JP2003147459A - Copper alloy cast member and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems in the casting of a copper alloy containing high concentration of Sn to develop a casting crack because the fluidity of this molten metal is low and the γ-phase is precipitated at the cooling time if the alloy is a brass and to add lead for improving the fluidity. SOLUTION: A brass cast member is made to contain 33.5-43 wt.% Zn and 0.5-8.0 wt.% Sn on the apparent contents and to have 0.5-4 mm thickness and <=10% residual ratio of the γ-phase after casting. When a dezincing corrosion test according with Technical Standards in Japan Brass Makers Association (JBMA) T-303 is applied, in the case of being the parallel with the working direction, to the maximum dezincing penetrating depth direction, the maximum dezincing depth is made to <=100 μm or in the case of being the right angle to the working direction, to the maximum dezincing penetrating depth direction, the maximum dezincing depth is made to <=70 μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a copper alloy casting member containing Sn.

[0002]

2. Description of the Related Art Conventionally, in a casting method for a Sn-containing copper alloy-based material, it is general to increase the lead and copper contents to suppress molten metal flow and solidification cracking. there were.

On the other hand, in order to improve mechanical properties and machinability, it is necessary to add a large amount of Zn. However, a copper alloy containing Sn and Zn at the same time, especially S
With the copper alloy containing a large amount of n, the molten metal flow was poor and a cast product having a predetermined shape could not be obtained. Further, the narrowing of the solid-liquid coexisting region due to the inclusion of Sn and Zn and the occurrence of cracks due to γ-phase precipitation during solidification were remarkable, and they were not used as casting materials.

In addition, even in products that have been cast, the formation of a coarse casting structure and the precipitation of a coarse γ phase are major problems of corrosion resistance and mechanical property deterioration as structural members. Has been said not to.

[0005]

According to the present invention, the Sn content is 0.5 to 10 wt% and the Pb content is 0.01 wt%.
% Of the copper alloy cast member is formed by precision casting.

According to the present invention, in addition to the bad molten metal flow of Sn, in order to improve the molten metal flowability, precision casting such as the lost wax method can be used even if the addition of Pb which has been added is made zero. Thus, by ensuring the temperature of the mold and controlling the pressure conditions, forced filling of the molten metal can be facilitated.

Further, the apparent Zn content is 33.5 to
It is a brass casting member having a Sn content of 0.5 to 8.0 wt% at 43 wt% and a wall thickness of 0.5 mm to 4 m.
The brass cast member was characterized by being in the range of m.

Here, the apparent Zn content is A
Is the Cu content [wt%], B is the Zn content [wt%],
When the Zn equivalent of the third element (for example, Sn) to which t is added and Q is the content [wt%] of the third element, “{(B
+ T · Q) / (A + B + t · Q)} × 100 ”, and when a third element is added to the Cu-Zn alloy, it forms a solid solution in α and β without forming a special phase. However, in that case, a structure in which the amount of Zn is increased or decreased is generated, and the properties corresponding to the structure are exhibited. Incidentally, the Zn equivalent of Sn is 2 and Pb is 1. According to the present invention, it is possible to suppress the occurrence of cracks due to shrinkage due to the precipitation of the γ phase by forming a thin-walled cast product having a wall thickness of the cast member of 0.5 mm to 4 mm. This enabled the cooling rate to be increased to minimize the precipitation of the γ phase, and the brass cast member containing a large amount of Sn could be manufactured.

Further, the apparent Zn content is 33.5 to
It is a brass casting member having a Sn content of 0.5 to 8.0 wt% at 43 wt% and a wall thickness of 0.5 mm to 4 m.
m, and the residual ratio of γ phase after casting was 10% or less.

By increasing the cooling rate of the cast member after casting by reducing the thickness of the cast member, it is possible to suppress the precipitation of the γ phase to a minimum and further reduce the influence of shrinkage due to the precipitation of the γ phase.

The present invention also provides a step of preparing a copper alloy casting material made of a copper alloy containing no lead, and a cavity diameter of a precision casting die having a molten metal of the copper alloy casting material heated to 0.5.
The method for producing a copper alloy cast member is characterized by at least including a step of casting under pressure to mm to 4 mm.

According to the present invention, lead was added to bronze or brass in order to ensure good flowability of molten metal, but metal can be flowed while maintaining a high temperature, and
By applying pressure, defects in the cavity can be prevented and the flowability of the molten metal can be secured, so the addition of lead becomes unnecessary.
Lead can be brought to a level of almost zero except that it is mixed as an impurity, and the adverse effect on the environment can be reduced.

Further, the apparent Zn content is 33.5 to
A step of preparing a brass casting material having a Sn content of 43 wt% and a Sn content of 0.5 to 8.0 wt%, and a cavity diameter of a precision casting mold in which a molten metal of the brass casting material is heated 0.5 mm to 4 m
and a step of casting under pressure into m.

According to the present invention, a precision casting die such as a ceramic shell die formed by the lost wax method can be used to provide a casting member having a good surface condition and high precision. Since the mold itself can be molded to be relatively thin, the cooling rate after casting can be increased, and the shrinkage during solidification can be made absolute by increasing the shrinkage ratio in the thickness direction compared to the width direction. It is possible to suppress the amount of deformation and significantly reduce the occurrence of shrinkage cracks. In addition, the cavity diameter is 0.5mm-4m
By setting m, the cooling rate at the time of solidification of casting can be made faster than that of sand casting, and the precipitation of γ phase, which is a brittle phase with a large volume change rate at the time of solidification, can be minimized. Become. This makes it possible to realize a casting process in which cracking is suppressed. Cooling of the cast member can suppress precipitation of the γ phase as much as possible.

Further, the casting mold is maintained at a temperature equal to or higher than the melting point of the copper alloy until the end of the casting step, and is rapidly cooled after the casting step to secure a molten metal flow by suppressing the precipitation of the γ phase at the time of casting and By suppressing the precipitation of the γ phase and increasing the cooling rate after solidification, the crystal grains are made finer and the strength and
Mechanical properties such as abrasion resistance are greatly improved, and at the same time, erosion resistance and stress corrosion cracking resistance can be dramatically improved.

Further, by heat-treating the cast member, it becomes possible to refine the crystal grains and optimize the structure, and to greatly improve the corrosion resistance and mechanical properties. In particular, it is possible to reduce the wall thickness as a structural member by improving the strength, and it is possible to significantly reduce the corrosion allowance due to the high corrosion resistance, so that the wall thickness can be reduced. Due to this thinning, it is possible to realize weight reduction and reduction of material usage.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
The method for manufacturing the water meter described in 1 will be described. The water meter 1 has a structure having a space 4 containing a flow meter (not shown) between a water inlet 2 and a water outlet 3. First, a model having the shape shown in FIG. 1 is molded with wax or other removable material. Thereafter, the process of coating the surface of the wax mold with the ceramic and drying it is repeated. Then, using an autoclave,
Upon heating, the wax pattern is melted and removed to form a mold called a so-called ceramic shell. This mold is fired at a predetermined temperature to make a unglazed mold. At this time, the wall thickness of the ceramic shell should be strong enough to hold the molten metal.
Basically, a sufficient strength can be secured with a few mm. Also,
At the time of casting, particles having good thermal conductivity may be filled around the ceramic shell to back up the strength. After heating this unglazed mold to a predetermined temperature, preferably above the melting point of the copper alloy to be used, pouring the molten metal, filling the cavity with the molten metal, and then cooling it or blowing air To force cooling. Then, after the molten metal has cooled and solidified, for example, a water jet or the like is sprayed to break the mold,
It is manufactured by obtaining the step of performing casting. The water meter obtained in this process is thinner and can be made lighter than conventional ones, and has various excellent properties such as strength and corrosion resistance by utilizing the γ phase described later. Can be Furthermore, since it is not necessary to add lead, the anxiety is resolved by the elution of lead.

Various materials can be used in the above process, but the apparent Zn content is 33.5 to 43.
A composition having a wt% and a Sn content of 0.5 to 8.0 wt% can be preferably used. At this time, if the cavity diameter in the ceramic shell is molded to about 0.5 to 4 mm, molding can be performed without being affected by shrinkage even if the γ phase precipitates during cooling after casting. Becomes In addition, the temperature of the ceramic shell is maintained at a temperature above the region where the γ phase does not exist by a heater, for example, at a temperature range of 550 to 800 ° C., and then water cooling or the like is used to prevent the γ phase from being precipitated or the γ phase ratio By rapidly cooling at a cooling rate of 10% or less (including 0), the solidification structure can be significantly improved, and the corrosion resistance and mechanical properties can be significantly improved. It is considered that each property of the solidified structure is improved by the solid solution of a large amount of Sn in the β phase, which is said to have poor corrosion resistance. Quenching allows for a thin ceramic shell and a small cavity inner diameter.

The above-mentioned cast member after casting is
In order to make full use of the characteristics of the γ phase such as improved wear resistance and machinability, it is reheated at a temperature of 520 ° C or higher at which the γ phase once disappears, and then air-cooled (de-cooled) It is possible to form a structure in which the γ layer is uniformly dispersed.

In order to further improve the cooling efficiency, the ceramic shell is made of W / Co / Ni and heat-resistant alloy fiber or powder, which is a material having excellent thermal conductivity and higher than the melting point of the molten metal, or fiber and powder. It is desirable to mix them. Specifically, the wax type is first coated with the ceramic alone to ensure heat resistance and to prevent the molten metal and metal powder or fiber from reacting and adhering to each other. The powder is mixed and made into a slurry to be adhered to form a layer for improving the thermal conductivity. Second
In the subsequent coating steps, metal powder or metal fibers are mixed on the basis of a slurry of SiO ₂ , CaCO ₃ , and Al ₂ O ₃ as the components of the slurry. At this time, since the specific gravity is different, it is necessary to stir until just before the immersion.

Here, the term "apparent Zn content" means that A is a Cu content [wt%], B is a Zn content [wt%], and a third element (for example, Sn) to which t is added. Z
When n equivalent and Q are the contents [wt%] of the third element, “{(B + t · Q) / (A + B + t · Q)} × 10
It is used to mean "0".

In the casting step, when pouring the molten metal into the cavity of the ceramic shell, it is desirable to perform centrifugal casting or pressure casting in order to secure the flow of molten metal and suppress evaporation of Zn. Using this method, the Pb
It is also possible to apply a composition in which Pb is removed from the composition of a bronze casting or a brass casting containing 0.5 to 10 of Sn, which was used to secure the molten metal flowability.

The cast member of the present invention having the above-mentioned γ phase has (1) a cutting resistance index of 50 or more, preferably 80 or more, based on a free-cutting brass rod according to Japanese Industrial Standard JISC-3604. , (2) Sn as a raw material composition
If it contains, the Japan Copper and Brass Association technical standard JBMAT
When performing the dezincification corrosion test according to −303, the maximum dezincification penetration depth direction is 100 μm or less when the maximum dezincification penetration depth direction is parallel to the processing direction, or the maximum dezincification penetration depth direction is the processing direction. Maximum dezincing depth is 70 when perpendicular to
It was less than μm. This characteristic is due to the existence of the γ phase, which has not been obtained in the conventional cast structure of brass.

It should be noted that, in addition to the characteristics listed here, excellent polishing characteristics can be exhibited. That is, regarding the abrasiveness, 1. When the polishing is performed under the same conditions, the surface roughness after polishing is smaller than that of the conventional material. 2. When polishing is performed under the same conditions, the polishing amount is larger than that of conventional materials. When polished under the same conditions, it is evaluated from the viewpoint that the appearance is not defective and the plating paste is good compared to the conventional material. As a result of evaluation from these viewpoints, the Sn-containing brass described above is evaluated. This is because the cast member is shown to be superior to the conventional brass and bronze cast members.

To quantify this polishing property, the plate material according to the present invention, after the heat treatment step, has a polishing apparatus of a Buehler ECOMET IV and a polishing plate rotation speed of 200 rp.
m, sample pressing pressure is 6.9 KPa, abrasive paper is SiC #
When the # 80 scratch is surface-polished under the condition of 600, polishing is completed in 1/2 time as compared with the brass cast material according to Japanese Industrial Standard JIS C-2700.

When the pipe material is cast, after the heat treatment step, the polishing apparatus is a Buehler ECOMET IV, the polishing plate rotational speed is 150 rpm, and the sample pressing pressure is 6.9 KP.
a, when the # 600 scratch is surface-polished under the condition that the polishing powder is Al2O3, it has the characteristic that the polishing is completed in 1/2 time compared with the brass plate material according to Japanese Industrial Standard JIS C-2700.

Further, by making the area ratio of the β phase 5% or more, the β phase, which is originally excellent in machinability and abrasivity, is effectively utilized to secure the machinability and the like. By setting the area ratio of the β phase to 40% or less, preferably 20% or less, corrosion resistance can be ensured.
The adjustment of the area ratio can be appropriately adjusted depending on the apparent Zn content.

Furthermore, the Sn concentration in the β phase is 1.5 wt.
If it is at least%, the β phase, which is originally inferior in corrosion resistance, can be strengthened to improve the corrosion resistance as a whole.

Further, by setting the area ratio of the γ phase to 1% or more, the machinability and the abradability at the interface between the hard γ phase and other phases are effectively utilized while securing the machinability and the like. The strength of the γ phase is utilized to improve the strength, and it is preferable to reduce the brittleness of the γ phase by setting the area ratio of the γ phase to 30% or less.

Further, the average crystal grain size (minor axis) of the γ phase is set to 8 μm.
When it is m or less, preferably 5 μm or less, the brittleness of the γ phase can be further reduced, but the Sn concentration of the γ phase is 8 w.
If it is t% or more, the corrosion resistance is also improved. In particular, when the β phase is contained, by surrounding the β phase with the γ phase having a Sn concentration of 8 wt% or more, the β phase which is originally inferior in corrosion resistance can be protected and the corrosion resistance can be improved as a whole. Also,
Machinability can be significantly improved by performing crystal control including optimization of the γ phase shape by heat treatment, and the synergistic effect of Sn-containing brass that does not contain Pb has a shorter cutting time than before. It becomes possible to

[0031]

As described above, according to the present invention, the Sn content is large,
Even with a copper alloy that does not contain Pb, a good quality cast member can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

[Explanation of symbols]

1 Water meter body 2 water inlet 3 outlets

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22D 27/09 B22D 27/09 A 29/00 29/00 G C22C 9/04 C22C 9/04

Claims (9)

[Claims] 1. A Sn content of 0.5 to 10 wt.
A copper alloy cast member, characterized in that a copper alloy cast member having a b content of 0.01 wt% or less is formed by precision casting. 2. The apparent Zn content is 33.5 to 43w.
A copper alloy cast member having a Sn content of 0.5 to 8.0 wt% at t% and a wall thickness of 0.5 mm to 4 mm. 3. Apparent Zn content is 33.5 to 43w.
It is a copper alloy cast member having a Sn content of 0.5 to 8.0 wt% at t%, a thickness of 0.5 mm to 4 mm, and a γ phase residual ratio after casting of 10% or less. A copper alloy cast member characterized by being present. 4. As a raw material composition, apparent Zn content is 33.5 to 43 wt% and Sn content is 0.5 to 8.0 w.
It is a copper alloy cast member having a thickness of 0.
A copper alloy cast member having a size of 5 mm to 4 mm and having the following characteristics. Japan Copper and Brass Association Technical Standard J
When performing the dezincification corrosion test according to BMA T-303, when the maximum dezincification penetration depth direction is parallel to the processing direction, the maximum dezincification penetration depth is 100 μm or less, or the maximum dezincification penetration depth direction If is perpendicular to the processing direction, the maximum dezincing depth should be 70 μm or less. 5. A step of preparing a copper alloy casting material made of a copper alloy containing no lead, the molten metal of the copper alloy casting material being cast under pressure into a cavity diameter of a precision casting mold of 0.5 mm to 4 mm. A method for manufacturing a copper alloy cast member, which comprises at least a step. 6. The apparent Zn content is 33.5 to 43w.
a step of preparing a copper alloy casting material having a Sn content of 0.5 to 8.0 wt% at t%, a cavity diameter of a precision casting die heated to a molten metal of the copper alloy casting material 0.5 mm to 4 mm
And at least a step of casting under pressure, the method for producing a copper alloy cast member. 7. The method for producing a copper alloy cast member according to claim 5, wherein the precision casting mold is a mold utilizing a lost wax method. 8. The copper alloy casting according to claim 6, wherein the casting mold is maintained at a temperature equal to or higher than the melting point of the copper alloy until the casting step is completed, and is rapidly cooled after the casting step is completed. A method of manufacturing a member. 9. The copper alloy casting member is demolded from the casting die after the quenching treatment, and then the copper alloy casting member is heated to 520 ° C. or higher and gradually cooled. A method for producing the copper alloy cast member described.