Austenitic stainless steels characteristics

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. 

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. 

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. 

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. 

S. Ahmad, M.L. Mehta, S.K. Saraf, and I. Saraswat, Anodic Polarization Characteristics of Sensitized 304 Austenitic Stainless Steel in Polythionic Acid Environment, Corrosion, Vol 39,1983, p 330... 

Since austenitic stainless steels are susceptible to pitting and intergranular corrosion in the presence of chloride ions, other materials were examined for caustic service [43-47]. These include Fe-Cr alloys, which are resistant to SCC. However, these alloys are brittle and suffer from 475°C embrittlement and sigma embrittlement. A popular alloy that was examined for the caustic evaporator service was E-Brite-26-1, containing 26% Fe and 1 % Mo, which exhibited performance characteristics comparable to that of... 

The body of the vessel is of low-alloy steel. To minimize corrosion, the inside surfaces in contact with the coolant are cladded with a minimum of some 3-lOmm of austenitic stainless steel. The major characteristics of the RPVs used for four-loop plants are listed in Table 4.1 (IAEA, 2009). The PWR RPV design pressure is about 17 MPa and the operating pressure is about 15.5 MPa. The design temperature is 343 °C where the operating temperature is typically 280-325 °C (IAEA, 2009). 

Characteristics and Mechanical Properties of Cold-Worked Austenitic Stainless Steels for RCPB Components... 

SCC of the austenitic stainless steels has a characteristic morphology. The cracks are branching and transgranular in nature, unless the alloy is sensitized. In sensitized material the cracking will take an intergranular path. This form of corrosion also has an incubation period. Depending on the chloride ion concentration, the temperature, and the magnitude of tensile stresses, the failure can occur within hours or after many years. 

Corrosion of filters occurs in the transpassive state. Their cathodic protection is based on the polarization of steel to a potential characteristic of the passive state. Garner (1998) states that over 120 CP installations have been applied, mainly in North America, for the protection against corrosion of equipment made of austenitic stainless steels operating in bleacheries. More information is given by Webster (1989) and Singbeil and Garner (1987). 

Commercial phosphoric acid contains fluorides, chlorides, sulfates, and heavy metal ions as impurities, however, which significantly increase its corrosivity and makes its corrosion characteristics unpredictable. Chloride contamination significantly increases acid corrosion of austenitic stainless steels and requires the use of nickel-based alloys. Very good corrosion behavior is reported for the superferrite XlCrNiMoNb28-4-2, Fig. 1-44 (Thyssen Edelstahl, 1979). 

Wrought austenitic stainless steels do not exhibit the sharp ductile to brittle transition behavior characteristic of low alloy and carbon steels. Rather, toughness losses due to irradiation tend to accumulate with increasing fluence and saturate at levels >1x10 n/m. Until recently, there was little information available to quantify the effects of radiation embrittlement on RPVIs. New information [5.2] describes the results of a fracture toughness study performed on irradiated Type 304 stainless steel reactor internal material taken from... 

As mentioned before, austenitic stainless steels are susceptible to IGC due to sensitization caused by exposure to high temperatures (450-850 C). The IGC of austenitic stainless steel can also be characterized by normalized classical tests ASTM G28, ASTM A262-86, SEP 1877, AFNOR A05-159 and AFNOR A05-160, currently known as the Strauss, Huey and Streicher tests [54-57]. These methods however are destructive, difficult to perform on site and require sampling that can be harmful to the integrity of materials during service. For this reason, the electrochemical, non-destructive tests commonly known as EPR (electrochemical potentiokinetic reactivation) and DL-EPR (double loop electrochemical potentiokinetic reactivation) were developed to measure the sensitivity of austenitic stainless steels to IGC [58-66]. However, EPR and DL-EPR are based on measurements of characteristic potentials and currents of passive/active zones on potentiody-namic curves in an aqueous solution (linear voltammetry curve from oxygen to hydrogen evolution in the... 

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