JP5257670B2 - Method for producing aluminum alloy material excellent in creep resistance - Google Patents

Description

  The present invention relates to a method for producing an aluminum alloy material excellent in creep resistance, and particularly relates to a method for producing an Al—Mn alloy material useful as a material forming part of a brazing structure such as a heat exchanger.

In heat exchangers for automobiles configured by brazing, members formed from Al-Mn alloy materials are frequently used. In recent years, heat exchangers (high-performance intercoolers, air conditioners using CO ₂ refrigerant, etc.) that are used under higher temperature and pressure than conventional ones have been developed in order to improve fuel efficiency and environmental friendliness of automobiles. Yes. In order to cope with this, an improvement in creep resistance at a high temperature, specifically 150 to 270 ° C., is also required for the Al—Mn alloy material which is a member material.

  For example, Patent Documents 1 and 2 propose techniques for improving high-temperature strength by controlling precipitates, adding alloy elements, and the like for Al—Mn alloy materials for heat exchangers that are brazed and used.

Special table 2007-530794 gazette JP-T-2004-524442

  The techniques disclosed in Patent Documents 1 and 2 are based on strengthening by adding an alloy element such as Mg. However, for example, the addition of Mg has a problem that the brazing property when using a flux is lowered. Further, Patent Documents 1 and 2 do not disclose a technique for improving the creep resistance at the use temperature after brazing.

  This invention is made | formed in view of the said problem, and it aims at providing the manufacturing method of the aluminum alloy material from which high brazing property and the high creep resistance under the high temperature after brazing are acquired.

In order to achieve the above object, the method for producing an aluminum alloy material excellent in creep resistance according to the present invention,
Containing Mn: 1.0 to 1.5% by mass, Cu: 0.05 to 0.2% by mass, and regulating Si as impurities to less than 0.6% by mass and Fe to less than 0.7% by mass , A process of cold working the alloy material consisting of Al and inevitable impurities to the final dimensions,
Applying a solution treatment for holding the cold worked alloy material at a temperature of 560 to 620 ° C. for 0.5 to 2000 hours,
It is characterized by that.

  According to the present invention, an appropriate solution treatment is applied to an Al-Mn alloy (JIS3003 alloy) that is frequently used as a member for a heat exchanger, thereby increasing solid solution strengthening by Mn and Cu and growing crystal grains. Therefore, it is possible to provide an aluminum alloy material excellent in creep resistance while obtaining high brazing properties.

  Hereinafter, embodiments of the present invention will be specifically described. The present inventors emphasized that Mg-less JIS3003 alloy is frequently used as a member for heat exchangers, and improved the creep resistance at 150 to 270 ° C. of such a general Al—Mn alloy. The method to do was examined. The present inventors have found that the creep resistance of the Al-Mn alloy sheet can be improved by heat treatment under appropriate conditions after rolling to the final sheet thickness, and further the creep resistance after brazing. Also found to be improved.

  Hereinafter, the manufacturing method of the aluminum alloy (hereinafter also referred to as Al-Mn alloy) material of the present embodiment will be described. In the following description, a method for manufacturing an Al—Mn alloy plate will be mainly described.

  First, an alloy material used in this embodiment is prepared. The target alloy material of the present invention contains Mn: 1.0 to 1.5% by mass, Cu: 0.05 to 0.2% by mass, Si as an impurity is less than 0.6% by mass, Fe is contained. The Al—Mn alloy is limited to less than 0.7% by mass, and the balance is made of Al and inevitable impurities.

  When Si is contained in an amount of 0.6% by mass or more, or Fe is contained in an amount of 0.7% by mass or more, formability and corrosion resistance are hindered.

The Al—Mn alloy may contain 0.1% by mass or less of Zn as an inevitable impurity element with respect to the aluminum alloy. Furthermore, Ti: 0.01% by mass to 0.15% by mass, which is a component derived from a finer commonly used in aluminum casting, alone or B (boron): 0.0001% by mass to 0%. .05% by mass may be contained. When the Ti content is less than 0.01% by mass and the B content is less than 0.0001% by mass, the effect of refining the texture of the ingot is reduced. Further, if the Ti content exceeds 0.15% by mass, TiAl ₃ crystallizes and formability is inhibited, and if the B content exceeds 0.05% by mass, coarse particles of TiB ₂ are mixed and formability is inhibited. The For the above reasons, the Ti and B contents are preferably within the above range.

  JIS standard 3003 alloy corresponds to the above target alloy range.

  Note that Mn, which is an essential alloy component, is mostly in a solid solution state by solution treatment, and has an effect of increasing resistance to creep. When the amount of Mn added is less than 1.0 to 1.5% by mass, the effect of improving creep resistance is limited, which is not preferable. On the other hand, if the amount of Mn added is larger than the above range, a large amount of coarse crystallized matter is formed and the improvement in creep resistance is saturated, which is inappropriate.

  Cu is also an effective additive element for improving creep resistance. If the amount of Cu added is less than 0.05 to 0.2% by mass, the effect of improving creep resistance is limited, which is not preferable. On the other hand, if the amount of Cu added exceeds the above range, precipitates are formed at the grain boundaries during use at 150 to 270 ° C. after brazing, which is inappropriate because the susceptibility to intergranular corrosion increases.

  Next, the alloy material is rolled to the final thickness. Rolling can be performed by a known method using, for example, DC (Direct Chill) casting, homogenization treatment, hot rolling, and cold rolling. Thereby, an Al-Mn alloy plate is obtained. In cold rolling, annealing at the intermediate plate thickness or the final plate thickness may be appropriately performed. Moreover, the Al-Mn alloy plate may be either an O material that has been finally annealed or an H material that has been processed.

  Next, a solution treatment is performed on the Al—Mn alloy plate under the following conditions. Specifically, it is held at 560 to 620 ° C. for 0.5 to 2000 hours, and then rapidly cooled so that the average cooling rate up to 100 ° C. is 1 ° C./s or more. If the cooling rate is lower than this, precipitation of an intermetallic compound containing Mn occurs during cooling, and the solid solution Mn contributing to creep resistance is reduced, which is inappropriate.

  Here, the reason why the solution treatment temperature and the holding time are within the above ranges will be described below.

  When the solution treatment temperature is lower than 560 ° C., the solid solution of the alloy element components becomes insufficient, which is inappropriate. Further, even when the solution treatment temperature is higher than 620 ° C., the improvement in the effect is saturated, and there is a possibility that harmful effects such as local melting may occur.

  If the holding time is less than 0.5 hours, the solution effect and crystal grain growth are insufficient, which is inappropriate. Moreover, even if the solution treatment is performed for a holding time exceeding 2000 hours, it does not lead to a special performance improvement. Accordingly, the holding time is suitably 0.5 to 2000 hours. In particular, a holding time of 15 hours or longer is particularly desirable because the creep resistance is greatly improved as will be described later.

  The solution treatment can be performed by appropriately selecting a furnace such as an air atmosphere furnace, a non-oxidizing gas atmosphere furnace, or a salt bath furnace. In addition, as a cooling method, a method such as air cooling or water quenching can be appropriately selected. Further, before or after the solution treatment, it is possible to perform processing such as press molding or roll molding of the plate.

  The Al—Mn alloy plate manufactured by the above method is brazed and bonded in combination with other members to form a structure such as a heat exchanger as the most used form. In such a usage pattern, a brazing material made of an Al—Si based alloy is disposed at least at a portion that can be joined. Here, it is preferable in terms of production efficiency that the mating material is a brazing sheet having an Al—Si alloy as a skin material.

  As the brazing method, a so-called nocolok method in which brazing is performed in a furnace using a non-corrosive flux such as a fluoride type is preferable, but the brazing method is not limited thereto. The brazing heating temperature is preferably in the range of 590 to 610 ° C., and the brazing is carried out by being held within this temperature range for 1 to 30 minutes. It is desirable to perform brazing heating cooling at a rate of 1 ° C./s or more.

  According to the manufacturing method of this embodiment mentioned above, the effect of the solid solution strengthening by Mn and Cu increases by performing an appropriate solution treatment. Thereby, the creep resistance of the Al—Mn alloy plate can be improved. Further, the growth of crystal grains during the solution treatment of the present embodiment also contributes to the improvement of creep resistance. In addition, when brazing an Al-Mn alloy plate, heating for a short time at 590 ° C. to 610 ° C. is performed. However, the effective element can be sufficiently dissolved by performing a prior solution treatment. It becomes possible. Moreover, since the manufacturing method of this embodiment does not add the alloy element which reduces brazing properties, such as Mg, favorable brazing property is obtained also when a flux is used.

  In the above-described embodiment, the method for manufacturing the Al—Mn alloy plate has been described. However, the method for producing an aluminum material according to the present invention may be used not only for a plate material but also for an Al—Mn alloy material having various shapes such as a bar material, a wire material, and a pipe material depending on applications. In these cases, various methods according to the shape of the Al—Mn alloy material, such as extrusion and drawing, can be used for cold working up to the final dimension, in addition to rolling.

  Hereinafter, the effect of the present invention will be specifically described in comparison with a comparative example that is out of the scope of the claims.

  First, an Al—Mn alloy having the composition shown in Table 1 was made into an ingot by ordinary DC casting, and hot-rolled after homogenization to give a hot-rolled plate having a thickness of 5 mm. Subsequently, the hot-rolled sheet was further cold-rolled to a thickness of 2 mm, and recrystallized by final annealing to obtain an O-material Al-Mn alloy sheet.

  Next, as shown in Table 2, the Al—Mn alloy plate (O material) was subjected to a solution treatment at 600 ° C. while changing the holding time. The cooling at this time was water quenching, but the cooling rate was 500 ° C./s or more.

  The test piece thus produced was evaluated for creep resistance using a single type creep rupture test apparatus. A test piece having a parallel part of 5 mm and a score of 30 mm was used, the test conditions were 250 ° C., and the load stress was 45 MPa.

Table 3 shows the test results for Examples 1 to 6 and Comparative Examples 1 to 4 processed within the specified range of the present invention. Examples 1 to 4 and Comparative Examples 1 and 2 are examples in which brazing heating is not performed. As shown in Table 3, in Examples 1 to 4, the minimum strain rate was reduced and the break time was increased. That is, the results showing that the creep resistance was improved in the case of Examples 1 to 4 were obtained. Among them, in Examples 1 and 2 in which the retention time of the solution treatment is 15 hours or more, the minimum strain rate is particularly small on the order of 10 ⁻⁶ / s and the breaking time becomes long. The improvement of performance is realized. On the other hand, in Comparative Example 1 in which the solution treatment holding time is short and in Comparative Example 2 in which the solution treatment is not performed, the minimum strain rate is large and the breaking time is short. That is, in Comparative Examples 1 and 2, the creep resistance is insufficient.

  Further, under some solution treatment conditions, the specimens were subjected to brazing heating on the Al-Mn alloy sheet treated according to the present invention and the Al-Mn alloy sheet outside the scope of the present invention. Produced. The manufacturing method is shown below.

  First, as shown in FIG. 1, a brazing structure 12 was formed by brazing a brazing sheet 12 to both ends in the longitudinal direction of an Al—Mn alloy plate 11. The brazing sheet 12 is a clad material whose outer skin is an Al—Si brazing material. The joining part of the Al-Mn alloy plate 11 and the brazing sheet 12 was brazed in nitrogen under the condition that a fluoride-based flux was applied by a known method and kept at 600 ° C for 3 minutes. The cooling after maintaining the brazing temperature was about 1.8 ° C./s. Thereafter, a test piece was collected from the Al—Mn alloy plate 11.

  A creep rupture test similar to the test conditions described above was performed on the test piece after brazing and heating thus produced. As shown in Table 3, Examples 5 and 6 of the present invention are resistant to 250 ° C. even after brazing, compared to Comparative Examples 3 and 4 where brazing is performed for a short time or without solution treatment. The result that the creep property was good was obtained. Moreover, even in the case of the test piece heated by brazing, the creep resistance was particularly good in Example 5 in which the retention time of the solution treatment was 15 hours or longer. The brazing properties were good in both Examples 5 and 6.

It is a perspective view which shows the brazing structure in the Example of this invention.

Explanation of symbols

10 Brazed structure 11 Al-Mn alloy plate 12 Brazing sheet

Claims (1)

Containing Mn: 1.0 to 1.5% by mass, Cu: 0.05 to 0.2% by mass, and regulating Si as impurities to less than 0.6% by mass and Fe to less than 0.7% by mass , A process of cold working the alloy material consisting of Al and inevitable impurities to the final dimensions,
Applying a solution treatment for holding the cold worked alloy material at a temperature of 560 to 620 ° C. for 0.5 to 2000 hours,
A method for producing an aluminum alloy material having excellent creep resistance.

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