Stainless steel austenitic type

The most widely used austenitic stainless steel is Type 304, known as 18—8. It has excellent corrosion resistance and, because of its austenitic stmcture, excellent ductihty. It may be deep-drawn or stretch formed. It can be readily welded, but carbide precipitation must be avoided in and near the weld by cooling rapidly enough after welding. Where carbide precipitation presents problems. Types 321, 347, or 304L may be used. The appHcations of Types 304 are wide and varied, including kitchen equipment and utensils, dairy installations, transportation equipment, and oil-, chemical-, paper- (qv), and food-processing (qv) machinery. 

Fig. 5. Metastable Fe—Ni—Cr "temary"-pliase diagram where C content is 0.1 wt % and for alloys cooled rapidly from 1000°C showing the locations of austenitic, duplex, ferritic, and martensitic stainless steels with respect to the metastable-phase boundaries. For carbon contents higher than 0.1 wt %, martensite lines occur at lower ahoy contents (43). A is duplex stainless steel, eg. Type 329, 327 B, ferritic stainless steels, eg. Type 446 C, 5 ferrite + martensite D, martensitic stainless steels, eg. Type 410 E, ferrite + martensite F, ferrite + pearlite G, high nickel ahoys, eg, ahoy 800 H,...

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... 

A careful, quantitative study on grain boundary segregation, boron segregation in austenitic stainless steels of types 316L (with 206 at. p.p.m. of boron, and with <5 at. p.p.m. of boron) and Mo-free 316L (75 at. p.p.m. boron), has been reported by Karlsson, Norden, and Andren36 using a combination of TEM, FIM, AP and IAP techniques. Concen-... 

U.K. Standard specification BS6744 1986 Austenitic Stainless Steel Bars (Type 304, 304L, 316 and 316L)... 

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. 

One material that has wide application in the systems of DOE facilities is stainless steel. There are nearly 40 standard types of stainless steel and many other specialized types under various trade names. Through the modification of the kinds and quantities of alloying elements, the steel can be adapted to specific applications. Stainless steels are classified as austenitic or ferritic based on their lattice structure. Austenitic stainless steels, including 304 and 316, have a face-centered cubic structure of iron atoms with the carbon in interstitial solid solution. Ferritic stainless steels, including type 405, have a body-centered cubic iron lattice and contain no nickel. Ferritic steels are easier to weld and fabricate and are less susceptible to stress corrosion cracking than austenitic stainless steels. They have only moderate resistance to other types of chemical attack. 

Figure 6.28 Cathodic partial current density for the reduction of oxygen, of Fe ions, and of Ce ions on an austenitic stainless steel of type AISI304 in 5% H2SO4. Concentration of the oxidizing agents (3/n) mM 1 (n= charge number). Dashed hne anodic partial current density [30].

Ferritic stainless steel has the reputation of being less sensitive to intergranular corrosion than austenitic stainless steel. This type of corrosion can nevertheless take place under certain conditions of thermal treatment [20]. The diffusion coefficients of both carbon and chromium in ferrite are larger than in austenite. Grain boundary precipitation of carbides and nitrides of chromium can therefore occur at temperatures of 540-600 °C already. The behavior differs from that of austenitic stainless steel, which becomes sensitized at higher temperatures only. Because of the larger diffusion... 

IGSCC susceptibility varies from alloy composition and with metallurgical condition. Given conditions of normal stress and BWR environment, several materials have shown susceptibility to IGSCC as a result of the material itself or due to its fabrication history. For RPVIs, these materials include austenitic stainless steel like Type 304/316 and nickel-base Alloys 600 and 182 weld metals. 

Because the presence of 5 to 10% ferrite in the microstmcture is extremely beneficial, the choice of filler material composition is cmcial in suppressing the risk of cracking. An indication of the ferrite-austenite balance for different compositions is provided by the Schaeffler diagram. For example, when welding Type 304 stainless steel, a Type 308 filler material that has a slightly different alloy content is used. 

Austenitic Stainless Steels. These steels, based on iron—chromium—nickel alloys, are not hardenable by heat treatment and are predominandy austenitic. They include Types 301, 302, 302B, 303, 304, 304L, 305, 308, 309, 310, 314, 316, 316L, 317, 321, and 347. The L refers to 0.03% carbon max, which is readily available. In some austenitic stainless steels, all or part of the nickel is replaced by manganese and nitrogen in proper amounts, as in one proprietary steel and Types 201 and 202 (see Table 4). 

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