Austenitic steels

Fig. 19. Effect of cooling rate on structure of a eutectoid steel. = austenitizing temperature > = austenite phase.

Stainless steel, austenitic IS Cr S Ni types 0 2 0 3 < 400 Wronglit, cast, clad Good Good 90 9.6 AlSl type 304 ASTM corrosion- and heat-resisting steels stabHi2ed or LC types used for welding... 

The austenitic irons can be usefully applied in handling very dilute solutions of sulphuric acid at ambient or moderately elevated temperatures under conditions which can be very corrosive to ordinary cast iron and carbon steel. Austenitic irons have also given satisfactory service in handling... 

Carbon Carbon-manganese, low alloy steels Austenitic stainless steels Non-ferrous metals... 

High alloy steels, austenitic All All All All None None ... 

Materials suitable for liquid oxygen service are nickel steel, austenitic stainless steels, and copper or aluminium alloys. Carbon steels and plastics are brittle at low temperatures and should not be used on liquid oxygen duty. PTFE is the most widely used sealant. 

A preliminary approach to the selection of the stainless steel for a specific application is to classify the various types according to the alloy content, microstructure, and major characteristic. Table 3 outlines the information according to the classes of stainless steels-austenitic, martensitic, and ferritic. Table 4 presents characteristics and typical applications of various types of stainless steel while Table 5 indicates resistance of stainless steels to oxidation in air. 

Stainless steel, austenitic 3 3 4 <400 Wrought, cast Cood Good 90 9.4 ACI CH-7M good resistance to sulfuric, phosphoric, and fatly... 

Whether decarburization will be an issue for internal combustion engines burning H2 is difficult to predict from existing information. Low-alloy carbon steels begin to decarburize at temperatures around the operating temperature of exhaust valves, but exhaust valves and valve seats are made from high-alloy steels, austenitic alloys, and superalloys where the carbon is much more stable than low-alloy carbon steels. The hardenable martensitic valve stems of exhaust valves may experience decarburization over extended periods, and this would lead to accelerated wear because of the softened surface that results from decarburization. 

No Attraction Commercially pure nonferrous metals (except nickel and cobalt) Copper-nickels Hastelloys, Inconels, Incoloys Stainless steels austenitic, austenitic precipitation hardening Stellite... 

Environment Aluminum alloys Carbon steels Copper alloys Nickel alloys Stainless steels Austenitic Duplex Martensitic Titanium Zirconium alloys alloys... 

There are four main classes of stainless steel (austenitic, ferritic, ferritic-austenitic (duplex) and martensitic), and within these, a variety of different grades. The names ferritic and austenitic follow from their structures ferrite (P-Fe) and austenite (y-Fe) lattices hosting the alloying elements. The presence of Cr promotes the formation of the ferrite structure, while the austenite lattice forms when Ni is introduced. While ferritic and martensitic stainless steels are magnetic, austenitic stainless steel is non-magnetic. Further additives to some stainless steels are molybdenum (which improves corrosion resistance) and nitrogen (which adds strength and improves corrosion resistance). 

Stainless Steel. Austenitic stainless steels of the AISI 300 series are well suited for low temperature service by their strength and impact resistance properties. They are easy to weld, have a low heat conductivity and require no stress relief. Partially offsetting these factors is their higher cost. The commonly-used analyses of stainless steel are available in thin wall piping schedules 5S and lOS as well as in the normal schedules. Thinner walls are allowable for stainless steel because it is not subject to corrosion. All of its thickness is available for strength. 

FERRITIC (Fe-Cr) STAINLESS STEELS AUSTENITIC (Fe-Ni-Cr) STAINLESS STEELS... 

Refractory metal tools have been used to weld low-carbon steels, carbon-manganese steels, austenitic stainless steels, and ferritic stainless steels. 

Superabrasive tools, primarily PCBN, have been used to successfully weld ferritic steels, ferritic stainless steels, austenitic stainless steels, nickel-base superalloys. Invar, and Narloy-Z. Attempts to weld titanium with PCBN tools have been inconclusive. Tool life of 80 m (260 ft) has been demonstrated in FSW of 1018 steel, and very low tool wear has been reported on all other alloys. The primary concern in tool life continues to be fracture, and developments in PCBN grades continue to improve the fracture toughness of the FSW tools. The PCBN tools provide an extremely smooth finish when used for FSW or FSP. 

Low-carbon steel, high-strength steels Austenitic stainless steels a-Brass Titanium alloys (8% Al, 1% Mo, 1% V) Aluminum alloys Solutions containing NOj, OH , H2O Solutions containing Cl , OH , Br NH3, amines Solutions containing Cl , Br , H2O, NaCl solutions... 

For a number of stress corrosion cracking systems, e.g., mild steel, austenitic stainless steels, measured bare surface current densities appear to be of the right order of magnitude ( ). For other alloys, e.g.,... 

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