worked into a wide variety of shapes without becoming distorted and, in terms of corrosion, have the same resistance levels as austenitic steels [1]. Nitronic stainless steel alloys contain nitrogen and are completely austenitic. Nitronic steels do not become magnetic when they are cold worked. Nitronic stainless steel contains nitrogen, which makes it stronger and also more resistant to corrosion. Nickel is also a primary ingredient, improving resistance to corrosion and overall workability. Due to their composition, Nitronic steel is not only one of the strongest steel, but it is temperature resistant and continuously non-magnetic as well [2]. This versatility is reflected in the fact that there are actually over 150 different grades of stainless steel, with fifteen of them being the ones most commonly used. Table 4.1 shows the stoichiometry of Nitronic and 4340 steels. Table 4.2 shows a summary of mechanical properties of Nitronic steels and 4340 steel. 4.1.1 Grades of Nitronic Stainless Steel [2] • Nitronic 30 is highly resistant to both corrosion and abrasion and it is also resistant to impact, and as such it can be used for heavy-duty jobs. It is one of the toughest and most durable steels and it is used for coal buckets, ore separators, food processing equipment, sewage treatment, and truck or bus frames [3]. • Nitronic 40, like other Nitronic steels, remains austenitic and retains its toughness all the way down to—253 C,making this type of stainless steel perfect for cryogenic applications. Therefore it is used in many different applications such as, for aircraft as ducting and bellows systems, fasteners, clamps, and flanges. It is also resistant to oxidation at high temperatures [4]. • Nitronic 50 stainless steel is also highly resistant to corrosion and is also very strong. However, when annealed, it has nearly twice its normal yield strength. It is used for pumps, fasteners, cables, wire cloth, boat and marine hardware, springs, and photographic equipment [5]. • Nitronic 60 is a high quality steel of lower cost than other alloys. Nitronic 60 stainless steel provides resistance to oxidation at high temperatures and resistance to impact at lower temperatures. It is ideal for valve seats, trim and stems, as well as nuts and bolts, screening, pins, roller bearings, and pump components, bridge pins and other fastening systems [6]. Table 4.1 Composition of Nitronic steels and 4340 30 40 50 60 4340 Carbon 0.03max. 0.08 0.06 0.10 0.37–0.43 Manganese 7.0–9.0 3–10.00 8 8 0.6–0.8 Phosphorus 0.040max. 4.00–6.00 0.035 Sulfur 0.030max. 0.030 0.030 0.04 Silicon 1.00max. 1.00 1.00 4 0.15–0.30 Chromium 15.0–17.0 19–21.50 17 17 0.7–0.9 Nickel 1.5–3.0 5.50–7.50 11.50–13.50 8.5 1.65–2.00 Nitrogen 0.15–0.30 0.15–0.40 0.20–0.30 0.13 Copper 1.00max. Molybdenum 1.50–3.00 0.2–0.3 Columbium/Niobium 0.10–0.30 Vanadium 0.10–0.30 The remaining element if iron [3–7] Table 4.2 Properties of Nitronic and 4340 steels [3–7] ρ E UTS YS El% Hardness Nitronic 30 0.284 lb/in3 7.862 g/cm3 28 103 Ksi 193 GPa 108 Ksi 749 MPa 49Ksi 339 MPa 56 B89 Nitronic 40 0.285 lb/in3 7.89 g/cm3 28 103 Ksi 193 GPa 95 Ksi 655 103 MPa 48Ksi 330 MPa 35 B100 Nitronic 50 0.285 lb/in3 7.89 g/cm3 28 103 Ksi 193 GPa 121 Ksi 834 MPa 57Ksi 393 MPa 46 B91 4340 0.284 lb/in3 7.86 g/cm3 29 103 Ksi 200 GPa 108 Ksi 745 MPa 68.2 Ksi 470 MPa 22 B95 22 C.G. Fountzoulas et al.
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