Brass illustration

Table 16 illustrates the property enhancements and tradeoffs seen when tin is added to a copper—zinc brass base composition. The most commonly used alloys for electrical connectors are the Cu—10 Zn—Sn brasses, such as C411, C422, and C425. These lower level zinc—tin alloys offer good corrosion resistance along with the good formabiHty, conductivity, and strength levels of brass. 

This case history dramatically illustrates the value of proper alloy choice. It was found that the failed exchanger had been ordered many years ago but was not installed until recently. Today, uninhibited grades of brass are almost never used for condenser and heat exchanger service in the United States. 

Demonstrations Take a strip — 0.25 mm X 1 cm X 15 cm of cold-rolled (work-hardened) brass and bend it (on edge) on the overhead until permanent deformation takes place. Anneal brass strip at bright red head for — 0.5 min to soften it. After cooling replace on overhead and show that permanent deformation takes place at a much smaller deflection than before. This illustrates the importance of large Uy in springs. 

A survey of the literature (see pages 1.114 to 1.117) shows that numerous workers in the field of corrosion have used potential-pH diagrams in order to throw more light on the mechanism of a corrosion process. As an example, some consideration will be given to the stress corrosion of a-brass, which also serves to illustrate diagrams of the type where in... 

This example of aluminium illustrates the importance of the protective him, and hlms that are hard, dense and adherent will provide better protection than those that are loosely adherent or that are brittle and therefore crack and spall when the metal is subjected to stress. The ability of the metal to reform a protective him is highly important and metals like titanium and tantalum that are readily passivated are more resistant to erosion-corrosion than copper, brass, lead and some of the stainless steels. There is some evidence that the hardness of a metal is a signihcant factor in resistance to erosion-corrosion, but since alloying to increase hardness will also affect the chemical properties of the alloy it is difficult to separate these two factors. Thus althou copper is highly susceptible to impingement attack its resistance increases with increase in zinc content, with a corresponding increase in hardness. However, the increase in resistance to attack is due to the formation of a more protective him rather than to an increase in hardness. 

Only certain specific environments appear to produce stress corrosion of copper alloys, notably ammonia or ammonium compounds or related compounds such as amines. Mercury or solutions of mercury salts (which cause deposition of mercury) or other molten metals will also cause cracking, but the mechanism is undoubtedly differentCracks produced by mercury are always intercrystalline, but ammonia may produce cracks that are transcrystalline or intercrystalline, or a mixture of both, according to circumstances. As an illustration of this, Edmundsfound that mercury would not produce cracking in a stressed single crystal of brass, but ammonia did. 

FIGURE 40 Patina. Patina is a colored (usually green) layer of corrosion products that frequently develops naturally on the surface of copper and copper alloys exposed to the environment. Since it is sometimes appreciated aesthetically and as a proof of age, patina is also developed artificially, by chemical means, as a simulated product of aging. Copper patina generally includes such compounds as copper oxides, carbonates, and chlorides. In bronze and brass patinas, these compounds are mixed with the oxides of tin and lead resulting from the corrosion of the other components of the alloys. In any particular patina there may be many layers, not necessarily in the order shown in the illustration. 

Electrodeposited binary alloys may or may not be the same in phase structure as those formed metallurgically. By way of illustration, we note that in the case of brass (Cu-Zn alloy), x-ray examination reveals that apart from the superstructure of... 

We now return to the case of codeposition of metals whose standard electrode potentials are wide apart. As stated, the deposition potentials [Eq. (11.2)] are brought together by complexing the more noble metal ions, as illustrated below for the case of the codeposition of copper and zinc as brass. 

As an illustration of the use of electrode potentials, consider the classical method of analysis of copper in brass, which involves dissolving the weighed sample in nitric acid to obtain Cu2+(aq), adjusting the pH to a weakly acidic level, allowing the Cu2+ to react completely with excess potassium iodide to form iodine and the poorly soluble Cul, and then titrating the iodine with sodium thiosulfate solution that has been standardized against pure copper by the same procedure ... 

Fig. 10.15, Metal vacuum systems for handling fluorine and reactive fluorides, (a) A design used extensively at Argonne National Laboratory constructed of nickel tubing and Monel valves (A) with cone joints (illustrated in Fig. 10.13) (D) nickel U-trap (E) Monel Bourden gauge (0-1000 ion) (F) 130-mL nickel reactor can (Fig. 10.17) (G) 1,500-mL nickel storage or measuring can, (H) 85-mL nickel can, (i) brass valve (K) soda-lime trap to protect vacuum pumps (L) Monel valve. (Reproduced by permission of the copyright holder, The University of Chicago Press, from Nobel Gas Compounds, H. H. Hyman (Ed.), Chicago, 1963.)...

Electrodeposited binary alloys may or may not be the same in phase structure as those formed metallurgically. By way of illustration, we note that in the case of brass (Cu-Zn alloy), X-ray examination reveals that, apart from the superstructure of /3-brass, virtually, the same phases occur in the alloys deposited electrolytically as formed in the melt. Phase limits closely agree with those in the bulk. Debye-Scherrer interference rings indicate the presence of a strong distortion of the lattice, particularly in the a-phase brass. Electrodeposited a-brass, for instance, is... 

Various designs have been developed to magnify the small displacements, at the cost of reduced blocking force. A well known design, the Moonie , is illustrated in Fig. 6.26. The brass end-caps not only follow the -controlled displacement but also redirect the dn displacement into the 3-direction. This magnified displacement can be as much as 20 pm on a 3 mm thick actuator for an applied voltage of as little as 50 V. 

Ball-Centering Guide If desired, center the ball by using a guide constructed of brass and having the general shape and dimensions illustrated in Fig. 40c. 

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