253MA
253MA (UNS S30815) is an austenitic heat-resistant stainless steel alloyed with silicon and cerium rare-earth elements. These additions produce a tightly adherent, multi-layer oxide scale that resists spallation under thermal cycling at temperatures up to 1100°C. The nitrogen content provides solid-solution strengthening, helping the alloy maintain creep resistance at service temperature.
1. Chemical Composition
The table below lists the elemental composition of 253MA. The rare-earth (cerium) and high-silicon additions are responsible for its oxidation resistance and strong scale adhesion.
| GRADE | UNS Designation |
C | Mn | P | S | Si | Cr | Ni | Mo | Ti | Cu | Al | Other |
| 253MA | S30815 | 0.05-0.1 | 0.80 | 0.040 | 0.030 | 1.4-2.0 | 20.0-22.0 | 10.0-12.0 | N:0.14-0.20 Ce:0.03-0.08 |
Note: The cerium addition (0.03–0.08%) acts as an oxide scale modifier. It improves how well the chromia scale adheres to the steel surface during thermal cycling, a property that conventional austenitic heat-resistant grades lack.
2. Mechanical Properties
These are the minimum mechanical property values for 253MA in the solution-annealed condition. They reflect both ambient-temperature strength and suitability for structural use in high-temperature furnace environments.
| Grade | Condition & Size | Standard | Heat Treating Temp. : min | Tensile Strength Min. MPa |
Yield Strength Min. MPa |
Elongation min. % |
| 253MA | A312 | 1040°C | 600 | 310 | 35 |
Note: At 900°C, 253MA keeps a 0.2% proof strength of roughly 70–80 MPa. This gives it useful load-bearing capacity at temperatures where standard 310 stainless steel softens considerably.
3. Equivalent Grade
This table shows international designation cross-references for 253MA. Equivalents are limited because its proprietary cerium-modified composition does not appear in most national standards.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 253MA | S30815 | - | 0Cr21Ni11N | - | X9CrNiSiNCe21-11 | 1.4835 | - |
Note: 253MA is a proprietary grade developed by Outokumpu (formerly Avesta Sheffield). EN 1.4893 is the recognized European equivalent. There are no direct equivalents in JIS, GB, or GOST.
3. Key Technical Advantages
- Cerium-Modified Oxide Scale Adherence: The rare-earth cerium addition changes the oxide growth mechanism on the steel surface. Cerium segregates to oxide grain boundaries and the metal-oxide interface, where it suppresses oxide scale spallation during thermal cycling. This is the primary failure mechanism in conventional austenitic heat-resistant alloys above 900°C.
- High Silicon for Oxidation Resistance Beyond Chromium Alone: Silicon at 1.4–2.0% forms a sub-layer of amorphous SiO2 beneath the primary chromia (Cr2O3) scale. This slows oxygen diffusion through the oxide layer and extends service life in air and combustion atmospheres up to 1100°C.
- Nitrogen Solid-Solution Strengthening for Elevated-Temperature Creep: Nitrogen at 0.14–0.20% strengthens the austenitic matrix through solid solution, improving creep rupture life compared to equivalent chromium-nickel grades between 800°C and 1050°C. It does this without reducing ductility or formability.
- Technical Note: 253MA is designed for cyclic oxidizing atmospheres, not reducing or sulfidizing environments. In sulfur-bearing combustion gases, the cerium and silicon additions do not protect against sulfide attack. High-nickel alloys are more appropriate for sulfidizing service. Welding should use matching 253MA filler or Sanicro 71 (ERNiCr-3) for full corrosion performance.
4. Common Manufacturing Standards
- ASTM A312: Standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipes. UNS S30815 is listed for heat-resistant service piping.
- ASTM A213: Standard specification for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes. S30815 is applicable for high-temperature service.
- ASTM A249: Standard specification for welded austenitic steel boiler, superheater, heat-exchanger, and condenser tubes. The S30815 designation applies.
- DIN EN 10216-5: Seamless steel tubes for pressure purposes, stainless steel (Grade 1.4893 equivalent).
- GB/T 14976: Seamless stainless steel tubes for fluid transport. Material substitution review is required since no direct GB designation has been established.
Manufacturing Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 S30815 | EN 10216-5 (1.4893) | — | — | — |
| Seamless Tube | A213 S30815 | EN 10216-5 (1.4893) | — | — | — |
| Welded Tube | A249 S30815 | EN 10217-7 (1.4893) | — | — | — |
5. Primary Applications
- Radiant Tubes in Heat Treatment Furnaces: Electrically heated and gas-fired radiant tubes in batch and continuous heat treatment furnaces operating between 900–1100°C. In this range, 253MA's cyclic oxidation resistance extends tube service life well beyond standard 310 stainless steel.
- Industrial Burner Components: Flame deflectors, burner baskets, and combustion chamber inserts in gas-fired industrial furnaces. These parts face frequent thermal cycling and high peak temperatures that spall conventional oxide scales.
- Incinerator Afterburner Chambers: Structural components in waste incineration afterburner sections and thermal oxidizer vessels operating in aggressive mixed-atmosphere combustion gases at 900–1050°C.
- Biomass and Waste-to-Energy Boilers: Superheater and reheater tube bundles in biomass-fired boilers. Alkali chloride deposits combined with high temperatures challenge both oxidation resistance and deposit-induced corrosion performance in these installations.
- Ethylene Cracker Convection Section Tubes: Convection section tube coils in steam cracking furnaces where cyclic thermal loading and an oxidizing flue gas atmosphere make scale adhesion the primary material selection factor.