Piping material grades & UNS numbers
Quick reference to common piping materials — UNS numbers, the ASTM specifications for forgings, fittings and pipe, and where each grade is typically used. Compare any grades in the MOC comparator or see EN/DIN/JIS equivalents.
| Grade | UNS | Family | Typical ASTM / ASME specs | Typical use |
|---|---|---|---|---|
| Carbon steel A105 | K03504 | Carbon steel | ASTM A105 (forgings / flanges) | The standard carbon-steel forging for flanges and forged fittings in ambient and high-temperature service. |
| Carbon steel WPB | K03006 | Carbon steel | ASTM A234 WPB (buttweld fittings), A106 Gr B / A53 Gr B (pipe) | The workhorse grade for process, steam and utility piping. |
| Low-temp carbon steel LF2 | K03011 | Carbon steel | ASTM A350 LF2 (forgings), A420 WPL6 (fittings), A333 Gr 6 (pipe) | Impact-tested carbon steel for service down to about -46 °C. |
| Chrome-moly F11 / P11 | K11572 / K11597 | Alloy steel | ASTM A182 F11, A234 WP11, A335 P11 | 1¼Cr-½Mo for high-temperature steam and refinery service. |
| Chrome-moly F22 / P22 | K21590 | Alloy steel | ASTM A182 F22, A234 WP22, A335 P22 | 2¼Cr-1Mo for higher-temperature power and refinery lines. |
| Chrome-moly F91 / P91 | K90901 | Alloy steel | ASTM A182 F91, A234 WP91, A335 P91 | 9Cr-1Mo-V creep-strength-enhanced steel for supercritical power plants. |
| Stainless 304 | S30400 | Austenitic stainless | A182 F304, A403 WP304, A312 TP304 | General-purpose 18-8 stainless steel. |
| Stainless 304L | S30403 | Austenitic stainless | A182 F304L, A403 WP304L, A312 TP304L | Low-carbon 304 for welded construction; resists sensitisation. |
| Stainless 316 | S31600 | Austenitic stainless | A182 F316, A403 WP316, A312 TP316 | Molybdenum-bearing grade with better pitting resistance than 304. |
| Stainless 316L | S31603 | Austenitic stainless | A182 F316L, A403 WP316L, A312 TP316L | Low-carbon 316; the most specified stainless grade for process plants. |
| Stainless 321 | S32100 | Austenitic stainless | A182 F321, A403 WP321, A312 TP321 | Titanium-stabilised for high-temperature service. |
| Stainless 347 | S34700 | Austenitic stainless | A182 F347, A403 WP347, A312 TP347 | Niobium-stabilised for high-temperature service. |
| Super austenitic 904L | N08904 | Super austenitic | A182 F904L, A403 WP904L, B677 / A312 | High-alloy grade for sulphuric acid and chloride service. |
| Super austenitic 254 SMO | S31254 | Super austenitic | A182 F44, A403 WPS31254, A312 | 6Mo grade for seawater and aggressive chloride environments. |
| Duplex 2205 | S31803 / S32205 | Duplex stainless | A182 F51 / F60, A815, A790 | Roughly twice the strength of 316L with excellent chloride stress-corrosion resistance. |
| Super duplex 2507 | S32750 | Super duplex | A182 F53, A815, A790 | High-strength, high-PREN grade for offshore and seawater systems. |
| Super duplex Zeron 100 | S32760 | Super duplex | A182 F55, A815, A790 | Tungsten/copper-bearing super duplex for offshore and desalination service. |
| Nickel alloy 400 (Monel) | N04400 | Nickel-copper | B564, B366, B165 | Excellent resistance to seawater, hydrofluoric acid and alkalis. |
| Nickel alloy 600 (Inconel) | N06600 | Nickel-chromium | B564, B366, B167 | Oxidation and high-temperature resistance. |
| Nickel alloy 625 (Inconel) | N06625 | Nickel-chromium-moly | B564, B366, B444 | High strength with outstanding pitting and crevice resistance. |
| Nickel alloy 825 (Incoloy) | N08825 | Nickel-iron-chromium | B564, B366, B423 | Resists sulphuric and phosphoric acids. |
| Hastelloy C-276 | N10276 | Nickel-moly-chromium | B564, B366, B622 | One of the most corrosion-resistant alloys for severe chemical service. |
| Alloy 20 | N08020 | Nickel-iron-chromium | B462, B366, B729 | Designed for sulphuric acid service. |
| Titanium Grade 2 | R50400 | Titanium | B381 F2, B363 WPT2, B861/B862 | Commercially pure titanium for seawater and chloride service. |
| Titanium Grade 5 | R56400 | Titanium | B381 F5, B348 | Ti-6Al-4V high-strength alloy. |
| Copper-nickel 90/10 | C70600 | Copper-nickel | B151, B466/B467 | Seawater piping, cooling water and shipbuilding. |
| Copper-nickel 70/30 | C71500 | Copper-nickel | B151, B466/B467 | Higher-velocity seawater service. |
Reading a material specification
A single alloy appears under different ASTM numbers depending on product form: A182 for forged flanges, A403 or A815 for buttweld fittings, and A312 or A790 for pipe. The UNS number ties them together, which is why purchase orders often state both the ASTM specification and the UNS designation.
Frequently asked questions
What is the UNS number of 316L?
S31603.
What is the UNS number of duplex 2205?
S31803 or S32205; S32205 has tighter chemistry and is often dual-certified.
What is ASTM A182 F51?
F51 is duplex stainless steel UNS S31803 in forged form, used for flanges and forged fittings.
Last updated 2026-11-02