U.S. patent application number 14/127212 was filed with the patent office on 2014-04-24 for lead-free brass alloy for hot working.
This patent application is currently assigned to JOETSU BRONZ1 CORPORATION. The applicant listed for this patent is Tagayasu Hoshino, Tetsuya Matsuhashi, Katsuyuki Nakajima, Makoto Ueno, Hideki Yamamoto. Invention is credited to Tagayasu Hoshino, Tetsuya Matsuhashi, Katsuyuki Nakajima, Makoto Ueno, Hideki Yamamoto.
Application Number | 20140112821 14/127212 |
Document ID | / |
Family ID | 47789898 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140112821 |
Kind Code |
A1 |
Yamamoto; Hideki ; et
al. |
April 24, 2014 |
LEAD-FREE BRASS ALLOY FOR HOT WORKING
Abstract
Provided is a lead-free brass alloy for hot working provided
with good hot-working properties and mechanical characteristics. A
lead-free brass alloy for hot working, comprising: 28.0 to 35.0 wt
% zinc, 0.5 to 2.0 wt % silicon, 0.5 to 1.5 wt % tin, 0.5 to 1.5 wt
% bismuth, 0.10 wt % or less lead, and the remainder being copper
and unavoidable impurities, the zinc equivalent being in a range of
40.0 to 43.0, and the area ratio of the .kappa. phase after hot
working being 20% or less.
Inventors: |
Yamamoto; Hideki;
(Joetsu-shi, JP) ; Hoshino; Tagayasu; (Joetsu-shi,
JP) ; Nakajima; Katsuyuki; (Joetsu-shi, JP) ;
Ueno; Makoto; (Joetsu-shi, JP) ; Matsuhashi;
Tetsuya; (Joetsu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yamamoto; Hideki
Hoshino; Tagayasu
Nakajima; Katsuyuki
Ueno; Makoto
Matsuhashi; Tetsuya |
Joetsu-shi
Joetsu-shi
Joetsu-shi
Joetsu-shi
Joetsu-shi |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
JOETSU BRONZ1 CORPORATION
Joetsu-shi, Niigata
JP
|
Family ID: |
47789898 |
Appl. No.: |
14/127212 |
Filed: |
April 18, 2012 |
PCT Filed: |
April 18, 2012 |
PCT NO: |
PCT/JP2012/060466 |
371 Date: |
December 18, 2013 |
Current U.S.
Class: |
420/475 |
Current CPC
Class: |
C22F 1/00 20130101; C22C
9/04 20130101; C22F 1/08 20130101 |
Class at
Publication: |
420/475 |
International
Class: |
C22C 9/04 20060101
C22C009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2011 |
JP |
2011-286159 |
Claims
1. A lead-free brass alloy for hot working, characterized in
comprising: 28.0 to 35.0 wt % zinc, 0.5 to 2.0 wt % silicon, 0.5 to
1.5 wt % tin, 0.5 to 1.5 wt % bismuth, 0.10 wt % or less lead, and
the remainder being copper and unavoidable impurities, the zinc
equivalent being in a range of 40.0 to 43.0, and the area ratio of
the .kappa. phase after hot working being 20% or less.
2. The lead-free brass alloy for hot working according to claim 1,
characterized in that elongation is 10% or more.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lead-free brass alloy for
hot working, having excellent resistance to dezincification and
resistance to erosion and corrosion, and having good hot-working
properties and mechanical characteristics.
BACKGROUND ART
[0002] Bronze, brass, and other copper alloys have conventionally
been used in faucet parts for water supply, water contact parts for
general piping, and in various valves in order to make use the
excellent material characteristics of such alloys. These copper
alloys require good machinability for working a product, and
therefore lead has generally been included to thereby impart the
required machinability. For example, JIS H5120 CAC406, CAC407, and
other bronze alloys, and JIS H3250 C3604, C3771, and other brass
alloys having excellent machinability contain 1 to 6 wt % of
lead.
[0003] However, lead evaporates in the alloy melting and casting
process, elutes into drinking water when used as a water contact
part, and has other drawbacks. There is a deepening awareness that
lead is a toxic element that negatively affects the human body and
environmental sanitation, and the content of lead has been strictly
restricted in increasing fashion in recent years. Accordingly,
there is a need to develop a free-cutting copper alloy that does
not contain lead.
[0004] In view of the background described above, in silzin bronze
alloys, a Cu--Zn--Si alloy in which free-cutting is achieved by
adding silicon without the inclusion of lead has been proposed and
used (see Patent Documents 1 and 2). Additionally, there has been
proposed a Cu--Zn--Si--Sn alloy in which tin has been added in
order to enhance the corrosion resistance of a Cu--Zn--Si alloy
(see Patent Document 3). There have also been proposed a
Cu--Zn--Si--Bi alloy in which bismuth has been added in order to
further improve the machinability of a Cu--Zn--Si alloy (see Patent
Document 4), and a Cu--Zn--Si--Sn--Bi alloy (see Patent Document 5)
in which tin has been added to the Cu--Zn--Si--Bi alloy in order to
improve corrosion resistance. These alloys have excellent
mechanical characteristics and dezincification resistance, and
excellent machinability in the case that bismuth has been added,
and alloys in which Bi has not be added are provided with excellent
hot workability. In the case that bismuth is added to a Cu--Zn--Si
alloy, there is an additional advantage in that the alloy can be
used as scrap to be dissolved into raw materials.
PRIOR ART DOCUMENTS
Patent Documents
[0005] [Patent Document 1] Japanese Patent No. 3917304 [0006]
[Patent Document 2] Japanese Laid-open Patent Application No.
2001-64742 [0007] [Patent Document 3] Japanese Laid-open Patent
Application No. 2002-12927 [0008] [Patent Document 4] Japanese
Laid-open Patent Application No. 2009-7657 [0009] [Patent Document
5] Japanese Patent Application No. 2010-84231
DISCLOSURE OF THE INVENTION
Problems that the Invention is to Solve
[0010] The alloys disclosed in the above-noted documents can be
said to have the main object of removing lead toxicity. Therefore,
the most important issue in terms of performance is to maintain
free-cutting characteristics without the inclusion of lead, and to
a certain extent machinability has been ensured.
[0011] However, in the case that the alloy does not contain
bismuth, machinability is improved by the silicon compound, but the
improvement may be insufficient in some cases, and currently, a
certain amount of bismuth must be added in order to improve
machinability. Also, it is preferred the alloy contain bismuth from
the viewpoint of use as scrap.
[0012] However, a bismuth-containing lead-free brass alloy can be
hot worked in mold working in which there is little deformation,
but in the case of molding work with a considerable amount of
deformation, forge cracking or other defects readily occur unless
the addition amount of bismuth and the forging conditions are
rigorously controlled. It is known that hot forging a brass alloy
has different conditions in which cracking occurs in a product
depending on the working temperature. There are upper and lower
limits to the working temperature at which working can be performed
without cracks forming, and heating and forging must be carried out
in this temperature region (hereinafter referred to as working
temperature range). For example, the working temperature must be
increased for the alloy in Patent Document 5, which contains about
0.7 wt % of bismuth, and since the working temperature range is
very narrow, temperature management is difficult, and there is also
a problem in terms of the amount of energy used. Patent Document 3
describes an alloy in which it is effective to add silicon as the
element for improving hot forging characteristics, but in the
embodiments, there is no data provided in relation to the
hot-working characteristics in the case that bismuth has been
added. The only evaluation is that the working temperature is on
the single level of 750.degree. C., and the working temperature
range is unclear.
[0013] The inventors carried out studies and found that the working
temperature range becomes very narrow when bismuth is included in a
Cu--Zn--Si--Sn alloy. Therefore, problems readily occur in
operations because the forging conditions must be rigorously
controlled in order to subject this alloy to molding work that
involves a considerable amount of deformation. In other words,
broadening the working temperature range is a first issue and is
important in order to apply the excellent corrosion resistance and
machinability of this alloy to a large number of components.
[0014] Also, tin is added in order to increase dezincification and
erosion and corrosion resistance, and elongation of a
Cu--Zn--Si--Sn--Bi alloy is readily reduced. The .kappa. phase and
.gamma. phase of this alloy precipitate and, depending on the
precipitation conditions, the mechanical properties are readily
degraded. Furthermore, these precipitation conditions are readily
affected by the heat history or the like during manufacture, and it
is important to accurately ascertain and suitably control the
relationship between the configuration of the structure and the
mechanical properties. In other words, a second issue is
controlling the mechanical properties, more particularly, the
elongation of the Cu--Zn--Si--Sn--Bi alloy.
[0015] The present invention was devised in order to solve the
above-described problems, it being an object thereof to provide a
lead-free brass alloy for hot working provided with good
hot-working properties and mechanical characteristics.
Means for Solving the Problems
[0016] The main points of the present invention are described
below.
[0017] A first aspect of the present invention relates to a
lead-free brass alloy for hot working, characterized in comprising:
28.0 to 35.0 wt % zinc, 0.5 to 2.0 wt % silicon, 0.5 to 1.5 wt %
tin, 0.5 to 1.5 wt % bismuth, 0.10 wt % or less lead, and the
remainder being copper and unavoidable impurities, the zinc
equivalent being in a range of 40.0 to 43.0, and the area ratio of
the .kappa. phase after hot working being 20% or less.
[0018] The present invention also relates to the lead-free brass
alloy for hot working according to the first aspect, characterized
in that elongation is 10% or more.
Effects of the Invention
[0019] The present invention is configured in the manner described
above, and is therefore a lead-free brass alloy for hot working,
provided with good hot-working properties and mechanical
characteristics. In other words, adding 28.0 to 35.0 wt % zinc
makes it possible to obtain good hot-working properties. In similar
fashion to zinc, silicon is an essential element for obtaining good
hot-working properties and the addition of 0.5 to 2.0 wt % is
effective. Tin contributes to improvement in dezincification decay
and resistance to erosion and corrosion decay. Bismuth is added in
order to improve machinability. The zinc equivalent is determined
by the balance among zinc, silicon, and other elements, and is a
parameter for maintained a balance between hot-working properties
and mechanical characteristics in particular. A zinc equivalent of
40.0 to 43.0 simultaneously satisfies the two characteristics.
Also, the area ratio of the .kappa. phase after hot working is 20%
or less, whereby good mechanical characteristics are obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a description of the zinc equivalent;
[0021] FIG. 2 is a chart showing the chemical components of samples
used in the hot-working test;
[0022] FIG. 3 is a descriptive view showing the shape of the test
piece in the hot-working test;
[0023] FIG. 4 is a chart showing the forging test results;
[0024] FIG. 5 is a graph showing the relationship between the Si
addition amount and the working temperature range;
[0025] FIG. 6 is a graph showing the relationship between the Zn
equivalent and the working temperature range;
[0026] FIG. 7 is a chart showing the chemical components of samples
used in the tensile test;
[0027] FIG. 8 is a chart showing the test results of the tensile
test;
[0028] FIG. 9 is a graph showing the relationship between the Si
addition amount and the mechanical characteristics in a low Zn
equivalent;
[0029] FIG. 10 is a graph showing the relationship between the Si
addition amount and the mechanical characteristics in a high Zn
equivalent;
[0030] FIG. 11 is a chart showing the chemical components of
samples in which the relationship between the Si addition amount,
the area ratio of the .kappa. phase, and the elongation has been
studied;
[0031] FIG. 12 is a chart showing the relationship between the Si
addition amount, the area ratio of the .kappa. phase, and the
elongation;
[0032] FIG. 13 is a graph showing the relationship between the Si
addition amount and the area ratio of the .kappa. phase;
[0033] FIG. 14 is a graph showing the relationship between the area
ratio of the .kappa. phase and the elongation;
[0034] FIG. 15 is a chart showing the chemical components of
samples used in the erosion and corrosion test, and the
dezincification decay test;
[0035] FIG. 16 is a descriptive view showing the shape of the test
piece in the erosion and corrosion test;
[0036] FIG. 17 is a chart showing the test conditions;
[0037] FIG. 18 is a chart showing the test results;
[0038] FIG. 19 is a chart showing the test results of the
dezincification decay test;
[0039] FIG. 20 is a chart showing the chemical components of
samples used in the machinability test;
[0040] FIG. 21 is a chart showing the test conditions;
[0041] FIG. 22 is a chart showing the test results; and
[0042] FIG. 23 is a photograph showing an example of the
photographed microstructure.
BEST MODE FOR CARRYING OUT THE INVENTION
[0043] Preferred embodiments of the present invention are briefly
described below while indicating the effects of the present
invention.
[0044] In order to obtain good resistance to dezincification and
resistance to erosion and corrosion, and to provide good
hot-working properties and mechanical characteristics, the present
invention provides a lead-free brass alloy for hot working
comprising: 28.0 to 35.0 wt % zinc, 0.5 to 2.0 wt % silicon, 0.5 to
1.5 wt % tin, 0.5 to 1.5 wt % bismuth, 0.10 wt % or less lead, and
the remainder being copper and unavoidable impurities, wherein the
zinc equivalent is in a range of 40.0 to 43.0.
[0045] The component composition as described above in the present
invention, the reasons for specifying the mechanical
characteristics, and the effects of the present invention will be
briefly described below.
[0046] Zinc (Zn)
[0047] Zinc dissolves in the matrix of a Cu--Zn--Si copper alloy,
and has the effect of increasing mechanical strength. Zinc also
reduces the melting point of the alloy, increases the fluidity of
the molten alloy, and enhances casting characteristics. Zinc also
has the effect of improving hot working, and in order to obtain
these effects, zinc must be added in the amount of 28.0 wt % or
more due to the relationship between the later-described silicon
addition amount and the zinc equivalent.
[0048] However, when the amount of zinc exceeds 35.0 wt %, the
hot-working properties are conversely degraded due to the
relationship between the later-described silicon addition amount
and the zinc equivalent. Also, the mechanical characteristics of
the alloy are liable to be degraded due to precipitation of a hard
phase that is greater than necessary. Due to such reasons, the zinc
content is set to 28.0 to 35.0 wt %.
[0049] Silicon (Si)
[0050] Silicon works as a deoxidizer during dissolution, enhances
the fluidity of the molten alloy, and improves casting
characteristics. A portion dissolves in the matrix and improves
mechanical strength, and a portion works with zinc to cause the
emergence of a hard phase that functions as a chip breaker during
cutting work and improve machinability.
[0051] Furthermore, as a result of thoroughgoing research, the
present inventors discovered the following, which dramatically
improves the working temperature range (a value obtained by
subtracting the lower limit from the upper limit of the working
temperature in which hot forging can be carried out without the
occurrence of cracking) of a Cu--Zn--Sn--Si alloy in the case that
bismuth is included.
[0052] In the heating stage during hot working, bismuth has a
property of readily aggregating at the grain boundary, and this is
thought to be the cause of inhibiting hot-working properties.
However, the addition of a suitable amount of silicon prevents
bismuth aggregation and is effective in preventing forging cracks.
In order to obtain these effects, silicon must be added in the
amount of 0.5 wt % or more. When the content exceeds 2.0 wt %,
hot-working properties are degraded even when the zinc equivalent
has been kept at an optimal level, and the mechanical
characteristics of the alloy are liable to be degraded due to the
emergence of a hard phase that is greater than necessary. Due to
such reasons, the silicon content is set to 0.5 to 2.0 wt %.
[0053] Tin (Sn)
[0054] Tin is effective for enhancing dezincification resistance
and resistance to erosion and corrosion. Tin is particularly
effective in improving erosion and corrosion properties, and in
order to obtain these effects, tin must be added in the amount of
0.5 wt % or more. On the other hand, when the content exceeds 1.5
wt %, mechanical characteristics are liable to be degraded. Due to
such reasons, the tin content is set to 0.5 to 1.5 wt %.
[0055] Bismuth (Bi)
[0056] A bismuth content less than 0.5 wt % can be considered to
have little effect for improving machinability, but machinability
is improved in accordance with the addition amount by adding 0.5 wt
% or more. However, the addition of a large amount is not preferred
in that it causes degradation in hot-working properties. A large
amount not only causes degradation in hot-working properties, but
also causes degradation in the mechanical characteristics, hence
the upper limit is set to 1.5 wt %.
[0057] Lead (Pb)
[0058] The lead content is set to 0.10 wt % or less, and it is
thereby possible to essentially avoid evaporation in the
dissolution and casting processes of the alloy, as well as lead
poisoning in the human body and/or environmental hygiene due to
elution into drinking water or the like when the alloy is used as a
water contact component. Due to such reasons, the lead content is
limited to 0.10 wt % or less.
[0059] Copper (Cu)
[0060] Copper is an element that reduces sensitivity to
dezincification decay and improves corrosion resistance and
mechanical characteristics, but in the alloy of the present
invention, the copper content is determined as the remainder due to
the balance between the zinc content and silicon content. The
effective content is 59.0 to 71.0 wt %.
[0061] Zinc Equivalent
[0062] The zinc equivalent is an important parameter for
maintaining a broad working temperature range in the alloy of the
present invention. As described above, a suitable addition of
silicon makes it possible to maintain a broad working temperature
range, but control is insufficient using silicon alone, and using
the zinc equivalent computed by the balance between silicon, zinc,
and the like to achieve limited control makes it possible to more
reliably maintain a broad working temperature range. The present
inventors carried out research and found that setting the zinc
equivalent in the alloy of the present invention to 40.0 or more
provides a working temperature range that is broad enough to
satisfy industrial requirements. However, a zinc equivalent
exceeding 43.0 is liable to lead to degradation in the mechanical
characteristics. In view of this background, the zinc equivalent is
set to 40.0 to 43.0.
[0063] The zinc equivalent is obtained using the Guillet formula
(zinc equivalent=100.times.(B+.SIGMA.tq)/(A+B+.SIGMA.tq)), and the
zinc equivalent of Bi is calculated using a factor of 1 (see FIG.
1).
[0064] .kappa. Phase Quantitative Ratio or Heat Treatment
[0065] The addition of the elements described above and the use of
hot working makes it possible to demonstrate the excellent function
of the alloy of the present invention, but depending on the cooling
speed and/or the processing rate during hot working, elongation may
be slightly insufficient. In order to improve the elongation of the
alloy of the present invention, the metal structure must be
controlled, and setting the area ratio of the .kappa. phase in the
alloy of the present invention to 20% or less makes it possible to
ensure elongation. Therefore, the area ratio of the .kappa. phase
is set to 20% or less. The method for controlling the structure is
not particularly limited, and may be controlled using a hot-working
method, heat treatment, or the like.
Embodiments
[0066] Specific embodiments of the present invention will be
described below with reference to the drawings.
[0067] The alloy according to the present invention (the alloy of
the present invention) and a comparative alloy were used as samples
and tested in the manner described below.
[0068] 1) Hot-Working Test
[0069] The chemical components of the samples used in the
hot-working test are shown in FIG. 2. A molten alloy melted in a
Siliconit furnace for test dissolution and prepared with the
chemical components shown in FIG. 2 was cast in a mold having an
outside diameter of 88 mm and a length of 120 mm, and then machined
to an outside diameter of 78 mm and a length of 90 mm. Machined
billets were extruded to a diameter of 22 mm, and the resulting
rods were worked into a test piece shape such as that shown in FIG.
3. The working temperature was varied and these test pieces were
forged with a processing rate of 80%. As used herein, the
processing rate is calculated using the following formula.
Processing rate=100.times.(sample height prior to forging-sample
height after forging)/sample height prior to forging
[0070] The test pieces (samples) after forging were observed
macroscopically, the lower limit was subtracted from the upper
limit of the working temperature at which forging can be carried
out without the occurrence of cracking, and this was used to define
the working temperature range and make evaluations. The heating
time in all tests was 20 minutes. The working temperature range of
each sample is shown in FIGS. 4 to 6.
[0071] (a) Effectiveness of the Silicon Addition
[0072] The effectiveness of adding silicon to the alloy of the
present invention is shown in FIG. 5. In the case that silicon is
not added, the working temperature range is narrow, but it is
apparent that the working temperature range increases in
accompaniment with the addition of silicon. The effect of these
additions is to produce a satisfactory working temperature range
with the addition of 0.5 wt % or more. However, when the addition
amount exceeds 2.0 wt %, the working temperature range tends to be
conversely reduced, and it was found that an effective silicon
content is 0.5 to 2.0 wt %.
[0073] (b) Effectiveness of the Zinc Equivalent
[0074] Next, the effectiveness of the zinc equivalent is shown in
FIG. 6. It was found that the zinc equivalent must be 40.0 to 43.0
in order to adequately maintain the working temperature range in
the alloy of the present invention, and it was confirmed that the
zinc equivalent must be controlled, as appropriate, in accordance
with the effect of increasing the working temperature range by the
silicon addition described above.
[0075] 2) Tensile Test of the Hot-Working Material
[0076] The chemical components of the sample materials used in the
tensile test are shown in FIG. 7. A molten alloy was cast in a mold
having a diameter of 45 mm and a length of 100 mm, and was then
machined into billets having a diameter of 40 mm and a length of 75
mm. The billets were subsequently heated to 650 to 750.degree. C.
and extruded to a diameter of 10 mm, then machined into test pieces
in accordance with JIS Z2201 14A, and subjected to a tensile test
using a universal testing machine. The results are shown in FIGS. 8
to 10.
[0077] When the effect of the silicon addition amount is
considered, there is a noted tendency for the elongation to be
reduced in accordance with the silicon addition amount, and this is
particularly dramatically in the case that the zinc equivalent is
high. It is apparent that the tensile strength tends to be
temporarily reduced when the silicon content is near 1.0 wt % with
the zinc equivalent near 40.6, and when the silicon content is near
2.0 wt % with the zinc equivalent near 42.5, but thereafter the
tensile strength increases.
[0078] 3) Metal Structure and Mechanical Characteristics
[0079] The alloy of the present invention has excellent hot-working
properties as described above, and it is important to suitably
control the Si addition amount and the zinc equivalent. However,
elongation tends to be readily reduced when the zinc equivalent is
high, and controlling the structure also becomes an issue.
[0080] The alloy of the present invention mainly has .kappa.-phase
and .alpha.-phase constituent structures, and between these two,
the structure was observed with focus on the effect that the
quantitative ratio of the .kappa. phase has on the mechanical
characteristics. Five locations were photographed using an optical
microscope to obtain images at 500.times. magnification using the
samples used in the tensile test described above. The quantitative
ratio of the .kappa. phase was measured using image processing
software (an example of the photographs taken is shown in FIG. 23).
These results are shown in FIGS. 11 to 14. The inventors found the
following facts from these structural observations. The elongation
of the alloy of the present invention was found to have a very
strong correlation with the area ratio of the .kappa. phase, and
when elongation is to be increased, the area ratio of the .kappa.
phase must be kept low.
[0081] The relationship between the area ratio of the .kappa. phase
and the silicon addition amount increases in accordance with the
silicon addition amount (see FIG. 13). In terms of the relationship
between the area ratio of the .kappa. phase and the silicon
addition amount, elongation is 10% or more when the area ratio of
the .kappa. phase is 20% or less (see FIG. 14). Therefore, the area
ratio of the .kappa. phase in the alloy of the present invention
must be 20% or less.
[0082] 4) Corrosion Decay Test
[0083] (a) Erosion and Corrosion Test
[0084] The chemical components of the sample materials used in the
erosion and corrosion test are shown in FIG. 15. A molten alloy
melted in a Siliconit furnace for test dissolution and prepared
with the chemical components shown in FIG. 15 was cast in a mold
having a diameter of 40 mm and a length of 100 mm, and was then
worked into a test piece shape such as that shown in FIG. 16.
Testing was carried out with the test conditions of FIG. 17 using
these test pieces. The test results are shown in FIG. 18. It was
found from these results that the alloy of the present invention
was slightly inferior to CAC406, but was considerably better than
free-cutting brass.
[0085] (b) Dezincification Decay Test
[0086] The same samples as those used in the erosion and corrosion
test were used. The test was carried out in accordance with ISO
6509. The test results are shown in FIG. 19. Good results were
obtained with the alloy of the present invention in that the
maximum decay depth was 100 .mu.m or less for all samples.
[0087] 5) Machinability Test
[0088] The chemical components of the sample materials used in the
erosion and corrosion test are shown in FIG. 20. A molten alloy
melted in a Siliconit furnace for test dissolution and prepared
with the chemical components shown in FIG. 20 was cast in a JIS
H5120 E mold, the outside diameter of the test pieces was worked
using the cutting conditions shown in FIG. 21, and the cutting
resistance of the test pieces was measured. The test results are
shown in FIG. 22. In comparison with lead-containing bronze and
lead-containing brass, the alloy of the present invention has
higher resistance, but is on the same level as that of lead-free
bronze.
[0089] In view of the above, it was confirmed that the lead-free
brass alloy for hot working has good hot-working properties and
mechanical characteristics, the lead-free brass alloy for hot
working, comprising: 28.0 to 35.0 wt % zinc, 0.5 to 2.0 wt %
silicon, 0.5 to 1.5 wt % tin, 0.5 to 1.5 wt % bismuth, 0.10 wt % or
less lead, and the remainder being copper and unavoidable
impurities, wherein the zinc equivalent is in a range of 40.0 to
43.0.
* * * * *