JPH038569A - Production of heat exchanger made of aluminum - Google Patents

Abstract

PURPOSE:To produce the thin heat exchanger having high strength by increasing the cooling rate after brazing of a brazing sheet formed by using a specifically composed alloy as a core material and cladding an Al alloy brazing filler metal thereon. CONSTITUTION:The core material of the brazing sheet 1 is composed of the alloy which contains, by weight, 0.4 to 1.2% Si, 0.15 to 1.0% Fe, 0.4 to 1.0% Cu, 0.5 to 1.2% Mn, 0.05 to 0.8% Mg, contains further one or >=2 kinds of 0.001 to 0.5% Cr, 0. 001 to 0.3% Zr, 0.001 to 1.5% Hf, 0.001 to 0.5% Ti, and 0.0001 to 0.1% B within these ranges, and consists of the balance Al and unavoid able impurities. The heat exchanger is assembled by using the brazing sheet 1 formed by cladding the Al alloy brazing filler metal contg. >=0.5% Si on one or both surfaces of such core material. After the heat exchanger is heated to and held at the brazing temp., the heat exchanger is cooled at >=150 deg.C/min cooling rate down to 500 to 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing an aluminum heat exchanger, and in particular improves the room temperature strength after brazing.

[Conventional technology]

In general, many aluminum heat exchangers, especially automobile heat exchangers such as radiators, heaters, oil coolers, and air conditioner evaporators and condensers, are assembled by the brazing method.

These heat exchangers, as shown in Figure 2, combine plate moldings f4) and f4') to form a refrigerant passage (5), and fins (6) are installed between the passages (5). For Dron cup type evaporators and oil coolers, 3
A brazing sheet is used in which the core material is a 003 series alloy and the surface thereof is clad with an Al alloy brazing material. Also, as shown in Figure 3, there are fins (6) between the tubes (7).
, install seat plates (8) on both ends of the tube (7),
In a radiator in which a resin tank (10) is attached to the seat plate (8) via a backing (9), the seat plate and tube are made of 3003 series alloy as a core material, and one side of the inner side is made of 3003 series alloy.
A brazing sheet is used in which a sacrificial anode layer such as 70 alloy or 7072 alloy is clad, and the opposite side is clad with an Al alloy brazing material.

[Problem to be solved by the invention]

In recent years, there has been a demand for thinner heat exchanger members in order to reduce the weight and cost of heat exchangers.

However, conventionally used brazing sheets having a core material such as 3003 alloy have low strength after brazing and heating, making it difficult to reduce the thickness. Therefore, in order to maintain the strength of the heat exchanger, attempts have been made to develop various high-strength alloys, and high-strength alloys such as heat-treated alloys have been proposed, but none of them can improve the strength under the current brazing conditions. There is a limit. In addition, if the cooling rate is slow from the viewpoint of corrosion resistance, there is a problem in that additive elements precipitate at grain boundaries, increasing the occurrence of intergranular corrosion.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has found that the strength can be improved by increasing the cooling rate after brazing.As a result of further studies, the present invention has made it possible to manufacture a high-strength, thin-walled heat exchanger. A method for manufacturing high-strength aluminum heat exchangers has been developed.

That is, one of the aspects of the present invention is Si 0.4 to 1,211% (hereinafter wt% is abbreviated as %), Fe 0.15 to 1.0
%Cu0.4-1.0%, Mn0.5-1.2%, M
g0.05-0.8%, and further contains Cr 0.00[~
0.5%.

Zr 0.001~0.3%, Hf0.001~
1.5%.

T i 0.001~0.5%, Bo, 0001~
A/gold alloy material containing 5% or more of Si on one or both sides of which the core material is an alloy consisting of one or two or more of the above within the range of 0.01% and the remainder is \a and unavoidable impurities. The cratted brazing sheet is used as a heat exchanger member to assemble the heat exchanger, and after heating and maintaining it at the brazing temperature,
It is characterized by cooling from 00°C to 200°C at a rate of 150°C/min or more.

Another aspect of the present invention is Si0.4 to 12% Fe
0.15-1.0%, Cu0.4-1.0%, Mn
0.5-1.2%, Mg 0.05-08%, further Cr 0.001-0.5%, Z r0.001-
0.3%.

Hf 0.001-15%, Ti 0.001-0.5%
, B0.000+-0.1%, and the balance is Al and unavoidable impurities, and the core material is an alloy containing 5% or more of Si on one side. A brazing sheet clad with Al alloy skin material having a potential 50 mV or more more base than the core material on the opposite side is used as a heat exchanger member, and the heat exchanger is assembled, and after heating and holding at the brazing temperature. , 500℃ to 200℃
It is characterized by cooling at a rate of 1508 C/min or more.

[Effect]

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

Si forms a solid solution in the matrix during brazing heating, improves strength, and also forms fine Mg25 with Mg during cooling after brazing heating and when left at room temperature after cooling.
i is precipitated to improve material strength. However, the S1 content was limited to 0.4 to 1.2% because if it is less than 0.4%, the strength after brazing will not be sufficient, and if it exceeds 1.2%, the solidus temperature will be low. This is because there is a risk of melting during brazing heating.

Fe refines the crystal grains of the core material and improves formability. However, the reason why the Fe content is limited to 0.15 to 1.0% is that if it is less than 0.15%, the effect will not be sufficient, and if it exceeds 1.0%, the corrosion resistance of the material will decrease.

Cu forms Al-Cu-based and Al-Cu-Mg-based fine precipitates, which contributes to improving the strength after brazing heating, and also increases the potential of the material to improve corrosion resistance. However, the reason why the Cu content was limited to 0.4% to 1.0% was 0.4%.
If the content is less than 1.0%, the effect will not be sufficient, and if it exceeds 1.0%, the moldability will deteriorate and there is a risk of melting during brazing heating.

Although Mn improves strength, its content should be reduced from 0.5 to 1.
The reason why it is limited to 2% is that if it is less than 0.5%, the effect is not sufficient, and if it exceeds 1.2%, a huge intermetallic compound is generated during casting, which reduces the ductility of the material.

Mg is solid dissolved in Matri Soxu by brazing heating,
The strength is improved, and the strength is further improved by forming fine precipitates of Mg2Si together with Si during cooling after brazing heating and when left at room temperature after cooling. However, the Mg content was reduced to 0.
The reason why the content is limited to 0.05 to 0.8% is because the effect is insufficient if it is less than 0.05% (and if it exceeds 0.8%, the brazing properties are reduced).

Cr, Zr, Hf, Ti, and B make the composition of the material uniform,
It has the effect of improving material strength, and also improves corrosion resistance by relaxing the potential difference around grain boundaries due to the precipitation of insoluble compounds. However, Cr 0.001-0.5%, Z
r0.001~O13%Hf0.001~1.5%,
T0.001~0.5%, B0.0001~0.1%
If the lower limit is less than the lower limit, the effect will not be sufficient, and if the upper limit is exceeded, coarse intermetallic compounds will be formed during casting, and the ductility of the core material will be reduced. This is to reduce the

The present invention provides Si on at least one side of the core material having the above composition.
Clad with Al alloy brazing filler metal containing 5% or more, A
The reason why the Si content of the l-alloy brazing filler metal is limited to 5% or more is because
This is because if it is less than 5%, the liquidus temperature will be high and sufficient brazing will be difficult. Usually the brazing filler metal contains 5 to 15 Si.
% of Be, Bi, Mg, etc. may be added for the purpose of improving brazing properties. The brazing filler metal is applied to one or both sides of the core material, each 3 to 3 times the total thickness of the core material.
0% cladding, preferably in the range of 3-15%.

In addition, the present invention is characterized by crating an Al alloy brazing material containing 5% or more of Si on one side of the core material having the above composition, and on the other side,
It is possible to clad an Al alloy skin material having a potential 50 mV or more more base than the core material. This is to protect the core material by cladding with an Al alloy skin material having a more base potential than the core material, so that this alloy layer acts as a sacrificial layer in cathodic protection. However, the potential difference is 50
The reason why mV or higher is selected is that a sufficient effect cannot be obtained at less than 50 mV. This sacrificial layer is 1~2 of the total board thickness.
The cladding is preferably 0%, preferably in the range of 2 to 10%.

Next, the reason for setting the cooling conditions of the present invention will be explained. When brazing heating (600℃), Si, Mg,
Cu etc. are dissolved in the matrix. When rapidly cooled from this state, Mg25I, Al--Cu compounds, etc. are finely precipitated, thereby improving the strength. Therefore, the cooling conditions were changed from 500℃ to 200℃ at 150℃/min.
The reason for setting the cooling rate above is that if the cooling rate is slower than 150° C./min in this temperature range, the precipitates will become coarse and the strength improvement effect will not be obtained.

be.

〔Example〕

The present invention will be described below with reference to Examples.

Example-1 An alloy having the composition shown in Table 1 was cast to a thickness of 70 m by DC casting.
An ingot with a width of 300 mm and a width of 300 mm was milled on each side, homogenized at 580°C for 3 hours, and then 4004 alloy brazing filler metal was applied on both sides to 15 mm of the total plate thickness on each side.
%, and was hot-rolled and cold-rolled into a plate having a thickness of 10 mm. This was annealed at 400° C. for 2 hours to produce a brazing sheet. In addition, T in Table 1
is 3003 alloy.

U indicates 6061 alloy.

This brazing sheet was evaluated for mechanical properties and brazing properties after heating for brazing. The results are shown in Table 2.

Mechanical properties were determined by heating to 600°C to simulate brazing, cooling at different cooling rates, and returning to room temperature for 1 day.
After being left for 0 and 100 days, measurements were taken. As shown in Figure 1 (a) and (b), the brazing property was determined by placing a 30 mm wide plate in the center of a 3003 alloy plate (2) with a width of 30 mm and a length of 50 mm.
nun, 50mm long brazing sheet (1)
was fixed vertically with a stainless steel wire (2) with a diameter of 3n++n interposed at one end, and after pretreatment, a flux suspension consisting of potassium fluoroaluminate salt was applied, and after drying, it was heated at 610°C in an N2 gas atmosphere. Heat brazing for 5 minutes,
The gap filling length (I) of the filler material shown in FIG. 1 (0) was measured. In this test, the gap filling length was 15IIl111
The above was judged as good.

Example-2 An alloy having the composition shown in Table 1 was subjected to DC treatment in the same manner as in Example-1.
An ingot with a thickness of 70 mm and a width of 3 Q Omm was obtained by casting, and this was faceted by 3 mm on each side and homogenized at 580°C for 3 hours, after which a 4004 alloy brazing filler metal was applied to one side and a skin material was applied to the other side. 7072 alloy as 10 of the total plate thickness.
%, and was hot-rolled and cold-rolled into a tentative material with a thickness of 1.5 mm.

This was annealed at 400° C. for 2 hours to produce a brazing sheet.

This brazing sheet was subjected to an Erichsen test to evaluate its moldability. In addition, this brazing sheet was processed into a header material for a radiator, which was combined with a 0.4 mm thick tube material made of 3003 alloy as a core material and clad with 4004 alloy brazing material and 7072 alloy skin material, and then brazed to form a radiator. A corrosive liquid was circulated through this, and the pitting depth was measured at 30 points on the header every 1.2°3 months to determine the maximum pitting depth. These results are shown in Table 3.

The test included Cl-195ppm and SO42-6 in the corrosive liquid.
QppmF e ” 311ppm, Cu 2+l
ppm and kept at 90°C for 8 hours, then heated to room temperature for 16 hours.
The holding time was repeated.

As is clear from Tables 1 to 3, the method of the present invention Nα9
~18. Nα3θ~39. Nα59-68. Nα80～
89 had good brazeability and formability, and the comparison method using conventional alloys T and U was Nα28.29°4.
9, 50.78. 79.99. compared to 100,
It can be seen that the tensile strength and corrosion resistance after brazing heating are excellent.

On the other hand, within the composition range of the alloy for the present invention (A.

F), the comparative method Nα1. has a cooling rate lower than 150° C./min. 2. 5. It can be seen that in No. 6, the improvement in strength after brazing heating was insufficient. In addition, comparative alloys outside the composition range of the alloy for the present invention include L, M, N, 0
．． P, 0. Comparison method using R, S Nα19-27.4
0-48, 69-77, 90-98, it can be seen that it melts during brazing heating, has poor formability, and is poor in one or more of the strength and corrosion resistance after brazing heating.

〔Effect of the invention〕

As described above, according to the present invention, the strength after brazing heating is high, the corrosion resistance is also good, and in the production of a heat exchanger,
This has significant industrial effects, such as making it possible to make heat exchangers thinner and lighter.

[Brief explanation of the drawing]

Figure 1 ((), (0) shows the gap filling test method during brazing heating, (a) is a side view before brazing, (0) is a side view after brazing, and Figure 2 is a side view after brazing. FIG. 3 is a perspective view showing an example of a radiator with a part cut away. (11 Brazing sheet (2 + 3003 alloy plate (3) Stainless steel wire (4) ), (4) Plate molded body (5) Refrigerant passage (6) Fin (7) Tube (8 seat plate (9) Backing (10) Resin tank (A) Port C) Figure 2 Figure 3

Claims (2)

[Claims] (1) Si0.4-1.2wt%, Fe0.15-1.
0wt%. Cu0.4-1.0wt%, Mn0.5-1.2wt%
, contains Mg0.05-0.8wt%, and further contains Cr0.0
01-0.5wt%, Zr0.001-0.3wt%,
Hf0.001-1.5wt%, Ti0.001-0.
5 wt%, B0.0001 to 0.1 wt%, the core material is an alloy containing one or more types within the range of 0.0001 to 0.1 wt%, and the balance is Al and unavoidable impurities, and one or both sides of the alloy are Si5
A brazing sheet clad with an Al alloy brazing filler material containing more than wt% is used as a heat exchanger member, the heat exchanger is assembled, and after heating and holding at the brazing temperature, it is heated from 500℃ to 200℃.
A method for manufacturing an aluminum heat exchanger, characterized in that the aluminum heat exchanger is cooled down to a temperature of 150°C/min or more. (2) Si0.4-1.2wt%, Fe0.15-1.
0wt%, Cu0.4-1.0wt%, Mn0.5-1
．． 2wt%, Mg0.05-0.8wt%, and further contains Cr0.001-0.5wt%, Zr0.001-0.
3wt%, Hf0.001-1.5wt%, Ti0.0
The core material is an alloy containing one or more of the following in the range of 0.01 to 0.5 wt% and B0.0001 to 0.1 wt%, with the remainder being Al and unavoidable impurities.
A heat exchanger is assembled by using a brazing sheet clad with an Al alloy brazing material containing 5 wt% or more and an Al alloy skin material having a potential 50 mV or more more base than the core material on the opposite side as a heat exchanger member. , after heating to brazing temperature,
A method for manufacturing an aluminum heat exchanger, characterized by cooling from 500°C to 200°C at a rate of 150°C/min or more.