310S 321 347H Stainless Steel Seamless Boiler Tubing for High Temperature Power

Our high temperature and pressure resistant stainless steel seamless pipes are engineered for critical service in power generation, petrochemical reforming, and industrial boiler applications where operating temperatures routinely exceed 600°C and design pressures reach 250 barg or higher. Available in ASTM A312 TP310S, TP321, TP321H, TP347, and TP347H, these austenitic stainless steel grades provide exceptional creep strength, oxidation resistance, and microstructural stability under sustained thermal and mechanical loading.

Product Specifications

High Temperature Properties by Grade

Creep and Stress Rupture Data

Application Scenarios

Power Generation - Superheater and Reheater Tubes

In coal-fired, gas-fired, and combined-cycle power plants, superheater and reheater tubes operate at steam temperatures of 540-620°C and pressures of 160-250 barg. TP347H is the preferred material for the hottest sections due to its superior creep-rupture strength and resistance to steam-side oxidation. TP321H is commonly specified in intermediate temperature zones (450-540°C) where the Ti-stabilized microstructure prevents sensitization during field welding without requiring post-weld heat treatment.

Petrochemical - Reformer Furnace Tubes and Transfer Lines

Steam methane reforming (SMR) furnaces operate with tube metal temperatures reaching 850-950°C at the hot face. TP310S seamless pipes are used in convection section transfer lines and hot collector headers where high chromium (24-26%) and nickel (19-22%) content provides essential oxidation and carburization resistance in flue gas environments containing CO, CO2, and H2O.

Industrial Boilers - Water Wall and Economizer Piping

High-pressure industrial boilers serving chemical plants, refineries, and district heating networks demand piping that withstands both thermal cycling and internal corrosion from treated boiler feedwater. TP321 and TP321H pipes provide the necessary combination of weldability, creep strength, and resistance to flow-accelerated corrosion (FAC) in two-phase regions.

Heat Recovery Steam Generators (HRSG)

Combined-cycle HRSG units subject tube bundles to rapid temperature transients during daily start-stop cycling. TP347H's niobium-stabilized microstructure and higher creep ductility make it the grade of choice for high-pressure evaporator and superheater harp assemblies. The material tolerates the thermal fatigue associated with frequent cycling better than ferritic grades like T91 in the same temperature range.

Ethylene Cracking Furnaces

Cracking furnace convection sections operate at tube metal temperatures of 700-850°C in hydrocarbon-rich atmospheres. TP310S provides exceptional resistance to metal dusting and carburization - degradation mechanisms that can reduce tube wall thickness by 0.5-1.0 mm/year in lower-grade stainless steels.

Mechanical Properties at Elevated Temperature

Quality Assurance

• Solution Annealing Verification: 100% metallographic examination on sample tubes from each heat to confirm fully recrystallized austenitic grain structure (ASTM grain size 4-7 for H-grade)
• Grain Size Control: TP321H and TP347H tubes are tested per ASTM E112 to ensure grain size 7 or coarser per ASME SA312 requirements, directly affecting creep performance
• Stabilization Ratio: For TP321/321H: Ti/C ratio ≥5 per ASTM A312. For TP347/347H: Nb+Ta/C ratio ≥10 per ASTM A312
• Ultrasonic Testing (UT): 100% UT per ASTM A388/A388M for wall thickness ≥6.35 mm; ASTM E213 for thinner walls
• Hydrostatic Test: Each pipe tested at 1.5 times the calculated design pressure; extended hold times (30 seconds minimum) applied for heavy-wall pipe
• Flattening and Flaring Tests: Mechanical workability verified per ASTM A312/A312M on samples from each heat
• Intergranular Corrosion Test: ASTM A262 Practice E (Strauss test) performed on stabilized grades after sensitizing heat treatment at 675°C for 1 hour to verify Ti/Nb stabilization effectiveness
• Mill Test Reports: EN 10204 Type 3.1 MTR includes full heat chemistry, mechanical properties at room and elevated temperature, grain size, and stabilization ratio

FAQ

Need a material recommendation for your high-temperature piping system? Send us your design temperature, pressure, and service fluid composition. Our application engineers will provide a grade recommendation within 24 hours, complete with ASME allowable stress verification.