Stainless Steel 347H Stabilize Annealed
Heat-treated state
AISI/SAE 347H · UNS S34709 · ASTM A240 TP347H
Specify when maximum immunity to intergranular / polythionic-acid attack and knife-line attack is required in refinery service.
Values for the Stabilize Annealed condition
Other 347H tempers and conditions
347H is listed in 5 conditions; see the grade overview at 347H.
- Hot Finished
- Annealed
- Solution Annealed
- Stabilize Annealed
- Cold Drawn
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Finished (hot rolled, annealed and descaled) bar / seamless pipe | Economical large-section bar and seamless pipe; slightly coarser surface and marginally lower strength than cold-worked product. | 250 | 585 | 45 | 170 HB | 2.4 % IACS |
mill-annealed bar/forging condition | Bar, forgings and fittings delivered fully annealed when softness and machining/forming ease matter more than strength. | 255 | 600 | 50 | 150 HB | 2.4 % IACS |
Solution AnnealedDefault 1040–1120 °C, rapid cool (ASTM A240/A213 delivery condition) | Standard as-supplied condition for plate, tube and pipe; maximum ductility and corrosion resistance, ASME-code creep properties. | 275 | 620 | 45 | 160 HB | — |
Stabilize AnnealedThis page 885–950 °C hold after solution anneal or welding | Specify when maximum immunity to intergranular / polythionic-acid attack and knife-line attack is required in refinery service. | 280 | 615 | 43 | 165 HB | 2.4 % IACS |
Cold Drawn / cold finished bar (ASTM A484 condition B) | Choose for close-tolerance small-diameter bar, higher yield strength and better surface for machined fittings and studs. | 520 | 790 | 28 | 225 HB | — |
What is 347H Stabilize Annealed?
347H Stabilize Annealed is 347H heat treated to Stabilize Annealed — specify when maximum immunity to intergranular / polythionic-acid attack and knife-line attack is required in refinery service. 347H Stabilize Annealed has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 615 MPa (89.2 ksi) — weaker than 75% of stainless steel grades. Elongation at break is 43% and the elastic modulus is 195 GPa (28.3 Msi). 347H Stabilize Annealed has a density of 7.96 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,400°C (2,552 °F). Solution Annealed is the default condition FabDigit quotes; Stabilize Annealed is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- Readily welded — 80/100, better than 80% of stainless steel grades
- High service temperature — 815°C (1,499 °F), better than 77% of stainless steel grades
Limitations
- Low strength — 280 MPa (40.6 ksi), worse than 75% of stainless steel grades
347H Stabilize Annealed properties
Typical room-temperature values for 347H Stabilize Annealed; 22 are specific to this condition. Other listed values are 347H reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
347H Stabilize Annealed has a density of 7.96 g/cm³ (0.288 lb/in³), heavier than 83% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
347H Stabilize Annealed has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 615 MPa (89.2 ksi) — weaker than 75% of stainless steel grades. Elongation at break is 43% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
347H Stabilize Annealed is rated for continuous service to 815°C (1,499 °F). It conducts heat at 16.1 W/m·K (9.3 BTU/hr·ft·°F), better than 61% of stainless steel grades. Thermal expansion is 16.6 µm/m·K (9.22 µin/in·°F).
Electrical3
347H Stabilize Annealed conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 58% of stainless steel grades.
Sustainability4
Producing a kilogram of 347H Stabilize Annealed takes about 60 MJ of energy and emits 5.3 kg of CO₂ — more than 70% of stainless steel grades. Typical recycled content is 60%.
Manufacturability8
347H Stabilize Annealed's machinability is poor (33/100, worse than 57% of stainless steel grades); weldability very good (80/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 347H Stabilize Annealed
Is 347H easy to machine?
Machine like 321/304 but expect abrasive NbC: rigid setup, sharp coated carbide, 25–60 m/min, heavy positive feed to cut through the work-hardened skin, flood coolant, no dwelling.
Can 347H be welded?
Readily welded by GTAW/GMAW/SMAW with ER347/E347 filler (ER16-8-2 for thick multipass creep service); low heat input, no preheat, keep interpass low to limit hot cracking, and add a 900 °C stabilizing anneal where knife-line attack or polythionic SCC is a risk.
Can 347H be formed, bent or molded?
Cold forms well but work-hardens fast — allow ~50 % more press force than mild steel, generous bend radii, and interstage annealing; hot work at 1150–1200 °C and always solution anneal afterwards.
What surface finishes work on 347H?
Pickle and passivate (ASTM A380/A967) or electropolish after fabrication to restore the chromium oxide film; takes a good mechanical or mirror polish, never anodized, and can be Ni-brazed in vacuum or dry hydrogen.
347H chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cdeliberately high for creep strength (H grade) | 0.04 – 0.1 | 0.06 |
| Si1.00 max in some product standards | ≤ 0.75 | 0.5 |
| Mn | ≤ 2 | 1.5 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Cr | 17 – 19 | 18 |
| Ni | 9 – 13 | 11 |
| NbNb(+Ta) ≥ 8 × C per ASTM A240/A213; min shown for C = 0.04 | 0.32 – 1 | 0.6 |
| Fe | balance | — |
347H Stabilize Annealed — frequently asked
What is 347H Stabilize Annealed used for?
347H Stabilize Annealed is typically used for boiler and superheater tubing, refinery heater and reformer piping, power plant steam headers, high-temperature pressure vessels, petrochemical reactor internals and expansion joints and bellows. In short: high-temp niobium-stabilized stainless.
What is the yield strength of 347H Stabilize Annealed?
347H Stabilize Annealed has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 615 MPa (89.2 ksi) — weaker than 75% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 347H Stabilize Annealed easy to machine?
Not especially — machinability is rated poor (33/100, worse than 57% of stainless steel grades). Machine like 321/304 but expect abrasive NbC: rigid setup, sharp coated carbide, 25–60 m/min, heavy positive feed to cut through the work-hardened skin, flood coolant, no dwelling.
Can 347H Stabilize Annealed be welded?
Yes — weldability is rated very good (80/100). Readily welded by GTAW/GMAW/SMAW with ER347/E347 filler (ER16-8-2 for thick multipass creep service); low heat input, no preheat, keep interpass low to limit hot cracking, and add a 900 °C stabilizing anneal where knife-line attack or polythionic SCC is a risk.
What surface finishes work on 347H Stabilize Annealed?
Pickle and passivate (ASTM A380/A967) or electropolish after fabrication to restore the chromium oxide film; takes a good mechanical or mirror polish, never anodized, and can be Ni-brazed in vacuum or dry hydrogen.
Can 347H Stabilize Annealed be formed, bent or molded?
Cold forms well but work-hardens fast — allow ~50 % more press force than mild steel, generous bend radii, and interstage annealing; hot work at 1150–1200 °C and always solution anneal afterwards.
What is the maximum service temperature of 347H Stabilize Annealed?
347H Stabilize Annealed is rated for continuous use to about 815°C (1,499 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 347H Stabilize Annealed?
Yes — 347H Stabilize Annealed is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip — ASTM International (2023)
- ASTM A213/A213M — Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — ASTM International (2022)
- ASTM A312/A312M and A479/A484 (S34709 pipe and bar) — ASTM International (2022)
- ASME BPVC Section II Part D — allowable stresses for SA-213 TP347H — ASME (2023)
- GB/T 1220 / GB/T 24593 (0Cr18Ni11Nb, 07Cr18Ni11Nb) — SAC (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Sandvik / Alleima 347H and Outokumpu 4550 datasheets — Alleima, Outokumpu (2023)
- (SMM / Mysteel / 1688 ) (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.