JPH0448045A - Aluminum brazing sheet for noncorrosive flux brazing - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of an aluminum brazing sheet and to attain its thinning and lightening in weight by adding a specified amt. of Be to a high strength Al thin sheet contg. Mg, Mn, Si, Cu, Fe, Ti or the like. CONSTITUTION:The compsn. of an Al brazing sheet for brazing by using noncorrosive flux is formed of a one contg., by weight, 0.5 to 2.5% Mn, 0.03 to 2.0% Mg, 0.1 to 1.5% Si, 0.01 to 1.0% Cu, 0.06 to 0.5% Be and 0.1 to 1.0% Fe and contg. 0.001 to 0.2% Ti or 0.0002 to 0.02% B together with the above Ti. The added Be suppresses the formation of Al-Fe series intermetallic compounds and improves the corrosion resistance. Furthermore, it also contributes to the improvement of the brazability and improves the static strength and fatigue strength.

Description

Detailed Description of the Invention "Object of the Invention" The present invention relates to an aluminum plating sheet for non-corrosive flux brazing, and aims to provide an aluminum plating sheet for non-corrosive flux brazing that has high strength and high corrosion resistance. It is something to do.

(Industrial application field) Aluminum plating sheet for non-corrosive flux brazing. More specifically, aluminum plating sheet for brazing using aluminum potassium fluoride non-corrosive flux.

(Prior art) Potassium aluminum fluoride flux (hereinafter referred to as -F-Al series) is used in automobile radiators and automobile air conditioners because the flux residue after brazing is non-corrosive and no post-treatment is required. It is widely used for brazing heat exchangers, etc., and is published in Japanese Patent Publication No. 5B-27037 and US Pat. No. 3,951,328.

On the other hand, in recent years, there has been a strong demand for lightweight aluminum radiators, and in order to meet this demand, it is essential to reduce the thickness of radiator constituent members, and for this purpose, it is necessary to have high strength and high corrosion resistance. However, in such cases, it is common to improve the strength by adding Mg, and this Mg
JP-A-63-180394 discloses that 0.001 to 0.05 wt % of beryllium is added to increase the strength by adding g to improve the brazing property.

(Problems to be Solved by the Invention) The above-mentioned technique of JP-A-63-180394 can be said to be a preferable technique for achieving high strength and good brazing properties, but it does not contain a certain amount of Fe. In aluminum alloy systems for heat exchangers and the like, which are required to have high-temperature strength and buckling resistance, corrosion resistance, particularly pitting corrosion resistance, cannot be achieved. That is, it is recognized that the crystals and precipitates of the Al--Fe intermetallic compound become the nucleus of pitting corrosion or the nucleus of fatigue fracture, making it impossible to obtain sufficient corrosion resistance.

"Structure of the Invention" (Means for Solving the Problems) The present invention has been devised after repeated studies to solve the problems of the conventional products as described above. The present invention was completed by discovering that the corrosion resistance was significantly improved by adding a predetermined amount or more of Be, and the details are as follows.

Mn: 0.5-2.5wt%, Mg: 0.0
3 to 2.0 wt%, Si: O, 1 to 1.5 wt%,
Cu: 0.01-1.0wt%, Be: 0.0
6 to 0.5 wt%, Fe: 0.1 to 1.0 wt%, and Ti: O, OO 1 to 0.2 wt% or Ti: 0.00
1-0.2wt% and B: 0.0002-0.0
An aluminum plating sheet for non-corrosive flux brazing, characterized in that it is made of an aluminum alloy containing 2 wt% and the remainder containing unavoidable impurities.

(Function) The non-corrosive aluminum plating sheet for fluff brazing according to the present invention contains Mg, Mn, and Si.

By adding 0.06 wt% or more of Be to a high-strength aluminum thin plate containing Cu, Fes Ti, etc., the corrosion resistance is improved, and the thickness of the layer can be made thinner, thereby achieving preferable weight reduction.

That is, the effect of e addition as described above is caused by Fe added to improve strength and buckling resistance at high temperatures. It is presumed that this suppresses the precipitation of -Fe-based intermetallic compounds and prevents this Al--Fe-based intermetallic compounds from becoming the core of pitting corrosion.

In the plating sheet of the present invention as described above, each alloy component contained is -t% (hereinafter simply referred to as %) and is as follows.

Mg: 0.03-2.0%.

Mg is an element that imparts strength, and if it is less than the lower limit, its effect is insufficient, while if it exceeds the upper limit, the plastic workability and brazing properties are reduced.

Be: 0.06-0.50%.

Be suppresses the formation of Ql-Fe-based intermetallic compounds,
Improves pitting corrosion resistance. It also contributes to improved brazing properties and improves static strength and fatigue strength.

If it is less than 0.06%, these effects will be poor;
Even if the content exceeds 0%, the effect will be saturated, so 0.50
% or less.

Mn: 0.5-2.5%.

Mn makes the pitting corrosion potential more noble and increases the difference from the immersion potential, thereby improving pitting corrosion resistance, and also improves strength and buckling resistance. If the content is less than 0.5%, these effects will be insufficient, while if the content exceeds 2.5%, there is a risk of the formation of giant compounds, which will impede castability and workability, so the content should be 2.5% or less. It is necessary.

Si: 0.1-1.5%.

Si ages hardens due to its coexistence with the above-mentioned Mg, thereby improving the strength. If the content is less than 0.1%, this effect cannot be obtained properly, and if the content exceeds 1.5%, the melting point of the material will decrease, causing problems in brazing, so the upper limit is set at 1.5%. .

Cu: 0.01-1.0%.

Cu contributes to improving strength and can achieve this effect at 0.01% or more, but if it is contained in more than 1.0%, the overall corrosion resistance will decrease, so it should be 1.0% or less. It is necessary to do so.

Fe2 0.1-1.0% As mentioned above, Fe improves high temperature strength and buckling resistance, and for this purpose it is necessary to contain it in an amount of 0.1% or more. However, if this Fe content exceeds 1.0%, the above-mentioned effect of adding Be will be reduced, and the amount of precipitates will increase, deteriorating corrosion resistance, W workability, etc.
．． 0% or less.

Ti:0.001~0.2% or Ti:0.001~
0.2% and B: 0.0002-0.02%Ti
Alternatively, Ti and B refine the ingot crystal grain structure. In addition, Ti coexists with Mn and Cu to cause the corrosion of the plating sheet core material to be a general corrosion type, and in order to properly obtain these effects, it is necessary to contain 0.01% or more. . However, if the content exceeds 0.2%, a giant intermetallic compound is formed and the castability and plastic workability are deteriorated, so it is necessary to set this as the upper limit.

Further, when B is contained together with Ti in an amount of 0.0002 to 0.02%, the ingot crystal grain structure can be further refined. 0.
If it is less than 0,002%, the effect is not significant, and if it is less than 0,0
If the content exceeds 2%, large intermetallic compounds are formed and castability and plastic workability are deteriorated, so it is necessary to set this as the upper limit.

The composition of the non-corrosive fluff for Blazing Sea 1 is fluorides such as alkali or alkaline earth metals, such as KF, mixtures of these compounds mainly composed of AlF3, complex compounds, and KAlF4 alone. , or 38 IF6, K28 IFs, KAlF3, AII
It is a mixture, complex compound, etc. containing at least two or more of the above as main components, and contains 90% or more. Of course, these fluxes may contain other elements or compounds as impurities, but they may also be intentionally added with other elements or compounds, such as ZnF and Li, for the purpose of further lowering the melting point or for adhesion or other purposes.
It is also possible to add F.

Regarding the amount of beryllium added in the present invention described above, the amount of beryllium added was 0 with respect to the present invention material 1 of the example described later.
Figures 1 and 2 summarize the results of 1000 cycles of alternating saline immersion test and 90 cycles of combined corrosion test for samples with changes in the range of ~0.30%. In both the salt water alternating immersion test and the composite corrosion test shown in Figure 2, it was confirmed that the maximum pitting depth decreased rapidly near the area where the Be addition amount exceeded 0.03%. By becoming .06%, 0
．． The maximum pitting depth is less than one-third of the depth at 0.03%,
By increasing the amount of Be added to 0.10% or more, the amount can be further reduced by half.

(Embodiments) Specific embodiments of the invention as described above will be described below.

Examples of the composition and comparative examples of typical aluminum alloys for plating sheet core materials adopted by the present inventors are shown in Table 1 below.

Table 1 *It was analyzed as an impurity.

The present invention core material and comparative core material in Table 1 above are 9.5%
Each material was melted and cast together with Si brazing material, hot rolled to form a three-layer clad material in which both sides of the core material were clad with brazing material, and then cold rolled to produce a plating sheet with a thickness of 0.25 mm. The cladding rate was 10% in all cases.

JIS No. 5 tensile test pieces were prepared using each of the plating sheets thus prepared as test materials.) [JIF6
A flux, which is a complex of 25% and 475% of KAlF, was suspended in water, applied and dried, and then brazed and heated at 600" x 3 minutes to obtain a corrosion resistance test piece and a test piece for measuring tensile strength.

In addition, using the plating sheet prepared as described above as a test material, the JIS standard as shown in Figure 3fa) to (C)
An inverted T-shaped solder plate of A3003 with a thickness of 21 mm and a length of 651 mm and a vertical piece 1 of the present invention material and a comparative material with a thickness of 0.25 m, a height of 25 mm, and a length of 40 mm. Brazing test pieces were prepared, and pitting corrosion resistance was evaluated using these test pieces after brazing. Table 2 below summarizes the results of these tests. In Table 2, the evaluation results of brazing properties are also shown, and the brazing properties were judged based on the criteria listed in Table 2 using the solder portion 3 in Fig. 3.

That is, the pitting depth of the material of the present invention in the alternating saline immersion test was 0.05 mm or less at maximum, and 0.03 Ilm on average, whereas the maximum depth of the comparative material was 0.11 to 0.25 a.
m, with an average of 0.06 to 0.18 m, and even in the composite corrosion test, the maximum depth and average depth of the comparison material reached two to several times, and in some cases more than 10 times, that of the inventive material. was confirmed. In addition, all of the materials of the present invention were evaluated to be good in brazing properties, and it can be said that they are also excellent in tensile strength after brazing.

"Effects of the Invention" According to the present invention as explained above, high strength and excellent corrosion resistance can be obtained in a non-corrosive flux brazing aluminum plating sheet, and therefore, thinner material can be used. This invention ensures favorable durability, reduces weight, saves energy, and further reduces costs, and is industrially highly effective.

[Brief explanation of the drawing]

The drawings show the technical contents of the present invention, and Fig. 1 is a diagram summarizing the relationship between the amount of beryllium added and the maximum pitting depth in 1000 cycles of the salt water alternate immersion test, and Fig. 2 is a diagram summarizing the relationship between the amount of beryllium added and the maximum pitting depth in 1000 cycles of the salt water alternate immersion test. FIG. 3 is a diagram summarizing the relationship between the amount of beryllium added and the maximum pitting depth in a 9° cycle of corrosion testing, and FIG. 3 is an explanatory diagram showing the configuration of a tensile test piece in an example of the present invention.

Claims (1)

[Claims] Mn: 0.5-2.5 wt%, Mg: 0.03-2.
0wt%, Si: 0.1-1.5wt%, Cu: 0.0
1-1.0wt%, Be: 0.06-0.5wt%, F
e: 0.1 to 1.0 wt%, and Ti: 0.001 to 0.2 wt%, or Ti: 0.001 to 0.2 wt% and B: 0.0002 to 0.02 wt%. An aluminum brazing sheet for non-corrosive flux brazing, characterized in that it is made of an aluminum alloy containing the remainder unavoidable impurities.