JPS593530B2 - Corrosion-resistant brass material for radiator tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brass material for radiator tubes having dezincing corrosion resistance properties.

Generally, the tube material for radiators used in automobiles is made of brass containing 65% copper and 35% zinc (hereinafter referred to as 65/35 brass), and is made by molding a brass strip into a flat cross-sectional shape.
The abutting ends are joined to the flap and brazed.

Further, corrosion resistance is required for use, and solder coating or painting is performed on the coating.

However, what is most required in the production of radiators today is further weight reduction and improved corrosion resistance.In order to reduce weight, the thickness has recently been reduced to 0.13m7M, but on the other hand, Sometimes dezincification corrosion occurs, causing pitting corrosion, and there is a risk of water leaking from that area, so it is necessary to anticipate a certain degree of corrosion in advance, and it has been thought that it would be difficult to make the wall any thinner. .

The dezincification corrosion phenomenon of radiator tube material progresses from both the inside and outside of the tube.The inner surface is corroded due to constant contact with the hot water circulating inside the tube, and the outer surface is corroded due to the presence of chlorides due to residual solder flux or in coastal areas. This is due to the contact with salt in the environment and S02 gas in industrial areas, and when a car is subjected to vibrations and severe repeated stress while driving in such a corrosive environment, corrosion fatigue occurs and the damage is more severe than simple corrosion. Furthermore, there are more opportunities for corrosion.

Therefore, if it is possible to prevent such dezincification corrosion, it is possible to further reduce the thickness of the radiator tube material, which can contribute to reducing the weight of automobiles and the like.

The present invention was developed for the purpose of preventing such dezincification corrosion.

Generally, 65/35 brass is used because hot workability is poor if the zinc content is less than 28% in brass materials, and 37%
If the β phase is exceeded, the β phase will precipitate, deteriorating the corrosion resistance and also the cold workability, so an intermediate component thereof is used.

The present invention improves corrosion resistance by adding a small amount of nickel etc. to a brass material in the above zinc range.At the same time, it has the tensile strength, elongation, hardness, grain size, and Erichsen It also satisfies other characteristics such as value.

That is, the present invention uses 0.5 to 5.0 parts of nickel alone, or 0.05 to 1.0 parts of nickel, 0.005 to 0.1 parts of arsenic, and 0.005 to 0 parts of phosphorus. .1%, antimony 0.005 to 0.1%, and one or more of the following are mixed and added, and zinc is in the range of 28 to 37%, and the balance is substantially copper to prevent dezincification corrosion. A brass material for a radiator tube is provided.

Next, the present invention will be described in detail below based on examples.

First, in order to find additive metals that are effective against dezincification corrosion of brass plates, we melted 65/35 base brass to which various elements were added, and used it for corrosion tests with a thickness of 0.51n7IL in the following manner. A specimen was made.

(a) Melt casting (15mm thick) → (b) 850℃ hot rolling (5mm thick) → (・Pickling → (→ cold rolling (2mm thick) → (e) 500℃ sintering → (to) ) Pickling → (G) Cold rolling (Q, 5 mm thickness) → (7) 500°C annealing → (IJ) Pickling → (J) Cold rolling (Q, 5 mm thickness).

Conventional methods for measuring dezincification corrosion of brass include (a) immersing it in an acidic solution of cupric chloride in hydrochloric acid for several months and measuring the progress of corrosion.

(b) A method of measuring the progress of corrosion over several weeks using a salt spray test.

However, since the test period for each method is long, the present inventors have developed and adopted a new rapid corrosion measurement method that has the same accuracy as the above method.

This is a method in which the weight loss rate and copper ion concentration and zinc ion concentration in the solution are measured by immersing the solution in a 60°C 5th scale hydrochloric acid aqueous solution for 72 hours.
As shown in the figure.

That is, 1 three-lough flask (500 mA capacity) with 2 reflux devices.
250 m of 5% hydrochloric acid aqueous solution 3 was added to the tank, the specimen 4 was inserted and suspended by plastic thread 5, and after being left in a constant temperature bath 6 maintained at 60°C for 72 hours, it was taken out. In addition to determining the change in weight, the concentrations of Cu2+ ions and Zn2+ ions eluted into the aqueous hydrochloric acid solution 3 are determined.

In this case, the specimen 4 is 110×257fi with a thickness of 0.5
The surface of the plate was polished with ≠1500 emery paper, washed with water and dried.

In addition, in the figure, 7 is hot water, 8 is a heater, 9 is a temperature controller,
Reference numeral 10 indicates a thermometer, and reference numeral 11 indicates a heat insulating material (styrofoam).

An example using the above measurement method will be described below.

Reference Example 1 An alloy was prepared in which arsenic, which is said to be effective in preventing dezincification corrosion of brass, was mixed with 65/35 base brass in a range of 0.005 to 0.1%, and the corrosion was measured by the above measurement method. The results of the test are shown in Figure 2-a.

As can be seen from this result, the amount of weight loss per unit area and the amount of [Cu2++Zn2 mo] eluted into the liquid were almost the same, and showed a tendency to increase as the amount of As added increased.

On the other hand, the zn2+/Cu2+ ratio in the liquid is a constant value within the addition amount range of 0.02% As or more (Zn/Cu in brass = 35/
65=0.54), which indicates that dezincification corrosion is prevented.

In addition, when the Zn''/Cu2 force ratio is 0.54 or more,
The surface of test piece 4 is copper-colored, and the cross section of the test piece is EPMACX.
When we performed elemental analysis using a wire microanalyzer, it was confirmed that the surface layer was almost entirely made of copper.
It was found that a dezincification corrosion phenomenon occurred.

Example 1 Therefore, in the same manner as in Reference Example 1 above, 0.1 to 5 nickel was added.
．． Amount of weight decrease (△W) when 0% is added.

The relationship between the amount of eluted ions (Ct), the dezincing ratio (r), and the total amount of corrosion (ΔT) is shown in Figure 2-b.

From this result, it can be seen that, except for the difference in the amount added, the inhibition of dezincing shows almost the same tendency as in the case of As addition.

The total corrosion amount (ΔT) shown in Figures 2-a and 2-b is a value calculated as follows.

△T (m?/d)"C5s(Zn"")+(Zn2
”)N However, ■=Test liquid volume (4) S=Specimen surface area (ffl) [zn2mo]=Zn2+ ion concentration in the liquid (rnfI/l) [Cu2+]=Cu”+e in the liquid) f7 concentration (mfI
/l) As a result, △T value and dezincification ratio r (=Zn''/Cu2
+) allows comparison of dezincification suppression effect and corrosion resistance.

Reference Example 2 Next, in order to find out which metal elements are effective in suppressing dezincification corrosion, various metal elements were added to 65/35 base brass to prepare specimens, and the 5 coefficient of ω℃ was added. The effect of dezincification on corrosion in aqueous hydrochloric acid was investigated.

The results are shown in Table 1. As can be seen from Table 1, among the various metal elements, five were effective in suppressing dezincing: arsenic, phosphorus, antimony, tin, and nickel.

Of these, arsenic is 0.02% or more and phosphorus is 0.005%.
As described above, anti-corrosion effects were observed when antimony was added in an extremely small amount of 0.005% or more.

However, since antimony tends to increase the total amount of corrosion, it is better to add less antimony.

Nickel is effective when added in a ratio of 1 or more, and the total amount of corrosion is also low.

It is a new finding that the addition of nickel alone has the effect of preventing dezincification corrosion.Nickel is easily dissolved in brass, has good workability, and has good mechanical properties of rolled sheets, so it can be used for brass for radiator tubes. Suitable as an additive element for materials.

Although tin is known as an element that improves the corrosion resistance of brass, its effect on inhibiting dezincification corrosion is inferior to the above four elements.

However, no dezincing suppression effect was observed for elements other than the above five elements.

As described above, the five elements of arsenic, antimony, phosphorus, tin, and nickel were effective individually.

However, although small amounts of arsenic, antimony, and phosphorus are effective, adding large amounts may cause edge cracking during hot or cold working.

Example 2 Next, the amount of nickel was reduced to 0.5% and 0.2%, and trace amounts of arsenic, antimony, and phosphorus were added thereto, and their synergistic effects were investigated.

The results are shown in Table 2. Table 2 shows that even if the amount of nickel is reduced, dezincification corrosion is prevented by adding trace amounts of arsenic, antimony, and phosphorus.

In Tables 1 and 2, the total amount of corrosion hardly changes even if the dezincification ratio decreases because dezincification corrosion is prevented and the corrosion shifts to full surface corrosion.

In addition, as a result of measuring the cold work hardening curves of the samples in Table 2, there was almost no difference between the cold work hardening curves and the case of 65/35 brass without additives.

Example 3 Additive element-containing 6 prototyped in the reference examples and examples above
A 0.4 mm thick 5/35 brass plate subjected to 80° cold rolling was annealed at various temperatures for 30 minutes to determine its hardness (Hv).
Figure 3 shows the annealing softening curve measured.

As can be seen from Figure 3, the recrystallization temperature is hardly affected by trace addition elements, and in any case it is between 200 and 30.
It can be seen that the temperature is between 0℃.

The hardness above the recrystallization temperature differs slightly depending on the type and amount of added elements, but except for the case of 0.5Ni+0.05P, it is almost the same as the case of no addition.

It is softened to a hardness (Hv) of 100 or less by annealing at 600°C for 30 minutes.

The case of 0.2Ni+0.02As is equivalent to the case of no addition.

Example 4 Figure 4 shows the results of measuring the mechanical properties of a 0.2 nickel brass material to which trace amounts of arsenic, antimony, and phosphorus were added.The test sample was annealed at 500°C for 30 minutes. rear,
It is a 17% cold-rolled Q plate material with a thickness of 5 mm.

As can be seen from FIG. 4, the elongation was slightly lower and the hardness and tensile strength were slightly higher than when no additive was added.

As shown in Examples 3 and 4, the workability and mechanical properties were hardly affected by the addition of nickel, and on the other hand, it was found that by raising the temperature slightly in the final annealing, it could be handled in the same way as brass without additives.

For example, Table 3 shows that a 5 mm hot rolled sheet is cold rolled to a thickness of 2 mm, annealed at 600°C for 30 minutes, and then 0.5 mm thick. Various types of 65/3 when cold-rolled with Renme and annealed again at 600°C for 30 minutes
5 This shows the mechanical properties of brass.

As can be seen from Table 3, samples 461 and 3 are the cases in which 0.2% nickel is added to 0.02% phosphorus, and the cases in which 0.02% phosphorus is added alone, but the results are almost the same. It is.

/I6.2 No additives (4
This is almost the same as in case 4).

Therefore, it can be seen that the addition of a small amount of nickel does not particularly affect workability, mechanical properties, etc., and is significantly effective in preventing dezincing.

As described above, the present invention uses 0.05 to 5% of nickel alone or 0.005 to 0.1% of arsenic and 0.05% of phosphorus by weight.
．． It is a brass material to which at least one of 0.005 to 0.1% antimony is mixed and added, and the composition is made of zinc in a range of 28 to 37 parts and the balance is copper, and is dezinced. It is particularly effective in preventing corrosion, making it ideal for radiator tubes.

In the case of adding nickel alone, a ratio of 0.5 to 5 is good, and a ratio of 1 or more is particularly preferred, and if it exceeds 5, no special effect will be observed and it will be economically disadvantageous.

In addition, in the case of 0.05 to 1% nickel, it is preferable to add a small amount of one or more of arsenic, antimony, and phosphorus in a mixed manner.Addition of more than the above numerical range will have an adverse effect on workability, and will prevent corrosion during dezincing. The effect is not very noticeable.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the dezincification corrosion measuring device, Figure 2-a and b
The figures are graphs showing the effects of arsenic and nickel on the corrosion of 65/35 brass plates in a 5% hydrochloric acid solution, and Figure 3 is a graph showing the annealing softening curves of 65/35 brass plates containing various additive elements. FIG. 4 is a graph showing the results of measuring mechanical properties when arsenic, antimony or phosphorus is added to a brass plate with 0.2 nickel added. Explanation of symbols, 1...Three-hole flask, 2...Reflux vessel, 3
... 5th grade hydrochloric acid aqueous solution, 4... Sample, 5... Thread, 6
... Constant temperature bath.

Claims (1)

[Claims] 1. Nickel 0.5-5.0%, zinc 28-37% by weight
A corrosion-resistant brass material for a radiator tube, characterized in that the remainder has a composition of copper within a range of 1. 2. Add at least 0.05 to 1.0 part of nickel by weight, 0.005 to 0.1 part of arsenic to 0.005 to 0.1 part of herring, and 0.005 to 0.1 part of antimony. A corrosion-resistant brass material for a radiator tube, characterized in that the composition is mixed and added with zinc in a range of 28 to 37 parts, with the remainder being substantially copper.