JPH0375328A - Brazing sheet for drawn cup-type heat exchanger and its manufacture - Google Patents

Abstract

PURPOSE:To suppress erosion in a low worked part of the brazing sheet and to improve its corrosion resistance by subjecting aluminum stock to cold rolling, specifying the heating rate in final annealing and refining its grain size. CONSTITUTION:An Al alloy of Al-Mn series or the like is regulated as a core material and both faces are clad with brazing filler materials, which undergoes the stages of hot rolling, cold rolling and final annealing to manufacture the brazing sheet for a drawn cup-type heat exchanger. At this time, the final annealing is executed at a heating rate of >=100 deg.C/min to refine the average grain size to 15 to 30 mum. In this way, erosion in a tank part of the heat exchanger is effectively suppressed to obtain the effect of improving its corrosion resistance and workability. As the core material, an alloy contg., by weight, 0.3 to 1.5% Mn and <=0.3% Fe as well as satisfying >=2.5 Mn/Fe ratio, if required, contg. one or more kinds among <=0.06% Mg, <=0.5% Cu and <=0.3% Cr and the balance Al is preferably used.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a brazing sheet used as a plate material for a dragon cup type heat exchanger, and in particular, it has excellent erosion resistance even in processed parts and can significantly improve corrosion resistance, so it can be made thinner and lighter. The present invention relates to a possible brazing sheet and its manufacturing method. (Prior Art) Generally, an evaporator for a car cooler is composed of a plate material made of a brazing sheet and a corrugated fin material, and is assembled by vacuum brazing. In heat exchangers such as evaporators, various corrosion resistance improvement measures are being considered to prevent penetrating corrosion of tubes and tanks, such as improving the aluminum alloy composition of the core material and using fin materials to act as a sacrificial anode. . Specifically, ■ Blazing Sea 1 - Principles of core material composition, for example, Cu,
Addition of Cr etc., regulation of Fe. ■Blazing Sea 1 - Principles of core material structure, such as soaking conditions and addition of Ti and Zr. ■Sacrificial anode corrosion protection using fin materials, such as the use of Sn-added fin materials. However, the Dron cup heat exchanger is subjected to cold working in the range of 0 to 20% during cup forming, and especially
Erosion is significant in the low-processed area that has been processed by ~10%, and the corrosion resistance in that area is significantly reduced. Therefore, it is difficult to reduce the thickness and weight of the Dron cup heat exchanger by using only the above corrosion resistance improvement measures. (Problems to be Solved by the Invention) As described above, with the conventional techniques, it is difficult to effectively prevent erosion in low-machined parts. Even if a material with excellent corrosion resistance could be developed, erosion could not be suppressed and it was extremely difficult to improve the corrosion resistance as a heat exchanger. The present invention eliminates the drawbacks of the prior art described above, and provides a brazing sheet for a doron cup type heat exchanger that can effectively suppress erosion in processed parts, especially low processed parts, and improve corrosion resistance. The purpose is to provide a manufacturing method. (Means for Solving the Problems) In order to achieve the above object, the inventors of the present invention have conducted extensive research in order to find a brazing seal that has excellent erosion resistance without impeding workability. First, in the Dron cup heat exchanger, as mentioned above, there is significant erosion in the areas that have undergone low processing during cup forming.When we investigated the cause of this, we found that the recrystallization of the core material occurred during the waxing process in the low processing areas. It has been found that as a result of the subgrain remaining without completion, erosion is promoted. If the amount of X lotion is significant, the remaining core material thickness will decrease,
In order to prevent the remaining subgrains that would reduce corrosion resistance, it is most effective to apply processing distortion of a certain value or more to the brazing seam. Sexuality decreases. In addition, the remaining subgrain during brazing varies depending on the core material composition and manufacturing conditions, and the larger the amount of solid solution of the transition element, the more recrystallization is suppressed and the subgrain remains more easily. Al-M is often used as a core material for brazing sheets.
In the case of an n-based alloy, the composition and manufacturing conditions that control the amount of Mn solid solution are preferred, and addition of Fe and high-temperature soaking at 570° C. or higher are preferred. However, although the addition of Fe is effective in promoting recrystallization, it impairs corrosion resistance. Therefore, the present inventor conducted various studies on ways to effectively suppress erosion by promoting recrystallization during brazing of the brazing seam 1-. Conventionally, a method of coarsening the crystal grain size of the core material of the aluminum brazing sheet was proposed as a method of suppressing erosion, but recrystallization is difficult in low-machined parts such as the Dron cup heat exchanger. corrosion was delayed, and erosion was significant, causing a decrease in corrosion resistance. On the other hand, it is possible to refine the crystal grain size of the core material of aluminum material plating sheet -1. It has been discovered that erosion in low-machined areas can be suppressed without reducing workability, and the present invention has been developed based on this discovery. That is, the brazing sheet for a doron cup type heat exchanger according to the present invention is characterized in that the average crystal grain size of the core material of the aluminum material brazing sheet before molding is 15 to 30 μm. In addition, the manufacturing method is such that when manufacturing the core material of the aluminum material brazing sheet before forming, after cold rolling, final annealing is performed at a heating rate of 100°C/min or more.
It is characterized by obtaining an average crystal grain size of 30 μm. The present invention will be explained in more detail below. (Function) The reason why the average crystal grain size of the core material of the brazing sheet material before the forming process of the Dron cup type heat exchanger is specified to be in the range of 15 to 30 μm is because brazing sometimes promotes recrystallization, as described above. In particular, this is to suppress erosion of the tank portion (particularly the low-machined portion), which greatly affects corrosion resistance. The finer the crystal grain size, the more likely recrystallization will occur, but on the other hand, erosion will be promoted in non-processed areas, leading to a decrease in brazing properties. Therefore, brazing is regulated to a range of 15 to 30 μm as an average crystal grain size that can suppress erosion in areas important for corrosion resistance without impairing properties. The method for obtaining the average crystal grain size of the above size is as follows. It is most effective to increase the heating rate during final annealing of the aluminum brazing sheet core material. As an industrial means, annealing using a continuous annealing line is effective. In this case, if the heating rate during annealing is 100° C./min or more, the crystal grain size of the core material normally used for brazing sheets can be controlled within the range of 15 to 30 μm. Other annealing conditions are not particularly limited. For example, the heating temperature is 350 to 540°C, the holding time is 1 second to 120 seconds, and the cooling rate is 20 to 200℃.The above conditions for the core material of an aluminum brazing sheet are 1. However, the effect is particularly remarkable when applied to Al-Mn alloys, which tend to have sub-grain residues and are susceptible to deterioration in corrosion resistance due to two lotions. Of course, it goes without saying that the present invention can also be applied to Al-Mg-8i core materials in which erosion due to residual subgrains does not pose much of a problem. Next, a preferred component composition when applied to an An-Mn alloy will be described. In general, although Al-Mn alloys have very good corrosion resistance in an unprocessed state, they often suffer from erosion due to delayed recrystallization in lightly processed areas, resulting in a significant decrease in corrosion resistance. In this regard, it contains Mn: 0.3 to 1.5% and Fe: 0.3% or less, and the Mn/Fe ratio is 2.5 or more, and if necessary, Mg: 0.6%. Below, Cu: 0
, 5% or less and Cr: 0, 1 type or 2 of 3% or less
A having a composition in which the remainder is substantially composed of Al.
It has been found that an l-Mn alloy can effectively solve these problems. The reason for limiting the components of this Afl-Mn alloy is as follows. First, Mn is generally used as an alloy additive element for aluminum alloys for brazing sheet core materials, and is a component that is effective in improving high temperature strength and post-brazing strength. On the other hand, as the amount of solid solution increases, recrystallization is suppressed and subgrains are likely to remain, so care must be taken to ensure coexistence with Fe and optimization of manufacturing conditions. If the Mn content is less than 0.3%, brazing is insufficient for improving properties and strength.
Moreover, if the Mn content exceeds 1.5%, the effect is saturated and this is not preferable because it reduces workability and promotes the persistence of subgrains, so the Mn content is set in the range of 0.3 to 1.5%. Fa is effective in suppressing the amount of Mn solid solution, promoting recrystallization, and improving moldability by making the grain size finer.
On the other hand, it is a component that causes a decrease in corrosion resistance. It is preferable to limit Fe to 0.3% or less as a range that is effective in suppressing the remaining subgrain and improving workability and does not significantly reduce corrosion resistance. However, the Mn/Fe ratio is extremely important for the corrosion resistance of the brazing sheet, and if the Mn/Fe ratio is 2.5 or more,
Excellent corrosion resistance can be obtained. However, on the other hand, recrystallization is suppressed, resulting in erosion, but by making the crystal grains finer as described above, 20-erosion control becomes possible. Among the optionally added components, Mg is effective in improving strength and workability by refining crystal grains, but it also promotes the diffusion of Si and promotes the formation of two lotions. It should be 0.6% or less. In addition, Cu and Cr are effective in improving strength, shifting the core material potential, and further improving corrosion resistance through potential balance. However, C1
, 1 exceeds 0.5%, the corrosion resistance of the fillet portion decreases, so the amount of Cu added is limited to 05% or less. In addition, if Cr is contained in excess of 0.3%, it will form a giant compound and cause a decrease in workability, so the amount of Cr added should be 0.3%.
Click below. It goes without saying that the brazing material used to clad the core material of the material brazing seal l- can be the conventionally used Al-gold alloy (eg, 4004 alloy) (7
There are no particular restrictions on the cladding rate or brazing conditions. Examples of the present invention are shown below. (Example) An aluminum alloy having the composition shown in Table 1 was used as the core material, 4004 brazing filler metal was applied on both sides at 10% of each plate thickness, and the process of hot rolling → cold rolling → final annealing was carried out by a conventional method to achieve a 0. 6+++
An aluminum alloy brazing sheet 1 with a thickness of m was manufactured. However, the final annealing was performed under various conditions shown in the first table. The average crystal grain size of the obtained Blazing Sea 1-core material is also listed in Table 1. In addition, Table 2 shows the results of investigations regarding workability, erosion resistance, and corrosion resistance in the following manner. The processability of the ball-free hat was evaluated by determining the limit overhang height of the obtained Nosing Sea 1 by Erichsen test, and by the overhang processability. Erosion resistance The Nosing Sheet 1 with the obtained erosion resistance is processed into the shape shown in Figure 1, eight pieces are combined, and the Cera 1 is molded into the shape not shown in Figure 2.
- For this brazing, the test piece is 5 x J,, O"-'
It was heated at 595° C. x 3 ml in a vacuum of Torr. Erosion resistance was evaluated by measuring the thickness of the remaining core material after brazing. Brazing under the above conditions tt +, brazing sea-I
A CASS test was conducted for ・, and the corrosion resistance was evaluated based on the test time until penetrating corrosion occurred. As is clear from Table 2, all of the five invention materials. Brazing that uses 3003 alloy as a core material, which has excellent erosion resistance while maintaining good workability, and has been widely used as a play material in Dron cup heat exchangers. It shows better erosion resistance than sheet O material. In addition, the material of the present invention has a conventional process (heating rate D in Table 1)
Compared to a brazing sheet made of aluminum material with the same composition, the tank part (first part), which has the greatest effect on corrosion resistance,
- The decrease in core material thickness due to erosion in Figure 8) is extremely slight. Of course, the corrosion resistance of the material of the present invention is significantly improved compared to conventional materials and materials of the same composition without grain refinement.

[Left below]

(Effects of the Invention) As detailed above, according to the present invention, the crystal grains of the aluminum core material of the brazing sheet for a dragon cup type heat exchanger are refined and regulated within a specific range, so corrosion resistance is the most important issue. Erosion of the tank portion of the Dron cup heat exchanger is effectively suppressed, and the corrosion resistance of the heat exchanger is greatly improved. In addition, since the effect of improving workability is also obtained, even when an Afl-Mn alloy is used for the core material, Fe can be reduced and deterioration of corrosion resistance can be suppressed. Therefore, when applied to applications where there is a strong need for thinner walls and lighter weights, such as heat exchangers for automobiles, the effect is remarkable.

[Brief explanation of drawings]

FIG. 1 is an explanatory view showing the shape of the Nosing Seat after molding, and FIG. 2 is a view showing the shape and dimensions of the test piece for brazing.

Claims (4)

[Claims] (1) A brazing sheet for a doron cup type heat exchanger, characterized in that the average crystal grain size of the core material of the brazing sheet made of an aluminum material is 15 to 30 μm before forming. (2) The brazing sheet for a dragon cup type heat exchanger according to claim 1, wherein the core material is an Al-Mn alloy. (3) As the core material, in weight% (the same applies hereinafter), Mn
: 0.3 to 1.5% and Fe: 0.3% or less, and the Mn/Fe ratio is 2.5 or more, and if necessary, Mg: 0.6% or less, Cu: 0. .5% or less and Cr:
The brazing sheet for a doron cup type heat exchanger according to claim 1 or 2, wherein an alloy containing 0.3% or less of one kind or two or more kinds, the remainder being substantially Al, is used. (4) When manufacturing the aluminum brazing sheet core material before forming, after cold rolling, final annealing is performed at a heating rate of 100°C/min or higher to obtain an average crystal grain size of 15 to 30 μm. A method for manufacturing a brazing sheet for a doron cup type heat exchanger.