Brass, types

The Hume-Rothery types listed in Table 4.6 include structures of different complexity ranging from the simple close-packed (fee and hep) and bcc structures to the more complex Mn-type and 7-brass type structures. As for the hexagonal hep structures, notice that for this type several variations are known three branches of this structure are generally considered. The (-hep corresponds to the true closest packing with the value of the axial ratio da close to the ideal one ((8/3) = 1.6329. .. (see 3.7.4 and Fig. 3.16). The e-hex corresponds to da ranging around 1.55 to 1.58 and the r/ phase to c/a values of about 1.77 to 1.88. As observed by Lee and Hoistad (1995), the various hexagonal types can be considered genuinely different. 

The Cu5Zn8 ( Cu5Zn6 9 — Cu5Zn9 7) phase is a classical example of a Hume-Rothery phase ( electron compounds , brass-type phases) that is of a phase in which there is a structure-determining influence of the VEC (valence electron concentration, see 4.4.5). 

The CsCl structure (Fig. 1.5) consisting of interpenetrating primitive cubic arrays of Cs and Cl ions with 8 8 coordination is exhibited by many solids (a) CsCl, CsBr and Csl (b) NH4.CI, NH Br and NH I in their low-temperature modification (c) thallous halides (d) alloys of ) -brass type, CuZn, AuZn (e) CuCN, CuSH and TICN in their high-temperature form and (1) alkali halides (with the exception of lithium salts) at high pressures. 

The ratio 21 /13 is characteristic of compounds of the y-brass type (CuZn) and 7/4 for the e-brass type (CuZn3) (Hume-Rothery compounds). 

Since the early days of texture research the fact that fee metals and alloys develop two different types of rolling texture, the copper type and the brass type, has been a mystery to the texture community. One may say that it is the classical texture problem. As mentioned in section 1 it was already in the nineteensixties suggested, on the basis of circumstantial evidence, that the texture transition is governed by cross slip. In 1968 one of the present... 

The structure is suggested to be probably related to the CsCl or / -brass type. 

Lead is also a component in some steel and brass types ... 

Brass type Corrosion rate Depth of (pm/year) dezincification pits/m ... 

CeU terminal connections are usuaUy brought out by two-threaded terminals that protmde through the ceU jar cover. They are usuaUy steel, brass, or copper with a hoUow coastmctioa. The plate leads are soldered ia place ia the ceater hoUow portioa of the terminal to effect an electrical contact and ceU seal. The terminal itself is potted iato the jar cover usiag epoxy-type pottiag compouads. NormaUy, terminal hardware is sUver-plated. However, for corrosioa resistance nickel-plating has been used. 

Clad tube eets in service with carbon steel backer material include stainless-steel types 304, 304L, 316, 316L, and 317, Monel, Inconel, nickel, naval rolled brass, copper, admiralty, silicon bronze, and titanium. Naval rolled brass and Monel clad on stainless steel are also in service. 

Metal Fabrics or Screens These are available in several types of weave in nickel, copper, brass, bronze, aluminum, steel, stainless steel. Monel, and other alloys. In the plain weave, 400 mesh is the closest... 

Parting, or Dealloying, Corrosion This type of corrosion occurs when only one component of an alloy is removed by corrosion. The most common type is dezincification of brass. 

Dezincification Dezincification is corrosion of a brass alloy containing zinc in which the principal product of corrosion is metallic copper. This may occur as plugs rilling pits (plug type) or as continuous layers surrounding an unattacked core of brass (general type). The mechanism may involve overall corrosion of the alloy followed by redeposition of the copper from the corrosion products or selective corrosion of zinc or a high-zinc phase to leave copper residue. This form of corrosion is commonly encountered in brasses that contain more than 15 percent zinc and can be either eliminated or reduced by the addition ox small amounts of arsenic, antimony, or ph osphorus to the alloy. 

Figure 13.1 Layer-type dezincification on a brass casting. The red layers are uniformly corroded regions. The original yellow of the brass is visible in between.

Layer-type dezincification is easy to recognize visually. The original component shape and dimensions are usually preserved, but the metal color changes from the golden yellow of zinc brass to the red of ele-... 

Flgure 13.2 Layer-type dezincification of a thin brass plate. The 0.019-in. (0.048-cm) plate is shown in cross section. The dezincified layers converge toward the plate edge. Note the porosity of the dezincified metal. 

Figure 13.3 Layer-type dezindfication on the internal surface of a cast brass pipe 90° elbow.

Figure 13.5 Plug-type dezincification on the internal surface of a brass condenser tube. Note the extreme porosity of the copper plugs. Tube wall thickness was 0.040 in. (0.10 cm). Compare to Fig. 13.13. (Courtesy of National Association of Corrosion Engineers, Corrosion 89 Paper No. 197 by H. M. Herro.)...

Figure 13.8 A brass tube showing plug-type dezincification. The white patch above the plug on the external surface was caused by dissolved solids, concentrated by evaporation of water leaking through the porous dezincified plug.

Figure 13.10 A hole emanating from the internal surface of a brass condenser tube. The hole was caused by plug-type dezincification (see Fig. 13.11).

The more severe metal loss adjacent to the brass nozzles is apparently due to a direct galvanic interaction between the aluminum ring and the brass nozzles. The type of exfoliation observed microscopically in corroded areas is consistent with galvanic attack. 

Alloys of nonferrous metals, primarily the brasses (copper and zinc) and the bronzes (copper and tin), can cause an air pollution problem during melting and casting. The type and degree of emissions depend on the furnace and the alloy. Control systems consist of hoods over the furnaces and pouring stahons to collect the hot gases, ducts and fans, and baghouses or ESPs. 

The valve was made of brass and was of a type stocked for use on domestic water systems. It was not the correct pressure rating for LFG. 

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