U.S. patent application number 12/644254 was filed with the patent office on 2010-06-24 for lead-free free-cutting aluminum brass alloy and its manufacturing method.
Invention is credited to Zhenqing Hu, Chuankai Xu, Siqi Zhang.
Application Number | 20100155011 12/644254 |
Document ID | / |
Family ID | 42264359 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100155011 |
Kind Code |
A1 |
Xu; Chuankai ; et
al. |
June 24, 2010 |
Lead-Free Free-Cutting Aluminum Brass Alloy And Its Manufacturing
Method
Abstract
The present invention provides a lead-free free-cutting aluminum
brass alloy and its manufacturing method. The alloy comprises:
57.0.about.63.0 wt % Cu, 0.3.about.0.7 wt % Al, 0.1.about.0.5 wt %
Bi, 0.2.about.0.4 wt % Sn, 0.1.about.0.5 wt % Si, 0.01.about.0.15
wt % P, at least two elements selected from the group of 0.01-0.15
wt % Mg, 0.0016-0.0020 wt % B, and 0.001-0.05 wt % rare earth
elements and the balance being Zn and unavoidable impurities. The
inventive alloy has excellent castability, weldability, cuttability
and corrosion resistance. It is suitable for low pressure die
casting, gravity casting, horizontal continuous casting, forging
and extrusion. Its metal material cost is lower than bismuth brass.
It is particularly applicable for components used in drinking water
supply systems and other structural components. It is a new
environmentally-friendly free-cutting aluminum brass alloy.
Inventors: |
Xu; Chuankai; (Xiamen City,
CN) ; Hu; Zhenqing; (Xiamen City, CN) ; Zhang;
Siqi; (Changsha City, CN) |
Correspondence
Address: |
Daniel N. Christus;McDermott Will & Emery LLP
227 West Monroe Street, Suite 4400
Chicago
IL
60606-5096
US
|
Family ID: |
42264359 |
Appl. No.: |
12/644254 |
Filed: |
December 22, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12643513 |
Dec 21, 2009 |
|
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12644254 |
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Current U.S.
Class: |
164/459 ;
164/113; 420/471 |
Current CPC
Class: |
C22C 9/00 20130101; B22D
21/027 20130101; B22D 11/004 20130101; C22C 9/01 20130101 |
Class at
Publication: |
164/459 ;
420/471; 164/113 |
International
Class: |
B22D 11/00 20060101
B22D011/00; C22C 9/01 20060101 C22C009/01; B22D 17/02 20060101
B22D017/02; C22C 9/00 20060101 C22C009/00; C22C 9/02 20060101
C22C009/02; C22C 9/04 20060101 C22C009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2008 |
CN |
200810188263.4 |
Claims
1. A lead-free free-cutting aluminum brass alloy comprising:
57.0.about.63.0 wt % Cu, 0.3.about.0.7 wt % Al, 0.1.about.0.5 wt %
Bi, 0.1.about.0.4 wt % Sn and the balance being Zn and unavoidable
impurities.
2. A lead-free free-cutting aluminum brass alloy comprising:
57.0.about.63.0 wt % Cu, 0.3.about.0.7 wt % Al, 0.1.about.0.5 wt %
Bi, 0.2.about.0.4 wt % Sn, 0.1.about.0.5 wt % Si, 0.01.about.0.15
wt % P, at least two elements selected from the group of 0.01-0.15
wt % Mg, 0.0016-0.0020 wt % B, 0.001-0.05 wt % rare earth elements
and the balance being Zn and unavoidable impurities.
3. The lead-free free-cutting aluminum brass alloy of claim 2
comprising 0.4-0.6 wt % Al, 0.2-0.5 wt % Si and 0.1-0.3 wt %
Bi.
4. The lead-free free-cutting aluminum brass alloy of claim 1,
wherein the impurities comprising .ltoreq.0.1 wt % Pb, .ltoreq.0.1
wt % Fe and .ltoreq.0.03 wt % Sb.
5. The lead-free free-cutting aluminum brass alloy of claim 2,
wherein the impurities comprising .ltoreq.0.1 wt % Pb, .ltoreq.0.1
wt % Fe and .ltoreq.0.03 wt % Sb.
6. The lead-free free-cutting aluminum brass alloy of claim 3,
wherein the impurities comprising .ltoreq.0.1 wt % Pb, .ltoreq.0.1
wt % Fe and .ltoreq.0.03 wt % Sb.
7. The manufacturing method of claim 1, wherein the temperature for
low pressure die casting is 980-1000.degree. C.
8. The manufacturing method of claim 2, wherein the temperature for
low pressure die casting is 980-1000.degree. C.
9. The manufacturing method of claim 3, wherein the temperature for
low pressure die casting is 980-1000.degree. C.
10. The manufacturing method of claim 1, wherein the mold forging
temperature for horizontal continuous castings is 650-710.degree.
C.
11. The manufacturing method of claim 2, wherein the mold forging
temperature for horizontal continuous castings is 650-710.degree.
C.
12. The manufacturing method of claim 3, wherein the mold forging
temperature for horizontal continuous castings is 650-710.degree.
C.
Description
RELATED APPLICATION
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 12/643,513, filed Dec. 21, 2009, and claims
priority therefrom.
FIELD OF THE INVENTION
[0002] The present invention generally relates to a lead-free
free-cutting aluminum brass alloy, in particular a lead-free
free-cutting aluminum brass alloy and its manufacturing method
which is applicable in low pressure die castings and forgings.
BACKGROUND OF THE INVENTION
[0003] Currently, when people search and develop lead-free or low
lead free-cutting brass alloys, they typically follow two routes to
find the elements which could replace Lead: one route is to select
the elements which hardly form solid solutions in Cu and can't form
intermetallic compounds with Cu, such as Bi, Se and Te, etc; the
other route is to select the elements which will form solid
solutions in Cu wherein the solid solubility is reduced with
decreasing temperature, so as to form intermetallic compounds with
Cu, and with Sb, P, Mg, Si, B and Ca, etc. The first route has been
well-known for some time. The second route is a more recent
development.
[0004] In the process of researching and developing, considering
the process properties, and comparing properties versus market cost
requirements, the selection of elements for an alloy, and their
range, will vary. Therefore, varied lead-free free-cutting brass
alloys have been invented The bismuth brass alloy invention is the
most common of these alloys.
[0005] For example, Pub. No. CN101225487A to Xuhong Hu discloses an
arsenic-containing low-lead brass alloy which comprises (wt %)
57-62 Cu, 36-43 Zn, 0.01-1.0 Al, 0.05-2.5 Bi, 0.005-0.3 As,
.ltoreq.0.2 Pb and .ltoreq.0.65 Sn, wherein small amounts of Ni, Fe
and S and minimum amounts of Si, Mg, Mn and Re (Rhenium) are
selectively added. No P is added. Arsenic is one of the main
elements of such an alloy. If its As content is in the middle to
upper limits of the above-specified range, and if the content of Pb
is in the range of 0.1-0.2 wt %, then both As and Pb are released
into the water in amounts that will exceed the upper limits of the
NSF standard. Therefore, such brass alloys cannot be used in the
components for drinking water supply systems, such as faucets and
valves.
[0006] Pat. No. CN1045316C to Kohler discloses a low-lead bismuth
brass alloy which comprises (wt %) 55-70 Cu, 30-45 Zn, 0.2-1.5 Al,
0.2-0.3 Bi, .ltoreq.1.0 Pb, .ltoreq.2.0 Ni, .ltoreq.1.0 Fe,
.ltoreq.0.25 In, and 0.005-0.3 Ag, further comprising minimal
amounts of one or more of the elements Ta, Ga, V, B, Mo, Nb, Co,
and Ti. Zr is selectively added. No Si or P is added.
[0007] Pub. No. CN1710126A to Powerway discloses a lead-free
free-cutting low-antimony bismuth brass alloy and its manufacturing
method which comprises (wt %) 55-65 Cu, 0.3-1.5 Bi, 0.05-1.0 Sb,
0.0002-0.05 B, wherein elements such as Ti, Ni, Fe, Sn, P and rare
earth elements are selectively added and the balance is Zn and
impurities. No Si or Al is added. If the content of Sb is
.gtoreq.0.1, the amount of Sb released in the water will exceed the
requirements of the NSF standard.
[0008] JP2000-239765A to Joetsu discloses a lead-free brass alloy
with corrosion resistance for castings, which comprises (wt %)
64-68 Cu, 1.0-2.0 Bi, 0.3-1.0 Sn, 0.01-0.03 P, 0.5-1.0 Ni, 0.4-0.8
Al, <0.2 Fe and the balance being Zn and impurities. The content
of Bi is higher and no Si is added.
[0009] With the increasingly extensive application of bismuth
brasses, their negative effects are also increasingly notable, such
as susceptibility to hot and cold cracking, poor weldability, the
necessity to slowly heat and cool when annealing, etc. The cause of
these negative effects has a common thermodynamic reason: the large
differential between the surface tension of bismuth (350 dyne/cm)
and that of copper (1300 dyne/cm), and the fact that bismuth cannot
form a solid solution in copper and cannot form intermetallic
compounds with copper. As a result, liquid bismuth has good wetting
with .alpha. and .beta. grains of copper and brass. The dihedral
angle between bismuth and copper or brass tends to zero. After
solidification, bismuth is distributed in the grain boundary in the
form of a continuous film.
[0010] Nowadays, the developed bismuth brasses are mainly
deformation alloys and comprise more than 0.5 wt % bismuth. The
public casting bismuth brasses, such as C89550 (which comprises
0.6.about.1.2 wt % Bi), have high tendencies to experience hot
cracking during low pressure die casting, and are not easily
welded.
[0011] Lead-free or low-lead free-cutting antimony brass has
excellent castability, weldability, hot working formability, and
dezincification corrosion resistance. However, antimony is more
toxic than lead. The NSF/ANSI61-2007 standard requires that Sb is
released in drinking water in amounts .ltoreq.0.6 .mu.g/L and that
Pb is released in amounts .ltoreq.1.5 .mu.g/L (NSF61-2005 requires
that Pb release is .ltoreq.5 .mu.g/L). Antimony brass is not
suitable for components used in drinking water supply system.
[0012] Lead-free free-cutting silicon brass is a brass which has
certain good developing prospects. Currently researched and
developed lead-free free-cutting silicon brasses are mainly
low-zinc deformation silicon brass. Most of them comprise small
amounts of bismuth and the cost of raw material is rather
higher.
[0013] Aluminum brass has good corrosion resistance, but its
cuttability is inadequate. Few patents and other literature exists
relating to lead-free free-cutting aluminum brasses. U.S. Pat. No.
3,773,504 (1973) discloses a Cu--Zn--Al--P series alloy having wear
resistance. Japanese Patent 2003-253358 discloses a lead-free
free-cutting low-zinc aluminum brass (containing vanadium and
boron, etc.)
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1A, 1B and 1C show the chip shape of example alloy 1
obtained at a cutting speed of 40 m/minute, at feeding quantities
of 0.1, 0.2, and 0.3 mm/revolution, respectively.
[0015] FIGS. 1D, 1E and 1F show the chip shape of alloy
CuZn40Pb1Al0.6 obtained at a cutting speed of 40 m/minute, at
feeding quantities of 0.1, 0.2, and 0.3 mm/revolution,
respectively.
[0016] FIGS. 2A, 2B and 2C show the chip shape of example alloy 1
obtained at a cutting speed of 60 m/minute, at feeding quantities
of 0.1, 0.2, and 0.3 mm/revolution, respectively.
[0017] FIGS. 2D, 2E and 2F show the chip shape of alloy
CuZn40Pb1Al0.6 obtained at a cutting speed of 60 m/minute, at
feeding quantities of 0.1, 0.2, and 0.3 mm/revolution,
respectively.
[0018] FIGS. 3A, 3B and 3C show the chip shape of example alloy 1
obtained at a cutting speed of 80 m/minute, at feeding quantities
of 0.1, 0.2, and 0.3 mm/revolution, respectively.
[0019] FIGS. 3D, 3E and 3F show the chip shape of alloy
CuZn40Pb1Al0.6 obtained at a cutting speed of 80 m/minute, at
feeding quantities of 0.1, 0.2, and 0.3 mm/revolution,
respectively.
[0020] FIGS. 4A, 4B and 4C show the chip shape of example alloy 1
obtained at a cutting speed of 100 m/minute, at feeding quantities
of 0.1, 0.2, and 0.3 mm/revolution, respectively.
[0021] FIGS. 4D, 4E and 4F show the chip shape of alloy
CuZn40Pb1Al0.6 obtained at a cutting speed of 100 m/minute, at
feeding quantities of 0.1, 0.2, and 0.3 mm/revolution,
respectively.
DETAILED DESCRIPTION
[0022] The object of the present invention is to solve the
technical problems of current aluminum brass alloys, including bad
cuttability, a tendency of hot cracking and difficulty in welding.
The object of the invention also includes the provision of an
environment-friendly lead-free free-cutting aluminum brass alloy,
which is applicable for low pressure die casting, gravity casting,
horizontal continuous casting, forging and welding.
[0023] The object of the present invention is realized by selection
of the following elements and their composition design. The present
invention provides a lead-free free-cutting aluminum brass alloy
which comprises (wt %): 57.0.about.63.0 Cu, 0.3.about.0.7 Al,
0.1.about.0.5 Bi, 0.1.about.0.4 Sn, the balance being zinc and
unavoidable impurities. The present invention also provides another
alloy which comprises (wt %): 57.0.about.63.0 Cu, 0.3.about.0.7 Al,
0.1.about.0.5 Bi, 0.1.about.0.5 Si, 0.1.about.0.4 Sn,
0.01.about.0.15 P, and which further comprises at least two
elements selected from Mg, B and rare earth elements, with the
balance being Zn and unavoidable impurities. The at least two
selected elements are present in amount of 0.01.about.0.15 wt % Mg,
0.001.about.0.05 wt % rare earth elements and 0.0016.about.0.0020
wt % B.
[0024] When bismuth content is in the middle to upper limits of the
specified range, .alpha. phase and a small amount of .beta. phase
dominate the matrix phase of the alloy. When bismuth content is in
the lower to middle limits of the specified range, .beta. phase and
small amounts of .alpha. phase and .gamma. phase dominate the
matrix phase of the alloy.
[0025] In the inventive alloy, aluminum is the main alloy element,
except for zinc. Al can improve corrosion resistance and strength
of common brass. During the melting and casting process, bismuth
can form compact oxide film for preventing melt oxidation, and for
reducing the loss of zinc, which is prone to volatilize and
oxidize. However, oxidation characteristics of aluminum are
unfavorable for castability and weldability. In addition, aluminum
will coarsen the grain of common brass. The zinc equivalent
coefficient of aluminum is rather great, and can substantially
enlarge the .beta. phase zone. If combined with silicon, aluminum
is prone to increase the .beta. phase rate, and promote the
formation of the .gamma. phase. Therefore, it is beneficial for
improving the cuttability of brass. The surface tension of aluminum
(860 dyne/cm) is less than that of copper. It can form solid
solutions in copper resulting in decreasing the surface tension of
copper. It is favorable for spherifying bismuth, which is
distributed in the grain boundary. The surface tension of zinc (760
dyne/cm) is less than that of copper. It can form solid solutions
in copper. It is also favorable for spherifying bismuth which is
distributed in the grain boundary. In this inventive alloy,
aluminum content is lower than common commercialized aluminum
brass, and is limited in the range of 0.3.about.0.7 wt %, more
preferably in the range of 0.4.about.0.6 wt %. Higher aluminum
content is not beneficial for castability and weldability.
[0026] Bismuth is added to improve the cuttability of aluminum
brass. However, as mentioned above, bismuth will increase the hot
and cold cracking tendency of copper alloys. The thermodynamic
reason for this is the large differential between the surface
tension of bismuth and copper, with the result that the dihedral
angle between liquid bismuth and solid copper grain tends to be
zero. Bismuth will fully wet copper grains. After solidification,
bismuth will be distributed in the grain boundary in the form of a
continuous film. In order to promote bismuth spheroidization and
reduce its unbeneficial effect, the present invention selects the
elements which can form solid solutions in copper and decrease the
surface tension of copper, such as the above-mentioned main alloy
elements, zinc and aluminum. Other optional elements are P, Sn, In,
Ga, Ge, Mg, B, Ca, etc. On the other hand, the elements which can
form solid solutions in bismuth, and which have surface tension
greater than bismuth, such as Pb, Se, Tl, etc, can also promote
bismuth spheroidization. The first of the above-mentioned elements,
In, Ga and Ge, are very expensive, so only a few bismuth brasses
selectively add them. Among the second group of the above-mentioned
elements, Pb's pollution to the environment and harmfulness to the
human body have been a concern. Selenium and thallium are also
toxic. NSF61 standard requires that in drinking water, Se release
should be .ltoreq.5.0 .mu.g/L (equal to Pb) and Tl release should
be .ltoreq.0.2 .mu.g/L (equal to Hg). Ingestion of trace amounts of
selenium is not harmful, but in excessive amounts, will damage the
skin. Selenium and thallium are also very expensive. In this
inventive alloy, selenium and thallium are not added, and thus
thallium cannot leach into the water. In this inventive alloy,
bismuth content is limited in the range of 0.1.about.0.5 wt %.
Higher bismuth content will not only increase the tendency of hot
cracking, which makes castings crack from time to time during low
pressure die casting, but also increase cost, reduce corrosion
resistance and increase the risk of thallium as an impurity in
amounts beyond the standard. The content of Bi is limited in the
range of 0.1.about.0.5 wt %, more preferably in the range of
0.1.about.0.3 wt %, so that it can achieve castability,
weldability, cuttability and low cost.
[0027] The effects of Tin mainly include strengthening the solid
solution, and improving dezincification corrosion resistance of the
alloy. If .gamma. phase is formed in the alloy, small amounts of
tin will make .gamma. phase more effectively dispersed, uniformly
distributed, and decrease the harmful effects of .gamma. phase on
plasticity, and further improve cuttability. The surface tension of
tin is 570 dyne/cm. The effect of zinc in promoting bismuth
spheroidizing is greater than the spheroidizing effect of zinc and
aluminum. Tin content is limited to the range of 0.1.about.0.4 wt
%. Higher content of tin is helpful for bismuth spheroidizing, but
cost will increase, and together with silicon and aluminum, more
.gamma. phase will be produced resulting in increasing hardness,
decreasing plasticity and unbeneficial effects for cutting and
forming.
[0028] The effects of silicon include improving castability,
weldability and corrosion resistance of the alloy, and remarkably
enlarging .beta. phase zone. Under certain zinc content, silicon is
the main element for adjusting the composition of matrix phase. If
there is an appropriate matching ratio among silicon and zinc and
aluminum, silicon will promote the formation of .gamma. phase in
the alloy and then improve the cuttability. With the increasing of
silicon content, .gamma. phase will increase and cuttability will
be improved. However, the plasticity will gradually decrease and
tendency of hot cracking will increase. It is not beneficial for
casting forming, especially for low pressure die casting
forming.
[0029] In the case that cuttability is guaranteed by bismuth,
silicon content is limited in the range of 0.1.about.0.5 wt %, and
is more preferably limited in the range of 0.2.about.0.5 wt %. When
bismuth content is in the middle to upper limits of the specified
range and silicon content is in the middle to lower limits of the
specified range, the matrix phase of the alloy is .alpha. phase and
minor amount of .beta. phase.
[0030] When bismuth content is in the middle to lower limits of the
specified range and silicon content is in the middle to upper
limits of the specified range, the matrix phase of the alloy is
.beta. phase and minor amount of .alpha. phase and .gamma.
phase.
[0031] Phosphorus is one of the main elements of the alloy. Its
effects include deoxidation, improving castability and weldability
of the alloy, reducing the oxidation loss of beneficial elements
such as aluminum, silicon, tin and bismuth, and refining brass
grains. If phosphorus content in the brass exceeds 0.05 wt %,
intermetallic compound Cu.sub.3P will be formed. It is beneficial
for improving the cuttability of the alloy, but meanwhile, the
plasticity will be decreased. Excessive Cu.sub.3P resulting from
excessive phosphorus will increase the tendency of hot cracking
during low pressure die casting.
[0032] In addition, the surface tension of phosphorus is 70 dyne/cm
and phosphorus has bigger solid solubility in copper at high
temperature; therefore it will obviously decrease the surface
tension of copper and improve the effect of bismuth
spheroidization. It is a "plasticizer" of bismuth-contained
brass.
[0033] In the presence of phosphorus, tin, aluminum and zinc,
bismuth will be spherically distributed in grain and in grain
boundary. It will obviously decrease its unbeneficial influence for
cold and hot plasticity and improve castability and weldability.
Meanwhile, as bismuth is spherically, uniformly and dispersedly
distributed, it is favorable for bismuth to play its beneficial
influence on cuttability.
[0034] Phosphorus content is limited in the range of
0.01.about.0.15 wt %. If it is used for horizontal continuous
castings or forgings, its content is in the middle to upper limits
of the specified range. If it is used for low pressure die casting
products (such as the bodies of a faucet), its content is in the
middle to lower limits of the specified range.
[0035] Magnesium is a selectively added element. Its main effects
include further deoxidizing before horizontal continuous casting
and preventing castings from cracking during low pressure die
casting and welding. If magnesium content exceeds 0.1 wt %, the
effect on preventing castings from cracking is still obvious.
However, the elongation rate will be decreased. This effect also
appears in lead-free free-cutting high-zinc silicon brass.
Magnesium also has the effect of grain refinement with the result
that bismuth and hard-brittle intermetallic compounds grain is more
dispersedly and uniformly distributed and is beneficial for
improving cuttability, castability and weldability.
[0036] If magnesium content is larger than 0.1 wt %, it will form
intermetallic compound Cu.sub.2Mg with copper and is also
beneficial for improving cuttability. If magnesium is added, its
content is preferably limited in the range of 0.01.about.0.15 wt
%.
[0037] The main effect of selectively adding boron and rare earth
metal is for grain refinement. The solid solubility of boron in
copper is very small, but it will be reduced with the temperature
decrease. Precipitated boron also has the effect of improving
cuttability. Boron also could suppress dezincification. In addition
to grain refinement, rare earth metal also can clean the grain
boundary and reduce the unbeneficial effects resulting from the
impurities in the grain boundary. Cerium and bismuth can form
intermetallic compound BiCe whose melting point reaches up to
1525.degree. C. so that bismuth can enter into the grain boundary
in the form of such intermetallic compound. It is favorable for
eliminating the hot and cold brittleness caused by bismuth, but
meanwhile the contribution of bismuth on cuttability is
reduced.
[0038] Magnesium, boron, and the rare earth elements are added in
small amounts.
[0039] In the inventive alloy, Zr and C are present only as
unavoidable impurities. Zr and C are not required in the alloy. If
Zr is present as an unavoidable impurity, the amount of Zr at most
at 0.0007 wt %. If C is present as an unavoidable impurity, the
amount of C will be less than 0.0015 wt %. The alloy does not
require Ni.
[0040] In the inventive alloy, lead, iron and antimony may be
present as unavoidable impurities, but their content should be
limited in the range of .ltoreq.0.1 wt %, .ltoreq.0.1 wt % and
.ltoreq.0.03 wt %, respectively. If Pb.gtoreq.0.2 wt %, Pb released
will exceed government standards. If Sb>0.05 wt %, Sb released
will exceed the standard. Therefore, the alloy containing such
larger content is not applicable for the components used in
drinking water systems.
[0041] Trace antimony can improve dezincification corrosion
resistance of the alloy, like tin and arsenic. In the common
casting copper alloys, the allowed iron content is larger than 0.2
wt %. In the inventive alloy, aluminum and silicon are present and
iron will form hard-brittle iron-aluminum intermetallic compounds
and iron silicide, which will decrease the plasticity, corrosion
resistance and castability. In addition, if the hard particles
formed by these intermetallic compounds are placed on the surface
of the products, after polishing and electroplating, a "hard spots"
defect characterized by inconsistent brightness will appear. Any
such products must be scrapped.
[0042] Alloys containing small amounts of such impurities are
beneficial for collocation using lead brass, antimony brass,
phosphorus brass, magnesium brass and other old brass materials,
saving resource and cost.
[0043] The features of selection of the above alloy elements and
their composition design include making bismuth be spherically,
uniformly and dispersedly distributed in the grain and in the grain
boundary, instead of continuous film distribution in the grain
boundary. One should generally consider the high standard
requirements of processing properties (casting, welding, cutting,
plating and etc.). One should also consider using performance
criteria (dezincification corrosion, stress corrosion, salt spray
corrosion, metal release amount in water, leakage, hardness,
strength, elongation rate, consistent brightness on the
electroplating surface) and the cost.
[0044] The invented alloy and old bismuth brass alloy can be
recycled. Lead brass, antimony brass, phosphorus brass, magnesium
brass and other old brass materials can be used for saving
resources and cost.
[0045] The manufacturing method is easily operated, and current
lead brass manufacturing equipment can be used.
[0046] In order to take all processing properties and using
performance into consideration, the volume shrinkage samples should
ensure that the surface of concentrating shrinkage cavities is
smooth, there is no porosity in depth, the elongation rate of
as-cast is larger than 6%, the hardness HRB is in the range of
55.about.75, and the bending angle of the strip samples is larger
than 55.degree..
[0047] The inventive alloy is a new environment-friendly aluminum
brass, especially applicable for low pressure die casting or
gravity casting or forging products which are subject to cutting
and welding, such as components for drinking water supply
systems.
[0048] The manufacturing method of the inventive alloy is as
follows:
[0049] Materials proportion--melting in main-frequency induction
furnace and being protected by the covering agent--tapping at
1000.degree. C., and pouring to be ingots--remelting--low pressure
die casting (980.about.1000.degree. C.) or horizontal continuous
casting (990.about.1030.degree. C.) forging (650.about.710.degree.
C.)
EXAMPLES
[0050] The alloy composition in examples is shown in Table 1.
TABLE-US-00001 TABLE 1 Alloy composition in examples (wt %)
Examples Cu Al Bi Sn Si Mg B Re P Zn 1 60.13 0.52 0.48 0.275 0.12
-- 0.0017 0.005 0.0653 Balance 2 58.72 0.38 0.41 0.165 0.23 0.09
0.0016 -- 0.093 Balance 3 59.60 0.49 0.30 0.133 0.182 0.07 0.0017
-- 0.0128 Balance 4 61.06 0.42 0.24 0.242 0.13 0.105 -- 0.01 0.051
Balance 5 61.27 0.43 0.29 0.251 0.27 0.133 -- 0.03 0.062 Balance 6
60.82 0.39 0.23 0.318 0.24 0.08 -- 0.01 0.075 Balance 7 60.26 0.42
0.37 0.327 0.31 0.07 0.019 0.04 0.082 Balance
[0051] 1. Castability
[0052] Castability of the inventive alloy is measured by four kinds
of common standard test samples for casting alloys.
[0053] Volume shrinkage test samples are used for measuring the
shrinkage condition. If the face of the concentrating shrinkage
cavity is smooth, and there is no visible shrinkage porosity in
depth, it will be shown as "O." It indicates the alloy has good
fluidity, strong feeding capacity and high casting compactability.
If the face of the concentrating shrinkage cavity is smooth but the
height of visible shrinkage porosity is less than 3 mm in depth, it
indicates castability is good, and will be shown as ".quadrature.."
If the face of the concentrating shrinkage cavity is not smooth and
the height of visible shrinkage porosity is more than 5 mm in
depth, it will be shown as "x." It indicates the alloy has bad
fluidity, weak feeding capacity and bad casting compactability.
Leakage will appear if water test is done.
[0054] Strip samples are used for measuring linear shrinkage rate
and bending angle of the alloy. If the bending angle is larger than
55.degree., it indicates it is excellent. If it is less than
40.degree., it indicates the plasticity of the alloy is too low and
it is poor. If it is larger than 100.degree. and even unpliant, it
indicates the plasticity of the alloy is good and is not beneficial
for cutting.
[0055] Circular samples are used for measuring shrinkage crack
resistance of the alloy. If there is no crack, it is rated as
excellent, and will be shown as "O." If there is a crack, it is
rated as poor, and will be shown as "x."
[0056] Spiral samples are used for measuring the melt fluid length
and evaluating the fluidity of the alloy.
[0057] All samples are hand poured and the pouring temperature is
1000.degree. C. Test results are shown in Table 2.
TABLE-US-00002 TABLE 2 Castability of the examples and comparative
alloys Examples 1 2 3 4 5 6 7 C36000 CuZn40Pb1Al0.6 Volume
shrinkage .largecircle. .largecircle. .largecircle. .quadrature.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. Linear shrinkage rate/% 1.5~1.9 1.9~2.1 1.7~1.9 Fluid
length/mm 400~420 420~440 440 430 Wall thickness of 2.5
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. circular samples/mm 3.0 .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. 3.5 .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
[0058] 2. Weldability
[0059] The pieces for welding are low pressure die castings and
CuZn37 brass pipes and are processed by brazing and flame heating
at a temperature of 350.about.400.degree. C. Weldability measuring
standards relate to whether cracks and porosity appear in the
welding seam and the heat affected zone. If there is no crack and
no porosity, it is qualified; otherwise it is unqualified.
[0060] Fifty (50) pieces are taken from the same type of faucet
body of each alloy. Test results are shown in Table 3.
TABLE-US-00003 TABLE 3 Weldability of the examples and comparative
alloys Examples 1 2 3 4 5 6 7 CuZn40Pb1Al0.6 After welding
Qualified Qualified Qualified Qualified After welding Small part
Qualified Qualified Qualified and polishing unqualified After
welding, Qualified Qualified Qualified Small part polishing and
unqualified ammonia- fumigating
[0061] 3. Cuttability
[0062] Several methods can be used for measuring the materials
cuttability. The common method is fixing the cutting process
parameters, measuring the cutting resistance, energy consumption or
spindle torque of the machine motor and so on, comparing with
free-cutting lead brass such as C36000 and finally obtaining the
relative cutting rate. Actually, good or poor materials'
cuttability is very closely related to the cutting process
parameters. In actual production, the cuttability of the material
is "good" or "poor," is always judged by the shape and size of the
chips, smooth degree of chip discharging and wear speed of the
tools. The cutting process parameters can be adjusted on the base
of different materials or different states of the same material for
getting successful cutting operation. The influence of the cutting
process parameters on chip shape is shown in Table 4. This shows
that feeding quantity has great influence on chip shape and size,
while linear speed has little influence on chip shape and size. If
feeding quantity is 0.2 mm/rev. and 0.3 mm/rev., the chip shape of
example alloy 1 is a thin sheet or thin tile. It indicates
cuttability is good, but not better than lead brass which contains
1 wt % Pb. Cutting depth is 4 mm.
TABLE-US-00004 TABLE 4 Influence of cutting process parameters on
chip shape Cutting Example alloy 1 CuZn40Pb1Al0.6 speed/m feeding
quantity/mm r.sup.-1 feeding quantity/mm r.sup.-1 min.sup.-1 0.1
0.2 0.3 0.1 0.2 0.3 40 See FIG. 1A See FIG. 1B See FIG. 1C See FIG.
1D See FIG. 1E See FIG. 1F 60 See FIG. 2A See FIG. 2B See FIG. 2C
See FIG. 2D See FIG. 2E See FIG. 2F 80 See FIG. 3A See FIG. 3B See
FIG. 3C See FIG. 3D See FIG. 3E See FIG. 3F 100 See FIG. 4A See
FIG. 4B See FIG. 4C See FIG. 4D See FIG. 4E See FIG. 4F
[0063] 4. Corrosion Resistance
[0064] All test samples are taken from low pressure die castings.
The results are shown in Table 5.
[0065] Dezincification corrosion testing is carried out according
to GB10119-1988 standard.
[0066] Stress corrosion testing is carried out according to
GS0481.1.013-2005 standard.
[0067] Salt-spray corrosion testing is carried out according to
ASTMB368-97 standard.
[0068] Release amount Value Q is measured according to
NSF/ANSI61-2007 standard.
TABLE-US-00005 TABLE 5 Corrosion Test results of the examples and
comparative alloy Examples 1 2 3 4 5 6 7 CuZn40Pb1Al0.6 Depth of
Average 0.24~0.32 0.27~0.38 0.25~0.33 0.24~0.31 0.23~0.28 0.30~0.35
dezincification value layer/mm Maximum 0.43~0.50 0.47~0.55
0.40~0.48 0.40~0.50 0.41~0.49 0.45~0.51 value Stress corrosion
Qualified Qualified Salt spray corrosion Qualified Qualified
Release amount Value Q/ Zn < 300, Bi < 50.0, Pb < 1.5, Sb
< 0.6, All qualified except .mu.g/L Tl < 0.2, Cd < 0.5, As
< 1.0, Hg < 0.2, All qualified for Pb > 5.0
[0069] 5. Mechanical Properties
[0070] Tensile test samples are processed by low pressure die
casting. Hardness test samples are processed by hand pouring. The
test results are shown in Table 6.
TABLE-US-00006 TABLE 6 Mechanical properties of the examples and
comparative alloy Examples 1 2 3 4 5 6 7 CuZn40Pb1Al0.6 Tensile 378
365 380 430 410 442 445 370 Strength/MPa Elongation Rate/ 7.5 9.5
11 16 14 16 17 10 % Hardness HRB 69 62 61 57 72 70 70 55
* * * * *