How Much Lower Is the Maximum Temperature Resistance of 1.4404 than That of 310S?

The Short Answer: A Difference of About 230 °C

1.4404 (the EN designation of UNS S31603, widely known as 316L) and 310S (UNS S31008, EN 1.4845) are both austenitic stainless steels, but they are engineered for very different temperature windows. In continuous air service, 1.4404 is typically rated to a maximum of about 870 °C, while 310S is rated to about 1100 °C - a gap of roughly 230 °C. The difference is governed mainly by chromium and nickel content, which determine how protective the oxide scale is at high temperature.

Chemical Composition: Why 310S Lasts Longer in Heat

Both grades are chromium-nickel austenitic alloys. 310S carries much more chromium (24.00-26.00%) and nickel (19.00-22.00%), which form a dense and stable chromium-oxide scale that slows further oxidation. 1.4404 adds 2.00-3.00% molybdenum, which strongly improves resistance to pitting and crevice corrosion in chlorides, but molybdenum plays little part in oxidation resistance above 800 °C.

Typical composition ranges per ASTM A240 (wt%):

Element	1.4404 / UNS S31603	310S / UNS S31008
Carbon, max	0.030	0.08
Silicon, max	0.75	1.50
Manganese, max	2.00	2.00
Phosphorus, max	0.045	0.045
Sulfur, max	0.030	0.030
Chromium	16.00-18.00	24.00-26.00
Nickel	10.00-14.00	19.00-22.00
Molybdenum	2.00-3.00	Not specified
Nitrogen, max	0.10	Not specified

Mechanical Properties (Annealed Plate, ASTM A240)

Property	1.4404 / S31603	310S / S31008
Tensile strength, min (MPa)	485	515
Yield strength, min (MPa)	170	205
Elongation, min (%)	40	40

At room temperature the two grades are close in strength. The real separation appears at temperature: 310S keeps useful strength and a protective scale where 1.4404 would oxidize quickly and lose load-bearing capacity to creep. Above roughly 550 °C, creep - not oxidation - usually becomes the limiting design factor for both grades.

Practical Temperature Limits: Continuous and Intermittent Service

Typical published ratings for air service: 1.4404 - about 870 °C continuous and 815 °C intermittent; 310S - about 1100 °C continuous and 1035 °C intermittent. These ratings assume oxidizing atmospheres and negligible applied load. In reducing or sulfidizing atmospheres the usable limits can be lower, and in vacuum or inert-gas service oxidation is no longer the governing concern.

Application Guidance

1.4404: food and beverage equipment, chemical storage, pharmaceutical plant, heat exchangers and marine components where chloride pitting resistance matters and service stays below roughly 500-550 °C for load-bearing parts.

310S: furnace parts, radiant tubes, muffles, kiln components, heat-treatment fixtures and petrochemical equipment where service reaches 900-1100 °C and scaling resistance is essential.

If a component will see sustained temperature above about 900 °C, 1.4404 is not an acceptable substitute for 310S.

Frequently Asked Questions

What is the maximum service temperature of 1.4404?

About 870 °C for continuous service in air and about 815 °C for intermittent service, based on oxidation behaviour. For pressure-bearing parts the design temperature is usually much lower because creep strength falls sharply above about 550 °C.

Why does 310S tolerate higher temperatures than 1.4404?

310S contains 24.00-26.00% chromium and 19.00-22.00% nickel, roughly 8 percentage points more of each than 1.4404. These elements form a slower-growing, more adherent chromium-oxide scale and keep the austenitic structure stable at high temperature.

Can 1.4404 replace 310S in a furnace operating at 1000 °C?

No. At 1000 °C, 1.4404 oxidizes rapidly and loses mechanical strength. 310S is rated to about 1100 °C in air and is the appropriate choice for such service.

Is 1.4404 better than 310S for chloride environments?

At moderate temperature, yes. The 2.00-3.00% molybdenum in 1.4404 gives markedly better pitting and crevice corrosion resistance in chlorides. In hot chloride service, however, both grades are vulnerable to stress corrosion cracking and duplex or higher-alloy grades should be considered.

What are the EN and UNS equivalents of these grades?

1.4404 corresponds to UNS S31603 and EN X2CrNiMo17-12-2 (EN 10088); 310S corresponds to UNS S31008 and EN 1.4845 (X8CrNi25-21).

Which grade should be used for a high-temperature heat exchanger?

If the metal temperature stays below about 550-600 °C, 1.4404 can be suitable and offers better corrosion resistance in process fluids. Above that range, 310S - or a creep-resistant stabilized grade such as 321 or 347 for service around 800-900 °C - is the safer choice.