UNS S32100 STAINLESS STEEL PICKLING ANNEALED PIPE A312 TP321

Overview

Stainless Steel Seamless (SMLS) pipe is formed by drawing a solid billet over a piercing rod to create the hollow shell. As the manufacturing process does not include any welding, Seamless Pipes are perceived to be stronger and more reliable. Historically, seamless pipe was regarded as withstanding pressure better than other types, and was often more available than Welded Pipe.

Grades 321 and 347 are the basic austenitic 18/8 steel (Grade 304) stabilized by Titanium (321) or Niobium (347) additions. These grades are used because they are not sensitive to intergranular corrosion after heating within the carbide precipitation range of 425-850°C. Grade 321 is the grade of choice for applications in the temperature range of up to about 900°C, combining high strength, resistance to scaling and phase stability with resistance to subsequent aqueous corrosion.

Grade 321H is a modification of 321 with a higher carbon content, to provide improved high temperature strength.

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 stabilization 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.

ASTM A312 TP321 Chemical Composition

ASTM A312 TP321 Mechanical Properties

ASTM A312 TP321 Physical Properties

ASTM A312 TP321 Grade Specifications

ASTM A213 TP321 Stainless Steel Seamless Pipes Application:

• Food preparation equipment particularly in chloride environments.
• Laboratory benches & equipment.
• Coastal architectural panelling, railings & trim.
• Boat fittings.
• Chemical containers, including for transport.
• Heat Exchangers.
• Woven or welded screens for mining, quarrying & water filtration.
• Threaded fasteners.
• Springs.