Cast iron alloys

Alloy cast irons are high strength, hard, and abrasion- and corrosion-resistant materials, and are suitable for high-temperature services. Addition of about 5% nickel causes the formation of martensitic 

Tetble 4.11 Composition and properties of some cast irons 

Approximate composition Tensile strength (MN/m ) Type and uses 

5% Si 170 Silal a growth-resistant iron for high-temperature service 

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Alloy cast irons. Alloy additions are made to cast irons to improve the properties for particular purposes. Alloy cast irons can be used in engineering applications where plain cast iron is unsuitable and may even replace steel for some components such as crankshafts. 

A standard 99.85 collapsible tubes, unalloyed (block) tin products, ejectrotinning, tin-alloyed cast iron, high grade solders... 

Piping—carbon steel, alloy, cast iron, lead-lined, aluminum, copper. Purchasing, expediting, and traffic... 

Tube-side headers for water sei vice are made in a wide variety of materials carbon steel, copper alloy, cast iron, and lead-hned or plastic-lined or specially painted carbon steel. 

Alloy Cast Irons Cast iron is not usually considered corrosion-resistant, but this condition can be improved by the use of various cast-iron alloys. A number of such materials are commercially available. 

The austenitic cast irons are in widespread use in many industries (food, pharmaceutical, petroleum, chemical, petrochemical, pulp and paper, etc.) in mildly corrosive and erosive situations where the life of unalloyed or low-alloy cast iron or steel is short, but the high cost of stainless steel and nonferrous alloys cannot be justified. 

The rotor (forged steel) may or may not be an integral part of the shaft. In any case the material for both rotor and shaft is usually a high-strength alloy cast iron. The rotor has radial slots machined along its entire length. The blades or vanes are of heat-treated phenolic resin, metal, or suitable material to withstand the gas and the pressure fit in these slots. 

The scope of the term stainless steel has not been precisely defined, but for general purposes it may be considered to include alloys whose main constituent is iron but which also contain not less than 10% Cr. As with low-alloy steels, a distinction between low or medium carbon grades and high carbon grades must also be drawn, the latter being more in the nature of alloy cast irons. These are used mainly for oxidation resistance at high temperatures and for applications where abrasion resistance allied to a certain amount of corrosion resistance is required, and will not be considered in this section. 

The austenitic irons have also been shown to exhibit better corrosion resistance than the ferritic irons in sea-water. Tests over long periods of time have shown that Ni-Resist irons of Types 1, 2 and 3 corrode at rates of 0 020 to 0-058 mmy in relatively quiet sea-water. Under similar conditions low alloy cast irons have shown corrosion rates ranging from 0-066 to 0-53 mmy" . The Ni-Resist irons maintain this superiority over a wide variety of conditions (Figs. 3.49 and 3.50) both in stationary and flowing sea-water. In a test lasting 740 days in sea-water moving at l-5m/s low... 

Austenitic cast irons show particularly good corrosion resistance in alkaline environments, even better than that shown by low alloy cast irons. The resistance to corrosion improves with increasing nickel content (Fig. 3.51),... 

Most industrial reactors and high pressure laboratory equipment are built using metal alloys. Some of these same metals have been shown to be effective catalysts for a variety of organic reactions. In an effort to establish the influence of metal surfaces on the transesterification reactions of TGs, Suppes et collected data on the catalytic activity of two metals (nickel, palladium) and two alloys (cast iron and stainless steel) for the transesterification of soybean oil with methanol. These authors found that the nature of the reactor s surface does play a role in reaction performance. Even though all metallic materials were tested without pretreatment, they showed substantial activity at conditions normally used to study transesterification reactions with solid catalysts. Nickel and palladium were particularly reactive, with nickel showing the highest activity. The authors concluded that academic studies on transesterification reactions must be conducted with reactor vessels where there is no metallic surface exposed. Otherwise, results about catalyst reactivity could be misleading. 

Use Lighter flints, ferrous and nonferrous alloys, cast iron, aluminum, nickel, magnesium and copper alloys, getter in vacuum tubes, magnetic alloys. 

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