JPH0642994B2 - Aluminum brazing sheet for drone cup heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an aluminum brazing sheet used in a drone cup type heat exchanger, and in particular, has improved brazing property.

[Conventional technology]

For oil coolers, evaporators, intercoolers and the like for automobiles, a drone cup type heat exchanger using an A alloy, which is excellent in thermal conductivity and corrosion resistance, and is lightweight and has good formability, is used. Such a drone cup type heat exchanger is constructed such that the flow path (2), (3) is formed in the longitudinal direction of the tube sheet (1) press-molded as shown in Fig. 1 (a) (b). The tube sheet (1) is made up of one unit which is opposed to each other and is vertically laminated to form the channels (4) and (5) in the vertical direction at both ends of the tube sheet (1). It is made by placing corrugated fins (6) in between and brazing.

Vacuum brazing is generally used for joining assembled parts such as the above heat exchanger, which have many joints between various parts, and therefore the tube sheet has a skin material on one or both sides of the core material. As the brazing material, a brazing sheet clad with a brazing material is used.

As a brazing sheet, A-Mn type, A-Mn
-Mg-based or A-Si-Mg-Cu-based alloy core material on one or both sides of A-Si-based, A-Si-Mg
System, A-Si-Bi system, A-Si-Be system or A
-Si-Bi-Be-based alloy brazing filler metal is used as a skin material, and is rolled together with a desired clad ratio, and then cold rolling and annealing are repeated to obtain a desired sheet thickness, and final annealing is performed to produce a sheet. Has been.

Further, since it is desired that the fin material is hard during fin formation, a work hardening material made of an A-Mn-based alloy, an A-Mn-Mg-based alloy or an A-Si-Mg-Cu-based alloy,
That is, H14 material or the like is used.

The above fins and tube sheet are assembled as shown in Fig. 1 (a) and (b), set in a furnace, and heated to a temperature of about 600 ° C to melt and flow the brazing filler metal to form an assembled product. The brazing is moved to the contact area of each other, cooled, solidified and joined to complete the integration.

[Problems to be solved by the invention]

As described above, the joint strength of the part joined by brazing is
The moved brazing filler metal forms a pool of brazing filler metal at the joint and largely depends on the amount of brazing filler metal in the solidified portion (hereinafter referred to as fillet). In order to increase the size of the fillet and improve the joint strength, it is important to quickly move the brazing filler metal to the joint when heat is applied to the brazing filler metal, and to prevent the brazing filler metal from flowing and diffusing outside the joint. Is. As the former method, adjustment of the amount of Si in the brazing material or Bi, B
Although it is clear that the addition of e etc. is effective,
On the other hand, the latter phenomenon in which the brazing material flows and spreads outside the joint is that the brazing material flows on the surface of the core material when the brazing heat is applied and gathers in the joint part, but part of it is in the core of the part other than the joint part. By diffusing inward from the material surface along the grain boundaries,
Since the brazing filler metal is consumed by diffusion, the fillet may not be formed sufficiently large, and the brazing filler metal may corrode the diffused core material surface, leading to a reduction in wall thickness. As a result, the pressure resistance of the core material is reduced, which is a problem.

[Means for solving problems]

As a result of various studies in view of this, the present inventor has found that, in the vicinity of the brazing portion of the tube sheet of the heat exchanger, the extent to which the brazing material diffuses into the core material is small in the cold working rate by press molding of the brazing sheet. As a result of further study, we found that the aluminum brazing sheet for a drone cup heat exchanger that forms a large fillet without diffusing the brazing filler metal into the core material when the brazing heat is applied. Alternatively, in an aluminum brazing sheet in which an A-Si alloy is clad as a brazing material on one or both sides of a core material of an A alloy, a cold working rate of 3
It is characterized in that the grain size of the core material is 66 μm or less at ˜10%.

[Action]

When press-molding a brazing sheet, the smaller the grain size of the core material, the better the moldability. However, the crystal grain size of the core material after cold working is set to 66 μm or less because it acts together with an appropriate strain applied by cold working, and quickly causes recrystallization of the core material when the brazing heat is applied, and This is because it has the effect of increasing the size of the recrystallized grains, and this reduces the amount of molten wax that diffuses into the core material. On the contrary, when the crystal grain size exceeds 66 μm, the formability is remarkably reduced,
Further, the recrystallization of the core material is delayed when the brazing material is heated, and the diffusion of the brazing material into the core material becomes large.

In addition, the reason why the cold working rate is set to 3 to 10% as the above appropriate strain is 0 to 30% for the brazing sheet during press forming.
However, since the amount of strain as the driving energy for promptly causing recrystallization by the brazing heat is insufficient in the region of low working rate, by adding strain in advance before press molding, This is to make up for this shortage. However, if the cold working rate is less than 3%, the brazing filler metal diffuses into the core material at a low strained portion during press forming, and if it exceeds 10%, the elongation becomes small and the formability is remarkably deteriorated. .

〔Example〕

JIS 3003 alloy (Mn 1.2%, Cu 0.12%, balance A) is melted and cast by a conventional method to produce an ingot of 60 × 180 × 180 mm, and then chamfered by 5 mm on each side and a core with a thickness of 50 mm It was made of wood. Next, a JIS 4004 alloy (Si 10%, Mg 1.5%, balance A) was cast in the same manner as above, after chamfering 5 mm on each side, hot rolling was performed at 500 ° C, and a skin material with a thickness of 10.7 mm was obtained. did. The core material having a thickness of 50 mm was subjected to soaking for 3 hours at various temperatures between 560 and 620 ° C, and the grain size after the final annealing was variously changed. A clad material having a thickness of 5 mm was obtained by clad a skin material on both sides of these core materials and hot rolling at 500 ° C. These clad materials are cold-rolled and intermediate-annealed to obtain a plate thickness of 0.60 to 0.71.
mm sheets, and then these sheets are subjected to final annealing at a temperature of 360 ° C. for 2 hours, and then, as shown in Table 1, final cold rolling is performed at a 0% to 15% working rate to obtain all sheets. A brazing sheet with a thickness of 0.6 mm was finished and used as 13 types of test materials. The crystal grain size of the core material of the obtained brazing sheet was 10 to 110 μm as shown in Table 1.

The mechanical properties of the above test material are tensile strength, elongation, and a JIS X 2247A method of 90 × 90 mm test material sheet and diameter 20
The Erichsen value was investigated using a punch of mm, and the brazing property was evaluated by the following method. A cup as shown in Fig. 2 (a) and (b) was formed from each test material, and 6 cups of the same type were alternately laminated as shown in Fig. 3 to form a core. After fixing with, vacuum degree 5
Vacuum brazing was performed at a temperature of 600 ° C. for 3 minutes at × 10 ^-5 torr. 10 cores were made using the same type of cup, and the brazed cores were cut in the longitudinal direction. As shown in Fig. 4, the fillet lengths of the flange joints were 6 places per core. The average length was determined by measurement, and the brazing property was evaluated by the average length of all 10 cores.

The above results are shown in Table 1 together with the test results of the mechanical performance and brazing property of the conventional brazing sheet not subjected to the final cold rolling.

As is clear from Table 1, the materials of the present invention (NO.1 to NO.7) having a cold working rate of 3 to 10% and a grain size of 66 μm or less are the conventional materials (NO.14, NO.15). It can be seen that the brazability is excellent without lowering the formability and mechanical performance. On the other hand, if the final cold rolling rate exceeds 10% (NO.11 and NO.13), the formability is remarkably poor, and if the final cold rolling rate is less than 3% (NO.10 and NO.12). ) And the final cold rolling ratio within 3 to 10%, the grain size exceeding 66 μm (NO. 8 and NO. 9) is inferior in brazing property or formability.

〔The invention's effect〕

As described above, by using the brazing sheet according to the present invention, the brazing filler metal can be efficiently flowed to the joint portion, and since the diffusion of the brazing filler metal is small, the seat of the laminated cup portion in brazing of the drone cup heat exchanger is reduced. Since the bending strength is increased and the dimensional change before and after brazing is small, the dimensional accuracy of the laminated cup is improved, which is an industrially significant effect.

[Brief description of drawings]

1 (a) and 1 (b) show a Delon cup type heat exchanger, (a) is a perspective view, (b) is a side view, and FIG. 2 (a).
(B) shows the molding cup used in the brazing test, (A) is a plan view, (B) is a side sectional view, FIG. 3 is a side sectional view showing the state of the sample in the brazing test, FIG. 4 is an explanatory view showing the fillet length of the joint portion in the brazing test. 1 ... Tube sheet 2, 3 ... Longitudinal flow path 4, 5 ... Vertical flow path 6 ... Fin 7 ... Brazing test cup a ... Exhaust hole b ... Joint fillet length

Claims (1)

[Claims] 1. An aluminum brazing sheet in which an A-Si alloy is clad as a brazing material on one or both sides of a core material of A or A alloy, and a cold working ratio of 3 to 10%.
An aluminum brazing sheet for a drone cup type heat exchanger, characterized in that the grain size of the core material is 66 μm or less.