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.
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