JPH0436600A - Heat exchanger made of aluminum - Google Patents

Abstract

PURPOSE:To contrive higher brazing material properties and corrosion resistance, by providing an intermediate material between a core material and a brazing material, specifying the kind of alloy constituting the intermediate material, and determining the thickness of the intermediate material in relation to the Mg content of the core material. CONSTITUTION:A brazing sheet is a 4-layered clad material comprising a core material, an intermediate material provided on one side of the core material, a brazing material provided on the intermediate material, and a sacrificial anode material provided on the other side of the core material. The core material is an Al alloy containing 0.3-2.0 wt.% of Mn, 0.25-1.0 wt.% of Cu, 0.4-1.0 wt.% of Mg, 0.1-1.0 wt.% of Si and 0.06-0.35 wt.% of Ti, the balance being Al and unavoidable impurities. The intermediate material is an Al alloy containing 0.1-2.0 wt.% of Mn and 0.06-0.35 wt.% of Ti, together with up to 0.5 wt.% of Cu and/or up to 0.5 wt.% of Si, the balance being Al and unavoidable impurities. The brazing material is an Al-Si alloy, and the sacrificial anode material comprises an Al-Zn alloy or Al-Zn-Mg alloy. The thickness T (mum) and the Mg content (%) of the core material are in the relationship of expression I, and the Cu content (%) of the core material is greater than the Cu content (%) of the intermediate material by at least 0.15%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to aluminum heating devices such as radiators and heater cores having tubes, header plates, etc. that have good brazing properties and excellent strength and corrosion resistance after brazing. Regarding the exchanger.

[Prior art] Tube materials and header plate materials for automobile radiators, heater cores, etc. have a core material of Al-Mn alloy such as 3003, a brazing material of Al-Si alloy on one side, and a brazing material of Al-Si alloy on the other side. In addition, Al-Zn alloys and Al-Zn-M
A three-layer cladding material made of a sacrificial anode material made of a g-based alloy is used.

The Al-Si brazing filler metal is used for joining tubes and fins, and joining chinives and header plates.

Brazing is often performed using fluoride flux in an inert gas atmosphere. The material temperature during waxing is 580~
The temperature is 600°C and the holding time is often 0 to 5 minutes.

The other side clad with sacrificial anode material is inside (
water side) and acts as a sacrificial anode to prevent pitting and crevice corrosion of the core material.

[Problem to be solved by the invention] In recent years, there has been a strong demand to reduce the weight of radiators, heater cores, etc. (and thinner tube materials and header plate materials. It is necessary to improve the strength of the brazing material, and Mg is increasingly being added to the core material to increase the strength.However, Mg diffuses to the surface of the brazing material, and fluoride Because it reacts with the flux, a flocculent product (Mg fluoride) is generated and adheres to the core material, resulting in poor bonding.Thus, the amount of Mg added to the core material is practically 0.2 to 0. The content is limited to 3% by weight, which is an obstacle to increasing the strength.

In view of these circumstances, it is an object of the present invention to provide an aluminum heat exchanger with excellent brazing properties and corrosion resistance.

[Means for solving the problem] The present inventors have discovered that Mg diffuses from the core material to the surface (brazing material side).
In order to suppress the amount reaching ゛, an intermediate material was provided between the core material and the brazing material, and various studies were conducted regarding the alloy type and thickness of the intermediate material. As a result, MnO,1~2 was used as an intermediate material.
．． Using an alloy containing 0% by weight, TiO, 06 to 45% by weight, and further containing 0.5% or less of Cu and/or 0.5% or less of Si, the thickness is determined in relation to the amount of Mg in the core material. By doing so, it is possible to suppress the amount of Mg that reaches the surface and reacts with the flux, and brazing prevents a decrease in properties. It has been found that if the brazing temperature is controlled to 0.80 g/s 2 or less, brazing defects such as poor bonding and formation of flocculent products will not occur. Furthermore, it has been found that corrosion resistance is significantly improved by increasing the amount of Cu in the core material by 0.15% or more than the amount of Cu in the intermediate material, thus completing the present invention.

That is, the present invention provides an aluminum heat exchanger in which a plating sheet is brazed using a fluoride-based flux, wherein the plating sheet is Mn:OJ.
~2.0% by weight, Cu: 0.25~1.0% by weight,
Mg: 0.4-1.0% by weight, Si: 0.1-1
．． 0% by weight, Ti: 0.06 to 0.35% by weight, and the remaining Al alloy consisting of inevitable impurities is used as a core material, and one side of the core material has Mn: 0.1 to 2.0% by weight, T
i: Contains 0.06 to 0.35% by weight, and further contains CuO
, 5% by weight or less and/or 5% by weight or less of SiO, the remaining Al and unavoidable impurities are clad with an Al-Si alloy brazing filler metal, and the other surface is coated with Al-Zn. A four-layer clad material clad with a sacrificial anode material made of either a Zn-based alloy or an Al-Zn-Mg-based alloy, and between the thickness T (μm) of the intermediate material and the amount of Mg (%) in the core material. There is a relationship of T ≧ 58
This is an aluminum heat exchanger characterized by 15% more heat exchanger.

Next, the reason for limiting each component and its content in the plating sheet used in the present invention will be explained.

(1) Core material Mn of praising sheet: Improves strength. Furthermore, the potential difference between the core material and the sacrificial anode material is increased to improve corrosion resistance. 0
．． If it is less than 3% by weight, the effect will not be sufficient; 2. O1i amount%
If this value is exceeded, coarse compounds will be generated during casting, making it impossible to obtain a sound board.

Cu: Uses the potential of the core material to increase the potential difference between the sacrificial anode material and the intermediate material and the core material, thereby increasing the anticorrosion effect due to the sacrificial anode effect of the sacrificial anode material and the intermediate material. Furthermore, Cu in the core material diffuses into the sacrificial anode material and the intermediate material during soldering, forming a gentle concentration gradient, with the core material having a higher potential and the surface sides of the sacrificial anode material and intermediate material having less base potential. A gentle potential distribution is formed in between, making the corrosion form a general corrosion type. The anti-corrosion effect of Cu as described above will not be exhibited unless the amount of Cu in the core material is greater than the amount of Cu in the sacrificial anode material or the amount of Cu in the intermediate material. If the amount is not 0.15% or more, the concentration gradient after diffusion will be too small and the effect will not be sufficient.

Cu is not usually added to the sacrificial anode material, but Cu may be added to the intermediate material for the purpose of improving strength, so care must be taken in this case.

Cu in the core material also contributes to improving strength.

The anticorrosion effect and strength improvement effect of Cu shown above are not exhibited when the amount of Cu in the core material is less than 0.25% by weight;
．． If it exceeds 0% by weight, the corrosion resistance of the core material itself deteriorates, and the melting point of the core material decreases, causing local melting during waxing.

Mg: Improves the strength of the core material. The strength improving effect is better exhibited by age hardening after brazing when it coexists with Si and/or Cu.

If it is less than 0.4% by weight, the effect is not sufficient, and if it is less than 1.0% by weight,
If it exceeds this, the corrosion resistance decreases and the melting point of the core material decreases, causing local melting during soldering.

Si: Improves the strength of the core material. When coexisting with Mg, the strength improving effect is better exhibited by age hardening after brazing. If it is less than 0.1% by weight, the effect will not be sufficient, and if it exceeds 1.0% by weight, the corrosion resistance will decrease and the melting point of the core material will drop, causing local melting during soldering.

Ti: Further improves the corrosion resistance of the core material. That is, T
i is divided into regions with high and low Ti concentrations, which are distributed alternately in the thickness direction to form a layered structure, and regions with a low Ti concentration corrode preferentially compared to regions with a high Ti concentration, resulting in a layered corrosion pattern. do. As a result, the progress of corrosion in the thickness direction is inhibited and the pitting corrosion resistance of the material is improved. If it is less than 0.06% by weight, the effect will not be sufficient, and if it exceeds 0.35% by weight, coarse compounds will be produced during casting, making it impossible to obtain a sound plate.

Other elements: Fe, Zn, (rSZr, etc.) may be included within a range that does not impair the effects of the present invention. However, if Fe is included in a large amount, corrosion resistance will be impaired, so it is necessary to limit the content to 0.7% by weight or less. Since Zn makes the potential of the core material base and reduces the potential difference between the sacrificial anode material and the intermediate material, it needs to be contained in an amount of 0.62% by weight or less.

(2) Intermediate material Mn for plating sheet: Improves strength. If it is less than 0.1% by weight, the effect will not be sufficient, and if it exceeds 2.0% by weight, coarse compounds will be produced during casting, making it impossible to obtain a sound plate.

Ti: Ti is divided into high- and low-concentration regions, which are distributed alternately in the thickness direction to form a layered structure, and regions with low Ti concentration corrode preferentially compared to regions with high Ti concentration, resulting in a corrosion pattern. Layer. As a result, the progress of corrosion in the thickness direction is inhibited and the pitting corrosion resistance of the material is improved. 0,0
If it is less than 6% by weight, the effect is not sufficient, and 0.35% by weight.
If this value is exceeded, coarse compounds will be generated during casting, making it impossible to obtain a sound board.

Cu, Si: These elements contribute to improving strength. In particular, Mg diffuses from the core material during brazing, so Mg and Cu are mixed together after brazing.

Since Si coexists, the strength is improved by age hardening. However, since these elements promote the diffusion of Mg from the core material to the brazing material, the brazing properties deteriorate as the content increases. Therefore, in order to ensure brazability, it is necessary to limit Cu to 0.5% by weight or less and Si to 0.5% by weight or less. In addition, as mentioned above, in order to form a gentle concentration gradient of Cu from the core material to the surface of the intermediate material (brazing material side) and to make the corrosion form a general corrosion type, the amount of Cu in the intermediate material is adjusted to the core material. It is necessary to reduce the amount of Cu in the material by 0.15% by weight or more.

Other elements: F e s Cr SZ r s Z
n, etc. may be included within a range that does not impair the effects of the present invention. However, since Fe impairs corrosion resistance if contained in a large amount, it must be kept at 0.7% or less. Further, Zn may be added to the intermediate material to provide a sacrificial anode effect, but in this case, the content must be 0.3% or less so as not to promote the diffusion of Mg.

Thickness: The intermediate material is used to suppress the amount of Mg in the core material that diffuses and reaches the brazing material, and its thickness T (μm
) is determined by the following formula depending on the Mg amount (%) in the core material.

T≧58×l [Mg (%)] - 0J5) ”2 This formula was determined through experiments, but it means that the greater the amount of Mg in the core material, the thicker the intermediate material must be. When the thickness of the intermediate material does not satisfy this formula, that is, 58x I[Mg(%)] -0,15
) If it is smaller than '', the M to the filler metal side when soldering.
The amount of diffusion of Mg is large, and Mg and fluoride flux react with each other, resulting in defective bonding or producing flocculent products, which impairs the appearance.

(3) Brazing material of the plating sheet The brazing material is a commonly used Al-Si alloy. Usually, an alloy containing 6 to 13% by weight of Si is used.

(4) Sacrificial anode material of the plating sheet The radiator, heater core, etc. are clad on the side (inner surface) that comes into contact with water, and the sacrificial anode action prevents pitting corrosion and crevice corrosion of the core material.

Al-Zn alloy is used when it comes into contact with water only, and Al-Zn alloy is used when it comes into contact with rubber backing etc. to form a gap.
Zn-Mg alloys are often used. Further, in either case, an element that makes the potential less noble, such as I ns 5nSGaSB s, may be included.

(5) Amount of Mg Reacted with Flux Mg in the core material of the plating sheet diffuses through the intermediate material into the brazing material and reacts with the flux on the surface of the brazing material. If the amount of reacted Mg, that is, the amount of reacted Mg per unit surface area of the plating sheet is 0.80 g/lr" or less, no flocculent products or poor bonding will occur.

On the other hand, if it exceeds 0.80 g/m2, these brazing defects will occur.

The amount of Mg reacted here is measured as follows. That is, first, an EPMA line analysis is performed on a cross section of a plating sheet to be replaced with brazing to determine the distribution of Mg. At this time, a distribution curve as shown in FIG. 1 is obtained. From this distribution curve, the amount of Mg reacted R (g/s'
).

R= (Co/100) ・p ・(A-B)/)
'Here, Co: Initial Mg concentration in the core material (vt%) ρ Density of the nibrating sheet (g/g3) A: Area of the part lost from the core material due to diffusion (intestine 2) B: Intermediate area due to diffusion Area of the portion appearing in the material and brazing material (12) y; Length from Mg concentration 0 to Co in FIG. 1 (■) The size of y in FIG. 1 is arbitrary.

The above Mg reaction amount is 0.80g/if the relational expression between the thickness of the intermediate material of the present invention and the Mg content in the core material is satisfied.
m2 or less.

[Example code] The present invention will be explained in more detail with reference to Examples below.

Example 1 Alloys for core materials shown in Table 1, alloys for intermediate materials shown in Table 2
An alloy for the filling material shown in Table 3: An ingot of the alloy for the sacrificial anode material shown in Table 14 is prepared, and the alloy for the intermediate material, the alloy for the brazing material, and the alloy for the sacrificial anode material are hot-rolled to the specified size. These were combined with a core alloy ingot and hot rolled to obtain a Clarado material. Thereafter, a plate (HI3 material) with a thickness of 0.30 m5 was created by cold rolling, intermediate annealing, and cold rolling.

The composition of the cladding was as shown in FIG. 2, and the alloy combinations were as shown in Table 5.

Fluoride fluff was applied to the brazing material side of the obtained plating sheet, and the material temperature was heated to 600°C (holding time: 5 minutes) in N2 gas. After that, a tensile test and a corrosion test were conducted. The corrosion test method was CASS test for 30 days on the outside side (brazing metal side), and CI''' 1100pp, SO on the inside side (sacrificial anode side).
4"-100ppm, HCO3""1100pp, C
Immerse it in an aqueous solution containing u''loppm, heat it to 80℃ for 8 hours, then let it cool to room temperature and then heat it for 16 hours.
The cycle of leaving it alone was repeated for three months.

Further, the above-mentioned plating sheet was roll-formed, the ends of which were welded, and then a tube was made into a flat tube shape. At this time, the sacrificial anode material was placed on the inner surface of the tube, and the brazing material was placed on the outer surface of the tube. The obtained tube was assembled with corrugated fins, a header plate, and a side plate, and fluoride flux brazing was performed (material temperature: 600° C., holding time: 5 minutes) to produce a heat exchanger as shown in FIG. 3.

The fin material is Al-1.2% M n -1.5% Zn alloy, 0.1 ha in thickness, and the header plate material is Al1.2.
%Mn-0, Al-7 on one side of the 15% Cu alloy core material.
4%Si alloy brazing material and Al-1,5%Z on the other side.
It is clad with n-alloy sacrificial anode material, and has a thickness of 1.
It was 2ms. The resin tank was attached to the header plate by mechanical caulking via an O-ring. Regarding the heat exchanger obtained in this way, M diffused from the tube core material to the outer surface side and reacted with the flux.
The amount of g, the state of connection between the tube and fins, and the state of formation of flocculent products (Mg fluoride) on the outer surface of the tube were investigated.

The above results are summarized in Table 5. Invention example No. 1,
For No. 3 to 13, the tensile strength is 18 kgf/l1m
12 or higher, and the maximum corrosion depth is also small. Reacted Mg
The amount is also 0.80 g/s' or less, and the brazing property is also good.

In the case of Comparative Example No. 2, the difference between the amount of Cu in the core material and the amount of Cu in the intermediate material was as small as 0.10%, so the corrosion on the outer surface side was deep.

In the case of No. 14, the tensile strength is low due to the small amount of Mn in the core material, and the corrosion on the outer surface side is also deep. In No. 15, a healthy plate material was not obtained because the core material contained a large amount of Mn.

No. 18 had a rather low tensile strength because the amount of Cu in the core material was small, and the corrosion on the outer surface was deep. No.

No. 17 has a large amount of Cu in the core material, causing local melting in the brazing material, resulting in low tensile strength and large corrosion depth on the outer and inner surfaces.

No. 18 has a low tensile strength due to a small amount of Mg in the core material, and No. 19 has a large amount of Mg in the core material, resulting in poor brazing and deep corrosion on the outer surface side.

No. 20 has a low tensile strength due to a small amount of Si in the core material (No. 21 has a low tensile strength due to a large amount of Si in the core material, resulting in local melting, and the tensile strength is low on the outer and inner surfaces. Deep corrosion.

In No. 22, the corrosion on the outer and inner surfaces was slightly deeper due to less T1 in the core material. In No. 23, a healthy plate material was not obtained because the core material contained a large amount of Ti.

No. 24 uses 3003 alloy as the core material and does not have an intermediate material.
Although it is a three-layer cladding material, its tensile strength is low and the outer and inner surfaces are deeply corroded.

No. 25 has a slightly lower tensile strength because the intermediate material has less Mn. In No. 26, a healthy plate material was not obtained because the intermediate material contained a large amount of Mn.

In No. 27, the corrosion on the outer surface side was slightly deeper due to less Ti in the intermediate material. In No. 28, a healthy ingot was not obtained because the intermediate material contained a large amount of Ti.

In No. 29, the amount of Cu in the core material is smaller than the amount of Cu in the intermediate material, so the corrosion on the outer surface side is deep, and the C of the intermediate material
Due to the large amount of u, flocculent products are produced during brazing.

No. 30 has a large amount of St in the intermediate material, so flocculent products are produced during brazing.

*3003 Alloy Table 1 Table 2 Example 2 A 0.301 square plating sheet was prepared in the same manner as in Example 1 using the combinations shown in Table 6. Here, the thicknesses of the brazing material and the sacrificial anode material were the same as in Example 1, and the thicknesses of the intermediate material and core material were varied.

The obtained plating sheet was subjected to a tensile test and a corrosion test in the same manner as in Example 1, and a heat exchanger brazing test was conducted to determine the amount of Mg reacted with the flux, the joining condition of the tube and fin, and the tube. The formation of flocculent products on the outer surface was investigated.

The results are shown in Table 6.

If T≧58x ([Mg (%) - 0,35) "" is not satisfied, brazing failure has occurred.

Brazing test results in Table 6 and Nos. 5 to 8 in Table 5
The results of the brazing test are summarized in Figure 4. Curve T-58X ([Mg(%)-0,35
) If it is above 2, it means that the brazing property is good, and if it is below it, it is found that the brazing property is poor.The brazing conditions (material temperature, holding time) used in this example are normal. This is almost the upper limit of the conditions. Therefore, as long as normal brazing conditions are used, it can be said that no brazing failure will occur if T≧58X ([Mg (%) - 0,351"2).

[Effects of the Invention] As explained above, the aluminum heat exchanger of the present invention has excellent brazing properties with fluoride flux, as well as excellent material strength and corrosion resistance. down is possible.

[Brief explanation of drawings]

Figure 1 is a diagram schematically showing the Mg distribution according to EPMA line analysis in the cross section of the plating sheet after brazing. Figure 2 is a diagram showing the structure of the cladding material in the example. Figure 3 is a diagram showing the heat distribution in the example. A diagram showing the configuration of the exchanger, Figure 4 is a diagram showing the results of the brazing test in Example 2, Depth (rn) Figure 1

Claims (1)

[Claims] (1) In an aluminum heat exchanger formed by brazing a plating sheet using a fluoride-based flux, the plating sheet has Mn: 0.3 to 2.0% by weight, Cu: 0.25 to 1.0% by weight, Mg: 0.4-1
．． 0% by weight, Si: 0.1-1.0% by weight, Ti: 0.
The core material is an Al alloy containing 0.06 to 0.35% by weight, the remainder being Al and unavoidable impurities, and one side of the core material is coated with Mn: 0.06 to 0.35% by weight. 1 to 2.0% by weight, Ti: 0.06 to 0.35% by weight, and further contains 0.5% by weight or less of Cu and/or Si0
．． A brazing material of Al-Si alloy is clad through an intermediate material of Al alloy containing 5% by weight or less and consisting of the remaining Al and unavoidable impurities, and the other side is coated with Al-Zn alloy and Al-Zn-Mg alloy. A four-layer clad material clad with a sacrificial anode material made of any of the following, the thickness T (μm) of the intermediate material and the M
Between g amount (X), T≧58×{[Mg(%)]-0.35}^1^/^2
An aluminum heat exchanger having the following relationship and characterized in that the amount (%) of Cu in the core material is greater than the amount (%) of Cu in the intermediate material by 0.15% or more.