Stainless Steel 348 · grade
Stainless Steel 348H
Properties of the 348H condition, compared with the other 348 tempers.
Specify when ASME creep allowables above ~540 °C are needed; coarser grain size and higher carbon give better long-term rupture strength.
What is 348H?
348H is 348 in the 348H grade — specify when ASME creep allowables above ~540 °C are needed; coarser grain size and higher carbon give better long-term rupture strength. 348H has a yield strength of 245 MPa (35.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 94% of stainless steel grades. Elongation at break is 43% and the elastic modulus is 193 GPa (28 Msi). 348H 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). Annealed is the default condition FabDigit quotes; 348H is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 220 MPa·√m (200.2 ksi·√in), better than 97% of stainless steel grades
- Forms and bends easily — 80/100, better than 93% of stainless steel grades
- Readily welded — 85/100, better than 86% of stainless steel grades
- High service temperature — 900°C (1,652 °F), better than 84% of stainless steel grades
Limitations
- Low strength — 245 MPa (35.5 ksi), worse than 94% of stainless steel grades
348H properties
Typical room-temperature values for 348H — 6 properties are specific to this condition; the rest are grade-level values shared by every 348 temper. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher.
Physical3
348H 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).
Mechanical16
348H has a yield strength of 245 MPa (35.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 94% of stainless steel grades. Elongation at break is 43% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
348H is rated for continuous service to 900°C (1,652 °F). It conducts heat at 16.3 W/m·K (9.42 BTU/hr·ft·°F), better than 68% of stainless steel grades. Thermal expansion is 16.6 µm/m·K (9.22 µin/in·°F).
Electrical3
348H conducts electricity at 2.4 % IACS, better than 67% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 53% of stainless steel grades.
Sustainability4
Producing a kilogram of 348H takes about 53 MJ of energy and emits 5.4 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 55%.
Manufacturability8
348H's machinability is fair (38/100, better than 63% of stainless steel grades); weldability excellent (85/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 348 tempers and conditions
348 is also supplied in 8 other conditions. The full side-by-side table is on the 348 overview.
- AnnealedDefaultStandard stocked condition for plate, pipe, tube and forgings; maximum ductility and corrosion resistance.250 MPa yield · 160 HB
- CDPick for straight, close-tolerance bar and fasteners needing higher yield strength and better machined finish than annealed.480 MPa yield · 210 HB
- 348HSpecify when ASME creep allowables above ~540 °C are needed; coarser grain size and higher carbon give better long-term rupture strength.245 MPa yield · 165 HB
Working with 348H
Is 348 easy to machine?
Work-hardens rapidly and NbC particles are abrasive — use rigid setups, positive-rake carbide, heavy constant feed, no dwelling, and flood coolant.
Can 348 be welded?
Readily welded by GTAW/GMAW/SMAW with ER/E347-type filler (order low-Ta, low-Co filler for nuclear work); no post-weld anneal normally needed, but stabilize-anneal heavy sections and avoid excessive heat input to limit hot cracking.
Can 348 be formed, bent or molded?
Excellent cold formability with high work-hardening rate; allow ~50 % more press force and more springback than carbon steel, and interstage anneal for severe draws.
What surface finishes work on 348?
Passivate per ASTM A967 or electropolish after fabrication; pickle/blast weld scale off to restore the passive film — not anodizable.
348 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 |
|---|---|---|
| C0.04–0.10 for 348H | ≤ 0.08 | 0.05 |
| Mn | ≤ 2 | 1.5 |
| Si1.00 max in some product specs | ≤ 0.75 | 0.5 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.03 | 0.01 |
| Cr | 17 – 19 | 18 |
| Ni | 9 – 13 | 11 |
| NbNb+Ta ≥ 10×C (≥ 8×C for 348H), 1.10 max total | ≤ 1.1 | 0.7 |
| Tarestricted for low neutron activation | ≤ 0.1 | 0.05 |
| Corestricted to limit Co-60 activation | ≤ 0.2 | 0.1 |
| Fe | balance | — |
348H — frequently asked
What is 348H used for?
348H is typically used for nuclear reactor internals, radiation-service piping and fittings, reactor vessel cladding and liners, steam and superheater tubing (348H), instrumentation tubing in reactor systems and pressure vessel shells and nozzles. In short: low-Ta, low-Co 347; nuclear reactor grade; stabilized for 870 °C service.
What is the yield strength of 348H?
348H has a typical yield strength of 245 MPa (35.5 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 94% of stainless steel grades. Strength varies by condition: see the 9 listed tempers.
Is 348H easy to machine?
Not especially — machinability is rated fair (38/100, better than 63% of stainless steel grades). Work-hardens rapidly and NbC particles are abrasive — use rigid setups, positive-rake carbide, heavy constant feed, no dwelling, and flood coolant.
Can 348H be welded?
Yes — weldability is rated excellent (85/100). Readily welded by GTAW/GMAW/SMAW with ER/E347-type filler (order low-Ta, low-Co filler for nuclear work); no post-weld anneal normally needed, but stabilize-anneal heavy sections and avoid excessive heat input to limit hot cracking.
What surface finishes work on 348H?
Passivate per ASTM A967 or electropolish after fabrication; pickle/blast weld scale off to restore the passive film — not anodizable.
Can 348H be formed, bent or molded?
Excellent cold formability with high work-hardening rate; allow ~50 % more press force and more springback than carbon steel, and interstage anneal for severe draws.
What is the maximum service temperature of 348H?
348H 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 348 Annealed and 348-FH?
Annealed is the default condition — standard stocked condition for plate, pipe, tube and forgings; maximum ductility and corrosion resistance. FH: maximum cold-worked strength strip/wire; essentially flat-only parts, blanking and springs. Yield strength is 250 MPa in Annealed versus 1,000 MPa in FH.
Sources
- ASTM A240/A240M — Chromium and Chromium-Nickel Stainless Steel Plate, Sheet and Strip — ASTM International (2023)
- ASTM A312/A312M — Seamless and Welded Austenitic Stainless Steel Pipe — ASTM International (2022)
- ASTM A479/A479M — Stainless Steel Bars and Shapes for Pressure Vessels — ASTM International (2023)
- SAE AMS 5512 / UNS S34800 designation data — SAE International (2019)
- ASM Specialty Handbook: Stainless Steels — ASM International (1994)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASME BPVC Section II Part D — allowable stresses for TP348/TP348H — ASME (2023)
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.