JPH07166279A - Copper-base alloy excellent in corrosion resistance, punchability, and machinability and production thereof - Google Patents

Abstract

PURPOSE:To produce the copper-base alloy by specifying the comosition, in which Ni content is reduced as compared with nickel silver and a specific amount of Mn is added, and also specifying the area percentage of beta-phase comprising in a metallic structure. CONSTITUTION:An alloy ingot consisting of, by weight, 25-40% Zn, 0.1-8% Mn, and the balance copper, is worked into a specific shape. The resultant worked material is annealed at 450-600 deg.C for >=30min and then cold-worked at >=10% draft. The cold worked material is annealed at 350-500 deg.C for >=30min. By this method, the copper-base alloy, where the area percentage of beta-phase comprising in the metallic structure is 5-50% and which has corrosion resistance equal to that of nickel silver and also has punchability and machinability equal to those of brass and is reduced in cost, can be obtained. Moreover, 0.001-2% of one or more elements among Sn, P, Mg, Al, Cr, Fe, Co, Ag, Cd, Sb, Ti, Zr, In, B, Ta, Si, and Pd can be further incorporated into the above copper alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper-based alloy having excellent corrosion resistance, punching workability and machinability, which is used for keys and coins of houses and automobiles, various decorations and buildings, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, brass (C2801 etc.) plated with Ni or Cr is used for keys of houses and automobiles. In these plated products, the plated layer is likely to be peeled off or worn during use, and there is a risk that the brass base is exposed and the appearance is impaired. Moreover,
The exposed brass is easily corroded because it is directly touched by a person. For this reason, recently, nickel-white, which does not require plating, has been used in place of the brass. Nickel white is a silver-based copper-based alloy and is excellent in workability and corrosion resistance, and is widely used for keys or various decorations and buildings without plating.

[0003]

[Problems to be Solved by the Invention]
Since the Ni content is high as specified in JIS C7351 or C7521, the corrosion resistance is excellent, but the punching workability and machinability are inferior and the cost is high.

The present invention has been made in view of the above problems, and has corrosion resistance equivalent to nickel white containing a high concentration of Ni, but has punching workability and machinability comparable to those of brass. Another object of the present invention is to provide a copper-based alloy having excellent corrosion resistance, punching workability and machinability, which enables significant cost reduction by reducing the Ni content, and a method for producing the same.

[0005]

The copper-based alloy excellent in corrosion resistance, punching workability and machinability according to the present invention is Zn: 25 to 40% by weight, Ni: 6 to 12% by weight, Mn: 0.1 to 8%. % By weight, the balance consisting of copper and inevitable impurities,
The area ratio of the β phase in the metal structure is 5 to 50%. In addition to the above elements, Sn,
P, Mg, Al, Cr, Fe, Co, Ag, Cd, S
b, Ti, Zr, In, B, Ta, Si, and Pb, the total amount of one or more elements selected from the group consisting of 0 or more.
It may be contained in an amount of 001 to 2% by weight.

The method for producing a copper-based alloy excellent in corrosion resistance, punching workability and machinability according to the present invention, uses Zn: 25 to 40% by weight, Ni: 6 to 12% by weight, Mn: 0.1 to 8% by weight. A step of processing an alloy ingot containing the balance of copper and unavoidable impurities into a predetermined shape, and 450 to 6
The first annealing step of annealing for 30 minutes or more at a temperature of 00 ° C, the step of cold working the worked material after annealing at a working rate of 10% or more, and the cold working material at a temperature of 350 to 500 ° C. A second annealing step of annealing for 30 minutes or more. In addition to the above elements, the alloy ingot contains S
n, P, Mg, Al, Cr, Fe, Co, Ag, Cd,
The total amount of at least one element selected from the group consisting of Sb, Ti, Zr, In, B, Ta, Si and Pb is 0.
It may be contained in an amount of 001 to 2% by weight. Further, after the second annealing step, cold working may be performed at a working rate of 30% or less.

[0007]

The inventors of the present application have conducted various experimental studies in order to solve the above-mentioned problems of the prior art. As a result, it was found that the insufficient corrosion resistance due to the lower Ni content than that of nickel silver can be compensated by adding a predetermined amount of Mn. Further, it has been found that precipitation of β phase is effective for improving punching workability and machinability. However, the β phase has a property of being easily corroded. Therefore, the inventors of the present application investigated the relationship between the proportion of β phase and punching workability and machinability. As a result, the ratio of the area of β phase in the metal structure is 5 to 50.
It has been found that a copper-based alloy having a corrosion resistance of practically acceptable level and good punching workability and machinability can be obtained by setting the content by weight.
Further, by setting the crystal grain size of the β phase to 5 μm or less,
Corrosion resistance, punching workability and machinability are further improved.
When the crystal grain size of the phase is 10 μm or less, the effects of improving corrosion resistance, punching workability and machinability can be further enhanced.
The present invention has been made based on such experimental results.

Next, the reason for adding each component and the reason for limiting the composition in the copper-based alloy excellent in corrosion resistance, punching workability and machinability according to the present invention will be explained.

Zn: 25 to 40 wt% Zn contributes not only to improving mechanical strength but also to improving punching workability and machinability. When the Zn content is less than 25% by weight, the contribution of Zn to the strength improvement is small, and the proportion of β phase that can contribute to punching workability and machinability is set.
It is difficult to increase it to 5% or more. Conversely, if the Zn content is 4
If it exceeds 0% by weight, it becomes difficult to suppress the proportion of β phase to 50% or less, the corrosion resistance deteriorates, and the cold workability deteriorates. Therefore, the Zn content is 25 to 40% by weight.

Ni: 6 to 12 wt% Ni needs to be added in an amount of 6 wt% or more in order to improve mechanical properties and corrosion resistance. However, even if Ni is added in an amount of more than 12% by weight, the effects on these characteristics are saturated, and the punching workability and machinability are deteriorated, and the hot and cold workability are deteriorated. The increase will also be significant.
Therefore, the Ni content is 6 to 12% by weight.

Mn: 0.1 to 8 wt% Mn has the effect of improving the mechanical properties and corrosion resistance, and also having the effect of making the copper-based alloy have a high-grade, light-colored tone by the cooperative action with Ni. When the Mn content is less than 0.1% by weight, the effect on improving the mechanical properties and the corrosion resistance is small, and even when Mn exceeds 8.0% by weight, the hot and cold workability are deteriorated. Therefore, the Mn content is 0.1 to 8.0
Weight%

Sn, P, Mg, Al, Cr, Fe, C
o, Ag, Cd, Sb, Ti, Zr, In, B, Ta,
At least one selected from the group consisting of Si and Pb
Element: 0.001 to 2.0 wt% Sn, P, Mg, Al, Cr, Fe, Co, Ag, C
d, Sb, Ti, Zr, In, B, Ta, Si and Pb
Addition of at least one element selected from the group consisting of improves the mechanical properties of the copper-based alloy. Therefore, if necessary, one or two of these elements may be used.
One or more elements may be added. However, if the total addition amount of these elements is less than 0.001% by weight, the above effect cannot be sufficiently obtained. On the other hand, if the total content of these elements exceeds 2.0% by weight, hot and cold workability deteriorate. Therefore, Sn, P, Mg, Al, C
r, Fe, Co, Ag, Cd, Sb, Ti, Zr, I
When adding at least one element selected from the group consisting of n, B, Ta, Si and Pb, the addition amount is
It is preferably 0.001 to 2.0% by weight.

Note that Sn, P, Fe and Co have the effect of improving the corrosion resistance of the copper-based alloy in addition to the effect of improving the mechanical properties described above, and Mg, B and Pb include
It has the effect of improving punching workability and machinability. Further, Mg, Al, Cr, Zr and Ti have the effect of improving the hot workability of the copper-based alloy.

By the way, in order to improve the punching workability and the machinability, it is necessary to precipitate the β phase as described above. However, in order to enhance the effect without impairing the corrosion resistance, the β phase is added. It is necessary to disperse finely and uniformly. The inventors of the present application also studied a method for realizing fine and uniform dispersion of β phase. as a result,
It was found that the β phase can be finely and uniformly precipitated by performing the annealing in multiple times. Less than,
The method for producing a copper-based alloy according to the present invention will be described.

In the method of the present invention, first, an alloy ingot containing each element described above is hot-worked and cold-worked into a predetermined shape, and then annealed at a temperature of 450 to 600 ° C. for 30 minutes or more. (First annealing) is performed. By this first annealing, recrystallization occurs and the structure can be homogenized. In this case, if the annealing temperature is less than 450 ℃, not only recrystallization becomes insufficient, the structure becomes non-uniform and the corrosion resistance deteriorates, and the strength of the final product increases and the punching workability and machinability are increased. Deteriorates. On the other hand, if the annealing temperature exceeds 600 ° C., the crystal grains become coarse, and even if the second annealing described below is performed, it becomes difficult to disperse the β phase finely and uniformly, and the desired target properties cannot be obtained. . Also, when the annealing time is less than 30 minutes, recrystallization and homogenization of the structure are not sufficiently performed, and the corrosion resistance deteriorates. Therefore, it is necessary that the annealing temperature in the first annealing step is 450 to 600 ° C. and the annealing time is 30 minutes or more.

Next, after the first annealing, the working rate is 10%.
The above cold working is carried out. This cold working is performed in order to introduce a working strain to the structure,
In the annealing step of, the β phase is precipitated along with the processing strain introduced by this cold working. If the working ratio in the cold working process is less than 10%, the amount of working strain is insufficient and it is difficult to introduce the working strain uniformly. Therefore, the β phase is uniformly and finely precipitated in the second annealing process. Can't do it. Therefore, in the cold working performed after the first annealing step, it is necessary to set the working rate to 10% or more.

Then, annealing (second annealing) is performed at a temperature of 350 to 500 ° C. for 30 minutes or more. In the second annealing step, the β phase precipitates along the processing strain introduced by the cold working described above. However, if the annealing temperature in the second annealing step is less than 350 ° C, it is difficult to uniformly precipitate the β phase. Even if the annealing temperature is less than 350 ° C, there is a possibility that the β phase can be uniformly precipitated by setting the annealing time to, for example, 10 hours or more,
Such long annealing is not practical because the productivity is significantly reduced. On the other hand, if the annealing temperature exceeds 500 ° C,
Since the introduced work strain is completely recovered, β-phase precipitation easily occurs at the α-phase grain boundaries. Therefore, it becomes difficult to precipitate the β phase uniformly and finely. Also, if the annealing time is less than 30 minutes, it becomes difficult to uniformly precipitate the β phase. Therefore, the annealing temperature in the second annealing step is 35
It is necessary that the temperature is 0 to 500 ° C. and the annealing time is 30 minutes or more.

In this way, it is possible to obtain a copper-based alloy in which the β phase is uniformly and finely dispersed and which is excellent in corrosion resistance, punching workability and machinability. After the second annealing, finish cold working may be performed to adjust the product strength. However, if the processing rate in finish cold working exceeds 30%,
Product strength becomes too high and machinability deteriorates. For this reason, when performing finish cold working, the working rate is 30% or less.

[0019]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Using a Cryptor furnace, copper alloys having the compositions shown in Table 1 below were melted and cast in the atmosphere under charcoal coating to obtain an ingot having a thickness of 50 mm, a width of 75 mm, and a length of 180 mm. After cutting the front and back surfaces of this ingot, hot rolling was performed at a temperature of 800 ° C. to a thickness of 15 mm. Next, after removing the oxide scale with a grinder, cold rolling and annealing were performed to finally produce a plate material having a plate thickness of 2.8 mm. A plate material having a thickness of 0.5 mm was prepared for the stress corrosion cracking test.

[0020]

[Table 1]

Using these plate materials, tensile test, hardness test, grain size measurement, salt spray test, stress corrosion cracking test,
A punching test and a cutting test were carried out to examine the properties of the alloys of Examples and Comparative Examples. However, for the tensile test,
A JIS No. 5 test piece sampled in the rolling direction was used. The hardness is
The load was measured with a micro Vickers hardness meter at 5 kg. The crystal grain size was measured for α phase and β phase according to the comparison method of JIS H0501. Moreover, the area ratio of the β phase in the metal structure was also examined. The salt spray test was performed according to JIS Z2371.

The stress corrosion cracking test is conducted by Thompson (DHTh
Ompson) method. That is, holes were bored at both ends of a test piece (plate material) having a predetermined size, the test piece was bent into a loop, and a copper wire was passed through the hole so that both ends were in contact and fixed. Then, the copper wire was unwound to measure the distance (L1) between both ends of the test piece. In addition, the test piece was exposed to ammonia vapor for a certain period of time while keeping both ends of the test piece in contact with the copper wire, and then the copper wire was unwound to remove the distance (L
2) was measured. Then, the stress relaxation rate was calculated by the following mathematical formula 1.

[0023]

## EQU1 ## Stress relaxation rate (%) = {(L1-L2) / L1} × 100 By the 50% stress relaxation time at which this stress relaxation rate becomes 50%,
The results of the stress corrosion cracking test are shown.

The punching test was carried out using a die having a punch diameter of 10 mm and a die diameter of 10.10 mm with a universal testing machine at a punching speed of 5 mm / min. Then, the punching workability was evaluated in the secondary shearing occurrence state of the punching blank.

The cutting test was carried out by an end mill having a diameter of 2.5 mm under the conditions of a rotation speed of 2000 rpm, a feed rate of 100 mm / min, and a cutting depth of 1 mm. This cutting test was an accelerated test that did not use lubricating oil, and the burrs were observed on the test material after cutting to a length of 3 m. The machinability was evaluated by the number of burrs (having a length of 1 mm or more) per unit length of cutting groove. The results of these tests are summarized in Tables 2 and 3 below.

[0026]

[Table 2]

[0027]

[Table 3]

As is clear from Tables 2 and 3, all the alloys of Examples 1 to 9 are excellent in mechanical properties, and are also comprehensively excellent in corrosion resistance, punching workability and machinability. . Example 1 has a smaller proportion of β phase than the other examples, and although the punching workability and the machinability are not as excellent as those of the other examples, the corrosion resistance is good. In Examples 2 to 4, the proportion of β phase increases in this order, and β
The corrosion resistance is lower as the proportion of phases is larger, but conversely, the punching workability and the machinability are improved as the proportion of β phases is larger. In Examples 5 and 6, although the proportion of β phase was substantially equal to that in Example 3, the crystal grain size of β phase was small,
As a result, corrosion resistance and machinability are improved as compared with Example 3. In addition, in Examples 7 to 9, as compared with Example 6, α
The crystal grain size of the phase is small, and as a result, the corrosion resistance (particularly stress corrosion cracking resistance) is improved. in this way,
All of Examples 1 to 9 have excellent overall corrosion resistance, punching workability and machinability, and in particular, Examples 1, 2, 5 to 9 in which the β phase grain size is 5 μm or less have corrosion resistance and machinability. Very good. Further, Examples 8 and 9 in which the grain size of the α phase is 10 μm or less have extremely low susceptibility to stress corrosion cracking.

On the other hand, Comparative Example 1 in which the proportion of β phase was as small as 3%
Has excellent corrosion resistance, but has poor punching workability and machinability. In addition, Comparative Example 2 having a large proportion of β phase
Although it has excellent punching workability and machinability, it has poor corrosion resistance. Comparative Example 3 (white silver) is inferior in mechanical properties, punching workability and machinability. Comparative Example 4 (brass) is inferior in mechanical properties and corrosion resistance.

Next, a method for producing a copper alloy according to the present invention will be described in comparison with its comparative example. Using a Cryptor furnace, copper alloys having the compositions shown in Table 4 below were melted and cast in the atmosphere under charcoal coating to obtain an ingot having a thickness of 50 mm, a width of 75 mm, and a length of 180 mm. After cutting the front and back surfaces of this ingot, hot rolling was performed at a temperature of 800 ° C. to a thickness of 15 mm. Next, after removing the oxide scale with a grinder, cold rolling and annealing were performed under the conditions shown in Table 5 below.
Finally, a plate material having a plate thickness of 2.8 mm was produced. A plate material having a thickness of 0.5 mm was prepared for the stress corrosion cracking test.

Using these plate materials, the above-mentioned Examples 1 to 1
The tensile test, the hardness test, the grain size measurement, the salt spray test, the stress corrosion cracking test, the punching test and the cutting test were carried out in the same manner as in 9 and Comparative Examples 1 to 4. The results are summarized in Tables 6 and 7 below.

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Table 6]

[0035]

[Table 7]

As is clear from Tables 6 and 7, since the annealing temperature in the first and second annealings is higher in Example 13 than in the other Examples, the β phase is partially segregated at the grain boundary of the α phase. Was. However, all of the alloys of Examples 10 to 13 have excellent mechanical properties, as well as excellent corrosion resistance, punching workability and machinability. On the other hand, in Comparative Example 5 in which the annealing temperature in the first annealing step was low and Comparative Example 7 in which the annealing time was short, there were uncrystallized parts, and part of the β phase was segregated into a fiber shape. Therefore, the alloys of Comparative Examples 5 and 7 were inferior in corrosion resistance and were not good in both punching workability and cutting workability. In Comparative Example 6 in which the annealing temperature in the first annealing step was high, the crystal grain size of the α phase was large, and the β phase was α
Because of segregation at the grain boundary of the phase, none of the corrosion resistance, punching workability and machinability was satisfactory. In Comparative Example 8 in which the intermediate cold working ratio was as small as 5%, the β phase distribution was non-uniform even after the second annealing, and punching workability and machinability were not satisfactory. In Comparative Example 9 in which the annealing temperature in the second annealing step is low and Comparative Example 11 in which the annealing time in the second annealing step is short, the precipitation amount of the β phase is small, and the distribution is non-uniform, and the punching process is performed. And machinability were poor. In Comparative Example 10 in which the annealing temperature in the second annealing step is high, the β phase is segregated at the grain boundary of the α phase, stress corrosion cracking property is not good, and punching workability and machinability are also satisfactory. Was not. Comparative Example 12 in which the cold working rate after the second annealing was increased to 35% was inferior in machinability because of its high strength. In addition, Comparative Example 13 (white silver)
Has excellent corrosion resistance, but is slightly inferior in strength and inferior in punching workability and machinability. Furthermore, Comparative Example 14
Although (brass) is excellent in punching workability and machinability, it is slightly inferior in strength and inferior in corrosion resistance.

[0037]

As described above, the copper-based alloy according to the present invention contains predetermined amounts of Zn, Ni and Mn, and
Since the area ratio of β phase occupying in the metallographic structure is specified within the predetermined range, it has excellent corrosion resistance, punching workability and machinability, and significantly improved mechanical properties compared to conventional nickel silver or brass. is doing. Further, the copper-based alloy according to the present invention has corrosion resistance equal to or higher than nickel silver, and punching workability and machinability are substantially the same as brass. Furthermore, since the Ni content is low, the manufacturing cost is relatively low. Therefore, the present invention is extremely useful as a copper-based alloy used for various keys, coins, decorations, buildings and the like.

Further, according to the method for producing a copper-based alloy of the present invention, the β phase can be finely and uniformly dispersed and precipitated in the copper-based alloy, and the corrosion resistance, punching workability and machinability are excellent. The copper-based alloy described above can be manufactured.

Claims (7)

[Claims] 1. Zn: 25 to 40% by weight, Ni: 6 to 12
%, Mn: 0.1 to 8% by weight, the balance consisting of copper and unavoidable impurities, and the area ratio of the β phase in the metal structure is 5 to 50%, corrosion resistance, punching -Based alloy with excellent workability and machinability. 2. Zn: 25 to 40% by weight, Ni: 6 to 12
% By weight, Mn: 0.1 to 8% by weight, and Sn,
P, Mg, Al, Cr, Fe, Co, Ag, Cd, S
0.001 to 2 of at least one element selected from the group consisting of b, Ti, Zr, In, B, Ta, Si and Pb.
% By weight, the balance consisting of copper and unavoidable impurities,
A copper-based alloy excellent in corrosion resistance, punching workability and machinability, characterized in that the area ratio of β phase in the metal structure is 5 to 50%. 3. The copper-based alloy having excellent corrosion resistance, punching workability and machinability according to claim 1, wherein the β phase has a crystal grain size of 5 μm or less. 4. The copper-based alloy having excellent corrosion resistance, punching workability and machinability according to claim 3, wherein the α-phase crystal grain size is 10 μm or less. 5. Zn: 25 to 40% by weight, Ni: 6 to 12
%, Mn: 0.1 to 8% by weight, the step of processing an alloy ingot having the balance of copper and unavoidable impurities into a predetermined shape, and the processed material at a temperature of 450 to 600 ° C. for 30 minutes or more. The first annealing step of annealing, the step of cold working the worked material after annealing at a working rate of 10% or more, and the cold working material
A second annealing step of annealing at a temperature of 0 to 500 ° C. for 30 minutes or more, and a method for producing a copper-based alloy having excellent corrosion resistance, punching workability and machinability. 6. Zn: 25 to 40% by weight, Ni: 6 to 12
% By weight, Mn: 0.1 to 8% by weight, and Sn,
P, Mg, Al, Cr, Fe, Co, Ag, Cd, S
0.001 to 2 of at least one element selected from the group consisting of b, Ti, Zr, In, B, Ta, Si and Pb.
A step of processing an alloy ingot having a content of wt% and the balance of copper and unavoidable impurities into a predetermined shape, and
A first annealing step, in which the material is annealed at a temperature of 0 to 600 ° C for 30 minutes or more, a step of cold working the worked material after annealing at a working rate of 10% or more, and a temperature of this cold worked material of 350 to 500 And a second annealing step in which the copper-based alloy is annealed for 30 minutes or more. 7. The corrosion resistance, the punching workability and the cutting according to claim 5, further comprising a step of performing a finish cold working at a working rate of 30% or less after the second annealing step. A method for producing a copper-based alloy having excellent properties.