Brasses

Brass is the most used alloy of copper metal. Normally brass is copper alloyed with zinc. There are two types of this alloy, a-brass and a/ 3-brass. At room temperature, copper can dissolve up to 38% zinc in solid solution. In physical metallurgy this phase is called the a-phase. An alloy with 37% zinc, the most common brass, thus consists entirely of the a-phase, and is also called a-brass. It is used as sheet metal and strip for all types of cold forming. For deep drawing, which is especially difficult for the material, the zinc content is decreased to 30%. 

The color of the alloy depends on the zinc content. A brass with 10% zinc and 90% copper is golden yellow and is used for ornamental applications. 

If the zinc content is increased above 38% a new structural component, the 13-phase, appears. In the composition range 38-45% zinc there is a mixed structure and these alloys are called a/ 3-brass. They have improved strength but reduced corrosion resistance. For special purposes, for example cables in condensers and oil refrigerators, a brass with 40% zinc is used. 

Bronzes are primarily cast alloys and constitute a very diversified group. The prototype is tin bronze, an alloy with 90% Cu and 10% Sn. When the molten alloy solidifies, a number of intermediate phases are precipitated and reinforce the copper matrix. That is the reason why the soft tin metal makes copper harder. 

As well as tin, aluminum, beryllium, nickel and iron are also used in special bronzes. An overview of the bronze family is given in Table 7.7. Only one alloy of each type has been included as an example. 

Brass samples may be prepared by turning on a lathe, provided a subsequent etching is carried out. 

Brass is an alloy of copper and zinc. Sandblasting or other mechanical means of surface preparation may be used. The following procedure combines 

Abrasive blast, using either dry or wet methods. Particle size is not especially critical 

Treat with a 5% solution of sodium dichromate in deionized water 

the characteristics mentioned in connection with copper are basically applicable. 

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The y-brass structure is adopted by a series of alloys with an electron atom ratio of 21 13, e.g. CUjZng, CugAl4., Cu3Sna. 

Fig. 1 The view of the polar display with monitors arcs and control panel for SFT6000N board parameters. Recorded signal is from the eddy current probe moved along in a brass tube of inner diameter 20 mm with 2 mm holes as artificial flaws. SFT6000N card operates with 40 kHz injection voltage firequency.

Figure A2.5.18. Body-centred cubic arrangement of (3-brass (CiiZn) at low temperature showing two interpenetrating simple cubic superlattices, one all Cu, the other all Zn, and a single lattice of randomly distributed atoms at high temperature. Reproduced from Hildebrand J H and Scott R L 1950 The Solubility of Nonelectrolytes 3rd edn (New York Reinliold) p 342.

Figure A2.5.21. The heat eapaeity of an order-disorder alloy like p-brass ealeulated from various analytie treatments. Bragg-Williams (mean-field or zeroth approximation) Bethe-1 (first approximation also Guggenheim) Bethe-2 (seeond approximation) Kirkwood. Eaeh approximation makes the heat eapaeity sharper and higher, but still finite. Reprodueed from [6] Nix F C and Shoekley W 1938 Rev. Mod. Phy.s. 10 14, figure 13. Copyright (1938) by the Ameriean Physieal Soeiety.

Figure A2.5.22 shows [6] the experimental heat eapaeity of p-brass (CiiZn) measured by Moser in 1934. Note that the experimental eiirve is sharper and goes imieh higher than any of the theoretieal eurves in figure A2.5.21 however, at that time it was still believed to have a finite limit.

For example,copper has relatively good corrosion resistance under non-oxidizing conditions. It can be alloyed with zinc to yield a stronger material (brass), but with lowered corrosion resistance. Flowever, by alloying copper with a passivating metal such as nickel, both mechanical and corrosion properties are improved. Another important alloy is steel, which is an alloy between iron (>50%) and other alloying elements such as carbon. 

Kirkendall E O 1942 Diffusion of zinc in a-brass Trans. Metall. Soo. AIME 147 104... 

In certain alloys and under certain environmental conditions, selective removal of one metal (the most electrochemically active) can occur that results in a weakening of the strength of the component. The most common example is dezincification of brass [164, 165]. The residual copper lacks mechanical strength. 

Sheets of galvanised iron are used for roofing, guttering and the like. Alloys of zinc, notably brass, are used extensively. The metal is used m wet and dry Leclanche batteries. 

Figure 2-121. The first brass-wire model of a macromolecule built by Kendrew et al. in 1958 [193],...

The metal is employed to form numerous alloys with other metals. Brass, nickel silver, typewriter metal, commercial bronze, spring bronze, German silver, soft solder, and aluminum solder are some of the more important alloys. 

Genesis mentions that Tubal-Cain, seven generations from Adam, was "an instructor of every artificer in brass and iron."... 

The electrical industry is one of the greatest users of copper. Iron s alloys -- brass and bronze --are very important all American coins are copper alloys and gun metals also contain copper. 

The corrections to be made on the reading are as follows (1) Temperature, to correct for the difference in thermal expansion of the mercury and the brass (or glass) to which the scale is attached. 

For most purposes it is sufficient to assume a density of 8.4 for brass weights, and a density of 0.0012 for air under ordinary conditions. The equation then becomes... 

Brass weights, density = 8.4 Ft or Pt-Ir weights, density = 21.5 A1 or quartz weights, density = 2.7 Gold weights, density = 17... 

The volume is determined by weighing the water, having a temperature of r°C, contained or delivered by the apparatus at the same temperature. The weight of water, w grams, is obtained with brass weights in air having a density of 1.20 mg/mL. 

Acetylene Bromine, chlorine, brass, copper and copper salts, fluorine, mercury and mercury salts, nitric acid, silver and silver salts, alkali hydrides, potassium metal... 

Lead(ll) azide Calcium stearate, copper, zinc, brass, carbon disulfide... 

A 10-mL volumetric pipet was calibrated following the procedure just outlined, using a balance calibrated with brass weights having a density of 8.40 g/cm. At 25 °C the pipet was found to dispense 9.9736 g of water. What is the actual volume dispensed by the pipet ... 

What is the minimum density of a substance necessary to keep the buoyancy correction to less than 0.01% when using brass calibration weights with a density of 8.40 g/cm ... 

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