Stainless Steel
Stainless Steel 348
Properties, tempers, machining, finishes and uses — values shown for the Annealed condition.
348 (UNS S34800, ASTM A240 TP348) is a niobium-stabilized austenitic stainless steel similar to 347 but with restricted tantalum and cobalt content, developed for nuclear reactor service where neutron activation must be controlled.
Reference datasheet — 348 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.
What is 348?
348 (UNS S34800, ASTM A240 TP348) is a niobium-stabilized austenitic stainless steel similar to 347 but with restricted tantalum and cobalt content, developed for nuclear reactor service where neutron activation must be controlled. Annealed material gives 250 MPa yield, 620 MPa tensile, 45 % elongation and 160 HB (80 HRB), with service to 870 °C; conditions on file include annealed, stabilize-annealed, hot-rolled, cold-drawn, quarter- through full-hard, and the higher-carbon 348H for creep service. Formability is good (score 80) but the alloy work-hardens rapidly and NbC particles are abrasive. Specify 347 or 347LN where the Ta and Co limits are not required. 348 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). 348 has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 91% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
What is 348 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
- Pressure vessel shells and nozzles
- Welded structural supports in containment
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 — 870°C (1,598 °F), better than 82% of stainless steel grades
- Ductile — tolerates forming and impact — 45%, better than 76% of stainless steel grades
Limitations
- Low strength — 250 MPa (36.3 ksi), worse than 91% of stainless steel grades
348 properties
Typical room-temperature values for 348-Annealed (standard stocked condition for plate, pipe, tube and forgings; maximum ductility and corrosion resistance), compiled from standards, handbooks and producer data. Each bar shows where the value sits among the stainless steel grades in FabDigit's library — further right is higher. Other conditions have their own pages: see tempers.
Physical3
348 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
348 has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 91% of stainless steel grades. Elongation at break is 45% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
348 is rated for continuous service to 870°C (1,598 °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
348 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 348 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
348's machinability is fair (38/100, better than 63% of stainless steel grades); weldability excellent (85/100); formability very good (80/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
348 tempers and conditions
348 is supplied in 9 conditions, each with its own property set. Open one for its full datasheet. Annealed is what FabDigit quotes unless the drawing says otherwise.
- 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
7 further conditions are listed below with a summary only.
| Condition | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault solution annealed ~1040–1120 °C, rapid cooled | Standard stocked condition for plate, pipe, tube and forgings; maximum ductility and corrosion resistance. | 250 | 620 | 45 | 160 HB | — |
solution anneal followed by 870–900 °C / 2 h hold | Choose for heavy welded nuclear assemblies or service in the 425–815 °C sensitizing range to tie up carbon as NbC and prevent knife-line attack. | 255 | 615 | 43 | 165 HB | — |
hot worked and annealed bar and plate | Economical condition for large bar, forging stock and heavy plate where surface finish and tight tolerance are not critical. | 245 | 600 | 45 | 165 HB | — |
annealed then cold drawn bar/wire | Pick for straight, close-tolerance bar and fasteners needing higher yield strength and better machined finish than annealed. | 480 | 720 | 28 | 210 HB | — |
cold rolled strip/sheet to quarter-hard temper | Use where moderate strength increase is needed but some bending/forming is still required. | 570 | 900 | 14 | 26 HRC | — |
cold rolled to half-hard temper | For springy flat parts, clamps and shim stock where high yield strength matters more than formability. | 790 | 1,070 | 10 | 32 HRC | — |
cold rolled to three-quarter-hard temper | Niche strip temper for flat springs and straps with only gentle forming. | 950 | 1,200 | 6 | 35 HRC | — |
cold rolled to full-hard temper | Maximum cold-worked strength strip/wire; essentially flat-only parts, blanking and springs. | 1,000 | 1,300 | 4 | 38 HRC | — |
high-carbon (0.04–0.10 % C) version, solution annealed ≥1050 °C | Specify when ASME creep allowables above ~540 °C are needed; coarser grain size and higher carbon give better long-term rupture strength. | 245 | 620 | 43 | 165 HB | — |
Working with 348
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.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. 348 is highlighted; hover a dot for its name, or open the interactive family chart.
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 | — |
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.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing.
Passivation
- Pickling
Plating
- Electroless Nickel (EN)
- Gold Plating
- Hard Chrome Plating
- Silver Plating
Organic Coating
- Epoxy Coating
Thermal Spray
- Plasma Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel 348 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S34800
- ASTM
- A240 TP348
- Also called
- TP348
How much does 348 cost?
348 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.
348 — frequently asked
What is 348 used for?
348 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 348?
348 has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 91% of stainless steel grades. Strength varies by condition: see the 9 listed tempers.
Is 348 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 348 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 348?
Passivate per ASTM A967 or electropolish after fabrication; pickle/blast weld scale off to restore the passive film — not anodizable.
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 is the maximum service temperature of 348?
348 is rated for continuous use to about 870°C (1,598 °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.
How much does 348 cost?
348 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
- 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; 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.