Sandvik 27.7.5.L is a filler material of hyper-duplex (austenitic-ferritic) stainless steel that has been specially developed for welding of the hyper-duplex steel Sandvik SAF 2707HD.
Chemical composition (nominal) %
Sandvik 27.7.5.L is a hyper-duplex (austenitic-ferritic) filler metal with improved yield strength and better pitting and crevice corrosion resistance compared to super-duplex stainless steels (UNS S32750 and S32760). It also has higher HISC (hydrogen induced stress cracking) resistance compared to super-duplex stainless steels and higher resistance to aggressively sour environments.
Sandvik 27.7.5.L can be advantageously used for welding 13% Cr flow pipes, as its high strength enables reduction of repair rates during pipeline production, because finite element analysis is not required for weld metal of matching strength and the acceptance criteria can be less conservative.
The high pitting resistance of Sandvik 27.7.5.L makes it suitable for root pass welding in Sandvik SAF 2507 and other super-duplex stainless steels (UNS S32750 and S32760) when the risk of pitting corrosion is critical, or when mixed shielding gases cannot be used.
Sandvik 27.7.5.L can also be used for overlay welding on e.g. tube sheets in heat-exchangers or for joint welding of hyper-duplex (UNS S32707) pipe with wall thickness < 13 mm.
Forms of supply
Sandvik 27.7.5.L is supplied as wire and rod.
Weld metal characteristics
Sandvik 27.7.5.L gives an austenitic-ferritic (duplex) microstructure with approximately 60-70% ferrite measured according to ASTM E562.
MIG TIG – typical for non-heat treated weld metal
|Temperature||°C (°F)||20 (68)||-30 (-22)||-50 (-58)|
|Yield strength, RP0.2||MPa (ksi)||690 (100)||-||-|
|Tensile strength, Rm||MPa (ksi)||890 (129)||-||-|
|Impact strength, Charpy V||J (ft lbs)||190 (140)||106 (78)||40 (30)|
a) Rp0.2 corresponds to 0.2% offset yield strength.
Sandvik 27.7.5.L has excellent resistance to intergranular corrosion and pitting. Nominal CPT in the ASTM G48 test is 57.5°C. The filler also excellent resistance to stress corrosion cracking, especially in environments containing H2S or chlorides.
Recommended welding data
The parameters for TIG welding depend largely upon the base metal thickness and the welding application.
Electrode negative and a shielding gas of argon+3%N2 should be used to prevent oxidation and to maintain nitrogen in the weld metal.
Recommended thermal data
Heat-input is restricted to 0.2-1.0 kJ/mm and maximum interpass temperature is 100°C (212°F).