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[Name of Document] DESCRIPTION
[Title of the Invention] BRONZE-BASED ALLOY OF LOW LEAD
CONTENT
[Technical Field]
[0001]
The present invention relates to a bronze-based alloy of low lead
content suitable as a material for plumbing instruments, such as valves or
joints for water supply, hot water supply or steam emission, pressure
instruments, such as cylinders or casings, or structural members and
particularly to a bronze-based alloy of low lead content improved in tensile
strength at high temperatures and capable of contributing to the soundness
of a casting.
[Background Art]
[0002]
A bronze casting (JIS H5120 CAC406) is generally excellent in
castability, corrosion resistance, machinability and pressure resistance and
has numerously been used for plumbing instruments for water supply, hot
water supply and steam emission, such as valves, cocks and joints. The
bronze casting (CAC406) contains several % of Pb (lead) and contributes
particularly to the enhancement of machinability and pressure resistance.
In recent years, however, it has been recognized that even low-concentration
Pb might adversely affect human bodies, resulting in trends toward the
establishment of regulations in various fields over the world, such as
regulations for the leaching of Pb into tap water, discharge of Pb-containing
waste and content of Pb in a material to be used. Under these
circumstances, there has been an urgent need to anew develop useful
leadless copper alloys. Of these alloys, various materials including Bi-based,
Bi-Sb-based and Bi-Se-based alloys have been developed.

-2-
[0003]
For example, JP-B HEI 5-63536 (Patent Document 1) discloses a
leadless copper alloy substituting Bi for lead to enable the enhancement of
cuttability and the prevention of dezincification. In Japanese Patent No.
2889829 (Patent Document 2), disclosed is a leadless bronze to which Sb is
added to enable the suppression of the generation of porosities during the
course of casting in consequence of the addition of Pb for enhancing the
cuttability, thereby achieving the enhancement thereof in mechanical
strength. In addition, U.S. Patent No. 5614038 (Patent Document 3)
discloses a bronze alloy having Se and Bi added thereto to particularly
deposit a Zn-Se compound thereon, thereby making the mechanical
properties, cuttability and castability thereof substantially identical with
those of CAC406.
[Patent Document 1] JP-B HEI 5-63536
[Patent Document 2] Japanese Patent No. 2889829
[Patent Document 3] U.S. Patent No. 5614038
[Disclosure of the Invention]
[Problems the Invention intends to solve]
[0004]
In the leadless bronze casting having Bi added thereto as a
substitute component for Pb, as in the above Patent Documents, where it
contains a slight amount of Pb, when the casting material has been exposed
to such a high temperature as exceeding 1000°C, among other mechanical
properties the tensile strength is possibly lowered. It is conceivable as one
of the causes thereof that Bi and Pb exist as Bi-Pb binary eutectic crystals of
low melting point in the crystal grain boundaries and in the crystal grains
where portions fragile at high temperatures are formed. There is the same
trend toward the generation of these phenomena in various materials having
Bi added thereto, such as Bi-based, Bi-Sb-based and Bi-Se-based materials.

-3-
The applicant of this application proposed in the previously filed
application No. PCT/JP2004/4757 the technique of having Te contained in an
alloy to materialize the enhancement of mechanical properties at high
temperatures. However, since a bronze casting used for valves for steam
emission etc. is required to have a prescribed tensile strength even at a high
temperature of approximately 180°C, a further improvement in tensile
strength at high temperatures and in mass-productivity by dint of use of
more numbers of general-purpose alloy components has been desired.
[0005]
As the technique of suppressing the production of Bi-Pb binary
eutectic crystals and improving the tensile strength at high temperatures, a
technique of super reduction making the Pb content approximate to zero is
conceivable. In major cases, however, conventional casting equipment for
producing CAC406 is used concurrently for the mass-production of leadless
copper alloys and, in such a case, there is a possibility of interfusion of Pb
from a furnace and a ladle. In addition, since leadless copper alloys are
produced using recycled materials, such as scraps, or ingots comprising such
recycled materials and since these materials contain Pb mixed therein as an
unavoidable impurity, even when the casting equipment exclusive for
producing leadless copper alloys is used, it is unavoidable that Pb be mixed
in the leadless copper alloys. Under the present set of circumstances,
therefore, the content of Pb up to 0.25 mass % is allowable (for leadless
bronze valves prescribed under JIS B 2011). Thus, the technique of super
reduction making the Pb content approximate to zero is impractical from the
standpoints of mass-production and manufacturing cost.
[0006]
Here, as regards the tensile strength of ordinary bronze-based alloys
at high temperatures, though it is recognized that sand castings made of
bronze-based alloy has exhibited a decrease in tensile strength at high
temperatures, the experience shows that the continuously cast castings

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(about 28 mm in diameter) shown in Table 1 exhibit no decrease in tensile
strength at high temperatures in the approximate range of 100°C to 200°C
(refer to Figure 2V cited from "Industrial Technology of Leadless Copper
Alloy Castings and Their Applied Instances," The Materials Process
Technology Center, published October 15, 2004, pp. 35 an 37) However,
there is no material quantitatively grasping these phenomena over other
casting diameters or casting processes (Example: metal mold casting).
[0007]

[0008]
The present invention has been developed as the result of keep
studies made in view of the aforementioned problems and has as its object to
first improve the tensile strength of a bronze-base alloy of low lead content at
high temperatures, secondly provide a bronze-based alloy of low lead content
excellent in mass production while avoiding the adverse effect of lead on
human bodies owing to the reduction in the amount of lead and contributing
to the promotion of the environmental conservation including recycling and
further to secure the soundness of castings.
[Means for solving the Problems]
[0009]
To attain the above object, the invention set forth in claim 1 is
directed to a bronze-based alloy of low lead content, comprising 2.0 to 6.0
mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % <

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P < 0.6 mass % and the remainder of Cu and unavoidable impurities,
whereby the P increases grain boundary strength in the alloy to improve
tensile strength thereof at high temperatures.
[0010]
The invention set forth in claim 2 is directed to a bronze-based alloy
of low lead, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1
to 3.0 mass % of Bi, 0.1 mass % < P < 0.6 mass %, 0.0 mass % < Ni < 3.0
mass % and the remainder of Cu and unavoidable impurities to improve
tensile strength thereof at high temperatures and secure soundness of a
casting.
[0011]
The invention set forth in claim 3 is directed to a bronze-based alloy
of low lead content, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of
Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % < P < 0.6 mass %, 0.0 mass % < Se <
1.3 mass % and the remainder of Cu and unavoidable impurities to improve
tensile strength thereof at high temperatures and secure soundness of a
casting.
[0012]
The invention set forth in claim 4 is directed to a bronze-based alloy
of low lead content, comprising 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of
Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % < P < 0.6 mass %, 0.0 mass % < Ni <
3.0 mass %, 0.0 mass % < Se < 1.3 mass % and the remainder of Cu and
unavoidable impurities to improve tensile strength thereof at high
temperatures and secure soundness of a casting.
[0013]
The invention set forth in claim 5 or claim 6 is directed to a
bronze-based alloy of low lead content, further comprising 0.005 to 2.0
mass % of Pb to secure a tensile strength of at least 152 MPa at a
temperature of 180°C in an alloy region having a secondary dendrite spacing
of 14 um or more.

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The invention set forth in claim 7 is directed to a bronze-based alloy
of low lead content used as a material for a valve, water faucet clasp or water
meter.
[Effects of the Invention]
[0014]
According to the invention of claim 1, it has been made possible to
provide a bronze-based alloy of low lead content, improved in tensile
strength at high temperatures, contributing to the promotion of the
environmental conservation including recycling and excellent from the
standpoints of mass-productivity and manufacturing cost. The application
of the conventional leadless copper alloys has been limited to implements for
the supply of water or hot water having a principal temperature of 100°C or
less in use. However, the copper alloy of the present invention improved in
tensile strength at high temperatures can be developed to appropriate use of
the conventional bronze alloys over the general application, with no
restriction made on its application, and can enlarge the range of its
application as recycled materials and exhibits its effects from the viewpoints
of the manufacturing cost, not to mention the environmental conservation.
In particular, it is preferably applicable to alloys low in cooling velocity
during the course of casting, such as sand castings, and optimum for alloys
requiring a tensile strength of 152 MPa at a high temperature (about 180°C).
[0015]
According to the invention of claim 2, it has been made possible to
provide a bronze-based alloy of low lead content, suppressing a decrease in
tensile strength at high temperatures, contributing to the promotion of the
environmental conservation including recycling and excellent from the
standpoint of mass-productivity. In addition, it contains Ni as a principal
component to obtain P-Ni interaction, thereby suppressing the content of P
therein, enabling the tensile strength thereof to be 152 MPa at a high

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temperature (about 180°C) and obtaining the action of enhancing the tensile
strength thereof by means of the Ni using the content of 0 mass % < P < 0.6
mass %. While, in the "pressure container structure" under JIS B 8270, the
fundamental allowable stress of CAC 406-2 at 200°C is prescribed at 38 MPa,
the present invention makes it possible to secure even at high temperatures
152 MPa that is four times the prescribed value. While the excess content
of P in a casting has a tendency to lowering the soundness of the casting, the
P-Ni interaction enables the tensile strength at high temperatures to be
secured even in a small content of P, thereby also securing the soundness of
the casting to a satisfactory extent. Thus, it is possible to obtain an alloy
suitably usable for a pressure-resistant container, such as a valve.
[0016]
According to the invention of claim 3, it has been made possible to
provide a bronze-based alloy of low lead content, containing Se as a principal
component, suppressing the content of Bi and exhibiting its tensile strength
of 152 MPa at a high temperature (about 180°C). Since Se is present in the
alloy in the form of intermetallic compounds of Se-Zn and Cu-Se, it is
effective for securing the tensile strength and soundness of a casting while
suppressing the content of Bi. Thus, it is possible to obtain an alloy suitably
usable for a pressure-resistant container, such as a valve.
[0017]
According to the invention of claim 4, it has been made possible to
provide a bronze-based alloy of low lead content, containing Ni as a principal
component to suppress the contents of P and Bi and exhibiting its tensile
strength of 152 MPa at a high temperature (about 180°C).
[0018]
According to the invention of claim 5, it is made possible to provide a
bronze-based alloy of low lead content, which can secure an excellent tensile
strength even at high temperatures without being affected by the content of
Pb. As a result, the tensile strength at high temperatures can be secured

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without being affected by Pb interfused from a furnace and a ladle in the
case where the conventional casting equipment for producing CAC406 is
used concurrently for the mass-production of the alloys of the present
invention and without being affected by Pb interfused as an unavoidable
impurity in the case where the alloys of the present invention are produced
using recycled materials, such as scraps or ingots comprising such scraps.
[0019]
According to the invention of claim 6, it is made possible to provide a
bronze-based alloy of low lead content, applicable to an alloy low in cooling
velocity during the course of casting and making it possible to secure a
tensile strength of at least 152 MPa at 180°C in an alloy region having a
secondary dendrite spacing of 14 μm or more.
[0020]
According to the invention of claim 7, it is made possible to provide a
bronze-based alloy of low lead content, which exhibits a high tensile strength
even at high temperatures particularly for use as a material for a valve,
water faucet clasp or water meter and which is therefore highly practicably
valuable.
[Brief Description of the Drawings]
[0021]
[Figure l] It is a graph showing the relationship between the content
of P of the copper alloy of the present invention and the tensile strength
thereof at 180°C.
[Figure 2] It is a schematic view of a dendrite.
[Figure 3] It is a micrograph showing the typical microstructure of
CAC406.
[Figure 4] It is an explanatory view showing the measurement
method for secondary dendrite arm spacing.

-9-
[Figure 5] It is a graph showing the relationship between the
secondary dendrite spacing of alloys and the tensile strengths thereof at
normal room temperature.
[Figure 6] It is a graph showing the relationship between the
secondary dendrite spacing of alloys and the tensile strengths thereof at
180°C.
[Figure 7] It is a photograph showing the cut surface of a barrel part
of a small valve (a general-purpose gate valve of leadless bronze having a
nominal pressure of 10 K and a nominal diameter of 1/2).
[Figure 8] It is a photograph showing the cut surface of the barrel
part in Figure 7 that has been subjected to etching treatment with nitric
acid.
[Figure 9] It is a graph showing the relationship between the content
of Pb of the alloys and the tensile strength thereof at 180° C.
[Figure 10] It is a graph showing the relationship between the
content of Ni of the copper alloy of the present invention and the tensile
strength thereof at 180°C.
[Figure 11] It is a graph showing the relationship between the
contents of Ni and P of the copper alloys of the present invention and the
tensile strengths thereof at 180°C.
[Figure 12] It is a graph showing the influence of the Sb content on a
leadless copper alloy.
[Figure 13] It is an explanatory view showing a casting method
scheme for stepwise cast test pieces.
[Figure 14] It is an explanatory view showing the surface observed in
the visible dye penetrant testing for each stepwise cast test piece.
[Figure 15] It is a conceptual diagram showing the P-Ni interaction.
[Figure 16] It is a SEM photograph showing the alloy of the present
invention.

-10-
[Figure 17] (a) is an SEM photograph showing the alloy of the
present invention and (b) a photograph showing the texture of the fracture
surface of the same alloy.
[Figure 18] (a) is an SEM photograph showing the alloy in
Comparative Example, and (b) a photograph showing the texture of the
fracture surface of the same alloy.
[Figure 19] It is a diagram showing the microstructure of the alloy of
the present invention.
[Figure 20] (a) to (g) are photographs each showing the distribution of
the components of the alloy in Figure. 19 obtained by the EDX analysis.
[Figure 21] It is a graph showing the variation in tensile strength at
high temperatures with respect to a conventional continuous cast product.
[Best Mode for carrying out the Invention]
[0022]
The bronze-based alloy of low lead content according to the present
invention is characterized in that a casting material has P contained therein
to improve the tensile strength of the alloy at high temperatures.
Particularly, the present invention is characterized in that within an alloy
region having a secondary dendrite arm spacing interval of 14 μm or more in
an ordinary leadless bronze alloy containing Bi, the tensile strength is
improved at high temperatures exceeding 180°C and specifically in that the
tensile strength of 152 MPa at least at 180°C can be ensured. The
"bronze-based" alloy fundamentally comprises Sn, Zn, Bi, Cu and
unavoidable impurities and, as preferable bronze-based alloys of low lead
content, Cu-Sn-Zn-Bi-based alloys (hereinafter referred to as "Bi-based"
alloys) and Cu-Sn-Zn-Se-based alloys (hereinafter referred to as
"Bi-Se-based" alloys) can be cited.

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[0023]
The alloy of "low lead content" used in the present invention refers to
an alloy having a Pb content lower than a bronze alloy containing Pb
(CAC406 etc.) and not restricted to the content of Pb (0.25 mass % or less) as
the residual component of a lead-free (leadless) copper alloy prescribed by
JIS H5120 etc.
A "high-concentration P (phosphorus)" that will be used in the
present invention refers to P in an amount exceeding 0.1 mass % that is
larger than the amount of the residual P in the prior art.
The "P-Ni interaction" used in the present invention refers to a
synergistic effect enabling the ratio of the effect by an increase in P content
(enhancement in tensile strength) to be increased at high temperatures in
the presence of Ni.
Here, the "tensile strength" used in the present invention refers to
that evaluated with the Amsler tensile strength tester using the test piece
No. 4 prescribed by JIS Z2201 that will be described later.
The "soundness of the casting" used in the present invention refers to
the evaluation of the presence or absence of cast defects on the surface
observed in the visible dye penetrant testing using a stepwise cast test piece
that will be described later, made as acceptance if the evaluation is
substantially the same as that for CAC406 or is capable of being judged as
being in a state improvable by an amendment of a casting method scheme up
to substantially the same as that for CAC 406.
The range of each component content and the reason for it will be
described hereinafter.
[0024]
P: O.K P < 0.6 mass %
Generally, a copper alloy contains P in a relatively small amount of
0.01 mass % or more and 0.1 mass % or less. In order to promote the
deoxidation of a molten metal and making the flowability of the molten

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metal good, for example, a casting produced by the sand casting contains
residual P in an amount of 0.01 mass % or more and less than 0.1 mass %.
For example, the content of P as the residual component in CAC406 is 0.05
mass % or less. Also as shown in Reports of the 146th JFE Meeting, p. 30,
the content of P, even when being positively added to a copper alloy for the
purpose of preventing cast cracking, is 200 to 300 ppm (0.02 to 0.03 mass %).
The P in these examples is added to the molten metal in a casting furnace or
ladle, and the content of the residual P in a casting to be produced is 0.1
mass % or less.
As proposed in application No. PCT/JP2004/4757 cited above, the
alloy has P contained therein in an amount of 0.01 to 0.5 mass %, preferably
0.05 to 0.1 mass % to improve the tensile strength at 100°C.
Incidentally, though less than 0.5 mass % of P is generally added
with the aim of enhancing deoxidation of the molten metal to a molten metal
in performing a method for continuously casting a copper alloy, the P is
contained not positively in a cast product, and the content of P as the
residual P is not disclosed.
[0025]
On the other hand, the amount of P contained in the present
invention contributes to the enhancement of the tensile strength at a high
temperature (about 180°C) and belongs to a high-concentration range of P to
be positively contained, which range greatly surpasses the amount of P to be
added for the purpose of deoxidizing molten metal and preventing cast
cracking. The amount of the contained P exceeding 0.1 mass % can
heighten the grain boundary strength while suppressing the production of
Bi-Pb binary eutectic crystals, thereby contributing to the enhancement of
the tensile strength at high temperatures.
In Example 1 to be described later (relationship between the content
of P and the tensile strength at 180°C), it is preferred that the upper limit of
range in which P is contained and which satisfies the tensile strength of 152

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MPa be 0.4 mass % and that the lower limit thereof be 0.2 mass %.
Incidentally, the upper limit enables acquisition of the peak value of the
tensile strength at 180°C and, more preferably from the standpoint of const
for commercial production, the upper limit is 0.4 mass %. Also as a value
capable of securing the soundness of a casting in Example 5 to be described
later and without requiring any change to a great extent in the casting
method scheme during the commercial production, the upper limit is
preferably 0.4 mass %.
Also, in the case further containing Ni to be described later, the
interaction of the P and Ni enables the lower limit of the P content capable of
infallibly acquiring the tensile strength of 152 MPa at 180°C to be lowered.
From this point of view, the lower limit of the P content is set to be preferably
0.12 mass % and more preferably 0.14 mass % and, as a result, it is made
possible to acquire the tensile strength of 152 MPa at 180°C at the upper
limit suppressed to 0.33 mass %. Incidentally, it is effective to further
suppress the P content when requiring better soundness of a casting and, in
this case, the upper limit is preferably 0.2 mass %.
[0026]
Ni: 0.0 < Ni < 3.0 mass %
Generally, Ni in a copper alloy exhibits solubility into an a phase in
the alloy to strengthen the matrix thereof, thereby contributing to the
enhancement of mechanical properties of the alloy, the tensile strength
thereof in chief. JP-A 2003-193157, for example, proposes a technique
having 0.2 to 3.0 weight % of Ni contained in an alloy to secure the tensile
strength at normal room temperature substantially the same as that of
CAC406, in which a variation in tensile strength with an increase in Ni
content assumes a gentle-mountain-shaped characteristic wherein the
tensile strength reaches its peak when the Ni content falls in the range of 0.6
to 0.8 weight % in the exemplified alloy containing 0.01 to 0.02 weight % (130
to 200 ppm) of P (refer to Figure 1 thereof).

-14-
In addition, as shown in Comparative Example that will be described
later relative to Example 4 (relationship between the contents of P and Ni
and the tensile strength at 180°C), the leadless alloy containing P as the
residual P (0.1 mass % or less) exhibits no discernible change in tensile
strength at a high temperature (180°C) with an increase in Ni content.
On the contrary, the content of Ni in the present invention
contributes to the enhancement of the tensile strength at high temperatures
on the premise of the content of P at a high concentration exceeding 0.1
mass % and, as shown in Example 4 that will be described later, this
variation in tensile strength assumes a parabolic characteristic (with the
axis as an x-axis) wherein the P-Ni interaction greatly enhances the tensile
strength in the presence of a small amount of Ni content. Thus, even a
small amount of Ni content makes it possible to suppress the P content to
within a high-concentration range (0.1 < P < 0.6 mass %) and enhance the
tensile strength at high temperatures. This is extremely useful in due
consideration of the fact that P is easy to evaporate from molten metal to
make it difficult to control the P to a high concentration.
A concrete Ni content is only required to exceed 0 mass %. For
example, 0.05 or 0.08 mass % of Ni is available. It is preferred to use 0.1
mass % of Ni, thereby enabling the tensile strength of 152 MPa at a high
temperature (about 180°C) while suppressing the P content.
On the other hand, since the excess amount of Ni content allows the
enhancement of the tensile strength to be saturated, the upper limit of the
Ni content is set to be 3.0 mass %. When judging from Figure 10 (P = 0.32
mass %) the state of saturation in the enhancement of the tensile strength at
the preferable upper limit of P (0.4 mass%), it is better to adopt 2.0 mass %
as the upper limit of the Ni content. As the upper limit of the range
effectively enabling acquisition of the tensile strength even in a small
amount of Ni content in view of cost reduction, 0.1 mass % may be adopted.
Further in view of enabling the tensile strength of at least 152 MPa to be

-15-
obtained at a high temperature (about 180°C), it is better that the lower
limit of the Ni content be 0.3 mass % and that the upper limit thereof be 0.6
mass %.
[0027]
Bi: 0.1 to 3.0 mass %
This component is a substitute for Pb, has a low melting point and
enters minute shrinkage cavities called microporosities produced in portions
being finally solidified in the dendrite spacing of an alloy (casting) during the
course of solidification of the casting, thereby enhancing the alloy soundness
(resistance to pressure) and contributing to the ensuring of cuttability.
While 0.1 mass % or more of Bi is effective for enhancing the cuttability, an
alloy is required to contain 0.25 mass % of Bi in addition to the inclusion of
Se in order to reduce the number of microporosities and secure its soundness.
The excessive content of Bi, however, induces "inverse segregation" allowing
the Bi to be concentrated together with Sn or high-concentration P on the
surface of a casting during the course of the solidification of the casting and,
in this case, there is a possibility of the number of microporisities in the
casting being increased. Therefore, it is effective that the upper limit of Bi
be set to be 3.0 mass % to secure the soundness of the alloy.
When it is required to effectively reduce the further number of
microporosities, such as for the application requiring the resistance to
pressure, it is effective that the lower limit of the Bi be 0.4 mass % and that
the upper limit thereof be 2.5 mass %. Furthermore, in order to enable the
mechanical machining under substantially the same cutting conditions as in
the case of CAC406, the lower limit is preferably 1.0 mass%.
Incidentally, since an excessive content of Bi lowers the tensile
strength, when necessitating infallible securement of the tensile strength at
high temperatures at a level of commercial production, the upper limit of Bi
is preferably 2.6 mass %. In addition, when making much of cost reduction
in the commercial production, it is preferable to set the upper limit of Bi to be

-16-
2.0 mass %.
[0028]
Zn: 3.0 to 10.0 mass%
This component is for enhancing hardness and other mechanical
properties, particularly elongation, without imparting the influence of
cuttability to an alloy. The content of Zr in an amount of 3.0 mass % or
more promotes deoxidation of the molten metal effectively and enables the
soundness of a casting and the flowability of the molten metal to be
enhanced. Since Zr is comparatively inexpensive, though it is a component
desirably contained in an amount as many as possible, the upper limit
thereof is fixed at 10 mass % in view of possible deterioration of the casting
environment by a vapor of Zn.
Then, when intending to infallibly acquire the deoxidation effect by
Zn, the upper limit thereof is preferably 4.0 mass %. Furthermore, in the
case of requiring the vapor pressure of Zn to be lowered taking particular
note of the filling property of the molten metal in a casting mold, the upper
limit thereof is preferably 9.0 mass %. Incidentally, in view of the fact that
the optimum lower limit of Sn is 2.8 mass % described later, preferably the
lower limit of a range of Sn not allowing the deposition of a 8 phase is 6.0
mass %.
[0029]
Sn: 2.0 to 6.0 mass%
This component is for contributing to the enhancement of mechanical
properties of an alloy, especially elongation and corrosion resistance, and the
effective content thereof is 2.0 mass % or more. In consideration of the fact
that Sn allows deposition of a hard and brittle 8 phase and makes the
machine workability and elongation lower and further of its cost, the upper
limit thereof is fixed at 6.0 mass%.
When requiring substantially the same tensile strength as CAC406,
the effective content of Sn is 2.8 mass % or more. Furthermore, in case

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where it is necessary to suppress the inverse segregation of solutes, such as P,
Bi and Sn, even under different casting conditions during commercial
production, the upper limit of Sn is preferably fixed at 5.5 mass %.
Incidentally, in order to acquire a peak value of the tensile strength taking
particular note of the tensile strength, the advantageous upper limit thereof
is 4.5 mass %.
[0030]
Se:0.0
The compositions thereof consist of 3.0 to 6.0 (preferably 3.1 to 5.9)
mass % of Sn, 4.0 to 9.0 (preferably 8.3) mass % of Zn, 1.0 to 3.0 (preferably
1.3 to 2.2) mass % of Bi, 0.2 to 0.5 mass % of Se, 0.20 (preferably 0.22) to 0.50
mass % of P and the balance of Cu and unavoidable impurities.

-22-

The compositions thereof consist of 3.0 to 6.0 (preferably 5.8) mass %
of Sn, 4.0 to 9.0 (preferably 8.4) mass % of Zn, 1.0 to 3.0 (preferably 1.1 to 2.2)
mass % of Bi, 0.20 to 0.40 (preferably 0.22 to 0.27) mass % of P and the
balance of Cu and unavoidable impurities.
[Example 2]
[0039]
Next, the tensile strengths of bronze-based copper alloys of low lead
content at high temperatures are quantitatively grasped to show the ranges
of the components of the alloys in compliance with the present invention and
verify the effects of the present invention.
It is generally known that the tensile strength of an alloy has
relationship with the size of the microstructure thereof. In view of this, the
present test used the secondary dendrite arm spacing as a criterion showing
the size of the microstructure of an alloy. Here, the term "dendrite" means
one of the crystal-growth modes in the metallic solidification. Figure 2 is a
schematic view showing the dendrite, in which when the stem is defined as a
primary dendrite arm (primary branch) and the branches produced from the
primary branch as secondary dendrite arms (secondary branches). It has
been known that the dendrite arm spacing has a great influence on the
mechanical properties etc. of a casting. Figure 3 is a micrograph showing
the typical microstructure of CAC406, from which it can be observed that the
secondary dendrite arms have been well developed and well aligned.
[0040]
Therefore, the secondary dendrite arms were measured using the
measurement method for secondary dendrite arm spacing to evaluate the
size of the microstructure. The measurement method for secondary
dendrite arm spacing is a method for measuring the average spacing in the
well-aligned dendrite arms as shown in Figure 4(a). To be specific, a search
is made, from the microstructure, for dendrite arms grown as aligned in

-23-
parallel, then a line of optional length substantially orthogonal to the
dendrite arms is drawn, and the length L of the line intersecting the dendrite
arms is divided by the number (n - l) of the dendrite arms to obtain a
quotient ds. That is to say, the size of the secondary dendrite arms is
expressed as L/(n - l). Incidentally, the microstructures of a test piece
casting differ in size from one locality to be observed to another and, since
the test piece casting has a polycrystalline structure, the individual crystal
grains show different ways to grow the dendrite arms. In the present test,
the methods for measuring the secondary dendrite arm spacing of the test
pieces are unified as described below. Furthermore, when failing to observe
clear crystal grain boundaries in the actually cast product, item 3 below is
applied.
[0041]
1. Localities to be observed:
JIS No. 4 tensile test pieces, gauge mark parts and axial transverse
sections.
2. Localities to be measured:
The localities in which the secondary dendrite arms are aligned in
the individual crystal grains near the center of the axial transverse section of
a test piece as shown in Figure 4(b) are specified, and three or more crystal
grains in total are measured.
3. Number of dendrites measured:
30 dendrites each having five or more dendrite arms aligned.
Figure (4c) illustrates an example of the measurement of CAC306.
Since the average value of the secondary dendrite arm spacing is converged
when the number of the dendrites exceeds 10, the influence caused by the
difference in locality to be measured can be eliminated.
[0042]
In the tests based on the above method, the tensile strengths of
castings at normal room temperature and at a high temperature, which

-24-
casting were divided into sand castings, metal mold castings and
continuously cast castings, were verified. The compositions of samples are
shown in Table 5 (normal room temperature) and Table 6 (high temperature).
The test results are shown in these tables and plotted in Figure 5 (normal
room temperature) and Figure 6 (high temperature). Incidentally, the
normal room temperature used in this Example is about 23°C and this is
applicable to other Examples.

-27-
[0045]
It is found from the test results that the smaller the secondary
dendrite arm spacing, the smaller the degree of decrease in tensile strength
at 180°C. In the meantime, though it has conventionally been common
knowledge that the tensile strength of a continuously cast casting is not
lowered, as is clear from the test results, it has been confirmed that the
tensile strength of the continuously cast casting is lowered depending on the
diameter thereof. In particular, the castings having a large diameter
lowered their tensile strengths. It is conceivable that the reason for it is
that a casting of a larger diameter causes the cooling rate thereof to be
delayed to make the secondary dendrite arm spacing larger.
Here, the "continuously cast casting" is molded by means of
"continuous casting" that continuously extracts solidified castings from
below while pouring molten metal from above into a hollow and vertical
metal mold, for example. The solidification of molten metal is promoted
with cooling equipment, such as water-cooling.
On the contrary, the "sand casting" is molded by means of "sand
casting" that pours molten metal into a casting mold formed of solidified
casting sand, leaves the molten metal standing to cool it with air and takes
solidified metal part out of the casting mold, and the "metal mold casting" is
molded by means of "metal mold casting" that pours molten metal into a
casting mold formed of metal, leaves the molten metal standing to cool it
with air and takes solidified metal part out of the casting mold. Though the
cooling rates of castings differs depending on the difference of the methods of
casting, size of castings and scheme of casting methods, since the "sand
casting" and "metal mold casting" used in the present example adopted
slower cooling rates than the "continuously cast casting," the secondary
dendrite arm spacing was further widened to possibly lower the tensile
strength.

-28-
[0046]
On the other hand, it is found that the copper alloys of the present
invention are improved in tensile strength at high temperatures so as not to
be lowered without being affected by the secondary dendrite arm spacing.
That is to say, the copper alloys of the present invention are those improved
in tensile strength at high temperatures without being affected by the
difference in method of casting (cooling rate). In other words, it is found
that these alloys are those improved in tensile strength at high temperatures
while permitting the manufacture thereof even through the use of the
conventional method of casting (cooling rate). In addition, since the copper
alloys of the present invention exhibits a tendency similar to that of CAC406
as shown in Figures 5 and 6, they can secure the tensile strength up to high
temperatures as a substitute for CAC406.
[0047]
Incidentally, since the secondary dendrite arm spacing at the target
value of 152 MPa during the course of the transit in tensile strength of
leadless copper alloy at a high temperature (180°C) is around 14 μm, as
shown in Figure 6, this spacing of 14 μm has been determined as a boundary
reference value in the alloy region suitable for the copper alloys of the
present invention. According to the copper alloys of the present invention,
therefore, it is made possible to secure the tensile strength of at least 152
MPa at 180°C within the alloy region exhibiting a secondary dendrite arm
spacing of 14 μm or more.
[0048]
Here, the actual products are tested for the secondary dendrite arm
spacing. Particularly, adopted were small-sized valves (pressure resistance:
10 K, nominal diameter: 1/2, general-purpose gate valves of leadless bronze,
sand castings). Figure 7 is the cut surface of a barrel part, and Figure 8
shows the same cut surface after being subjected to etching treatment with
nitric acid. Sections (alloy regions) 1, 2 and 3 of different-thickness walls

-29-
have secondary dendrite arm spacing of 27.9 μm, 24.7 μm and 23.4 μm,
respectively. Since any of these has an arm spacing exceeding 14 μm,
ordinary sand cast products can be judged as objects to be improved.
Incidentally, a section having an arm spacing of 14 μm or more may be part
(alloy region) of a casting and, in this case, the whole of a casting part
constitutes an object to which the copper alloy of the present invention is
applied.
[0049]
The method of measurement comprises, as shown in Figure 8,
etching treatment, use of an electron microscope in a state wherein an
understanding of the metal texture is made easy to measure the secondary
dendrite arm spacing. Thus, even in one casting, the difference in thickness
induces a difference in secondary dendrite arm spacing and, therefore, it is
made possible to quantitatively grasp the tensile strength of local alloy
regions and make acceptance/rejection criteria of products resulting from the
tensile strength.
[Example 3]
[0050]
Next, the relationship between the Pb content and the tensile
strength at 180°C was verified with respect to the copper alloys of the
present invention (Bi-Se-based alloys). The composition of each sample is
shown in Table 7 and plotted in Figure 9. Incidentally, each sample was
collected from a sand casting.

-30-
[0051]
[Table 7]

[0052]
It is found from the present test results that in the copper alloys of
the present invention containing a high concentration of P, while an increase
in Pb content allows a gradual decrease in tensile strength, no discernible
decrease in tensile strength is found when the Pb content exceeds 0.5 mass%
and that the target value of 152 MPa at 180°C can substantially be secured.
On the other hand, in leadless copper alloys shown as Comparative
Examples, the tensile strength is conspicuously decreased and, when the Pb
content exceeds 0.005 mass %, the target value of 152 MPa at 180°C cannot
be satisfied. Thus, the alloys of the present invention makes it possible to
secure high tensile strengths at high temperatures even in the presence of

-31-
Pb and, therefore, are useful as recycled materials.
[Example 4]
[0053]
Next, the relationship between the Ni content and the tensile
strength at 180°C was verified with respect to the copper alloys of the
present invention (Bi-based alloys). The composition of each sample is as
shown in Table 8 and the test results are shown in the same table and
plotted in Figure 10. Incidentally, each sample in Example 4 was obtained
from a sand casting.
[0054]
[Table 8]


-32-
[Appendix Table 8]

[0055]
It was found from the present test results that addition of Ni to the
copper alloy of the present invention containing P in a high concentration
enhanced the tensile strength both at normal room temperature and at high
temperatures. It can be confirmed particularly from Figure 10 that when
the Ni content is in the range of 0.1 to 3.0 mass %, the target value of 152
MPa is secured.
Next, the tensile strengths at normal room temperature and at 180°C
were verified with respect to each of the following samples. Indicated by
Nos. 4-11 to 16 are samples of the copper alloys of the present invention
(Bi-based alloys), with the contents of the principal components of Sn, Zn and
Bi varied and with the contents of the characterizing components of P and Ni
varied. In addition, indicated by Nos. 4-17 and 18 are samples of the copper
alloys of the present invention (Bi-Se-based alloys), with the contents of the
principal components of Bi and Se varied, and by Nos. 4-19 and 20 are
samples of Comparative Examples, with the content of the principal
component Zn increased.

-33-
[0056]
Furthermore, here, the tensile strengths at 180°C were verified with
respect to the copper alloys of the present invention (Bi-based alloys)
containing 0.14 mass %, 0.22 mass %, 0.28 mass% and 0.32 mass %,
respectively, of P having added thereto 0, 0.20 mass %, 0.40 mass% and 0.60
mass %, respectively, of Ni. As Comparative Examples, those of the alloys
containing 0.02 mass % and 0.10 mass %, respectively of P were measured.
The composition of each sample is shown in Table 9 and the test results are
shown in the same table and plotted in Figure 11.
[0057]
[Table 9]


-34-
[0058]
It was confirmed from the present test results that in respect of the
tensile strengths at high temperatures the higher the concentration of the P
content, the larger the feature-enhancing effect of the Ni content was and
therefore that there was an interaction of P and Ni. To be specific, in
Comparative Examples having a P content of low concentration, the
enhancement in tensile strength even in the presence of Ni was small,
whereas the samples containing P in a concentration exceeding 0.10 mass %
were greatly enhanced in tensile strength in the presence of an Ni content.
Particularly, in the samples containing P in a concentration exceeding 0.16
mass %, the addition of the Ni content particularly in the range of 0.16 to
0.61 mass % in accordance with the characteristics shown in Table 9 and
Figure 11 to the samples enabled the target value of 152 MPa in tensile
strength to be obtained.
[0059]
Considering Table 8, Appendix Table 8 (Brbased alloys) and Table 9,
it is found from the test results that Examples having the following
composition range can achieve the target value of 152 MPa in tensile
strength at a high temperature (180°C) in consequence of having contained a
high concentration of P therein.

The compositions thereof consist of 2.0 to 6.0 (preferably 2.3 to 5.7)
mass % of Sn, 6.0 to 10.0 (preferably 6.5 to 9.5) mass % of Zn, 0.1 to 3.0
(preferably 2.6) mass % of Bi, 0.12 to 0.40 (preferably 0.33) mass % of P, 0.1
to 3.0 mass % of Ni and the balance of Cu and unavoidable impurities.
Incidentally, BrSe-based alloys containing 0.1 to 1.3 mass % of Se in
addition to the components of the Brbased alloy can be applied to the
present invention.
Figure 15 is a conceptual diagram showing the P-Ni interaction. As
compared with the alloy of Comparative Example containing P of low

-35-
concentration (0.1 < P), the copper alloy of the present invention containing P
of high concentration (0.1 < P < 0.6) is enhanced in tensile strength at high
temperatures (refer to A in Figure 15). On the contrary, when containing Ni
in addition to P, the alloy of Comparative Example containing P of low
concentration exhibits a slight increase in tensile strength at high
temperatures (refer to C in Figure 15), whereas the copper alloy of the
present invention containing P of high concentration exhibits a large
increase in tensile strength at high temperatures to the neighborhood of the
tensile strength at normal room temperature (refer to B in Figure 15). Thus,
the P-Ni interaction implies a synergistic effect (refer to B and C in Figure
15) of increasing an enhancing ratio of the effect with an increase in P
content (tensile strength) at high temperatures owing to the presence of Ni.
[Example 5]
[0060]
Next, the copper alloys of the present invention were tested for
casting soundness and the test results will be described. Figure 13 is an
explanatory view showing the casting method scheme for stepwise cast test
pieces, and Figure 14 an explanatory view showing the location of each test
piece measured.
By the casting method scheme for the stepwise casting test pieces
shown in Figure 13, samples numbered 5-1 to 17 were cast. Each of the
castings obtained was cut to obtain a test piece shown in Figure 14. The cut
surface of each test piece was polished and then subjected to the visible dye
penetrant testing. The "visible dye penetrant testing" comprises the steps
of spraying a penetrant onto the cut surface of a test piece, leaving the
penetrant standing for 10 minutes, then wiping away the penetrant, further
spraying a developer onto the cut surface having the penetrant wiped away
to determine the presence or absence of casting defects from red marks
having emerged on the cut surface. The casting method scheme for the
stepwise test piece comprises the step of pouring molten metal from the side

-36-
of the stepwise part having a wall thickness of 40 mm via a gate riser
measuring 70 mm in diameter x 160 mm in length starting with a pouring
gate having a diameter of 25 mm. The casting conditions include
performing resolution in an experimental high-frequency furnace, using a
meltage of 12 kg, adopting a pour point of 1180°C and using a C02 casting
mold.
[0061]
Indicated by Nos. 5-1 to 7 shown in Table 10 are samples of the
copper alloys of the present invention (Brbased alloys), with the contents of
the principal components of Sn and Zn varied and the content of the
characterizing component of P in the present invention varied.
Then, Indicated by Nos. 5-8 to 17 are samples of the copper alloys of
the present invention (Bi-based alloys), with the contents of the principal
components of Sn, Zn and Bi varied and the contents of the characterizing
components of P and Ni varied. In addition, indicated by Nos. 5-18 to 20 are
samples of the copper alloys of the present invention (Bi-Se-based alloys),
with the contents of the principal components of Sn, Zn and Bi varied and
the contents of the characterizing components of P and Ni in the present
invention varied.
Furthermore, when considering Table 10, the samples containing
about 0.36 mass % of P (Nos. 5-1 to 3, 19 and 19) are confirmed to have slight
defects with respect to their stepwise casting test pieces, but are the samples
improvable in consequence of correcting the casting method scheme in
manufacturing products to be mass-produced, such as valves etc.
Moreover, with respect to the samples containing Ni, the samples
containing P in a high concentration of 0.31 mass % (Nos. 5-8 and 9) were
confirmed to have no defect and obtain good castings. It is found from the
present test results that in the examples having the following ranges of
components, it is made possible to achieve the target value of tensile
strength that is 152 MPa at a high temperature (180°C) owing to the

-37-
presence of a high concentration of P and as well secure the casting
soundness.

The compositions thereof consist of 2.5 (preferably 2.9) to 6.0 mass %
of Sn, 4.0 (preferably 3.9) to 8.0 mass % of Zn, 0.5 to 3.0 (preferably 2.5
mass % of Bi, 0.15 to 0.40 (preferably 0.36) mass % of P, 0 < Ni < 2.0
(preferably 1.9) and the balance of Cu and unavoidable impurities.
Incidentally, with respect to the Bi-Se-based alloys, those containing
Se in the range of 0.1 to 1.3 in addition to the components of each of the
Bi-based alloys are available.
[0062]
[Table 10]


-38-
[Example 6]
[0063]
(Cuttability Test)
The pieces subjected to cuttability test were evaluated by machining,
with a lathe, cylindrical substances to be machined and using a cuttablity
index in the cutting resistance exerted on a turning tool when the cutting
resistance of a bronze casing CAC406 was regarded as 100. The test
conditions include using the pour point of 1160°C (in the C02 casting mold),
the shape of the substance to be cut measuring 31 mm in diameter and 300
mm in length, 3.2 as the surface coarseness RA, 3.0 mm as the cut depth,
1800 rpm as the number of revolutions of the lathe, 0.2 mm/rev as the
feeding amount and no oil.
The results of the cuttability test are shown in Table 11.
[0064]
[Table 11]

[0065]
Indicated by Nos. 6-1 to 4 are samples of the copper alloys of the
present invention (Bi-based alloys) and by Nos. 6-5 to 11 ate samples of the
copper alloys of the present invention (Bi-Se-based alloys).

-39-
Any of these samples satisfies an index of 80% or more processible by-
processing equipment, with a blade and under cutting conditions for use in
processing CAC406 and is found to be proccessible under substantially the
same cutting conditions as for CAC406.
5 [Example 7]
[0066]
(Gap Jet-Flow Corrosion Test)
Erosion and corrosion are evaluated by means of the gap jet-flow
corrosion test. The test procedure comprised mirror-polishing a test piece
10 that had been machined to have an exposed area of 64 mm2 (16 mm in
diameter) relative to corrosive liquid, then jetting a test solution (a 1% cupric
chloride solution) onto the exposed area part of the test piece at a rate of 0.4
l/min for five hours from a jet nozzle (nozzle diameter: 1.6 mm) disposed at a
height of 0.4 mm from the surface of the test piece and measuring the
15 maximum corrosion depth in the corroded surface.
Indicated by Nos. 7-1 to 3 shown in Table 12 are samples of the
copper alloy of the present invention (Bi-based alloys) that exhibited better
results than CAC406 and CAC401 shown as Comparative Examples.
[0067]
[Table 12]


-40-
[Example 8]
[0068]
(Tensile Test and Fracture Surface and Texture Evaluations)
The tensile test was performed in the same manner as in Example 1
(relationship between the P content and the tensile strength at 180°C) to
evaluate the tensile test pieces through the observation of the fracture
surface texture, observation of the microstructure and EDX analysis.
As shown in Table 13, indicated by No. 8-1 is a sample of the copper
alloy of the present invention (Bi-based alloy) containing P of high
concentration, by No. 8-2 is a sample of the copper alloy of the present
invention (Bi-based alloy) containing Ni to suppress the P content to within
the high-concentration range (0.1 < P < 0.6 mass %) and by No. 8-3 is a
sample of JIS H5120 CAC911 (Bi-Se-based bronze casting), as Comparative
Example, containing P in a low concentration of 0.02 mass%.
[0069]
[Table 13]

[0070]
SEM photographs and texture photographs of the facture surfaces of
the alloy samples that underwent the tensile test at 180°C are shown in
Figures 16 to 18. In the copper alloy of the present invention, as shown in
Figure 17(b), it is observed that the central portion of the fracture surface
has a fibrous texture and the peripheral portion thereof has a radial texture.
In addition, as shown in Figures 16 and 17(a), the SEM photographs show a
plurality of microscopic dimples (dents). It can therefore be considered that
"ductile fracture" would occur during the tensile test at 180°C.

-41-
On the other hand, the alloy of Comparative Example, as shown in
Figure 18, assumes "cleavage" along the crystal face (cleavage surface of
crystal) and no dimple can be observed from the SEM photograph. It can
therefore be considered that "brittle fracture" would occur during the tensile
test at 180°C.
Thus, owing to the presence of the P content in a high concentration,
the strength of the alloy at the crystal grain boundaries is enhanced at a
high temperature (180°C). This indicates that the "bristle fracture" is
converted into the "ductile fracture." This is applicable to the case of
containing Ni.
[0071]
Figure 19 shows the microstructure of the copper alloy of the present
invention (No. 8-2), and Figure 20 shows the distribution of the components
of the alloy of Figure 19 obtained by the EDX analysis. In the present
Example, the primary crystal a is grown in a dendrite form and, in the gap
thereof, a Brphase is observed. In the vicinity of the Bi-phase, a Cu-P
compound (CU3P) and an Ni-P compound (N13P) exist. Furthermore, since
the P and Ni assume solid solutions also in the crphase, they may possibly
enhance the matrix strength.
As a result of the above evaluations, therefore, it could be supported
by the observations of the fracture surfaces and textures of the samples that
the presence of P content in a high concentration brought about the effect of
enhancing the tensile strength at a high temperature (180°C) and that the
further presence of Ni content also brought about the effect of enhancing the
tensile strength at a high temperature (180°C) while suppressing the P
content to within a high-temperature range.
[Industrial Applicability]
[0072]
The bronze-based alloy of low lead content according to the present
invention is a copper alloy befitting various kinds of parts in a wide range of

-42-
fields, including a material for plumbing instruments (valves, joints, etc.) for
water supply, hot water supply or steam emission, pressure instruments
(casings etc.). Since the alloy of the present invention is an alloy enhanced
in tensile strength, it befits a material for parts of small wall thickness
including structural members as well as the plumbing instruments. It is
suitable for the process-formation of electric and mechanical products, such
as gas appliances, washing machines, air conditioners, etc. Other parts and
members having advantageously adopted the copper alloy of the present
invention as a material for them include water contact parts, such as valves,
water faucets, etc., namely ball valves, hollow balls for the ball valves,
butterfly valves, gate valves, globe valves, check valves, hydrants, clasps for
water heaters or warm-water-spray toilet seats, cold and hot-water supply
pipes, pipe joints, parts for electric water heaters (casings, gas nozzles, pump
parts, burners, etc.), strainers, parts for water meters, parts for underwater
sewer lines, drain plugs, elbow pipes, bellows, connection flanges for closet
stools, spindles, joints, headers, corporation cocks, hose nipples, auxiliary
clasps for water faucets, stop cocks, water-supplying, -discharging and
distributing faucet supplies, sanitary earthenware clasps, connection clasps
for shower hoses, gas appliances, building materials, such as doors, knobs,
etc., household electrical goods, adapters for sheath tube headers,
automobile air-conditioner parts, fishing-tackle parts, microscope parts,
water meter parts, measuring apparatus parts, railroad pantograph parts
and other members and parts. Furthermore, the copper alloy of the present
invention is widely applicable to washing things, kitchen things, bathroom
paraphernalia, lavatory supplies materials, furniture parts, family room
supplies materials, sprinkler parts, door parts, gate parts, automatic
vending machine parts, washing machine parts, air-conditioner parts, gas
welding machine parts, heat-exchanger parts, solar collector parts,
automobile parts, metal molds and their parts, bearings, gears, construction
machine parts, railcar parts, transport equipment parts, fodders,

-43-
intermediate products, final products, assembled bodies, etc.
The following applications can be cited as intended purposes usable
particularly at high temperatures.
1. (alloys used in environments requiring not so high resistance to
pressure)
Structural parts, such as burners, gas nozzles, flare nuts, ball taps,
thermostat parts, bolts, nuts, spindles and sliding parts (bearings, gears,
pushers, sleeves and worm gears).
2,
(alloys requiring strength and resistance to pressure:
Plumbing instruments and pressure instruments, such as
heat-exchangers (plates and tubes), gas turbines, atomic furnace parts,
industrial furnace parts (plumbing, valves and joints), seawater treating
facilities, (plumbing, valves, containers and joints), letdown valves,
electromagnetic valves, steam valves, safety valves, steam pipework,
water-heating instruments, steam generators, boiler parts (plumbing, pipes,
containers and joints), pump parts (casings, covers and impellers), steam
traps, drainpipes, valves for steam, floats, air-conditioner parts, (plumbing,
valves and joints), strainers for steam, hydraulic pump parts (casings and
impellers), air release pipes, electric water heater parts (plumbing, valves
and joints), hot-water containers, proportional valves, room heater parts,
carburetors, service valves, ball taps, tableware washers, water contact parts
for valves or water washing (ball valves, hollow balls for ball valves, butterfly
valves, gate valves, globe valves, check valves, feed pipes, connecting pipes,
pipe joints and strainers), headers, corporation stops, hose nipples, auxiliary
clasps for water faucets, stop cocks, water-supplying, -discharging and
distributing faucet supplies and adapters for sheath tube heads.
Incidentally, though clasps or auxiliary clasps for water faucet clasps,
water-feeding and hot-water feeding parts, etc. are not exposed to a

-44-
temperature of 100°C or more during ordinary use thereof, the copper alloy
of the present invention is of significance under the circumferences under
which cold water and hot water are alternately used or under which a high
temperature of 100°C or more by hot-air drying in a tableware washing and
drying apparatus etc. is used.

-45-
[Name of Document] SCOPE OF CLAIMS
[Claim 1]
A bronze-based alloy of low lead content, comprising 2.0 to 6.0
mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % <
P < 0.6 mass % and the remainder of Cu and unavoidable impurities to
improve tensile strength thereof at high temperatures.
[Claim 2]
A bronze-based alloy of low lead content, comprising 2.0 to 6.0
mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % <
P < 0.6 mass %, 0.0 mass % < Ni < 3.0 mass % and the remainder of Cu and
unavoidable impurities to improve tensile strength thereof at high
temperatures and secure soundness of a casting.
[Claim 3]
A bronze-based alloy of low lead content, comprising 2.0 to 6.0
mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % <
P < 0.6 mass %, 0.0 mass % < Se < 1.3 mass % and the remainder of Cu and
unavoidable impurities to improve tensile strength thereof at high
temperatures and secure soundness of a casting.
[Claim 4]
A bronze-based alloy of low lead content, comprising 2.0 to 6.0
mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass % of Bi, 0.1 mass % <
P < 0.6 mass %, 0.0 mass % < Ni < 3.0 mass %, 0.0 mass % < Se < 1.3 mass %
and the remainder of Cu and unavoidable impurities to improve tensile
strength thereof at high temperatures and secure soundness of a casting.

-46-
[Claim 5]
A bronze-based alloy of low lead content according to any one of
claims 1 to 4, further comprising 0.005 to 2.0 mass % of Pb to secure a tensile
strength of at least 152 MPa at a temperature of 180°C.
[Claim 6]
A bronze-based alloy of low lead content according to any one of
claims 1 to 4, that secures a tensile strength of at least 152 MPa at a
temperature of 180°C in an alloy region having a secondary dendrite spacing
of 14 μm or more.
[Claim 7]
A bronze-based alloy of low lead content according to any one of
claims 1 to 6, that is used as a material for a valve, water faucet clasp or
water meter.

The object of the present invention is to provide a bronze-based alloy
of low lead content, first improved in tensile strength at high temperatures,
secondly contributing to the promotion of the environmental conservation
including recycling, while avoiding the adverse effect of lead on human
bodies by means of reduction of a lead content, and excellent from the
standpoints of mass-productivity and manufacturing cost. The alloy
includes 2.0 to 6.0 mass % of Sn, 3.0 to 10.0 mass % of Zn, 0.1 to 3.0 mass %
of Bi, 0.1 mass % < P ≤ 0.6 mass % and the remainder of Cu and unavoidable
impurities to improve the tensile strength thereof at high temperatures.