JPS6335701B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy for brazing, and in particular has improved burning resistance during brazing, strength after brazing, and stress corrosion cracking resistance. In aluminum equipment that is generally constructed by brazing, such as a heat exchanger, a connector 2 is attached to one end of an extruded tube 1 that forms a fluid passage, as shown in FIG. It is connected to a fluid supply pipe by a screw 2a formed at the other end of 2. Since such connectors are required to have a certain level of strength (Vitkers hardness of 70Hv or more) when used after brazing, they easily become quenched when cooled after brazing.
Al alloys that are then age hardened at room temperature, e.g. 7003 (Al-0.50~1.0wt%Mg-5.0~6.5wt%Zn)
-0.05~0.25wt% Zr alloy; hereinafter wt% is simply abbreviated as %) or 7N01 (Al-0.20~0.7%Mn-1.0~2.0%
For extruded tubes that use Mg-4.0 to 5.0% Zn alloy and do not require much strength, 1050 (pure Al with a purity of 99.5% or more), 1100 (Al-0.05 to 0.20% Cu alloy),
1200 (Pure Al with a purity of 99.0% or more), 3003 (Al−0.05~
0.20%Cu−1.0~15%Mn alloy), 3203(Al−1.0~
1.5Mn alloy), 3005 (Al−1.0~1.5%Mn−0.20~
0.6%Mg alloy), 6063 (Al−0.20~0.6%Si−0.45~
0.9% Mg alloy) etc. are used. In addition, 4047 (Al-11 to 13% Si) and 4045 (Al-9 to 11% Si) are used as brazing filler metals.
%Si alloy) is used. Torch brazing, furnace brazing, immersion brazing, vacuum brazing, inert brazing, etc., which use flux, are used for brazing. The melting temperature range of brazing metal is 4047 to 577
~580℃, 577~590℃ for 4045, the melting temperature range of the connector material is 615~650℃ for both 7003 and 7N01, and the melting temperature range of the tube material is 1050, 1100, and 1200℃.
640~657℃ at 3003, 643~654℃ at 3005, 6063
616~654℃, standard brazing temperature is 600~630
℃, but in torch brazing, the temperature is instantaneous.
Temperatures can rise to around 640℃. Due to such variations in brazing temperature, when the connector material reaches a melting start temperature or higher, melting occurs at the grain boundaries, so-called burning development, which causes cracking or stress corrosion cracking during use. . In view of this, as a result of various researches, the present invention has developed an aluminum alloy for brazing that has improved burning resistance during brazing, as well as excellent strength and stress corrosion cracking resistance after brazing. That is, one of the alloys of the present invention contains 3.0 to 4.5% Zn,
It is characterized by containing 0.3 to 0.8% Mg, 0.2 to 0.9% Mn, and 0.2 to 0.5% Cr, with the remainder consisting of Al and inevitable impurities. Another of the alloys of the present invention is Zn3.0~4.5%,
Contains Mg0.3~0.8%, Mn0.2~0.9%, Cr0.2~0.5%, and further contains Zr, Ti, Cu, V, Mo, and Ag, respectively.
One or more types in total within a range of 0.3% or less
It is characterized by containing 0.5% or less of Al, with the remainder consisting of Al and unavoidable impurities. One of the alloys of the present invention has Zn and Mg as essential components, which are hardened by cooling after brazing and then age-hardened at room temperature. By reducing the age hardening properties within a range that does not impair the age hardening properties, the melting temperature of the alloy is increased, and the strength decrease due to the reduction of both elements is suppressed.
This was improved by adding Mn and Cr simultaneously, and the stress corrosion cracking resistance was improved. In addition, another one of the alloys of the present invention further includes Zr, Ti, Cu,
Strength and stress corrosion cracking resistance are improved by adding a small amount of one or more of V, Mo, and Ag. However, in the alloy of the present invention, the alloy composition is limited as described above for the following reasons. The reason for setting Zn3.0~4.5% and Mg0.3~0.8% is to obtain the necessary strength through cooling after brazing and then age hardening at room temperature, so either one of the two elements is the lower limit. If it is less than the upper limit, the required strength cannot be obtained, and if either exceeds the upper limit, the melting start temperature decreases, causing burning and stress corrosion cracking. In addition, Mn0.2-0.9% and Cr0.2-0.5% both improve strength, and Cr in particular improves stress corrosion cracking resistance, but if either of the two elements is below the lower limit, the effect is This is because, if the upper limit is exceeded, coarse metal compounds will be formed, which will significantly impede workability. Also, Zr, Ti, Cu, V, Mo, and Ag are each 0.3
The reason why one or more of these elements is set at 0.5% in total within the range of 0.5% or less is because none of these elements are as strong as Mn and Cr above, but they all improve strength and stress corrosion cracking resistance. also improve each independently
This is because if the amount exceeds 0.3%, or the total amount of two or more types exceeds 0.5%, coarse intermetallic compounds are formed, which significantly impedes workability. Note that the alloy of the present invention does not impair the properties of the alloy as long as the total amount of impurities such as Fe, Si, and other impurities contained in ordinary Al base metal as unavoidable impurities is 0.8% or less. The alloy of the present invention having the above-mentioned composition is effective not only for the above-mentioned connectors but also for other devices assembled by brazing, such as members requiring strength such as radiator brackets of heat exchangers. Further, as a brazing method, not only torch brazing using flux but also furnace brazing, fluxless vacuum brazing, inert gas brazing, etc. can be applied. Examples of the alloy of the present invention will be described below.
An alloy with the composition shown in Table 1 was melted, and the diameter was 230 mm.
A billet with a length of 500 mm was cast. This was soaked at a temperature of 550°C for 3 hours, and then extruded at a temperature of 500°C to produce a raw rod with a diameter of 50 mm. This was cold extruded and finished into a hexagonal bar with opposite sides of 24 mm.
A connector having the shape shown in FIG. 1 was prepared from this hexagonal bar, and tested for melting start temperature, hardness, burning during brazing, stress corrosion cracking after brazing, etc. These results are also listed in Table 1. For brazing, furnace brazing with flux is adopted as the most severe condition, and the brazing temperature is 620℃, which is the upper limit of general control, and the brazing material is
A 1050 tube was brazed to the connector using 4047. The melting start temperature was determined by differential thermal spectroscopy for the hexagonal bar. Further, the hardness was measured after being air cooled after brazing and then left at room temperature for one week. In addition, stress corrosion cracking is determined by applying a torque of about 3 kg to the threaded part of the connector after brazing, applying tensile stress to the tip, and then conducting a dry-wet alternating test (10-minute immersion - After drying for 50 minutes, stress corrosion cracking was determined.

【table】

[Table] As is clear from Table 1, all of the alloys of the present invention have a high melting start temperature, do not cause burning during brazing, have a hardness of 70 or more after brazing, and are resistant to stress corrosion cracking. I never wake up. On the other hand, from the composition range of the alloy of the present invention, Zn or
Comparative alloys No. 19 and No. 21, both of which have a high Mg content, have lower melting start temperatures and not only cause burning during brazing, but also stress corrosion cracking after brazing. It can be seen that the desired hardness cannot be obtained after brazing with comparative alloys No. 20 and No. 22, which have a small content of. Comparative alloy No. 1 has a higher Mn or Cr content than the composition range of the invention alloy.
No. 23 and No. 25 are satisfactory in terms of hardness, burning, stress corrosion cracking, etc., but the workability during manufacturing is extremely poor, and more than 50% cracking occurs during processing, so it is not suitable for industrial use. In addition, the desired hardness cannot be obtained after brazing with comparative alloys containing less Mn or Cr. Furthermore, the addition of one or more of Zr, Ti, Cu, V, Mo, and Ag improves the hardness of the alloy without reducing burning and stress corrosion cracking resistance, but the composition of the alloy of the present invention If it is added in excess of the upper limit of the range, the processability during manufacturing will be significantly reduced, and cracking of 50% or more will occur during processing, so it is not industrially viable. In this way, the present invention provides aluminum for brazing that does not cause burning or stress corrosion cracking even when brazed at the upper limit temperature of the general brazing condition range, and that requires strength such as clearing the required hardness during use. It has a remarkable effect as a member.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of a connecting portion between a heat exchanger tube and a connector. 1... Connector, 2... Tube, 3... Brazing material.

Claims (1)

[Claims] 1 Zn3.0~4.5wt%, Mg0.3~0.8wt%, Mn0.2~
An aluminum alloy for brazing that contains 0.9wt% Cr, 0.2~0.5wt% Cr, and the balance is Al and unavoidable impurities. 2 Zn3.0~4.5wt%, Mg0.3~0.8wt%, Mn0.2~
Contains 0.9wt%, Cr0.2~0.5wt%, and further Zr, Ti,
Aluminum alloy for brazing, containing Cu, V, Mo, and Ag within a range of 0.3wt% or less, and a total of 0.5wt% or less of any one or more of them, and the balance being Al and normal unavoidable impurities. .