Stainless Steel 347-1/4 Hard
Supply condition
AISI/SAE 347 · UNS S34700 · ASTM A240 TP347 · EN 1.4550, X6CrNiNb18-10 · JIS SUS347
1/4 Hard = quarter hard
Light temper rolling where extra stiffness is needed but some bending is still required.
Values for the 1/4 Hard 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 |
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 |
1/4 HardThis page 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 347-1/4 Hard?
347-1/4 Hard is 347 supplied in the 1/4 Hard condition — light temper rolling where extra stiffness is needed but some bending is still required. 347-1/4 Hard has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 83% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 193 GPa (28 Msi). 347-1/4 Hard 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; 1/4 Hard is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 80/100, better than 89% of stainless steel grades
- Readily welded — 85/100, better than 87% of stainless steel grades
- High strength — 550 MPa (79.8 ksi), better than 83% of stainless steel grades
Limitations
- Limited ductility — 12%, worse than 95% of stainless steel grades
- High embodied carbon — 5.5 kg CO₂/kg, worse than 77% of stainless steel grades
347-1/4 Hard properties
Typical room-temperature values for 347-1/4 Hard; 24 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
347-1/4 Hard 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
347-1/4 Hard has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 83% of stainless steel grades. Elongation at break is 12% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
347-1/4 Hard is rated for continuous service to 425°C (797 °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
347-1/4 Hard conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (66/100), better than 59% of stainless steel grades.
Sustainability4
Producing a kilogram of 347-1/4 Hard 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
347-1/4 Hard's machinability is fair (40/100, better than 72% of stainless steel grades); weldability excellent (85/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 347-1/4 Hard
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 | — |
347-1/4 Hard — frequently asked
What is 347-1/4 Hard used for?
347-1/4 Hard 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 347-1/4 Hard?
347-1/4 Hard has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 83% of stainless steel grades. Strength varies by condition: see the 10 listed tempers.
Is 347-1/4 Hard easy to machine?
Not especially — machinability is rated fair (40/100, better than 72% 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 347-1/4 Hard be welded?
Yes — weldability is rated excellent (85/100). 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 347-1/4 Hard?
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 347-1/4 Hard 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 347-1/4 Hard?
347-1/4 Hard is rated for continuous use to about 425°C (797 °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 347-1/4 Hard?
Yes — 347-1/4 Hard 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.