Note: Descriptions are shown in the official language in which they were submitted.
CA 02718613 2010-10-20
DEZINCIFICATION RESISTANT BRASS ALLOY
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to dezincification resistant copper alloys, and
more particularly, to a dezincification resistant brass alloy.
Description of Related Art
Brass alloy includes copper and zinc as major ingredients usually at a
ratio of about 7:3 or 6:4. Dezincification corrosion is a selective corrosion
of
brass alloys. When a copper-zinc alloy is in an aqueous solution (such as sea
water or fresh water), some corrosion occurs on a surface of the alloy, and
zinc on the surface of the alloy is dissolved. However, copper residue still
remains on the surface of the alloys, resulting in red porous sponge-like
copper, i.e. dezincification corrosion phenomenon.
Generally, if the zinc content is less than 15 wt%, dezincification is not
likely to occur. However, as the zinc content increases, the sensitivity to
dezincification is increased. If the zinc content exceeds 30 wt%,
dezincification corrosion is more severe.
It has been reported in literatures that dezincification corrosion is
associated with alloy compositions and environmental factors. In the context
of alloy compositions, dezincification of brass alloy with a single a phase
and zinc content higher than 20 wt% gives porous copper, whereas
dezincification of brass alloy with double a+O phases begins initially in 0
phase and later expands to a phase when 0 phase is completely converted
into loosely-structured copper (see Kuaiji Wang et al., Chinese Journal of
Materials Research, Vol.13, pages 1-8).
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Since dezincification of brass alloy severely damages the structures of
brass alloys, the surface intensities of brass products produced from brass
alloys are decreased and porosity thus occurs on brass pipes. This
significantly decreases the lifetimes of the brass products, and causes
application problems. Therefore, standards like AS 2345 and ISO 6509 are
established for testing the dezincification resistance of a brass product,
i.e.
the depth of a dezincification layer formed on the surface of a brass product
shall not exceed 100 lAm.
Regarding the formulations of dezincification resistant brass alloys,
except for copper and zinc which are major ingredients, patents such as US
Patent No. 4,417,929 discloses a formulation comprising iron, aluminum and
silicon, US Patent Nos. 5,507,885 and US 6,395,110 disclose formulations
comprising phosphorus, tin and nickel, US Patent No. 5,653,827 discloses a
formulation comprising iron, nickel and bismuth, US Patent No. 6,974,509
discloses a formulation comprising tin, bismuth, iron, nickel and phosphorus,
US Patent No. 6,787,101 discloses a formulation comprising phosphorus, tin,
nickel, iron, aluminum, silicon and arsenic, and US Patent Nos. 6,599,378
and US 5,637,160 disclose adding selenium and phosphorus in a brass alloy
to achieve a dezincifying effect. Alternatively, please refer to Kuaiji Wang
et
at., Chinese Journal of Materials Research, Vol.13, pages 1-8, wherein a
dezincification effect is achieved by adding boron and selenium into a brass
alloy.
Conventional dezincification resistant brass alloys usually have higher
lead contents (most in the range from 1 to 3 wt%) for facilitating subsequent
processing of brass materials. However, as the awareness of environmental
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protection increases and the impacts of heavy metals on human health and
issues like environmental pollutions become major focuses, it is a trend to
restrict the usage of lead-containing alloys. Various countries, such as
Japan and the United States of America, have sequentially amended
relevant regulations and put intensive efforts to lower lead contents in the
environment by particularly demanding that no molten lead shall leak from
the lead-containing alloy materials used in products such as household
electronic appliances, automobiles and water systems to drinking water and
lead contamination shall be avoided during processing. Thus, there exists
an urgent need in the industry to develop a brass material having
dezincification resistance and possessing desirable properties like good
casting properties, machinability, corrosion resistance and mechanical
properties.
In order to eliminate damages to human bodies and environment, the
present invention provides a free cutting brass alloy including silicon and
antimony instead of lead, and further including arsenic for improving
dezincification resistance.
SUMMARY OF THE INVENTION
The present invention provides a dezincification resistant brass alloy,
including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of antimony (Sb);
0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of aluminum (Al); and
more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the brass alloy has effects of solid solution
strengthening due to the addition of silicon and aluminum. Further, the
addition of zinc influences mechanical strength and elongation rate of the
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brass alloy. In the present invention, silicon has the zinc equivalent
coefficient as about 10 to 12, and aluminum has the zinc equivalent
coefficient as about 4 to 6. The amount of silicon is 0.5 to 1.2 wt% of the
brass alloy, and the amount of aluminum is 0.4 to 0.8 wt% of the brass alloy.
Once the zinc equivalent is controlled to be lower than 45%, the tensile
strength of the brass alloy is about 320 MPa, the elongation rate is about
10.8%, and the hardness is about HRB 76. Apparently, the brass alloy of the
present invention has great mechanical strength and elongation rate.
In the present invention, the addition of silicon makes inter-metallic
compounds being separated out, so as to improve the cutting property of the
brass alloy. The cutting property and fluidity of the alloy melt are improved
as long as the amount of silicon is increased. However, when the amount of
silicon is more than 1.2 wt% and the zinc equivalent is more than 45%, the
brass alloy turns to be brittle and has decreased mechanical strength and
elongation rate. For example, when the zinc equivalent is 48%, the brass
alloy has the tensile strength as about 55 MPa, elongation rate as about 2%
and hardness as about HRC 30, and thus the brass alloy fails to have good
casting property. In addition, the brass alloy of the present invention
preferably includes 0.5 to 0.8 wt% of silicon.
In the present invention, the addition of aluminum improves the effect of
solid solution strengthening, increases the strength and hardness of the brass
alloy, and decreases the specific weight of the brass alloy. Moreover, due to
the addition of silicon, when the zinc equivalent is no more than 45% and
the amount of aluminum is more than 0.8 wt%, the elongation of the brass
alloy is decreased, the metal melt is easily oxidized to form slag and the
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fluidity of the brass alloy is lowered, such that the casting product of the
brass alloy may have some flow marking, entrapped slag and less compact.
Preferably, the brass alloy of the present invention includes 0.5 to 0.8 wt%
of aluminum.
The divacancy occurs on the surface of the brass alloy during corrosion,
and then the divacancy diffuses toward the interior of the brass alloy due to
the concentration gradient, and zinc atoms diffuse toward the surface of the
brass alloy, such that zinc is dissolved first.
Therefore, in the present invention, the dezincification resistant brass
alloy includes arsenic for inhibiting the re-deposition of copper.
Furthermore,
the arsenic atoms form a protection layer at the crystal boundary, so as to
occupy or diffuse into the divacancy for interrupting the dissolution of zinc,
and thus achieve dezincification resistance. Preferably, the brass alloy of
the
present invention includes 0.07 to 0.17 wt% of arsenic. The proper addition
amount of arsenic significantly improves the dezincification resistance of
the brass alloy; however, if the addition of arsenic is more than 0.17 wt%, no
relative improvement can be obtained.
In addition to improve mechanical properties for processing, such as
cutting property, antimony is added in the dezincification resistant brass
alloy, wherein antimony and copper form inter-metallic compounds as brittle
granules dispersed in S phase and phase boundary of 3 phase for improving
cutting property and filling the divacancy so as to decrease corrosion of the
brass alloy. Further, when the amount of antimony is more than 0.2 wt%, the
brittleness of the alloy is significantly increased and the strength of the
alloy
is further limited. Moreover, since antimony atoms aggregate at the crystal
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boundary of the alloy to form deflection, resulting hot embrittlement of the
casting product. Hence, the amount of antimony added in the brass alloy of
the present invention is 0.01 to 0.12 wt%.
In the present invention, as the addition of silicon increases, precipitation
of arsenic and antimony in aqueous solution is decreased (NSF 61-2007a
SPAC). When the amount of arsenic is more than 0.25 wt% and the amount
of antimony is more than 0.2 wt%, precipitation amount of arsenic and
antimony exceed the standard established in regulations, and cannot be
decreased even though the amount of silicon is increased. Based on the
about illustrations, the present invention provides a dezincification
resistant
brass alloy, including 0.5 to 1.2 wt% of silicon (Si); 0.01 to 0.2 wt% of
antimony (Sb); 0.02 to 0.25 wt% of arsenic (As); 0.4 to 0.8 wt% of
aluminum (Al); and more than 95.8 wt% of copper (Cu) and zinc (Zn).
In the present invention, the dezincification resistant brass alloy further
includes one or more selected from the group consisting of nickel, tin, boron
and lead. For example, the dezincification resistant brass alloy includes
nickel, tin, boron or lead. For example, the dezincification resistant brass
alloy includes 0.2 to 1.25 wt% of nickel and tin.
In one embodiment, the dezincification resistant brass alloy includes 0.1 to 1
wt% of tin. In another embodiment, the dezincification resistant brass alloy
includes 0.1 to 0.25 wt% of nickel. In addition, the dezincification resistant
brass alloy includes boron in a range from 1 to 20 ppm, and preferably in a
range from 5 to 15 ppm. The proper amount of nickel and tin are added to
improve corrosion resistance, and to increase the strength of the brass alloy.
The suitable amount of boron is added alloy material, which the process can
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to reduce grain size and improve the property of the brass alloy.
In another embodiment, the dezincification resistant brass alloy includes
0.05 to 0.18 wt% of lead. The proper amount of lead is added to improve
cutting property of the brass alloy.
The alloy can contain unavoidable impurities in an amount less than 0.2
wt%.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a metallographic structural distribution of a specimen of a
dezincification resistant brass copper alloy of the present invention;
FIG. 1B is a metallographic structural distribution of a specimen of a
CW602N brass specimen;
FIG. 1C is a metallographic structural distribution showing a specimen of
C85700 brass alloy;
FIG. 2A is diagram showing the fluidity of the dezincification resistant
brass alloy of the present invention;
FIG. 2B is diagram showing the fluidity of CW602N brass alloy;
FIG. 2C is diagram showing the fluidity of C85700 brass alloy;
FIG. 3A is a diagram showing the turning characteristic of the
dezincification resistant brass alloy of the present invention;
FIG. 3B is a diagram showing the turning characteristic of CW602N
brass alloy;
FIG. 3C is a diagram showing the turning characteristic of C85700 brass
alloy;
FIG. 4A is a metallographic structural distribution showing the specimen
of the dezincification resistant brass alloy of the present invention after
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performing a test of dezincification corrosion resistance;
FIG. 4B is a metallographic structural distribution showing the
specimen of CW602N brass alloy after performing a test of dezincification
corrosion resistance; and
FIG. 4C is a metallographic structural distribution showing the
specimen of C85700 brass alloy after performing a test of dezincification
corrosion resistance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The detailed description of the present invention is illustrated by the
following specific examples. Persons skilled in the art can conceive the
other advantages and effects of the present invention based on the disclosure
contained in the specification of the present invention.
In the specification of the present invention, the term "dezincification
resistant copper alloy/dezincification resistant brass alloy" is a commonly
used technological term in the field, and means an alloy having surfaces that
are tolerant to corroding conditions in the environment and not likely to
dezincify. AS 2345 regulations (Dezincification resistance of copper alloys)
are used as a basis to define that the depth of the dezincification layer
formed on the surface of a brass alloy product shall not exceed 100 pm.
Unless otherwise specified, the ingredients comprised in the
dezincification resistant brass alloy of the present invention, as discussed
herein, are all based on the total weight of the alloy, and are expressed in
weight percentages (wt%).
The composition of the dezincification resistant brass alloy in the
present invention meets the requirement as set forth in California Bill
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AB 1953, in which the materials of bathroom products contacting water must
have lead less than 0.25 wt%. Further, NSF 61 requires that lead leach much
be less than 5 ppb. The dezincification resistant brass alloy of the present
invention meets the above regulations and is applicable to faucets, water
pipes, water supply systems, and etc.
In accordance with inventor's research, the dezincification resistant
brass alloy includes specific amounts of silicon, antimony and arsenic to
have characteristics as those of the conventional lead brass. Specifically,
the
dezincification resistant brass alloy of the present invention includes only
0.5 to 1.2 wt% of silicon, 0.01 to 0.2 wt% of antimony and 0.02 to 0.25 wt%
of arsenic to have characteristics (such as cutting property) as those of the
conventional lead brass, is not prone to generate product defects like cracks
and slag inclusions, and complies with the dezincification requirement set
forth in AS-2345.. In addition, the dezincification resistant brass alloy of
the
present invention effectively reduces the cost of production, and is
extremely advantageous to commercial-scale productions and applications.
In an embodiment, the dezincification resistant brass alloy of the
present invention includes 58 to 65 wt% of copper, 0.5 to 1.2 wt% of
silicon, 0.01 to 0.2 wt% of antimony, 0.02 to 0.25 wt% of arsenic, 0.4 to
0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and
zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the
present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of
silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to
0.8 wt% of aluminum, less than 0.2 wt% of unavoidable impurities, and
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zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the
present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of
silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to
0.8 wt% of aluminum, less than 5 to 15 ppm of boron, 0.1 to 1 wt% of tin,
0.1 to 0.25 wt% of nickel, less than 0.2 wt% of unavoidable impurities, and
zinc in balance.
In another embodiment, the dezincification resistant brass alloy of the
present invention includes 59 to 63 wt% of copper, 0.5 to 0.8 wt% of
silicon, 0.01 to 0.12 wt% of antimony, 0.07 to 0.17 wt% of arsenic, 0.5 to
0.8 wt% of aluminum, 0.05 to 0.18 wt% of lead, less than 0.2 wt% of
unavoidable impurities, and zinc in balance.
The present invention is illustrated by the following exemplary
examples.
The ingredients of the dezincification resistant brass alloy of the present
invention used in the following test examples are described below, wherein
each of the ingredients is added at a proportion based on the total weight of
the alloy.
Example 1:
Cu: 61.32 wt% Si: 1.03 wt%
Sb: 0.1283 wt% Al: 0.6452 wt%
As: 0.0852 wt% Zn: in balance
Example 2:
Cu: 62.75 wt% Si: 0.653 wt%
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Sb: 0.047 wt% Al: 0.78 wt%
As: 0.169 wt% Zn: in balance
Example 3:
Cu: 62.63 wt% Si: 0.563 wt%
Sb: 0.052 wt% Al: 0.653 wt%
As: 0.165 wt% Ni: 0.152 wt%
B: 10 ppm Sn: 0.861 wt%
Zn: in balance
Example 4:
Cu: 64.47 wt% Si: 0.78 wt%
Sb: 0.015 wt% Al: 0.79 wt%
As: 0.142 wt% Pb: 0.115 wt%
Zn: in balance
The dezincification-resistant low lead brass alloy of the present
invention and foundry return were preheated for 15 minutes to reach a
temperature higher than 400., and the two were mixed at a weight ratio of
7:1, along with addition of 0.2 wt% of refining slag, for melting in an
induction furnace until the brass alloy reached a certain molten state
(hereinafter referred to as "molten copper liquid"). A metallic gravity
casting
machine was coupled with the sand core and the gravity casting molds to
perform casting, and a temperature monitoring system further controlled
temperatures so as to maintain the casting temperature to a range from 1010
to 1060C. In each casting, the feed amount was preferably 1 to 2 kilograms,
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and the casting time was controlled to a range from 3 to 8 seconds.
After the molds were cooled, the molds were opened and the casting
heads were cleaned. The mold temperatures were monitored so as to control
the mold temperatures to a range from 200 to 220C to form casting parts.
Then, the casting parts were released from the molds. Then, the molds were
cleaned to ensure that the site of the core head were clean. The graphite
liquid was spread on the surface of the molds following by cooling with
immersion. The temperature of the graphite liquid for cooling the mold was
preferably maintained at a range from 30 to 36C, and the specific weight of
the graphite liquid ranged from 1.05 to 1.06.
Self-checking was performed on the cooled casting parts, and the casting
parts were sent in a sand cleaning drum for cleaning. Then, an as-cast
treatment was performed, wherein a thermal treatment for distressing
annealing was performed on as-casts to eliminate the internal stress
generated by casting. The as-casts were subsequently mechanically
processed and polished, so that no sand, metal powder or other impurities
adhered to the cavity of the casting parts. A quality inspection analysis was
performed and the total non-defectiveness in production was calculated by
the following equation.
total non-defectiveness in production = the number of non-defective
products/the total number of products x 100%
Total non-defectiveness in production reflects the qualitative stability of
production processes. High qualitative stability of production processes
ensures normal production.
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Table 1. Ingredients, processing characteristics and total non-defectiveness
in production of the alloys
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W602N 59 lead brass ezincification resistant brass
alloy of the present invention
ompara ompara ompara ompar ompara ompara
ve Exampi Example Example Example
ive ive ive tive tive [e-.
example xample example example example ample el 2 3 4
2 3
1
(%) 1.39 62.92 62.14 62.39 1.86 62.01 61.32 62.75 62.63 64.47
Cu
0
Sb (%} 0.0010 <0.0010 0.0010 0.0010 0.0010 0.0010 .1283 0.047 0.052 ).015
As (%) .112 0.145 .127 .0014 .0011 .0016 .0852 .169 .165 .142
Si (%) .0161 .0035 1.0026 .028 .024 .021 1.03 .653 .563 ).78
Al (%) .634 .618 .601 .51 .58 .55 .6452 .78 .653 ).79
b (%) 1.83 .67 .12 1.47 1.69 1.871 .0086 .002 .0085 ).115
Sn (%) -- --- -- -- -- --- -- -- .861 ---
i (%) -- --- -- -- -- -- -- -- v.152 B (%) -- -- -- -- --- -- -- -- lOppm --
Inp
ut 150 150 150 150 150 150 150 150 150 150
astin (pcs
olishi out
g out 140 141 140 140 141 144 140 139 141 141
pcs
field 2% 93% 2% 2% 93% 6% 2% 0% 3% 3%
It is known from Table I that the dezincification resistant brass alloy of
the present invention gave a yield higher than 90% when it was used a raw
material.
In Example 3, tin was added and dissolved into copper solid solution, so
as to achieve solid solution strengthening and improve the resistance to
seawater corrosion. However, when the amount of tin is more than 2.0 wt%,
the brittle y phase occurs in the alloy, which adversely affects the
plasticity
of the alloy, and no relative corrosion resistance can be obtained. In
addition,
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in order to have great casting, mechanical processing and yield, the amount
of tin in the dezincification of the present invention is in a range from 0.1
to
1.0 wt%.
The addition of nickel makes copper liquid form fine crystals, and cleans
the copper substrate and crystal boundaries, so as to improve mechanical
property of brass casting products. In the brass alloy, nickel has relatively
high melting point. Therefore, the amount of nickel needs to be strictly
controlled to prevent nickel and other metal elements from forming brittle
inter-metallic compounds with high melting points which adversely affect
to thermal processing properties of the alloy and forms pores and cracks.
Accordingly, the amount of nickel in the dezincification resistant brass alloy
of the present invention is less than 0.25 wt%.
The addition of boron facilitates refinement of the brass alloy, and
increases the strength and hardness of the brass alloy. Further, boron slows
down the migration of divacancy, so as to improve dezincification resistance
of the brass alloy. However, when the amount of boron is more than 20 ppm,
boride slag aggregates, no relative strength and hardness of the brass alloy
can be obtained, and furthermore, the dezincification resistance of the brass
alloy is decreased. Hence, the amount of boron in the dezincification
resistant brass alloy of the present invention is less than 20 ppm which
makes the yield more than 93%.
The yield of the dezincification resistant brass alloy of the present
invention was comparable to those of conventional 59 lead brass (C85700
brass) and DR brass (CW602N brass), and can indeed be a substitute brass
material. The dezincification resistant brass alloy of the present invention
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can significantly decrease the lead content in the alloy, effectively avoid
the
lead contamination occurred during processes, and decrease the amount of
lead leach during processing. It is clear that the dezincification resistant
brass alloy of the present invention has material characteristics to meet the
environmental requirements.
Test example 2:
FIGS. 1A to 1C illustrate the structural distributions showing the materials
of the dezincification resistant brass alloy of the present invention (Example
2), CW602N brass (Comparative Example 1) and 59 lead brass
(Comparative Example 4) when the specimens were examined under an
optical metallographic microscope at 100X magnification.
The measured values of the major ingredients of the alloy in Examples 2
are as follows: Cu: 62.75%, Zn: 35.42%, Si: 0.653%, Sb: 0.047%, Al:
0.78% and As: 0.169%.
As shown in FIGS. 1A to 1C, the structure of a phase of the metallography
of the CW602N brass (as shown FIG. 1B) was coarse, indicating that the
CW602N brass had good plasticity but poor cutting property. The
metallography of the 59 lead brass showed dendritic structures with a+(6
phase. The dezincification resistant brass alloy of the present invention had
Si and Sb added therein, such that the metallography of the dezincification
resistant brass alloy of the present invention showed a phase. In the brass
alloy of the present invention, the addition of Si expanded the region of 0
phase, and thus the strength and hardness of the brass alloy were increased.
Further, in the brass alloy of the present invention, Si and Cu formed
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inter-metallic compounds so as to increase hardness and improve cutting
property; and Si was present at # phase and boundaries of lS phase as
inter-metallic compounds to improve the cutting property of the brass alloy.
Accordingly, the dezincification resistant brass alloy of the present
invention had excellent mechanical property.
Test example 3:
The test of fluidity was performed on the dezincification resistant brass
alloy of the present invention (Example 2), DR brass (CW602N brass)
(Comparative Example 2) and 59 lead brass (C85700 brass) (Comparative
Example 5), wherein the furnace temperature was 1000C and the mold
temperature was 150C. The results were shown in PIGS. 2A to 2C. In the
fluidity test, the flow distance of the DR brass (CW602N brass) was about
580 mm, the flow distance of the 59 lead brass was about 600 mm, and the
flow distance of the dezincification resistant brass alloy of the present
invention was about 700 mm. Accordingly, the dezincification resistant
brass alloy of the present invention had great fluidity for casting.
Test example 4:
The turning test was performed on the dezincification resistant brass alloy
of the present invention (Example 3), DR brass (CW602N brass)
(Comparative Example 3) and 59 lead brass (C85700 brass) (Comparative
Example 6), wherein the parameters were set as follows; 610 rpm, feed
amount: 2 mm and feed rate: 0.2 mm/rpm. The cutting results were shown
in FIGS. 3A to 3C.
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The turning length of the DR brass (CW602N brass) was about 2 mm and
was shown as a C-shaped or short whirlpool-like sheet; the turning length of
the 59 lead brass (C85700 brass) was about 2 mm and was shown as a
C-shaped sheet; and the turning length of the dezincification resistant brass
alloy of the present invention was about 5 mm and was shown as a
C-shaped sheet. Accordingly, the dezincification resistant brass alloy of the
present invention had turning characteristics, i.e. great mechanical
processing property.
Test example 5:
A dezincification test was performed on the dezincification resistant brass
alloy of the present invention (Example 3), DR brass (CW602N brass)
(Comparative Example 1) and 59 lead brass (C85700 brass) (Comparative
Example 4) to test the corrosion resistance of the brasses. The
dezincification test was performed according to the Australian standard
AS2345-2006 "Dezincification resistance of copper alloys". Before a
corrosion experiment was performed, a novolak resin was used to make the
exposed area of each of the specimens be 100 mm2. The specimens were
ground flat using a 600# metallographic abrasive paper, following by
washing using distilled water. Then, the specimens were baked dry. The test
solution was 1% CuC12 solution prepared before use, and the test
temperature was 75 2C. The specimens and the CuCI2 solution were placed
in a temperature-controlled water bath to react for 24 0.5 hours. The
specimens were removed from the water bath, and out along the vertical
direction. The cross-sections of the specimens were polished, and then the
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depths of corrosion of the specimens were measured and observed under a
digital metallographic electronic microscope.
As shown in FIG. 4A, the average dezincification depth of
dezincification resistant brass alloy of the present invention in Example 3
was 74.81 um. As shown in FIG. 4B, the average dezincification depth of
the CW602N brass in Comparative example 1 was 82.28 pm. As shown in
FIG. 4C, the average dezincification depth of the 59 lead brass was 336.72
Am.
It is corroborated from the above results that the dezincification resistant
brass alloy of the present invention meets the dezincification resistance
standard set forth in AS2345-2006 (i.e. the depth of a dezincification layer
not exceeding 100 pm).
Test example 6:
A test of mechanical properties was performed on the specimens in the
examples according to the standard set forth in IS06998-1998 "Tensile
experiments on metallic materials at room temperature". Results are shown
in Table 2.
Table 2
Mechanical properties
Material Tensile strength QM an Elongation00d
1 2 3 4 5 average 1 2 3 4 5 averag
e
Example 2 320 315 305 325 308 314.6 10 11 11 10 12 10.8
Comparativ
e example 356 337 363 374 367 359.4 12 11 13 13 12 12.2
4
Comparativ
e example 361 387 378 359 383 373.6 11 11 13 11 12 11.6
1
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It is known from Table 2 that the tensile strength and the elongation (%)
of dezincification resistant brass alloy in the present invention were
comparable to those of the conventional 59 lead brass and CW602N,
meaning that the dezincification resistant brass alloy of the present
invention had mechanical properties comparable to those of the 59 lead
brass and CW602N. Further, the lead content of the dezincification resistant
brass alloy of the present invention was less than 0.18 wt%, thereby
complying with the environmental requirements. It appears that the
dezincification resistant brass alloy of the present invention can indeed
replace the 59 lead brass and CW602N brass in product manufacturing.
Test example 7:
The test was performed according to the standard set forth in NSF
61-2007a SPAC for the allowable precipitation amounts of metals in
products, to examine the precipitation amounts of the metals of the brass
alloys in an aqueous environment. Results are shown in Table 3.
Table 3. Precipitation amounts of the metals in the products
Element Upper Comparative Comparative Comparative Comparative Example Example
limit example 1 example 1 example 4 example 4 1 4
(ug/L) (by lead (by lead
stripping stripping
treatment) treatment)
Pb 5.0 22.863 1.538 14.835 0.861 0.958 1.2384
Sb 0.6 0.006 0.005 0.013 0.012 0.487 0.125
Al 5.0 0.191 0.162 0.415 0.349 4.572 7.852
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As 1 0.061 0.058 0.452 0.398 0.573 0.752
As shown in Table 3, the precipitation amounts of each metal of the
dezincification resistant brass alloy of the present invention were lower than
the upper limits of the standard values, and therefore, the dezincification
resistant brass alloy of the present invention meets the standard set forth in
NSF 61-2007a SPAC. The materials of Comparative examples 1 and 4 had
lead contents significantly exceeding the standard values when no lead
stripping treatments were performed. It appears that only the brass alloys of
Example I and Example 4 meet the standard set forth in NSF 61-2007a
SPAC without performing a lead stripping treatment. Further, the
dezincification resistant brass alloy of the present invention clearly had a
significantly lower precipitation amount of the heavy metal, lead, than those
of the 59 lead brass (C85700 brass) and the DR brass (CW602N brass).
Thus, the dezincification resistant brass ally of the present invention is
more environmentally friendly, and more beneficial to human health.
In conclusion, the dezincification resistant brass alloy of the present
invention has excellent casting properties and good toughness and
machinability, and it is thus not likely to generate defects like cracks and
slag inclusions or casting defects. Therefore, the dezincification resistant
brass alloy of the present invention can achieve the material characteristics
possessed by lead brasses, and be suitable for applications to subsequent
processes. Further, there is no need to perform a lead stripping treatment on
the dezincification resistant brass alloy of the present invention. This can
lower the production costs, and is extremely advantageous in
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CA 02718613 2010-10-20
commercial-scale productions and applications.
The invention has been described using exemplary preferred
embodiments. However, it is to be understood that the scope of the
invention is not limited to the disclosed arrangements. The scope of the
claims, therefore, should be accorded the broadest interpretation, so as to
encompass all such modifications and similar arrangements.
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