JPS59153854A - Copper alloy with superior corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a Cu alloy with superior corrosion resistance as a material for a heat exchanger by adding specified percentages of Zn, P, Sn, Ni, Fe and Pb to Cu. CONSTITUTION:A Cu alloy consisting of, by weight, 25-40% Zn, 0.005-0.070% P, 0.05-1.0% Sn, 0.05-2.0% Ni, 0.005-1.3% in total of 0.005-1.0% Fe and/or 0.005-0.3% Pb and the balance Cu with inevitable impurities is prepd. The grain size of the alloy may be adjusted to <=0.015mm. by final annealing, and/or the alloy may be cold-rolled at 3-20% draft after final annealing. An alloy showing high solderability as well as high corrosion resistance and weld crack resistance is obtd.

Description

Detailed Description of the Invention The present invention is a copper alloy with excellent corrosion resistance, which is used as a material for heat exchangers such as condensers, feed water heaters, distillers, coolers, and water generators, especially in automobiles. 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. It is also popularly used as a radiator for automobiles.

Depending on the environment, brass may experience dezincification corrosion.

This is the problem of thickness.

An automobile radiator dissipates heat by circulating liquid as a cooling medium between the engine and the radiator in order to adjust the temperature of the main body.The radiator is in constant contact with the cooling medium, and this cooling medium causes There is a problem that corrosion occurs from In fact, if a radiator is exposed to exhaust gas, salty coastal air, or even SO gas from a factory atmosphere while the car is running, it will corrode from the outside as well.

Materials conventionally used for radiators are @6
Brass made of S wt and zinc 35 wt4 is used, but the lifespan of conventional radiators using brass is becoming shorter due to deterioration of the corrosive environment.

Furthermore, in recent years, especially in radiator tubes,
Copper alloy welding using high-frequency resistance welding or high-frequency induction welding has come to be used instead of the conventional lock seam tube using crimping to reduce costs and improve production efficiency. 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, high frequency induction welding is also used as a welding method when manufacturing copper alloy welded pipes.
When high frequency resistance welding is used, weld cracks are particularly likely to occur due to the characteristics of the welding method, which is a manufacturing drawback.

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

In response to this demand, many attempts have already been made to add additive elements to brass to improve its corrosion resistance.
So far, no material has been found that exhibits excellent corrosion resistance against corrosion from both the inner and outer surfaces.

In view of this, the present invention provides a copper alloy having excellent corrosion resistance as a material for heat exchangers, particularly radiators.

The present invention has zinc of 25 to 40 vyt and phosphorus of 0.005 to 0.
, 070 wt, tin 0.05-1. Owt section, nickel 0.05-2. Including Owt staff, Sarakakutetsu 0.0
05~1, Owt, lead 0.0 O5~0.5 wt
The total amount of 1 or 2 types of inner surface cracks is 0.005 to 1.
3 Including wt staff.

An alloy consisting of the remainder copper and unavoidable impurities, an alloy in which this alloy is further cold-rolled at a working degree of 3 to 2 degrees after final annealing, and an alloy in which the grain size is reduced to 0.
After adjusting the alloy so that the grain size is 0.015F or less, and the alloy' IC final 41f, the alloy is dull and adjusted to have a grain size of 0.015F or less, it is further cold rolled with a working degree of 3 to 20%. The present invention relates to a copper alloy that has been processed and has excellent corrosion resistance.

Next, the reasons for limiting the alloy components and contents forming 47' of the alloy of the present invention will be explained. Copper and zinc are the basic materials for the alloy of the present invention, and they have excellent workability and mechanical strength.
It also has excellent thermal conductivity.

The reason why the zinc content is set at 25 to 40 wt.

If the zinc content is less than 25 wtef6, the workability will deteriorate, and if the zinc content exceeds 40 wt%, copper-
This is because precipitation of β phase is observed in the zinc alloy Kf6, resulting in poor corrosion resistance and cold workability. 00 phosphorus content
The reason for setting 05 to 0.070 Wt96 is that no improvement in corrosion resistance is observed when the phosphorus content exceeds 0.005 wt%, whereas corrosion resistance is improved when the phosphorus content exceeds 0.070 wt%. This is because signs of grain boundary disease can be seen. The reason for setting the tin content to 0.05 to 0.05 wt.
This is because the effect becomes saturated when the value exceeds o wd.

The reason why the nickel content k is 0.05 to 2; If it exceeds 1, the effect will become saturated. The iron content is 0.0 O5 to 1. Ow
The reason for setting it as t% is that if the iron content is less than 0.005 wt%, no improvement in corrosion resistance will be observed, and if it exceeds 1.0 wt%, the effect will be saturated. The reason why the lead content is set to 0.005 to 0.3 wt% is that if the lead content is less than 0.005 wt%, no improvement in corrosion resistance is observed, and if it exceeds 0.5 wt%, workability deteriorates. It is no use.

As mentioned above, corrosion resistance is added to the material by adding phosphorus, iron, and lead, and when the material is welded by adding tin and nickel.

This adds corrosion resistance to the weld.

Furthermore, the reason why the crystal grain size 'r is limited to 0.015 mm or less will be explained. As a result of investigating the causes of weld cracking caused by high-frequency resistance welding and high-frequency induction welding, the present inventors found that grain boundaries become brittle when in contact with molten base metal, and welding occurs when subjected to a light impact in a warehouse. It was discovered that cracks occur. As a result of various investigations into such phenomena, it has been found that such phenomena can be significantly suppressed by reducing the crystal grain size. Furthermore, the present inventors also investigated the effect of grain size + vvK, which does not affect corrosion resistance, and found that corrosion resistance, especially dezincification corrosion resistance, is affected by grain size.Corrosion resistance can be improved by reducing grain size. I found out that it is possible. The reason why the grain size is limited to 0.015m++ or less is that if the grain size exceeds 0.015wnn, weld cracking is likely to occur and deterioration of corrosion resistance is observed.

In addition, after final annealing of the alloy of the present invention, an additional 3 to 20%
The reason why cold rolling is performed at a working degree of No improvement in properties was observed, and if it exceeded 20 inches, the mechanical strength would become too high and the workability during radiator duplex molding would 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 inch, and finally annealed at various temperatures to form a second plate. The grain size was adjusted as shown in the table. The welded parts to be subjected to the corrosion resistance test were fabricated by T-welding and welding alloys of various compositions having grain sizes shown in Table 2, each having a thickness of 1 mm, butted against each other. Corrosion resistance test was conducted using sodium bicarbonate in 1 ton of distilled water.
1.3 t/t of sodium sulphate 5v/l.

Sodium chloride 1. '6 y/l of each solution was kept at a temperature of 88°C, and the rate was 100% per minute.
- 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 3.

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

The cross section of the pipe deformed at that time was observed under a microscope to confirm the presence or absence of two-grain boundary fracture, and this was used to evaluate the resistance to weld cracking. The results are shown in Table 4.

Further, after cold rolling an alloy of one thickness with the grain size shown in Table 2 at the working degree shown in Table 5, it was subjected to a soldering test. Sn 20wt-Pb in a cylindrical crucible with a diameter of 80mm and a depth of 60mm
80 wt of solder was heated to 320°C to create a molten metal, and a sample (with a clean surface) was placed into the molten metal at a falling speed of 25 m/sec.
The buoyancy force that the sample receives from the solder bath when it is immersed in the solder bath.

The time required for the force drawn into the solder bath to reach equilibrium was measured, and the soldering performance was evaluated based on this measurement. The results are shown in Table 6.

As can be seen from Tables 3, 4, and 4, the alloy of the present invention exhibits excellent corrosion resistance against dezincification corrosion due to the material and welded parts (1), as well as weld cracking resistance and The alloy was found to have good soldering properties.

That is, for the ratio-axis alloys (sample numbers 1 to 10), the f1 dezincification corrosion depth in the base metal is 235μ to 396μ.

In contrast, the alloys of the present invention (sample numbers 11 to 25) have a minimum value of 26p-m in the base metal and a high value of 96μ, and a minimum value of 63μ to a maximum value of 180μ in the welded part, indicating dezincification corrosion resistance. It can be seen that it is excellent. Among the alloys of the present invention, alloys with a grain size of 0.015 m+++ or less have better dezincification corrosion resistance.

The alloy of the present invention has excellent dezincification corrosion resistance as described above, but the alloy with a grain size of 0.015 or less (sample number 12.14.16.1a20) is shown in Figure 2. In tests for weld cracking resistance, the weld cracking resistance is improved, with only ductile deformation and no cracking. On the other hand, if the crystal grain size exceeds 0.015 grains, grain boundary failure will occur, so this is not a good choice.

Furthermore, among the alloys of the present invention, those that were cold-rolled with a working degree of 3 to 20 inches (sample numbers 11-19) and those that were not cold-rolled (sample numbers 20-23) had a low soldering temperature. Compared to the comparatively long time of 2.23 seconds to 2.40 seconds in evaluation (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 much shorter. It can be seen that equilibrium has been 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 2 Third? Part 4 7 Table 5 Table 6

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an alloy pipe of one thickness used for testing weld cracking resistance, and FIG. 2 is a schematic illustration of a weld cracking resistance testing apparatus. 1: Alloy pipe with 1 gate thickness (length 10F11) 2: Free falling body (200 section W of mold bone) 3: Support stand 4; Heating and holding furnace a,: Pipe inner diameter (σ20 gates) b: Pipe outer diameter ( (22 gates) C: Falling distance of falling object 2 (50 gates) Patent applicant Nippon Koryoku Co., Ltd.

Claims (4)

[Claims] (1) Zinc 25-40wt, phosphorus 0.005-0
．． 070wt person. Tin 0.05-1. Owt section, nickel 0.05-2.
Including Owt, and further iron 0.005~1. Owt
Person in charge. A copper alloy with excellent corrosion resistance, which contains one or two types of inner grains of 0.005 to 0.3 wt'l of lead in a total amount of 0.005 to 1.3 wt, and the balance is copper and unavoidable impurities. (2) Grain size is less than 0.015 mm in final annealing ~2. Contains Owt4 and further contains iron [1,oo5~1
．． . wt person, lead 0. OO5~o, 3wt type inner layer contains one or two types in total amount of 0.005~t3wt type. A copper alloy with excellent corrosion resistance consisting of the balance copper and unavoidable impurities. (3) After the final annealing, cold rolling was further performed at a working degree of 3 to 20 wte4. Zinc 25-40 wt4
. Phosphorus O, OO5~0.070 wt, tin 0.05~1
．． Owt%, nickel 0.05-2. Including Owt section, and further iron 0. OO5~t Owt section, lead 0.00
Total amount of 1 or 2 types of 5 to 0.3wt inside 0
．． A copper alloy with excellent corrosion resistance, containing 0.005 to 1.3 wt, the balance being copper and unavoidable impurities. (4) After final annealing, the grain size was adjusted to 0.015 mm or less, and then cold rolling was performed at a working ratio of 3 to 20. Zinc 25-40wt, phosphorus 0.00
5~0.070wt, tin 0.05~1, Owt,
Nickel 0.05~2. Including Owt staff. Furthermore, iron 0.0 O5~1. Owt section, lead 0.0 O
A copper alloy with excellent corrosion resistance, containing one or two of the inner side of 5 to 0 and 5 wt in a total amount of o, o o s to t s wt, and the balance being steel and unavoidable impurities.