What is AISI329 material?

A type of stainless steel that is more corrosion-resistant than ordinary austenitic stainless steels, and also possesses excellent mechanical properties. Chemical composition (%): C 0.10, Mn 2.00, Si 1.00, Cr 25.0–30.0, Ni 3.0–6.0, P 0.045, S 0.03, Mo 1.0–2.0. Density at 25 degrees Celsius: (×1000 kg/m3) 7.8. Poisson’s ratio: 0.27–0.30. Elastic modulus: (GPa) 190–210. Tensile strength: (Mpa) 724 (annealed). Yield strength: (Mpa) 550. Elongation: (%) 25. Last edited by superblade on 2009-3-24 at 12:43

Some of the stainless steels are those specified in the American ASTM standard series: AISI303, AISI301, AISI302, AISI 304, AISI304J1, AISI304N2, AISI304L, AISI304LN, AISI-XM21, AISI309, AISI309S, AISI310S, AISI 305, AISI312L, AISI S31254, AISIXM-15, AISI315J1, AISI 316/L/F, AISI 316Ti, AISI 317L, AISI304L, AISI309L, AISI316LS, AISI317, AISI347, AISI321, AISI-XM7, AISI329, AISI405, AISI403, AISI 400, AISI 409, AISI 410S, AISI 436, AISI 410, AISI 439, AISI416, AISI 420J2/F, AISI 430, AISI430FR, AISI430F, AISI 434, AISI 440A, AISI 440B, AISI 440C, AISI 440F, AISI446, AISI447, AISI 431, AISI 202, AISI 205, AISI 17-4PH, AISI 904L

AISI 329 is known as duplex stainless steel; the German designation is 1.4462. Duplex stainless steel refers to a type in which, within its solid solution structure, ferritic phase and austenitic phase are present in equal amounts, with the content of each phase generally needing to be at least 30%. At low C levels, the Cr content ranges from 18% to 28%, while the Ni content ranges from 3% to 10%. Some steels also contain alloying elements such as Mo, Cu, Nb, Ti, and N. This type of steel possesses the characteristics of both austenitic and ferritic stainless steels. Compared to ferritic steels, it offers higher plasticity and toughness, lacks room-temperature brittleness, and exhibits significantly improved resistance to intergranular corrosion as well as weldability. At the same time, it retains the brittleness at 475°C and high thermal conductivity associated with ferritic stainless steels, as well as superplasticity. Compared to austenitic stainless steels, it has higher strength, as well as significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel possesses excellent pitting resistance and is also a nickel-saving stainless steel. Performance characteristics of duplex stainless steel: Due to its two-phase structure, and through proper control of chemical composition and heat treatment processes, duplex stainless steel combines the advantages of both ferritic and austenitic stainless steels. It merges the excellent toughness and weldability of austenitic stainless steels with the higher strength and resistance to chloride stress corrosion of ferritic stainless steels. It is these superior properties that have led to the rapid development of duplex stainless steel as a weldable structural material; since the 1980s, it has become one of the major types of stainless steel, on par with martensitic, austenitic, and ferritic stainless steels. Dual-phase stainless steel has the following performance characteristics: (1) Molybdenum-containing dual-phase stainless steel exhibits good resistance to chloride stress corrosion at low stresses. Generally, type 18-8 austenitic stainless steel is prone to stress corrosion cracking in neutral chloride solutions at temperatures above 600°C. Equipment such as heat exchangers and evaporators made from this type of stainless steel in industrial environments containing trace amounts of chlorides and hydrogen sulfide is susceptible to stress corrosion cracking, whereas duplex stainless steel exhibits good resistance to such phenomena. (2) Mo-containing duplex stainless steels exhibit good pitting resistance. When they have the same pitting resistance equivalent value (PRE=Cr%+3.3Mo%+16N%), the critical pitting potentials of duplex stainless steels and austenitic stainless steels are similar. The pitting resistance of duplex stainless steels and austenitic stainless steels is comparable to that of AISI 316L. The pitting and crevice corrosion resistance of 25%Cr stainless steels, especially nitrogen-containing high-chromium duplex stainless steels, exceeds that of AISI 316L. (3) It exhibits good resistance to corrosion fatigue and wear corrosion. Under certain corrosive medium conditions, it is suitable for manufacturing power equipment such as pumps and valves. (4) It has good comprehensive mechanical properties. It has high strength and fatigue resistance, with a yield strength that is twice that of 18-8 type austenitic stainless steel. The elongation rate in the solid solution state reaches 25%, and the toughness value AK (V-notch) is above 100 J. (5) It has good weldability and a low tendency to thermal cracking; generally, no preheating is required before welding, nor is heat treatment necessary after welding. It can be welded to different materials such as 18-8 austenitic stainless steel or carbon steel. (6) The hot working temperature range for duplex stainless steels with low chromium content (18%Cr) is wider than that of 18-8 austenitic stainless steels; they exhibit less resistance, allowing steel plates to be produced directly through rolling without the need for forging. Hot working of duplex stainless steels with high chromium content (25% Cr) is slightly more difficult than that of austenitic stainless steels, but products such as sheets, tubes, and wires can be manufactured. (7) During cold working, the work hardening effect is greater than that of 18-8 austenitic stainless steel; at the initial stage of deformation in tubes and plates, a higher stress must be applied to cause deformation. (8) Compared with austenitic stainless steels, it has a higher thermal conductivity and a lower linear expansion coefficient, making it suitable for use as linings in equipment and for producing composite sheets. It is also suitable for use in heat exchanger wafers, offering a higher heat exchange efficiency than austenitic stainless steel. (9) It still possesses various brittle tendencies of high-chromium ferritic stainless steels, and is not suitable for use in operating conditions above 3000°C. The lower the chromium content in duplex stainless steel, the less harmful the brittle phases such as σ become.