Austenitic steels parameters

High chromium in martensitic steels have strengths comparable to austenitic steels up to 500°C and present a greater resistance to the effect of radiation damage. For this reason, it is important to obtain parameters such as the solubility and permeability of hydrogen and its isotopes. 

In FP-5, two projects deal with irradiation assisted cracking of austenitic steels, the material used for reactor internals. Within the framework of FP-5 project INTERWELD the radiation induced damages that promote cracking in the heat affected zones of PWR and BWR core internal components will be studied looking at parameters such as neutron fluence/irradiation conditions, residual stresses, microstructural and microchemical conditions. Further work is... 

In Fig. 8 can be seen in the centered disks the deficiency intersections of the high order Lane zones (HOLZ). As was demonstrated previously by Sarikaya et al [30] in austenitic steels in the central disks with deficiency lines, they are very sensitive to the crystal lattice parameters when the diagrams are obtained in the same excitation conditions. The first results obtained in mullite/zirconia are in this sense promising. 

The austenitic-ferritic steels, because of their two structural components also known as duplex steels, are chromium-nickel steels with chromium contents of about 21%-27%, and nickel contents of 4%-5%. They are usually made with about 3% molybdenum, nitrogen additions and a carbon content of < 0.03%. They reach the category of temperable martensitic steels with values for the 0.2% yield point of > 450 N/mm and are thus clearly above the austenitic steels. Worth mentioning are the good viscosity parameter values and the favourable fatigue strength properties of these steels, even in corrosive mediums. 

The above measures and reactor operation under derated power conditions resulted in a significant reduction in the number of defective fuel rods in the core. Further increase in fuel bum-up is planned through utilization of the ferritic steel EP-450 for ducts and improved austenitic steel in cold-worked state for cladding. The basic parameters for different cores used in the reactor are ven in Table 2.2. Simultaneously with the improvement of the core fuel operating performances, modifications have been introduced in the design of the control rods and guide sleeves by the use of radiation-resistant structural materials. 

Alloy composition is a key material parameter. Otsuka et al. [44] showed that a Cr content >25wt.% was necessary for formation of a uniform external Cr203 film on the surface of austenitic steels this film reduces outward Fe diffusion and prevents formation of a less-protective (Fe,Cr)304 outer layer. There appears to be little effect of Ni content on corrosion resistance in SCW (Fig. 4.10). 

Fig. 8.4 highlights the fact that, beyond the material nature, the key parameter governing the Fe dissolution is here the Cr content starting from 9% in the ferrito-martensitic EMI 2, which is therefore unsuitable for reprocessing with classical processes, to 16% with the 316 type steels which present no reprocessing problem at all. In Section 8.6 we discuss the possibility of specifying an advanced austenitic steel exhibiting a lower Cr content than classical materials of 300-series, and will have to keep in mind the rather poor behavior of the 12% Cr N9 material, CEA precursor of advanced austenitic materials. 

The austenitic and, hence, anisotropic V-butt weld is embedded in isotropic steel it has a width of 10 mm at its baseline and a height of 30 mm. If a notch is present, it has a width of 1 mm and a height of 15 mm it is located at the right-hand side of the V-butt weld. The simulated transducer is a commercial 45°-shear wave probe (MWB45-2E). The parameters varied during the simulations are ... 

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. 

Some of the most obvious examples of problems with gas and materials are frequently found in refining or petrochemical applications. One is the presence of hydrogen sulfide. Austenitic stainless steel, normally a premium material, cannot be used if chlorides are present due to intergranular corrosion and subsequent cracking problems. The material choice is influenced by hardness limitations as well as operating stresses that may limit certain perfonnance parameters. 

With small modifications, ASTM standard G48 can be used to determine a CPT. The test is used as a ranking parameter for the resistance to pitting of high-alloyed austenitic stainless steels. In this method, material coupons are typically exposed for 24 or 72 h to a 6% FeCl3 (=1.11 mole/liter) solution at fixed temperatures (typically with 2.5°C intervals). The CPT is defined as the lowest temperature at which the specimen is attacked by pitting corrosion. 

Microscopic examination of a hardened 1.0 percent carbon steel shows no undissolved carbides. X-ray examination of this steel in a diffractometer with filtered cobalt radiation shows that the integrated intensity of the 311 austenite line is 2.33 and the integrated intensity of the unresolved 112-211 martensite doublet is 16.32, both in arbitrary units. Calculate the volume percent austenite in the steel. (Take lattice parameters from Fig. 12-5, A/corrections from Fig. 13-8, and temperature factors from Fig. 4-20.)... 

PRE is also a vahd parameter when stainless-steel parts are not completely embedded in concrete and are partially in direct contact with the aggressive environment. In these cases it is more appropriate to specify austenitic stainless steels with molybdenum, since they provide additional corrosion resistance. A minimum molybdenum content of 2.5% is preferable to 2%, because of the resulting increase in corrosion resistance with only marginal increase in cost. 

Parameters for Pitting Corrosion of Austenitic Chromium-Nickel Steels... 

Due to their exceptional industrial relevance, some practical approaches to improve the machinability of austenitic stainless steels are presented in the following. They can be subdivided into attempts to modify the cutting tool geometries and coating systems, attempts to determine optimal cutting parameters, and attempts for the most suitable application of cutting fluids. 

Knotek O, Loffler F, Kramer G (1992) Multicomponent and multilayer physically vapour deposited coatings for cutting tools. Surf Coat Technol 54-55 241-248 Korkut I, Kasap M, Ciftci I, Seker U (2004) Determination of optimum cutting parameters during machining of AISI 304 austenitic stainless steel. Mater Des 25(4) 303-305... 

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