CHAPTER II 

 THE BRASSES 



The most widely used and the best-known copper-base 

 alloys are those with zinc known as "the brasses." Copper 

 and zinc together form a complete series of solid solu- 

 tions. As zinc is added to copper, tensile properties 

 increase, electrical and thermal properties decrease, and 

 some diminution of resistance to the action of most 

 corrosive media results. 



Brasses are commonly used in applications where it is 

 desired to improve upon some specific characteristic of 

 copper, and where such improvement may be effected at 

 a sacrifice only of such characteristics of copper as are 

 unimportant in respect to the particular application at 

 hand. 



Commonly, certain mill products and certain manu- 

 factured products may be produced at lower cost if, 

 instead of copper, certain of the brasses are used. Obvi- 

 ously therefore, cost frequently is the consideration that 

 leads to the use of brass rather than copper for a given 

 product. 



In general the brasses offer mechanical properties 

 superior to those of copper; the advantage in this respect 

 being gained at a sacrifice of both electrical and thermal 

 conductivities. 



There are two broad classifications of the alloys of 

 copper and zinc: one containing from 64 to 99 per cent 

 of copper, consisting of a single phase and known as 

 "alpha" brasses; the other containing from 55 to 64 per 

 cent of copper, containing two phases and knowm as the 

 "alpha-beta" brasses. The alloys of copper and zinc 

 containing less than 55 per cent of copper, owing to the 

 predominance of the beta phase, are brittle and of no 

 commercial significance. 



ALPHA BRASSES 



Cold Working. — The alpha brasses are exceptionally 

 ductile and malleable at room temperature and can be 

 cold-worked by any of the commercial methods such as 

 deep drawing, spinning, stamping, forming, cold rolling, 

 cold heading, flaring, and upsetting. 



As the brasses are cold-worked, they become increas- 

 ingly hard; the degree of hardness being dependent on 

 the amount of cold work and the copper content of the 

 alloy. The alpha brasses containing in excess of 85 per 

 cent of copper have work-hardening properties similar to 

 those of copper. Those containing between 64 and 

 85 per cent of copper work-harden less rapidly than those 

 of higher copper content. Because of this property 

 these brasses are used extensively for applications 

 requiring successive drawing operations without inter- 

 mediate anneals. 



Annealing. — After cold-working operations, the brasses 

 can be rendered malleable or ductile again by heat- 

 treatment at temperatures ranging from 700 to 1400°F., 

 depending upon the properties desired. 



Since the alpha brasses are single-phase alloys, they 

 are not susceptible of hardening by heat-treatment. 



Hot Working. — Those alpha brasses containing be- 

 tween 64 and 80 per cent of copper possess relatively 

 poor hot- working properties. In order to hot-roll or 

 hot-forge these alloys successfully the utmost care must 

 be taken to keep lead, a natural impurity of most zinc, 

 to a trace. (The presence of even 0.03 per cent of lead 

 causes these alloys to crack at any hot-working temper- 

 ature.) Brasses of this group are best hot-worked at 

 temperatures in excess of 1350°F. ; the best results are 

 secured if all hot working is done within the range of 

 1350 to 1550°F. 



The alpha brasses containing 80 per cent or more of 

 copper have hot-working properties comparable to those 

 of copper, which is extremely plastic through a wide tem- 

 perature range. However, as in the case of copper, care 

 must be exercised to control the lead to within very close 

 limits. As a general rule, if these brasses do not con- 

 tain in excess of 0.01 per cent of lead, they can be hot- 

 forged, hot-rolled, or otherwise hot-worked without any 

 difficulty. 



Physical Properties — General. — In the alpha range, 

 tensile properties increase with increasing zinc content, 

 which is also accompanied by a change of color from red 

 through gold to the green yellows and a progressive 

 diminution of electrical and thermal conductivites. 



Corrosion Resistance. — Alpha brasses are, for the 

 most part, adversely affected by the same substances 

 and the same conditions that have an adverse effect on 

 copper. In some instances they may be corroded by 

 substances, particularly those which might be termed 

 "active chemical reagents," that do not affect copper to 

 any appreciable extent. An exception to this generality 

 is that in resisting the corrosive attack of sulphides the 

 brasses, on the whole, are better than copper, and their 

 superiority in that respect becomes more marked as the 

 zinc content increases. Further, it is of particular inter- 

 est that in combating the corrosion of sea water certain 

 of the brasses, e.g., 85-15 brass (known as "rich low" or 

 "red brass") gives materially better service in respect to 

 withstanding corrosion than copper itself. 



Brasses containing less than 85 per cent of copper, 

 when exposed to certain media, frequently fail in a 

 characteristic manner termed "dezincification." Fail- 

 ures of this kind are identified by the appearance of 



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