U.S. patent application number 15/126085 was filed with the patent office on 2017-05-04 for low-lead brass alloy for use in member for water works.
This patent application is currently assigned to KURIMOTO, LTD.. The applicant listed for this patent is KURIMOTO, LTD.. Invention is credited to Syohei MATSUBA, Takeaki MIYAMOTO, Hiroshi YAMADA, Masaaki YAMAMOTO.
Application Number | 20170121791 15/126085 |
Document ID | / |
Family ID | 54240053 |
Filed Date | 2017-05-04 |
United States Patent
Application |
20170121791 |
Kind Code |
A1 |
YAMADA; Hiroshi ; et
al. |
May 4, 2017 |
LOW-LEAD BRASS ALLOY FOR USE IN MEMBER FOR WATER WORKS
Abstract
An object of the present invention is to provide a brass alloy,
in which the content of Bi is reduced to secure a good
recyclability while maintaining the dezincification corrosion
resistance required for a member for water works, and which is
capable of exhibiting an erosion-corrosion resistance and excellent
mechanical properties to be used as a member for water works. This
brass alloy contains: 24% by mass or more and 34% by mass or less
of Zn; 0.5% by mass or more and 1.7% by mass or less of Sn; 0.4% by
mass or more and 1.8% by mass or less of Al; 0.005% by mass or more
and 0.2% by mass or less of P; and 0.01% by mass or more and 0.25%
by mass or less of Pb; with the balance being copper and an
unavoidable impurity(ies).
Inventors: |
YAMADA; Hiroshi; (Osaka,
JP) ; YAMAMOTO; Masaaki; (Osaka, JP) ;
MIYAMOTO; Takeaki; (Osaka, JP) ; MATSUBA; Syohei;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KURIMOTO, LTD. |
Osaka |
|
JP |
|
|
Assignee: |
KURIMOTO, LTD.
Osaka
JP
|
Family ID: |
54240053 |
Appl. No.: |
15/126085 |
Filed: |
March 6, 2015 |
PCT Filed: |
March 6, 2015 |
PCT NO: |
PCT/JP2015/056671 |
371 Date: |
September 14, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 9/04 20130101 |
International
Class: |
C22C 9/04 20060101
C22C009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2014 |
JP |
PCT/JP2014/059499 |
Claims
1. A low-lead brass alloy for use in a member for water works, the
brass alloy comprising: 24% by mass or more and 34% by mass or less
of Zn; 0.5% by mass or more and 1.7% by mass or less of Sn; 0.4% by
mass or more and 1.8% by mass or less of Al; 0.005% by mass or more
and 0.2% by mass or less of P; and 0.01% by mass or more and 0.25%
by mass or less of Pb; with the balance being copper and an
unavoidable impurity(ies); wherein, in cases where the brass alloy
has a content of Sn of less than 1.0% by mass, the contents of Al
and Sn in % by mass satisfy the following Inequality (1):
Al+2.times.Sn.gtoreq.2.8 (1).
2. The low-lead brass alloy for use in a member for water works
according to claim 1, wherein the content of Sn is 1.0% by mass or
more.
3. The low-lead brass alloy for use in a member for water works
according to claim 1, further comprising 0.0005% by mass or more
and 0.015% by mass or less of B.
4. The low-lead brass alloy for use in a member for water works
according to claim 1, further comprising 0.1% by mass or more and
1.8% by mass or less of Ni.
5. The low-lead brass alloy for use in a member for water works
according to claim 2, further comprising 0.0005% by mass or more
and 0.015% by mass or less of B.
6. The low-lead brass alloy for use in a member for water works
according to claim 2, further comprising 0.1% by mass or more and
1.8% by mass or less of Ni.
7. The low-lead brass alloy for use in a member for water works
according to claim 3, further comprising 0.1% by mass or more and
1.8% by mass or less of Ni.
8. The low-lead brass alloy for use in a member for water works
according to claim 5, further comprising 0.1% by mass or more and
1.8% by mass or less of Ni.
Description
TECHNICAL FIELD
[0001] The present invention relates to a material made of a brass
alloy and having an erosion-corrosion resistance, designed for use
in a member for water works.
BACKGROUND ART
[0002] JIS H5120, CAC 203, a brass casting which has been
conventionally used for members related to water works, such as tap
faucet parts, contains from 0.5 to 3.0% by mass of lead, and it has
become difficult to comply with the lead regulations for copper
alloys for use in members for water works, implemented around the
world in recent years. Efforts have therefore been made to produce
a copper alloy with a reduced lead content, in order to reduce the
harmful effect of lead.
[0003] However, simply reducing the Pb content results in a
decrease in the castability, machinability and/or pressure
resistance of the copper alloy, which could potentially cause water
leak when used as a valve, for example. In order to compensate for
the changes in the properties of the alloy due to reduced content
of lead, incorporation of Bi has been proposed to improve
machinability, dezincification corrosion resistance and/or pressure
resistance.
[0004] For example, the below-identified Patent Document 1
discloses a brass alloy having a reduced risk of dezincification
corrosion and improved mechanical properties and castability, while
having a reduced lead content, which brass alloy containing, along
with Zn, from 0.4 to 3.2% by mass of Al, from 0.1 to 4.5% by mass
of Bi, and from 0.001 to 0.3% by mass of P.
[0005] Further, the below-identified Patent Document 2 discloses a
brass alloy (for example, No. 6 or No. 20) capable of preventing
water quality deterioration and having an excellent machinability
and abradability at the time of plating pretreatment, which brass
alloy containing from 0.3 to 1.0% of Sn, from 0.5 to 1.0% of Ni,
from 0.4 to 8% of Al, from 0.01 to 0.03% of P, from 1.0 to 2.0% of
Bi, and a trace amount of Sb. Patent Document 2 also discloses a
brass alloy further containing from 5 to 10 ppm by weight of B, in
addition to containing the above mentioned elements within the
above ranges.
[0006] However, a copper alloy which contains a large amount of Bi
for the purpose of securing the machinability must be separated
from other copper alloys containing no Bi, when subjected to
recycling. This is because, if a copper alloy containing Pb is
contaminated with Bi, for example, it causes embrittlement of the
resulting alloy. Since the alloy according to the Patent Document 1
contains Bi, it has the above mentioned problem, and the same
problem applies to the alloy according to Patent Document 2,
specifically, the alloy No. 6 disclosed as an Example therein.
[0007] In contrast, a brass alloy is also known which contains no
Bi, and which is useful as a member for water works in terms of
recyclability. For example, since the alloy No. 20 disclosed as a
Comparative Example in Patent Document 2 does not contain Bi, there
is no need to carry out the sorting of alloys based on whether or
not Bi is contained, at the time of recycling.
[0008] The below-identified Patent Document 3 discloses a copper
alloy (for example, No. 803) for use in wires, which does not
contain Bi or Pb, and contains from 62 to 91 mass % of Cu, from
0.01 to 4 mass % of Sn, from 0.0008 to 0.045 mass % of Zr, and from
0.01 to 0.25 mass % of P, with the balance being Zn. This copper
alloy is required to have a composition in which the contents of
Cu, Sn, and P, each in percent by mass, satisfy the relation:
62.ltoreq.Cu-0.5.times.Sn-3.times.P.ltoreq.90, in addition to
containing the above mentioned elements within the above contents.
Further, the copper alloy is also required to have a phase
structure in which the total content of .alpha.-phase,
.gamma.-phase, and .beta.-phase accounts for 95 to 100% in terms of
area ratio, and to have an average crystal grain size at the time
of melt-solidification of 0.2 mm or less. However, when this alloy
for use in wires is used as a member for water works, the alloy
fails to exhibit sufficient machinability, despite having a
sufficient recyclability due to containing no Bi.
[0009] In cases where a brass alloy is used as a member for water
works, there are other important issues to be addressed, in
addition to the recyclability. When used as a member for water
works, such as a valve, any brass alloy is susceptible to corrosion
induced by the rapid flow of water, referred to as an
erosion-corrosion. When a brass alloy is in contact with still
water, an oxide film is gradually formed on the surface of the
metallic material to prevent corrosion. However, in an environment
where the alloy is exposed to flowing water, the influence of the
shear force or turbulent flow caused by the flowing water, in
addition to ordinary corrosion, destroys the oxide film, thereby
accelerating the corrosion. The alloy No. 20 disclosed as a
Comparative Example in Patent Document 2 has an insufficient
erosion-corrosion resistance. Examples of the brass alloy having an
erosion-corrosion resistance, as described above, include alloys
disclosed in the below-identified Patent Documents 4 to 6.
[0010] Patent Document 4 discloses a copper alloy containing from
10 to less than 25 wt % of Zn, from 0.005 to 0.070 wt % of P, from
0.05 to 1.0 wt % of Sn, and from 0.05 to 1.0 wt % of Al; and any
one or two of from 0.005 to 1.0 wt % of Fe and from 0.005 to 0.3 wt
% of Pb in a total amount of from 0.005 to 1.3 wt %; with the
balance being copper and an unavoidable impurity(ies); wherein the
alloy has an excellent erosion-corrosion resistance.
[0011] Patent Document 5 discloses a copper alloy containing from
25 to 40 wt % of Zn, from 0.005 to 0.070 wt % of P, from 0.05 to
1.0 wt % of Sn, and from 0.05 to 1.0 wt % of Al, as essential
elements; and any one or two of from 0.005 to 1.0 wt % of Fe and
from 0.005 to 0.3 wt % of Pb in a total amount of from 0.005 to 1.3
wt %; with the balance being copper and an unavoidable
impurity(ies); wherein the alloy has a crystal grain size of 0.015
mm or less and an excellent dezincification corrosion
resistance.
[0012] Further, Patent Document 6 discloses a copper alloy
containing from 25 to 40 wt % of Zn, from 0.005 to 0.070 wt % of P,
from 0.05 to 1.0 wt % of Sn, from 0.05 to 1.0 wt % of Al, and from
0.005 to 1.0 wt % of Si, as essential elements; and any one or two
of from 0.005 to 1.0 wt % of Fe and from 0.005 to 0.3 wt % of Pb in
a total amount of from 0.005 to 1.3 wt %; with the balance being
copper and an unavoidable impurity(ies); wherein the alloy is
characterized by being subjected to cold rolling at reduction of
sectional area of 3 to 20%, after final annealing, and having an
excellent dezincification corrosion resistance.
[0013] In addition, the below-identified Patent Document 7
discloses copper alloys containing Zr and/or Te as a trace
element(s). Disclosed therein is a copper alloy containing from 8
to 40% of Zn, from 0.0005 to 0.04% of Zr, and from 0.01 to 0.25% of
P; and one or more than one of from 2 to 5% of Si, from 0.05 to 6%
by mass of Sn, and from 0.05 to 3.5% by mass of Al; with the
balance being Cu and an unavoidable impurity(ies). Also disclosed
therein, as Example 105, is a copper alloy which does not contain
Si or Bi, and contains 27% of Zn, 0.8% of Sn, 0.8% of Al, 0.05% of
P, 0.18% of Pb, 0.005% of Zr, and 0.12% of Te.
[0014] Moreover, the below-identified Patent Document 8 describes a
finding that it is possible to obtain an alloy satisfying required
physical properties by integrating the influence of each of the
elements in terms of zinc equivalent (Zneq), and allowing the zinc
equivalent Zneq to satisfy a certain Inequality. Note, however,
that the alloy in the above mentioned description contains Bi.
Specifically, the alloy contains: from 0.4 to 2.5% by mass of Al;
0.001 to 0.3% by mass of P; 0.1 to 4.5% by mass of Bi; from 0 to
5.5% by mass of Ni; from 0 to 0.5% by mass each of Mn, Fe, Pb, Sn,
Si, Mg, and Cd; and Zn; with the balance being Cu and an
unavoidable impurity(ies). Further, in the above mentioned alloy,
it is required that the Zneq and the content of Al satisfy the
following Inequalities (1) and (2):
Zneq+1.7.times.Al.gtoreq.35.0 (1)
Zneq-0.45.times.Al.ltoreq.37.0 (2).
PRIOR ART DOCUMENTS
Patent Documents
[0015] Patent Document 1: WO 2013/145964 A1
[0016] Patent Document 2: JP 2000-239765 A
[0017] Patent Document 3: JP 4094044 B
[0018] Patent Document 4: JP 60-138034 A
[0019] Patent Document 5: JP 61-199043 A
[0020] Patent Document 6: JP 62-30862 A
[0021] Patent Document 7: WO 2007/091690 A1
[0022] Patent Document 8: JP 5522582 B
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0023] However, since the alloy according to Patent Document 4 has
a low Zn content, its tensile strength is insufficient, thereby
causing problems in mechanical properties. In addition, although it
is alleged therein that the alloy has an erosion-corrosion
resistance, its Sri content is practically insufficient to provide
a sufficient erosion-corrosion resistance.
[0024] Further, since the alloys disclosed in Patent Documents 5
and 6 contain a large amount of Zn, they have problems that the
elongation tends to be insufficient, and that the dezincification
corrosion is likely to occur. The alloys also have an insufficient
erosion-corrosion resistance.
[0025] In addition, since the alloys disclosed in Patent Document 7
contain Zr and/or Te as an essential element(s), problems may occur
when used as a mixture with other copper alloys. In particular,
since Te is toxic, the use of this alloy as a member for water
works is not desirable in the first place.
[0026] Still further, since the alloy disclosed in Patent Document
8 contains Bi, it cannot be recycled along with other common copper
alloys containing Pb. This alloy also has a problem of insufficient
erosion-corrosion resistance.
[0027] Accordingly, an object of the present invention is to
provide a brass alloy, in which the contents of toxic elements are
reduced while maintaining the dezincification corrosion resistance
required for a member for water works; which is capable of
exhibiting an erosion-corrosion resistance while having a reduced
Bi content to secure a good recyclability; and which has excellent
mechanical properties to be used as a member for water works.
Means for Solving the Problems
[0028] The present invention has solved the above mentioned
problems by providing a low-lead brass alloy for use in a member
for water works, the brass alloy comprising: 24% by mass or more
and 34% by mass or less of Zn; 0.5% by mass or more and 1.7% by
mass or less of Sn; 0.4% by mass or more and 1.8% by mass or less
of Al; 0.005% by mass or more and 0.2% by mass or less of P; and
0.01% by mass or more and 0.25% by mass or less of Pb; with the
balance being copper and an unavoidable impurity(ies);
[0029] wherein, in cases where the brass alloy has a content of Sn
of less than 1.0% by mass, the contents of Al and Sn in % by mass
satisfy the following Inequality (3):
Al+2.times.Sn.gtoreq.2.8 (3).
[0030] Although the content of Pb is lower the better, Pb
contributes to improving the machinability of the alloy, even in a
small amount within the range in which its adverse effects on
health are limited. Further, Pb and Al--P compounds work in
combination to serve as chip breakers, and significantly contribute
to improving the machinability. This allows the alloy to have a
sufficient machinability, making it suitable for a member for water
works. Further, the incorporation of a specified amount of Sn
allows the alloy to exhibit mechanical properties required for a
brass alloy having a high content of Zn, such as tensile strength,
elongation, and 0.2% proof stress, while exhibiting durability
against erosion-corrosion.
[0031] In cases where the Sn content is less than 1.0% by mass, it
is necessary that the alloy meet a further requirement that the
relationship between the Sn content and the Al content satisfy the
above mentioned Inequality (3) in order to secure the
erosion-corrosion resistance. While both Al and Sn are involved in
the erosion-corrosion resistance, in cases where the Sn content is
less than 1.0% by mass, in particular, Sn has twice as much
influence on the improvement of the erosion-corrosion resistance as
Al does. Therefore, it is required that the above mentioned
Inequality (3) be satisfied, in order to obtain necessary physical
properties while securing a good balance of the erosion-corrosion
resistance and physical properties in the alloy. On the other hand,
when the Sn content is 1.0% by mass or more, a sufficient
erosion-corrosion resistance and the 0.2% proof stress can both be
secured, even if the above mentioned Inequality (3) is not
satisfied.
[0032] As with Pb, Si is also known as an element capable of
improving the machinability. However, the brass alloy according to
the present invention contains Si in an amount less than the amount
contained as an unavoidable impurity(ies).
[0033] This is because Si tends to produce an oxide which causes
problems in recyclability and mechanical properties, particularly,
in elongation. In addition, Si may potentially cause a reduction in
the erosion-corrosion resistance. When 0.015% by mass or less of B
is further incorporated into the brass alloy having the above
mentioned composition, as a variation of the brass alloy according
to the present invention, the dezincification corrosion resistance
is markedly improved.
[0034] Further, when 1.8% by mass or less of Ni is further
incorporated into the brass alloy having the above mentioned
composition, as another variation of the brass alloy according to
the present invention, the dezincification corrosion resistance is
markedly improved.
Effect of the Invention
[0035] The present invention allows for producing a member for
water works made of a brass alloy which has a good machinability
and erosion-corrosion resistance while having a reduced Bi content
to improve the recyclability, and in which safety, durability, and
convenience are ensured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a schematic diagram illustrating a tensile test
evaluation method.
[0037] FIG. 2 is a schematic diagram illustrating an
erosion-corrosion test apparatus.
[0038] FIG. 3 shows standards for evaluating machining chips
obtained in a machinability test.
[0039] FIG. 4 is a graph obtained by plotting the maximum
erosion-corrosion depth against the content of Sn, of alloys of
Examples.
[0040] FIG. 5 is a graph obtained by plotting the maximum
erosion-corrosion depth against the value T of Equation (4), of the
alloys of Examples.
[0041] FIG. 6 shows photographs of machining chips obtained in the
machinability test.
MODE FOR CARRYING OUT THE INVENTION
[0042] The present invention will now be described in detail.
[0043] The present invention relates to a brass alloy for use in a
member for water works which contains at least Zn, Sn, Al, P, and
Pb.
[0044] It is necessary that the above mentioned brass alloy contain
24% by mass or more of Zn. Preferably, the Zn content is 27% by
mass or more. A Zn content of less than 24% by mass results in an
insufficient tensile strength, thereby causing problems in
mechanical properties. When the Zn content is 27% by mass or more,
the resulting brass alloy has a sufficient 0.2% proof stress, and
thus has an excellent strength. At the same time, it is necessary
that the Zn content be 34% by mass or less. Preferably, the Zn
content is 32% by mass or less. Too high a Zn content tends to
result in an insufficient elongation. Further, a Zn content
exceeding 34% by mass leads to an excessive increase in the
dezincification corrosion.
[0045] It is necessary that the above mentioned brass alloy have a
Sn content of 0.5% by mass or more. If the Sn content is less than
0.5% by mass, the resulting alloy has an insufficient resistance to
erosion-corrosion. A Sn content of 1.0% by mass or more is
preferred, because the resulting alloy has a sufficient
erosion-corrosion resistance and a sufficient 0.2% proof stress. At
the same time, it is necessary that the Sn content be 1.7% by mass
or less. Preferably, the content is 1.3% by mass or less. This is
because too high a Sn content tends to results in too low an
elongation. Further, in cases where the Sn content is less than
1.0% by mass, it is necessary that the relationship between the Sn
content and the Al content satisfy Inequality (3) to be described
later, in order to secure the erosion-corrosion resistance.
[0046] It is necessary that the above mentioned brass alloy have an
Al content of 0.4% by mass or more. Preferably, the Al content is
0.6% by mass or more. An Al content of less than 0.4% by mass
results in an insufficient tensile strength and/or 0.2% proof
stress, thereby causing problems in mechanical properties. Further,
compounds formed between Al and P to be described later
significantly contribute to the improvement in the machinability.
However, if the Al content is deficient, the effect provided by the
compounds will also be insufficient. At the same time, it is
necessary that the Al content be 1.8% by mass or less. Preferably,
the content is 1.3% by mass or less. An Al content exceeding 1.8%
by mass may results in too low an elongation.
[0047] In cases where the Sn content is less than 1.0% by mass, it
is necessary that the relationship between the Sn content and the
Al content in the alloy satisfy the following Inequality (3). The
maximum depth of the cavities caused by erosion-corrosion tends to
decrease when either of the Al content and the Sn content is
increased. However, in cases where the Sn content is within the
range of less than 1.0% by mass, in particular, an increase in the
Sn content has twice as large an effect as an increase in the Al
content does in improving the erosion-corrosion resistance.
Al+2.times.Sn.gtoreq.2.8 (3)
[0048] It is necessary that the above mentioned brass alloy have a
P content of 0.005% by mass or more. Preferably, the P content is
0.01% by mass or more. Too low a P content reduces the effect of
improving the machinability provided by the Al--P compounds formed
between P and Al, and the resulting alloy tends to produce
continuous machining chips. Further, since P exhibits a deoxidizing
effect, too low a P content leads to a decrease in the deoxidizing
effect during casting, thereby resulting in an increased occurrence
of gas defects, as well as a decreased fluidity due to oxidation of
molten metal. At the same time, it is necessary that the P content
be 0.2% by mass or less. Preferably, the P content is 0.15% by mass
or less. Too high a P content leads to an increased formation of
hard Al--P compounds and the like, thereby resulting in a decrease
in the elongation. Further, P reacts with water in the mold to
increase the occurrence of gas defects and shrinkage cavity
defects.
[0049] It is necessary that the above mentioned brass alloy have a
Pb content of 0.01% by mass or more. Preferably, the Pb content is
0.03% by mass or more. The presence of Pb contributes to an
improved machinability of the alloy, along with the Al--P
compounds, but if the Pb content is less than 0.01% by mass, there
is a potential risk that the machinability may be insufficient.
Since the above mentioned brass alloy contains Sn, which leads to
the formation of hard .gamma.-phase, in particular, the effect of
improving the machinability provided by Pb is indispensable. On the
other hand, if the Pb content exceeds 0.25% by mass, it becomes
difficult to comply with the leaching standards for alloys for use
in members for water works, depending on the district in which it
is used. Accordingly, it is necessary that the Pb content be 0.25%
by mass or less, at maximum.
[0050] The above mentioned brass alloy may contain as the balance,
in addition to Cu, an element(s) other than those described above
as an unavoidable impurity(ies), which are inevitably included in
the alloy due to the problems associated with raw materials or the
production process. However, it is necessary that these elements be
contained within the ranges in which the effect of the present
invention is not impaired. This is because, when too large amounts
of unexpected elements are incorporated into the alloy, even if the
above mentioned elements are contained within the above mentioned
ranges, there is a potential risk that the physical properties of
the alloy may be deteriorated. The total content of the unavoidable
impurities is preferably less than 1.0% by mass, and more
preferably, less than 0.5% by mass.
[0051] Among the above mentioned unavoidable impurities, the
content of Si is preferably less than 0.2% by mass, more
preferably, less than 0.1% by mass, and still more preferably, less
than the detection limit. Too high a Si content accelerates the
entrainment of oxides, decrease in elongation, and occurrence of
shrinkage cavities, resulting in a failure to produce a decent
casting.
[0052] Among the above mentioned unavoidable impurities, it is
necessary that the content of Bi be less than 0.3% by mass. The Bi
content is preferably less than 0.1% by mass, and still more
preferably, less than the detection limit. This is because, if the
alloy contains an unignorable amount of Bi, the products made
therefrom must be recycled separately, thereby complicating the
recycling process. If the Bi content exceeds 0.3% by mass, the
coexistence of Bi in combination with Pb contained in the brass
alloy according to the present invention may cause an insufficient
elongation, and there is a potential risk that problems in
mechanical properties could occur.
[0053] The content of each of the elements which are considered as
the unavoidable impurities, is preferably less than OA % by mass,
more preferably, less than 0.2% by mass, and still more preferably,
less than the detection limit. Examples of such impurities include
Fe, Mn, Cr, Zr, Mg, Ti, Te, Se, Cd and the like. Among these, in
particular, the contents of Se, Cd, and Te, which are known to be
toxic, are each preferably less than 0.1% by mass, and more
preferably, less than the detection limit. Further, the content of
Zr, which increases the occurrence of shrinkage cavity defects, is
preferably less than 0.1% by mass, and still more preferably, less
than the detection limit.
[0054] On the other hand, when the above mentioned brass alloy
contains 0.0005% by mass or more of B as an intentionally included
element, apart from the above mentioned unavoidable impurities, the
dezincification corrosion resistance is significantly improved.
This is because the presence of B causes the crystal grains to be
refined and to be formed into shapes less susceptible to
dezincification corrosion. The content of B is preferably 0.0007%
by mass or more, because the dezincification corrosion resistance
is further improved. On the other hand, if the B content exceeds
0.015% by mass, a large amount of hard compounds is formed within
the texture of the alloy, potentially causing adverse effects on
machinability or elongation.
[0055] Further, the above mentioned brass alloy may contain Ni as
an intentionally included element, apart from the unavoidable
impurities. When the Ni content is 0.1% by mass or more, the
surface area of .alpha.-phase, which has an excellent corrosion
resistance, is increased, thereby improving the dezincification
corrosion resistance of the brass alloy. It is possible to adjust
the composition such that the alloy benefits from both the effect
provided by containing B, and the effect provided by containing Ni.
At the same time, the Ni content is preferably 1.8% by mass or
less, and more preferably, 0.5% by mass or less. The addition of an
excessive amount of Ni increases the amount of a phase having a
high Sn content, and the resulting alloy tends to have a reduced
elongation and/or machinability. A Ni content of greater than 1.8%
by mass results in an unignorable decrease in elongation. In order
to certainly prevent a decrease in elongation, the Ni content is
preferably 0.5% by mass or less.
[0056] Further, the above mentioned brass alloy may contain both B
and Ni as intentionally included elements, within the above
described ranges.
[0057] Note, however, that the values of the contents of elements
as used in the present invention indicate the contents thereof in
the resulting alloy produced by casting or forging, not the
contents in the raw materials.
[0058] The balance of the above mentioned brass alloy is Cu. The
brass alloy according to the present invention can be obtained by a
common method for producing a copper alloy, and when a member for
water works is produced using this brass alloy, a common production
method (such as casting, rolling, or forging) can be used. Examples
of the production method include a method in which an alloy is
melted using an oil furnace, gas furnace, high-frequency induction
melting furnace, or the like, and then cast using a mold in a
variety of shapes.
EXAMPLES
[0059] The brass alloy according to the present invention will now
be described with reference to Examples in which the brass alloys
were actually produced. First, test methods carried out for the
brass alloys will be described.
<Tensile Test Method>
[0060] A sample prepared by casting in a metal mold having a size
of 28 mm diameter.times.200 mm length was processed into a type 14A
test specimen defined in JIS Z2241. The specific shape of the test
specimen is as shown in FIG. 1. The test specimen is a proportional
test piece in which the original sectional area S.sub.0 and the
original gauge length L.sub.0 of the parallel portion satisfy the
relationship represented by the equation:
L.sub.0=5.65.times.S.sub.0 (1/2). The diameter d.sub.0 of the
rod-like portion was 4 mm, the original gauge length L.sub.0 was 20
mm, the length L.sub.c of the parallel portion which was
cylindrical was 30 mm, and the radius R of the shoulder portions
was 15 mm. (L.sub.0=5.65.times.(2.times.2.times..pi.)
(1/2)=20.04)
[0061] The test specimen was subjected to a tensile test according
to JIS Z2241 and the tensile strength (MPa), the 0.2% proof stress
(MPa) and the elongation (%) were evaluated as follows. The tensile
strength was defined as the maximum test force Fm, which was the
force the test specimen withstood during the test until it
exhibited discontinuous yielding. The 0.2% proof stress is the
value of the stress when the plastic elongation expressed in
percentage relative to the original gauge length L.sub.0 equals to
0.2%. The elongation is the value of the permanent elongation of
the test specimen after the test, obtained by continuing the test
until it ruptures, expressed in percentage relative to the original
gauge length L.sub.o. [0062] The tensile strength was evaluated
according to the following standards: "Good" (G): 300 MPa or more;
"Fair" (F): 250 MPa or more and less than 300 MPa, and
"Insufficient" (I): less than 250 MPa. [0063] The 0.2% proof stress
was evaluated according to the following standards: "Good" (G): 100
MPa or more, "Fair" (F): 80 MPa or more and less than 100 MPa, and
"Insufficient" (I): less than 80 MPa. [0064] The elongation was
evaluated according to the following standards: "Good" (G): 25% or
more, "Fair" (F): 20% or more and less than 25%, and "Insufficient"
(I): less than 20%.
<Erosion-Corrosion Test>
[0065] A sample prepared by casting in a metal mold having a size
of 20 mm diameter.times.120 mm length was cut into a cylinder
having a diameter of 16 mm as shown in FIG. 2, to be used as a test
specimen 12. A nozzle 11 having a bore diameter of 1.6 mm was
disposed at a position 0.4 mm spaced apart from the test specimen
12, and a 1% aqueous solution of CuCl.sub.2 13 was allowed to
continuously flow from the nozzle 11 toward the sample at a flow
rate of 0.4 L/min for 5 hours. Then the amount of the weight lost
(abrasion weight loss), which is the difference in weight of the
sample before and after the test, and the maximum erosion-corrosion
depth in the sample were measured. [0066] The abrasion weight loss
was evaluated according to the following standards: "Good" (G):
less than 250 mg, "Fair" (F): 250 mg or more and less than 350 mg,
and "Insufficient" (I): 350 mg or more. [0067] The maximum
erosion-corrosion depth was evaluated according to the following
standards: "Good" (G): 150 .mu.m or less, "Fair" (F): 150 .mu.m or
more and 200 .mu.m or less, and "Insufficient" (1): 200 .mu.m or
more.
<Drilling Test>
[0068] Each of the alloys was subjected to a drilling test using a
drilling machine. The drilling test was carried out using the
samples each formed by machining to a size of 18 mm
diameter.times.20 mm height, and using a drilling machine, under
the drilling conditions shown in Table 1. The evaluation was
carried out as follows. The time required to drill a 5 mm hole in
each of the samples was measured, and those with the results of 20
seconds or less were evaluated as "Good" (G), those with the
results of more than 20 seconds and 25 seconds or less were
evaluated as "Fair" (F), those with the results of more than 25
seconds were evaluated as "Insufficient" (I).
TABLE-US-00001 TABLE 1 Items Conditions Cutting tool Material
High-speed steel (SDD0600; manufactured by Cutting Diameter: 6 mm
Mitsubishi Corporation) diameter Total 102 mm length Flute 70 mm
length Point angle 118 degree Load 25 kg Rotational speed 960 rpm
Drilling depth 5 mm
<Lathe Machining Test>
[0069] For each of the alloys to be tested, a sample prepared by
casting in a metal mold having a size of 28 mm diameter.times.200
mm length was subjected to dry machining on a universal lathe, with
a cemented carbides and/or hard metals brazed tool, at a feed of
0.15 mm/rev and a rotational speed 550 of rpm, to obtain machining
chips. The machining chips were categorized based on their shapes
as shown in FIG. 3. The evaluation was carried out as follows:
those having favorable shapes were evaluated as "Good" (G), and
those having unfavorable shapes were evaluated as "Insufficient"
(I).
<Dezincification Corrosion Test Method>
[0070] A sample prepared by casting in a metal mold having a size
of 28 mm diameter.times.200 mm length was cut out into a cubic test
specimen of 10 mm.times.10 mm.times.10 mm, and the test was
performed according to ISO 6509. Specifically, the surroundings of
the test specimen was covered with an epoxy resin having a
thickness of 15 mm or more such that only one surface of the test
specimen was exposed from the resin. After 100 mm.sup.2 of this
exposed surface was polished with wet abrasive paper, the exposed
surface was finished with No. 1200 abrasive paper, and washed with
ethanol immediately before the test. This sample embedded in the
epoxy resin with only one surface exposed was immersed in 250 mL of
a 12.7 g/L aqueous solution of cupric chloride at 75.+-.5.degree.
C. for 24 hours. After the completion of the test, the sample was
washed with water, rinsed with ethanol, and the dezincification
depth in its cross section was immediately measured using a light
microscope. Specifically, an arbitrary line of 10 mm on
cross-section of the exposed surface was divided into 5 visual
fields and the dezincification depths of the points having the
minimum and the maximum depths in each of the visual fields were
measured. The mean value of the total 10 points was taken as the
average dezincification corrosion depth, and the depth of the
deepest point of all these 10 points was taken as the maximum
dezincification corrosion depth. The average and maximum
dezincification corrosion depths were evaluated as follows, and
those having evaluations other than "insufficient" for both the
dezincification depths were defined as "pass". [0071] The average
dezincification corrosion depth was evaluated according to the
following standards: "Very Good" (V): less than 50 .mu.m, "Good"
(G): 50 .mu.m or more and less than 100 .mu.m, "Fair" (F): 100
.mu.m or more and less than 200 .mu.m, and "Insufficient" (1): 200
.mu.m or more. [0072] The maximum dezincification corrosion depth
was evaluated according to the following standards: "Very Good"
(V): less than 100 .mu.m, "Good" (G): 100 .mu.m or more and less
than 200 .mu.m, "Fair" (F): 200 .mu.m or more and less than 400
.mu.m, and "Insufficient" (I): 400 .mu.m or more.
<Sample Production Method>
[0073] Materials composed of each of the elements were mixed, and
melted in a high frequency induction melting furnace, followed by
casting to produce samples each having the composition as shown in
each of the Tables. All the values of the contents of the elements
are expressed in % by mass, and are values measured in the
resulting castings after the production. The following tests were
carried out for each of the resulting copper alloys. Note that, the
content of each of Sb, Si, and Fe was less than the detection
limit, in each of the alloys of Examples and Comparative Examples
shown in the Tables. Elements which are not shown in the Tables, or
the blanks therein, indicate that the contents of the respective
elements are less than the detection limit.
[0074] First, each of the Sn content and the Al content were varied
to examine the test results of the alloy in relation to the
Inequality (3). The components used in the evaluation, and the
results of the mechanical properties test and erosion-corrosion
(EC) test are shown in Table 2. FIG. 4 shows line graphs obtained
by plotting the data of the above obtained results, categorized in
3 groups based on the concentration of Al, with the values the
maximum erosion-corrosion depth on the vertical axis against the
values of the Sn content on the horizontal axis. In Table 2, Test
Examples 1 to 4 are alloys having an Al content of 0.6% by mass,
Test Examples 5 to 8 are alloys having an Al content of 1.0% by
mass, and Test Examples 9 to 12 are alloys having an Al content of
1.7% by mass. Test Examples are arranged in the order based on the
content of Sn, in increasing order from top to bottom, within each
of the groups based on the Al concentration.
TABLE-US-00002 TABLE 2 Mechanical properties EC 0.2% Abrasion
Tensile Elonga- proof weight Maximum Experiment Chemical components
(% by mass) strength tion stress loss depth No. Zn Al P Pb Sn Cu
(MPa) (%) (MPa) (mg) (.mu.m) Test Example 1 28.62 0.61 0.061 0.073
0.72 Bal 303.9 G 30.4 G 105.5 G 266 F 257 I Test Example 2 28.60
0.61 0.060 0.081 0.90 Bal 307.1 G 28.9 G 107.7 G 255 F 211 I Test
Example 3 28.32 0.61 0.058 0.075 1.02 Bal 301.6 G 28.3 G 114.6 G
216 G 143 G Test Example 4 28.77 0.61 0.065 0.065 1.23 Bal 346.5 G
25.2 G 131.1 G 218 G 104 G Test Example 5 28.52 1.02 0.061 0.070
0.71 Bal 340.1 G 28.1 G 124.3 G 261 F 214 I Test Example 6 28.54
1.01 0.062 0.065 0.91 Bal 350.1 G 28.2 G 129.8 G 216 G 173 F Test
Example 7 28.51 1.02 0.062 0.072 1.03 Bal 350.9 G 26.3 G 134.2 G
195 G 134 G Test Example 8 28.34 1.02 0.062 0.066 1.21 Bal 381.7 G
24.2 F 145.5 G 192 G 108 G Test Example 9 27.81 1.68 0.061 0.068
0.72 Bal 305.2 G 25.7 G 130.6 G 216 G 171 F Test Example 27.96 1.70
0.065 0.074 0.90 Bal 328.4 G 26.8 G 135.8 G 214 G 163 F 10 Test
Example 28.01 1.69 0.062 0.065 1.02 Bal 343.2 G 24.5 F 142.3 G 173
G 130 G 11 Test Example 27.97 1.69 0.061 0.070 1.21 Bal 389.1 G
21.9 F 143.7 G 172 G 112 G 12
[0075] The test results revealed that the erosion-corrosion (EC)
maximum depth was markedly reduced in the alloys of Test Examples
having a Sn content within the range of 1.0% by mass or more, as
compared to the alloys of the Test Examples having a Sn content
within the range of less than 1.0% by mass, regardless of the Al
content. Further, the results also indicated that, when the Sn
content is the same, the higher the Al content is, the more reduced
the maximum erosion-corrosion depth is. However, the above
mentioned tendency was markedly observed, particularly in cases
where the Sn content is within the range of less than 1.0% by
mass.
[0076] Therefore, among the alloys of Test Examples, those having a
Sn content of less than 1.0% by mass were examined. Specifically,
the alloys of Test Examples 1 and 2 having an Al content of 0.6% by
mass, Test Examples 5 and 6 having an Al content of 1.0% by mass,
and Test Examples 9 and 10 having an Al content of 1.7% by mass
were selected, which are shown in Table 3. Of these, the alloys of
Test Examples 1, 2, and 5 were evaluated as having an
"Insufficient" in the maximum erosion-corrosion depth. The Sn
content in the alloy of Test Example 2 is about 0.2% by mass higher
than that of Test Example 1. Further, the Al content in the alloy
of Test Example 5 is about 0.4% by mass higher than that of Test
Example 1. The values of the maximum erosion-corrosion depth of
Test Example 2 and Test Example 5 are almost the same. In other
words, the alloy of Test Example 2 with a Sn content 0.2% higher
than that of Test Example 1, and the alloy of Test Example 5 with
an Al content 0.4% higher than that of Test Example 1, have the
same level of reduction in the maximum erosion-corrosion depth
relative to the alloy of Test Example 1. Consequently, it is
assumed that, in the improvement in the erosion-corrosion
resistance, which is observed as the reduction in the maximum
erosion-corrosion depth associated with an increase in the Sn or Al
content, an increase in the Sn content has twice as large an effect
as an increase in the Al content does, when the Sn content is
within the range of less than 1.0% by mass. Thus, the value T
represented by the following Equation (4) can be used as an index
for the erosion-corrosion resistance.
TABLE-US-00003 TABLE 3 EC Abrasion weight Maximum Experiment
Chemical components (% by mass) loss depth No. Zn Al P Pb Sn Cu
(mg) (.mu.m) Equation (4): T Test Example 1 28.62 0.61 0.061 0.073
0.72 Bal 266 F 257 I 2.05 Test Example 2 28.60 0.61 0.060 0.081
0.90 Bal 255 F 211 I 2.41 Test Example 5 28.52 1.02 0.061 0.070
0.71 Bal 261 F 214 I 2.44 Test Example 6 28.54 1.01 0.062 0.065
0.91 Bal 216 G 173 F 2.83 Test Example 9 27.81 1.68 0.061 0.068
0.72 Bal 216 G 171 F 3.12 Test Example 27.96 1.70 0.065 0.074 0.90
Bal 214 G 163 F 3.50 10
T=Al+2.times.Sn (4)
[0077] FIG. 5 shows a graph obtained by plotting the data shown in
Table 2, with the values of the maximum erosion-corrosion depth on
the vertical axis against the values of Equation (4) on the
horizontal axis. The result revealed that, when the value T of
Equation (4) is within the range of less than 2.8, the value of the
maximum erosion-corrosion depth tends to decrease in an
approximately linear manner, as the value T of Equation (4)
increases. Further, when the value T of Equation (4) is within the
range of 2.8 or more, the value of the maximum erosion-corrosion
depth tends to remain approximately the same. Based on the above,
it was confirmed that in cases where the alloy has a Sn content of
less than 1.0% by mass, it is possible to secure a sufficient
erosion-corrosion resistance by allowing the Sn content and the Al
content to satisfy the above described Inequality (3).
[0078] In the above mentioned Test Examples, the alloys of Test
Examples 3, 4, and 6 to 12 correspond to the alloys of Examples
according to the present invention. Of these, the alloys of Test
Examples 6, 9, and 10 have a Sn content of less than 1.0% by mass,
and meet the requirement to satisfy the above mentioned Inequality
T.gtoreq.2.8, and thus correspond to the alloys of Examples
according to the present invention. On the other hand, the alloys
of Test Examples 3, 4, 7, 8, 11, and 12 meet the requirement to
have a Sn content of 1.0% by mass or more, and thus correspond to
the alloys of Examples according to the present invention.
[0079] Next, the changes in the mechanical properties and the
erosion-corrosion resistance when the contents of Zn, Al, P, Sn and
Pb were varied were evaluated by the tensile test and the
erosion-corrosion test. The contents of the respective components
and the test results of the respective alloys are shown in Table
4.
TABLE-US-00004 TABLE 4 Mechanical properties EC Tensile Abrasion
Chemical components strength Elongation 0.2% proof weight Maximum
Zn Al P Pb Sn Bi Cu (MPa) (%) stress (MPa) loss (mg) depth (.mu.m)
Total Zn Comparative Example 1 21.00 1.00 0.059 0.073 1.27 0.000
Bal. 220.5 I 23.4 F 84.0 F 212 G 141 G I Example 1 24.54 1.02 0.057
0.063 1.19 0.000 Bal. 257.0 F 30.0 G 89.5 F 201 G 132 G F Example 2
27.50 1.03 0.058 0.053 1.21 0.000 Bal. 385.0 G 25.1 G 125.0 G 198 G
120 G G Example 3 30.17 1.06 0.057 0.063 1.21 0.000 Bal. 392.0 G
26.9 G 147.5 G 188 G 128 G G Comparative Example 2 34.87 1.00 0.058
0.057 1.18 0.000 Bal. 401.0 G 19.1 I 175.5 G 210 G 138 G I Al
Comparative Example 3 30.69 0.00 0.059 0.065 1.09 0.000 Bal. 221.0
I 35.2 G 77.2 I 254 F 121 G I Example 4 30.83 0.39 0.060 0.074 1.13
0.000 Bal. 290.5 F 33.4 G 94.5 F 222 G 136 G F Example 5 30.25 0.65
0.058 0.064 1.17 0.000 Bal. 366.4 G 29.9 G 125.5 G 202 G 138 G G
Example 3 30.17 1.06 0.057 0.063 1.21 0.000 Bal. 392.0 G 26.9 G
147.5 G 188 G 128 G G Example 6 29.75 1.66 0.056 0.626 1.18 0.000
Bal. 399.0 G 21.2 F 158.5 G 182 G 141 G F Comparative Example 4
29.66 2.12 0.059 0.054 1.14 0.000 Bal. 410.0 G 16.1 I 179.0 G 172 G
190 F I P Example 7 29.93 1.00 0.036 0.054 1.14 0.000 Bal. 345.5 G
29.3 G 125.5 G 228 G 123 G G Example 3 30.17 1.06 0.057 0.063 1.21
0.000 Bal. 392.0 G 26.9 G 147.5 G 188 G 118 G G Example 8 29.79
1.02 0.121 0.070 1.12 0.000 Bal. 381.0 G 27.0 G 151.5 G 252 F 168 F
F Comparative Example 5 29.50 1.02 0.235 0.060 1.16 0.000 Bal.
361.0 G 19.6 I 151.5 G 287 F 188 F I Sn Comparative Example 6 29.28
1.01 0.059 0.060 0.11 0.000 Bal. 294.5 F 51.4 G 96.0 F 389 I 497 I
I Comparative Example 7 29.69 1.03 0.060 0.064 0.31 0.000 Bal.
302.0 G 45.0 G 101.5 G 278 F 288 I I Example 9 30.10 1.00 0.055
0.066 0.91 0.000 Bal. 388.0 G 34.5 G 138.2 G 206 G 162 F F Example
3 30.17 1.06 0.057 0.063 1.21 0.000 Bal. 392.0 G 26.9 G 147.5 G 178
G 128 G G Example 10 29.70 0.99 0.061 0.064 1.54 0.000 Bal. 382.5 G
22.4 F 144.8 G 188 G 108 G F Comparative Example 8 30.05 1.01 0.062
0.062 1.75 0.000 Bal. 349.5 G 18.3 I 139.5 G 177 G 114 G I
Comparative Example 9 29.64 1.00 0.061 0.063 2.19 0.000 Bal. 390.5
G 9.4 I 182.5 G 174 G 116 G I Pb Example 11 29.40 1.04 0.056 0.025
1.05 0.000 Bal. 323.0 G 29.4 G 110.5 G 188 G 122 G G Example 3
30.17 1.06 0.057 0.063 1.21 0.000 Bal. 392.0 G 26.9 G 147.5 G 178 G
118 G G Example 12 30.11 1.02 0.055 0.233 1.19 0.000 Bal. 358.0 G
23.3 F 148.2 G 174 G 120 G F
[0080] Firstly, alloys with varying Zn content were prepared. The
alloy of Comparative Example 1 having a Zn content of less than 24%
by mass has a problem in tensile strength. The alloy of Example 1
having a Zn content of 24% by mass or more has a certain level of
tensile strength, and the alloys of Examples 2 and 3 having a Zn
content of 27% by mass or more have a sufficient tensile strength.
On the other hand, the alloy of Comparative Example 2 having a Zn
content of greater than 34% by mass, which is too high, has a
problem in elongation.
[0081] Secondly, alloys with varying Al content were prepared. In
the alloy of Comparative Example 3 having an Al content of less
than the detection limit, both the tensile strength and the 0.2%
proof stress were insufficient. The alloy of Example 4 having an Al
content of 0.39% by mass has a certain level of tensile strength
and 0.2% proof stress, and the alloys of Example 5, 3, and 6 having
an Al content of 0.6% by mass or more have a sufficient tensile
strength and 0.2% proof stress. On the other hand, the alloy of
Comparative Example 4 having an Al content of greater than 1.8% by
mass, which is too high, has a problem in elongation, while the
alloy of Example 6 having an Al content of less than 1.66% by mass,
which is less than 1.8% by mass, has a certain level of
elongation.
[0082] Thirdly, alloys with varying P content were prepared. In the
alloy of Example 8 having a slightly higher P content, the
erosion-corrosion resistance was slightly reduced. Further, the
alloy of Comparative Example 5 having a high P content of greater
than 0.2% by mass has too low an elongation.
[0083] Fourthly, alloys with varying Sn content were prepared. In
the alloy of Comparative Example 6 having a Sn content of 0.11% by
mass and the alloy of Comparative Example 7 having a Sn content of
0.31% by mass, the erosion-corrosion resistance was insufficient,
and both the values of the abrasion weight loss and the maximum
depth were unfavorable. The alloy of Example 9, which has a Sn
content of 0.91% by mass and in which the Sn content and the Al
content satisfy the equation: T=Al+2.times.Sn=2.82, has a certain
level of erosion-corrosion resistance. Further, the alloys of
Examples 3 and 10 having a Sn content of 1.0% by mass or more have
a sufficient erosion-corrosion resistance. On the other hand, the
alloys of Comparative Examples 8 and 9 having a Sn content of
greater than 1.7% by mass have too low an elongation. The alloy of
Example 10 having a Sn content of 1.54% by mass has a certain level
of elongation.
[0084] Fifthly, alloys with varying Pb content were prepared. All
of the alloys of Examples 11, 3, and 12 having a Pb content as
shown in Table 4 exhibited good mechanical properties and the
erosion-corrosion resistance. However, in the alloy of Example 12
whose Pb content is close to 0.25% by mass, a slight decrease in
elongation was observed.
<Evaluation of Machinability in Relation with P and Pb
Content>
[0085] Next, alloys with varying P and Pb contents were prepared,
and subjected to the drilling test and the lathe machining test to
evaluate the changes in the machinability. The contents of the
respective components and the test results of the respective alloys
are shown in Table 5.
TABLE-US-00005 TABLE 5 Machinability test Chemical components
Drilling time Machining Zn Al P Pb Sn Bi Cu sec chips P Comparative
29.54 1.01 0.000 0.071 1.17 0.000 Bal. 28.7 I I Example 10
(Continuous) Example 13 29.70 1.00 0.009 0.074 1.20 0.000 Bal. 13.4
G G (Broken) Example 7 29.93 1.00 0.036 0.054 1.14 0.000 Bal. 19.9
G G (Broken) Example 3 30.17 1.06 0.057 0.063 1.21 0.000 Bal. 17.0
G G (Broken) Example 8 29.79 1.02 0.121 0.070 1.12 0.000 Bal. 21.9
F G (Broken) Comparative 29.50 1.02 0.235 0.060 1.16 0.000 Bal.
23.7 F G (Broken) Example 5 Pb Comparative 28.72 0.98 0.060 0.000
1.04 0.000 Bal. 42.4 I G (Broken) Example 11 Example 11 29.40 1.04
0.056 0.025 1.05 0.000 Bal. 21.4 F G (Broken) Example 3 30.17 1.06
0.057 0.063 1.21 0.000 Bal. 17.0 G G (Broken) Example 12 30.11 1.02
0.055 0.233 1.19 0.000 Bal. 12.0 G G (Broken) Pb and P Comparative
30.05 1.10 0.000 0.000 1.05 0.000 Bal. 47.3 I I Example 12
[0086] Firstly, the changes due to varying P content are examined.
The alloy of Comparative Example 10 having a P content of 0.009% by
mass and the alloy of Example 13 having a P content of less than
the detection limit were prepared. The thus prepared alloys and the
alloys of the above mentioned Examples 7, 3, and 8, and Comparative
Example 5 were subjected to the drilling test. In the alloy of
Comparative Example 10 having a P content of less than the
detection limit, it took too long to drill a hole, and continuous
machining chips were produced. In the alloys of Example 13, 7, and
3 having a P content of 0.005% by mass or more, it was possible to
drill a hole in a sufficiently short period of time. Further, in
the alloys of Examples 13 and 3, the resulting machining chips were
broken into pieces. This is thought to be due to the Al--P
compounds, formed as a result of containing P, serving as chip
breakers during the machining. On the other hand, in each of the
alloys of Example 8 and Comparative Example 5 having a P content of
greater than 0.1% by mass, the time required to drill a hole was
slightly increased to a level which cannot be disregarded.
[0087] In addition, the machining chips of the alloys of
Comparative Example 10, Example 13, and Example 3 were evaluated
based on their shapes. The photographs of the machining chips of
the alloys of Comparative Example 10, Example 13, and Example 3 are
shown in FIGS. 6 (a), (b), and (c), respectively. The alloy of
Comparative Example 10 produced helically-coiled, continuous
machining chips which are unfavorable; whereas the alloy of Example
13 having a higher P content produced generally shorter machining
chips, and the alloy of Example 3 having an even higher P content
produced even shorter machining chips, both of which are
favorable.
[0088] Next, the changes due to varying Pb content are examined.
The alloy of Comparative Example 11 having a Pb content of less
than the detection limit was newly prepared. The thus prepared
alloy and the alloys of the above mentioned Examples 11, 3, and 12
were subjected to the drilling test. In the alloys of Comparative
Example 11 having a Pb content of less than the stipulated value,
the drilling time was significantly increased. In the alloys of
Example 11 having a Pb content of 0.025% by mass, the drilling time
was relatively reduced, and a certain level of the machinability
was secured. In each of the alloys of Examples 3 and 12 having an
even higher Pb content, the drilling time was reduced to a
sufficiently short time. Further, the machining chips of the alloys
of Comparative Example 11 and Example 11 were evaluated based on
their shapes. The photographs of the machining chips of the alloys
of Comparative Example 11 and Example 11 are shown in FIGS. 6 (d)
and (e), respectively. The machining chips produced by respective
alloys had no problems.
[0089] Further, as an example containing neither P nor Pb, the
alloy of Comparative Example 12 was prepared. The alloy of
Comparative Example 12 was subjected to the evaluation of machining
chips and the drilling test. The photograph of the machining chips
of the alloy of Comparative Example 12 is shown in FIG. 6 (f). The
results revealed that, the alloy of Comparative Example 12
containing neither P nor Pb produced unfavorable continuous
machining chips which were even longer than those produced by the
alloy of Comparative Example 10 containing Pb but not P. In the
drilling test, as well, the alloy of Comparative Example 12
exhibited a drilling time which was even significantly longer than
that of Comparative Example 10.
[0090] Other results will be examined individually with reference
to Examples and Comparative Examples. The data thereof are shown in
Table 6.
TABLE-US-00006 TABLE 6 Mechanical properties Chemical component
Tensile strength Zn Al P Pb Sn Bi Cu Ni B (MPa) Zn Example 2 27.50
1.03 0.058 0.053 1.21 0.000 Bal. 385.0 G Example 3 30.17 1.06 0.057
0.063 1.21 0.000 Bal. 392.0 G Comparative 34.87 1.00 0.058 0.057
1.18 0.000 Bal. 401.0 G Example 2 Bi Example 3 30.17 1.06 0.057
0.063 1.21 0.000 Bal. 392.0 G Comparative 29.88 1.08 0.062 0.077
1.17 0.350 Bal. 348.5 G Example 13 Ni-1 Example 3 30.17 1.06 0.057
0.063 1.21 0.000 Bal. 392.0 G Example 14 30.10 1.11 0.059 0.083
1.12 0.000 Bal. 0.82 351.5 G Comparative 30.20 1.06 0.055 0.067
1.18 0.000 Bal. 1.88 362.5 G Example 14 Ni-2 Example 15 29.20 1.10
0.052 0.091 1.05 0.000 Bal. 0.52 377.0 G Example 16 30.20 1.06
0.048 0.088 1.08 0.000 Bal. 1.03 366.5 G B-1 Example 3 30.17 1.06
0.057 0.063 1.21 0.000 Bal. 392.0 G Example 17 30.10 1.11 0.059
0.083 1.12 0.000 Bal. 0.0060 392.0 G B-2 Example 18 30.17 1.05
0.056 0.100 1.10 0.000 Bal. 0.0007 388.0 G Example 19 29.70 1.05
0.055 0.075 1.12 0.000 Bal. 0.0012 390.0 G Example 20 30.10 1.10
0.055 0.097 1.06 0.000 Bal. 0.0110 385.5 G B + Ni Example 21 30.20
1.06 0.055 0.067 1.18 0.000 Bal. 0.81 0.0050 366.0 G Example 22
29.20 1.05 0.055 0.088 1.11 0.000 Bal. 0.49 0.0041 382.0 G Example
23 29.40 1.11 0.047 0.072 1.08 0.000 Bal. 1.04 0.0053 388.5 G
Dezincification corrosion EC Mechanical properties test Abrasion
Maximum Elongation 0.2% proof Maximum Average weight depth (%)
stress (MPa) depth (.mu.m) depth (.mu.m) loss (mg) (.mu.m) Zn
Example 2 25.1 G 125.0 G 104.7 G 47.1 V Example 3 26.9 G 147.5 G
133.8 G 67.7 G Comparative 19.1 I 175.5 G 396.9 F 207.5 I Example 2
Bi Example 3 26.9 G 147.5 G 133.8 G 67.7 G Comparative 18.2 I 154.0
G 122.3 G 65.4 G Example 13 Ni-1 Example 3 26.9 G 147.5 G 133.8 G
67.7 G Example 14 21.2 F 137.5 G 116.5 G 48.1 V Comparative 19.7 I
149.0 G 96.5 V 44.1 V Example 14 Ni-2 Example 15 25.5 G 141.5 G
122.2 G 49.4 V 175 G 124 G Example 16 22.4 F 140.2 G 105.2 G 45.2 V
168 G 119 G B-1 Example 3 26.9 G 155.0 G 133.8 G 67.7 G Example 17
27.3 G 155.0 G 79.2 V 41.7 V B-2 Example 18 27.5 G 153.0 G 103.8 G
49.8 V 184 G 129 G Example 19 25.5 G 151.5 G 95.3 V 44.2 V 182 G
125 G Example 20 24.8 F 152.5 G 70.4 V 38.9 V 179 G 131 G B + Ni
Example 21 22.5 F 152.0 G 65.7 V 39.8 V G G Example 22 23.5 F 153.5
G 70.5 V 40.5 V 171 G 129 G Example 23 21.0 F 153.0 G 63.5 V 32.2 V
166 G 121 G
<Results of Dezincification Corrosion Test>
[0091] The alloys of Example 2, Example 3, and Comparative Example
2 were used to examine the changes in the dezincification corrosion
depth due to varying Zn content. The alloy of Example 2 having a
sufficiently low Zn content exhibited a markedly reduced
dezincification corrosion depth. The alloy of Example 3 also had a
low level of corrosion. In contrast, in the alloy of Comparative
Example 2 having a Zn content of greater than 34% by mass, the
value of the maximum depth was close to the acceptable limit, and
the average depth was significantly increased.
<Examination of Alloy Behavior Due to Addition of Bi>
[0092] The alloy of Comparative Example 13 having a composition
close to that of Example 3 and containing 0.35% by mass of Bi was
prepared and examined. The results confirmed that the alloy has a
significantly reduced elongation, and thus has problems not only in
recyclability but also in mechanical properties.
<Examination of Alloy Behavior Due to Addition of Ni: No.
1>
[0093] The alloy of Example 14 having a composition close to that
of Example 3 and further containing 0.82% by mass of Ni, and the
alloy of Comparative Example 14 having a composition close to that
of Example 3 and further containing 1.88% by mass of Ni were
prepared. While the dezincification corrosion resistance was
significantly improved in both the alloys of Example 14 and
Comparative Example 14, the elongation was excessively decreased in
the alloy of Comparative Example 14 having a Ni content of 1.88% by
mass.
<Examination of Alloy Behavior Due to Addition of Ni: No.
2>
[0094] The alloys of Examples 15 and 16 each having a lower Sn
content and a higher Pb content as compared to that of Example 14
were prepared. In the alloy of Example 16 having a higher Ni
content as compared to that of Example 15, the dezincification
corrosion resistance was more improved. Further, the measurement of
the erosion-corrosion resistance of the alloys of Examples 15 and
16 revealed that the both alloys have a good erosion-corrosion
resistance. However, it was also shown that while the alloy of
Example 16 has a certain level of elongation, but it is slightly
decreased as compared to that of Examples 15.
<Examination of Alloy Behavior Due to Addition of B: No.
1>
[0095] The alloy of Example 17 having a composition close to that
of Example 3 and further containing 0.006% by mass of B was
prepared. In each of the alloys of Example 3 and Example 17, a
marked improvement in the dezincification corrosion resistance was
observed.
<Examination of Alloy Behavior Due to Addition of B: No.
2>
[0096] The alloys of Examples 18 to 20 having a composition close
to that of Example 3 and further containing increasing amounts of B
were prepared. The alloy of Example 18 has a B content of 0.0007%
by mass, the alloy of Example 19 has B content of 0.0012% by mass,
and the alloy of Example 20 has a B content of 0.011% by mass. The
dezincification corrosion resistance was significantly improved
with increasing B content, and thus the dezincification corrosion
resistance of the alloy of Example 20 was particularly improved. It
was also shown, however, that while the alloy of Example 20 has a
certain level of elongation, it is somewhat decreased as compared
to those of Examples 18 and 19.
<Examination of Alloy Behavior Due to Addition of B and
Ni>
[0097] The alloys of Examples 21 to 23 having a composition close
to that of Example 3 and further containing both B and Ni were
prepared. All the alloys exhibited a particularly excellent
dezincification corrosion resistance. However, it was also shown
that each of the alloys has a certain level of, but somewhat lower
elongation.
DESCRIPTION OF SYMBOLS
[0098] 11 nozzle [0099] 12 test specimen [0100] 13 aqueous solution
of CuCl.sub.2
* * * * *