Stainless austenitic

Figure 6.29 Three favorable conditions of penetration of bacteria through a pinhole, causing a corroded subsurface cavity in stainless austenitic steels31...

The positive effect of nitrogen on the resistance to pitting corrosion of stainless austenitic steels has recently been studied in greater detail. Examinations of austenitic materials with different Cr,... 

Normal anodic stress corrosion cracking is caused by a combination of mechanical tensile stress and loeal eleetrolyte dissolution processes when certain conditions are met. First, the corrosive medium must have a specific effect on the respective alloy, and in addition, the alloy in contact with the electrolyte in this material/corrosive medium system must be prone to stress corrosion cracking. The tensile stress must also be suffleiently high. Susceptible systems, for example, are stainless austenitic steels in chloride-eontaining solution or unalloyed and low-alloy steels in nitrate solutions. In contrast, unalloyed and low-alloy steels are not susceptible to stress eorrosion eraeking in ehloride solutions. 

If stress relief annealing is to be carried out on stainless austenitic steels to avoid stress corrosion cracking, tenperatures above are required because of the high strength at elevated temperatures. The use of more resistant materials can therefore be regarded as a more suitable alternative. 

Stainless (austenitic) steel Osteosynthesis (bone screws) Biotolerant... 

Corrosion resistance of installation elements of stainless austenitic chromium-nickel steels at high temperatures) (in German)... 

The following steels can be used instead of stainless austenitic 18/10-CrNi steels if there is a risk of stress corrosion cracking ... 

Stainless austenitic CrNiMo steels with more than 2.5% Mo, passive Titanium... 

Practical experience and exposure tests covering periods of several years have demonstrated that, in the immersion zone under fouling, stainless austenitic standard steels with approx. 18% Cr, 9-16% Ni and up to 3% Mo may develop both... 

Figure 38 Pitting potentials in 0.5 M NaCI solution, pH 6.6, as dependent on temperature for stainless austenitic steels (AL-6 X, 1.4306, 1.4571, NSCD) and the Ni-based alloy Incoloy 825 (DIN-Mat. No. 2.4858) [177]...

The corrosion behaviour of nickel and 14 nickel alloys was tested in comparison to titanium and stainless austenitic steel (Table 66) by means of exposure in stagnant and flowing natural seawater (flow rate 0.23 m/s) over a period of 1.6 years [205]. 

Considering the success of detecting crack tip echoes from defects at the near probe surface, future work will deal with the detection and sizing of defects on the far probe surface. Future work also relates to carrying out defect sizing in anisotropic austenitic stainless steel welds and... 

The materials are austenitic stainless steel (Hereafter,it is said SUS304), ductile cast iron (Hereafter, it is said FCD500), and pure Ni. The composition of the materials is shown in Table. 1. Moreover, the sound characteristic of the materials and air as the defect are shown in Table.2. 

The stream from the reactor consisting of a mixture of urea, unconverted ammonium carbamate, excess water, and NH, is fed into the top of the stripper. The ACES stripper utilizes a ferrite—austenite stainless steel, as do the carbamate condensers. The reactor and scmbber are constmcted with 316 L urea-grade stainless steel. 

The enhanced strength and corrosion properties of duplex stainless steels depend on maintaining equal amounts of the austenite and ferrite phases. The welding thermal cycle can dismpt this balance therefore, proper weld-parameter and filler metal selection is essential. Precipitation-hardened stainless steels derive their additional strength from alloy precipitates in an austenitic or martensitic stainless steel matrix. To obtain weld properties neat those of the base metal, these steels are heat treated after welding. 

Formic acid is commonly shipped in road or raH tankers or dmms. For storage of the 85% acid at lower temperatures, containers of stainless steel (ASTM grades 304, 316, or 321), high density polyethylene, polypropylene, or mbber-lined carbon steels can be used (34). For higher concentrations. Austenitic stainless steels (ASTM 316) are recommended. 

Although Hitec is nonflammable, it is a strong oxidizer and supports the combustion of other materials. Consequendy, combustible materials must be excluded from contact with the molten salt. Hitec is compatible with carbon steel at temperatures up to 450°C. At higher temperatures, low alloy or austenitic stainless steel is recommended. Adding water to Hitec does not appreciably alter its corrosion behavior. 

Many initiators attack steels of the AISI 4300 series and the barrels of the intensifiers, which are usually of compound constmction to resist fatigue, have an inner liner of AISI 410 or austenitic stainless steel. The associated small bore pipework and fittings used to transfer the initiator to the sparger are usually made of cold worked austenitic stainless steel. The required pumping capacity varies considerably from one process to another, but an initiator flow rate 0.5 L / min is more than sufficient to supply a single injection point in a reactor nominally rated for 40 t/d of polyethylene. 

Standard Wrought Steels. Steels containing 11% and more of chromium are classed as stainless steels. The prime characteristics are corrosion and oxidation resistance, which increase as the chromium content is increased. Three groups of wrought stainless steels, series 200, 300, and 400, have composition limits that have been standardized by the American Iron and Steel Institute (AlSl) (see Steel). Figure 8 compares the creep—mpture strengths of the standard austenitic stainless steels that are most commonly used at elevated temperatures (35). Compositions of these steels are Hsted in Table 3. 

Fig. 8. Stress—rupture curves for annealed H-grade austenitic stainless steels. AISI numbers are given (see Table 3). Rupture iu 10,000 h (35). To convert...

AISI 321 and 347 are stainless steels that contain titanium and niobium iu order to stabilize the carbides (qv). These metals prevent iatergranular precipitation of carbides during service above 480°C, which can otherwise render the stainless steels susceptible to iatergranular corrosion. Grades such as AISI 316 and 317 contain 2—4% of molybdenum, which iacreases their creep—mpture strength appreciably. In the AISI 200 series, chromium—manganese austenitic stainless steels the nickel content is reduced iu comparison to the AISI 300 series. 

The highly aHoyed austenitic stainless steels are proprietary modifications of the standard AISI 316 stainless steel. These have higher creep—mpture strengths than the standard steels, yet retain the good corrosion resistance and forming characteristics of the standard austenitic stainless steels. Nickel-Base Superalloys. 

Hardness, Impact Strength. Microhardness profiles on sections from explosion-bonded materials show the effect of strain hardening on the metals in the composite (see Hardness). Figure 8 Ulustrates the effect of cladding a strain-hardening austenitic stainless steel to a carbon steel. The austenitic stainless steel is hardened adjacent to the weld interface by explosion welding, whereas the carbon steel is not hardened to a great extent. 

Nickel—Iron. A large amount of nickel is used in alloy and stainless steels and in cast irons. Nickel is added to ferritic alloy steels to increase the hardenabihty and to modify ferrite and cementite properties and morphologies, and thus to improve the strength, toughness, and ductihty of the steel. In austenitic stainless steels, the nickel content is 7—35 wt %. Its primary roles are to stabilize the ductile austenite stmcture and to provide, in conjunction with chromium, good corrosion resistance. Nickel is added to cast irons to improve strength and toughness. 

Addition of niobium to austenitic stainless steels inhibits intergranular corrosion by forming niobium carbide with the carbon that is present in the steel. Without the niobium addition, chromium precipitates as a chromium carbide film at the grain boundaries and thus depletes the adjacent areas of chromium and reduces the corrosion resistance. An amount of niobium equal to 10 times the carbon content is necessary to prevent precipitation of the chromium carbide. 

Duplex stainless steels (ca 4% nickel, 23% chrome) have been identified as having potential appHcation to nitric acid service (75). Because they have a lower nickel and higher chromium content than typical austenitic steels, they provide the ductabdity of austenitic SS and the stress—corrosion cracking resistance of ferritic SS. The higher strength and corrosion resistance of duplex steel offer potential cost advantages as a material of constmction for absorption columns (see CORROSION AND CORROSION CONTROL). 

Corrosion Resistance of the Austenitic Chromium—Mickel Stainless Steels in Chemical Environments, Inco Limited, Nickel Development Institute, Toronto, Ontario, Canada, 1963. 

Materials of Construction and Operational Stress. Before a centrifugal separation device is chosen, the corrosive characteristics of the Hquid and soHds as weU as the cleaning and saniti2ing solutions must be deterrnined. A wide variety of materials may be used. Most centrifuges are austenitic stainless steels however, many are made of ordinary steel, mbber or plastic coated steel. Monel, HasteUoy, titanium, duplex stainless steel, and others. The solvents present and of course the temperature environment must be considered in elastomers and plastics, including composites. 

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). 

---