JPH046239A - High strength aluminum alloy excellent in brazability - Google Patents

Abstract

PURPOSE:To obtain an Al alloy excellent in brazability, having high strength and furthermore excellent in corrosion resistance and cold forgeability by specifying the compsn.constituted of Mg, Zn, Mn, Cu,Ti, Zr, Fe, Si and Al. CONSTITUTION:This is a high strength Al alloy contg., by weight, 0.15 to 0.5% Mg, > 3.0 to 7.0% Zn and 1.0 to 2.0% Mn, furthermore contg. at least one kind among 0.1 to 0.4% Cu, 0.005 to 0.2% Ti and 0.01 to 0.2% Zr, in which < 0.3% Fe and < 0.3% Si are regulated and the balance Al with inevitable impurities. The Al alloy is excellent in brazability and is suitable as the material for unions, connectors or the like. Furthermore, this Al alloy has excellent corrosion resistance and cold forgeability as well as has hardness (Hv) of about >=65.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wax suitable as a material for unions and connectors used as connection parts in aluminum alloy parts for heat exchangers such as car cooler condensers, evaporators, and heater cores. This invention relates to a high-strength aluminum alloy with excellent adhesion properties.

[Conventional technology] FIG. 1 is a plan view showing a car cooler capacitor.

A tube 1 of the car cooler condenser has a plurality of bends and is meandering, and fins 2 are disposed between adjacent portions of the tube 1. A union 3 is brazed to both ends of the tube 1 with a brazing material 5, and a screw 4 is attached to the outer peripheral surface of the tip of the union 3.
is formed.

The unions 3 and connectors used to connect the pipes of heat exchangers, etc., have screws 4 on the outer circumferential surface of their tips.
The piping and the member are connected by screwing into the female thread of the corresponding member. Therefore, the aluminum alloy material used for the union 3, connectors, etc.
It is necessary that the screw 4 has such strength that it can maintain a predetermined strength when the screw 4 is carved on its surface. In addition, since the union 3 and the connector are exposed to high temperatures of approximately 600°C during the brazing heat process, the aluminum alloy material used for these parts has high strength after being heated to such temperatures. It is also required.

Generally, the wax aluminum alloy material is 100%
0 series alloys and 3000 series alloys have been used, but these 1000 series alloys and 3000 series alloys have the disadvantage of low strength. For this reason, 7NO1 alloy has conventionally been used as a material for unions, connectors, etc. because of its high strength. This 7NO1 alloy is, for example, 1.2
It is an alloy containing 4.5% by weight of Mg and 4.5% by weight of Zn, with the remainder being A and unavoidable impurities.

Next, as an example of a method for manufacturing heat exchanger parts, a method for manufacturing a car cooler capacitor will be described with reference to FIG.

First, torch-braze or TI the union 3 to the tube 1.
C Weld and join. Next, the tube 1 and the fins 2, which have been formed into a predetermined shape, are placed in a predetermined position and fixed to each other to be assembled.

Next, after placing a brazing material at the connection between tube 1 and fin 2, tube 1 and fin 2 are heated in a heating furnace to convert fin 2 into a tube.

Braze to 1. This completes the car cooler capacitor.

Recently, in order to shorten the manufacturing process of parts for heat exchangers such as car cooler condensers, unions and fins have been brazed to tubes at the same time in a heating furnace. However, since the aforementioned 7NO1 alloy has poor brazing properties,
It is difficult to mass-produce heat exchanger parts using such a method using unions, connectors, etc. made of 7NOI alloy. In particular, when a fluoride-based non-corrosive flux is used, many brazing defects occur.

In recent years, it has become clear that the reason for the poor brazing properties of aluminum alloys such as 7NO1 alloy is that Mg contained in the alloy reacts with flux, resulting in a decrease in the action of flux. Based on this knowledge, various aluminum alloy materials with improved brazing properties have been proposed (JP-A-83-86845, JP-A-6L-119G).
No. 45, Japanese Patent Publication No. 1-22573G).

[Problem to be solved by the invention] However, although these aluminum alloy materials have excellent brazing properties, their strength is extremely low compared to 7NO1 alloy, and therefore they cannot be used with screws such as unions and connectors. The material of the member to be engraved is not satisfactory.

The present invention has been made in view of such problems, and includes:
An object of the present invention is to provide a high-strength aluminum alloy that has excellent brazing properties and high strength, and is suitable as a material for unions, connectors, etc.

[Means for Solving the Problems] The high-strength aluminum alloy with excellent brazing properties according to the present invention has an M g s 3 ,0 of 0.15 to 0.5% by weight.
More than 7.0% by weight of Zn and 1.0 to 2% by weight
．． Contains 0% by weight of Mn and 0.1 to 0.4
wt% Cu, 0.0Q5 to 0.2wt% T
i and at least one element selected from the group consisting of 0.01 to 0.2% by weight of Zr, and Fe
It is characterized in that the contents of both and Sl are regulated to less than 0.3% by weight, and the remainder consists of A and unavoidable impurities.

[Function] Next, the reason for adding each component of the aluminum alloy according to the present invention and the reason for limiting the composition will be explained.

Along with Zn, which will be described later, Mg is an extremely effective element for increasing the strength of aluminum alloys.

However, when the Mg content is less than 0.155% by weight, the effect of improving strength is not sufficient.

On the other hand, when the Mg content exceeds 0.5% by weight, the brazeability of the aluminum alloy decreases. Therefore, the Mg content is set to 0.15 to 0.5% by weight.

Zn reacts with the above-mentioned Mg and precipitates into the aluminum alloy as M g Z n 2, which has the effect of improving the strength of the aluminum alloy. However, the zn content is 3.0
If weight% or less, the strength (hardness) of the aluminum alloy
is extremely low compared to the 7NO1 alloy. On the other hand, when the Zn content exceeds 7.0% by weight, not only the strength-improving effect of Zn is saturated, but also the workability of aluminum alloys such as extrusion and forging is inhibited, and the corrosion resistance is significantly reduced. Therefore, the Zn content exceeds 3.0% by weight and is 7.0% by weight.
% by weight or less.

L Mn forms a solid solution in the aluminum base and has the effect of improving the strength of the aluminum alloy. In addition, the Mn-based product in this section has the effect of improving machinability during thread cutting. Furthermore, Ano.

Solid solution of Fe in Mn also has the effect of improving corrosion resistance.

In this case, if the Mn content is less than 1.0% by weight, the above effects are not sufficient. On the other hand, when the Mn content exceeds 2.0% by weight, giant pieces are produced and the extrudability and cold forgeability of the aluminum alloy are reduced. Therefore, the Mn content is set to 1.0 to 2.0% by weight.

Qj-Cu has the effect of increasing the strength of the aluminum alloy and improving the pitting corrosion resistance. In other words, pitting corrosion occurs around the Fe-based product, which has a higher potential than the aluminum base. Therefore, by including Cu in the aluminum alloy, the potential of the aluminum base increases, and the pitting corrosion resistance of the aluminum alloy improves.

In this case, if the Cu content is less than 0.1% by weight,
The strength and pitting corrosion resistance of aluminum alloys are not sufficient.

On the other hand, when the Cu content exceeds 0.4% by weight, the overall corrosion susceptibility increases and the corrosion resistance decreases. For this reason, C
When u is contained, its content is 0.1 to 0.4% by weight.

Both Ti and Zr have the effect of making the crystal grains of the aluminum alloy finer and improving its strength.

When the Ti content is 0.005% by weight and there are no grooves, the effect of refining crystal grains is small and the strength is not sufficiently improved.

On the other hand, when the Ti content exceeds 0.2% by weight, giant crystallized substances are generated, resulting in poor extrudability and forgeability. Therefore, when Ti is contained, the content is set to 0.005 to 0.2% by weight.

Further, like Ti, when the content of Zr is less than 0.0 I% by weight, the effect of refining the crystal grains of the aluminum alloy is small, and the strength is not sufficiently improved. On the other hand, Z
When the r content exceeds 0.2% by weight, giant pieces are produced and extrudability and forgeability are reduced. For this reason, Z r
If it contains, reduce its content to 0. 0.2% by weight.

Note that the above-mentioned Cu1Ti and Zr may be contained in the aluminum alloy at least one of these elements within the above content range.

L If 0.3% by weight or more of Fe is contained in the aluminum alloy, the pitting corrosion resistance of the aluminum alloy will decrease. Therefore, it is necessary to control the Fe content to less than 0.3% by weight.

When the content of L Si is high, the pitting corrosion resistance of the aluminum alloy decreases.

Further, in the case of an A-no-Zn-Mg alloy such as the aluminum alloy according to the present invention, when the Si content is high, the strength thereof decreases. That is, aluminum alloy materials such as unions and connectors are slightly hardened by heating during brazing, and then their strength is improved by natural aging.

This natural aging property is due to the Mg2 contained in the aluminum alloy.
Generated by Si and MgZn2. In this case, the strength improving effect of MgZn2 is greater than that of Mg2Si.

When Puff-Zn-Mg alloy contains a large amount of Si,
Mg selectively reacts with Si to produce Mg2Si, which has a small strength-improving effect due to natural aging, and MgZn2, which has a large strength-improving effect, is hardly produced. Therefore, the strength improvement effect due to natural aging is reduced, and the strength of the aluminum alloy is reduced. Therefore, the Si content needs to be regulated to less than 0.3% by weight in order to improve pitting corrosion resistance and improve strength through natural aging.

In addition, the above-mentioned Fe and Si may be contained in an amount of 0.2% by weight each in consideration of ease of industrially manufacturing the aluminum alloy.

[Examples] Next, examples of the present invention will be described in comparison with comparative examples that fall outside the scope of the claims.

An aluminum alloy having the components shown in Table 1 below was melted using a normal melting method, and an ingot having a diameter of 155 mm was cast. These ingots were heated to a temperature of 450 to 550''C and subjected to a homogenization treatment for 4 to 12 hours.

Thereafter, hot extrusion was performed at a temperature of 450° C. to form a round bar with a diameter of 30 mm. In addition, Comparative Example 6 is 7NO
1 alloy equivalent material, Comparative Example 8 is a 3003 alloy,
Comparative Example 9 is a 6061 alloy.

Table 1 The strength (hardness), brazeability, cold forgeability, and corrosion resistance of the round bars of these Examples and Comparative Examples were examined by the methods described below.

■Strength A test piece with a diameter of 30 ml and a thickness of 20 mm was cut out from each round bar of the Examples and Comparative Examples, and this test piece was
℃ for 1 minute, and then cooled at a rate of 20℃/min. After leaving the test piece at room temperature for 7 days, the Vickers hardness (Hv) of the test piece was measured.

The results are shown in Table 2 below.

■Brazing property From each round bar of the example and comparative example, the length is 5 m111 and the width is 5 m
A test piece having a length of 25 mm was cut out. Then, as shown in FIG. 2, one end of this test piece 6 was placed on a liner 7 and placed on a plating sheet 8. The size of this praising sheet 8 is 25 mm in length.
The side is 2511II11. Then, after applying a fluoride-based flux and performing furnace brazing, the brazing properties were evaluated by measuring the gap filling length of the brazing material. The brazing conditions were as follows: the temperature was 600°C, the time was 1 minute, and the atmosphere had a dew point of -40°C.

The results are also shown in Table 2. However, if the gap filling length of the brazing filler metal is 15m + n or more, ◎, or 10mm or more 1
A case of less than 5 mm is shown as ◯, a case of 5 mm or more and less than 10 mm is shown as △, and a case of less than 5 mm is shown as ×.

■Corrosion resistance Each round bar of the example and comparative example was heated at a temperature of 600°C for 1 minute, and then cooled at a rate of 20°C/min to a thickness of 3 mm.
A test piece with a width of 25 mm and a length of 20 mm was cut out.

Then, 5% NaCf, acetic acid (pH
3) and 50°C containing 0.26g/no Cu ions
A CASS test was conducted in which the liquid was sprayed for 100 hours, and the depth of the corrosion that occurred was measured to evaluate the corrosion resistance.

The results are also shown in Table 2. However, pitting depth is 0
．． ◎ if less than 2+u+, 0.2nua or more 0.3m
A case of less than m is indicated by ○, a case of 0.3 +++ m or more and no drop of 0.5 mm is indicated by Δ, and a case of 0.5 mm or more is indicated by ×.

■Cold forgeability After a specimen with a diameter of 3 hm and a thickness of 20 mm was subjected to zero heat refining, upsetting forging was performed and the processing rate when cracking occurred was investigated.

As shown in FIG. 3, the processing rate was calculated using the following formula 1, where H6 is the height of the specimen before processing and H is the height at which cracking occurs.

Processing rate = (Ho-H)/Ho (1) The results are also shown in Table 2. However, when the processing rate is 0.8 or more, ◎, and when it is 0.6 or more and less than 0.8, 0.0.
The case of 5 or more and less than 0.6 is shown as △, and the case of 0.5 or less is shown as ×.

Based on these results, the suitability as a material for unions, connectors, etc. was comprehensively evaluated. The results are also shown in Table 2. However, if it is extremely suitable as a material for unions and connectors, ◎, if it is suitable, ○,
The case where it is not suitable is shown as △, and the case where it is extremely unsuitable is shown as ×.

Table 2 As is clear from Table 2, the aluminum alloys of Examples 1 to 11 all have a gap filling length of 1
0rnrn or more, and has good brazing properties,
Excellent corrosion resistance and cold forging properties.

Moreover, the hardness (Hv) is 56 or more, and the strength is high.

On the other hand, Comparative Examples 1 to 9 all had low hardness or insufficient brazing properties, corrosion resistance, or cold forging properties, and were not suitable as materials for unions, connectors, and the like.

[Effects of the invention As explained above, the aluminum alloy according to the present invention has
Predetermined amount of Mg1Zns Mn1CIJN Ti and Z
r, and the content of Fe and Si is set to a predetermined value of 0.
Since it is regulated by grooves, it has excellent brazing properties, high strength, corrosion resistance, and cold forgeability. Therefore, this aluminum alloy is extremely suitable as a material for joints such as unions and connectors that are furnace-brazed to heat exchanger tubes and the like.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a car cooler capacitor, FIG. 2 is a perspective view showing a brazing test method, and FIG. 3 is a perspective view showing a cold forgeability test. 1; tube, 2; fin, 3: union, 4; screw,
5; brazing metal, 6; test piece, 7; liner 8; brazing sheet

Claims (1)

[Claims] (1) 0.15 to 0.5 wt% Mg, 3.0 wt%
more than 7.0% by weight of Zn and 1.0 to 2.0% by weight of Mn, and 0.1 to 0.4% by weight
of Cu, 0.005 to 0.2 wt% Ti and 0.0
It contains at least one element selected from the group consisting of 1 to 0.2% by weight of Zr, and the content of Fe and Si is controlled to less than 0.3% by weight, and the balance is Al.
A high-strength aluminum alloy with excellent brazing properties characterized by comprising: and inevitable impurities.