ASTM A312 TP321H Stainless Steel Seamless Pickling Tube
ASTM A312 TP321H Stainless Steel Seamless Pickling Tube
ASTM A312 TP321H is a seamless stainless steel tube treated with a titanium stabilizer, giving it excellent resistance to intergranular corrosion at high temperatures (up to 1500°F). Its key characteristics include a high carbon content for improved high-temperature strength, excellent low-temperature toughness, and ease of machining and welding. "Pickling" refers to a surface treatment process using an acid solution after manufacturing to remove oxide scale and rust.
What are the properties of 321 stainless steel?
321 stainless steel has a density of 0.29 g/cm³. Its elastic modulus is 193 GPa. Its resistivity is 72 μΩ·cm. Its thermal conductivity at 100℃ is 16.1 W/mK, and at 500℃ it is 22.2 W/mK.
ASTM A312 is a standard developed by the American Society for Testing and Materials (ASTM), entitled "Seamless and Welded Nominal Tubing of Austenitic Stainless Steel." It is one of the most fundamental and widely used standards in the field of stainless steel process piping. TP321H is a grade under this American standard. Compared to standard TP321, grade H has a lower carbon content requirement of only 0.04% to ensure higher creep strength and high-temperature durability. It is manufactured seamlessly using punching and cold drawing/cold rolling processes, resulting in a uniform integral structure and stronger pressure resistance. Pickling is a key post-treatment step in the surface treatment process.
ASTM A312 Stainless Steel Seamless Pipe Chemical Composition
| GRADE |
UNS. |
ASTM A312 CHEMICAL COMPOSITION % MAXIMUM | |||||||
|---|---|---|---|---|---|---|---|---|---|
| C | MN | P | S | SI | CR | NI | Ti | ||
| TP321H | S32109 | 0.04-0.10 | 2.00 | 0.045 | 0.030 | 1.00 | 17.0-19.0 | 9.0-12.0 |
4(C+N) min; 0.70 max |
The Significance of Pickling
The pickling process for stainless steel pipes typically involves immersing the pipe in a pickling solution composed of nitric acid and hydrofluoric acid. Through a chemical reaction, the oxide scale dissolves, exposing a uniform, silvery-white metallic substrate. Its main purpose is to remove the oxide scale that forms on the surface of stainless steel after high-temperature heat treatment, as well as trace contaminants embedded in the surface.
After pickling removes the oxide scale, a complete, dense, and chromium-rich passivation film can reform on the surface of the steel pipe, thereby restoring the pipe's corrosion resistance. Simultaneously, the cleaned surface facilitates non-destructive testing, such as penetrant testing, allowing for clearer detection of surface cracks, wrinkles, and other defects.
ASTM A312 TP321H Stainless Steel Seamless Pipe Mechanical Properties
| SS GRADE | HEAT TREATMENT | Tensile Strength, min ksi [MPa] | Yield Strength, min ksi [MPa] | |
|---|---|---|---|---|
| Cold Finished | Hot Finished | |||
| TP321H | 2000 °F [1100 °C] | 1925 °F [1050 °C] | 75 [515] | 30 [205] |
ASTM A312 TP321H Stainless Steel Seamless Pipe Main Applications:
Petrochemical Industry: Process piping for catalytic cracking units, reforming units, and heating furnaces, especially suitable for pipe sections requiring frequent welding.
Power Generation (Coal Power): Superheater and reheater piping in boilers, and high-temperature, high-pressure systems, such as main steam piping.
Thermal Engineering: Heat exchangers and high-temperature flue gas piping.
Food and Pharmaceutical Industry: Due to its smooth, clean pickled surface and excellent corrosion resistance, it can be used in certain process piping applications.
Gnee Steel specializes in the production of a wide range of stainless steel products. Gnee Steel's product packaging includes: Steel Strapping: Pipes with an outer diameter of 3 inches or less are typically strapped together with polypropylene film to prevent rust during ocean shipping, and then secured with steel strapping. Wooden Cases/Crates: Pipes are typically packaged in wooden cases or crates to protect the pipes during transportation, especially those that are longer or have larger diameters. Seaworthy Export Packaging: Suppliers typically use standard seaworthy export packaging methods, which may include a variety of materials and techniques to protect the pipes during transportation. Tarpaulin Packaging: This prevents rain, seawater, and other external factors from penetrating the export crates during transportation. Gnee Steel specializes in the production and sale of alloy materials. Gnee Steel's products are widely used in the aerospace, chemical, power, automotive, and nuclear energy sectors, and we can provide customized alloy material solutions based on customer needs. For alloy material pricing or customized alloy material solutions, please contact us for a quote: ru@gneesteelgroup.com
