JP2002285263A - Brass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide brass which has industrially satisfiable recycling properties and stable feedability, improved elution of Pb, and excellent machinability. SOLUTION: The brass has a crystal structure having a soft phase, and a hard phase, and in which a brittle phase is interposed into the boundary between the phases. The brass has an apparent Zn content of 37 to 50 wt.%, and an Sn content of 0.5 to 7 wt.%. The above crystal structure consists of α+γ; wherein, the area ratio of the α phase is 60 to 95%, and the area ratio of the γ phase is 5 to 40%, or consists of α+β+γ; wherein, the area ratio of the α phase is 40 to 95%, the area ratio of the βphase is 1 to 30%, and the area ratio of the γ phase is 5 to 30%. The above brittle phase consists of at least one selected from S, Ti and Zr of 0.01 to 0.2 wt.%, or their compound; wherein, the α phase is the hard phase, the γ phase is the hard phase, and the β phase is the brittle phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to brass having excellent machinability.

[0002]

2. Description of the Related Art Free-cutting brass (C3604) is often used as brass having excellent machinability.
There has been proposed a brass which is concerned about elution of Pb and has excellent machinability and improved Pb elution. For example, JP-A-200
0-119775 precipitates a γ phase or a κ phase by adding other elements such as Bi and Se instead of Pb,
Although the machinability is improved, Bi and Se have problems in recyclability, stable supply, cost, and the like.

[0003] The applicant of the present application has disclosed in
As 09835, a material in which the area ratio of γ phase and the crystal grain size are controlled is proposed as a material which is industrially satisfactory such as recyclability and stable supply and has improved Pb elution.

[0004]

When a γ-phase is present, a stress is generated in the vicinity of a relatively hard γ-phase when receiving a strain in a cutting process by utilizing a difference in hardness from other phases. It concentrates, breaks and generates voids (voids), and improves the machinability. However, soft α-phase has a relatively strong binding force between γ-phase and the phase, and suffers distortion during cutting. At this time, before the stress is concentrated near the γ phase, the α phase may be deformed to relieve the stress, hinder the destruction and the generation of voids, and there is still room for improvement.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide brass that is industrially satisfactory in terms of recyclability and stable supply, and that has improved Pb elution and excellent machinability. And

[0006]

According to the present invention, which has been made to solve the above problems, the crystal structure has a soft phase and a hard phase, and a fragile phase or particle is interposed at the phase interface. It is a brass characterized by that.

[0007] The crystal structure consisting of a soft phase and a hard phase is
When stress is applied during cutting, stress concentrates especially near the hard phase, and fracture and voids are likely to occur.When stress is concentrated by interposing a fragile phase at the phase interface Can easily generate voids from this fragile phase, and can reduce the energy required for deformation, so that cutting resistance can be reduced.

Further, the apparent Zn content is 37 to 5
The brass is characterized in that the content of Sn is 0 wt% and the content of Sn is 0.5 to 7 wt%, so that a soft phase and a hard phase can coexist, and the Sn is in the above range. Thus, the γ phase can be easily precipitated, and can be solid-solved in the β phase having poor corrosion resistance to improve the corrosion resistance.

Further, the crystal structure is composed of α + γ, the area ratio of the α phase is 60 to 95%, and the area ratio of the γ phase is 5 to 95%.
By using brass characterized by being 40%, voids for reducing cutting resistance when subjected to distortion due to cutting can be appropriately dispersed and present, so that brass excellent in machinability can be provided.

The crystal structure is composed of α + β + γ,
The brass is characterized in that the area ratio of the α phase is 40% to 95%, the area ratio of the β phase is 1 to 30%, and the area ratio of the γ phase is 5 to 30%. Voids to reduce cutting resistance when subjected to strain due to moderately dispersed existence can provide brass with excellent machinability, and by depositing β phase thinly, β phase becomes brittle phase Available.

Further, the γ phase is dispersed in the crystal structure,
When the particle size of the γ phase is 0.3 to 15 μm, the voids are easily generated in the vicinity of the γ phase, and the voids can be appropriately dispersed and present, so that brass excellent in machinability can be provided.

Further, the α phase which is a soft phase and the γ phase which is a hard phase have a strong bonding force between the phases, the α phase has a high ductility, and the concentration of stress hardly occurs. By interposing the fragile phase, the fragile phase can break and generate voids with low deformation energy, and the cutting resistance can be reduced efficiently.

Further, the brittle phase is made of at least one of S, Ti, and Zr or a compound thereof, so that the metal or the compound of the compound as the brittle phase easily intervenes between the phases. it can.

Further, there is provided a brass having a soft phase and a hard phase forming a crystal structure, and having a phase having an intermediate strength between the two phases at the phase interface.

According to the present invention, when the strength difference between the soft phase and the hard phase is too large, stress is not concentrated near the hard phase due to the ductility of the soft phase, and the occurrence of fracture and voids is suppressed. Therefore, stress can be concentrated at the interface between the phase having the intermediate strength and the hard phase by interposing the phase having the intermediate strength, causing breakage and generation of voids at the interface, Cutting resistance can be reduced.

Further, when the apparent Zn content is 37 to 5
The brass is characterized in that the content of Sn is 0 wt% and the content of Sn is 0.5 to 7 wt%, so that a soft phase and a hard phase can coexist, and the Sn is in the above range. And γ phase can be easily precipitated and solid solution in β phase having poor corrosion resistance to improve corrosion resistance.

The crystal structure is composed of α + β + γ,
The brass is characterized in that the area ratio of the α phase is 40% to 95%, the area ratio of the β phase is 1 to 30%, and the area ratio of the γ phase is 5 to 30%. The voids for reducing the cutting resistance when subjected to the strain caused by the deformation can be appropriately dispersed and present, so that brass excellent in the machinability can be provided.

Further, the γ phase is dispersed in the crystal structure,
When the particle size of the γ phase is 0.3 to 15 μm, the voids are easily generated in the vicinity of the γ phase, and the voids can be appropriately dispersed and present, so that brass excellent in machinability can be provided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, a detailed description will be given.

Materials that can be used in the present invention include an apparent Zn content of 37 to 50 wt% and a Sn content of:
0.5 to 7 wt% can be used. "The apparent Z
The term “n content” means that A is the Cu content [wt%],
B is the Zn content [wt%], t is the Zn equivalent of the third element (for example, Sn), and Q is the content of the third element [w
t%], “｛(B + t × Q) / (A + B + t
× Q)｝ × 100 ”. That is, the third element such as Sn does not form a special phase,
A solid solution is formed in the phase, and a structure in which the amount of Zn is increased or decreased is generated,
Since it shows properties corresponding thereto, it is defined by the apparent Zn content.

If the apparent Zn content is less than 37 wt%, no effective γ phase can be obtained, and if it exceeds 50 wt%, the brass becomes brittle, which is not desirable. In addition, the addition of Sn is a hard γ without impairing the good recyclability of brass.
A phase can be obtained, and in particular, a large amount of solid solution can be formed in the β phase to improve the corrosion resistance of the β phase having poor corrosion resistance. If the addition amount is less than 0.5 wt%, there is no effect, and 7 wt%
If it is larger, the brass becomes brittle, which is not desirable.

Precipitation of a soft α phase, a hard γ phase, and a β phase having intermediate strength by controlling the heating and cooling rates from raw materials such as castings, extrudates, and forgings having the above composition. Can be. For example, in order to form an α + γ phase, the material can be adjusted by heating, holding, and cooling the material at 400 to 480 ° C. At this time, the area ratio of the α phase was 6
It is desirable to set the area ratio of the γ phase to 0 to 95% and the area ratio of the γ phase to 5 to 40% in terms of compatibility between ductility and machinability. In the last cooling step of the casting step, the extrusion step, and the forging step when producing the raw material, the crystal may be adjusted in the above-mentioned temperature range and cooling rate.

Further, in order to form the γ phase so as to surround the β phase, the material is heated to 400 to 480 ° C. and α +
After obtaining the γ-phase structure, it can be adjusted by holding at 480 to 550 ° C. for 1 to 60 seconds and rapidly cooling to 400 ° C. or lower at 5 to 1000 ° C./second. At this time, the area ratio of the α phase is 40 to 95.
%, The area ratio of the β phase is 1 to 30%, and the area ratio of the γ phase is 5
It is desirable to set it to ３０30% in terms of compatibility between ductility and machinability. At this time, by adjusting the β phase so as to surround the γ phase, the generation of voids due to the ductility of the α phase can be suppressed.
Voids can be easily generated between the γ phase and the γ phase, and it is desirable. Further, by reducing the β phase to a minor axis of 10 μm or less, the β phase becomes a fragile phase, and voids can be generated from the β phase. Become like

The γ phase usually surrounds the β phase, that is, easily precipitates at the αβ interface. First, the α + γ phase forms a crystal structure, and the temperature range in which the β phase precipitates, for example, 52
By rapidly heating to 0 ° C, holding for several seconds, and then rapidly cooling,
The β phase can be precipitated so as to surround the γ phase.
If the heating rate is slow, β phase precipitates from one place of αγ interface,
It does not surround the gamma phase. If the retention time is long,
The γ phase becomes too small or disappears. When the cooling rate is low, a part of the β phase changes to the α phase and the γ phase, and does not surround the γ phase. Further, even when the β phase is rapidly cooled from a high temperature (around 550 ° C.) to precipitate a γ phase from the β phase, the β phase has a form surrounding the γ phase.

It is desirable that the γ phase is dispersed in the crystal structure, and the particle size is 0.3 to 15 μm or less. When the γ-phase particles are less than 0.3 μm, the particles are too small so that stress is not concentrated on the grain boundaries during cutting, and the γ-phase particles are 15 μm
If it exceeds, the resistance value when the blade comes into contact with the γ-phase particles itself increases, and the life of the blade and the surface accuracy decrease.

By adding a metal such as S, Ti, Zr or the like, which is concentrated at the grain boundaries, to the above-mentioned composition, and forming a fragile phase composed of those grains at the grain boundaries. When a strain is applied in the cutting process, stress concentrates on this fragile phase, and breakage and voids are easily generated, so that cutting resistance can be reduced. The metal may exist as a single metal or may exist in the form of a compound such as TiS. Further, the addition amount of the metal is 0.01 to 0.2 wt%. The effect does not change even if more than 0.2 is added.

Hereinafter, a more specific embodiment will be described in detail. Using the components shown in Table 1, the phase ratio, Examples 1, 3 and Comparative Example to adjust the crystal grain size of the γ phase,
It is manufactured through the steps shown in FIG. Examples 1 and 3 and Example 2 are manufactured through the steps shown in FIG. 2, in which the β phase is precipitated around the γ phase. In the process of Example 2, in order to obtain the above-mentioned crystal structure, the material is hot-extruded, air-cooled, then annealed at 400 to 500 ° C. and rapidly heated to 480 to 550 ° C. at 1 ° C./sec or more. And a water cooling process has been added.

[0028]

[Table 1]

The cutting performance was evaluated by measuring the cutting resistance using a dynamometer and evaluating the level of the resistance in three stages. The one that precipitates the β phase so as to surround it thinly around the γ phase is most excellent in machinability, and it is presumed that voids at grain boundaries are most likely to occur. On the other hand, in the case of the comparative example, it is presumed that stress is hardly concentrated on the grain boundaries and voids are hardly generated on the grain boundaries and cutting resistance is increased due to the high ductility of the α phase due to the large number of α phases.

[0030]

As described above, according to the present invention, it is possible to provide brass which is industrially satisfactory in terms of recyclability and stable supply, and which has improved dissolution of Pb and has excellent cutting properties.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a manufacturing process of an example of the present invention and a comparative example.

FIG. 2 is a diagram illustrating another manufacturing process of the embodiment of the present invention.

Claims (14)

[Claims] 1. A brass having a crystal structure having a soft phase and a hard phase, and a brittle phase interposed at the phase interface. 2. The brass has an apparent Zn content of:
37-50 wt%, Sn content is 0.5-7 wt%
The brass according to claim 1, comprising: 3. The crystal structure is composed of α + γ, the area ratio of the α phase is 60% to 95%, and the area ratio of the γ phase is 5%.
The brass according to claim 2, wherein the content is from about 40% to about 40%. 4. The crystal structure comprises α + β + γ,
The brass according to claim 2, wherein the α phase has an area ratio of 40% to 95%, the β phase has an area ratio of 1 to 30%, and the γ phase has an area ratio of 5 to 30%. 5. The γ phase is dispersed in a crystal structure,
The brass according to any one of claims 1 to 4, wherein the particle size of the γ phase is 0.3 to 15 µm. 6. The brass according to claim 3, wherein the fragile phase is provided at an interface between an α phase and a γ phase. 7. The fragile phase is 0.01 to 0.2 wt%.
The brass according to claim 1, comprising at least one of S, Ti, and Zr or a compound thereof. 8. A brass having a crystal structure having a soft phase and a hard phase, and a phase having an intermediate strength between the two phases is interposed at the phase interface. 9. The brass has an apparent Zn content of:
37-50 wt%, Sn content is 0.5-7 wt%
The brass according to claim 8, comprising: 10. The crystal structure is composed of α + β + γ, the area ratio of the α phase is 40% to 95%, the area ratio of the β phase is 1 to 30%, and the area ratio of the γ phase is 5 to 30%. The brass according to claim 9, wherein: 11. The brass according to claim 10, wherein the γ phase is dispersed in a crystal structure, and the γ phase has a particle size of 0.3 to 15 μm. 12. The brass according to claim 10, wherein the phase having the intermediate strength is a β phase and is provided at an interface between the α phase and the γ phase. 13. The method according to claim 1, wherein the β phase is α
The brass according to claim 12, wherein the brass is interposed between the brass and the phase. 14. The phase having the intermediate strength has a minor axis of 1 mm.
The brass according to any one of claims 8 to 13, wherein the brass has a crystal phase of 0 µm or less.