JPS59104445A - Copper alloy excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To provide a copper alloy showing good corrosion resistance and weld cracking resistance and also good in solderability, wherein Zn, Sn and Al are contained respectively in predetermined ratios and the remainder comprises Cu and inevitable impurities. CONSTITUTION:A copper alloy contains 25-40wt% Zn, 0.05-1.0wt% Sn and 0.05-1.0wt% Al and comprises the remainder Cu and inevitable impurities. In addition, this copper alloy is obtained by a method wherein the aforementioned copper alloy is subjected to cold rolling in a processing degree of 3-20% after final annealing or adjusted so as to bring the crystal particle size to 0.015min or less by final annealing. This copper alloy has excellent corrosion resistance and is optimum as a material for a heat exchanger such as a condenser, a water supply heater, a distillation vessel, a cooler or a water making apparatus, especially, as the materials of the tank and the fin of the radiator used in an automobile.

Description

Detailed Description of the Invention The present invention is a copper alloy that has excellent corrosion resistance and is used as a material for heat exchangers such as condensers, feed water heaters, distillers, coolers, water supply devices, etc., especially in automobiles, etc. Radiator tank (container).

It relates to copper alloys that are optimal as materials for tubes, fins, etc.

Brass generally has good mechanical properties and formability, and is cheaper than other copper alloys, so it is used in a wide range of applications. Brass is also popularly used in heat exchangers, especially automobile radiators, but depending on the environment, brass can undergo dezincification corrosion, which is a major problem.

Automobile radiators dissipate heat by circulating liquid as a cooling medium between the engine and the radiator in order to adjust the temperature of the two bodies. There is a problem that corrosion occurs from the inner surface of the housing. Further, when the radiator is exposed to exhaust gas, salt-containing coastal air, and even SO and gas in the factory air while the car is running, the radiator is corroded from the outside as well.

The material conventionally used for radiators is copper 6.
Brass consisting of 5 wtl and 35 wtl of zinc is used, but the lifespan of conventional radiators using brass is becoming shorter due to deterioration of the corrosive environment.

Furthermore, in recent years, 2% of radiator tubes have been adopting copper alloy welded tubes made by high-frequency resistance welding or high-frequency induction welding, instead of the conventional swaged lock-seam tubes, in order to reduce costs and improve production efficiency. It's starting to happen. However, copper alloy welded pipes have the disadvantage that the welded part has significantly lower corrosion resistance than other parts due to the uniqueness of its welded structure. This poses a major restriction on the use of copper alloy welded pipes. Furthermore, when high-frequency induction welding or high-frequency resistance welding is used as a welding method when manufacturing copper alloy welded pipes, there is a manufacturing difficulty in that weld cracks are particularly likely to occur due to the characteristics of the welding method.

Under these circumstances, improved corrosion resistance is required for heat exchangers, especially radiator tanks, tubes, fins, etc. At the same time, for welded parts, we are developing materials that are both corrosion resistant and less susceptible to weld cracking. has been desired.

In view of these points, the present invention provides a copper alloy that improves conventional brass and has excellent corrosion resistance as a material for heat exchangers, particularly radiators.

The present invention uses zinc 25 to 40 wt, tin 005 to 1,
Owt 2 aluminum 0.05~1. An alloy containing Owt and the balance consisting of copper and unavoidable impurities.

and an alloy in which the alloy is further cold-rolled with a working degree of 3 to 20% after final annealing, an alloy in which the grain size is adjusted to 0.015 m or less in the final annealing, The present invention relates to a copper alloy having excellent corrosion resistance, which is an alloy which is subjected to final annealing so that the grain size is 0.015W or less, and then cold-rolled at a working degree of 3 to 20 inches.

Next, the reasons for limiting the alloy components and contents constituting the alloy of the present invention will be explained. Copper and zinc are the basic materials of the alloy of the present invention, and have excellent workability, mechanical strength, and thermal conductivity.

The reason why the zinc content is set to 25 to 40 twt% is that if the zinc content is less than 25 wt%, the workability will be poor, and if the zinc content exceeds 40 wtl, the precipitation of β phase in the copper-zinc alloy will be noticeable. This is because corrosion resistance and cold workability deteriorate. The tin content is α05~1.
The reason why it is Owtl is that the tin content is (105wt%).
Less than corrosion resistance.

In particular, when welding, no improvement in the corrosion resistance of the welded part was observed.
Also, 1. This is because the effect becomes saturated when it exceeds Owtl. Aluminum content is 0.05~1. Ow
The reason why the aluminum content is (L O5
When welding to a corrosion resistance of less than 1% wt, no improvement in the corrosion resistance of the welded part was observed.

Also, 1. This is because the effect becomes saturated when it exceeds Owtl.

By adding tin and aluminum in this manner, corrosion resistance is added to the material and the welded part when welded.

Furthermore, the reason why the crystal grain size was limited to 0.015+u or less will be described. Results of investigating the causes of weld cracking caused by high frequency induction welding or high frequency resistance welding 1
The present inventors have discovered that grain boundaries become brittle when in contact with molten base metal, and weld cracking occurs when subjected to a light impact. Therefore, as a result of investigating such phenomena, it was found that the effect of crystal grain size is large and that such phenomena can be significantly suppressed by reducing the crystal grain size.

Furthermore, the present inventors investigated the influence of grain size on corrosion resistance and found that corrosion resistance, especially dezincification corrosion resistance, is affected by grain size. I learned that it is possible. The reason why the crystal grain size is limited to 0015 or less is that the crystal grain size is 0.
If the welding temperature exceeds 0.015, weld cracking is likely to occur, but deterioration of corrosion resistance is still observed.

The reason why the alloy of the present invention is cold rolled at a working degree of 3 to 20 inches after final annealing is that cold rolling improves the solderability of the alloy of the present invention. When the degree of processing is less than 6, no improvement in soldering properties is observed.

In addition, when the ratio exceeds 20, the mechanical strength is high and the crack formability is 1%.
This is because the formability during processing of the radiator tube deteriorates.

The alloy of the present invention exhibits good corrosion resistance and weld cracking resistance, and has good solderability, so it is a material suitable as a copper alloy for heat exchangers, particularly for radiators.

Examples An alloy having the various compositions shown in Table 1 was melted, hot-rolled, annealed as appropriate, and then cold-rolled to a thickness of 1R, and finally annealed at various temperatures. In addition, the crystal grain size was adjusted to be as shown in Table 2. The welded parts to be subjected to the corrosion resistance test were fabricated by butt TIG welding 1M thick alloys of various compositions having the grain sizes shown in Table 2.

Corrosion resistance test was carried out by bathing 1 ton of distilled water with 1.3 y/l of sodium bicarbonate, 1.5 y/l of sodium chloride, and t 6 y/l of sodium chloride, and maintaining the liquid temperature at 88°C at a rate of 100 per minute. - air was blown into the sample, and the sample was immersed in this solution for 500 hours. The maximum dezincification corrosion that occurred at that time was measured for the welded part and the base metal part, and the corrosion resistance was evaluated based on this. The results are shown in Table 3.

The second test was for resistance to weld cracking caused by embrittlement of grain boundaries when in contact with molten base metal.
Alloys of various compositions with the grain sizes shown in the table are processed into pipe shapes as shown in Figure 1, immersed in molten metal of the same composition maintained at +50°C melting point for 3 seconds, and then taken out. While the attached metal was melted in the holding furnace, an impact was applied as shown in Figure 2.

The cross section of the deformed pipe was then observed under a microscope to confirm the presence or absence of intergranular fracture, and this was used to evaluate resistance to weld cracking. The results are shown in Table 4.

Further, alloys having a thickness of 1/2 inch and having the grain size shown in Table 2 were cold rolled at the working degree shown in Table 5, and then subjected to a soldering test. For soldering, the diameter is a80wA.
, Sn20wt%-Pb8 in a cylindrical crucible with a depth of 60mm.
0wt% solder was heated to 520℃ to create a molten metal, and when a sample (with a clean surface and a shape of 10U in width and 50cm in length) was immersed in the molten metal at a descending rate of 25W/sec, the melt was removed from the solder bath. The time required for the buoyant force exerted on the sample and the force drawn into the solder bath to reach equilibrium was measured, and the soldering properties were evaluated based on this. The results are shown in Table 6.

As can be seen from Tables 5, 4, and 6, the alloy of the present invention exhibits excellent corrosion resistance against dezincification corrosion in the raw material and welded parts, and also exhibits excellent weld cracking resistance and soldering resistance. was also found to be a good alloy.

That is, for the comparative alloys (sample numbers 1 to 6), the maximum dezincification corrosion depth was 213μ to 667μ.

In contrast, the alloys of the present invention (sample numbers 7 to 23) have a minimum value of 20 μ to a maximum value of 90 μ in the raw material, a minimum value of 54 μ to a maximum value of 137 μ in the weld, and have good dezincification corrosion resistance. It turns out that it is excellent. Among the alloys of the present invention, alloys with a grain size of 0.015w or less are
Excellent resistance to dezincification and corrosion.

The alloy of the present invention has excellent dezincification corrosion resistance as described above, but it also has a crystal grain size of O, O15 or less (sample number 7.8.9.12.14.15°16. 1
a, 19.21.23), the weld cracking resistance shown in FIG. 2 is simply ductile deformation, no cracking occurs, and the weld cracking resistance is improved. On the other hand, a crystal grain size exceeding 10,150 is not preferable because it causes grain boundary fracture.

Furthermore, among the alloys of the present invention, those that were cold-rolled with a workability of 3 to 20% (sample numbers 7 to 16) and those that were not cold-rolled (sample numbers 17 to 23) were soldered. Compared to the comparatively long time of 205 seconds to 2.20 seconds required for evaluating the properties of the sample (depending on the time it takes for the buoyant force exerted on the sample from the solder bath and the force drawn into the solder bath to reach equilibrium), it is possible to achieve equilibrium in a shorter time. It can be seen that the soldering properties are excellent.

As described above, the alloy of the present invention has extremely excellent properties as a copper alloy for use in 1% heat exchangers and radiators.

Table 1 (Unit: wt) Table 2 Table 3 Table 4 Table 5 Table 6

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an alloy pipe having a thickness of 1H used for testing weld cracking resistance, and FIG. 2 is a schematic illustration of a weld cracking resistance testing apparatus. 1: Alloy pipe with thickness 10 (length 10 yur) 2:
Free falling object (weight 200 gw) 6: Support stand 4: Heating and holding furnace a: Pipe inner diameter (z2oIIJ) b: Pipe outer diameter (022 m) C: Falling distance of falling object 2 (50 m) Patent applicant Nippon Mining Co., Ltd. Agent Patent Attorney (7569) Keishi Namikawa

Claims (4)

[Claims] (1) Zinc 25-40wt, tin 0.05-1.
Owt%. Aluminum 0.05~1. Copper alloy with excellent corrosion resistance, containing 50% by weight, the balance being copper and unavoidable impurities. (2) Zinc 25-40 wt%, tin 005-1 which was further cold-rolled with a working degree of 3-20 inches after final annealing.
．． A copper alloy with excellent corrosion resistance, containing 0.05 to 1.0 wt% of aluminum, and the balance being steel and unavoidable impurities. (3) Zinc 25-40 wt%, tin 005 adjusted so that the grain size is [1,015 m or less] in the final annealing
~1. Owt 俤, aluminum 005~1.0wt5
A copper alloy with excellent corrosion resistance, consisting of copper and unavoidable impurities. (4) Zinc 25-40wtqII which was adjusted to have a grain size of 0.015w or less by final annealing, and then further cold-rolled at a workability of 3-20mm. Tin 105~1. Owt96, aluminum α05~
A copper alloy with excellent corrosion resistance that contains 1.0 so, tS, and the remainder is copper and unavoidable impurities.