JPS58130244A - Aluminum alloy for tube of heat exchanger - Google Patents

Abstract

PURPOSE:To provide the titled Al alloy consisting of prescribed percentages of Cu and B and the blance Al with inevitable impurities, capable of being easily hot extruded, and enhancing the surface state and pitting corrosion resistance of tubes. CONSTITUTION:This Al alloy for the tubes of a heat exchanger consists of 0.2- 1.0% Cu, 0.003-0.05% B and the balance Al with inevitable impurities. By further adding <=0.08% Ti to the alloy, the grains of the alloy are made fine and the surface roughening of the bent parts of the tubes can be prevented. The total amount of Fe and Si as inevitable impurities are restricted to <=0.5% to prevent the deterioration of the pitting corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention can be combined with sacrificial anode fins by brazing;
Tube constituting a heat exchanger, Special C: This relates to an aluminum alloy that can be easily hot extruded as a tube material formed by hot dark extrusion, and has a good tube surface condition and pitting corrosion resistance.

It consists of an aluminum tube and cooling fins on the air side, which are generally assembled by brazing, and are usually joined to the fins by brazing using a plating sheet. Such a heat exchange Pi! For example, in serpentine type car cooler condensers and evaporators, A 3003 (AI -0,
15wt%Cu-12wt%N.

Hereinafter, wt% is simply abbreviated as %) V core material is used, A4004 (
AI-10%8i-1,5%Mg) or A4343(
AI-7,5%5i) Clad board made of v skin material? use,
A1050 (pure 1f99.5% or more pure AI) in the tube
) was formed by hot extruding an extruded tube (IIV was used, with a meandering shape as shown in Fig. 2 A corrugated plating sheet (21) is inserted between the bent tube (11) and joined by brazing.

When these heat exchangers are used in a severely corrosive environment, pitting corrosion progresses in a short period of time, so their use is severely restricted. Pitting corrosion occurs when the fins and their brazed parts become electrically sensitive, and the tube selectively corrodes as the tube passes from the tube side through the electrolyte V to the fin side. It is okay for the fins to corrode to some extent, but if the tubes suffer through pitting corrosion, the refrigerant will leak, which is a fatal defect for the heat exchanger. In order to prevent this, a so-called sacrificial anode fin was proposed in which an element V such as 8n or Zn was added to the core material or skin material of the plating sheet that became the fin, making the potential of the fin less noble than that of the tube, and it was not put into practical use. ing.

The potential of the sacrificial anode fin is -800 mv or less based on a saline saturated calomel electrode at 25°C, and the potential of the tube is A.
-79 at 1050 (Ev Al 1@Al -0,05
~0.20%Cu) gives -78 OnlF, and A3003 gives -720 mV.

Therefore, the tube has the largest electric current difference A with the fin.
3003 is preferable; A1050 and Al100 have difficulty in pitting corrosion resistance due to the potential relationship with the fins. Also, A3003, Mu105G, and Al100 all have problems in extrusion processability.In particular, A3003 has a higher strength than Mu105° and Al100, so the extrusion speed is low and the processing cost is low. ) or extrusion] - the surface condition was the poorest.

In view of this, one of the present inventors has conducted various research and found that when combined with a sacrificial anode fin, it exhibits pitting corrosion resistance equivalent to that of A3003, and extrusion processability of aluminum alloy V equivalent to A105 (J and Al100). Development 17 was proposed.This alloy is filled with CuO, 2-10%, and the balance consists of A1 and unavoidable impurities.
Extrusion processability equivalent to '? A1050 and Al1
Similar to 00, roughness (hereinafter referred to as pickup) and die marks appear on the surface during extrusion, and when bending the tube, roughness occurs on the surface of the bent part due to relatively large crystal grains. It had some drawbacks.

The present invention is based on the results of further studies on the above A I-0.2 to 1.0% Cu. By adding H)) to the intermetallic alloy, the pitting corrosion resistance when combined with sacrificial m & fins is reduced. The company discovered that the extrusion processability could be improved, and developed an aluminum alloy V for heat exchanger tubes that prevents pickup and die marks from occurring during extrusion.

Section 1 The alloy of the present invention is characterized in that it contains 2 to 1.0% of CuO, 0.03 to 0.05% of Bo, and the remainder consists of AI and inevitable impurities.

Another alloy of the present invention contains 0.2 to 10% Cu and 0.003 to 0.005% H, and further contains '1'' i 0.O.
It is characterized by consisting of the remainder AI and unavoidable impurities.

(2) The composition of the alloy of the present invention is limited as shown in J Pi above for the following reasons.

The purpose of adding CLI is to increase the potential of the alloy and obtain excellent pitting corrosion resistance when combined with a sacrificial anode fin.If the Cu content is less than 0.2%, the potential of the alloy cannot be maintained at a high level. First, if the content exceeds 1.0%, not only the effect of knitting potential v will be saturated, but also the hot extrudability will be low FT. Also B
The purpose of this addition is to prevent pickup and die marks from occurring during hot extrusion without changing the potential of the alloy.
B is dispersed in the alloy and has the effect of polishing the die bearing part (forming part of the tube shape and size) during hot extrusion.A tube with a sharp surface can be obtained, and a large number of billets V2 can be obtained. ! ! ! The effect is smooth when extruding continuously),
Furthermore, B refines the crystal grains and prevents rough skin V at the first stop of the duplex for assembling the heat exchanger, but if the B content is less than 0D03%, the effect is small, and if the B content is less than 0D005%, This is because not only the effect is saturated, but also the wear of the tool when cutting the tube during hot hardening is significantly increased. Furthermore, Ti is used to refine the crystal grains of the alloy and prevent roughness at the bent portion of the tube.Although the effect increases with the amount of Ti added, if the 'l'1 content exceeds 008%. This is because as the effect reaches saturation, brazing begins to have a negative impact on sex. In addition, TI is intergold compound '1
When added in the form of '1t(2), it is possible to greatly increase the grain refinement effect of the 1 alloy.

Fe and 8i contained in AI bullion are impurities that exist in the metal, and although they can be tolerated to some extent,
If the sum of e and Si exceeds 0.5%V, the pitting corrosion resistance of the joint will decrease.It is desirable to limit the sum of FC and St to 0.5% or less.

In addition, other unavoidable impurities 1 such as Mg, Mn, Zn
, Cr, Zr, etc. are contained in ordinary metals to an illusory extent, but do not impair the effects of the alloy of the present invention.

Examples of the alloy of the present invention will be described above. An aluminum alloy billet (O diameter 175 - length 400 Ill) shown in Table 1 with a composition T was water-cooled cast, and after homogenization treatment at a temperature of 520 ° C. for 3 hours, Hot extrusion was carried out at a temperature of 450°C to form a deformed tube (separation 07■,
A width of 106 m, an island size of 5 cm, and 26 holes were created. During extrusion, each component was extruded five times in succession [7, and the extrusion speed and surface condition (plate portion of the extruded material) were observed for the last five grains. In addition, for each different alloy composition, extrusion-I
I prepared the dice for J.

The irregularly shaped tube thus extruded was bent into a meandering shape like a T-tube (1) shown in FIG. 2, and the surface condition of the bent portion was observed. These results are shown in Table 2.
.

In addition, as shown in Fig. 2, an extruded irregularly shaped tube (I
Sacrifice 1111 bent into a meandering shape and formed into a wave shape on the tube n11! Charge the pole fin (2) 17, and braze in the air (5XlO-'Torr, 600℃, 1 minute)
A simulated heat exchanger core was prepared using l-, and about this simulated core, dichloromethane was added to a vinegar solution of sodium chloride.
Perform a CASS test using the added solution and find out how long it takes for pitting to penetrate the side wall of the tube. Side pressure.

The pitting corrosion resistance was compared. In addition, the potential of the tube and fin was set to vI1gi in a 5% NaCl aqueous solution. The results of h4 are also listed in Table 2.

Incidentally, the sacrificial anode was made of AI-11%Mn-0,n
A 6%8nQ, 5%Zn alloy plate was used as a core material, and both sides of the core material were clad with Al-1θ%8i-1,5%Mg alloy plates, thickness Q, and a brazing rate of 15 m.

As is clear from Tables 1 and 2, compared to the conventional alloy (AI-Cu, 418), the alloys of the present invention have the same or better hot extrudability and the same pitting corrosion resistance [2 , The surface condition after extrusion is much better, and the surface condition of the tube bending part is also excellent.11. Although the hot extrusion speed is somewhat lower than that of the conventional alloy (A105 (LA16)), the surface condition after extrusion,
Much better pitting corrosion resistance and surface condition after bending. Furthermore, compared to the conventional composite* (A300 Å417), it can be seen that the pitting corrosion resistance and the surface condition of the curved portion of the tube are almost the same, and the extrusion speed and surface condition after extrusion are far superior.

[1] Comparative alloy All with less Cu content than the composition range of the present alloy has a significant decrease in pitting corrosion resistance;
Comparative alloy 412, which has a high u content, has deteriorated extrusion speed and surface condition after extrusion.

Comparative alloy 413, which has a low B content, had poor surface condition after extrusion, and comparative alloys /1614 and I, which had a high B content, had poor surface conditions after extrusion.
Comparative alloy No. 15, which has a high I content, has almost the same pitting corrosion resistance and hot extrudability.

It was difficult to cut when creating the simulated core, and the brazing properties were significantly reduced, making it impossible to obtain good brazing.

In this way, the alloy of the present invention can obtain an excellent surface condition without leaving pick-up or die marks on the tube surface during hot extrusion, has good extrudability, and can be used to bend the tube without causing rough skin. In addition, it has excellent pitting corrosion resistance, and has remarkable effects as a part of the heat exchanger.

[Brief explanation of the drawing]

The first factor (a) and (C4, shi) respectively indicate heat exchanger tubes, (a) is a perspective view of an extruded tube with three refrigerant passages, and <C4 is a perspective view of an extruded tube with 11 cold tofu passages. 1 is a perspective view of an extruded tube provided with 26 refrigerant passages, and FIG. 2 is a perspective view showing an example of a heat exchanger core.

Claims (1)

[Claims] tll CuO, 20-1.0w1% and 80.003
An aluminum alloy for heat exchanger tubes containing ~0.05 wt% and the remainder consisting of Al and unavoidable impurities. (21CuO, 20~1.0w1% and Bo, 003~Q
An aluminum alloy for heat exchanger tubes containing 5wt% of G, further containing 98w1% or less of TiQ, and the balance being AI and unavoidable impurities.