Stainless Steel 347LN
AISI/SAE 347LN · UNS S34751
347LN (UNS S34751) is a low-carbon, nitrogen-enhanced niobium-stabilized austenitic stainless steel in the 347 family, using Nb stabilization plus very low carbon to resist sensitization while nitrogen restores strength.
Reference datasheet — 347LN is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the Annealed condition
347LN tempers and conditions
347LN is supplied in 8 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed 1040–1120 °C, rapid quenched | Standard supply condition for plate, pipe, tube, bar and forgings; maximum corrosion resistance and ductility for nuclear/pressure service. | 290 | 620 | 50 | 160 HB | — |
880–930 °C hold after solution anneal | Chosen for severe hot nitric-acid or long high-temperature service where all residual carbon must be tied up as NbC. | 300 | 610 | 45 | 165 HB | 2.4 % IACS |
As-welded deposit (ER347 / E347 type filler, no PWHT) | Design basis for weld metal and HAZ in nuclear/piping joints welded without post-weld solution anneal. | 400 | 600 | 35 | 180 HB | 2.3 % IACS |
Cold drawn / cold finished bar (annealed + drawn) | Bar and tube where tighter tolerance, better surface and higher yield strength are needed than annealed. | 500 | 720 | 30 | 16 HRC | 2.4 % IACS |
Quarter hard | Light cold-rolled temper for springy sheet parts still needing appreciable forming ability. | 545 | 880 | 12 | 25 HRC | 2.4 % IACS |
Half hard | Structural sheet, clamps and springs where strength outweighs formability. | 790 | 1,060 | 10 | 32 HRC | 2.4 % IACS |
Three-quarter hard | High-strength strip for flat springs and shims with only simple bends. | 960 | 1,230 | 7 | 37 HRC | 2.4 % IACS |
heavily cold rolled strip per ASTM A666 | Maximum strength thin strip; essentially no forming beyond flat blanking. | 1,000 | 1,300 | 4 | 40 HRC | 2.4 % IACS |
What is 347LN?
347LN (UNS S34751) is a low-carbon, nitrogen-enhanced niobium-stabilized austenitic stainless steel in the 347 family, using Nb stabilization plus very low carbon to resist sensitization while nitrogen restores strength. Annealed material gives 290 MPa yield, 620 MPa tensile, 50 % elongation and 160 HB (83 HRB), with service to 800 °C; it is supplied annealed or stabilize-annealed as plate, sheet, tube and cold-drawn or cold-worked bar. Weldability is high (score 88) with no post-weld anneal required, but NbC particles are abrasive and general corrosion resistance (score 68) is no better than 304-class in chlorides. Use 316L or 317L where chloride pitting governs. 347LN has a density of 7.95 g/cm³ (0.287 lb/in³), heavier than 81% of stainless steel grades. It melts at 1,400°C (2,552 °F). 347LN has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi).
What is 347LN used for?
- Nuclear primary and secondary piping
- High-pressure welded piping systems
- Superheater and reheater tubing
- Pressure vessel shells and nozzles
- Steam headers and manifolds
- Welded expansion joints and bellows
- High-integrity flanges and fittings
Advantages
- Readily welded — 88/100, better than 91% of stainless steel grades
- Ductile — tolerates forming and impact — 50%, better than 90% of stainless steel grades
- Forms and bends easily — 78/100, better than 90% of stainless steel grades
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 86% of stainless steel grades
347LN properties
Typical room-temperature values for 347LN-Annealed; bars are the position among stainless steel grades.
Physical3
347LN has a density of 7.95 g/cm³ (0.287 lb/in³), heavier than 81% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
347LN has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
347LN is rated for continuous service to 800°C (1,472 °F). It conducts heat at 16.2 W/m·K (9.36 BTU/hr·ft·°F), better than 64% of stainless steel grades. Thermal expansion is 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
347LN conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 63% of stainless steel grades.
Sustainability4
Producing a kilogram of 347LN takes about 53 MJ of energy and emits 5.2 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 60%.
Manufacturability8
347LN's machinability is fair (38/100, better than 63% of stainless steel grades); weldability excellent (88/100); formability very good (78/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 347LN is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 347LN
Is 347LN easy to machine?
Cut like 347/321 — rigid setups, sharp positive-rake carbide, heavy flood coolant, 20–30 % lower speed than 304 because NbC particles are abrasive and chips are stringy.
Can 347LN be welded?
Excellent: GTAW/GMAW/SMAW with ER347/E347 (or Nb-free 316L only where allowed); low heat input, interpass ≤150 °C, no post-weld anneal needed thanks to ultra-low C plus Nb.
Can 347LN be formed, bent or molded?
Very ductile hot (1150–1250 °C) and cold, but work-hardens fast — allow for springback, use interstage anneals for deep draws and avoid stopping hot work below ~900 °C.
347LN 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 |
|---|---|---|
| Cultra-low carbon, controlled range | 0.01 – 0.02 | 0.01 |
| Nnitrogen-strengthened | 0.06 – 0.1 | 0.08 |
| Cr | 17 – 19 | 18 |
| Ni | 9 – 13 | 10.5 |
| Nbstabiliser; standard requires ≥15×C (Nb+Ta basis in some specs) | 0.2 – 1 | 0.4 |
| Mn | ≤ 2 | 1.5 |
| Si | ≤ 1 | 0.5 |
| P | ≤ 0.05 | |
| Snuclear orders often restrict S ≤0.015 and Co ≤0.05 | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 347LN?
Pickle (HNO₃/HF) or electropolish after fabrication and passivate per ASTM A967; polishes to a mirror finish; never anodised, and avoid iron contamination from carbon-steel tooling.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 347LN in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S34751
How much does 347LN cost?
347LN is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
347LN — frequently asked
What is 347LN used for?
347LN is typically used for nuclear primary and secondary piping, high-pressure welded piping systems, superheater and reheater tubing, pressure vessel shells and nozzles, steam headers and manifolds and welded expansion joints and bellows. In short: stabilized, sensitization-resistant 347; nitrogen-boosted weld strength; nuclear-grade piping choice.
What is the yield strength of 347LN?
347LN has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 72% of stainless steel grades. Strength varies by condition: see the 8 listed tempers.
Is 347LN easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% of stainless steel grades). Cut like 347/321 — rigid setups, sharp positive-rake carbide, heavy flood coolant, 20–30 % lower speed than 304 because NbC particles are abrasive and chips are stringy.
Can 347LN be welded?
Yes — weldability is rated excellent (88/100). Excellent: GTAW/GMAW/SMAW with ER347/E347 (or Nb-free 316L only where allowed); low heat input, interpass ≤150 °C, no post-weld anneal needed thanks to ultra-low C plus Nb.
What surface finishes work on 347LN?
Pickle (HNO₃/HF) or electropolish after fabrication and passivate per ASTM A967; polishes to a mirror finish; never anodised, and avoid iron contamination from carbon-steel tooling.
Can 347LN be formed, bent or molded?
Very ductile hot (1150–1250 °C) and cold, but work-hardens fast — allow for springback, use interstage anneals for deep draws and avoid stopping hot work below ~900 °C.
What is the maximum service temperature of 347LN?
347LN is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 347LN cost?
347LN is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip (UNS S34751) — ASTM International (2023)
- ASTM A312/A312M — Seamless and Welded Austenitic Stainless Steel Pipes — ASTM International (2022)
- ASTM A666 — Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate and Flat Bar — ASTM International (2015)
- ASME BPVC Section II Part D — Material Properties (physical/allowable stress tables for 347 group) — ASME (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- EN 10088-2 / 1.4550 (X6CrNiNb18-10) stabilised austenitic stainless — CEN (2014)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.