High Temperature Resistance: 1.4841 vs 1.4845 Stainless Steel

1.4841 and 1.4845: The 25Cr-20Ni Heat-Resisting Family

1.4841 (X15CrNiSi25-20) and 1.4845 (X8CrNi25-21) are austenitic heat-resisting stainless steels standardized in the EN 10088 series and used for components that run at elevated temperature in oxidizing atmospheres. Both grades are built on a 24-26% chromium, 19-22% nickel base, the combination that gives this family its resistance to scaling and to attack by combustion gases. The practical differences between the two grades are the silicon and carbon levels, and these small differences control service temperature, weldability and fabrication cost.

Chemical Composition and Standard Equivalents

Element (wt%)	1.4841 X15CrNiSi25-20	1.4845 X8CrNi25-21
C	0.15 max	0.10 max
Si	1.50-2.50	1.50 max
Mn	2.00 max	2.00 max
P	0.045 max	0.045 max
S	0.015 max	0.015 max
Cr	24.0-26.0	24.0-26.0
Ni	19.0-22.0	19.0-22.0
ASTM equivalent	UNS S31000 (AISI 310)	UNS S31008 (AISI 310S)

Composition limits follow EN 10088-1 / EN 10095. 1.4841 is the higher-silicon, higher-carbon grade; 1.4845 is the low-carbon variant. A common misconception is that 1.4845 gains creep strength from molybdenum. It does not: neither grade lists molybdenum as an intentional alloy addition. The oxidation and creep behavior of this family is governed by chromium, nickel, silicon and carbon, not by molybdenum.

High-Temperature Performance

At elevated temperature the protective scale formed by the 25Cr-20Ni base resists continued oxidation, and the silicon in 1.4841 improves scale adhesion and resistance to spalling during thermal cycling. As a result 1.4841 is commonly specified for furnace rollers, radiant tubes, heat-treatment baskets and exhaust purification components with typical continuous service around 1000 C and peaks toward 1050-1100 C. 1.4845, with carbon limited to 0.10%, shows better microstructural stability in welded assemblies and is frequently used for boiler internals, combustion chamber parts and welded heat-treatment equipment with continuous service around 1050 C. Exact temperature limits depend on atmosphere, stress level and cycling, and should be confirmed against component design practice.

Mechanical Strength and Corrosion Resistance

At room temperature both grades deliver tensile strength in the 500-700 MPa range in the annealed condition. At high temperature the controlling property is creep and rupture strength rather than room-temperature tensile strength; the higher carbon of 1.4841 supports carbide formation that helps resist deformation under sustained load. In terms of corrosion, both grades resist oxidation, carburization and attack by hot combustion gases, and both perform well in nitric acid and mild chemical media. However, because neither grade contains molybdenum, pitting resistance in chloride-rich or seawater-like environments is limited; for chloride service a molybdenum-bearing grade such as 316L or a 6% Mo super-austenitic grade is required instead.

Fabrication and Welding

1.4841 is harder to machine than 1.4845 because the elevated silicon content accelerates work hardening; carbide tooling and reduced speeds are recommended. Welding of both grades is carried out with matching high-alloy fillers of the 310 type, low heat input and interpass control to avoid hot cracking; 1.4841 needs tighter preheat and interpass control because of its silicon level. 1.4845 is the more forgiving grade for welded and formed components and is preferred where fabrication complexity is high. Post-weld heat treatment is not generally required for either grade.

Selection Guidance

Choose 1.4841 when the component sees repeated thermal cycling, requires a tightly adherent scale, and fabrication is simple, for example furnace rollers, burner nozzles and exhaust system parts. Choose 1.4845 when the component is welded or cold formed, when the assembly is large, or when maximum microstructural stability at continuous high temperature matters, for example boiler internals, combustion chambers and radiant tube assemblies. When chlorides or seawater are present, move to a molybdenum-alloyed stainless grade and do not rely on this family.

FAQ

Are 1.4841 and 1.4845 the same as 310 and 310S?

They are the EN counterparts of the ASTM 310 family: 1.4841 approximates UNS S31000 (310) and 1.4845 approximates UNS S31008 (310S). The EN and ASTM limits differ slightly, so use the standard specified on the purchase order.

Does 1.4845 contain molybdenum?

No. Neither 1.4845 nor 1.4841 lists molybdenum as an intentional alloy addition. Their high-temperature resistance comes from chromium, nickel and silicon; do not expect chloride pitting resistance comparable to molybdenum-bearing grades.

Which grade withstands higher temperature in continuous service?

1.4845 is typically rated for continuous service near 1050 C, while 1.4841 is commonly used around 1000 C with peaks toward 1100 C. The limiting factor is usually creep and scale spalling behavior under the actual atmosphere and stress, so ratings should be treated as guidance rather than absolute limits.

Can these grades be welded?

Yes. Use matching 310-type filler metal with low heat input and controlled interpass temperature. 1.4841 needs tighter control because its higher silicon content raises hot-cracking sensitivity. Post-weld heat treatment is not normally required.

Can 1.4841 or 1.4845 replace 316L in chloride service?

No. Both grades lack molybdenum and have limited pitting resistance in chloride environments. For seawater or chloride service specify 316L, 317L or a 6% Mo super-austenitic grade instead.

How do I decide between 1.4841 and 1.4845 for furnace parts?

Use 1.4841 for simple cast or forged parts exposed to thermal cycling where scale adhesion matters. Use 1.4845 for welded assemblies, large structures and applications where low carbon improves weldability and long-term microstructural stability.