Stainless steel ferritic type

Ferritic steels Stainless steels AISI type... 

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, ferritic 17% Cr type 0 2 0 2 <400 Wronglit, cast, clad Good Good 7S 6.0 AlSl type 430 ASTM corrosion- and heat-resisting steels... 

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. 

McDonald et al. studied the performance of solid stainless steel rebars (types 304 and 316) and found that they performed well while ferritic stainless steels (types 405 and 430) developed pitting (15). Studies by McDonald et al. reported investigations on a 10-year exposure of 304 stainless steel in Michigan and Type 304 stainless steel clad rebar in a bridge deck in New Jersey and found no corrosion (15). In a study by Virmani and Clemena, the type 316 stainless steel-clad rebar extended the estimated time to the cracking of the concrete beyond 50 years, but not as much as solid types 304 and 316 stainless steels (100 years) (16). 

Performance of stainless steel of type 304 and 316 for sodium components is excellent. Failure of welds have occurred in the stabilised grade 321 in PFR [I] Phenix [2] and 15 Mo3 ferritic steel in SNR-300 SPX-1 [2]. Performance of elevated temperature components on the whole is satisfactory indicating that failure mode of creep-fatigue can be well taken care of in design. 

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... 

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. 

When good resistance to aqueous sulfide corrosion is required, ferritic stainless steels or duplex stainless steels can be substituted for austenitic stainless steel. Ferritic stainless steels, such as Type 405 (S40500) or Type 430 (S43000), are not susceptible to chloride SCC. The duplex stainless steels have a mixed ferritic-austenitic structure and are resistant to chloride SCC, but not to highly aggressive chloride environments. 

Stainless steels. When chromium is present in amounts in excess of 12%, the steel becomes highly resistance to corrosion. There are several types of stainless steel which are summarized below. Ferritic stainless steels. Ferritic stainless steels contain between 12 and 25% chromium and less than 0.1% carbon. This type of steel cannot be heat treated, but may be strengthened by work hardening. 

Two types of materials are studied in the CIAPES programme ferritic steel and stainless steel. A database for vessels monitored by acoustic emission has been builded to collect the results of all the tests carried out in laboratory and in situ. 

Ferritic stainless steels depend on chromium for high temperature corrosion resistance. A Cr202 scale may form on an alloy above 600°C when the chromium content is ca 13 wt % (36,37). This scale has excellent protective properties and occurs iu the form of a very thin layer containing up to 2 wt % iron. At chromium contents above 19 wt % the metal loss owiag to oxidation at 950°C is quite small. Such alloys also are quite resistant to attack by water vapor at 600°C (38). Isothermal oxidation resistance for some ferritic stainless steels has been reported after 10,000 h at 815°C (39). Grades 410 and 430, with 11.5—13.5 wt % Cr and 14—18 wt % Cr, respectively, behaved significandy better than type 409 which has a chromium content of 11 wt %. 

Ferritic Stainless Steels. These steels are iron—chromium alloys not hardenable by heat treatment. In alloys having 17% chromium or more, an insidious embrittlement occurs in extended service around 475°C. This can be mitigated to some degree but not eliminated. They commonly include Types 405, 409, 430, 430F, and 446 (see Table 4) newer grades are 434, 436, 439, and 442. 

Martensitic Stainless Steels. The martensitic stainless steels have somewhat higher carbon contents than the ferritic grades for the equivalent chromium level and are therefore subject to the austenite—martensite transformation on heating and quenching. These steels can be hardened significantly. The higher carbon martensitic types, eg, 420 and 440, are typical cutiery compositions, whereas the lower carbon grades are used for special tools, dies, and machine parts and equipment subject to combined abrasion and mild corrosion. 

Other Metals. Metals such as the austenitic series. Types 301—347, and the ferritic series. Types 409—446, of stainless steels may be enameled, as well as a number of other alloys (17). The metal preparation usually consists of degreasiag and grit blasting. Copper, gold, and silver are also enameled. These metals are usually prepared for appHcation by degreasiag. Copper is pickled usiag either a nitric acid [7697-37-2] or a sulfuric acid [7664-93-9] solution, followed by a dilute nitric acid dip. Silver may be pickled in hot dilute sulfuric acid followed by a dip in a nitric acid solution (18). 

The H2SO4-CUSO4 test, unlike the Huey test, is specific for susceptibility due to chromium depletion and is unaffected by the presence of submicro-scopic a-phase in stainless steels containing molybdenum or carbide stabilisers. It can be used, therefore, with confidence to test susceptibility in austenic (300 series) and ferritic (400 series) stainless steels and in duplex austeno-ferritic stainless steels such as Types 329 and 326. 

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