JPH0816257B2 - Aluminum alloy brazing sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an Al alloy brazing sheet used for brazing of a drone cup type heat exchanger, which has particularly improved strength, brazing property and pitting corrosion resistance. It is a thing.

[Conventional technology]

For heat exchangers such as automobile oil coolers, evaporators, and intercoolers, Al alloys that have excellent heat conductivity and corrosion resistance, and are lightweight and have good formability, namely JIS 3003 alloy (Cu0.
05-0.2wt%, Mn1.0-1.5wt%, balance Al), JIS 6951 (Si
JIS 4343 alloy (Si6.8 to 8.2wt) with a lower melting point than the core material on one or both sides of the core material such as 0.20 to 0.50wt%, Cu 0.15 to 0.40wt%, Mg 0.4 to 0.8wt%, balance Al) %, Balance Al), JIS 4004
A brazing sheet in which an alloy (Si 9.0 to 10.5 wt%, Mg 1.0 to 2.0 wt%, balance Al) is clad as a brazing material is used.

The structure of the heat exchanger is usually a drone cup type having a laminated structure. This drone cup heat exchanger is the first
As shown in Figures (a) and (b), by press molding, the bottoms drilled at both ends are projected in the same direction to form a cup shape, and a continuous groove between the cups is projected in the same direction as the cup. A unit is formed by stacking the formed tube sheets (1) so that the projecting surfaces face each other outward and facing the concave grooves to each other to form the refrigerant channels (2) and (3).

A plurality of the above units are vertically stacked to provide tank portions (4) and (5) in which flow paths are formed in the stacking direction at both ends of the tube sheet (1), and a corrugate is provided between the stacked units of the tube sheet (1). Processed fins (6)
Placed and brazed.

Vacuum brazing is generally performed for joining assembled parts such as the above drone cup heat exchanger that has many joints between each part, and therefore the brazing sheet used is currently JIS 300 alloy. As a core material, J on both sides of the core material
The IS 4004 alloy brazing material is jointly rolled at a desired clad ratio, then cold-rolled and annealed repeatedly to a desired sheet thickness, and finally annealed.

As shown in Fig. 1 (a) and (b), the tube sheet and the fin material made of pure Al, Al-Mn alloy, etc. are assembled and set in the furnace, and heated to a temperature of about 600 ° C. By melting and flowing the wax, the wax is moved to the contact part of each component, cooled and solidified, and then combined and integrated to manufacture a heat exchanger.

[Problems to be solved by the invention]

The heat exchanger as described above, especially the evaporator, is placed inside the automobile, and the corrosive environment is not bad compared to the radiator and condenser placed on the front grill, but when the air conditioner is used, the outside is always wet, Further, in the salt-damaged areas such as the Middle East, North America and coastal areas, the problem of corrosion is serious even in the above evaporator.

Conventionally, S is used to improve the corrosion resistance against such external corrosion.
Using fin material with n, In, Zn, etc. added as a sacrificial material,
Although pitting corrosion is prevented in the refrigerant passages, the anticorrosion effect of the fins extends only to the vicinity of the joints between the fins and the tube sheet. It was a problem without expecting the corrosion resistance of the sheet itself.

Also, due to the demand for cost reduction and weight reduction of automobile parts in general, thinning of these brazing sheets is required, but in the case of Al-Mn-Cu alloy core brazing sheet, the strength of the annealed material is 11 to 12 Kg / mm. ^When it is increased from ² to 14 to 15 Kg / mm ² or more, it is not possible to maintain the elongation, which is the standard for good formability, at around 30% of the current material, and it has been strongly desired to improve these.

[Means for solving problems]

As a result of various studies in view of this, the present invention has improved the corrosion resistance life of a portion of the heat exchanger that is not protected by the sacrificial fins, and also improved the strength and brazing property, thereby reducing the weight of the heat exchanger aluminum alloy brazing. The developed sheet is Cu 0.3-2.0wt% (hereinafter wt% is simply referred to as%), Mn0.5-
1.5%, Ti0.03 to 0.25%, Cr0.05 to 0.3%, Mg0.05 to 0.50%,
A brazing sheet in which an Al-Si alloy brazing filler metal is clad on one or both sides of an Al alloy core material that contains Fe 0.2% or less and Si 0.2% or less and the balance is Al and ordinary impurities. It is characterized in that the crystal grain size of is 50 to 150 μm.

[Work]

The reason why the alloy composition of the core material is limited as described above in the present invention is as follows.

The addition of Cu enhances the strength and further makes the pitting potential of the core material noble. Therefore, the Cu content was limited to 0.3 to 2.0%.
If it is less than 0.3%, the above effect is small, and if it exceeds 2.0%, the elongation is lowered and the formability is impaired. The addition of Mn is to further increase the strength, and the reason for limiting the Mn content to 0.5 to 1.5% is that the effect is small if it is less than 0.5%, and if it exceeds 1.5%, the elongation decreases and the formability deteriorates. Because.
The addition of Ti is to improve the pitting corrosion resistance.
The reason why the content is limited to 0.03 to 0.25% is that if the content is less than 0.03%, the above effect does not occur, and if the content exceeds 0.25%, the workability deteriorates, which causes a problem in manufacturing. The addition of Cr is for improving the strength, and the Cr content is limited to 0.05 to 0.3%. If the content of Cr is less than 0.05%, the above effect does not occur, and if it exceeds 0.30%, the workability decreases, which is a problem in manufacturing. Because. The addition of Mg is to improve the strength, and the reason why the Mg content is limited to 0.05 to 0.5% is that the above effect does not occur if it is less than 0.05%, and if it exceeds 0.50%, the brazing filler metal after clad diffuses into the core material. Is increased and the brazing property is hindered. The usual Fe content of 0.2% or less and the Si content of 0.2% or less are used because the compound of these elements and Al or Mn acts as a cathode and deteriorates the corrosion resistance.

Furthermore, it is Cu and
This is because it suppresses the decrease in formability due to the decrease in elongation due to the addition of Mn.Also, after brazing, a brazing material with an appropriate thickness remains on the surface of the brazing sheet, which ensures the plate thickness and the potential difference from the core material. This is because the brazing filler metal layer acts as a sacrificial anode and can improve the corrosion resistance. The grain size is limited to 50 to 150 μm. When the brazing filler metal layer is less than 50 μm, the diffusion of the brazing filler metal into the core material becomes large at the time of brazing. This is because the corrosion resistance deteriorates due to buckling and reduction in core thickness. Again 150
This is because when the thickness exceeds μm, the brazing material locally penetrates deeply in the core direction during brazing, and the brazing material remaining on the surface of the core material decreases, that is, the brazing material easily flows, thereby lowering corrosion resistance. The crystal grain size can be set in the range of 50 to 150 μm by soaking the core material in the range of 560 to 610 ° C.

〔Example〕

Alloys having the compositions shown in Table 1 were melted and cast by a conventional method,
After producing a 60 × 180 × 180 mm ingot, soaking was carried out at 600 ° C. for 3 hours, and 5 mm on each side was chamfered to obtain a core material having a thickness of 50 mm. Next is JIS 4004 alloy (Si 10%, Mg 1.5%, balance A
l) was melted and cast to produce an ingot of 60 × 180 × 180 mm, both sides were ground, and hot rolled at a temperature of 500 ° C. to obtain a skin material having a plate thickness of 10.5 mm. The skin material is put on both sides of the core material, heated at 500 ° C, hot-rolled to a clad material with a thickness of 5 mm, further cold-rolled, and finally annealed at 360 ° C for 2 hours to obtain a sheet thickness.
A 0.6 mm brazing sheet was prepared.

The results of measuring the crystal grain size of the core material of the brazing sheet thus produced are also shown in Table 1. Comparative materials No. 8 and No. 9 in Table 1 are brazing sheets having crystal grain sizes of 40 μm and 170 μm prepared by changing the soaking temperature of the core material of the present invention material No. 1.

Strength and elongation of the brazing sheets shown in Table 1 were measured by a tensile tester to evaluate the mechanical properties, and the moldability was determined by the Erichsen test according to the JIS Z 2247A method. Overhang molding was performed with a head punch, and the molding height when cracks were formed was measured and evaluated.

Furthermore, regarding the brazing sheet shown in Table 1, 60 ×
The one cut to 110 mm is hung on a jig and the vacuum degree is 5 × 10 ^-5 t.
Vacuum brazing was performed by holding at a temperature of 600 ° C. for 3 minutes with an orr. Seal the back and end faces of this brazed product to 50 x
The 100 mm portion was subjected to a cass test and the maximum pit depth after 200 hours was measured to evaluate the corrosion resistance. For the measurement of the pitting depth, select 10 deep points within the same brazed product, find the depth by the depth of focus method with an optical microscope, and select the deepest of these to determine the cross section of the part. The pitting depth was determined by cutting out and polishing.

Then, the brazing sheet (7) of the brazed product is cut out at a right angle in the cross section as shown in FIG. 2, and the thickness of the residual core material (9) excluding the brazing material diffusion layer (8), that is, the residual core material thickness. By measuring (l), the diffusion state of the brazing material into the core material was ranked into the following three stages, and the brazing property was evaluated.

Extremely large diffusion to core material ... Large Conventional diffusion to core material ... Medium Extremely small diffusion to core material ... Small Further measure the total thickness of brazing sheet after brazing and measure its size. The amount of residual brazing filler metal that acts as a sacrificial layer against corrosion of the core material was evaluated by.

The above results show that the conventional JIS 3003 alloy (Cu0.15%, Mn1.0
%, Ti0.01%, Cr0.01%, Mg0.01%, Fe0.5%, Si0.25%, balance Al) and JIS 3004 alloy (Mn1.1%, Mg0.90%, Cu0.20%,
Mechanical properties, corrosion resistance, and brazing sheet with JIS 0.014, Cr 0.01%, Fe 0,5%, Si 0.25%, balance Al) as core material and JIS 4004 alloy similar to the above It is shown in Table 1 together with the test results of the brazing property and the residual amount of the brazing material.

In addition, if the Cu content exceeds 2%, the Mn content exceeds 1.5%, the Ti content exceeds 0.25%, and the Cr content exceeds 0.3%, the workability is extremely poor, and as a brazing sheet Since it could not be manufactured, the evaluation test was impossible.

As can be seen from Table 1, the materials of the present invention (No. 1 to No. 7) all have a very small maximum pitting depth and good corrosion resistance, and the diffusion of the brazing material into the core material is small and the brazing is good. It turns out that it has sex. Furthermore, the materials of the present invention are all 14.5 Kg
It has a strength of / mm ² or more and an Erichsen value of 9.3 mm or more, which is equivalent to conventional materials (No.18, No.19), there is no problem in practical formability, and after brazing The total thickness, that is, the residual amount of the brazing filler metal is not so different.

On the other hand, if the alloy composition of the core material is the same as that of the material of the present invention (No. 1), the comparative materials (No. 8 and No. 9) whose grain size is not 50 to 150 μm have a large maximum pitting depth, and It can be seen that the brazing property is also poor.

Of the additive elements, those with a Cu content of less than 0.3% (No.
No. 10) has poor corrosion resistance and Mn content of less than 0.5% (No.
11) and those with a Mg content of less than 0.05% (No. 12) have low strength, those with a Mg content of more than 0.5% (No. 13) have poor corrosion resistance and brazing material, and have a Fe content of 0.2%. More than (N
o.14), Si content exceeding 0.2% (No.15) and Ti
Corrosion resistance of all those with a content of less than 0.03% (No.17) is drastically reduced, and the content of Cr is less than 0.05% (No.1).
It can be seen that 6) has low strength.

〔The invention's effect〕

As described above, according to the present invention, the corrosion resistance of the brazing sheet used as the material of the heat exchanger can be remarkably improved, the strength can be further improved without impairing the formability, and the weight of the member can be reduced. It has a remarkable effect.

[Brief description of drawings]

Fig. 1 (a) and (b) show the Delon cup type heat exchanger, (a) is a perspective view, (b) is a side view, and Fig. 2 is the residual core material thickness of the brazing sheet after brazing. FIG. 1 …… Tube sheet 2,3 …… Refrigerant flow path 4,5 …… Tank section 6 …… Fin 7 …… Brazing sheet 8 …… Brazed material diffusion layer 9 …… Residual core material l …… Residual core thickness

Continuation of the front page (56) Reference JP-A-59-205445 (JP, A) JP-A-55-107748 (JP, A) JP-A 61-104042 (JP, A) JP-A 61-89498 (JP , A) JP-A-56-136949 (JP, A) JP-A-62-230494 (JP, A)

Claims (1)

[Claims] 1. Cu 0.3 to 2.0 wt%, Mn 0.5 to 1.5 wt%, Ti 0.03 to
0.25wt%, Cr0.05〜0.3wt%, Mg0.05〜0.50wt%, Fe0.2wt
% Or less than 0.2 wt% of Si, and the grain size of the core material in the brazing sheet in which the Al-Si alloy brazing material is clad on one or both sides of the Al alloy core material consisting of the balance Al and ordinary impurities Aluminum alloy brazing sheet characterized by a thickness of 50 to 150 μm.