Stainless Steel ER347Si
UNS S34780 · EN 19 9 Nb Si
ER347Si is a niobium-stabilized 19Cr-9Ni austenitic stainless welding wire (UNS S34780, 19 9 Nb Si) with elevated silicon for better arc wetting and puddle control in GMAW.
Reference datasheet — ER347Si 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 AW condition
ER347Si tempers and conditions
ER347Si is supplied in 5 conditions, soft to hard. AW is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Post-weld stabilizing anneal | Use when the joint will see long-term 400–800 °C service or aggressive acid media and maximum resistance to intergranular attack is required. | 350 | 570 | 42 | 170 HB | 2.4 % IACS |
As-welded, submerged-arc deposit with neutral/basic flux | For thick-section and cladding work at high deposition rate; properties depend strongly on flux, keep Nb/Si recovery and ferrite in check. | 385 | 585 | 34 | 180 HB | 2.4 % IACS |
As-welded, TIG deposit with Ar shielding | Choose for thin sections, root passes and cleanest deposits; highest ductility and toughness of the process options. | 395 | 595 | 40 | 185 HB | 2.4 % IACS |
AWDefault As-welded deposit | Default reported condition: undiluted all-weld-metal properties as deposited, no post-weld heat treatment. | 410 | 610 | 37 | 12 HRC | 2.4 % IACS |
As-welded, MIG/MAG spray or pulsed deposit | Main reason to pick 347Si over 347: high Si gives flat, well-wetted MIG beads and stable spray/pulse transfer at high deposition rates. | 420 | 620 | 35 | 195 HB | 2.4 % IACS |
Supply forms, finishes and certifications
Ways ER347Si is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WIRE-CD | Cold-drawn bright solid wire, as supplied on spool/coil | Supply form |
What is ER347Si?
ER347Si is a niobium-stabilized 19Cr-9Ni austenitic stainless welding wire (UNS S34780, 19 9 Nb Si) with elevated silicon for better arc wetting and puddle control in GMAW. It is chosen for joining 321, 347 and 304H where niobium stabilization prevents chromium carbide precipitation, and is supplied as cold-drawn spooled wire and cut lengths for GMAW, GTAW and SAW. As-welded deposits run about 410 MPa yield, 610 MPa tensile, 37% elongation and 190 HB, with service to 800 °C. The added silicon increases hot-crack sensitivity at high heat input; use standard ER347 where wetting is not the limiting factor. ER347Si 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). ER347Si has a yield strength of 410 MPa (59.5 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 60% of stainless steel grades. Elongation at break is 37% and the elastic modulus is 195 GPa (28.3 Msi).
What is ER347Si used for?
- Automated MIG welding of stabilized stainless
- Type 321 and 347 pipe and pressure vessel joints
- 304H high-temperature piping and headers
- Stabilized-to-stabilized stainless structural welds
- Furnace and flue ductwork fabrication
- Heat exchanger shell and nozzle welds
- Robotic welding of stainless exhaust and manifold assemblies
Advantages
- Readily welded — 95/100, better than 99% of stainless steel grades
Limitations
- High embodied carbon — 6.5 kg CO₂/kg, worse than 93% of stainless steel grades
ER347Si properties
Typical room-temperature values for ER347Si-AW; bars are the position among stainless steel grades.
Physical3
ER347Si 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).
Mechanical17
ER347Si has a yield strength of 410 MPa (59.5 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 60% of stainless steel grades. Elongation at break is 37% and the elastic modulus is 195 GPa (28.3 Msi).
Thermal6
ER347Si is rated for continuous service to 800°C (1,472 °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 16.5 µm/m·K (9.17 µin/in·°F).
Electrical3
ER347Si conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of ER347Si takes about 55 MJ of energy and emits 6.5 kg of CO₂ — more than 50% of stainless steel grades. Typical recycled content is 70%.
Manufacturability7
ER347Si's machinability is fair (38/100, better than 63% of stainless steel grades); weldability excellent (95/100); formability good (60/100).
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. ER347Si is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ER347Si
Is ER347Si easy to machine?
Weld metal machines like Type 347: gummy, work-hardening, needs sharp carbide tooling, rigid setup, positive rake, heavy coolant and low surface speed (~40% of 1212).
Can ER347Si be welded?
Use for 321/347/304H and stabilized-to-stabilized joints; keep interpass below ~150 °C, ferrite 4–10 FN, Ar or Ar+2% O₂/CO₂ (max ~2.5% CO₂) to protect Nb, avoid high heat input to limit hot-crack sensitivity from the higher Si.
Can ER347Si be formed, bent or molded?
Supplied as cold-drawn wire; deposit is fully ductile austenite and tolerates cold straightening/bending of the joint, but expect strong work hardening and springback.
ER347Si 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 |
|---|---|---|
| CAWS A5.9 max | ≤ 0.08 | 0.05 |
| Cr | 19 – 21.5 | 20 |
| Ni | 9 – 11 | 9.8 |
| NbNb+Ta; minimum = 10 × C per AWS A5.9 | ≤ 1 | 0.7 |
| Mn | 1 – 2.5 | 1.7 |
| Sihigh-Si variant — improves wetting | 0.65 – 1 | 0.85 |
| Moresidual | ≤ 0.75 | 0.15 |
| Curesidual | ≤ 0.75 | 0.15 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on ER347Si?
Pickle and passivate or electropolish weld area to restore the chromium oxide film; light ferrite in the bead can etch slightly darker and shows faint magnetism — no anodizing.
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 ER347Si in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S34780
- EN / DIN / Werkstoff-Nr.
- 19 9 Nb Si
How much does ER347Si cost?
ER347Si is a high-cost stainless steel ($$$$), pricier than about 78% 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.
ER347Si — frequently asked
What is ER347Si used for?
ER347Si is typically used for automated MIG welding of stabilized stainless, type 321 and 347 pipe and pressure vessel joints, 304H high-temperature piping and headers, stabilized-to-stabilized stainless structural welds, furnace and flue ductwork fabrication and heat exchanger shell and nozzle welds. In short: best-wetting stabilized austenitic filler; nb-stabilized for 321/347; deposit rated to 800 °C.
What is the yield strength of ER347Si?
ER347Si has a typical yield strength of 410 MPa (59.5 ksi) and a tensile strength of 610 MPa (88.5 ksi) — stronger than 60% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is ER347Si easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% of stainless steel grades). Weld metal machines like Type 347: gummy, work-hardening, needs sharp carbide tooling, rigid setup, positive rake, heavy coolant and low surface speed (~40% of 1212).
Can ER347Si be welded?
Yes — weldability is rated excellent (95/100). Use for 321/347/304H and stabilized-to-stabilized joints; keep interpass below ~150 °C, ferrite 4–10 FN, Ar or Ar+2% O₂/CO₂ (max ~2.5% CO₂) to protect Nb, avoid high heat input to limit hot-crack sensitivity from the higher Si.
What surface finishes work on ER347Si?
Pickle and passivate or electropolish weld area to restore the chromium oxide film; light ferrite in the bead can etch slightly darker and shows faint magnetism — no anodizing.
Can ER347Si be formed, bent or molded?
Supplied as cold-drawn wire; deposit is fully ductile austenite and tolerates cold straightening/bending of the joint, but expect strong work hardening and springback.
What is the maximum service temperature of ER347Si?
ER347Si 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.
What is the difference between ER347Si-AW and ER347Si PWHT-SA?
AW is the default condition — default reported condition: undiluted all-weld-metal properties as deposited, no post-weld heat treatment. PWHT-SA: use when the joint will see long-term 400–800 °C service or aggressive acid media and maximum resistance to intergranular attack is required. Yield strength is 410 MPa in AW versus 350 MPa in PWHT-SA.
How much does ER347Si cost?
ER347Si is a high-cost stainless steel ($$$$), pricier than about 78% 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
- AWS A5.9/A5.9M — Bare Stainless Steel Welding Electrodes and Rods — American Welding Society (2017)
- ASME BPVC Section II Part C, SFA-5.9 — ASME (2023)
- ISO 14343 (19 9 Nb Si) — Welding consumables, wire electrodes for stainless steels — ISO (2017)
- ASM Handbook Vol.1 — Properties of Wrought Stainless Steels (Type 347) — ASM International (1990)
- ASM Handbook Vol.6 — Welding of Stainless Steels — ASM International (1993)
- 347Si / 19 9 Nb Si solid wire datasheets (all-weld-metal typicals) — Böhler Welding / Sandvik / Lincoln Electric (2023)
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.