1.4878 vs 1.4571 Stainless Steel: Composition, Heat Resistance and Selection

What the Two Designations Actually Mean

Both grades are titanium-stabilised austenitic stainless steels, but they belong to separate families in the European designation system. EN 1.4878 (X8CrNiTi18-10) is a heat-resisting grade listed among the austenitic steels of EN 10095 and is the European counterpart of AISI 321H, UNS S32109. EN 1.4571 (X6CrNiMoTi17-12-2) is a corrosion-resisting grade covered by EN 10088-2 for flat products and EN 10088-3 for bars, rods and profiles, and corresponds to AISI 316Ti, UNS S31635. The practical consequence is that ordering 1.4878 is normally driven by a temperature requirement, while ordering 1.4571 is driven by a corrosion requirement.

Titanium is present in both grades for the same reason: it combines with carbon to form TiC particles, which removes carbon from solid solution and prevents chromium carbide precipitation at grain boundaries during welding or prolonged exposure in the 425-815 C sensitisation band.

Chemical Composition Comparison

The carbon range is the single most important difference. 1.4878 is deliberately held at a higher carbon level to raise high-temperature creep strength; the same higher carbon is exactly what makes the grade less suitable for aggressive aqueous corrosion where welded assemblies are left in the as-welded condition.

Mechanical Properties and the Elevated-Temperature Window

At room temperature the two grades are close. Under ASTM A240 both 321H and 316Ti carry a minimum tensile strength of 515 MPa and a minimum 0.2 % offset yield strength of 205 MPa in the annealed condition. The separation appears above roughly 500 C, where 1.4878 retains useful creep and stress-rupture strength to about 850 C in oxidising atmospheres. 1.4571 is normally applied below that range; its molybdenum improves pitting and crevice resistance rather than creep resistance. Design work at temperature should always be based on the stress-rupture data of the actual heat and product form, since grain size and stabilisation practice influence creep behaviour strongly.

Corrosion Resistance in Chloride and Acid Service

The 2.00-2.50 % molybdenum addition in 1.4571 raises its pitting resistance number (PREN = Cr + 3.3 Mo + 16 N) to roughly 24-26, against approximately 18-20 for 1.4878. In practice this means 1.4571 tolerates chlorides, dilute hydrochloric acid and organic acids that would initiate pitting in 1.4878, which is why 1.4571 is common in chemical plant, pulp and paper, food processing and marine-adjacent piping. 1.4878, lacking molybdenum, is selected for hot gas, flue gas, furnace and exhaust components instead of for wet chloride service.

Welding, Forming and Product Forms

Both grades weld with matching stabilised filler metals and do not require post-weld solution annealing for intergranular corrosion resistance in ordinary thicknesses. Cleanliness matters more than filler selection: heat tint and iron contamination must be removed mechanically or by pickling to restore the passive film. Cold formability of 1.4571 is slightly lower than that of 1.4301 because of its higher alloy content, and both grades work-harden readily, so progressive forming with intermediate anneals is normal for deep-drawn parts. Standard supply forms include seamless and welded pipe, plate, coil, round bar, wire and fasteners. Pipe is commonly supplied to EN 10216-5 or ASTM A312 practice, and plate to EN 10028-7 or ASTM A240 practice.

How to Choose

Choose 1.4878 when the governing condition is sustained high temperature: furnace furniture, radiant tubes, exhaust manifolds, heat exchanger tubes in hot gas, and expansion joints. Choose 1.4571 when the governing condition is aqueous corrosion, particularly chlorides or reducing acids, and when welded construction cannot be heat treated. If a project needs both, a common compromise is to specify one grade for the hot section and the other for the wet section, with dissimilar joints made with a nickel-rich filler.

Frequently Asked Questions

Q: Is 1.4878 the same as 321?
A: No. 1.4878 corresponds to 321H, the higher-carbon variant of 321. The H grade requires 0.04-0.10 % carbon, while standard 321 is limited to 0.08 % carbon, which is why 321H is preferred for creep service.

Q: Can 1.4571 replace 1.4878 in a high-temperature application?
A: Only after checking creep data. 1.4571 has lower carbon and therefore lower creep strength at the top of the temperature range; substituting it purely on the basis of similar room-temperature strength is not safe.

Q: Which grade is better for chloride-containing media?
A: 1.4571. Its molybdenum content gives a higher pitting resistance number and better crevice corrosion behaviour than 1.4878.

Q: Do the two grades need post-weld heat treatment?
A: For corrosion service in normal thicknesses, no. Titanium stabilisation prevents sensitisation, so solution annealing is only required when the specification or a severe environment demands it.

Q: Are both grades magnetic?
A: In the fully annealed condition they are essentially non-magnetic. Cold working such as drawing, bending or thread rolling generates strain-induced martensite and can make the material weakly magnetic.

Q: What product forms are normally available?
A: Seamless and welded pipe, plate, sheet, coil, round and hexagonal bar, wire and machined fasteners. Availability of heavy-wall or large-diameter sections is more limited for 1.4878 than for 1.4571.