The 2707HD Duplex steel is a special super duplex stainless steel. The corresponding UNS grade is S32707 stainless steel. The special super duplex stainless steel is used to solve the problem of the local corrosion resistance and strength of the heat-resistant chloride of super duplex stainless steel. It was introduced after 2000. The PRE value of S32707 stainless steel can be as high as 49. The high nitrogen, molybdenum, chromium content and Duplex structure make the yield strength and tensile strength of this steel pipe as high as 800MPa and 1000MPa, respectively, and the plasticity and toughness are also maintained in the engineering application. The higher level of need. The availability of the 2707HD Duplex steel has greatly broadened the application of duplex stainless steels and increased the competitiveness of high nickel materials such as super austenitic stainless steels and high nickel corrosion resistant alloys in engineering applications. The microstructure characteristics of the 2707HD Duplex steel are not significantly different from those of the superduplex stainless steel such as 2507 stainless steel.
Since the duplex stainless steel generally has twice the yield strength of general austenitic stainless steel, the use of duplex stainless steel can significantly reduce the thickness of the material and reduce the weight of the equipment. This saves material and reduces costs, making the 2707HD Duplex possible. Steel is higher than common duplex stainless steel and super duplex stainless steel, and it has the advantages of material saving and composition reduction.
S32707 stainless steel has good weldability. The 2707 Duplex steel is mostly used for the heat transfer tube of the heat exchanger. It is recommended to use the TIG/GTAW method (tungsten inert gas/tungsten inert gas arc welding) for the welding of the steel tube and the tube sheet. Manual welding and TIG welding can be used. Sandvik27.9.5L can be used as the filler material. Ferritic content is 30% to 70% in the α+γ duplex microstructure of weld metal and HAZ of Sandvik 27.9.5L. Because of the high nitrogen content in the stainless steel of S32707, γ2 austenite is quickly generated during the welding process. In order to make up for the consumption of nitrogen in the protective gas, the protection gas for the welding of this steel is Ar+2% to 3%N2. For heat exchangers, the TIG/GTAW method is recommended for tube and tube plate welding. During the welding process, the thermal cycle must be strictly controlled. The inter-layer temperature should be less than 100°C, and the heat input Q should be in the range of 0.2 to 1.5 KJ/mm.
S32707 stainless steel in the chloride environment has excellent resistance to pitting, crevice corrosion and stress corrosion resistance, and is particularly suitable for the manufacture of heat exchanger equipment using seawater and Cl-containing working media and cooling media. For example, the tower overhead heat exchanger bundle of the refinery atmospheric distillation unit has satisfactorily used S32707 stainless steel instead of 2507 duplex stainless steel and the seawater condenser cooling pipe (tube-pass seawater) manufactured with 2707HD.
|Super Duplex S32707 Seamless Pipe||Super Duplex Seamless Pipe|