Brass grades

A 99.5% Cu—0.5% Te alloy has been on the market for many years (78). The most widely used is alloy No. CA145 (number given by Copper Development Association, New York), nominally containing 0.5% tellurium and 0.008% phosphorous. The electrical conductivity of this alloy, in the aimealed state, is 90—98%, and the thermal conductivity 91.5—94.5% that of the tough-pitch grade of copper. The machinahility rating, 80—90, compares with 100 for free-cutting brass and 20 for pure copper. 

AQ grades of zinc slab are used to some degree in brasses and bronzes. In many leaded brass-mill products, the lead originates from the slab zinc the accompanying cadmium is usually acceptable. 

RoUed-zinc products in the form of strip, sheet, wire, and rod have many and varied commercial appUcations. Strip is formed into dry-ceU battery cans, mason jar covers, organ pipes, grommets, eyelets, and many other objects, some of which are subsequentiy brass or chromium plated (jewelry, medaUions, bathroom accessories, etc) (132). The zinc—carbon dry-ceU appUcation accounts for about one half the roUed-zinc consumption in the United States (see Batteries). Sheet zinc is used in photoengraving and also in the constmction of roofing and other architectural uses. Special high grade zinc with a... 

Many shell-and-tube condensers use copper alloy tubes, such as admiralty brasses (those containing small concentrations of arsenic, phosphorus, or antimony are called inhibited grades), aluminum brasses, and cupronickel austenitic stainless steel and titanium are also often used. Utility surface condensers have used and continue to use these alloys routinely. Titanium is gaining wider acceptance for use in sea water and severe service environments but often is rejected based on perceived economic disadvantages. 

Certain conditions, ultimately dictated by economics, make the substitution of more resistant materials a wise choice. Stainless steels (not sensitized) of any grade or composition do not form tubercles in oxygenated water neither do brasses, cupronickels, titanium, or aluminum. However, each of these alloys may suffer other problems that would preclude their use in a specific environment. 

Admiralty brass (70% Cu, 29% Zn, 1% Sn, 0.05% As or Sb) and arsenical aliuninum brass (76% Cu, 22% Zn, 2% Al, 0.05% As) are resistant to dezincification in most cooling water environments. In the recent past, heat exchangers have virtually always been tubed with inhibited grades of brass. Brasses containing 15% or less zinc are almost immune to dezincification. Dezincification is common in uninhibited brasses containing more than 20% zinc. Inhibiting elements include arsenic, antimony, and phosphorus. Without inhibiting elements. 

The dezincification was caused by underdeposit corrosion. The fact that the brass was not an inhibited grade was a major contributing factor. Chemical cleaning had not been done since this exchanger was installed. No chemical treatment was used on either external or internal surfaces. 

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. 

Contact of brass, bronze, copper or the more resistant stainless steels with the 13% Cr steels in sea-water can lead to accelerated corrosion of the latter. Galvanic contact effects on metals coupled to the austenitic types are only slight with brass, bronze and copper, but with cadmium, zinc, aluminium and magnesium alloys, insulation or protective measures are necessary to avoid serious attack on the non-ferrous material. Mild steel and the 13% chromium types are also liable to accelerated attack from contact with the chromium-nickel grades. The austenitic materials do not themselves suffer anodic attack in sea-water from contact with any of the usual materials of construction. 

The effective shielding of the detector system from direct and cascade radiation from the Co/Rh source is also very important. A graded shield consisting of concentric tubes of brass, tantalum, and lead was selected. The thickness and the shape of different parts of the shielding were optimized so that nearly zero direct 122 and 136 keV radiation (emitted by the Co source) was in a direct line with the detectors (see Fig. 3.16). 

Copper is attacked by mineral acids, except cold, dilute, unaerated sulphuric acid. It is resistant to caustic alkalies, except ammonia, and to many organic acids and salts. The brasses and bronzes have a similar corrosion resistance to the pure metal. Their main use in the chemical industry is for valves and other small fittings, and for heat-exchanger tubes and tube sheets. If brass is used, a grade must be selected that is resistant to dezincification. 

Figure 2 is a detail of the sloped wood cap used in Figure 1. Note that the joints are taped (at the top of the cant) and caulked (between the lead flooring and wood cant) to keep manufacturing components and product out of joints. The tape material is 3 inch wide, 2 ply, 100 percent cotton, grade B fabric with a warp and fill of approximately 78 x 78 x 72 pounds breaking strength. It should be adhesive-applied using a water insoluble nitrile rubber/ resin solution. These are commonly referred to as "Airplane Fabric" and "Pliobond 20" adhesive. The Fiberfrax Paper is used below lead flooring as an insulation barrier with a low thermal conductivity to resist heat required for installation of lead conductive floor. Note also that nonsparking nails are required. These are usually aluminum or brass.

In the closing years of the production of calamine brass, the following grades of brass are recorded by Aitken (1866) ... 

By the 19th Century, several grades of brass seem to have been in common use, although there is sometimes confusion between the terms employed (from Day and Tylecote, 1991, with additions) ... 

Black powder is the oldest explosive in history, dating back to the eighth century. Its chemical composition is well-known as a mixture of potassium nitrate, sulfur, and charcoal. The mixture ratio is varied according to the purpose for which it is to be used, with the ranges kno3(0-58-0.79), (0.08-0.20), and ( (0.10-0.20). Black powder composed of particles less than 0.1 mm in diameter is used for shell burst of fireworks and fuses. The grade with diameter 0.4—1.2 mm is used for the launch of spherical shells of fireworks, while that with diameter 3-7 mm is used in stone mines. Since black powder is sensitive to sparks caused by mechanical impact, friction, and static electricity, black powder containers should be made of brass or aluminum alloys rather than iron or steel. When Cl and Ca or Mg are present as impurities, CaClj or MgClj is formed and the thermal performance of KN is reduced. Contamination with NaCl also needs to be avoided for the same reason. 

Figure 2 ( ). These coefficients were determined when the following tubes were installed in the evaporator 2 copper, 1 Admiralty, 1 Ampco Grade 8, 2 aluminum brass, and 1 cupronickel. Each tube was 2 inches in outside diameter and 24 feet long, and had a 0.109-inch wall. The dashed curve of Figure 2 shows the heat transfer coefficients that were assumed in preparing the original estimates. In these tests, temperature differences...

Grade S Density Surface area Surface finish Surface protection Magnetic properties Corrosion resistance Hardness 7.7-8.1 g/cm3 (for 50 mg and larger) Not to exceed that of a cylinder of equal height and diameter Highly polished None permitted No more magnetic than 300 series stainless steels Same as 303 stainless steel At least as hard as brass... 

Fig. 2. Taper sections of a brass surface abraded on l/0 grade emery paper. Taper ratio 8.2. (a) Etched in ferric chloride reagent and showing the inhomogeneous distribution of the deformation close to the surface. X 100G before reduction for publication, (b) Etched to develop slip-line traces, showing the full extent of the plastically deformed layer. X 25(4 before reduction for publication. The fragmented layer, which is more clearly shown in Fig. 1, is also discern-able in these micrographs.

Fig. 5. Estimate of the strain gradient in a brass surface abraded on 600-grade silicon carbide paper.

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