General Introduction

Alloy 2507, with UNS number S32750, is a famous super duplex stainless steel. As a member of the duplex stainless steel family, it is a two-phase alloy based on the iron-chromium-nickel system with a mixed structure of about equal proportions of austenite and ferrite. Due to the duplex phase balance, Alloy 2507 exhibits excellent resistance to general corrosion like that of austenitic stainless steels with similar alloying elements. Besides, it possesses higher tensile and yield strengths as well as significantly better chloride SCC resistance than its austenitic counterparts while maintaining better impact toughness than the ferritic counterparts.

Chloride SCC Resistance, Pitting & Crevice Resistance

For severe environments in which chloride SCC is the primary concern, all austenitic stainless steels, especially types 304 and 316, are susceptible to some degree. Standard duplex stainless steel 2205 (S31803/ S32750) is highly resistant to chloride SCC. Under certain conditions of temperature – Cl– concentration combination, super duplex stainless steel 2507 (S32750) is completely immune to the stress corrosion cracking as illustrated in the diagram above. This has been attributed to the blocking of crack propagation by the ferrite. The SCC resistance may be evaluated by a drop evaporation test in which the critical stress that caused cracking is indicated as a percentage of yield strength. According to lab literature, in the drop evaporation test with sodium chloride solutions at 120°C [248°F], the critical stress that caused stress corrosion cracking of mill-annealed Alloy 2507 (S32750) is about 76% of the yield strength. It is much higher than the value of Type 316 which is only about 5%.

Product Surface:

2B	The surface brightness and flatness of no2B is better than no2D. then through a special surface treatment to improve its mechanical properties,No2B could nearly satisfy comprehensive uses.
No.1	Polished with abrasive belt of grit#100-#200, have better brightness with discontinuous coarse stria, used as inner and external ornaments for building, electrical appliances and kitchen utensils etc.
No.4	Polished with abrasive belt of grit #150-#180,have better brightness with discontinuous coarse stria, but thinner than No3, are used as bathtub buildings inner and external ornaments electrical appliances kitchen utensils and food processing equipment etc.
HL	Polished with abrasive belt of grit #150-#320 on the NO.4 finish and has continuous streaks, mainly used as buildings ornaments elevators, door of building, frontal plate etc.
BA	Cold rolled, bright annealed and skin-passed, the product have excellent brightness and good reflexivity like mirror, kitchen apparatus, ornament etc.
8K	The product have excellent brightness and prefer reflexivity can to be the mirror.

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