304H Stainless Steel: High-Carbon Grade for High-Temperature Service

304H is the high-carbon variant of 304 stainless steel, with carbon controlled between 0.04% and 0.10% (UNS S30409). At elevated temperatures, higher carbon content improves creep strength and structural stability, which is why 304H is specified for components that carry stress at temperature - boiler superheaters, furnace internals, high-temperature fan blades and similar parts. Its room-temperature corrosion resistance is similar to 304, but its performance retention at high temperature is significantly better.

 

 

 

1.Creep strength: in the 500–800°C range, 304H shows markedly higher creep strength than standard 304 - a typical engineering comparison is on the order of 2–3 times creep rupture life, but the actual ratio depends on temperature, stress and product form; verify with measured data where design is critical.

2.Oxidation resistance: equivalent to 304 - good resistance to oxidation and scaling at continuous service temperatures, with oxidation rate increasing with temperature (an oxidation rate on the order of 0.1 mm/year at about 800°C is a typical engineering figure, not a guaranteed value).

3.Weldability: good; use matching ER308H filler to preserve high-temperature performance of the weld, control heat input to limit carbide precipitation, and perform post-weld annealing (about 1050°C) where service conditions require it.

 

1.Power‑plant Boiler Components (Primary Application)

Boiler superheater tubes, reheater tubes and headers for high‑pressure steam service. Controlled carbon content provides excellent high‑temperature creep‑rupture strength, widely used in thermal power and waste‑heat recovery boilers.

2.High‑Temperature Heat‑Exchange Systems for Power Stations

Heat‑exchanger tube bundles and flue‑gas heat‑transfer pipes operating under high temperature and pressure.

3.Petrochemical High‑Temperature Process Equipment

Furnace tubes, high‑temperature process piping and heat exchangers for oxidizing high‑temperature atmospheres. Not suitable for strongly reducing high‑sulfur environments.

4.Pressure‑bearing Components for Industrial Furnaces

High‑temperature furnace piping and pressure‑resistant internals for service at 800‑850 ℃ under oxidizing conditions.

5.High‑Temperature Pressure Vessels & Piping

Vessel shells and process piping requiring reliable creep‑rupture performance at elevated temperatures.

304H is the high-carbon, high-temperature variant of 304, specified for stress-bearing components in the 500–870°C range. Its higher carbon content delivers the creep strength that standard 304 lacks at temperature, at the cost of slightly reduced cold formability and higher sensitization risk on welding. Confirm the grade designation (UNS S30409) against the applicable standard, verify quantitative creep and oxidation data for the specific product, and manage welding heat input carefully.