Brass ductility

The bellows is formed from a length of thin-walled tubing by extmsion in a die. The metals used in the constmction of the bellows must be ductile enough for reasonably easy fabrication and have a high resistance to fatigue failure. Materials commonly used are brass, bronze, beryllium copper, alloys of nickel and copper, steel, and Monel (5). 

Antimony may be added to copper-base alloys such as naval brass. Admiralty Metal, and leaded Muntz metal in amounts of 0.02—0.10% to prevent dezincification. Additions of antimony to ductile iron in an amount of 50 ppm, preferably with some cerium, can make the graphite fliUy nodular to the center of thick castings and when added to gray cast iron in the amount of 0.05%, antimony acts as a powerflil carbide stabilizer with an improvement in both the wear resistance and thermal cycling properties (26) (see Carbides). 

Temperature, op Carbon steel, carbon-molybdenum low-chromium (through 3 Cr Mo) 5Cr Mo through 9 Cr Mo Austenitic stainless steels, 18 Cr, 8 Ni 12 Cr 17 Cr 27 Cr 25 Cr, 20 Ni Monel 67 Ni, 30Cii 3V2 Nickel Aluminum Gray cast iron Bronze Brass 70Cii, 30 Ni Ni-Fe-Cr Ni-Cr-Fe Ductile iron... 

Brasses with up to 15 percent Zn are ductile but difficult to machine. Machinability improves with increasing zinc up to 36 percent Zn. Brasses with less than 20 percent Zn have corrosion resistance eqmvalent to that of copper but with better tensile strengths. Brasses with 20 to 40 percent Zn have lower corrosion resistance and are subject to dezincincation and stress-corrosion cracking, especially when ammonia is present. 

The outstanding properties of copper-base materials are high electrical and thermal conductivity, good durabihty in mildly corrosive chemical environments and excellent ductility for forming complex shapes. As a relatively weak material, copper is often alloyed with zinc (brasses), tin (bronzes), aluminum and nickel to improve its mechanical properties and corrosion resistance. 

The strength and ductility of brasses are well maintained over a range of 300° to -180°C, and castings are easy to make as well as to machine. Brass behaves similarly to copper in chemical plant environments, with somewhat greater rates of attack. 

The characteristic mode of corrosion of some alloys may be the formation as a corrosion product of a redeposited layer of one of the alloy constituents, as in the case of the brasses that dezincify, or of a residue of one of the components, as in the case of the graphitic corrosion of cast iron. Particularly in the case of the dezincified brass, the adherent copper is not likely to be removed with the other corrosion products, and therefore the mass-loss determination will not disclose the total amount of brass that has been corroded. This is especially important because the copper layer has very little strength and ductility and the extent of weakening of the alloy will not be indicated by the mass loss. In these cases, also, the mass-loss determinations must be supplemented by, or replaced by, mechanical tests or metallographic examination, or both, to reveal the true extent of damage by corrosion. Difficulties in obtaining accurate mass losses of heavily graphitised specimens have been reported... 

They consist of metallic (such as of brass) containers filled with an expl chge which has a resistance of 10-200 ohms and which fires in 10-100 msec upon passage of an electric current of 100 to 500 thousand ergs. One of the preferred expl compns is fine LA 70 elec conducting powd (consisting essentially of amorphous C graphite) 30%. For use with fasteners of low ductility ca 8% heat-sensitive expl diluent such as Tetra-... 

Figure 5.18 Influence of annealing temperature on tensile strength and ductility of a brass alloy. Grain structures during recovery, recrystallization, and grain growth are shown schematically. Reprinted, by permission, from W. Callister, Materials Science and Engineering An Introduction, 5th ed., p. 175. Copyright 2000 by John WUey Sons, Inc.

Metal powder can also be coated onto the workpiece. The 3M Company has developed a cold welding technique in which the workpiece, the metal powder, water, glass shot and additives are tumbled together in a barrel. Coatings are limited to ductile metals such as Cd, An, Sn, Pb, In, Ag, Cu, brass, and tin/lead solder the method is generally suitable only for small parts, and it doesn t produce a fine surfaced, cosmetic coating. Costs are comparable to those for electroplating with afterbake (Kirk-Othmer 1981). 

When lead is added to brass up to about 4%. improved machinabtlity results. The lead has practically no effect on tensile strength or hardness. However, for cold-worked materials, lead does lower ductility and shear strength. 

The valves used in propane systems must be made from steel, ductile (nodular) iron, malleable iron, or brass. Soft parts of these valves such as gaskets, valve seat disks, packing, seals, and diaphragms must be made of materials that are certified by the manufacturer to be compatible with propane. Valve pressure ratings shall be consistent with the pressures observed in the intended application [3.14]. 

Metals that remain ductile at very low temperatures are preferred for use with liquid hydrogen. Examples include aluminum, copper, Monel, Inconel, titanium, austenitic stainless steels, brass, and bronze [3.19]. 

Copper is a tough, soft, and ductile reddish metal, second only to Ag in its high thermal and electrical conductivities. It is used in alloys such as brasses and is completely miscible with Au. It is only superficially oxidized in air, sometimes acquiring a green coating of hydroxo carbonate and hydroxo sulfate. 

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