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Muntz Metal An Analysis of Muntz Metal’s properties and its Application as a Building Material
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Muntz Metal= 60% copper + 40% Zinc + small amount of iron
The purpose of adding alloying elements to copper is to optimize the strength, ductility (formability), and thermal stability, without inducing unacceptable loss in fabric ability, electrical/thermal conductivity, or corrosion resistance. The existence of impurities and all common alloying elements, except for silver, will decrease the electrical and thermal conductivity of copper.)
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Mechanical Properties
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Hardness Muntz Metal Metric English Comments Hardness, Rockwell F 80
Bronze Metric English Comments Hardness, Rockwell F Average value: 68.0 Grade Count:37 Stainless Steel Metric English Comments Hardness, Rockwell F >> Indentation hardness measures the resistance of a sample to permanent plastic deformation due to a constant compression load from a sharp object Rockwell F: 1/16 inch Brale indenter60 kg load >> The hardness value is above the acceptable range of the particular hardness scale. Mechanical Properties Metric English Comments Hardness, Brinell Average value: 168 Grade Count:93 Hardness, Rockwell B Average value: 88.4 Grade Count:139 Hardness, Rockwell C Average value: 33.5 Grade Count:12 Hardness, Rockwell F Average value: 68.0 Grade Count:37 Hardness, HR30T Average value: 50.6 Grade Count:26 Tensile Strength, Ultimate MPa psi Average value: 485 MPa Grade Count:302 Tensile Strength, Yield MPa psi Average value: 290 MPa Grade Count:256 Elongation at Break % Average value: 23.4 % Grade Count:297 Reduction of Area % Average value: 28.6 % Grade Count:33 Modulus of Elasticity GPa ksi Average value: 109 GPa Grade Count:256 Compressive Yield Strength MPa psi Average value: 655 MPa Grade Count:59 Poissons Ratio Average value: Grade Count:188 Charpy Impact J ft-lb Average value: 33.4 J Grade Count:53 Izod Impact J ft-lb Average value: 36.0 J Grade Count:48 Fatigue Strength MPa psi Average value: 201 MPa Grade Count:70 Machinability % Average value: 32.7 % Grade Count:200 Shear Modulus GPa ksi Average value: 42.3 GPa Grade Count:188 Shear Strength MPa psi Average value: 297 MPa Grade Count:102
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Sheer Strength Stainless Steel Metric English Comments Shear Modulus
62.1 – 86.0 Gpa ksi Average value: 78.2 GPa Grade Count:269 Bronze Metric English Comments Shear Modulus GPa ksi Average value: 42.3 GPa Grade Count:188 Muntz Metal Metric English Comments Shear Modulus 39.0 GPa 5600 ksi The shear modulus is concerned with the deformation of a solid when it experiences a force parallel to one of its surfaces while its opposite face experiences an opposing force (such as friction). It is defined as "the ratio of shear stress to the displacement per unit sample length (shear strain)" .
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Shear Modulus Stainless Steel Metric English Comments Shear Modulus
62.1 – 86.0 Gpa ksi Average value: 78.2 GPa Grade Count:269 Bronze Metric English Comments Shear Modulus 62.1 – 86.0 Gpa ksi Average value: 78.2 GPa Grade Count:269 Muntz Metal Metric English Comments Shear Modulus 62.1 – 86.0 Gpa ksi Average value: 78.2 GPa Grade Count:269 Shear Modulus is the coefficient of elasticity for a shearing force. It is defined as "the ratio of shear stress to the displacement per unit sample length (shear strain)" the shear modulus describes the material's response to shearing strains. It is the description of an object’s tendency to be deformed elastically.
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Thermal Conductivity (in/hr*ft²*°F)
Muntz Metal Stainless Steel Cast Iron 11.5 9.6 6.0
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Thermal Expansion (in²/°F x 10^-6)
Muntz Metal Stainless Steel Bronze 852 105.6 180
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Specific Heat Capacity
Stainless Steel Metric English Comments Specific Heat Capacity J/g-°C BTU/lb-°F Average value: J/g-°C Bronze Metric English Comments Specific Heat Capacity J/g-°C BTU/lb-°F Average value: J/g-°C Muntz metal Metric English Comments Specific Heat Capacity 0.375 J/g-°C BTU/lb-°F
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Corrosion Resistance Copper corrodes at negligible rates in unpolluted air, water, and desecrated non-oxidizing acids. Copper alloy artifacts have been found in nearly pristine condition after having been buried in the earth for thousands of years, and copper roofing in rural atmospheres has been found to corrode at rates of less than 0.4 mm in 200 years. Copper alloys resist many saline solutions, alkaline solutions, and organic chemicals. However, copper is susceptible to more rapid attack in oxidizing acids, oxidizing heavy-metal salts, sulfur, ammonia (NH3), and some sulfur and NH3 compounds Brasses (C C 28580) are basically copper-zinc alloys and are the most widely used group of copper alloys. The resistance of brasses to corrosion by aqueous solutions does not change markedly as long as the zinc content does not exceed about 15%. Above 15% Zn, dezincification may occur.
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Dezincification Dezincification results in a porous, reduced ductility, reddish copper matrix. What remains may support a given load until an increase of pressure or weight exceeds the local ductility and causes fracture. Soft, stagnant, or slow moving waters or saline solutions can lead to dezincification of unmodified brasses. The brasses may be more prone to dezincification in stressed regions (for example, in the bent region of a float arm on a water closet fixture) or where a bend exists (as in an elbow in a fresh water supply line). High zinc content introduces the possibility of stress-corrosion cracking. Very high zinc content, as in Muntz metal, may lead to excessive corrosion attack in seawater due to dezincification. (Limited or no data are available on the effects of zinc in brasses on the rate of corrosion; however, the addition of tertiary and quaternary elements is known to enhance the resistance of zinc-containing alloys to certain environments.)
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Stress corrosion cracking (SCC)
Stress Corrosion Cracking is cracking due to the process involving conjoint corrosion and straining of a metal due to residual or applied stresses SCC is the growth of cracks in a corrosive environment. It can lead to unexpected sudden failure of normally ductile metals subjected to a tensile stress, especially at elevated temperature in the case of metals.
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The SCC environment of Muntz
Alloys at the higher zinc levels of 35 to 40% Zn contain the bcc beta phase, especially at elevated temperatures, making them hot extrudeable and forgeable. When subjected to the combined effects of stress and corrosion, many alloys can develop cracks over a period of time and specifically copper-zinc alloys such as brass can be sensitive to stress corrosion attack, particularly in the presence of moisture through condensation. However, SCC occurs only in the presence of a sufficiently high tensile stress and a specific corrosive environment. For brasses, the environment involved is usually one containing ammonia or closely related substances such as amines.
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