JPS6230862A - Manufacture of copper alloy having superior corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the corrosion and weld crack resistances of a Cu alloy by restricting the contents of Zn, P, Sn, Al, Si and Fe and/or Pb and carrying out cold rolling again after final annealing. CONSTITUTION:An alloy consisting of, by weight, 25-40% Zn, 0.005-0.070% P, 0.05-1.0% Sn, 0.05-1.0% Al, 0.005-1.0% Si, 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 cold rolled again at 3-20% draft after final annealing. By the final annealing, the grain size of the alloy is regulated to <=0.015mm as required. By this method, a Cu alloy having superior corrosion resistance and low weld crack sensitivity can be obtd. The Cu alloy can be utilized as a material for a heat exchanger, especially for a radiator.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing a copper alloy having excellent corrosion resistance, and is particularly suitable for use as a material for heat exchangers such as condensers, feed water heaters, distillers, coolers, and water generators. Radiator tank (container) used for etc.

The present invention relates to a method for manufacturing a copper alloy that is optimal as a material 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 often used as a heat exchanger, especially as a radiator for automobiles, but dezincification corrosion occurs in brass depending on the environment, which is a major problem.

An automobile radiator dissipates heat by circulating liquid between the engine and the radiator as a cooling medium to adjust the temperature of the body.The radiator is in constant contact with the cooling medium, and this cooling medium causes corrosion from the inside. There is a problem that arises.

Also, while the car is running, the radiator absorbs SO from exhaust gas, coastal air containing salt, and even factory air.

If exposed to gas etc., it will corrode from the outside as well.

The material conventionally used for radiators is copper 6.
Brass containing 5 wt% and 35 wt% 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, especially in radiator tubes,
Copper alloy welded tubes made by high-frequency resistance welding or high-frequency induction welding have come to be used in place of conventional lock-seamed tubes made by caulking in order 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. When manufacturing copper alloy welded pipes, high-frequency 1'A conduction welding or V''6-frequency resistance welding is used as a welding method, and due to the characteristics of the welding method, welding cracks occur. It has the disadvantage of being easy to manufacture.

In this situation, heat exchangers, especially radiator tanks (
At the same time, there has been a demand for improved corrosion resistance for containers (containers), tubes, fins, etc., and at the same time, for the welding area F, it has been desired to develop a material that is both corrosion resistant and less susceptible to weld cracking.

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

The present invention has zinc 25 to 40 wt%, phosphorus 0.005 to 0
．． 070wt%, tin 0.05-1. Ow 7%, aluminum 0.05-1.0wt%, silicon 0.005-1.
Contains 0wt% and further contains iron 0.005-1.0wt%
, the inner surface of the button contains 0.005-1.3 wt% of any one or two of them in a total amount of 0.005-1.3 wt%, and the balance is copper and unavoidable impurities.
A method for producing a copper alloy with excellent corrosion resistance, characterized by cold rolling with a working degree of 0%, and 25 to 40 wt% zinc
, Phosphorus 0.005-0.070wt%, Tin 0.05-1
．． Qwt%, aluminum 0.05-1.0wt%, silicon 0.005-1.0wt%, and further iron 0.0
05 to 1.0 wt%, button 0.005 to 0.3 wt%, one or two of the inner surfaces in a total amount of 0.005 to 1.3 wt%
Including.

After final annealing the alloy consisting of the remaining copper and unavoidable impurities so that the grain size is 0.015 nta or less, the alloy is further cold rolled at a working ratio of 3 to 20% to achieve corrosion resistance. This article relates to a method for producing an excellent copper alloy.

Next, the reasons for limiting the alloy components and contents constituting the present invention will be explained. Copper and zinc are the basic materials of the alloy constituting the present invention, and have excellent workability, mechanical strength, and thermal conductivity. Zinc content 25~4Qwt
% is because the content is 25 wt%, and if it is less than 40 wt%, the workability will be poor, and if it exceeds 40 wt%, the precipitation of β phase in the copper-zinc alloy will be noticeable, resulting in poor corrosion resistance and cold pressability. This is because it becomes worse.

The phosphorus content is 0.005 to 0.070w! The reason why the phosphorus content is less than 0.005 wt% is that no improvement in corrosion resistance is observed;
If the content exceeds 0.05 to 1.0wt, the corrosion resistance will be improved, but signs of intergranular corrosion will be seen.
% is because if the tin content is less than 0.05 wt%, no improvement in the corrosion resistance of the welded part will be observed when L-welding is performed during corrosion resistance, and if it exceeds 1.0 wt%, the effect will be saturated. . Aluminum content 0.05~1.0w
The reason why it is set as t% is that the aluminum content is 0.05wt.
This is because if the content is less than 1.0% by weight, no improvement in corrosion resistance, especially of the welded part when welded, will be observed, and if it exceeds 1.0% by weight, the effect will be saturated. Silicon content 0.005-1
．． The reason for 0wt, ■ is that the silicon content is 0.0.
If it is less than 0.05 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 and, conversely, the corrosion resistance against corrosion from the inner surface will deteriorate. Iron content 0.005
The reason for ~1.0wt% is that the iron content is 0.005wt.
%, no improvement in corrosion resistance is observed, and 1.0 wt.
%, the effect becomes saturated. The reason why the lead content is set to 0.005 to 0.3 wt% is that the lead content is o.

If it is less than 0.05 wt%, no improvement in corrosion resistance is observed;
．． This is because if it exceeds 3 wt%, workability deteriorates. In this way, the addition of phosphorus, iron, and lead adds corrosion resistance to the material, and the addition of tin, aluminum, and silicon adds corrosion resistance to the material and the welded part when welded.

Furthermore, the reason why the crystal grain size is limited to 0.015Mn or less will be described below. As a result of investigating the cause of weld cracking caused by high-frequency induction 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 this phenomenon, it was found that the influence of the crystal grain size is large, and that such a phenomenon 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, and that corrosion resistance can be improved by reducing grain size. I found out.

The reason why the crystal grain size was limited to 0.015 m or less is.

This is because if the grain size exceeds 0.0150111, welding cracks are likely to occur and deterioration of corrosion resistance is observed.

In the present invention, the reason why cold rolling is performed at a workability of 3 to 20% after final annealing is that cold rolling improves soldering properties, but the workability is This is because if it is less than 3%, no improvement in soldering properties will be observed, and if it exceeds 20%, the mechanical strength will increase and the moldability, particularly when processing the radiator tube, will deteriorate.

The alloy obtained by the manufacturing method of the present invention is
This alloy exhibits good corrosion resistance and 78 joint cracking resistance, and also has good solderability, making it a material suitable as a steel alloy for heat exchangers, especially radiators.

EXAMPLE Alloys having the compositions shown in Table 1 were melted and hot rolled at 700'C to form a plate with a thickness of 8 m, which was then cold rolled to a thickness of 3 m. This was annealed for 500'CX 1 hr, and then finally cold rolled into a plate with a thickness of 200 mm.

This was further heat treated at various temperatures from 350°C to 600'CX 1 hr to adjust the crystal grain size shown in Table 2. The welded parts to be subjected to the corrosion resistance test were made by butting TIG? 6
It was made by touching.

The corrosion resistance test was performed by dissolving 1.3 g/Q of sodium bicarbonate, 1.5 g/Q of sodium sulfate, and 1.6 g/Q of sodium chloride (assuming corrosion from the inside) in IQ distilled water at a liquid temperature. The temperature was maintained at 88° C., air was blown at a rate of 100 mQ per minute, and the solution was immersed 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 result is the third
Shown in the table.

Tests for resistance to weld cracking caused by embrittlement of grain boundaries when in contact with molten base metal were conducted using alloys of various compositions with the grain sizes shown in Table 2 as shown in Figure 1. Processed into a pipe shape, this is made into a pipe with the same composition, melting point +
It was immersed in molten metal held at 50° C. for 3 seconds, then taken out and subjected to impact as shown in FIG. 2 in a holding furnace while the attached metal was molten. 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 IUn thickness and grain sizes shown in Table 2 were cold rolled at the working degrees shown in Table 5, and then subjected to solderability tests. Soldering test is 80++ diameter
+n+, 20wt% Sn in a cylindrical crucible with a depth of 60mm
- Heat the solder consisting of 80 wt% Pb to 320°C to create a molten metal, and drop the sample (width 10 nn + surface cleaned, length 50 nn +
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 (wetting equilibrium time) was measured when the sample was immersed in the solder bath (wetting equilibrium time), and the soldering properties were evaluated using this. The results are shown in Table 6.

As can be seen from Tables 3, 4, and 6, the alloy obtained by the present invention exhibits excellent corrosion resistance in the welded part when used as a material against dezincification corrosion and when welded, as well as exhibits excellent weld cracking resistance and solder resistance. It was found that the adhesive properties were also good.

In other words, in the comparative examples (sample numbers 1 to 10), the maximum dezincification corrosion depth was 213μ to 392μ in the base metal and 337μ in the welded part.
The alloy of the present invention (sample no. 11) reached ~721 μ
~23) has a minimum value of 23μ to a maximum value of 86μ in the base metal, and a minimum value of 53μ to a maximum value of 192μ in the welded part, indicating that it has excellent dezincification corrosion resistance. Among the alloys constituting the present invention, alloys with a grain size of 0.015n+m or less have better zinc corrosion resistance.

In addition, although the alloy constituting the present invention has excellent dezincification corrosion resistance as described above, it also has a crystal grain size of 0.015 na or less (sample number 12.14゜16.18.20
) undergoes only ductile deformation in the weld cracking test shown in FIG. 2, with no cracking occurring, and the weld cracking resistance is improved. On the other hand, if the grain size is 0. If it exceeds O15mn, it is not preferable because it causes grain boundary destruction.

The soldering properties of those subjected to the cold rolling of the present invention with a workability of 3 to 20% (sample numbers 11 to 19) and those that were not subjected to the same cold rolling (sample numbers 20 to 23) were evaluated based on the soldering properties ( 2 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 can be seen that the equilibrium is reached in a shorter time compared to the relatively long time of 30 seconds to 2.70 seconds, and the soldering is excellent.

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

Below margin Table 2 Table 3 Table 4 Table 5 Table 6

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a 1 m thick alloy pipe used in the weld cracking resistance test, and FIG. 2 is a schematic explanatory diagram of the weld cracking resistance testing apparatus. 1: Alloy pipe 1m thick (length 10mm) 2: Free falling object (weight 200gtz) 3: Support stand 4: Heating and holding furnace a: Pipe inner diameter (φ20■) b: Pipe outer diameter (φ22m)

Claims (2)

[Claims] (1) Zinc 25-40wt%, phosphorus 0.005-0.0
70wt%, tin 0.05-1.0wt%, aluminum 0.05-1.0wt%, silicon 0.005-1.0w
Contains t%, and further contains 0.005 to 1.0wt% iron and 0 lead.
．． After final annealing, an alloy containing one or two of 0.005 to 0.3 wt% in a total amount of 0.005 to 1.3 wt%, and the balance consisting of copper and unavoidable impurities, is further processed by 3 to 20%. A method for producing a copper alloy with excellent corrosion resistance, which is characterized by cold rolling. (2) Zinc 25-40wt%, phosphorus 0.005-0.0
70wt%, tin 0.05-1.0wt%, aluminum 0.05-1.0wt%, silicon 0.005-1.0w
Contains t%, and further contains 0.005 to 1.0wt% iron and 0 lead.
．． An alloy containing one or two of 0.005 to 0.3 wt% in a total amount of 0.005 to 1.3 wt%, and the balance consisting of copper and unavoidable impurities is finally annealed to have a crystal grain size of 0.0.
After adjusting it so that it is 15mm or less, add another 3 to 20 mm.
A method for producing a copper alloy with excellent corrosion resistance, which is characterized by cold rolling with a working degree of 1.5%.