Stainless Steel 347H · temper
Stainless Steel 347H Annealed
Properties of the Annealed condition, compared with the other 347H tempers.
Bar, forgings and fittings delivered fully annealed when softness and machining/forming ease matter more than strength.
What is 347H Annealed?
347H Annealed is 347H in the Annealed temper — bar, forgings and fittings delivered fully annealed when softness and machining/forming ease matter more than strength. 347H Annealed has a yield strength of 255 MPa (37 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi). 347H Annealed has a density of 7.96 g/cm³ (0.288 lb/in³), heavier than 82% of stainless steel grades. It melts at 1,400°C (2,552 °F). Solution Annealed is the default condition FabDigit quotes; Annealed is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 50%, better than 90% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 84% of stainless steel grades
- Forms and bends easily — 70/100, better than 78% of stainless steel grades
- High service temperature — 815°C (1,499 °F), better than 77% of stainless steel grades
Limitations
- Low strength — 255 MPa (37 ksi), worse than 87% of stainless steel grades
347H Annealed properties
Typical room-temperature values for 347H Annealed — 9 properties are specific to this condition; the rest are grade-level values shared by every 347H temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.
Physical3
347H Annealed has a density of 7.96 g/cm³ (0.288 lb/in³), heavier than 82% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
347H Annealed has a yield strength of 255 MPa (37 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 87% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
347H 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 Annealed conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (57/100), worse than 66% of stainless steel grades.
Sustainability4
Producing a kilogram of 347H 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 Annealed's machinability is fair (35/100, better than 51% of stainless steel grades); weldability very good (78/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 347H tempers and conditions
347H is also supplied in 4 other conditions. The full side-by-side table is on the 347H overview.
- Solution AnnealedDefaultStandard as-supplied condition for plate, tube and pipe; maximum ductility and corrosion resistance, ASME-code creep properties.275 MPa yield · 160 HB
- Cold DrawnChoose for close-tolerance small-diameter bar, higher yield strength and better surface for machined fittings and studs.520 MPa yield · 225 HB
- AnnealedBar, forgings and fittings delivered fully annealed when softness and machining/forming ease matter more than strength.255 MPa yield · 150 HB
Working with 347H 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 Annealed — frequently asked
What is 347H Annealed used for?
347H 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 Annealed?
347H Annealed has a typical yield strength of 255 MPa (37 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 87% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 347H Annealed easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% 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 Annealed be welded?
Yes — weldability is rated very good (78/100). 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 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 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 Annealed?
347H 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 Annealed?
Yes — 347H Annealed is available for CNC machining and sheet metal with instant online pricing. 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.