Stabilized S32109 321H Seamless Boiler Steel Tube Corrosion Resistance

Description
 

TP 321 is a stabilized stainless steel which offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperature in the chromium carbide precipitation range from 800 °F to 1500°F (427°C to 816°C). Alloy 321 stainless steel tubing is stabilized against chromium carbide formation by the addition of titanium.

Specification:

321 321H Stainless Steel is a titanium-stabilised version of 304, used in particular applications within the sensitizing temperature range. Its resistance to sensitization, coupled with its higher strength at high temperature makes it suitable in application where 304 will become sensitized, or where 304L has insufficient hot strength. It is not subject to weld decay intergranular corrosion when exposed to mildly corrosive environments. However, welded 321 must never be used in highly oxidising environments as it is liable to ‘Knife-line’ attack. However, 321 is a much better option in operating temperature environments in excess of 500° C and therefore has its own merits. Alloy 321 stainless steel tube is also advantageous for high temperature service because of its good mechanical properties. Alloy 321 stainless steel offers higher creep and stress rupture properties than Alloy 304 and, particularly, Alloy 304L also be considered for exposure where sensitization and intergranular corrosion are concern.

321 321H stainless steel is basically from 304 stainless steel. They different by a very very small addition of Titanium. The real difference is their carbon content. The higher the carbon content the greater the yield strength. 321 stainless steel has advantages in high temperature environment due to its excellent mechanical properties. Compared with 304 alloy, 321 stainless steel has better ductility and resistance to stress fracture. In addition, 304L can also be used for anti-sensitization and intergranular corrosion.A limitation with 321 is that titanium does not transfer well across a high temperature arc, so is not recommended as a welding consumable. In this case grade 347 is preferred – the niobium performs the same carbide stabilisation task but can be transferred across a welding arc. Grade 347 is therefore the standard consumable for welding 321. Grade 347 is only occasionally used as parent plate material.

Like other austenitic grades, 321 and 347 have excellent forming and welding characteristics, are readily brake or roll formed and have outstanding welding characteristics. Post-weld annealing is not required. They also have excellent toughness, even down to cryogenic temperatures. Grade 321 does not polish well, so is not recommended for decorative applications.

Grade 304L is more readily available in most product forms, and so is generally used in preference to 321 if the requirement is simply for resistance to intergranular corrosion after welding. However 304L has lower hot strength than 321 and so is not the best choice if the requirement is resistance to an operating environment over about 500°C.

Application Industries

• Off-Shore Oil Drilling Companies
• Power Generation
• Petrochemicals
• Gas Processing
• Specialty Chemicals
• Pharmaceuticals
• Pharmaceutical Equipment
• Chemical Equipment
• Sea Water Equipment
• Heat Exchangers
• Condensers