U.S. patent application number 09/737079 was filed with the patent office on 2002-08-15 for copper base alloy that contains intermetallic constituents rich in calcium and/or magnesium.
Invention is credited to Lawrence, Benjamin L..
Application Number | 20020110478 09/737079 |
Document ID | / |
Family ID | 27389817 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020110478 |
Kind Code |
A1 |
Lawrence, Benjamin L. |
August 15, 2002 |
Copper base alloy that contains intermetallic constituents rich in
calcium and/or magnesium
Abstract
An alloy is provided containing by weight about 1 to 7% bismuth,
up to 45% zinc, up to 20% tin, up to 30% nickel, up to 3% selenium,
up to 2% aluminum, up to 2% antimony, up to 1% iron, up to 1% lead,
up to 2% phosphorus, up to 2% carbon, and calcium and magnesium,
singularly or in combination, from 0.02 to 2.0%, and the remainder
copper and incidental impurities. The method for producing such an
alloy is also provided.
Inventors: |
Lawrence, Benjamin L.;
(Elkhart, IN) |
Correspondence
Address: |
PRICE HENEVELD COOPER DEWITT & LITTON
695 KENMOOR, S.E.
P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Family ID: |
27389817 |
Appl. No.: |
09/737079 |
Filed: |
December 13, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60219563 |
Jul 20, 2000 |
|
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|
60170411 |
Dec 13, 1999 |
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Current U.S.
Class: |
420/476 ;
420/494; 420/499 |
Current CPC
Class: |
C22C 9/00 20130101; C22C
9/04 20130101; C22C 1/02 20130101 |
Class at
Publication: |
420/476 ;
420/494; 420/499 |
International
Class: |
C22C 009/00; C22C
009/04 |
Claims
The invention claimed is:
1. An alloy comprising: bismuth in an amount of about 1% to about
7% by weight of the alloy; zinc in an amount of 0 to about 45% by
weight of the alloy; tin in an amount of 0 to about 20% by weight
of the alloy; calcium and magnesium, in an amount combined from
about 0.02% to about 2.0% by weight of the alloy; and copper in an
amount of 27% to about 98.8% by weight of the alloy.
2. The alloy defined in claim 1, further including antimony.
3. The alloy defined in claim 1, further including lead.
4. The alloy defined in claim 1, where said bismuth, calcium, and
magnesium are melt added to the remaining components of the
alloy.
5. A method for producing a pre-alloy comprising the steps of: (a)
melting and superheating bismuth; (b) placing granular calcium
carbide on top of the molten bismuth; (c) replenishing the calcium
carbide until saturation is reached; and (d) plunging magnesium
into the bismuth melt.
6. The method defined in claim 5, wherein said bismuth is melted
and superheated at a temperature of about 2000.degree. F.
7. A plumbing component made of an alloy comprising: bismuth in an
amount of about 1% to about 7% by weight of the alloy; zinc in an
amount of 0 to about 45% by weight of the alloy; tin in an amount
of 0 to about 20% by weight of the alloy; calcium and magnesium, in
an amount combined from about 0.01% to about 2.0% by weight of the
alloy; and copper in an amount of 27% to about 98.9% by weight of
the alloy.
8. The plumbing component of claim 7, further including
antimony.
9. The plumbing component of claim 7, further including lead.
10. The plumbing component of claim 7, where said bismuth, calcium,
and magnesium are melt added to the remaining components of the
alloy.
11. A method of producing a no-lead alloy comprising the steps of:
(a) melting and superheating bismuth; (b) placing granular calcium
carbide on top of the molten bismuth; (c) replenishing the calcium
carbide until saturation is reached; (d) plunging magnesium into
the bismuth melt to form a pre-alloy; (e) melting copper; (f)
adding zinc to the copper; and (g) adding said pre-alloy to said
melted copper and zinc.
12. The method defined in claim 11, further including the step of
adding tin to said melted copper before the addition of zinc.
13. The method defined in claim 11, wherein said bismuth is melted
and superheated at about 2000.degree. F.
14. The method defined in claim 13, wherein said bismuth is melted
in an electric coreless furnace.
15. The method defined in claim 11, further including the step of
adding antimony to the alloy.
16. A no-lead alloy comprising: about 68% copper by weight of the
alloy; about 28% zinc by weight of the alloy; about 2% bismuth by
weight of the alloy; about 1% tin by weight of the alloy; about
0.5% magnesium by weight of the alloy; and about 0.5% calcium by
weight of the alloy.
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. provisional application Serial No. 60/219,563
entitled COPPER BASE ALLOY THAT CONTAINS INTERMETALLIC CONSTITUENTS
RICH IN CALCIUM AND/OR MAGNESIUM and to U.S. Provisional
Application Serial No. 60/170,411 entitled LOW AND NO LEAD BRASS
CONTAINING CALCIUM CARBIDE, the entire disclosures of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a new copper based alloy intended
for, but not limited to, use in the production of components
suitable for potable water plumbing service.
[0003] Brass plumbing components are typically machined, forged or
cast to shape and traditionally contain from 1 to 9% by weight of
lead. The presence of lead in these components enhances machining
and improves pressure tightness. Yet, these benefits are rapidly
being outweighed by concern over the potential toxicological
effects of human exposure to lead. Human exposure is reportedly
linked directly to lead leaching from such plumbing components into
drinking water. In addition, hazards may arise during manufacturing
of leaded brass from exposure to airborne lead particulate released
by melting, machining, and cleaning operations.
[0004] Bismuth substituted for lead, alone or in combination with
other elements, provides the basis for a majority of the
"lead-free" alloy developmental work to date. Both bismuth and lead
have relatively low melting points and limited solid solubility
with respect to copper based alloys. Upon solidification of these
alloys, these characteristics promote a segregation of each element
into isolated pockets throughout the alloy matrix. These segregated
pools act as chip-breakers during machining and fill the
micro-porosity voids left in certain cast alloys by solidification
shrinkage. It is preferable that these discrete pools be uniformly
distributed throughout the matrix. In general, replacing lead with
bismuth does not benefit the mechanical properties of brass.
Elongation of bismuth brasses at ambient temperature is lower than
that of leaded brass. Also, bismuth brasses tend to lose mechanical
strength, undergo hot-shortness, at lower elevated temperature than
leaded brasses due to lower melting point. Other alloys that have
been tried as a replacement for leaded brass contain particles of
graphite, thermally stable dispersoids, or inter-metallic
compounds.
[0005] In recent years, a preferred form and distribution of
bismuth within "no-lead" brasses has been demonstrated by the use
of grain refining techniques. These techniques include the use of
grain refining melt additives including boron, phosphorus, and rare
earth elements such as lanthanum and cerium. As noted, these
additives do not change the nature of the bismuth segregate but
rather only affect its size and distribution.
[0006] Yet another approach to modification of grain microstructure
within "no-lead" bismuth brasses requires there to be an addition
of selenium to the alloy. Selenium is introduced to the melt as
selenide particles, which are claimed to have a synergistic effect
on the bismuth. It is claimed that these particles improve
free-machining characteristics by adding an additional component to
interrupt and break continuously formed machine chips.
[0007] U.S. Pat. No. 4,879,094 is directed to an alloy for the
manufacture of cast components intended for potable water supply
installations. This alloy is comprised in weight percent of 1.5 to
7% bismuth by weight, 5 to 15% zinc, 1 to 12% tin, with the
balance, excepting impurities and minor additives, being
copper.
[0008] U.S. Pat. No. 5,137,685 discloses an alpha-beta (yellow)
brass containing bismuth in place of lead. The brass is comprised
of about 30 to 58 wt. % zinc, up to 5 wt. % bismuth, and the
balance copper. In one embodiment of the invention, the alloy
contains sulfur, tellurium, and selenium, in the respective forms
of sulfides, tellurides, and selenides, as combined with zirconium,
manganese, iron, nickel or mischmetal (rare earth elements).
Another embodiment described calls for the use of bismuth
spheroidizing agents, such as phosphorous, antimony, and tin.
[0009] A further "lead-free" brass is disclosed in U.S. Pat. No.
5,330,712. That patent describes an alloy that contains mischmetal
as a grain refiner to more uniformly distribute segregated bismuth
particles.
[0010] U.S. Pat. No. 5,879,477, describes brasses used in plumbing
applications that contain either reduced lead alloys or bismuth
yellow brasses. These brasses contain 55 to 70 wt. % copper, 30 to
45 wt. % zinc, and 0.2 to 1.5 wt. % bismuth and are rendered
dezincification resistant by use of aluminum and antimony additions
or grain refiners including boron, indium, silver, titanium,
cobalt, zirconium, niobium, tantalum, molybdenum, and vanadium.
[0011] Dispersed particle brasses are a recent approach to
"lead-free" brass, as disclosed in U.S. Pat. No. 5,766,377. These
brasses contain no lead or bismuth to enhance machining through
dispersion of either high-melt point or intermetallic compound
particles. This patent describes a group of copper-zinc alloys that
contain one or more of the thermally stable dispersoids:
Cr.sub.2Ta, Dy.sub.2O.sub.3, Er.sub.2O.sub.3, MoB, Mo.sub.2C, NbC,
Nd.sub.2O.sub.3, Sm.sub.2O.sub.3, WS.sub.2, WSi.sub.2,
Yb.sub.2O.sub.3, and ZrC, or the inter-metallic compounds:
CeAl.sub.2, LaAl.sub.2, La.sub.3Sb, LaSb, La.sub.2Sb, Ni.sub.3Al,
NiAl, and Ni.sub.3Nb.
[0012] U.S. Pat. No. 4,859,417 discloses the presence of
intermetallic compounds of CaP, CuMg, and CuP. The primary
composition of the alloy includes the following elements, in
percent by weight: magnesium 0.05 to 1.0%, phosphorus 0.03 to 0.9%,
and calcium 0.002 and 0.04%. The remainder of the alloy is copper
with other alloying elements such as tin, zirconium, manganese, and
lithium.
[0013] U.S. Pat. No. 5,624,506 discloses a copper alloy in which
calcium is added to combine with and separate out sulfur from the
melt. The amount of calcium added to the molten bath is between
0.0001 and 0.01%, by weight.
[0014] European Patent Application No. 93301814.5 focuses on
combining bismuth and mischmetal in brass. This application
explains the formation and non-formation of certain intermetallic
compounds with copper and zinc. Calcium is identified as having
potential for intermetallic compound formation with these
elements.
[0015] U.S. Pat. No. 5,026,433 discloses grain refinement of a
copper based alloy using calcium.
[0016] Yet another approach to "lead-free" brass combines
relatively high levels of selenium and bismuth. The ratio of
selenium to bismuth is generally represented to be 1 to 2 parts.
These alloys are claimed to impart free-machining characteristics
by forming chip-breaking selenide particles.
SUMMARY OF THE INVENTION
[0017] The current invention presents an alloy that uses target
compositions to achieve enhanced machinability and/or improved
pressure tightness for lead-free plumbing components. The invention
utilizes intermediate compounds to modify the form and distribution
of the segregate bismuth phase.
[0018] One aspect of the present invention is an alloy comprising
bismuth in an amount of about 1.0% to about 7.0% by weight of the
alloy, zinc in an amount of 0.0% to about 45.0% by weight of the
alloy, tin in an amount of 0.0% to about 20.0% by weight of the
alloy, calcium and magnesium in an amount combined from about 0.02%
to about 2.0% by weight of the alloy, and copper in an amount of
27.0% to about 98.8% by weight of the alloy.
[0019] Another aspect of the present invention is a method for
producing a pre-alloy comprising the steps of melting and
superheating bismuth, placing granular calcium carbide on top of
the molten bismuth, replenishing the calcium carbide until
saturation is reached, and plunging magnesium into the bismuth
melt.
[0020] Yet another aspect of the present invention is a plumbing
component made of an alloy comprising bismuth in an amount of about
1.0% to about 7.0% by weight of the alloy, zinc in an amount of
0.0% to about 45.0% by weight of the alloy, tin in an amount of
0.0% to about 20.0% by weight of the alloy, calcium and magnesium
in an amount combined from about 0.02% to about 2.0% by weight of
the alloy, and copper in an amount of 27.0% to about 98.8% by
weight of the alloy.
[0021] Still another aspect of the present invention is a no-lead
alloy comprising about 68% copper by weight of the alloy, about 28%
zinc by weight of the alloy, about 2% bismuth by weight of the
alloy, about 1% tin by weight of the alloy, about 0.5% magnesium by
weight of the alloy, and about 0.5% calcium by weight of the
alloy.
[0022] These and other features, advantages and objects of the
present invention will be further understood and appreciated by
those skilled in the art by reference to the following
specification, claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a high magnification SEM view of the distribution
of Mg--Bi, Ca--Mg--Bi, and Bi agglomeration particles;
[0024] FIG. 2 is a high magnification SEM view of bismuth rich
intermetallic particles;
[0025] FIG. 3 is a high magnification SEM view of bismuth rich
intermetallic particles;
[0026] FIG. 4 is a microscopic photograph of non-treated yellow
brass with bismuth therein;
[0027] FIG. 5 is a microscopic photograph of calcium carbide
treated yellow brass;
[0028] FIG. 6 is a microscopic photograph of pure bismuth;
[0029] FIG. 7 is a microscopic photograph of calcium;
[0030] FIG. 8 is a microscopic photograph of calcium;
[0031] FIG. 9 is a microscopic photograph of magnesium rich bismuth
saturated with calcium;
[0032] FIG. 10 is a microscopic photograph of magnesium rich
bismuth saturated with calcium;
[0033] FIG. 11 is a microscopic photograph of the alloy of the
present invention;
[0034] FIG. 12 is a microscopic photograph of the alloy of the
present invention; and
[0035] FIG. 13 is an elevational view of a plumbing fitting elbow
that can be made from the alloy of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The present invention is an alloy containing by weight about
1 to 7% bismuth, up to 45% zinc, up to 20% tin, up to 30% nickel,
up to 3% selenium, up to 2% aluminum, up to 2% antimony, up to 1%
iron, up to 1% lead, up to 2% phosphorus, up to 2% carbon, and
calcium and magnesium, singularly or in combination, from 0.02% to
2.0%, and the remainder copper and incidental impurities.
[0037] The basis for this invention is a recognition that it is
beneficial to add to (or create within) copper based alloys a
uniform distribution of discrete intermetallic compounds. These
compounds are primarily intended to influence the distribution and
required amount of specific non-soluble segregate phases within an
alloy. This invention utilizes intermetallic compounds of
magnesium-bismuth, magnesium-calcium-bismuth, and calcium-carbon as
modifiers of the segregate phase of bismuth within "no-lead"
brass.
[0038] One facet of this invention relates to the creation of
nucleation sites within bismuth yellow brass. These nucleation
sites change the solidification pattern (i.e. dendrite structure)
of the freezing alloy, causing grain refinement and ultimately a
redistribution of the low-melt point bismuth phase. In order to
achieve such nucleation, discrete particles must be introduced into
the molten alloy and, upon cooling, be held within the matrix
beyond solidification. The nucleating particles must remain wholly
or partially insoluble in the alloy and be uniformly distributed
throughout the matrix. It is a further advantage to have these
particles act in unison with the bismuth phase to improve the
alloy. In particular, the segregation of any such constituents
within a bismuth brass would preferably, and does in practice,
reduce the amount of bismuth required to achieve good machining
properties.
[0039] Selection of the appropriate intermetallic compounds for
this invention is based on the following considerations:
[0040] The tendency for compounds to remain active within the
molten bath and not be consumed or removed during melting.
[0041] The potential for compounds to interact with or influence
the bismuth phase.
[0042] The proven compatibility of compounds and the chosen base
copper alloy.
[0043] One aspect of the current invention provides to the copper
based alloy an intermetallic compound of calcium carbide powder as
a late melt addition. The calcium component of the intermetallic
compound assists in modification of the bismuth phase of the alloy.
Calcium is a known grain refiner and increases fluidity of certain
copper based alloys. Calcium plays a role, singularly or in
combination with other elements, in deoxidizing copper alloys. For
example, calcium boride is used to deoxidize certain copper alloys.
In this process, a calcium boron compound is plunged into the
molten bath and reacts with the oxygen to form a B.sub.2O.sub.2
slag.
[0044] The second component of the intermetallic compound is
carbon. It provides a non-soluble particle that further enhances
grain refinement by introducing additional nucleation sites. Carbon
as an individual element is non-wetting and less dense in
relationship to a copper based alloy and naturally tends to float
out of the melt due to relative specific gravity differences.
Calcium presents itself as a wetting agent that inhibits the
flotation of the combined carbon from the liquid metal. Thus, the
non-soluble carbon tends to remain more uniformly distributed
throughout the melt providing nucleation sites for grain refinement
and improved bismuth distribution.
[0045] It was discovered that an addition to brass of a relatively
small amount of calcium carbide, less than 0.1%, into the furnace
melt provided no appreciable modification to the bismuth phase.
Calcium carbide was apparently largely being given up as a slag. It
was demonstrated that a change in dendrite spacing and
correspondingly a more uniform distribution of segregate bismuth
pools was possible with the late addition of calcium carbide. (See
FIGS. 4 and 5.)
[0046] The intent was to create a separate intermetallic compound,
combined with or largely replacing the segregate bismuth phase of
"no-lead" brass. The investigative work was expanded to include
consideration of the possibility of forming intermetallic compounds
containing magnesium, phosphorus and/or calcium.
[0047] Phosphorus was selected because of its demonstrated ability
to refine grain structure and form intermetallic compounds within
copper based alloys. The late addition of phosphorus to these
alloys did not change the form and distribution of the bismuth
phase, most notably through spheroidizing and grain refinement.
Nevertheless, this modification did not include the creation of a
substantive intermetallic compound within the bismuth phase itself.
In fact, the addition of phosphorus to cast yellow brass alloys
containing by weight 2% bismuth, 0.5% magnesium, and 0.5% calcium
resulted in high scrap due to entrapped inclusions and
porosity.
[0048] The addition of magnesium to a series of yellow brass alloys
containing bismuth and calcium achieved the intended outcome sought
by this invention, development of intermetallic compounds of
magnesium-bismuth and magnesium-calcium-bismuth. (See FIGS. 1, 2,
and 3.) Magnesium and calcium were both separately added to the
alloy melt. These elements segregated out of the alloy matrix upon
cooling along with the bismuth phase.
[0049] A more preferred technique for producing this invention
calls for the melt addition of prepared additive mixtures
containing target percentages of bismuth, calcium, carbon, and
magnesium.
[0050] The following examples illustrate the invention.
EXAMPLE 1
[0051] A "no-lead" version of an alloy, analogous to C85400 leaded
yellow brass, contains the composition given in Table 1.
1TABLE 1 "No-Lead" Bismuth Yellow Brass with Calcium and Magnesium
Overall Weight Percent Component Target Actual Copper about 68
Balance Zinc about 28 27.62 Bismuth about 2 2.12 Tin about 1 1.02
Magnesium about 0.5 0.32 Calcium about 0.5 0.64
[0052] The alloy presented in Example 1 was selected from a series
of casting trials investigating the effects of variation in
chemical composition and foundry practice. The alloy of Table 1 was
enriched with calcium by placing and maintaining a granular calcium
carbide cover layer on the brass melt. Calcium was visibly taken up
by the molten bath. The cover was replenished until the bath
appeared to reach a level of calcium saturation; that is, the cover
remained intact without further addition. Magnesium was plunged
into the melt batch directly prior to pouring.
[0053] After magnesium treatment, the molten brass developed a
somewhat stringy magnesium oxide skin. The pouring temperature of
the alloy did not change appreciably from that expected for a
comparable traditional leaded brass.
[0054] Sample plumbing components were cast in bonded sand molds
without modification of the existing pressurized gating system used
for leaded brass. An example of such a plumbing component is shown
in FIG. 13. The castings poured from this alloy were machined
without encountering any difficulty.
[0055] Microstructure evaluation of the alloy of Example 1 revealed
intermetallic compounds combined with the expected bismuth
segregate. These combined agglomerations were well distributed
throughout the matrix as shown in the high magnification SEM view
of FIG. 1. Separate constituents of individual agglomeration sites
are shown under higher magnification in FIGS. 2 and 3. The
agglomeration phase contains three distinct constituents that can
be distinguished as follows:
[0056] Constituent 1--White Irregular Shaped Bismuth-Rich Phase
[0057] Constituent 2--Grayish Segregate of Mg--Bi--Cu
[0058] Constituent 3--White Rounded Segregate of Ca--Mg--Bi--Cu
[0059] Semiquantitative EDX elemental analysis of the individual
constituents is provided in Table 2.
2TABLE 2 Bi-Rich Pool Constituent Composition Weight Percent
Element Per Constituent Constituent Mg Ca Bi Zn Sn Cu 1 0.02 0.14
95.42 0.00 0.00 Balance 2 5.46 0.00 75.39 0.00 0.00 Balance 3 3.97
3.87 88.76 0.00 0.00 Balance
[0060] The tensile strength of the alloy was checked using machined
test bars with an average ultimate tensile strength (UTS) of 36,000
pounds per inch.sup.2 and elongation of 40%. This compares
favorably with the typical UTS of 34,000 pounds per inch.sup.2 and
35% elongation for the leaded C85400.
[0061] It was originally thought that corrosion resistance might be
adversely affected by introducing calcium and/or magnesium into
certain brasses. A series of samples, including the Example 1
alloy, were subjected to 24-hour copper chloride exposure corrosion
testing. The exemplar alloy was compared with a C85400 yellow brass
tested in a like manner. The invention alloy compared favorably
with the standard yellow brass with only a third of the
dezincification corrosion loss.
EXAMPLE 2
[0062] This example is another embodiment of the invention with
chemical composition by weight (of the alloy) of 26.76% zinc, 3.20%
bismuth, 1.23% tin, 0.65% nickel, 0.083% antimony, 0.098% aluminum,
0.1% calcium, and 0.07% carbon. This example demonstrates the base
technique used for bismuth phase modification and redistribution by
the late melt addition of calcium carbide powder. (See FIGS. 4 and
5.) It is intended that magnesium and/or calcium be added in
varying percentages to this late melt addition to achieve
intermetallic phase segregation.
EXAMPLE 3
[0063] This example is from foundry trials that were conducted on
several preferred embodiments of this invention, and alpha-beta
brass (DZR yellow brass) was selected based on the dual requirement
of the alloy for grain refinement in regards to provision of a
uniform distribution of bismuth and the need for enhancement of DZ
resistance. The chemical composition of this alloy is as
follows:
3 26.76% Zinc 3.20% Bismuth 1.23% Tin 0.65% Nickel 0.083% Antimony
0.098% Aluminum 0.1% Calcium 0.07% Carbon
[0064] where all percentages are weight percentages based on the
total weight of the alloy.
EXAMPLE 4
[0065] Another run where items were cast using a
bismuth/calcium/magnesium alloy addition had the following
composition:
4 28.51% zinc 1.68% bismuth 1.04% tin 0.005% calcium, and 0.015%
magnesium
[0066] A weight percent target of 2.20% of the melt bath was used
for the bismuth-rich additive. This additive contained 73.40%
bismuth, 0.95% calcium and 25.65% magnesium. After melting in the
additive, the furnace melt was held at a temperature greater than
2100.degree. F. for nearly three hours. The magnesium content was
reduced considerably by this extended holding at temperature;
however, the calcium content remained reasonably stable. This
demonstrated retention of calcium confirmed previous study
findings. The castings produced by this demonstration were
machined, assembled and pressure tested without difficulty.
[0067] The addition of calcium to the bismuth provides an alloy
with a distinct segregate pattern of calcium. The microstructure of
pure bismuth is shown in FIG. 6. In contrast, the sharp acicular
form of the calcium segregate is depicted in FIGS. 7 and 8. The
further addition of magnesium to bismuth saturated with calcium
provides a microstructure as shown in FIGS. 9 and 10. Magnesium is
revealed as a dark component within the acicular calcium form.
FIGS. 11 and 12 show the microstructure of the final copper base
alloy containing 2% by weight of the bismuth/calcium/magnesium
additive. This alloy also contains about 38% zinc and about 1% tin
by weight with the balance being copper. It is contemplated that
the bismuth alloy may include other elements such as antimony,
lead, and tin.
[0068] The following process is used to create a bismuth/calcium or
bismuth/calcium/magnesium pre-alloy. Bismuth is melted and
superheated with an electric coreless furnace to about
2,000.degree. F. Granular calcium carbide is then placed on top of
the molten bismuth bath as a cover material. The calcium carbide
cover is replenished to make up for any loss. By doing this,
calcium is taken into the melt and carbon is released as fumes. The
calcium carbide cover is replenished until a point of saturation is
reached when the cover remains largely intact. After the calcium
carbide cover is maintained without further additions, a
predetermined amount of magnesium is plunged into the alloy. To
create the no-lead brass alloy, copper is melted in an induction
furnace, tin is optionally added, and then zinc is added. The
pre-made bismuth/calcium/magnesium or bismuth/calcium alloy is then
added to form the alloy. Other components such as antimony,
selenium, aluminum, and phosphorus can be added, as desired.
[0069] The above description is considered that of the preferred
embodiments only. Modifications of the invention will occur to
those skilled in the art and to those who make or use the
invention.
* * * * *