JP2002069551A - Free cutting copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a free cutting copper alloy having good extending workability and having excellent machinability so as to be low in machining resistance and so that machined chips are also finely parted irrespectively of working conditions in mechanical working. SOLUTION: In this copper alloy containing a low melting point metal which does not enter into solid solution in a matrix, the grains of the above low melting point metal are dispersed into the matrix by >=105 pieces per mm3. As the low melting point metal, Pb or Bi is preferable, and, as the copper alloy, a Cu-Zn alloy is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free-cutting copper alloy which has a performance peculiar to a copper alloy and is excellent in machinability, ie, machinability (machinability).

[0002]

2. Description of the Related Art A copper alloy containing a low melting point metal which does not form a solid solution in a matrix, for example, Cu-Zn containing Pb
Alloys are used as faucet fittings, valve parts, bearings, gears, etc. because of their excellent castability, hot and cold workability, and machinability.

[0003] Since machining of such components is generally performed using an automatic lathe, as a material characteristic, low machinability and good machinability are required, as long as the machinability is cut. . In order to improve production efficiency, when using a tool with a smooth finished surface as a roughing tool, a tool with a smooth finished surface is generally difficult to cut off the debris, and if the cutting resistance is high, Because the frequency of damage increases,
It is important to provide a low cutting resistance and to cut off the chips regardless of the machining conditions. Low cutting resistance leads to a longer life of the cutting tool, and cutting of the chips Therefore, improvement of machinability is desired because it leads to labor saving.

[0004] The Cu—Zn alloy containing Pb is manufactured according to JIS.
Registered as free cutting brass in C3600, C3700,
Although Pb for providing good machinability is defined by the concentration, even if the concentration is the same, sufficient machinability may not be obtained depending on the machining conditions. In recent years, Pb has been regarded as a harmful substance that has a bad effect on the human body and the environment, and its use tends to be restricted. Therefore, there is also a brass for cutting added with Bi in place of Pb. Further, depending on the machining conditions, there is a case where the swarf continues and sufficient machinability cannot be obtained.

[0005] It is possible to work harden the material by cold working and increase the hardness to divide the swarf to provide sufficient machinability, but on the other hand, when the hardness of the material increases, the material becomes harder. There is a problem that the resistance increases.

In order to clarify the reason why sufficient machinability cannot be obtained depending on machining conditions, even when the content of Pb or Bi is the same in Pb-containing brass or Bi-containing brass. In addition, as a result of various experiments and investigations, the difference in machinability is that the distribution form of Pb or Bi particles in the matrix depends on the manufacturing conditions such as the hot working temperature of the material, the degree of hot working and the cooling rate. It was found that it was caused by different things.

[0007]

SUMMARY OF THE INVENTION The present invention has been made as a result of further extensive experiments and studies based on the above findings, and has been developed in terms of hot extrudability, cold drawability and the like. An object of the present invention is to provide a free-cutting copper alloy having excellent machinability, excellent machinability, and low machinability regardless of machining conditions in machining, and in which machining chips are finely divided.

[0008]

According to the first aspect of the present invention, there is provided a free-cutting copper alloy containing a low-melting-point metal which does not form a solid solution in a matrix. 1 mm ^{3 of the} low melting point metal particles
It is characterized in that at least 10 ⁵ particles are dispersed.

[0009] The free-cutting copper alloy according to the second aspect is the first aspect.
Wherein the low melting point metal is one or two of Pb and Bi.

[0010] The free-cutting copper alloy according to the third aspect is the first aspect.
Or 2) wherein the copper alloy is a Cu—Zn alloy.

[0011] The free-cutting copper alloy according to the fourth aspect is the first aspect.
(3) to (3), wherein the copper alloy contains P: 0.01 to 0.1%.

[0012] The free-cutting copper alloy according to claim 5 is provided by claim 1.
The copper alloy is 0.5 to 4.0%,
Fe: characterized in that it contains one or two of 0.1 to 0.5%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The free-cutting copper alloy of the present invention is a low-melting metal that does not form a solid solution in a matrix, for example, Pb, B
A copper alloy containing i, Sb, etc. is assumed. These low-melting metals are molten immediately after hot working, but are solidified by subsequent cooling, disperse in the matrix as independent particles in an inconsistent manner with the matrix, and act as chip breakers during machining to protect them. Shreds chips.

That is, when the shear strain transmitted from the tool collides with the dispersed particles of the low-melting metal, the shear strain propagates as a crack in the matrix material due to mismatch. The propagation distance of this crack depends on the strength of the material and the amount of strain imparted to the material.However, if the distance between the low melting point metal particles is shorter than the maximum propagation distance of the crack, the crack will be continuous and the chips will be shear-type. It is divided. The low-melting metal particles are melted by machining heat during machining, and function as a lubricant between the machining tool and the material to reduce cutting resistance.

[0015] By cutting the cutting waste, reducing the cutting resistance,
In order to obtain a distribution form of low melting point metal particles for providing excellent machinability, it is necessary to disperse at least 10 ⁵ particles of low melting point metal per 1 mm ^{3 in} a matrix. Due to this distribution form, regardless of the material strength and the amount of strain applied to the material, and regardless of the machining conditions
The shavings are separated. It is more preferable to disperse at least 10 ⁶ particles of the low melting point metal having the above particle diameter per 1 mm ^{3 in the} matrix, and it is possible to surely reduce the number of continuous chips to 3 or less.

In the present invention, among the low melting point metals dispersed in the alloy matrix, Pb and Bi are particularly preferred. The melting points of Pb and Bi are 327 ° C. and 2
It is as low as 71 ° C. and hardly forms a solid solution in a copper matrix. Further, as the copper alloy applied to the present invention, Cu
-Zn alloy, Cu-Zn-Ni alloy, Cu-Sn alloy,
Cu-Sn-P alloy and the like can be mentioned. Among them, Cu
-Zn alloy is most preferred, and the Cu content is 50.0 to 76.
0% Cu-Zn alloy can be used.

Further, in the free-cutting copper alloy of the present invention,
In particular, when the copper alloy is a Cu-Zn alloy, a specific amount of P, S
The properties can be improved by adding i and Fe. That is, by containing 0.01 to 0.1% of P, there is an effect of suppressing dezincification corrosion.
Further, since P functions to suppress the coarsening of the crystal grains, the coarsening of the low-melting metal particles accompanying the coarsening of the crystal grains can also be suppressed, and the distribution form of the low-melting metal particles can be controlled regardless of the manufacturing conditions. It is possible to obtain. If P is added in excess of 0.1%, hard and brittle Cu ₃ P is likely to be generated, which impairs cold workability. A more preferable P content range is 0.02 to 0.08%.

Since Si functions to suppress the coarsening of the crystal grains, it is also possible to suppress the coarsening of the low melting point metal particles accompanying the coarsening of the crystal grains, and the distribution of the low melting point metal particles is independent of the manufacturing conditions. It becomes possible to obtain a form. Further, since the addition of Si improves the material strength, the propagation distance of the crack can be increased. On the other hand, Si is apparent Zn
Increase the content, so-called Zn equivalent amount is large,
The addition of a large amount necessitates a reduction in the Zn content in the alloy, and raises the cost. Taking these into consideration, the preferred content of Si is in the range of 0.5 to 4.0%, and the more preferred content range is 1.0 to 3.0%.

Fe, like Si, functions to suppress the coarsening of the crystal grains. Therefore, it is also possible to suppress the coarsening of the low melting point metal particles accompanying the coarsening of the crystal grains. It is possible to obtain a distribution form of the metal particles. On the other hand, if a large amount of Fe is added, Fe does not completely form a solid solution at the hot working temperature of the copper alloy, so that the remaining Fe impairs cold workability. Taking these into consideration, the preferable content of Fe is in the range of 0.1 to 0.5%, and the more preferable content is 0.15 to 0.4%.

The copper alloy of the present invention is usually supplied as a rod, and its production is performed by ingoting an alloy having the above composition,
The obtained ingot is hot-extruded, and further usually cold-drawn, and if necessary, straightened and finished. Post-heat treatment may be performed after hot extrusion in order to prevent stress corrosion cracking. The distribution form of the low-melting metal particles in the present invention can be obtained by a technique such as making the hot working temperature relatively low, performing extrusion at a high extrusion ratio, or increasing the cooling rate after extrusion. .

[0021]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples, and the effects thereof will be demonstrated based on them.
It should be noted that these examples are for describing a preferred embodiment of the present invention, and the present invention is not limited thereto.

Example 1 New ingots of Cu, Zn, Bi, Pb, Si, Fe and C
Alloys (alloys A to J) having the composition shown in Table 1 in which the concentrations of the component elements were adjusted by mixing a u-15% P master alloy were melted and cast, and formed into a billet having a diameter of 294 mm.

The resulting billet was subjected to a temperature of about 600 ° C. for alloys AB and about 650 ° C. for alloys CJ.
After hot extrusion into a bar having a diameter of 17.5 mm at a temperature of 680 ° C., cold drawing was performed with a reduction rate of cross section of 15%, followed by straightening.

With respect to the bar (test material) after the corrective finishing, the distribution form of Pb and / or Bi particles was measured by the following method, and the workability, machinability and dezincification corrosion resistance were evaluated.

Distribution form of low-melting metal particles: A reflection electron image of the matrix is taken by a scanning electron microscope, and the distribution form is specified by image analysis. Workability: In hot extrusion and cold drawing, those that did not break or crack were accepted (o), and those that broke or cracked were rejected (x).

Machinability: peripheral speed 10 to 300 m / min, cutting depth 0.01 to 2.5 mm, feed amount 0 to 0.25 mm /
rev. The cutting process was performed using cutting tools of various shapes, and under any of the cutting conditions, the chips were in the form of a shear, and were finely divided and the machinability was excellent. At least one piece with continuous chips was rejected (x).

Dezincification corrosion resistance: 12.7 g of CuCl ₂ .2H ₂ O at 75 ± 3 ° C. according to the ISO method
/ L solution for 24 hours, measure the dezincification corrosion depth,
Evaluation was made according to the following criteria. Dezincification corrosion depth 100μm
The following (depth that does not cause a problem of dezincification corrosion in practical use) are acceptable (（), and those with a dezincification corrosion depth exceeding 100 μm are unacceptable (x).

Table 1 shows the distribution of Pb and Bi particles, and Table 2 shows other evaluation results. As can be seen from Table 2, the test materials according to the present invention all have no problem in workability, show excellent machinability irrespective of the machining conditions, and have a test material No. P containing P. Nos. 5 to 8 have good dezincification corrosion resistance.

[0029]

[Table 1]

[0030]

[Table 2]

Comparative Example 1 New ingot of Cu, Zn, Bi, Pb and Cu-15% P
Alloys (alloys KL) having the composition shown in Table 3 in which the concentration of the component elements was adjusted by mixing the mother alloy were melted and cast, and the diameter was 294.
Ingots were formed into billets of mm.

After the obtained billet is hot-extruded into a bar having a diameter of 17.5 mm at a temperature of about 650 ° C., it is subjected to cold drawing at a cross-sectional reduction rate of 15%, and is further subjected to a straightening finish to straighten it. With respect to the rod (test material) after finishing, the distribution form of Pb and / or Bi particles was measured in the same manner as in Example 1, and the workability and machinability were evaluated. Table 4 shows the results.

As shown in Table 4, the test material No. 11-1
In No. 2, since the amount of distribution of Pb or Bi particles was small, in a cutting test, the chips were not finely divided but formed into a spiral shape, resulting in poor machinability.

[0034]

[Table 3]

[0035]

[Table 4]

Comparative Example 2 New ingots of Cu, Zn, Bi, Pb, Fe, Si and C
Alloys (alloys M to Q) having the composition shown in Table 5 in which the concentration of the component elements was adjusted by mixing a u-15% P master alloy were melted, cast, and formed into a billet having a diameter of 294 mm.

The obtained billet is heated at about 650-680 ° C.
After hot extrusion into a 17.5 mm diameter bar at a temperature of, cold drawing at a cross-section reduction rate of 15%, straightening and finishing, and a bar (test material) after straightening finishing, As in Example 1, the distribution form of Pb and / or Bi particles was measured, and workability and machinability were evaluated. Table 6 shows the results.

As shown in Table 6, the test material No. 13 is P
, Cracks occurred during hot extrusion and drawing. Test material No. 14 and No. 16 is Pb
Since the amount of distribution of particles and Bi particles was small, chips were not finely divided in a cutting test, but were spiraled, resulting in poor machinability. Test material No. 15 and No. In No. 17, since the Si content and the Fe content were large, cracks occurred during drawing.

[0039]

[Table 5]

[0040]

[Table 6]

Comparative Example 3 New ingots of Cu, Zn, Bi, Pb, Fe, Si and C
Alloys having a composition shown in Table 7 (alloys RU) in which the concentrations of the component elements were adjusted by mixing a u-15% P master alloy were melted and cast, and formed into a billet having a diameter of 294 mm.

The obtained billet is heated at about 650 to 680 ° C.
After hot extrusion into a 17.5 mm diameter bar at a temperature of, cold drawing at a cross-section reduction rate of 15%, straightening and finishing, and a bar (test material) after straightening finishing, As in Example 1, the distribution form of the Pb and / or Bi particles was measured, and the workability, machinability, and dezincification corrosion resistance were evaluated. Table 8 shows the results.

As shown in Table 8, the test material No. 18 is B
Since the distribution amount of the i-particles was small, the chips were not finely divided in the cutting test but became spiral and the machinability was poor. The test material No. Since all of Nos. 18 to 21 do not contain P, dezincification corrosion having a corrosion depth exceeding 100 μm occurred in a dezincification corrosion test.

[0044]

[Table 7]

[0045]

[Table 8]

[0046]

According to the present invention, the extensibility, such as hot extrudability and cold drawability, is excellent, and the machining resistance is low irrespective of the machining conditions in machining, and the swarf is fine. A free-cutting copper alloy having excellent machinability to be divided is provided.

Claims (5)

[Claims] 1. A copper alloy containing a low-melting metal that does not form a solid solution in a matrix, wherein at least 10 ⁵ particles of the low-melting metal are dispersed in the matrix per 1 mm ^3. Machinable copper alloy. 2. The low melting point metal is one of Pb and Bi.
The free-cutting copper alloy according to claim 1, wherein the alloy is a kind or two kinds. 3. The free-cutting copper alloy according to claim 1, wherein the copper alloy is a Cu—Zn alloy. 4. The copper alloy has a P content of 0.01 to 0.1%.
The free-cutting copper alloy according to any one of claims 1 to 3, further comprising (mass%, the same applies hereinafter). 5. The method according to claim 1, wherein the copper alloy contains 0.5 to 4.0% of Si.
The free-cutting copper alloy according to any one of claims 1 to 4, comprising one or two of Fe: 0.1 to 0.5%.