Super stainless steel

Kane, R. D. (1993). Super stainless steels resist hostile environments, Adv. Mater. Process., July, pp. 16-20. 

Table 14. Super-Ferritic Grades of Stainless Steel...

Super austenitic, high nickel, stainless steels, containing between 29 to 30 per cent nickel and 20 per cent chromium, have a good resistance to acids and acid chlorides. They are more expensive than the lower alloy content, 300 series, of austenitic stainless steels. 

Duplex, and super-duplex stainless steels, contain high percentages of chromium. They are called duplex because their structure is a mixture of the austenitic and ferritic phases. They have a better corrosion resistance than the austenitic stainless steels and are less susceptible to stress corrosion cracking. The chromium content of duplex stainless steels is around 20 per cent, and around 25 per cent in the super-duplex grades. The super-duplex steels where developed for use in aggressive off-shore environments. 

Solutes have differing solubilities in different liqnids dne to variations in the strength of the interaction of solnte molecnles with those of the solvent. Thus, in a system of two immiscible or only partially miscible solvents, different solutes become unevenly distribnted between the two solvent phases, and as noted earlier, this is the basis for the solvent extraction technique. In this context, solvent almost invariably means organic solvent. This uneven distribution is illustrated in Fig. 1.3, which shows the extractability into a kerosene solution of the different metals that appear when stainless steel is dissolved in aqueous acid chloride solution. The metals Mo, Zn, and Fe(III) are easily extracted into the organic solvent mixture at low chloride ion concentration, and Cu, Co, Fe(ll), and Mn at intermediate concentration, while even at the highest chloride concentration in the system, Ni and Cr are poorly extracted. This is used industrially for separating the metals in super-alloy scrap in order to recover the most valuable ones. 

Super Duplex Stainless Steel 9 Wrought/ Forgings A182Gr55 S32760 EN 102504 EN 100883 X2Cr Ni Mo CuWN2S74 1,4501 ... 

The original hydrothermal method involves heating the reactants in a closed vessel, an autoclave, with water (Figure 3.5). An autoclave is usually constructed from thick stainless steel to withstand the high pressures, and is fitted with safety valves it may be lined with non-reactive materials such as teflon. The autoclave is heated, the pressure increases, and the water remains liquid above its normal boiling temperature of 373 K, so-called super-heated water . These conditions, in which the pressure is raised above atmospheric pressure and the temperature is raised above the boiling temperature of water (but not to as high a temperature as used in the... 

Stainless steel 316L material used for piping and equipment shows considerable corrosion resistance because of the beneficial effect of molybdenum on the surface properties. It is also observed that the surface treatment (pre-reduced, polished, passivated and chemically treated surfaces) of stainless steel equipment and piping reduces the corrosion process in seawater applications. The corrosion resistance of stainless steel in seawater applications can also be enhanced by bulk alloying the stainless steel with nitrogen, chromium, molybdenum and nickel by converting the stainless steel into super austenitic stainless steel. From leaching studies it is also observed that the release of iron, chromium and nickel from the super austenitic stainless steel to seawater is considerably... 

The variety of materials available on the market today is immense, and the better manufacturers have designs from carbon steel over stainless steel, to duplex, super duplex, up to Hastelloy and even titanium. Usually body, bonnets and disc holders are made from castings, while a lot of the internal parts are made from bar, but almost any combination is possible today. 

Grinding media is selectable from stainless steel, ceramic or super hard... 

Alloys containing molybdenum can potentially experience catastrophic oxidation. The super-austenitic stainless steels such as Alloy AL-6XN, a 21Cr-25Ni-6.5Mo-N alloy (UNS N08367), are an example. A heavy molybdenum oxide scale forms, usually as a result of an improper heat treatment or a severe thermal excursion. Removal of such scales prior to service (or return to service), usually by pickling, prevents this problem. 

TWO STAINLESS STEEL SUPER HEATERS (12in xl V2 in O.D.) PACKED WITH STAINLESS STEEL RASCHIG RINGS. 

C San March , BP Somerday, J Zelinski, X Tang, and GH Schiroky, Mechanical properties of super duplex stainless steel 2507 after gas phase thermal precharging with hydrogen , Metallurgical and Materials Transactions, accepted. 

Super austenitic stainless steels with relatively high nickel content (approx. 20 Cr. 29 - 34 Ni), sometimes referred to as "alloy 20" are more costly than standard austenitic steels but provide excellent resistance to acids and some acid chlorides. 

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