Chemical Composition And Corrosion Resistance Of 2707HD Duplex Steel (s32707 Stainless Steel)

2707HD duplex steel is a super duplex stainless steel, and its corresponding UNS grade is S32707 stainless steel.

Special super duplex stainless steel is designed to solve the lack of local corrosion resistance and strength of super duplex stainless steel heat-resistant chloride. It came out after 2000. The PRE value of S32707 stainless steel can be as high as 49. It is high in nitrogen, molybdenum, chromium and duplex. The structure makes the yield strength and tensile strength of the steel pipe up to 800MPa and 1000MPa, respectively, and the plasticity and toughness are also maintained at a relatively high level required for engineering applications.

heat exchanger
Heat exchanger

The advent of 2707HD duplex steel has greatly broadened the application range of duplex stainless steel and improved its competitiveness with high-nickel materials such as super austenitic stainless steel and high-nickel corrosion-resistant alloys in engineering applications. The structure of 2707HD duplex steel is not significantly different from super duplex stainless steel such as 2507 stainless steel.

Chemical composition of 2707HD duplex steel (%)
Chemical composition grade UNS grade C Si Mn S P Cr Ni Mo Cu N
max max max max max
00Cr27Ni7Mo5N SAF 2707HD 0.03 1.00  1.50  0.02 0.035 26/29 5.5/9.5 4.0/5.0 1 0.3/0.5
UNS S32707

Since the yield strength of general duplex stainless steel is twice that of general austenitic stainless steel, the use of duplex stainless steel can greatly reduce the thickness of the material and reduce the weight of the equipment, which can save materials and reduce costs. 2707HD duplex Steel is higher than general duplex stainless steel and super duplex stainless steel, and has the advantages of saving materials and reducing costs.

S32707 stainless steel has good weldability. It is mostly used for heat exchanger tubing. TIG/GTAW (tungsten inert gas/tungsten inert gas arc welding) welding is recommended for the welding of the steel pipe and tube sheet, or manual For welding and TIG automatic welding, the welding consumables can be Sandvik 27.9.5L. In the α+γ duplex structure of the weld metal and heat-affected zone, the content of ferrite is 30% to 70%.

For heat exchangers, it is recommended to use the TIG/GTAW method to weld the tube to the tube sheet. The thermal cycle must be strictly controlled during the welding process, the interlayer temperature is less than 100℃, and the heat input Q range is 0.2~1.5KJ/mm.

S32707 stainless steel has excellent resistance to pitting, crevice corrosion and stress corrosion in chloride environments, and is particularly suitable for manufacturing heat exchanger equipment that uses seawater and chloride ions as working and cooling media. For example, the top heat exchanger bundle of the atmospheric distillation unit of the refinery has replaced 2507 duplex stainless steel with S32707 stainless steel, and the seawater condenser cooling tube made of 2707HD (the tube side is connected to seawater) has achieved satisfactory results. Due to the chemical composition and performance characteristics of this steel, it will be expanded to be used in applications resistant to some inorganic and organic acids.

Posted by stainless steel pipe fittings supplier, KAYSUNS

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