JPS6230861A - 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 and Si and carrying out cold rolling again at a specified draft 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 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 low weld crack sensitivity as well as superior corrosion resistance 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 as a material for heat exchangers such as condensers, feed water heaters, distillers, coolers, and water purifiers. The present invention relates to a method for producing a copper alloy that is optimal as a material for radiator tanks, tubes, fins, etc. used in automobiles and the like.

Brass generally has good mechanical properties, workability, and thermal conductivity, and is also relatively inexpensive, so it is widely used. Brass is widely used in heat exchangers, particularly automobile radiators, but in certain corrosive environments, brass undergoes denitrification ↑G corrosion, which is considered to be one of the fatal defects in use.

Automotive radiators are used to suppress the rise in engine temperature.A liquid cooling medium is circulated between the engine and the radiator, and the liquid that has risen in temperature is dissipated by the radiator, thereby increasing the temperature of the engine. Cooling is in progress. Therefore, the radiator is always in contact with the cooling medium, and there is a problem in that the cooling medium causes corrosion from the inner surface. In addition, while a car is running, it is corroded from the outside by exhaust gas, S○2 scum near industrial areas, and salt in coastal areas.

Copper 6 is traditionally used in radiators.
Brass consisting of 5wt% zinc and 35wt% zinc is used, but as the corrosive environment is worsening due to pollution, the lifespan of conventional radiators using brass is gradually becoming shorter.

Furthermore, particularly in recent years, welded tubes by high frequency resistance welding or high frequency induction welding have been used for radiator tubes (pipe) instead of conventional lock seam tubes by caulking. This is because welded tubes are cheaper than lock-seamed tubes in terms of cost and production efficiency, but due to the uniqueness of the weld structure, the welded part of welded tubes is less expensive than other parts. It has the disadvantage of significantly deteriorating corrosion resistance, which is a major restriction on its use. Furthermore, when a welded tube is manufactured using high-frequency induction welding or high-frequency resistance welding, the welding method also has the drawback of being susceptible to weld cracking.

Due to situations like 2, corrosion resistance is required for heat exchangers, especially radiator tanks, tubes, and fins. It is desired to develop materials with low

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

The present invention contains 25-40 wt% zinc and 0.005% phosphorus.
-0.070wt%, tin 0.05-1. OwL%, aluminum 0.05~1.0wt%, silicon 0.005~
A method for producing a copper alloy with excellent corrosion resistance, which is characterized in that an alloy containing 1.0 wt% and the balance consisting of copper and unavoidable impurities is further cold rolled at a workability of 3 to 20% after final annealing, and Zinc 25~40wt%, phosphorus 0.005~
0°070wt%, Do, 05-1.0wt%, aluminum 0.05-1.0wt%, silicon 0oO05~]
After adjusting the alloy containing 2.0 wt% and the balance copper and unavoidable impurities so that the grain size is 0.015 nn or less by final annealing, it is further cold rolled at a working ratio of 23 to 20%. The present invention relates to a method for producing a copper alloy having excellent edibility.

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 mechanical properties, workability, and thermal conductivity. The reason why the zinc content is set to 25 to 40 wt% is that if the zinc content is less than 25 wt%, workability will deteriorate, and if it exceeds 40 wt%, precipitation of β phase in the copper-zinc alloy will be noticeable, resulting in poor corrosion resistance and This is because cold workability deteriorates.

The reason why the phosphorus content is set to 0.0.05 to 0.070wt% is that no improvement in corrosion resistance is seen when the phosphorus content is 0.005wt%, and conversely, when the phosphorus content is 0.070w
This is because when the content exceeds t%, corrosion resistance is improved, but signs of single-grain boundary layer corrosion are observed. Tin content 0.05~1.0w
The reason why it is set as t% is that if the tin content is less than 0.05wt%, the corrosion resistance of the welded part will not be improved, especially when welded, and if the tin content exceeds 1.0wt%, the effect will be reduced. This is because it becomes saturated. Aluminum content from 0.05
The reason for setting it to 1.0 wt% is that the aluminum content is 0.0 wt%.
If the amount is less than 0.05 wt%, no improvement in corrosion resistance, particularly in the corrosion resistance of the welded part when welded, will be observed, and if it exceeds 1.0 wt%, the effect will be saturated. The reason why the silicon content is set to 0.005 to 1.0 wt% is that if the silicon content is less than 0.005 wt%, no improvement in corrosion resistance, especially of the welded part when welded, is observed; ,0wt
%, the effect becomes saturated and, conversely, the corrosion resistance against corrosion from the inner surface deteriorates.

By adding phosphorus in this way, corrosion resistance is added to the material, and by adding tin, aluminum, and silicon, the corrosion resistance of the material and the welded part is improved when welded.

Furthermore, the reason why the crystal grain size is limited to Q, Q15Iff11 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 contacting with the molten base material, the grain boundaries become brittle and when subjected to a light impact. It was discovered that weld cracking occurs. Therefore, as a result of investigating this phenomenon, it was found that the influence of crystal grain size is large.
In conclusion, it has been found that such a phenomenon can be significantly suppressed by reducing the W degree. Furthermore, the present inventors also investigated the influence of grain size on corrosion resistance, and found that corrosion resistance, particularly 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 is limited to 0.015 nn or less is that if the crystal grain size exceeds 0.015 nm, welding cracks are likely to occur and deterioration of corrosion resistance is observed.

In the present invention, after final annealing, the reason why cold rolling is performed at a working degree of 3 to 20' is to improve soldering properties by cold rolling.
If the degree of addition L is less than 3%, no improvement in soldering properties will be observed, and if it exceeds 20゛Z□, the mechanical strength will increase and the formability, especially when processing the radiator tube, will deteriorate. It's for a reason.

In this way, the manufacturing method of the present invention yields 1! ) is a material suitable as a copper alloy for exchangers, especially radiators, because it shows good corrosion resistance and weld cracking resistance, and also has good solderability.

Next, an example will be described.

Example 1 An alloy having the composition shown in Table 1 was melted and hot rolled at 700'C to form a plate with a thickness of 8mm, which was then cold rolled to a thickness of 3nn. This was annealed at 500° C. for 1 hr, and then final cold rolled into a plate with II and r dimensions.

This was further heat treated at various temperatures from 350°C to 600°C x lhr to adjust the crystal grain size shown in Table 2. The welded parts to be subjected to the corrosion resistance test were fabricated by butt TIG welding 1 mm thick alloys of various compositions having the grain sizes shown in Table 2. Corrosion resistance test was carried out by dissolving 1.3 g of sodium bicarbonate A, 1.5 g of Q sodium sulfate, 1.6 g of sodium chloride (1) in IQ distilled water, maintaining the liquid temperature at 88°C, and heating at 100 m/min.
Q 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 sizes shown in the table are processed into a pipe shape as shown in Figure 1, and this is immersed in molten metal of the same composition maintained at +50°C, melting point, for 3 seconds, and then It was taken out and placed in a holding furnace while the metal adhering to it was molten and 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.

Furthermore, 1 mP' with the grain size shown in Table 2! .

After cold rolling the alloy at the working degree shown in Table 5,
The soldering was subjected to a sex test. For soldering, the diameter is 8.
0mm, depth 60nn+ cylindrical crucible with Sn20wt
%-Pb 80 wt% was heated to 320 °C to make a molten metal, and a descending rate of 25 nn/see was added to the melt.
(When the sample (width with clean surface - 〇m, length 50mm) is immersed in the solder bath)
The time required for the force and the force drawn into the solder bath to reach equilibrium was determined as a1g, and the soldering properties were evaluated using this value. 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 raw material and welded against dezincification corrosion, and has good resistance to weld cracking. It was also found that soldering properties were good.

That is, in the comparative examples (sample numbers 1 to 10), the maximum corrosion depth was 168μ to 489μ in the base metal and 26μ in the welded part.
1μ to 782μ, whereas the alloys of the present invention (sample numbers 11 to 23) have a minimum value of 26μ to a maximum value of 103μ,
It can be seen that the welded part has excellent dezincification corrosion resistance with a minimum value of 58μ to a maximum value of 197μ. Among the alloys constituting the present invention, alloys with a crystal grain size of O', 015 nn or less have better dezincification 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, 15 nn 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, a crystal grain size exceeding 0.015me+ is not preferable because it causes grain boundary fracture.

In addition, the soldering properties of those subjected to cold rolling with a workability of 3 to 20% according to the present invention (sample numbers 11 to 19) and those that were not subjected to the same cold rolling (sample numbers 20 to 23) were evaluated ( 2. The time it takes for the buoyant force that the sample receives from the solder bath and the force that is drawn into the solder bath to become equal to 1.
It can be seen that soldering is excellent in soldering properties as it reaches a clear state in a shorter time than it takes a relatively long time of 13 seconds to 2.35 seconds.

The alloy obtained by the manufacturing method of the present invention has extremely excellent properties for use in heat exchangers, especially radiators.

Below margin Table 1 Table 2 Table 3 Table 5 Table 4 Table 6

[Brief explanation of the drawing]

FIG. 1 is a 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 parve of ffX length 1m (length 10n
vu') 2: Free falling object (200 stacks) 3: Support stand 4: Heating and holding furnace

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
A method for producing a copper alloy with excellent corrosion resistance, which comprises further cold rolling an alloy containing copper and unavoidable impurities at a working ratio of 3 to 20% after final annealing. (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
After final annealing the alloy, which contains copper and unavoidable impurities, is further subjected to cold rolling at a working ratio of 3 to 20%. A method for manufacturing a copper alloy with excellent corrosion resistance.