Stainless Steel 347H
Grade
AISI/SAE 347 · UNS S34700 · ASTM A240 TP347 · EN 1.4550, X6CrNiNb18-10 · JIS SUS347
347H = high-carbon (0.04–0.10 % C) variant, solution annealed ≥1050 °C
Pick for ASME code creep service above 540 °C — higher allowable stresses and better rupture life than plain 347.
Values for the 347H condition
Other 347 tempers and conditions
347 is listed in 10 conditions; see the grade overview at 347.
- Annealed
- Hot Finished
- 347H
- Solution Annealed
- Stabilize Annealed
- As Welded
- Cold Drawn
- 1/4 Hard
- 1/2 Hard
- Full Hard
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
softened condition (sheet/strip/wire, equivalent to solution annealed) | Soft sheet, strip and wire for forming, spinning and cold heading. | 240 | 600 | 48 | 155 HB | 2.4 % IACS |
Hot Finished / Hot Rolled Annealed bar (ASTM A276) | Economical large-section bar and plate for machined weldments and hot-service piping supports. | 240 | 600 | 42 | 165 HB | 2.4 % IACS |
347HThis page High-carbon (0.04–0.10 % C) variant, solution annealed ≥1050 °C | Pick for ASME code creep service above 540 °C — higher allowable stresses and better rupture life than plain 347. | 240 | 620 | 45 | 165 HB | 2.4 % IACS |
Solution AnnealedDefault 1010–1120 °C, rapid cool (ASTM A240/A276 standard delivery) | Default stock condition for plate, sheet, bar, pipe and tube — maximum ductility and corrosion resistance. | 245 | 620 | 45 | 160 HB | — |
870–900 °C hold after solution anneal | Extra Nb-carbide precipitation treatment for parts exposed to severe intergranular-corrosion service (nitric acid, long hot holds). | 255 | 615 | 43 | 165 HB | 2.4 % IACS |
ER347 / E347 weld metal deposit | Matching filler deposit condition; used for as-welded design values in stabilized 18-8 joints. | 400 | 600 | 35 | 180 HB | 2.4 % IACS |
Cold Drawn / Cold Finished bar (ASTM A484, ~10–20 % reduction) | Higher strength, tighter tolerance and better surface for screw-machine parts and fasteners. | 550 | 760 | 25 | 23 HRC | 2.4 % IACS |
Quarter hard | Light temper rolling where extra stiffness is needed but some bending is still required. | 550 | 900 | 12 | 25 HRC | 2.4 % IACS |
Half hard | Springy strip for clamps, shims and gasket/bellows plies that see little forming. | 790 | 1,035 | 9 | 32 HRC | 2.3 % IACS |
heavily cold rolled strip (≈ 965 MPa min yield) | Maximum strength flat product for flat springs and diaphragms; essentially no forming capability. | 1,000 | 1,275 | 6 | 38 HRC | 2.3 % IACS |
What is 347H?
347H is 347 in the 347H grade — pick for ASME code creep service above 540 °C — higher allowable stresses and better rupture life than plain 347. 347H has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 96% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi). 347H 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; 347H is available on request or by drawing note.
Advantages
- Readily welded — 88/100, better than 91% of stainless steel grades
- Forms and bends easily — 78/100, better than 90% of stainless steel grades
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
- High service temperature — 900°C (1,652 °F), better than 85% of stainless steel grades
Limitations
- Low strength — 240 MPa (34.8 ksi), worse than 96% of stainless steel grades
- High embodied carbon — 5.5 kg CO₂/kg, worse than 77% of stainless steel grades
347H properties
Typical room-temperature values for 347H; 22 are specific to this condition. Other listed values are 347 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
347H 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).
Mechanical16
347H has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 96% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
347H is rated for continuous service to 900°C (1,652 °F). It conducts heat at 16 W/m·K (9.24 BTU/hr·ft·°F), better than 58% of stainless steel grades. Thermal expansion is 16.6 µm/m·K (9.22 µin/in·°F).
Electrical3
347H conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (65/100), better than 56% of stainless steel grades.
Sustainability4
Producing a kilogram of 347H takes about 57 MJ of energy and emits 5.5 kg of CO₂ — more than 62% of stainless steel grades. Typical recycled content is 60%.
Manufacturability7
347H's machinability is fair (36/100, better than 57% of stainless steel grades); weldability excellent (88/100); formability very good (78/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 347H
Is 347 easy to machine?
Gummy and work-hardening with abrasive NbC particles — use rigid setups, positive-rake coated carbide, heavy constant feed, no dwelling, and flood coolant; ~40 % of 1212 speeds.
Can 347 be welded?
Excellent by GTAW/GMAW/SMAW with ER347/E347 filler; the Nb stabilization means no post-weld solution anneal is needed, but keep heat input low and interpass < 150 °C to limit distortion and hot-cracking risk.
Can 347 be formed, bent or molded?
Cold forms and deep draws well but work-hardens faster than 304 — allow extra power, generous radii and intermediate anneals at 1010–1120 °C followed by rapid cooling.
What surface finishes work on 347?
Passivate per ASTM A967 or electropolish after machining; not anodizable — bead blast, No.4 brush or mirror polish are the usual finishes, and pickling paste removes weld heat tint.
347 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 |
|---|---|---|
| C347H: 0.04–0.10 | ≤ 0.08 | 0.05 |
| Mn | ≤ 2 | 1.5 |
| Si | ≤ 0.75 | 0.5 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 17 – 19 | 18 |
| Ni | 9 – 13 | 11 |
| NbNb(+Ta) ≥ 10×C; EN 1.4550 requires Nb ≥ 10×C, max 1.00 | ≤ 1 | 0.6 |
| Talimited only in nuclear/Co-controlled orders | ≤ 0.1 | — |
| NEN 1.4550 limit | ≤ 0.1 | 0.04 |
| Fe | balance | — |
347H — frequently asked
What is 347H used for?
347H is typically used for boiler and superheater piping, refinery and petrochemical process piping, exhaust systems and expansion bellows, welded pressure vessels for hot service, heat exchanger tubes and tubesheets and aircraft collector rings and ducting. In short: niobium-stabilized austenitic stainless.
What is the yield strength of 347H?
347H has a typical yield strength of 240 MPa (34.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 96% of stainless steel grades. Strength varies by condition: see the 10 listed tempers.
Is 347H easy to machine?
Not especially — machinability is rated fair (36/100, better than 57% of stainless steel grades). Gummy and work-hardening with abrasive NbC particles — use rigid setups, positive-rake coated carbide, heavy constant feed, no dwelling, and flood coolant; ~40 % of 1212 speeds.
Can 347H be welded?
Yes — weldability is rated excellent (88/100). Excellent by GTAW/GMAW/SMAW with ER347/E347 filler; the Nb stabilization means no post-weld solution anneal is needed, but keep heat input low and interpass < 150 °C to limit distortion and hot-cracking risk.
What surface finishes work on 347H?
Passivate per ASTM A967 or electropolish after machining; not anodizable — bead blast, No.4 brush or mirror polish are the usual finishes, and pickling paste removes weld heat tint.
Can 347H be formed, bent or molded?
Cold forms and deep draws well but work-hardens faster than 304 — allow extra power, generous radii and intermediate anneals at 1010–1120 °C followed by rapid cooling.
What is the maximum service temperature of 347H?
347H is rated for continuous use to about 900°C (1,652 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 347 Solution Annealed and 347H?
Solution Annealed is the default condition — default stock condition for plate, sheet, bar, pipe and tube — maximum ductility and corrosion resistance. 347H: pick for ASME code creep service above 540 °C — higher allowable stresses and better rupture life than plain 347. Yield strength is 245 MPa in Solution Annealed versus 240 MPa in 347H.
Can FabDigit make parts in 347H?
Yes — 347H 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 — Cr and Cr-Ni Stainless Plate, Sheet and Strip — ASTM International (2023)
- ASTM A276/A276M — Stainless Steel Bars and Shapes — ASTM International (2023)
- EN 10088-2 — Stainless steels, technical delivery conditions for sheet/plate (1.4550) — CEN (2014)
- GB/T 1220 / GB/T 4237 (0Cr18Ni11Nb) — SAC (2015)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- 347/347H Stainless Steel Product Data Sheet — AK Steel / Cleveland-Cliffs (2021)
- Outokumpu Steel Grade 4550 datasheet — Outokumpu (2022)
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.