Overview

X9CrNiSiNCe21-11-2 is a heat-resistant austenitic chromium-nickel stainless steel with high silicon and nitrogen contents and a rare-earth (cerium) micro-addition, developed for high-temperature service where oxidation resistance, creep strength and long-term structural stability are essential. This datasheet presents the material within the European standard system.

It resists oxidation in air up to about 1150 °C (2100 °F) and provides superior service to the 25Cr-20Ni (310-type) grade in carbon-, nitrogen- and sulphur-bearing atmospheres. Its comparatively low nickel content gives an advantage in reducing sulphidising atmospheres relative to high-nickel alloys. The high chromium and silicon, together with the nitrogen and cerium, give good oxide-scale stability and adherence, high elevated-temperature (creep) strength and excellent resistance to sigma-phase precipitation: cerium suppresses oxide-scale spallation during thermal cycling, silicon forms a protective sub-scale that slows oxygen diffusion, and nitrogen provides solid-solution strengthening. The fully austenitic structure gives excellent toughness, even down to cryogenic temperatures. The most suitable temperature range is about 850–1100 °C; prolonged use in the 600–850 °C range can lead to structural changes (embrittlement).

Typical applications include industrial-furnace components and linings, radiant tubes, muffles and retorts, annealing baskets and heat-treatment fixtures, heat exchangers and recuperators, burner components, and other equipment for high-temperature oxidizing or thermally-cycled service. Resistance to oxidizing/reducing sulphur-bearing gases and to aqueous corrosion is limited.

1. Physical Properties

2. Chemical Composition (wt %)

Composition per EN 10095 (W.Nr. 1.4835, X9CrNiSiNCe21-11-2).

Nominal: 21Cr-11Ni-Si-N-Ce heat-resistant steel. The Si-N-Ce additions give exceptional oxidation resistance and creep strength to ~1150 °C in air.

3. Mechanical Properties

Solution-annealed (+AT) condition, per EN 10095 for W.Nr. 1.4835.

Values per EN/DIN; confirm against the inspection certificate (EN 10204).

4. Oxidation and High-Temperature Resistance

5. Heat Treatment

An austenitic stainless steel; it cannot be hardened by heat treatment. Strength is increased only by cold work.

Solution Anneal approximately 1020–1120 °C (commonly ~1080 °C), followed by rapid cooling in water or air, to dissolve carbides and secondary phases and produce a uniform austenitic structure with optimum oxidation and creep behaviour.

Prolonged exposure in the ~600–850 °C range can cause structural changes (embrittlement); ductility can be restored by re-solution-annealing followed by rapid cooling. The cerium and nitrogen additions help resist sigma-phase precipitation.

6. Weldability and Joining

Has good weldability and can be joined by submerged-arc, plasma-arc, flux-cored-arc, shielded-metal-arc, gas-tungsten-arc and gas-metal-arc processes. A matching or over-alloyed heat-resistant filler (matching 253-type composition) is used; preheating is not required.

No preheat required. Keep heat input controlled; solution anneal after welding where maximum high-temperature performance is required.

7. Machinability and Fabrication

Machining Guidelines

Forming Processes

8. Applications

9. Available Product Forms and Standards

Heat-resistant Si-N-Ce austenitic stainless steel (21Cr-11Ni). W.Nr. 1.4835 (X9CrNiSiNCe21-11-2); EN 10095. (Variant of 1.4828 with increased nitrogen and rare-earth metals.)

10. Comparison with Related Alloys (EN Symbol System)

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