Short answer: High-temperature or heat-resistant stainless steels rely on high chromium (for a protective oxide scale) and nickel (for a stable austenitic matrix) to survive 700–1150 °C service. 309S covers the mid-temperature range in clean air; 310S is the workhorse for 950–1100 °C and aggressive thermal cycling; 314 adds silicon for better scale resistance; and 330 (Ni-Cr-Fe alloy) is chosen for carburizing and nitriding atmospheres where pure stainless falls short.
This guide is written for stainless steel buyers, sourcing teams, engineers and product manufacturers. The purpose is not to declare one universal winner, but to turn a broad material question into a specification that a mill or service center can quote, process and inspect consistently.
Quick Comparison
| Option | Key point | Typical use or decision |
|---|---|---|
| 309S / S30908 | 23Cr 13Ni, low carbon | Furnace linings, burner parts, moderate-duty grates, 700–950 °C |
| 310S / S31008 | 25Cr 20Ni, low carbon | Radiant tubes, recuperators, 900–1100 °C cyclic service |
| 314 / S31400 | 25Cr 20Ni + 2% Si | Enhanced scale resistance, high-velocity hot gases |
| 330 / N08330 | 35Ni 19Cr | Carburizing furnaces, heat-treating fixtures, petrochemical |
The table is a starting point. Actual performance depends on the governing standard, delivered condition, dimensions, surface finish, fabrication route and service environment. Commercial names should never replace a complete purchase specification.
What Buyers Should Evaluate
- Name the atmosphere: clean air, sulfur-bearing flue gas, carburizing, reducing, or salt bath. Atmosphere, not temperature alone, decides the grade.
- Define the thermal cycle: steady state, rapid heat/cool, or daily shutdowns. Fatigue life and section size matter.
- Consider cast vs wrought; some burner nozzles or grate sections may only be available as investment cast HK30 or HH, not as wrought 310S.
When the duty involves continuous hot gas or cyclic heating, our guide to stainless steels for exhaust and high-temperature service and the stainless grade selection for heat exchangers help you match atmosphere and thermal cycling to the right grade before issuing an RFQ.
For production orders, share the end use rather than requesting a grade or finish in isolation. A supplier can then review corrosion exposure, forming severity, welding, visual requirements and packing before material is cut. This early review is usually less expensive than correcting a rejected shipment or unstable production trial.
Common Purchasing Mistakes
- Buying on temperature rating alone without considering cycling or sulfur content
- Using 310S with a standard 308L filler in a high-heat weld and getting cracking or premature failure
- Not accounting for sigma or 885 °F (475 °C) embrittlement when alloys spend long hold times in the 600–900 °C window
These mistakes are avoidable when drawings, approved samples, inspection methods and certificate requirements are agreed before production. For visual products, retain a signed master sample. For functional dimensions, define where and how measurements will be taken.
Recommended RFQ Wording
Include UNS or grade, product form (sheet, bar, tube, casting specification), temperature rating, atmosphere description, mechanical test at temperature (if required), NDT (UT/PT/RT for cast or weld-critical parts), and delivery solution-anneal condition.
Also include order quantity, acceptable quantity variation, destination, required delivery date and whether partial shipments are allowed. If a requirement is critical, make it measurable and place it on the purchase order rather than only in an email conversation.
How Still Steel Supports the Project
Still Steel supplies stainless steel coil, strip and sheet and provides slitting, cut-to-length, brushing, polishing and protective-film services. We can compare available mill material with your drawing, prepare trial quantities and preserve heat-number traceability through service-center processing.
Send the grade, dimensions, annual volume and application to vip@still-steel.com, or discuss the requirement on WhatsApp.
Frequently Asked Questions
Can 304 be used continuously at 900 °C?
304 is rated for intermittent service around 870 °C and continuous service to ~925 °C in clean air, but heavy cycling, sulfur-bearing gas or carburizing atmospheres push for 309S or 310S.
Why is 310S preferred over 309S for 1000+ °C?
310S has 25% Cr / 20% Ni (vs 23/13 for 309S), giving a more stable austenitic structure and higher resistance to oxidation, carburization and sigma-phase embrittlement at prolonged high temperatures.
What is 330 grade used for?
330 (UNS N08330) is a 35Ni-19Cr austenitic alloy with excellent carburization resistance, common in radiant tubes, heat-treating fixtures and cement-petrochemical equipment.
Technical References
Reference documents support general selection and fabrication principles. The final material decision must follow the applicable contract, standard, regulation and engineering review for the specific product.