed and there is no difference from the structure in the central part. It was confirmed. The pressure load of the molten metal is particularly preferably 600 N or less per 1 mm ingot width.

  In the present invention, a belt caster method that can easily control the pressure load to a low level is recommended as the continuous casting method.

  As described above, the present invention has a fine rapidly solidified structure in the vicinity of the ingot surface, and this is brought to the fin material after cold rolling to improve the moldability of the fin material. In order to further improve the moldability of the fin material, the present inventors examined the relationship between the moldability of the fin material and the material surface. As a result, it has been found that, in order to improve the moldability, it is effective to attach particles having a lubricating effect to the material surface in addition to applying the lubricating oil.

The particles having the lubricating effect may be adhered to the material surface by coating or the like before the molding process. However, this method increases the number of steps and is disadvantageous in terms of cost, and is coated so that the particle density is uniform. It is difficult to reduce the lubricity.
Therefore, the present inventors examined a method for uniformly and thinly applying the particles to the surface of the fin material. As a result, when the mold release agent is applied to the continuous casting mold, the pressure load of the molten metal is specified, and the rolling rate in hot rolling is specified to be less than 50% (including 0%), the particles are cold-rolled. It was found that it remained on the surface of the material later, which increased the lubricity between the material and the inner surface of the mold during fin molding, and improved moldability.

As the mold release agent, silica or carbon is highly recommended because of its lubricating effect. Further, when the pressure load of the molten metal during continuous casting is regulated to 1000 N or less per 1 mm of ingot width, the amount of release agent released from the surface is remarkably reduced. The pressure load is particularly preferably 600 N or less per 1 mm ingot width.
The prescribed values of the mold release agent and the pressure load were found by the inventors through experiments under various conditions.

  The inventors of the present invention hot rolled under various conditions, then cold rolled to produce a fin material, and the structure thereof was observed. It was found that a rapidly solidified structure in the vicinity was destroyed or particles having a lubricating effect attached to the surface were coated on a roll and separated. Therefore, in order to improve the moldability of the fin material by bringing the rapidly solidified structure or particles having a lubricating effect to the fin material, hot rolling is not performed at all or the hot rolling rate is set to less than 50%. There is a need.

  In the present invention, other conditions such as the heating temperature before hot rolling are arbitrary as long as the formability of the fin material is not impaired. The cold rolling rate is not particularly specified. The reason is that in cold rolling, roll coating does not occur, and the rapidly solidified structure in the vicinity of the surface and particles having a lubricating effect do not peel off. Therefore, under normal cold rolling conditions, the effect of improving the formability of the fin material of the present invention is not impaired. By producing the fin material under such conditions, particles having a lubricating effect attached to the material surface as a release agent are brought to the cold rolled material without being separated by hot rolling. For this reason, the moldability of the fin material is improved.

  In this invention, it does not prescribe | regulate also about the intermediate annealing conditions performed during cold rolling. The intermediate annealing may be performed by general heating such as batch annealing or continuous annealing. Various tempering conditions and the final cold rolling rate may be determined in consideration of the required characteristics of the fin material.

  The present invention is an aluminum alloy of a desirable fin material used in the present invention, containing appropriate amounts of Fe, Si, and Mn as essential elements, and optionally containing one or two of Ni and Cu. Further, it contains one or two or more of Cr, Zr, Ti, Zn, In, Sn, and Mg as required.

Hereinafter, the reasons for defining the action and content of the alloy element will be described.
Fe contributes to improving the strength of the fin material after brazing. The reason why the content is specified to be more than 0.1 mass% and 2.2 mass% or less is that the effect is not sufficiently obtained when the content is less than 0.1 mass%, and the crystallized phase becomes coarse when the content exceeds 2.2 mass%. This is because the moldability cannot be improved even by this manufacturing method. A large amount of Fe deteriorates workability. The Fe content is more preferably 0.7 mass% or more and less than 1.9 mass%.

  Si also contributes to improving the strength of the fin material after brazing. The reason why the content is specified to exceed 0.1 mass% and below 2.0 mass% is that the effect cannot be sufficiently obtained at 0.1 mass% or less, and when it exceeds 2.0 mass%, the melting point of the alloy is lowered, and the brazing fin material This is because the fin material buckles due to diffusion of the brazing material. The Si content is more preferably 0.3 mass% or more and 1.6 mass% or less.

  Mn also contributes to improving the strength of the fin material after brazing. The reason why the content is specified to be more than 0.2 mass% and not more than 2.5 mass% is that the effect cannot be sufficiently obtained if the content is less than 0.2 mass%, and if it exceeds 2.5 mass%, the number of Al-Fe-Mn crystallization phases This is because both the size increases and the moldability cannot be improved even in the production method of the present invention. The Mn content is more preferably more than 0.3 mass% and not more than 2.0 mass%.

  In the present invention, if necessary, one or two of Ni exceeding 0.05 mass% and 0.5 mass% or less and Cu exceeding 0.05 mass% and 0.5 mass% or less are added. All of these elements are added to improve the strength. However, the effect cannot be obtained sufficiently at 0.05 mass% or less, and if it exceeds 0.5 mass%, the Al-Fe-Ni crystallization phase becomes coarse and the formability is reduced. Getting worse. Cu, like Si, is 0.5 mass% or less in order to lower the melting point of the alloy.

  In addition to the above additive elements, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr, 0.3 mass% or less of Ti, 4 mass% or less of Zn, 0.3 mass% or less of In, 0.3 mass% or less of Sn, 1 mass You may contain 1 type (s) or 2 or more types of Mg below%. These alloy elements have an important effect on various properties required for the fin material. The reasons for defining the action and content of each element are described below.

  Cr and Zr contribute to improving the strength of the fin material after brazing, increase the droop resistance of the fin by coarsening the recrystallized grains of the fin material during brazing, and prevent the diffusion of the wax into the fin. . The reason why the contents of Cr and Zr are each 0.3 mass% or less is that when the content exceeds 0.3 mass%, an intermetallic compound grows and the above-mentioned properties deteriorate. The content of Cr and Zr is more preferably 0.08 mass% or less.

  Ti improves the strength after brazing and refines the solidified structure. The reason for prescribing its content to be 0.3 mass% or less is that when it exceeds 0.3 mass%, the sacrificial anticorrosive effect and conductivity of the fin material are lowered. 0.08 mass% or less, particularly 0.02 mass% or less is more preferable.

Zn, In, and Sn enhance the sacrificial anticorrosion effect of the fin material. Which element is added to what extent may be determined in consideration of the anticorrosive properties and conductivity required for the fin material. However, In and Sn exhibit a sufficient sacrificial anode effect even if they are added in a small amount, but there are problems that they are expensive and impede the recyclability of scraps. In the present invention, the addition of Zn is particularly recommended.
Zn is specified to be 4 mass% or less in order to reduce the corrosion resistance of the fin material itself as the addition amount is increased, but 2 mass% or less, particularly 1 mass% or less is recommended. The addition amount of Zn may be determined depending on the material to be anticorrosion, but it is usually desirable to add 0.5 mass% or more. The addition amount of In and Sn is specified to be 0.3 mass% or less in consideration of high cost and recyclability.

Mg contributes to strength improvement. The reason why the content is specified to be 1 mass% or less is that when Mg exceeds 1 mass%, it reacts with the flux by the NB brazing method and the brazing property is remarkably reduced. The Mg content is preferably 0.5 mass% or less, particularly preferably 0.05 mass% or less.
Hereinafter, the present invention will be described in detail with reference to examples.

The Al alloys (No. A to F) of the present invention composition shown in Table 1 were melted, and the obtained molten metal was cast into a plate ingot having a thickness of 10 to 20 mm by a belt caster method. The fin material was manufactured by cold rolling after hot rolling or by cold rolling without hot rolling. Some applied silica or carbon as a mold release agent to the inner surface of the belt caster mold.
Table 2 shows the thickness of the plate-shaped ingot, the pressure load applied by the pulley (belt wheel), the hot rolling rate, the cold rolling process, and the like. All were changed within the conditions prescribed in the present invention.

  As Comparative Example 1, a fin material was produced by the same method as in Example 1 except that an Al alloy (No. G to J) having a composition outside the scope of the present invention shown in Table 1 was used.

  As Comparative Example 2, a fin material was produced by the same method as in Example 1 except that the casting conditions and the hot rolling conditions were changed to conditions other than those specified in the present invention (see Table 2).

  A test piece was cut out from each fin material produced in Example 1 and Comparative Examples 1 and 2, and the Erichsen value, press formability, corrugated formability, and tensile strength were examined.

The Eriksen value was measured according to JIS-Z2247.
The press formability was examined by performing a deep drawing test. The deep drawing test was performed using a cylindrical punch having a diameter of 50 mm and a shoulder R of 9 mm, a punch speed of 200 mm / second, and a wrinkle holding force of 300 kgf, and a lubricant was applied to both sides of the test piece. The number of tests was 30 for each (n = 30).

  The press formability was examined by visually and visually observing the test piece after the test. If neither rupture nor wrinkle is observed, press formability is very good (◎). If there is no rupture but some wrinkles are observed, press formability is good (◯). If there are many wrinkles or breakage is observed It was determined to be defective (x).

  The corrugate formability was examined by forming each fin material into a corrugated shape having a number of peaks of 100 and a pitch of 2.5 mm (set value) using a corrugating machine. Corrugated formability was judged to be good (◯) when the crest having a crest of 2.5 mm ± 20% or more was less than 10 out of 100, and judged to be bad (×) if it was 10 or more.

The tensile strength was examined by heating a JIS No. 5 test piece in a nitrogen gas atmosphere under the same conditions as brazing (600 ° C. × 3 minutes), and performing a tensile test at room temperature. The tensile strength is shown as an average value (n = 5).
The survey results are summarized in Table 3. Table 3 also shows the presence or absence of material breakage during cold rolling.

  As is apparent from Table 3, Example No. of the present invention example. All of Nos. 1 to 8 could be produced satisfactorily without breaking during cold rolling. The press moldability and corrugated moldability were both good, and the Erichsen value and tensile strength were also high. In particular, no. No. 7 and carbon coated no. No. 8 was extremely excellent in press formability.

  On the other hand, No. 1 of Comparative Example 1 was used. Nos. 9 to 12 were inferior in characteristics because the alloy composition was outside the scope of the present invention. That is, no. No. 9 has a large amount of Fe. Since No. 11 had a large amount of Mn, the Erichsen value, press formability, and corrugated formability were all poor. No. No. 10 was inferior in Erichsen value and press formability due to a large amount of Si. No. No. 12 was inferior in tensile strength after brazing heating because Fe was low. No. No. 9 had a large amount of Fe, and fracture occurred during cold rolling.

  Moreover, No. 2 of Comparative Example 2 was used. In Nos. 13 to 16, since the casting conditions or hot rolling conditions were outside the scope of the present invention, there were no fine rapidly solidified structures or particles having a lubricating effect on the material surface, and all of them were inferior in press formability. Furthermore, no. Nos. 13 and 15 have poor Erichsen values and corrugated moldability. No. 16 was inferior in tensile strength.

Claims (5)

  Aluminum or aluminum alloy molten metal is continuously cast into a plate-shaped ingot having a thickness of 10 mm or more and 20 mm or less, with the pressure load of the molten metal being regulated to 1000 N or less per 1 mm of ingot width, and then cold-rolling the plate-shaped ingot The manufacturing method of the aluminum alloy fin material for brazing characterized by doing.   Aluminum or aluminum alloy molten metal is continuously cast into a plate-shaped ingot having a thickness of 10 mm or more and 20 mm or less, with the pressure load of the molten metal being regulated to 1000 N or less per 1 mm of the ingot width, and then the plate-shaped ingot is reduced by 50%. A method for producing an aluminum alloy fin material for brazing, comprising hot rolling at less than% and then cold rolling.   3. The method for producing an aluminum alloy fin material for brazing according to claim 1, wherein the continuous casting method is a belt caster method.   4. The method for producing an aluminum alloy fin material for brazing according to claim 1, wherein a release agent is used in the continuous casting method.   The aluminum alloy contains Fe of more than 0.1 mass% and less than 2.2 mass%, Si of more than 0.1 mass% and less than 2.0 mass%, and Mn of more than 0.2 mass% and less than 2.5% mass%, if necessary Containing 0.05 mass% to 0.5 mass% or less of Ni, 0.05 mass% to 0.5 mass% or less of Cu or one or two kinds of Cu, 0.3 mass% or less of Cr, 0.3 mass% or less of Zr, Aluminum containing one or more of 0.3mass% or less of Ti, 4mass% or less of Zn, 0.3mass% or less of In, 0.3mass% or less of Sn, or 1mass% or less of Mg, and the balance being inevitable impurities The method for producing an aluminum alloy fin material for brazing according to any one of claims 1 to 4, which is an alloy.