JPS6082631A - Copper alloy having superior corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a Cu alloy consisting of prescribed percentages of Zn, P, Sn, Al and As and/or Sb and the balance Cu with inevitable impurities and having superior corrosion resistance, weld crack resistance and high solderability. CONSTITUTION:This Cu alloy consists of, by weight, 10-40% Zn, 0.005-0.070% P, 0.05-1.0% Sn, 0.05-1.0% Al, 0.005-0.2% in total of 0.005-0.1% As and/or 0.005-0.1% Sb, and the balance Cu with inevitable impurities. The weld crack of the Cu alloy can be prevented by regulating the grain size to <=0.015mm. by final annealing. The solderability of the alloy is improved by cold rolling the alloy at 3-20% draft after the final annealing. The Cu alloy is most suitable for use as the material, especially of tank, tubes, fins, etc. of a radiator for an automobile or the like.

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, and water generators, especially in automobiles. This article relates to copper alloys that are optimal as materials for radiator tanks, tubes, fins, etc.

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

Automobile radiators use button liquid as a cooling medium to circulate the engine and radiator to dissipate heat in order to adjust the temperature of the engine body.The radiator is in constant contact with the cooling medium, and this cooling medium can cause corrosion from the inside. There is a problem that arises. Furthermore, when the radiator is exposed to exhaust gas, salt-containing coastal air, and even EI02 gas from factory air while the car is running, it corrodes from the outside as well.

The material traditionally used for radiators is copper 65.
Brass containing 35 wt% zinc and 35 wt% zinc is used, but the corrosive environment deteriorates.

The lifespan of traditional brass radiators is becoming shorter.

Furthermore, in recent years, copper alloy welded pipes made by high-frequency resistance welding or high-frequency induction welding have been adopted, especially for radiator tubes, in place of the conventional lock-seam tubes made by caulking, from the standpoint of cost reduction and production efficiency. It's becoming a trap. 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 @alloy welded pipes, there is a manufacturing drawback in that weld cracks are particularly likely to occur due to the characteristics of the welding method.

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

The present invention addresses this problem, improves conventional brass, and provides a copper alloy having excellent corrosion resistance as a material for heat exchangers, particularly radiators.

The present invention contains zinc 10-40 wt%, phosphorus 0.005-0,
070 wt%, tin 0.05-1. Owt, aluminum 0.05-1. Including Owt, and 0 arsenic
．． 005-0.1 wt%, antimony 0.005-0
．． A total of 1 or 2 types of 1wt% 0005 to 0
．． Contains 2wt%.

An alloy consisting of the remainder copper and unavoidable impurities, an alloy in which the crystal grain size is adjusted to 0.015 m or less in the final annealing, and the alloy is cold rolled at a workability of 3 to 20% after the final annealing. After the alloy was subjected to the following steps, and the alloy was subjected to final annealing so that the grain size was adjusted to 0.015 mm or less.

Furthermore, the present invention relates to a copper alloy that is cold-rolled with a working degree of 3 to 20 qb and has excellent corrosion resistance.

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 10 to 40 wt% is that if the zinc content is less than 10 wt%, the workability will deteriorate, and if the zinc content exceeds 40 wt%, the precipitation of β phase in the copper-zinc alloy will occur. This is because corrosion resistance and cold workability deteriorate. Phosphorus content 0.005-0.07
The reason why it is classified as 0wt is that the phosphorus content is 0.005w.
This is because when the content is less than t%, corrosion resistance is improved, but signs of grain boundary disease are observed. On the other hand, the phosphorus content is 0.070
This is because, although corrosion resistance is improved when the content exceeds w-t'ly, signs of grain boundary disease are observed. Tin content is 11.0
This is because if the content is less than 5 wt%, no improvement in corrosion resistance, especially of the welded part when welded, will be observed, and if it exceeds 1.0 wt%, the effect will be saturated. Aluminum content is 005-1. The reason for setting it as Owt% is.

This is because if the aluminum content is less than 1, o s wt1, no improvement in corrosion resistance, especially of the welded part when welded, will be observed, and if it exceeds 1,0 s wt14, the effect will be saturated. Furthermore, the content of arsenic is 0.005 to 0.
The reason why it is classified as 1vt is that the arsenic content is Q, OO5w
This is because if it is less than t%, no improvement in the corrosion resistance of the welded part will be observed when welding to a corrosion resistance of 1%, and if it exceeds 0.1w, the effect will be saturated. Antimony content 0.0
05 to 0.1wt4 is because if the antimony content is less than 0.005wt%, there is no improvement in corrosion resistance, especially in the welded part when welded, and [1.1
This is because the effect becomes saturated if it exceeds wt%.

As mentioned above, by adding phosphorus, corrosion resistance is added to the material, and it can be used to improve the corrosion resistance of tin, aluminum, and arsenic.

By adding antimony, corrosion resistance is added to the material and the welded part when welded.

Furthermore, the reason why the crystal grain size is limited to α015rtan or less will be described. As a result of investigating the causes of weld cracking caused by high-frequency resistance welding or high-frequency resistance welding, the present inventors found that when in contact with molten base metal, the grain boundaries become brittle, and when subjected to a light impact, weld cracking occurs. We found that this occurs. 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, as a result of investigating the influence of grain size on corrosion resistance, the present inventors found that corrosion resistance, especially dezincification corrosion resistance, depends on grain size, and that corrosion resistance can be improved by reducing grain size. .

The reason why the crystal grain size was limited to 0.015+Mn or less.

This is because if the crystal grain size exceeds 0.015 mm, weld cracking is likely to occur, and deterioration of corrosion resistance is observed.

Furthermore, the reason why the alloy of the present invention is cold rolled with a workability of 3 to 20% after final annealing is that cold rolling often improves the soldering properties of the alloy of the present invention. If the degree of processing is less than 3, no improvement in soldering properties will be observed, and if it exceeds 20, the mechanical strength will be high and the formability, especially when processing the radiator tube, will deteriorate.

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

Examples Alloys having the various compositions shown in Table 1 were melted, hot rolled and appropriately annealed, then cold rolled to form a plate with a thickness of 1 mm, and finally annealed at a high temperature as shown in Table 2. The grain size was adjusted to be as shown in . The strength was evaluated by tensile strength and elongation, and the results are shown in Table 3. The welded parts to be subjected to the corrosion resistance test were fabricated by butt T welding of alloys of various compositions having the crystal grain sizes shown in Table 2 and having a thickness of 1 dew. Corrosion resistance test: 1 ton of distilled water with sodium carbonate 1.3
f Sodium sulfate 1.5f Sodium chloride 1662 dissolved liquids were maintained at a temperature of 88°C, and the flow rate was 100 tons per minute.
nl of air was blown into the sample, and the sample was immersed in this solution for 500 hours. The maximum dezincification corrosion depth 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 4.

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 5.

Furthermore, the alloys having a grain size shown in Table 2 and having a thickness of one plate were cold rolled at the working degree shown in Table 6, and then subjected to a soldering test. Soldering test is 80111 diameter
I+1. Sn 20w in a cylindrical crucible with a depth of 60w+
Solder consisting of t%-Pb 80 wt was heated to 360°C to create a molten metal, and a descending speed of 25 m /
Sample in sec (width 1.0+++ with surface cleaned)
The time required for the buoyant force exerted on the sample from the solder bath and the force drawn into the solder bath to reach equilibrium was measured when the sample was immersed in the sample (shape of 50 m long), and the soldering properties were evaluated based on this measurement. The results are shown in Table 7.

As can be seen from Table 6, Table 4, Table 5, and Table 7, the alloy of the present invention exhibits excellent corrosion resistance against dezincification corrosion in the raw material and in the welded part when welded, and also has improved strength. The alloy was also found to have good weld cracking resistance and soldering properties.

That is, in the comparison alloys (sample numbers 1 to 5), the maximum dezincification corrosion depth was 211 to 361 μm.

Whereas it reaches 620-719μ in the welded part.

It can be seen that the alloys of the present invention (sample numbers 6 to 15) have a minimum value of 29μ to a maximum value of 79g, and a minimum value of 67μ to a maximum value of 160μ in the welded part, and are excellent in dezincification corrosion resistance. Among the alloys of the present invention, alloys with a grain size of 0.015 m or less have better dezincification corrosion resistance.

In addition, the comparative alloys (sample numbers 1 to 5) had a tensile strength of 34
~37 breasts/-, whereas 1 inventive alloy (sample no. 6
It can be seen that the strength of samples 15) to 15) is improved to 42 to 48 Kf/-.

In addition, the alloy of the present invention has excellent dezincification resistance and corrosion resistance 2 strength as described above, but in addition, the alloy with a grain size of 0.015 or less (sample number 7.11.12) is shown in Figure 2. In the weld crackability test, the weld crackability is improved by simply undergoing ductile deformation without cracking. On the other hand, if the grain size is 0. If it exceeds OfS, it is not preferable because it causes grain boundary destruction.

Furthermore, among the alloys of the present invention, those that were cold-rolled with a workability of 3 to 20 (sample numbers 6-12) and those that were cold-rolled (sample numbers 13-15) had poor soldering properties. (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) compared to the relatively long time of 2.22 to 2-30 seconds. It can be seen that equilibrium is reached and the soldering properties are excellent.

As described above, the alloy of the present invention has extremely excellent properties for use in heat exchangers, especially radiators.

Table 1 (Unit wt section) Table 2 Table 3 Table 4 Chapter 5 Shishi Table 6 Table 7

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an alloy pipe with a thickness of 1 mm used for the weld cracking resistance test, and FIG. 2 is a schematic explanatory diagram of the weld cracking resistance testing apparatus. 1. Alloy pipe with 1 piece thickness (length 1OW) 2: Free falling body (weight 200gW) 3: Support stand 4: Heating and holding furnace a; Pipe inner diameter (σ20) b: Pipe outer diameter (e22) C : Falling distance of falling object 2 (50 clauses) Patent applicant: Japan Mining Co., Ltd. Patent attorney (7569) Keishi Namikawa Figure 1

Claims (4)

[Claims] (1) Zinc 10-40wt, phosphorus 0.005-α07
0Wtchi. Anchor Q, 05~1.0 wt, aluminum 0.05~
1. Contains Owt, and further contains arsenic 0.005~[1,
jwt staff. Antimony 0.0 (within 15-0.1wt%)
A copper alloy with excellent corrosion resistance, containing one or two species in a total amount of 0.005 to 0.2 wt%, and the balance being steel and unavoidable impurities. (2) The grain size becomes 0.015wn or less in the final annealing.
Zinc 10-40 wt%, phosphorus o, o
os~0.07 Owt, tin 0.05~1.0. lol
t ratio, including aluminum 0.05 to t wt4,
In addition, 0.005 to 0.1 wt% of purple violet and 0.0% of antimony.
A total of 0 of any one or two of 005 to 0.1 wt%
．． A silver alloy with excellent corrosion resistance, containing 005~o, 2 wtfo, and the balance being copper and unavoidable impurities. (3) After final annealing, the crystal grain size was adjusted to α015 or less, and then cold-rolled at a working ratio of 3 to 20, containing 10 to 40 wt% zinc and 0.00 phosphorus.
A copper alloy with excellent corrosion resistance, containing a total of 5 to 0.070 wt, 0.05 to 1.0 of tin, and a total of 2 types of o, oos to o, 2 wtqb, and the balance being copper and unavoidable impurities. (4) Zinc 10-40 wt%, phosphorus Q, 0 which was further cold-rolled with a working degree of 3-20% after final annealing.
05~Q, D70 wt%, Tin 0.05-t D
wt%. Aluminum 0.05-1. Contains Ovzt%, and further contains arsenic α005~0.1wt, antimony 0005~
0, 1 wt% of any one or two types in total 0005 ~
A silver alloy with excellent corrosion resistance that contains 0.2 wtl and the balance is copper and unavoidable impurities.