JPS5921376B2 - Copper alloy for work hardening springs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a work-hardening copper alloy for springs that has excellent workability, corrosion resistance, spring characteristics, and the like.

Phosphor bronze, which is well known as this type of alloy, is a copper alloy with excellent moldability, corrosion resistance, spring characteristics, and solderability, and is therefore prized as a spring material for electrical equipment.

However, on the other hand, it has the drawback of containing a large amount of expensive Sn.

It is clear that the ratio of the price of Sn to Cu will become higher and higher in the future, considering the balance of resources on the earth.

The present invention aims to reduce costs without sacrificing the advantages of phosphor bronze, and is characterized by replacing a portion of Sn with Zn and Ni. Details will be explained below with reference to the drawings. do.

Cu-Ni-Z n-8n alloys have been known for some time, but the present invention maintains good corrosion resistance and solderability by regulating the upper limits of Zn and Ni. The feature is that the lower limit of Ni was determined with emphasis on creep characteristics.

First, an experiment conducted by the present inventor and its results will be described below.

That is, the sample was placed in a high-frequency melting furnace with a diameter of 20 mm and a height of 2 mm.
After creating an ingot of 0.001 m in length and subjecting it to groove roll rolling, heat treatment, wire drawing, peeling, and wire drawing processing, further heat treatment,
After repeated pickling and wire drawing processing, the final wire diameter is 0.55mm.
This is a wire rod that has been subjected to mechanical straightening processing.

Here, the intermediate processing rate is 40 to 80, and the final processing rate is 5.
0%, and the heat treatment temperature was 600°C.

As for the deoxidizer during dissolution, no new deoxidizing agent was used when Zn was included, and copper phosphorus containing 5% P was used only when Zn was absent.

Table 1 shows the measurement results of the core properties obtained from these samples.

Here, the number of samples for investigation of the tensile test, longitudinal elastic modulus, spring limit value, and stress relaxation property was two each under the same conditions, and the average thereof was determined.

In addition, the longitudinal elastic modulus was determined using the cantilever beam method, and the stress relaxation properties were also determined using the cantilever beam method, and an initial stress such that the maximum surface bending stress was 40 kgf/ma was applied to each sample at a constant displacement. The amount of stress relaxation after 400 hours at 120°C was determined.

(Actually, we also measured the state at intermediate intervals such as 10 hours, 25 hours, 50 hours, etc., but here we measured the condition at 400 hours.
Shows only the value after time has elapsed.

) Furthermore, the ammonia corrosion test was carried out by leaving the sample in a desiccator with an ammonia solution at a concentration of 12.5% stored in the bottom of the desiccator, separated from the solution, and applying an initial bending stress of 40 kgf 7 m4.

The test temperature in this case is 25°C.

In addition, when Zn is low, rather than stress corrosion,
A part of the sample melted and eroded into a pinhole, causing a break, and the time was recorded.

The number of samples was five for each condition, and Table 1 shows the maximum, minimum, and average.

As a result of analysis based on the values obtained from the above-mentioned experimental results, the following conclusion was reached.

Figure 1 shows various types of C processed by 50% in the experiment described above.
The relationship between the components and tensile strength of the u=Zn-8n alloy wire is shown in a phase diagram, and the numbers in the circles at the top of the figure indicate the tensile strength (unit: kg/mm) for each component.

In the figure, when connecting points with equal tensile strength, for example, Cu-5S n with a tensile strength of 66 becomes Cu-3,5
8n-5Zn, Cu-2,58n-10Zn,
Similarly, Cu-3Sn of 58 is Cu-1,5S n-5
It can be seen that Zn and Cu-I S n-10 are approximately equal to Zn.

In other words, when targeting the same strength, the addition of Zn at a weight ratio of 5% results in Sn1.5%, and the addition of Zn at a weight ratio of 10% results in 5n2-2.5%.
can be saved.

However, the addition of Zn lowers corrosion resistance and creep customization, so in the present invention, from the viewpoint of corrosion resistance, the upper limit of Zn is regulated, and in order to keep the creep characteristics higher than that of phosphor bronze, N is added.
i is added.

Figure 2 shows the change in ammonia corrosion resistance when Zn is added to 3% Sn-containing copper. The time until breakage is set as 100, and the ratio is shown. In the figure, the upper and lower lines at each point indicate the range of variation depending on each sample, and the black circles indicate the average value.

From this figure 2, when Zn is less than 10, the corrosion resistance is
It can be seen that it is not much different from phosphor bronze.

The alloy of the present invention contains Ni in addition to the above, but N
In fact, since i has the effect of improving corrosion resistance, Cu-
It does not impair the corrosion resistance of Zn-8n type.

Figure 3 shows the relationship between Zn and Ni content and creep customization in a phase diagram.The numbers in the circle indicate the initial stress of 40 kgf/ma for the 50% workpiece and after leaving it at 120℃ for 400 hours. The amount of stress relaxation is expressed as a ratio, with Cu-28n being 100.

From the figure, it can be seen that when Ni is added at a ratio of 4 or more to 10 Zn, an alloy having creep characteristics superior to that of phosphor bronze can be obtained.

Therefore, from the above results, according to the present invention, Zn is contained in 5 to 10 parts, Ni is contained in 2 to 10 parts, Sn is contained in 1 to 6%,
In addition, as shown by the diagonal lines in Figure 4, a copper alloy in which the Ni content is 40 times higher than the Zn content is cheaper than phosphor bronze, which has equivalent strength, corrosion resistance, and creep properties. , and was confirmed to be highly versatile.

Note that the reason why the upper limit of Ni is set to 10 is that if Ni increases further than this, the soldering properties will deteriorate.

Furthermore, the smaller the amount of Sn, the cheaper it will be, but if it is less than 1 thread, it will lose its strength, so it is not acceptable, and if it exceeds 6 threads, it will become difficult to process.

Furthermore, the reason why the lower limit of Zn is set to the factor 5 is that if the amount is less than this, the effect of replacing phosphor bronze in terms of strength will be diminished.

The above has shown the characteristics of the alloy of the present invention as a work hardening type alloy, but like other alloys such as phosphor bronze or precipitation hardening/spinodal hardening type alloys, it is also possible to improve the spring characteristics by heating at low temperature. be.

[Brief explanation of the drawing]

Figure 1 is a phase diagram showing the relationship between the components and tensile strength of various Cu-Zn-Sn alloy wires subjected to 50% processing, and Figure 2 is a characteristic diagram showing the relationship between the tensile strength and the components of various Cu-Zn-Sn alloy wires subjected to 50% processing. A custom-made diagram showing changes in ammonia corrosion resistance over time, Figure 3 shows Zn,
FIG. 4 is a characteristic diagram showing the relationship between the proportion of Ni and the IJ-p characteristic, and FIG. 4 is a characteristic diagram showing the usable range in comparison with Zn and Ni.

Claims (1)

[Claims] 1 Weight ratio: Zn: 5-10%, Sn: 1-6%, N
i: 2 to 10, the balance consists of Cu and impurities, and N
A work-hardening copper alloy for springs, characterized in that the amount of i is set to be a factor of 40 or more compared to the amount of Zn.