2507 Same grade from different mill standard
S32750 00Cr25Ni7Mo4N 022Cr25Ni7Mo4N 1.4410
2507 Chemical component ASTM A240
2507 mechanical property ASTM A240
Tensile strength : > 795 Mpa
Yield Strength : >550 Mpa
Elongation (%): > 15%
Hardness: < HV310
Duplex stainless steel History
Since the birth of duplex stainless steel in the United States in the 1940s, it has grown to the third generation. Its main feature is that the yield strength can reach 400-550MPa, which is twice that of ordinary stainless steel, so it can save materials and reduce equipment manufacturing costs. In terms of corrosion resistance, especially in the medium environment (such as seawater, high chloride ion content), the resistance of pitting, crevice corrosion, stress corrosion and corrosion fatigue of duplex stainless steel is better than ordinary austenite. Stainless steel, comparable to high-alloy austenitic stainless steel.
2205/2507 duplex stainless steel performance characteristics
Due to the characteristics of the two-phase structure, the duplex stainless steel has the advantages of ferritic stainless steel and austenitic stainless steel by properly controlling the chemical composition and heat treatment process, and it will have excellent toughness and weldability with austenitic stainless steel and iron. High strength and resistance of tempered stainless steel
The combination of chloride stress corrosion properties, these superior properties make duplex stainless steel develop rapidly as a weldable structural material. Since the 1980s, it has become a parallel with martensitic, austenitic and ferritic stainless steels. Steel. Duplex stainless steel has the following performance characteristics:
(1) Molybdenum-containing duplex stainless steel has good resistance to chloride stress corrosion under low stress. Generally, 18-8 type austenitic stainless steel is prone to stress corrosion cracking in neutral chloride solution above 60 °C, and heat exchangers, evaporators, etc. made of such stainless steel in industrial medium of trace chloride and hydrogen sulfide. There is a tendency to produce stress corrosion cracking, while duplex stainless steel has good resistance.
(2) Molybdenum-containing duplex stainless steel has good pitting resistance. The duplex pitting potential of the duplex stainless steel is similar to that of the austenitic stainless steel when it has the same pitting resistance equivalent value (PRE=Cr%+3.3Mo%+16N%). The pitting corrosion resistance of duplex stainless steel and austenitic stainless steel is comparable to that of AISI 316L. The pitting and crevice corrosion resistance of 25% Cr-containing, especially nitrogen-containing, high-chromium duplex stainless steels exceeds that of AISI 316L.
(3) It has good corrosion fatigue and wear corrosion resistance. In the case of certain corrosive media, it is suitable for making power equipment such as pumps and valves.
(4) The comprehensive mechanical properties are good. It has high strength and fatigue strength, and its yield strength is twice that of 18-8 austenitic stainless steel. The elongation in the solid solution state is 25%, and the toughness value AK (V-notch) is above 100J.
(5) Good solderability, low thermal cracking tendency, generally no preheating before welding, no heat treatment after welding, and can be welded to 18-8 type austenitic stainless steel or carbon steel.
(6) The duplex processing temperature of the duplex stainless steel containing low chromium (18% Cr) is wider than that of the 18-8 austenitic stainless steel, and the resistance is small, and the steel sheet can be directly rolled and rolled without forging. The hot processing of duplex stainless steels containing high chromium (25% Cr) is slightly more difficult than austenitic stainless steels, and can be used to produce plates, tubes and wires.
(7) Compared with 18-8 type austenitic stainless steel during cold working, the work hardening effect is large. When the tube and the plate are subjected to deformation, large stress is required to deform.
(8) Compared with austenitic stainless steel, it has a large thermal conductivity and a small coefficient of linear expansion, and is suitable for use as a lining for equipment and for producing composite panels. Also suitable for making heat exchanger dies, heat transfer efficiency is higher than austenitic stainless steel.
(9) There are still various brittle tendencies of high-chromium ferritic stainless steel, which should not be used in working conditions above 300 °C. The lower the chromium content in duplex stainless steel, the less harmful the brittle phase such as σ.
Application about duplex stainless steel
Heat exchangers and cold showers and devices for seawater, high temperature, concentrated nitric acid, etc. for refining, fertilizer, paper, petroleum, chemical, etc.
Features and grade type
Duplex stainless steel has the characteristics of austenitic stainless steel and ferritic stainless steel because it has austenitic + ferritic two-phase structure and the content of the two phases is basically the same. The yield strength can reach 400Mpa ~ 550MPa, which is twice that of ordinary austenitic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has high toughness, low brittle transition temperature, and excellent resistance to intergranular corrosion and weldability. At the same time, it retains some characteristics of ferritic stainless steel, such as 475 °C brittleness and heat. High conductivity, small linear expansion coefficient, superplasticity and magnetic properties. Compared with austenitic stainless steel, the strength of duplex stainless steel is high, especially the yield strength is significantly improved, and the properties such as pitting corrosion resistance, stress corrosion resistance and corrosion fatigue resistance are also significantly improved.
Duplex stainless steels are classified according to their chemical composition and can be classified into four types: Cr18 type, Cr23 (excluding Mo) type, Cr22 type and Cr25 type. For Cr25 type duplex stainless steel, it can be divided into ordinary type and super duplex stainless steel. Among them, Cr22 type and Cr25 type are used more. The duplex stainless steel used in China is mostly produced in Sweden. The specific grades are: 3RE60 (Cr18 type), SAF2304 (Cr23 type), SAF2205 (Cr22 type), SAF2507 (Cr25 type).