JPS6078188A - Composite pipe material for heat exchanger made of al alloy having excellent hole corrosion resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite tube material having excellent pitting corrosion resistance and particularly suitable for use as a tube material for an AC alloy heat exchanger.

Conventionally, heat exchangers such as heat exchangers for motorcycles and automobiles have been made of He8 alloy.

Usually, this A2 alloy heat exchanger 1d is made of Mn as a tube material.
: Contains 0.5 to 15 fission, and further contains Zr as necessary:
0.02-0.2%, Cr: 0.02-0.2%
, Mg: 0, 05-0.5%, and Cu: 0
．． 05~O',! On the outside of the AQ gold alloy core material, which has a composition (the above is by weight, the below is by weight) that contains two or more of I% and the remainder is AQ and unavoidable impurities. , S] Sections 3 to 15, and if necessary, one problem, 03 to 25% and Bi: 0.01 to 0.
A two-layer composite pipe material is used, which is clad with an A1 alloy brazing material containing 01 or 2 of the 3 elements, with the remainder consisting of AQ and unavoidable impurities. By combining single-layer or multi-layer fin materials of chemically base AQ or A9 alloy, these two parts are
Brazing is produced by heating to a temperature in a vacuum or in a non-oxidizing atmosphere.

However, in the AQ alloy heat exchanger manufactured in this way, when circulating water containing, for example, Cu ions or Ct ions is used as the heat exchange medium, pitting corrosion occurs relatively easily in the tube material. This often progresses deeply into the pipe 4d as localized corrosion, and this often develops into through holes.

Regarding the composition of the core material in the tube material of the conventional AQ alloy heat exchanger mentioned above, the Mn component is included to particularly improve high temperature strength and suppress thermal deformation during brazing, for example. Zr and Cr
The components are contained to further improve high-temperature strength, raise the recrystallization temperature, enlarge recrystallized grains formed during brazing, and thereby improve intergranular corrosion resistance. , and further contains Mg and Cu components (
It is contained to form a solid solution in the base material to strengthen it and thereby improve its room-temperature strength.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a tube material for an A2 alloy heat exchanger that does not cause pitting corrosion, and as a result, the two-layer structure for the conventional AQ alloy heat exchanger described above was developed. Pure A9, or Zn:
3 by cladding with a skin material of A9 alloy having a composition containing 0.05 to 05% and the remainder consisting of AQ and unavoidable impurities.
When it has a layered structure, the pure AQ- or AQ-Zn alloy skin material has at least Mn: 0 in the composite pipe structure.
．． Since it is electrochemically less base than the core material of A8 alloy containing 5 to 15%, it exerts a sacrificial anode effect on the core material and protects it well from corrosion. They obtained the knowledge that the occurrence of pitting corrosion can be prevented.

The present invention was made based on the above findings, and A9 containing at least 0.5 to 15% of Mn.
Pure A, A, or Zn: 0.05 is placed on the inside of a two-layer composite pipe material formed by cladding an A2 alloy brazing material containing at least Sl: 3 to 15q6 on the outside of an alloy core material.
The AQ alloy composite tube material for heat exchangers has a three-layer structure by cladding with an A9 alloy skin material having a composition of 0.05% and the remainder consisting of Al and unavoidable impurities.

In addition, in the skin material of the composite pipe material of this invention, Zn
may be included as an alloying component, but this makes the skin material more electrochemically base than the core material, and also makes the corrosion form completely soluble, thereby reducing the sacrificial anode effect on the core material. If the content is less than 0.05%, the desired effect cannot be obtained, while if the content exceeds 0.05%, Since local corrosion becomes more likely to occur and the amount of corrosion increases, the content should be reduced from 005 to 0.
It was set at 5%.

Next, the composite pipe material of the present invention will be specifically explained using examples.

Examples A9 alloys for core materials having the compositions shown in Table 1 were produced by a conventional melting and casting method] ~5. Afi for brazing metal
Alloy a and A9 alloy A-C for skin material were melted and cast to form an ingot. Although these ingots are not shown in Table 1, they all contain Mn:
0.01% or less, Mg: 0.01% or less, Cu
: O○3 attack or less, Zn: 0.02% or less.

Fe: 0.4% or less, Si: 0.359! + or less, Zr: 0.01% or less, and Cr: 0.01% or less.

Next, the various AQ alloy ingots obtained as a result are subjected to recycle and homogenization heat treatment, and then processed into core material ~e alloy 1~
5 is the plate thickness, A9 alloy A-C for skin material and A9 alloy a for brazing metal are hot rolled to 3 mm, and further A9 alloy A-C for skin material and AI for brazing metal. ! A hot-rolled sheet of alloy a was cold-worked to have a thickness of 1B.

Next, the resulting hot-rolled sheets of A1 alloys 1 to 5 for core material with a sheet thickness of 8 and M alloy A for skin material with sheet thickness of 1 mx were prepared.
Using cold-rolled sheets of AQ alloy a for brazing metal and AQ alloy a, these sheets were laminated according to the combinations shown in Table 2, cladded by hot rolling, and then cooled without appropriately intermediate annealing. By performing inter-rolling (final processing degree, 30%), plate-like materials 1-15 using the composite pipe of the present invention, both of which have a plate thickness of 03 stations, and conventional plate-like materials 1-1 for composite pipes without skin material 5 were produced respectively.

Next, from these plate materials, the parallel length is 10 u.
Cut out a tensile test piece with dimensions of x total length 50cm and a corrosion test piece with plane dimensions: 50mm x 80wn, and place these test pieces in a vacuum of 10-' torr or at
Each test piece was subjected to a heat treatment in which the sample was held at a temperature of 600° C. for 3 minutes in a nitrogen atmosphere of Torr, and then air cooled, that is, heat treated under conditions equivalent to normal flux-less brazing.

In addition, the corrosion test was carried out by a tap water immersion test in which the waxed surface of the test piece was coated with paint and insulated and immersed in tap water containing lppm of Cu2+ ions at a temperature of 40°C for 30 days, and a tap water immersion test in which the waxed surface of the test piece was immersed in tap water containing lppm of Cu2+ ions for 30 days. ct-ioy, So, 2-ion, and HCO3 ion, and l
A solution immersion test was conducted for 30 days in an aqueous solution containing ppm of Cu2+ ions at a temperature of 40°C, and after the test, 40C on the surface of the skin material or core material of the test piece.
The number of pitting corrosion per IIL and the maximum pitting depth were measured. The measurement results are shown in Table 2.

From the results shown in Table 2, it is clear that all of the plate materials 1 to 15 for composite pipes of the present invention exhibit much better pitting corrosion resistance than the conventional plate materials 1 to 5 for composite pipe materials. It is.

As mentioned above, the composite tube material of the present invention exhibits extremely excellent pitting corrosion resistance, especially against aqueous solutions containing Cu ions and Ct ions, so when used as a tube material for a heat exchanger, it has an extremely long service life. It shows.

Applicant: Mitsubishi Aluminum Corporation Agent Tomi 1) Kazuo and 1 other person

Claims (2)

[Claims] (1) On the outside of the core material of A9 alloy containing at least Mn: 0.5 to 1.5 weight coefficient, at least 81.3 to 1
A first sub-pitting corrosion-resistant pipe material characterized by having a three-layer structure by cladding pure AQ skin material on the inside of a two-layer composite pipe material made by cladding with AQ gold alloy brazing filler metal containing 5% by weight. Excellent AP and alloy composite pipe material for heat exchangers. (2) A brazing material of A9 alloy containing at least 3 to 15% by weight of Sl is clad on the outside of a core material of 89 alloy containing at least 0.5 to 15% by weight of Mn.
The inside of the layered composite pipe material is clad with an A1 alloy skin material containing 0.05 to 05% by weight of Zn and the remainder consisting of A and unavoidable impurities to create a three-layer structure. Composite pipe material for heat exchangers made of AQ alloy with excellent pitting corrosion resistance.