Monday, June 16, 2008
Densities of popular metals
Metal Density (Lbs/Cubic Inch)
Aluminum = 0.0975
Ampco Metal = 0.274
SAE660 bearing Bronze = 0.318
Brass = 0.308
Copper = 0.323
Cupro Nickel = 0.323
Gold = 0.697
Iron = 0.284
Lead = 0.41
Magnesium = 0.061
Manganese = 0.267
Muntz Metal = 0.308
Naval brass = 0.304
Nickel = 0.322
Platinum = 0.775
Silver = 0.378
Stainless steel = 0.2871
Steel = 0.284
Tin = 0.284
Tobin Bronze = 0.304
Zinc = 0.258
Aluminum = 0.0975
Ampco Metal = 0.274
SAE660 bearing Bronze = 0.318
Brass = 0.308
Copper = 0.323
Cupro Nickel = 0.323
Gold = 0.697
Iron = 0.284
Lead = 0.41
Magnesium = 0.061
Manganese = 0.267
Muntz Metal = 0.308
Naval brass = 0.304
Nickel = 0.322
Platinum = 0.775
Silver = 0.378
Stainless steel = 0.2871
Steel = 0.284
Tin = 0.284
Tobin Bronze = 0.304
Zinc = 0.258
Monday, June 09, 2008
ALUMINUM BRONZE
Foundry practice for aluminum bronze must be carefully controlled. The elimination of oxide inclusions is one of the principal problems. Agitation of the metal, whether in the furnace or during casting, can lead to serious results.
It is important to design the gating so that the metal enters and fills the mold cavity without turbulence. Gaes and runners should be wide and thin to help the alloy skim itself before entering the .mold. Pouring must be conducted so that the metal rises very slowly in the mold.
After the casting is poured, slow cooling should be avoided or "self-annealing", a. type of casting embrittlement found in low iron-aluminum-copper alloys, may take place. Castings should be removed from the mold as soon as they are solid enough to handle without distortion.If the casting
are large, it may help to spray them with water after they have been removed from the sand. Chilled castings usually cool rapidly enough so that no additional cooling is necessary. If no other method is available, self-annealing effect.,> may be overcome by heat treating the castings, or by using an a110y with higher iron and nickel content. Aluminum bronzes with 4% iron or high nickel content are less subject to "self-annealing".
Although aluminum bronze is usually thought to have a high solidification shrinkage, experimental data show that shrinkage is considerably less than for most copper-base casting alloys. The apparent shriI1kage problem is probably associated with the very narrow solidification range, which
gives the metal similar freezing characteristics to pure metal. As a result, piping is a problem and large, carefully placed risers are frequently necessary.
It is important to design the gating so that the metal enters and fills the mold cavity without turbulence. Gaes and runners should be wide and thin to help the alloy skim itself before entering the .mold. Pouring must be conducted so that the metal rises very slowly in the mold.
After the casting is poured, slow cooling should be avoided or "self-annealing", a. type of casting embrittlement found in low iron-aluminum-copper alloys, may take place. Castings should be removed from the mold as soon as they are solid enough to handle without distortion.If the casting
are large, it may help to spray them with water after they have been removed from the sand. Chilled castings usually cool rapidly enough so that no additional cooling is necessary. If no other method is available, self-annealing effect.,> may be overcome by heat treating the castings, or by using an a110y with higher iron and nickel content. Aluminum bronzes with 4% iron or high nickel content are less subject to "self-annealing".
Although aluminum bronze is usually thought to have a high solidification shrinkage, experimental data show that shrinkage is considerably less than for most copper-base casting alloys. The apparent shriI1kage problem is probably associated with the very narrow solidification range, which
gives the metal similar freezing characteristics to pure metal. As a result, piping is a problem and large, carefully placed risers are frequently necessary.
MANGANESE BRONZE
In melting manganese bronze, it is essential to maintain careful control of the chemical composition, especially of the copper and zinc content. The practice of "flaring" or heating manganese bronze until the zinc distills off, is of questionable "alue and may cause indeterminate zinc losses
which, in turn, will change mechanical properties of the alloy. Heat the metal only to the temperature
needed to pour sound castings.
Due to the dross-fanning tendencies of manganese bronze, gating should be such that there is a minimum of turbulence when the metal enters the mold. Top or bottom gating may be used, and strainer cores, choke gates and dross traps can be applied effectively to produce clean and sound castings. Gates and runners should be wide and thin so that the metal may skim itself before entering the mold cavity. The sprue should be filled quickly and kept full.
Manganese bronze has a high solidification shrinkage and large risers must be used so that all parts of the casting are adequately fed. Chills can be advantageously used to reduce the size and number of risers. Insulating sleeves and hot-topping compounds help in making risers feed more efficiently or in reducing riser size.
which, in turn, will change mechanical properties of the alloy. Heat the metal only to the temperature
needed to pour sound castings.
Due to the dross-fanning tendencies of manganese bronze, gating should be such that there is a minimum of turbulence when the metal enters the mold. Top or bottom gating may be used, and strainer cores, choke gates and dross traps can be applied effectively to produce clean and sound castings. Gates and runners should be wide and thin so that the metal may skim itself before entering the mold cavity. The sprue should be filled quickly and kept full.
Manganese bronze has a high solidification shrinkage and large risers must be used so that all parts of the casting are adequately fed. Chills can be advantageously used to reduce the size and number of risers. Insulating sleeves and hot-topping compounds help in making risers feed more efficiently or in reducing riser size.
LEADED YELLOW BRASSES
Melting practice for leaded yellow brasses is generally similar to that for tin bronzes and tin-lead bronzes.
Although there is usually little difficulty from gas absorption, the combustion atmosphere should be slightly oxidizing. The metal should be super heated only enough to permit handling and pouring at the required temperature. After removal from the furnace, the alloy should be skimmed carefully and permitted to stand in the open air until it reaches the proper casting temperature.
Hydrogen absorption is usually at a minimum because the large quantity of zinc vapor continually sweeps it away from the melt.
Yellow brasses show fairly high shrinkage during solidification and freezing. Gates and runners must be somewhat larger than for tin bronzes. Risers also must be large to provide for ample feeding of the sec6ons. To avoid drossy or dirty castings, gating must be arranged so that the metal enters the mold without agitation. Strainer cores and choke gates should be used when possible.
Pouring should be done carefully. Sprues should be choked and kept full. Sprue diameter should be as small as possible.
Although there is usually little difficulty from gas absorption, the combustion atmosphere should be slightly oxidizing. The metal should be super heated only enough to permit handling and pouring at the required temperature. After removal from the furnace, the alloy should be skimmed carefully and permitted to stand in the open air until it reaches the proper casting temperature.
Hydrogen absorption is usually at a minimum because the large quantity of zinc vapor continually sweeps it away from the melt.
Yellow brasses show fairly high shrinkage during solidification and freezing. Gates and runners must be somewhat larger than for tin bronzes. Risers also must be large to provide for ample feeding of the sec6ons. To avoid drossy or dirty castings, gating must be arranged so that the metal enters the mold without agitation. Strainer cores and choke gates should be used when possible.
Pouring should be done carefully. Sprues should be choked and kept full. Sprue diameter should be as small as possible.
HIGH LEADED TIN BRONZE
Some of the principal problems experienced in casting high-leaded tin bronzes are caused by low-melting constituents composed of the tin and lead in the alloy. At normal pouring temperatures, these alloys are so fluid that they may penetrate the mold. Attention should thus be given to the type of sand used and to the use of a mold or core wash that will resist metal penetration.
Leaded-tin bronzes may pick up gas which can cause casting defects, including one known as "mushrooming" or "purging". Gas picked up in the me(ting may accumulate in the last portion of the casting to freeze. building up sufficient pressure to blow the liquid metal up through the sprue or riser. The best possible melting practices must be applied to reduce gas pickup in melting. Liberal use of phosphor copper is also recommended. Additions of 15% phosphor copper up to six or eight ounces per hundred pounds of metal will often help insure sound castings.
Bushings or bearings cast in these alloys often have large cores. The gases given off by the cores may dissolve in the metal and show up as holes during machining. To prevent this from happening, the cores should be as permeable as possible. In many cases, hollow cores are desirable. Very hard cores should be avoided beC4use they usually contain unburnt oil, and also increase the possibility of hot-tearing around the core when the meta~ shrinks. Cores made by the C02 process or by the shell process may reduce gas from this particular source.
Application of the practices described above will help to control the subsurface porosity occasionally found when high-leaded tin bronze castings are machined.
Leaded-tin bronzes may pick up gas which can cause casting defects, including one known as "mushrooming" or "purging". Gas picked up in the me(ting may accumulate in the last portion of the casting to freeze. building up sufficient pressure to blow the liquid metal up through the sprue or riser. The best possible melting practices must be applied to reduce gas pickup in melting. Liberal use of phosphor copper is also recommended. Additions of 15% phosphor copper up to six or eight ounces per hundred pounds of metal will often help insure sound castings.
Bushings or bearings cast in these alloys often have large cores. The gases given off by the cores may dissolve in the metal and show up as holes during machining. To prevent this from happening, the cores should be as permeable as possible. In many cases, hollow cores are desirable. Very hard cores should be avoided beC4use they usually contain unburnt oil, and also increase the possibility of hot-tearing around the core when the meta~ shrinks. Cores made by the C02 process or by the shell process may reduce gas from this particular source.
Application of the practices described above will help to control the subsurface porosity occasionally found when high-leaded tin bronze castings are machined.
RED BRASS AND SEMI-RED BRASS
Bronze foundry men have had more experience in handling alloys of this type than in any other single group of copper-base casting alloy, and foundry practice for these materials is fairly we!! understood.
Multiple gating is highly desirable to avoid turbulence and overheating of local portions of the mold. Risers should be p1aced where they have access to hot metal. Sprues should be small in diameter and should be kept filled during pouring. Molds should be effective1y vented.
With the semi-red brasses. the cast ability i5 somewhat better. The higher zinc content may present a smoke. and fume pmb1em in the foundry. although this is usually not serious. The greater amount of zinc in these alloys may also necessitate more careful skimming before pouring to avoid dross being poured .into the mold cavity with the metal.
Phosphor-c:opper deoxidizer should be used with these alloys to help control the gas content and to improve their cast ability. Under usual conditions, the recommended addition is two ounces per hundred pounds of metal.
This group of alloys may be the easiest of all for the non-ferrous foundry man to handle. Good foundry practice will enable any foundry to produce salable red brass and semi-red brass castings.
Multiple gating is highly desirable to avoid turbulence and overheating of local portions of the mold. Risers should be p1aced where they have access to hot metal. Sprues should be small in diameter and should be kept filled during pouring. Molds should be effective1y vented.
With the semi-red brasses. the cast ability i5 somewhat better. The higher zinc content may present a smoke. and fume pmb1em in the foundry. although this is usually not serious. The greater amount of zinc in these alloys may also necessitate more careful skimming before pouring to avoid dross being poured .into the mold cavity with the metal.
Phosphor-c:opper deoxidizer should be used with these alloys to help control the gas content and to improve their cast ability. Under usual conditions, the recommended addition is two ounces per hundred pounds of metal.
This group of alloys may be the easiest of all for the non-ferrous foundry man to handle. Good foundry practice will enable any foundry to produce salable red brass and semi-red brass castings.
TIN BRONZE, LEADED TIN AND BRONZE
Because of their good mechanical properties and corrosion resistance, these alloys are often used in castings subject to hydrostatic or air pressures, as in valves, pumps, etc, The quality of such castings must be unusually high; they must be free of internal porosity, shrinkage, or other defects.
Good foundry practice is of critical importance in the casting of tin bronzes and leaded tin bronzes. All of these alloys have a wide freezing range of from 200" to 300" F. To produce sound castings in any of the tin bronzes, gates and risers should be designed so that the closest possible approximation is made to true directional solidification.
Gating must be non-turbulent and the metal flow distributed through as many gates as possible to avoid hot spots. The mold should be filled quickly. Risers should be placed so that they do not unnecessarily delay the freezing of heavy sections. Such delay results in a coarse. open structure that will leak under pressure. Risers should preferably feed hot metal directly into the casting without forcing it to cross through any thin section of the casting.
The use of chills with these alloys is highly desirable, and it is often necessary to use them liberally if complex castings are to be made sound.
It is very difficult to feed tin bronze into a parallel section. one inch or more thick. by a riser alone.. Tin bronzes begin freezing at the sand-metal interface and freeze progressively toward the center. leaving a pasty mixture of liquid and solid in the center. The flow of molten metal from the riser into a high, thick section will usually be obstructed by the already solidified portion of the wall. The liberal use' of chills in the drag of such a casting, or riser hot-topping compounds and riser insulators, may be helpful in producing sound sections.
Because of the solidification pattern of tin bronzes, ga5CS may aggravate the shrinkage condition by enlarging cavities until they are interconnected and can cause leakage. Following the melting practices listed in Part I of this Section should help minimize this condition.
The tin bronzes improve in cast ability and soundness when phosphor copper is used as a deoxidizer.
Good foundry practice is of critical importance in the casting of tin bronzes and leaded tin bronzes. All of these alloys have a wide freezing range of from 200" to 300" F. To produce sound castings in any of the tin bronzes, gates and risers should be designed so that the closest possible approximation is made to true directional solidification.
Gating must be non-turbulent and the metal flow distributed through as many gates as possible to avoid hot spots. The mold should be filled quickly. Risers should be placed so that they do not unnecessarily delay the freezing of heavy sections. Such delay results in a coarse. open structure that will leak under pressure. Risers should preferably feed hot metal directly into the casting without forcing it to cross through any thin section of the casting.
The use of chills with these alloys is highly desirable, and it is often necessary to use them liberally if complex castings are to be made sound.
It is very difficult to feed tin bronze into a parallel section. one inch or more thick. by a riser alone.. Tin bronzes begin freezing at the sand-metal interface and freeze progressively toward the center. leaving a pasty mixture of liquid and solid in the center. The flow of molten metal from the riser into a high, thick section will usually be obstructed by the already solidified portion of the wall. The liberal use' of chills in the drag of such a casting, or riser hot-topping compounds and riser insulators, may be helpful in producing sound sections.
Because of the solidification pattern of tin bronzes, ga5CS may aggravate the shrinkage condition by enlarging cavities until they are interconnected and can cause leakage. Following the melting practices listed in Part I of this Section should help minimize this condition.
The tin bronzes improve in cast ability and soundness when phosphor copper is used as a deoxidizer.
Sunday, June 08, 2008
Recommended Pouring Practice
1 At all times the alloy should be kept as quiet and free from agitation as possible. It should never be stirred prior to pouring.
2 The lip of the crucible or ladle should be brought as close as possible to the top Qf the sprue to avoid turbulent pouring, which creates dross.
3 The stream of molten metal should be of such size
that it can be controlled without splashing.
4 The metal should be poured into the sprue without
interruption. A steady stream is desirable.
2 The lip of the crucible or ladle should be brought as close as possible to the top Qf the sprue to avoid turbulent pouring, which creates dross.
3 The stream of molten metal should be of such size
that it can be controlled without splashing.
4 The metal should be poured into the sprue without
interruption. A steady stream is desirable.
brass pouring
The pouring practice used for copper base casting alloys does not vary much from that used for other metals:
Improper pouring may produce excess oxidation and if the oxides an: washed into the castings, they may show up during machining operations. When casting aluminum bronzes it is most important to pour in a non-turbu1ent fashion because the oxides fanned are tenacious and strong and can cause irreparable damage in the casting.
Alloys with high zinc content have a pronounced tendency to form oxides during pouring. It is important that the sprue be kept full and that the stream of metal from the crucible or ladle be uninterrupted while the mold is being filled. Splashing, dumping, or other such practices must be avoided.
Improper pouring may produce excess oxidation and if the oxides an: washed into the castings, they may show up during machining operations. When casting aluminum bronzes it is most important to pour in a non-turbu1ent fashion because the oxides fanned are tenacious and strong and can cause irreparable damage in the casting.
Alloys with high zinc content have a pronounced tendency to form oxides during pouring. It is important that the sprue be kept full and that the stream of metal from the crucible or ladle be uninterrupted while the mold is being filled. Splashing, dumping, or other such practices must be avoided.
Recommended Metal Melting Practice
1 Charge only clean, dry ingot or back scrap. The
presence of moisture or organic materials may cause gas in the metal after it is molten.
2 Use a clean crucible or a furnace in good condition to help avoid chemical contamination of tile alloy.
3 Melt as quickly as possible in an oxidizing atmosphere. This mean; there should be a slight amount of oxygen in the products of combustion. A sharp, green flame over tbe furnace in fuel-fired melting usually indicates this condition.
4 Do not overheat the metal. Superheat only as much
as needed to take the metal from the furnace, handle it, and pour it into the mold at the best pouring temperature.
5 After the metal is taken from the furnace, skim it carefully without stirring or agitation. Measure the temperature, and when it has reached a suitable point, add the necessary deoxidizer and pour the castings.
presence of moisture or organic materials may cause gas in the metal after it is molten.
2 Use a clean crucible or a furnace in good condition to help avoid chemical contamination of tile alloy.
3 Melt as quickly as possible in an oxidizing atmosphere. This mean; there should be a slight amount of oxygen in the products of combustion. A sharp, green flame over tbe furnace in fuel-fired melting usually indicates this condition.
4 Do not overheat the metal. Superheat only as much
as needed to take the metal from the furnace, handle it, and pour it into the mold at the best pouring temperature.
5 After the metal is taken from the furnace, skim it carefully without stirring or agitation. Measure the temperature, and when it has reached a suitable point, add the necessary deoxidizer and pour the castings.
control at metal temperature
There is a direct relationship between temperature and the amount of gas a copper-base alloy will dissolve while in the molten state. The higher the temperature, the more gas will be absorbed. Thus it is essential( that metal b~ taken from the furnace as soon as it has reached the minimum temperature necessary for pouring molds.A pyrometer should be used to determine the melting temperature of copper-base alloys. Generally, the melt should only be taken to the temperature which will permit removal from the furnace., skimming, deoxidizing, other necessary handling, and pouring at the required pouring temperature. This means controlled superheating, which is most important in producing quality copper alloys for quality castings
creation of metal oxides
While some oxidation is desirable for controlling the solution of gases in molten metal, excesses of oxygen will combine with the molten alloy to form undesirable oxides. or dross.
It is quite common to find the oxides of copper, zinc, tin and lead in the slag of the 85-5-5-5 type alloy, for example. Silicon bronze alloys are apparently protected against harmful oxidation by a film of some silicon oxide that forms on the bath. Aluminum bronzes easily form oxides of aluminum, which' complicate the handling of these alloys. The yellow brasses or manganese bronzes frequently form large quantities of zinc oxide.
In a reducing melting atmosphere, such oxidation is negligible, but when an oxidizing melting technique is used, it is necessary to closely control the melting atmosphere so that only a slight amount of free oxygen is present in the products of combustion. Some foundry men use cover fluxes to prevent the formation of undesirab1e oxides. While it is true that certain chemicals will partially protect the metal from exposure to air, improper usage of such covers may exclude too much oxygen and thus Permit hydrogen gas content to build up.
Deoxidizers are helpful in reducing the amount of metal oxide present in the bath except with silicon, manganese and aluminum bronze. Since oxides will impair the castability of the alloy, the deoxidizer should be added immediately after the molten rnetal has been skimmed of dross. It will then inhibit the additional pickup' of oxygen during pouring operations.
One of the most harmful common practices in brass and bronze foundries is stirring or agitating the molten metal' while it is .in the furnace or in the crucible on the foundry floor. Stirring will thoroughly mix the oxides into the metal, and when the casting is finally poured, it will contain .an unusual amount of dross. Of course, when adding deoxidizers, gentle mixing is required, but excessive or violent stirring must be avoided.
It is quite common to find the oxides of copper, zinc, tin and lead in the slag of the 85-5-5-5 type alloy, for example. Silicon bronze alloys are apparently protected against harmful oxidation by a film of some silicon oxide that forms on the bath. Aluminum bronzes easily form oxides of aluminum, which' complicate the handling of these alloys. The yellow brasses or manganese bronzes frequently form large quantities of zinc oxide.
In a reducing melting atmosphere, such oxidation is negligible, but when an oxidizing melting technique is used, it is necessary to closely control the melting atmosphere so that only a slight amount of free oxygen is present in the products of combustion. Some foundry men use cover fluxes to prevent the formation of undesirab1e oxides. While it is true that certain chemicals will partially protect the metal from exposure to air, improper usage of such covers may exclude too much oxygen and thus Permit hydrogen gas content to build up.
Deoxidizers are helpful in reducing the amount of metal oxide present in the bath except with silicon, manganese and aluminum bronze. Since oxides will impair the castability of the alloy, the deoxidizer should be added immediately after the molten rnetal has been skimmed of dross. It will then inhibit the additional pickup' of oxygen during pouring operations.
One of the most harmful common practices in brass and bronze foundries is stirring or agitating the molten metal' while it is .in the furnace or in the crucible on the foundry floor. Stirring will thoroughly mix the oxides into the metal, and when the casting is finally poured, it will contain .an unusual amount of dross. Of course, when adding deoxidizers, gentle mixing is required, but excessive or violent stirring must be avoided.
Friday, June 06, 2008
Brass has higher malleability than copper or zinc.
Brass has higher malleability than copper or zinc. The relatively low melting point of brass (900 to 940°C, depending on composition) and its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.
Today almost 90% of all brass alloys are recycled. Because most brass is nonmagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet. Brass scrap is collected and transported to the foundry where it is melted and recast into billets. Billets are heated and extruded into the desired form and size.
Brass Offers Good Corrosion Resistance from Water and Heat
Brass Offers Good Corrosion Resistance From Water and Heat and Resists Attack From Salt Water and Acids, Minerals and Peaty Soils Contained in Water. Relative Softness of Metal Provides for a Tight Seal and Ease of Installation. Brass Offers Many of the Same Advantages of Copper, With a Heavier Wall.
Sunday, June 01, 2008
HARDNESS OF BRASS
While Brinell Hardness is not a commonly required property of brass and bronze casting alloys, it is apparent that in materials witll such a range of tensile strength there will be considerable hardness variation. roo.
The nighest hardness values found are in some of the aluminum bronzes; up to 350 BHN or higher. Other commonly used copper alloys offer bardne$s values from 50 BHN to 250 BHN.
The nighest hardness values found are in some of the aluminum bronzes; up to 350 BHN or higher. Other commonly used copper alloys offer bardne$s values from 50 BHN to 250 BHN.
DUCTILITY
With their excellent tensile properties, copper alloys offer the engineer and designer a wide range of ductility. It is possible, for example, to have silicon bronze with as much as 75 percent elongation; or an aluminum bronze with as little as 2 or 3 percent.
MECHANICAL PROPERTIES OF BRASS AND BRONZE
A wide range of tensile properties is available in brass and bronze casting alloys . . . from the low of 25,000 psi for nearly pure copper to as high as 120,000 psi in high-tensile manganese bronze without heat treatment. With this range of strength properties, these alloys all offer inherent corrosion resistance, greatly broadening their engineering usefulness.
MACHINABILITY
Another of the valuable properties of brass and bronze casting alloys is their exceIlent machinability.
Lead is present in many copper casting alloys. usually as fine(y divided particles which serve to break up chips when the metal is machined. Most of the leaded brasses and bronzes are thus considered "free-machining."
Because of their. good machinability. these leaded aDoys lend themselves well to modern high-speed productton methods. Millions of copper alloy castings are machined each year OD turrec lathes, automatic screw machines and other mgh-speed production devices. In many cases the ability to machine at high speed is the chief factor in the. selection of a copper alloy for a particular application.
Even the high-strength copper alloys that do not contain lead usually have much better than avemge machining properties.
Lead is present in many copper casting alloys. usually as fine(y divided particles which serve to break up chips when the metal is machined. Most of the leaded brasses and bronzes are thus considered "free-machining."
Because of their. good machinability. these leaded aDoys lend themselves well to modern high-speed productton methods. Millions of copper alloy castings are machined each year OD turrec lathes, automatic screw machines and other mgh-speed production devices. In many cases the ability to machine at high speed is the chief factor in the. selection of a copper alloy for a particular application.
Even the high-strength copper alloys that do not contain lead usually have much better than avemge machining properties.
CORROSION RESISTANCE
Of all the commonly available casting metals, the alloys ~f copw per offer the best general corrosion resistance. This unique and important characteristic is onc of the chief reasons why these aUoys are used so extensively in industry_
Virtually al1 aUoys of copper bave good resistance to corrosion. When this characteristic is combined with such other valuable properties as strength, electrical conductivity and machinability, the engineer and designer have a highly useful group of marerials with which to work.
Pure copper is highly resistant to the atmosphere; to natural hot, fresh and salt water; and to all alkaline solutions except those distinctly anunoniacal. In general, the copper alloys retain these inherent resistances.
For exposure to weather, the entire group of alloys behaves excellently. For underground water or gas service all of the tin bronzes, leaded tin bronzes and silicon bronzes are acceptable. In ma~y instances, they are the only alloys specified for water or gas systems, since tin bronze and silicon bronze valves and fit. tings retain good operating characteristics indefinitely in service. Tin bronze has long been a standard alloy for use in sea water. The United States Navy specifies these alloys for equipment such as heat exchangers, condensers, and marine bardware for which sea water corrosion is an important consideration. Manganese or aluminum bronze is used extensively for propeller wheels of an sizes from those for small outboard engines to large wheels weighing over 75,000 pounds.
Copper alloys offer resistance to many chemicals, acid, alkaline or organic. They are widely used in equipment for industrial and chemical plants involving exposure to many types of COrTOsive agents.
Numerous tabulations are avajIable to indicate the materials with which the various groups of copper alloys can be successfully used. However, since corrosion of any metal depends on a variety of conditions, including concentration of the liquid, temperature., agitation, etc., it is difficult and unsafe to generalize.
Virtually al1 aUoys of copper bave good resistance to corrosion. When this characteristic is combined with such other valuable properties as strength, electrical conductivity and machinability, the engineer and designer have a highly useful group of marerials with which to work.
Pure copper is highly resistant to the atmosphere; to natural hot, fresh and salt water; and to all alkaline solutions except those distinctly anunoniacal. In general, the copper alloys retain these inherent resistances.
For exposure to weather, the entire group of alloys behaves excellently. For underground water or gas service all of the tin bronzes, leaded tin bronzes and silicon bronzes are acceptable. In ma~y instances, they are the only alloys specified for water or gas systems, since tin bronze and silicon bronze valves and fit. tings retain good operating characteristics indefinitely in service. Tin bronze has long been a standard alloy for use in sea water. The United States Navy specifies these alloys for equipment such as heat exchangers, condensers, and marine bardware for which sea water corrosion is an important consideration. Manganese or aluminum bronze is used extensively for propeller wheels of an sizes from those for small outboard engines to large wheels weighing over 75,000 pounds.
Copper alloys offer resistance to many chemicals, acid, alkaline or organic. They are widely used in equipment for industrial and chemical plants involving exposure to many types of COrTOsive agents.
Numerous tabulations are avajIable to indicate the materials with which the various groups of copper alloys can be successfully used. However, since corrosion of any metal depends on a variety of conditions, including concentration of the liquid, temperature., agitation, etc., it is difficult and unsafe to generalize.
COLOR OF BRASS
For thousands of years, brass and bronze alloys have been used because of their pleasing colors. The rich warmth of polished brass is familiar to all.
By varying the composition of copper alloys. distinct color changes are possible; established and precise alloying techniques enable modern non-ferrous metal producers to provide ingot of almost any specified metallic color for a wide variety of applications from plumbing fixtures to statuary.
Among the groups of common alloys, the copper~zinc brasses have the well-known golden color, although by varying the zinc content, color gradations from pinks to deep yellow can be produced.
The copper-tin alloys have the true bronze color, as do most
of the I~aded tin bronze alloys. Silicon bronze has a yellow cast when polished. Manganese bronze is normally golden yellow.
Nickel silvers, sometimes called "White Brasses", contain DO silver but are alloys of copper, lead. tin, nickel and zinc. They range from pale yellow to white as the zinc or niekel content is increased. For decorative purposes, the white alloy using 18 to 20 percent nickel is most popular.
By varying the composition of copper alloys. distinct color changes are possible; established and precise alloying techniques enable modern non-ferrous metal producers to provide ingot of almost any specified metallic color for a wide variety of applications from plumbing fixtures to statuary.
Among the groups of common alloys, the copper~zinc brasses have the well-known golden color, although by varying the zinc content, color gradations from pinks to deep yellow can be produced.
The copper-tin alloys have the true bronze color, as do most
of the I~aded tin bronze alloys. Silicon bronze has a yellow cast when polished. Manganese bronze is normally golden yellow.
Nickel silvers, sometimes called "White Brasses", contain DO silver but are alloys of copper, lead. tin, nickel and zinc. They range from pale yellow to white as the zinc or niekel content is increased. For decorative purposes, the white alloy using 18 to 20 percent nickel is most popular.
BEARING PROPERTIES
Brass and Bronze casting alloys are the standard materials for many bearing applications. Properly specified and designed, copper alloy bearings are resistant to deformation, are long~ wearing. and in some cases are able to operate for long periods without lubrication. The copper alloy bearing materia1s are easy to machine within the close toJerances required of modern precision bearing design.
The leaded bronzes are traditional for bearings. They offer the vaJuable combination of soft lead embedded in a harder copper-tin matrix. The lead in these aUoys improves seating qualities, acts as a temporary self-lubricant in case of lubrication failure, and has the quality of embeddability which may save an expensive shaft from scoring because of the presence of abrasive materials.
There are leaded bronze alloys operating successfully in almost every type of bearing application. As examples: 83-7-7-3
Federated MetaUurgical Engineers wilL be pletMed to help you choose the correct copper alloy for your bearing application.
Other important bronze bearing alloys are the copper-tin alloys containing tin in quantities of from 6 to 20 percent. These alloys aro characterized by their unusually high compression strength but should be used only where the design provides for adequate lubrication.
A third important class of brOnze beariDg materials is the. aluminum bronze; which ate able to withstand exceptionally high loads and high speeds and which perform well in difficult sliding operations. Aluminum- bronze bearings must be adequately and consistently lubricated.
The leaded bronzes are traditional for bearings. They offer the vaJuable combination of soft lead embedded in a harder copper-tin matrix. The lead in these aUoys improves seating qualities, acts as a temporary self-lubricant in case of lubrication failure, and has the quality of embeddability which may save an expensive shaft from scoring because of the presence of abrasive materials.
There are leaded bronze alloys operating successfully in almost every type of bearing application. As examples: 83-7-7-3
Federated MetaUurgical Engineers wilL be pletMed to help you choose the correct copper alloy for your bearing application.
Other important bronze bearing alloys are the copper-tin alloys containing tin in quantities of from 6 to 20 percent. These alloys aro characterized by their unusually high compression strength but should be used only where the design provides for adequate lubrication.
A third important class of brOnze beariDg materials is the. aluminum bronze; which ate able to withstand exceptionally high loads and high speeds and which perform well in difficult sliding operations. Aluminum- bronze bearings must be adequately and consistently lubricated.
BRASS AND BRONZE CASTING ALLOYS
Millions of pounds of copper alloy castings are used by industry every month. These readUy available metals provide. unusual combinations of physical and chemical properties which cannot readily be obtained from other types of castings . . . strength greater than that of many iron and steel casting alloys; outstanding ease of machining; a complete range of decorative colors from white to deep bronze; resistance to corrosion by atmosphere and by most alkaline, saline and acid solutions; a wide range of electrical and thermal conductivity. In addition, most copper alloys cast well in the foundry and castings can be obtained from thousands of reliable foundries all over America.
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