ANTIMONY-MODIFIED LOW-LEAD COPPER ALLOY
Alloys and methods for forming alloys of copper, including red brass, and yellow brass, having sulfur and antimony.
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This application claims priority from U.S. Provisional Patent Application 61/642,260 filed May 3, 2012 which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION
Current plumbing materials are typically made from lead containing copper alloys. One standard brass alloy formulation is referred to in the art as C84400 or the “81,3,7,9” alloy (consisting of 81% copper, 3% tin, 7% lead, and 9% zinc) (hereinafter the “81 alloy”). While there has been a need, due to health and environmental issues [as dictated, in part, by the U.S. Environmental Protection Agency (EPA) on maximum lead content in copper alloys for drinking water applications] and also for cost reasons, to reduce lead contained in plumbing fitting, the presence of lead has continued to be necessary to achieve the desired properties of the alloy. For example, the presence of lead in a brass alloy provides for desirable mechanical characteristics and to assist in machining and finishing the casting. Simple removal of lead or reduction below certain levels substantially degrades the machinability as well as the structural integrity of the casting and is not practicable.
Removal or reduction of lead from brass alloys has been attempted previously. Such previous attempts in the art of substituting other elements in place of lead has resulted in major machining and finishing issues in the manufacturing process, which includes primary casting, primary machining, secondary machining, polishing, plating, and mechanical assembly.
Several low or no lead formulations have previously been described. See, for example, products sold under the trade names SeBiLOY® or EnviroBrass®, Federalloy®, Biwalite™, Eco Brass®, Bismuth Red brass (C89833), and Bismuth Bronze (C89836), as well as U.S. Pat. Nos. 7,056,396 and 6,413,330.
However, there is a need for a low-lead alloy casting solution providing a low-cost alloy with similar properties to current copper/lead alloys without degradation of mechanical properties or chemical properties, as well as significant disruption to the manufacturing process because of lead substitution in the material causing cutting tool and finishing problems.SUMMARY OF THE INVENTION
One embodiment of the invention relates to a composition of matter comprising 82% to about 89% copper, about 0.01% to about 0.65% sulfur, greater than 0.1 to about 1.5% antimony, about 2.0% to about 4.0% tin, less than about 0.09% lead, about 5.0% to about 14.0% zinc, and about 0.5% to about 2.0% nickel.
In one embodiment of the invention, the composition comprises 86% to about 89% copper, about 0.01% to about 0.65% sulfur, greater than 0.1 to about 1.5% antimony, about 7.5% to about 8.5% tin, less than about 0.09% lead, about 1.0% to about 5.0% zinc, and about 1.0%% nickel.
In one embodiment of the invention, the composition comprises 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0.1 to about 1.5% antimony, about 1.5% tin, less than about 0.09% lead, about 31.0% to about 41.0% zinc, and about 1.5% nickel.
In one embodiment of the invention, the composition comprises 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0.1 to about 1.5% antimony, less than about 0.09% lead, and about 31.0% to about 41.0% zinc.
Another embodiment of the invention relates to a method for adding sulfur to a brass alloy. A base ingot is heated to a temperature of about 2,100 degrees Fahrenheit to form a melt. In one embodiment, Zn, Ni, and Sn are added to the copper the melt at about 2,124 F.°, stibnite is added at about 2,164 F.°, and phosphorous is added at about 2,164 F.°. Stibnite wrapped in copper foil is added and the temperature maintained at about 2164 F. In one embodiment, phosphorus deoxidation is also done at this temperature. Heating of the melt is ceased and additives, including tin, zinc, nickel, and carbon, are added at about 2124 F. At least a partial amount of slag is skimmed from the melt. Temperature of the melt is maintained at 2100 F. Slag is removed from the melt.
Additional features, advantages, and embodiments of the present disclosure may be set forth from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the present disclosure and the following detailed description are exemplary and intended to provide further explanation without further limiting the scope of the present disclosure claimed.
The foregoing and other objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.
Brass alloys typically utilize lead as a chip breaker and to generally improve the qualities desirable in brass alloys for use in a wide range of situations, including plumbing. The use of sulfides as a replacement for lead has been previously taught in U.S. patent application Ser. No. 13/317,785, incorporated by reference herein.
It has been observed that the addition of elemental sulfur in place of lead in a “standard” brass alloy may not result in the sulfur becoming integrated into the final alloy, but rather loss to the dross. As further described below, the brass alloys of the present invention utilize antimony for improved properties. In one embodiment, of the present invention a sulfur containing mineral, stibnite, is utilized as a source of sulfur and to provide antimony to the alloy.
Stibnite is a naturally occurring sulfide mineral in the form of Sb2S3. Stibnite typically contains 26.7% sulfur, 69.2% antimony and 0.4% moisture. Apparent density is 1.19 g/cc. Particle size is 325 mesh or 44 microns. One embodiment, utilized in the examples noted below, contains 27% S and 69% Sb.
The alloys of the present invention comprise copper, zinc, tin, sulfur, nickel, phosphorus, and antimony. In certain embodiments, one or more of manganese, zirconium, boron, titanium and/or carbon are included.
The alloys, comprise as a principal component, copper. Copper provides basic properties to the alloy, including antimicrobial properties and corrosion resistance. Pure copper has a relatively low yield strength, and tensile strength, and is not very hard relative to its common alloy classes of bronze and brass. Therefore, it is desirable to improve the properties of copper for use in many applications through alloying. The copper will typically be added as a base ingot. The base ingot's composition purity will vary depending on the source mine and post-mining processing. The copper may also be sourced from recycled materials, which can vary widely in composition. Therefore, it should be appreciated that ingot chemistry can vary, so, in one embodiment, the chemistry of the base ingot is taken into account. For example, the amount of zinc in the base ingot is taken into account when determining how much additional zinc to add to arrive at the desired final composition for the alloy. The base ingot should be selected to provide the required copper for the alloy while considering the secondary elements in the base ingot and their intended presence in the final alloy since small amounts of various impurities, such as iron, are common and have no material effect on the desired properties.
Lead has typically been included as a component in copper alloys, particularly for applications such as plumbing where machinability is an important factor. Lead has a low melting point relative to many other elements common to copper alloys. As such, lead, in a copper alloy, tends to migrate to the interdendritic or grain boundary areas as the melt cools. The presence of lead at interdendritic or grain boundary areas can greatly improve machinability and pressure tightness. However, in recent decades the serious detrimental impacts of lead have made use of lead in many applications of copper alloys undesirable. In particular, the presence of the lead at the interdendritic or grain boundary areas, the feature that is generally accepted to improve machinability, is, in part, responsible for the unwanted ease with which lead can leach from a copper alloy.
Sulfur is added to the alloys of the present invention to overcome certain disadvantages of using leaded copper alloys. Sulfur present in the melt will typically react with transition metals also present in the melt to form transition metal sulphides. For example, copper sulfide and zinc sulfide may be formed, or, for embodiments where manganese is present, it can form manganese sulfide.
Sulfur provides similar properties as lead would impart to a copper alloy, without the health concerns associated with lead. Sulfur forms sulphides which it is believed tend to aggregate at the interdendritic or grain boundary areas. The presence of the sulphides provides a break in the metallic structure and a point for the formation of a chip in the grain boundary region and improve machining lubricity, allowing for improved overall machinability. The sulphides predominate in the alloys of the present invention provide improved lubricity. Good distribution of sulphides improves pressure tightness, as well as, machinability.
It is believed that the presence of tin in some embodiments increases the strength and hardness but reduces ductility by solid solution strengthening and by forming Cu—Sn intermetallic phase such as Cu3Sn. It also increases the solidification range. Casting fluidity increases with tin content. Tin also increases corrosion resistance. However, currently Sn is very expensive relative to other components.
With respect to zinc, it is believed that the presence of Zn is similar to that of Sn, but to a lesser degree, in certain embodiments approximately 2% Zn is roughly equivalent to 1% Sn with respect to the above mentioned improvements to characteristics noted above. Zn increases strength and hardness by solid solution hardening. However, Cu—Zn alloys have a short freezing range. Zn is much less expensive than Sn.
With respect to certain embodiments, iron can be considered an impurity picked up from stirring rods, skimmers, etc during melting and pouring operations, or as an impurity in the base ingot. Such categories of impurity have no material effect on alloy properties.
In some embodiments, nickel is included to increase strength and hardness. Further, nickel aids in distribution of the sulphide particles in the alloy. In one embodiment, adding nickel helps the sulfide precipitate during the cooling process of the casting. The precipitation of the sulfide is desirable as the suspended sulfides act as a substitute to the lead for chip breaking and machining lubricity during the post casting machining operations. With the lower lead content, it is believed that the sulfide precipitate will minimize the effects of lowered machinability.
Phosphorus may be added to provide deoxidation. The addition of phosphorus reduces the gas content in the liquid alloy. Removal of gas generally provides higher quality castings by reducing gas content in the melt and reducing porosity in the finished alloy. However, excess phosphorus can contribute to metal-mold reaction giving rise to low mechanical properties and porous castings.
Aluminum is, in some embodiments, such as semi-red brasses and tin bronzes, treated as an impurity. In such embodiments, aluminum has harmful effects on pressure tightness and mechanical properties. However, aluminum in yellow brass castings can selectively improve casting fluidity. It is believed that aluminum encourages a fine feathery dendritic structure in such embodiments which allows for easy flow of liquid metal.
Silicon is also considered an impurity. In foundries with multiple alloys, silicon based materials can lead to silicon contamination in non silicon containing alloys. A small amount of residual silicon can contaminate semi red brass alloys, making production of multiple alloys near impossible. In addition, the presence of silicon can reduce the mechanical properties of semi-red brass alloys.
Manganese may be added in certain embodiments. The manganese is believed to aid in the distribution of sulphides. In particular, the presence of manganese is believed to aid in the formation of and retention of zinc sulfide in the melt. In one embodiment, a small amount of manganese is added to improve pressure tightness. In one embodiment, manganese is added as MnS.
Either zirconium or boron may be added individually (not necessarily in combination) to produce a fine grained structure which improves surface finish of castings during polishing.
Carbon may be added in certain embodiments to improve pressure tightness, reduce porosity, and improve machinability. In one embodiment, carbon may be added to the alloy as copper coated graphite (“CCG”). One type of copper coated graphite product is available from Superior Graphite and sold under the name DesulcoMC™. One embodiment of the copper coated graphite utilizes graphite that contains 99.5% min carbon, 0.5% max ash, and 0.5% max moisture. US mesh size of particles is 200 or 125 microns. This graphite is coated with 60% Cu by weight and has very low S.
In another embodiment, carbon may be added to the alloy as calcinated petroleum coke (“CPC”) also known as thermally purified coke. CPC may be screened to size. In one aspect, 1% sulfur is added and the CPC is coated with 60% Cu by weight. CPC, because of its relatively higher and coarser S content compared to copper coated graphite, imparts slightly higher S to the alloy and hence, better machinability.
It is believed that a majority of the carbon is not present in the final alloy. Rather, it is believed that carbon particles are formed that float to the surface as dross or reacting to form carbon dioxide (around 2100 F.) that is released from the melt as a gas. It has been observed that final carbon content of alloy is about 0.005% with a low density of 2.2 g/cc. Carbon particles float and form CO2 at 2100 F. (like a carbon boil) and purify the melt. Thus, the alloys utilizing carbon may be more homogeneous and pure compared with other additions such as S, MnS, stibnite etc. Further, the atomic radius of carbon is 0.91×10−10 M, which is smaller than that of copper (1.57X−10 M). Without limiting the scope of the invention, it is believed that carbon because of its low atomic volume remains in the face centered cubic crystal lattice of copper, thus contributing to strength and ductility.
Titanium may be added in combination with carbon, such as in graphite form. Without limiting the scope of the invention, it is believed that the titanium aids in bonding the carbon particles with the copper matrix, particularly for raw graphite. For embodiments utilizing copper coated with carbon, titanium may not be useful to distribute the carbon.
Brass alloys having antimony have been shown to exhibit dezincification resistance. In addition, antimony may aid in chip breaking by segregating to the grain boundaries. This provides for improved machinability. Sb forms compounds with Cu (Cu2Sb) and Zn (ZnSb). As discussed further below in regard to the back scattered electron images (18B-F and 20B-F) in the alloy materials, Sb, if added as Stibnite, separates from the S and interacts with Sn and Cu. Antimony may be provided in the form of Stibnite, which has the benefit of also providing sulfur and avoiding certain issues that arise with the use of elemental sulfur.Alloy Formulations
It can be observed that the use of stibnite provides sulfur to the finished alloy in a similar amount as some other components, such as the much more expensive MnS. As has been noted above, the use of sulfur in the alloy formation provides several problems, including environmental concerns due to the amount of sulfur dust and sulfur dioxide released, often violently, into the environment rather than integrated into the alloy melt. The use of sources of sulfur that provide for a better “yield” with regard to the amount of sulfur added and that retained in the finished alloy has been observed to be beneficial. Further, various sulfur sources could be utilized, but any non-sulfur component may have a negative impact on the properties of the finished alloy. Further, cost and availability are a consideration for selecting a sulfide for use as a sulfur source in the alloy. It has been observed that stibnite in the range of 0.4 to 1.6% provides sulfur in the amount desired and the antimony that remains in the alloy does not have an unacceptable impact on the properties of the finished alloys. A discussion of the impact of the antimony on the alloy mechanical properties is discussed further below.
One embodiment of the invention relates to a composition of matter comprising 82% to about 89% copper, about 0.01% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, about 2.0% to about 4.0% tin, less than about 0.09% lead, about 5.0% to about 14.0% zinc, and about 0.5 to about 2.0% nickel. In one embodiment, less than 0.65% sulfur is utilized to minimize the formation of gases such as sulfur dioxide, which negatively impact the mechanical properties of the finished product made from the alloy.
In one embodiment of the invention, the composition comprises 86% to about 89% copper, about 0.1% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, about 7.5% to about 8.5% tin, less than about 0.09% lead, about 1.0% to about 5.0% zinc, and about 1.0% % nickel.
In one embodiment of the invention, the composition comprises 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, about 1.5% tin, less than about 0.09% lead, about 31.0% to about 41.0% zinc, and about 1.5% % nickel.
In one embodiment of the invention, the composition comprises 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, less than about 0.09% lead, and about 31.0% to about 41.0% zinc.
In one embodiment, the brass alloy includes stibnite. The stibnite may be added in the range of greater than zero but less than 1.2%. In one embodiment, the preferred range is about 0.4 to about 1.2%. In one embodiment, the stibnite is 1.64%. In an alternative embodiment, the stibnite is 0.6%. In an alternative embodiment, the stibnite is 0.4%. The preferred embodiment utilizes about 1% stibnite. Addition of elemental S contributes to environmental problems due to release of sulfur dust and S02 to the atmosphere. The use of stibnite provides a source of antimony and a source of sulfur, without the drawbacks associated with working with elemental sulfur in alloy melts. The preferred range for Sb, S and stibnite, in the final alloy, are 0.3 to 0.8%, 0.1 to 0.35% and 0.4 to 1% respectively. (This is evident from
In certain embodiments, the brass alloy may include stibnite in combination with carbon. In one embodiment, the alloy includes 1.0% CCG or CPC and 1% stibnite. In a further embodiment, an additional 0.2% sulphur is provided for better machinability. In one embodiment, 1% carbon and 1% stibnite is utilized. In one embodiment, the stibnite is 0.6% and the carbon is 1. In an alternative embodiment, the stibnite is 1.64% and the carbon is 1.5%. In one embodiment, the carbon is copper coated graphite. In an alternative embodiment, the carbon is CPC.
It should be appreciated that the total amount of stibnite utilized in the melt can be varied to alter the amount of sulfur and the amount of antimony in the final alloy. For example, using a 27% S/69% Sb: 0.4% Stibnite gives 0.071% S and 0.27% Sb; 0.6% Stibnite gives 0.12% S and 0.4% Sb; 0.8% stibnite gives 0.2% S and 0.64% Sb; 1% stibnite gives 0.25% S and 0.77% Sb; 1.2% stibnite gives 0.278% S and 0.859% Sb, and 1.64% Stibnite gives 0.4% S and 1.35% Sb.
In one embodiment, about 0.5 to about 1.0 CCG (or CPC) together with about 0.8 to about 1.0 Stibnite provides desirable mechanical properties and machinability. The use of the stibnite provides benefits of sulfur while avoiding many of the issues with using pure sulfur in an alloy melt, including flaring and excess dross. As shown in the SEM (
The addition of stibnite to provide sulfur and antimony provides several advantages over the use of elemental sulfur. The use of sulfur results in undesired consequences, including environmental impact. For example, sulfur addition to the melt may cause flaring that results in the loss of sulfur as well as dangerous conditions during the addition. Further, the use of sulfur directly results in a lower yield with respect to the percentage of added sulfur that enters the melt and the final alloy, as much of the sulfur is lost to dross. The increase in dross can cause other problems with the alloying.
In one embodiment, the stibnite is wrapped in copper foil prior to addition to the melt. The wrapped stibnite may be added after melting the ingots and bringing temperature to about 2000 F.
In on embodiment, about 0.5 to about 1.0 CCG (or CPC) is utilized with about 0.8 to about 1.0 Stibnite to provide the best combination of mechanical properties and machinability. In a further embodiment, additional sulfur may be added to further increase the amount of sulfur in the alloy.Alloy Characteristics
In one embodiment, an alloy of the present invention solidifies in a manner such that a multitude of discrete particles of sulfur/sulfide are distributed throughout in a generally uniform manner throughout the casting. These nonmetallic sulfur particles serve to improve lubricity and break chips developed during the machining of parts cast in this new alloy, thereby improving machinability with a significant or complete reduction in the amount of lead. Without limiting the scope of the invention, the sulfides are believed to improve lubricity. The presence of antimony further improves properties of the C84030 red brass as described below. Embodiments utilizing stibnite provide for a source of antimony and sulfur while also delivering the sulfur in a form more readily compatible with the alloy melt process.
The preferred embodiments of the described alloy retain machinability advantages of the current leaded alloys. Further, it is believed that due to the relative scarcity of certain materials involved, the preferred embodiments of the ingot alloy will cost considerately less than that of the bismuth and/or selenium alloyed brasses that are currently advocated for replacement of leaded brass alloys. The sulfur is present in certain embodiments described herein as a sulfide which is soluble in the melt, but is precipitated as a sulfide during solidification and subsequent cooling of the alloy in a piece part. This precipitated sulfur enables improved machinability by serving as a chip breaker similar to the function of lead in alloys and in bismuth and selenium alloys. In the case of bismuth and/or selenium alloys the formation of bismuthides or selenides, along with some metallic bismuth, accomplishes a similar objective as this new sulfur containing alloy. The improvement in machinability may show up as increased tool life, improved machining surfaces, reduced tool forces, etc. This new idea also supplies the industry with a low lead brass/bronze which in today's environment is seeing any number of regulatory authorities limit by law the amount of lead that can be contained in plumbing fittings.Melt Process
In one embodiment, graphite is placed on the bottom of the crucible prior to heating. In one embodiment, silicon carbide or clay graphite crucibles may be used in the melts. It is believed that the use of graphite reduces the loss of zinc during the heat without substantially becoming incorporated into the final alloy. In one embodiment, approximately two cups of graphite are used for a 90 to 95 lbs capacity crucible. For the examples used herein, a B-30 crucible was used for the melts, which has a capacity of 90 to 95 lbs of alloy. For embodiments using CPC or CCG, the carbon is wrapped in copper foil, preheated in oven at 150 C. to drive off moisture and plunged into the melt followed by stirring.
Based upon the desired end alloy's formulation, the required base ingot is placed in the crucible and the furnace started. The base ingot, is brought to a temperature of about 1,149 degrees Celsius to form a melt. In one embodiment a conventional gas-fired furnace is used, and in another an induction furnace is used. The furnace is then turned off, i.e. the melt is no longer heated. Then the additives, except, in one embodiment, for sulfur and phosphorus, are then plunged into the melt between 15 to 20 seconds to achieve desired levels of Zn, Ni and Sn. The additives comprise the materials needed to achieve the final desired alloy composition for a given base ingot.
In one embodiment, the additives comprise elemental forms of the elements to be present in the final alloy. Then a partial amount of slag is skimmed from the top of the melt.
The furnace is then brought to a temperature of about 1,171 Celsius. The furnace is then shut off and the sulfur additive is plunged in, such as in the form of stibnite. For certain embodiments having phosphorus added, such as for degassing/deoxidizing of the melt, the furnace is then reheated to a temperature of about 1,177 degrees Celsius and phosphorous is plunged into the melt as a Cu—P master alloy. Next, preferably all of the slag is skimmed from the top of the crucible. Tail castings for pressure testing and evaluation of machinability and plating, buttons, wedges and mini ingots for chemical analysis, and web bars for tensile testing are poured at about 1,149, about 1,116, and about 1,093 degrees Celsius respectively.Mechanical Properties
Mechanical properties of various embodiments of the present alloys were tested as well as those for red brass without antimony added (as stibnite or otherwise). Sample heats, prepared in accordance with the process above and the resultant alloys were tested for ultimate tensile strength (“UTS”), yield strength (“YS”), percent elongation (“E %”), Brinnell hardness (“BHN”), and Modulus of Elasticity (“MoE”).
It has been observed that the sulfur content of SRB increases when MnS is added along with 0.4 and 0.6% Stibnite. When 1.64% stibnite is utilized, the sulfur level goes to 0.4%, but Sb level also increases to 1.35%.
Antimony is observed to improve or not be detrimental to certain desirable properties of the brass alloy at low levels. Above 1.5% the antimony's presence begins to negatively impact mechanical properties. However, sufficient antimony is necessary to provide the improved characteristics. Thus, one embodiment of C84030 includes 0.1% to 1.5% antimony.
The use of carbon in a brass alloy provides beneficial results. SRB with CCG or CPC have UTS around 43.5 ksi, YS of 18.1 ksi, but elongation in the range 59% (49-61%). However, adding MnS to CCG decreases UTS slightly to (42.9 ksi), YS remains almost unchanged (17.95 ksi), elongation decreases to 33-51% (47% avg). High levels of stibnite, 1.64%, in combination with CCG or CPC decreases UTS to 38.5 ksi, YS is around 19.8 ksi and elongation drops to 17-22% (20% Avg).
The use of MnS in a brass alloy gives 42.3 ksi UTS, 18.08 ksi YS and 45% elongation. Adding MnS to CCG and CPC does give good combination of UTS, YS and % elongation. However, sulfur level is not high enough to produce desirable machinability. Besides, addition of MnS increases ingot cost significantly. Adding S to SRB gives 39.7 ksi UTS, 18.67 YS and 29% elongation.
Overall, the tested embodiments of yellow brass C28330 had comparable results to the two leaded alloys C26000 and C35600 mentioned above. It is believed that quarter hard, half hard, hard and extra hard correspond to different stages of cold rolling such as 10%, 30%, 45% cold reduction etc. The hardness depends on the work hardening behaviour of the alloy. Embodiments of C28330 were cold rolled from 0.150 to 0.040 inch. This corresponds to 73% cold reduction. This is equivalent to extra hard condition.
Machinability was tested for certain embodiments of semi-red brass C84030 and yellow brass C28330. Machinability testing described in the present application was performed using the following method. The piece parts were machined by a coolant fed, 2 axis, CNC Turning Center. The cutting tool was a carbide insert. The machinability is based on a ratio of energy that was used during the turning on the above mentioned CNC Turning Center. The calculation formula can be written as follows:
- CF=Cutting Force
- E1=Energy used during the turning of a “known” alloy C 36000 (CDA).
- E2=Energy used during the turning of the New Alloy.
- Feed rate=0.005 IPR
- Spindle Speed=1,500 RPM
- Depth of Cut=Radial Depth of Cut=0.038 inches
An electrical meter was used to measure the electrical pull while the cutting tool was under load. This pull was captured via milliamp measurement. Table 1 below lists the chemical composition and machinability rating for several tested samples. Table 2 below lists the chemical composition and machinability rating for several tested samples of a C84030 red brass in accordance with the present invention. Table 3 below lists the chemical composition and machinability rating for several tested samples of a C28330 yellow brass in accordance with the present invention.
Machinability testing of embodiments of C84030 red brass indicate the addition of CCG does not improve machinability. There is some improvement in machinability when CCG and MnS are added together. The addition of sulfur improves machinability; however, addition of sulfur creates a lot of fumes in the melting area which is not environmentally friendly. The addition of MnS improves machinability; however, MnS is very expensive and increases ingot cost significantly. The addition of antimony as stibnite improves machinability. However, the benefits to machinability of embodiments of the C84030 red brass are lessened above 1% stibnite (for example, providing 0.8% antimony) as machinability decreases when stibnite content exceeds 1%. Further, it has been observed that antimony, for example provided as stibnite, in combination with MnS or CCP improves machinability. In one embodiment, a red-brass alloy includes 0.4-1% stibnite. In one embodiment, 0.3-0.8% antimony is included.
Machinability index of wrought alloy C28330 was 61%, which compares with C84030 containing Sb under 1%. It was observed that tail castings produced by permanent mold casting were used for machinability evaluation. These have a fine grain structure compared with sand cast C84030 tail castings. Chip morphology of C28330 was not good in comparison with C84030. However, it should be noted that the machined surfaces looked good. It should be appreciated that the possibility exists that the machinability rating could change if different speeds, feeds and tool geometry were to be used and samples can be machined well with proper use of tools and appropriate feed rate and speed.Effect of Stibnite, Antimony, and Sulfur content on Mechanical Properties of Semi Red Brass
Initially, the impact of sulfur upon the alloy's mechanical properties can be studied. Table 4 shows the effect of sulfur addition on mechanical properties (UTS, YS, and % Elongation) of four alloys from
The impact of various components in the alloys of the present invention was tested. Table 5 lists the seven alloys of the present invention from
The back scattered electron images (
Micrographical analysis was done on certain embodiments of C84030 red brass as indicated in
A portion of each sample was mounted, metallographically prepared and then examined optically using an inverted metallograph and a scanning electron microscope equipped with energy dispersive spectroscopy (SEM/EDS) in backscatter electron (BE) mode for semi-quantitative chemical content and elemental mapping. BE mode achieves greater contrast between elements of differing atomic weight percentages.Results Red Brass
The observed microstructures consist of dispersed particles throughout the copper-rich matrix. As polished metallograph photomicrographs were taken at 500×. Image analysis was then performed to determine the particle size. The minimum, maximum and average measurements are reported in the following table. As polished photomicrographs are provided in
A micrographical analysis of certain embodiments was undertaken to characterize the alloy and provide information regarding the microstructure and positioning of various elements within the alloy's structure.
The micrograph information supports the improved mechanical properties discussed above. Because some antimony remains in solid solution, a good % elongation is observed. The intermetallic compound and the solid solution contribute to strength. However, if there is too much intermetallic compound, strength and % elongation could gradually decrease. A decrease in UTS and % elongation is observed at 1.64% Stibnite addition.
SEM/EDS element analysis reveals dispersed particles primarily consisting of sulfur, zinc, tin, or antimony. SEM backscatter images taken at 200× and 1000× along with element maps at 1500× showing the requested element intensities are provided in
SEM EDS spectra results of the base material from sample 1109320 consist of significant amounts of copper with lesser amounts of tin, nickel, and zinc (see location 1,
SEM EDS spectra results of the base material from sample 84XX42-022812-H20P2-9A consist of significant amounts of copper with lesser amounts of tin, nickel, and zinc (see location 1,
Semi-quantitative chemical analysis data is reported in table 8 for the above locations. Sb is present in the matrix in solid solution and also in the intermetallic compounds.
SEM EDS spectra results of the base material from sample 84XX9-011312-H18P2-10A consist of significant amounts of copper with lesser amounts of tin, antimony, nickel and zinc (see location 1,
Semi-quantitative chemical analysis data is reported In Table 9 for the above locations. Sb is present in the matrix in solid solution and also in the intermetallic compounds.
Metallography work was also done on embodiments of yellow brass C28330. Chemistry of this alloy (28330-030613-P4H2A) is given in
SEM/EDS spectra analysis was taken at several locations including the base material and dispersed inclusions throughout the base material on all three samples.
Results are semi-quantitative, the spectra results are in weight percent unless otherwise indicated and the method used was SEM/EDS
The results indicate that grain size of permanent mold cast sample is about 50 microns (
As discussed above, copper may utilize a number of elements to alloy with. The use of stibnite as disclosed herein was tested in comparison to two forms of carbon, CCG and CPC, sulfur, manganese sulfide, and combinations thereof as indicated in Table 11.
Phase information was gathered for red brass C84030 (
The base composition: 87 Cu, 9 Zn, 3 Sn, 1 Ni, 0.4 S for the red brass, plus the indicated amount of antimony. It is generally observed that Sb forms stable compounds with Cu (Cu2Sb), with Mn (MnSb and Mn2Sb) with Zn (ZnSb) and with S (Sb2S3). Among these, it is believed that only Cu2Sb forms when Sb is added in the range of 0.4 to 1.3 wt %. The addition of Sb did not change the liquidus or the solidus temperatures.
Microstructural analysis shows that there are Zn, Sn and Ni in solid solution with Cu. In view of the microstructure and the phase analysis, it is believed that stibnite breaks down to Sb and S. Some Sb is in solid solution with Cu and some forms Cu2Sb compound. S combines with Zn and also Cu to form ZnS and Cu2S. The high level of Sn and Cu in some phases indicates that it is Cu3Sn phase.
Based on the observed phases described above, a 100 kg overall alloy will contain the following amounts of each phase in kg.
A 100 kg overall alloy will contain the following amounts of each phase in kg.
Thermal investigation of the systems was performed using a DSC-2400 Setaram Setsys Differential Scanning calorimetry. Temperature calibration of the DSC was done using 7 pure metals: In, Sn, Pb, Zn, Al, Ag, and Au spanning the temperature range from 156 to 1065° C. The samples were cut and mechanically polished to remove any possible contaminated surface layers. Afterwards, they were cleaned with ethanol and placed in a graphite crucible with a lid cover to limit possible evaporation and protect the apparatus. To avoid oxidation, the analysis chamber was evacuated to 10−2 mbar and then flooded with argon. The DSC measurements were carried out under flowing argon atmosphere. Three replicas of each sample were tested. The weight of the sample was 62-78 mg.
Two samples, one from the semi-red brass, C84030 and the other from the yellow brass, C28330 were used to measure the liquidus and solidus temperatures. Their compositions are given in Table 16
To find out the solidus and liquidus temperature the samples were heated from room temperature up to 1100 C., then cooled to 800 C., then heated to 1100 C. and cooled to 800 C. again. Finally the apparatus was brought down to room temperature. These experiments were conducted under an Argon atmosphere which was preceded by vacuum pump evacuation of the DSC chamber. Thus data from two cycles were collected. The heating was done at 10 C./min and the cooling at 15 C./min, as agreed. The solidus and the liquidus temperatures, obtained from both cycles are provided in the table below. Data from the first cycle is more representative of the alloys because of the Zn loss that occurs in the second cycle which was 7.3% for C84030 (low-Zn alloy) and 35.4% for the C28330 (high Zn) alloy. The measured values are shown in Table 17.
Four brass samples, two commercial brasses and embodiments of the C28330 yellow brass and C84030 red brass, were evaluated for the resistance to dezincification corrosion in accordance with ISO 6590, “Corrosion of Metals and Alloys-Determination of the Dezincification Resistance of Brass.” In this test, ground cross sections are immersed in a 1% copper chloride solution at 75±5° C. for 24 hours. At the end of this immersion period, polished cross sections are prepared perpendicular to the exposed surfaces, and the depth of any dezincification corrosion is measured. This analysis was performed in both a thin area and a thick area of the casting per the ISO specification. Where possible the sections were prepared from thick and thin walled sections. The samples that exhibited a uniform cross section samples were taken from the edge and the core. More than 100 microns of dezincification penetration was considered to exceed the allowable dezincification.
This dezincification results show that embodiments of yellow brass C28330 of the present invention provide for superior resistance to dezincification in comparison with commercial alloys, including C36000 yellow brass. Specifically, the results indicate that the section from the core of the sample identified as “MBAF 180” and both the thick and thin walled sections from the sample identified as “036000 Ht#1-Yeager” exhibit significant dezincification corrosion when tested in accordance with ISO 6509, “Corrosion of Metals and Alloys-Determination of the Dezincification Resistance of Brass.” ISO 6509 does not include any acceptance criteria, however, the dezincification depth of these samples exceed the 100 micron maximum dezincification depth included in the similar Australian Standard AS 2345, “Dezincification Resistance of Copper Alloys.” These results indicate these samples are susceptible to dezincification corrosion. This investigation indicates that the section from the edge of the sample identified as “MBAF 180” and the sections from both the core and the edge of the samples identified as “28330-Lab#358050 P4 H2a” and “84030-62412-H3P2-9” exhibit dezincification corrosion which is in conformance with the 100 micron maximum dezincification depth when tested in accordance with ISO 6509.Parameters of Properties Experiments
A series of alloys were created and tested to determine the properties of alloys having a composition outside of that set forth for the C84030 red brass alloy in
In order to provide a “figure of merit” to quantify the properties of the variance alloys in comparison to C84030, UTS, YS and EL % properties were utilized. Sufficient results for each of those three property values had to occur together for one of the pours to create further investigation. These three property values are:
- 1) The Ultimate Tensile Strength has to be greater than the maximum limit of C 84030 (>than 42.9)
- 2) The Yield Strength has to be greater than the maximum limit of C 84030 (>than 20.3)
- 3) The Elongation % has to be greater than the typical limit of C 84400 (>than 26)
Table 19 below provides a summary of the results of the variance testing. The design of experiment (DOE) was conceptually structured based on a statistical Taguchi method. The defining elements to the alloy were brought both above and below their defined limits. Table 19 below shows this logic always with the end result being 100%. The end goal being to see if better properties existed by going both above and below the defined limits to the nominal range for C84030.
The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
1. A composition of matter comprising:
- a copper content of about 82% to about 89%;
- a sulfur content of about 0.01% to about 0.65%;
- an antimony content of about 0.1 to about 1.5%
- a tin content of about 2.0% to about 4.0%;
- a lead content of less than about 0.09%;
- a zinc content of about 5.0% to about 14.0%; and
- a nickel content of about 0.5% to about 2.0%
2. The composition of matter of claim 1, further comprising an antimony content of 0.1 to 1.0%.
3. The composition of matter of claim 1, wherein at least a portion of the sulfur and antimony are derived from stibnite.
4. The composition of matter of claim 1, wherein at least a portion of the sulfur and antimony are derived from 1% stibnite.
5. The composition of claim 1, further comprising about 0.3% titanium
6. The composition of claim 1 further comprising about 0.1% carbon.
7. A composition of matter comprising about 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, about 1.5% tin, less than about 0.09% lead, about 31.0% to about 41.0% zinc, and about 1.5% % nickel.
8. The composition of matter of claim 7, further comprising an antimony content of 0.1 to 1.0%.
9. The composition of matter of claim 7, wherein at least a portion of the sulfur and antimony are derived from stibnite.
10. The composition of matter of claim 7, wherein at least a portion of the sulfur and antimony are derived from 1% stibnite.
11. The composition of claim 7, further comprising about 0.1% titanium
12. The composition of claim 7 further comprising about 0.1% carbon.
13. A composition of matter comprising about 58% to about 62% copper, about 0.01% to about 0.65% sulfur, greater than 0.1 to about 1.5% antimony, less than about 0.09% lead, and about 31.0% to about 41.0% zinc.
14. The composition of matter of claim 1, further comprising an antimony content of 0.1 to 1.5%.
15. The composition of matter of claim 13, wherein at least a portion of the sulfur and antimony are derived from stibnite.
16. The composition of matter of claim 13, wherein at least a portion of the sulfur and antimony are derived from 1% stibnite.
17. The composition of claim 13, further comprising about 0.3% titanium
18. The composition of claim 13 further comprising about 0.1% carbon.
19. A composition of matter comprising about 86% to about 89% copper, about 0.01% to about 0.65% sulfur, greater than 0 to about 1.5% antimony, about 7.5% to about 8.5% tin, less than about 0.09% lead, about 1.0% to about 5.0% zinc, and about 1.0% % nickel.
20. A method for adding sulfur to a brass alloy, comprising:
- heating a base ingot to a temperature of about 2,100 degrees Fahrenheit to form a melt;
- adding stibnite wrapped in copper foil and maintaining the temperature at about 2000 F.;
- ceasing heating of the melt and adding additives into the melt;
- skimming at least a partial amount of slag from the melt;
- heating the melt to a temperature of about 2,140 Fahrenheit;
- ceasing heating of the melt and plunging stibnite into the melt;
- heating the melt to a temperature of about 2,150 degrees Fahrenheit; and
- removing slag from the melt;
- wherein the additives include tin, zinc, nickel, and carbon.