Stainless Steel 1.4378 +AT (Solution annealed)
Heat-treated state · default condition
EN 1.4378
Standard stock condition: maximum ductility, non-magnetic, best corrosion resistance — pick for forming, deep drawing and welded fabrication.
Values for the +AT condition
Other 1.4378 tempers and conditions
1.4378 is listed in 5 conditions; see the grade overview at 1.4378.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ATDefaultThis page Solution annealed | Standard stock condition: maximum ductility, non-magnetic, best corrosion resistance — pick for forming, deep drawing and welded fabrication. | 430 | 780 | 50 | 200 HB | — |
Cold worked to Rm ≥ 700 MPa | Lightly cold-drawn bar/wire: modest strength gain while keeping good ductility for cold heading and bending. | 480 | 760 | 25 | 225 HB | — |
Cold worked to Rm ≥ 800 MPa | Standard cold-drawn bar strength class for shafts, pins and property-class fasteners needing higher yield than annealed. | 600 | 860 | 18 | 24 HRC | — |
Cold worked to Rm ≥ 900 MPa | Higher-strength drawn bar/wire for loaded fasteners and spring-like parts where 304 cold-worked strength is not enough. | 720 | 960 | 14 | 28 HRC | — |
Cold worked to Rm ≥ 1000 MPa | Heavily drawn condition for maximum strength in small-section bar, wire and springs; ductility and cold-forming capacity are largely used up. | 830 | 1,060 | 11 | 32 HRC | — |
What is 1.4378 +AT?
1.4378 +AT is 1.4378 heat treated to +AT — standard stock condition: maximum ductility, non-magnetic, best corrosion resistance — pick for forming, deep drawing and welded fabrication. 1.4378 +AT has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 67% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 197 GPa (28.6 Msi). 1.4378 +AT has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Advantages
- Ductile — tolerates forming and impact — 50%, better than 90% of stainless steel grades
- Low embodied carbon — 3.7 kg CO₂/kg, better than 78% of stainless steel grades
1.4378 +AT properties
Typical room-temperature values for 1.4378 +AT; 17 are specific to this condition. Other listed values are 1.4378 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
1.4378 +AT has a density of 7.8 g/cm³ (0.282 lb/in³), heavier than 50% of stainless steel grades. It melts at 1,380°C (2,516 °F).
Mechanical15
1.4378 +AT has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 67% of stainless steel grades. Elongation at break is 50% and the elastic modulus is 197 GPa (28.6 Msi).
Thermal6
1.4378 +AT is rated for continuous service to 800°C (1,472 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), worse than 80% of stainless steel grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
1.4378 +AT conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 58% of stainless steel grades.
Sustainability4
Producing a kilogram of 1.4378 +AT takes about 46 MJ of energy and emits 3.7 kg of CO₂ — less than 88% of stainless steel grades. Typical recycled content is 55%.
Manufacturability7
1.4378 +AT's machinability is poor (33/100, worse than 57% of stainless steel grades); weldability very good (75/100); formability good (65/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1.4378 +AT
Is 1.4378 easy to machine?
Machines like a tough 304 but work-hardens faster — use rigid setups, sharp positive-rake carbide, heavy constant feed, low-to-moderate speed and flood coolant; avoid dwelling or rubbing.
Can 1.4378 be welded?
Readily welded by GTAW/GMAW/SMAW without preheat; use 307/308L-type or over-alloyed Cr-Ni-Mn filler, keep heat input and interpass temperature low, and no post-weld stress relief in the 550–800 °C sensitisation range.
Can 1.4378 be formed, bent or molded?
Excellent cold formability in +AT but very high work-hardening rate: expect 20–40 % higher press loads and more springback than 304, use interstage annealing for severe draws.
What surface finishes work on 1.4378?
Not anodizable — passivate per ASTM A967, electropolish or mechanically polish; takes bright architectural and PVD finishes well, but a slightly higher sulphur/manganese level can leave more fine inclusion pitting on mirror polish.
1.4378 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 |
|---|---|---|
| C≤0.08 % (X6 designation) | ≤ 0.08 | 0.06 |
| Si | ≤ 1 | 0.5 |
| Mnaustenite stabiliser replacing Ni | 11.5 – 14.5 | 13 |
| P | ≤ 0.05 | — |
| S | ≤ 0.03 | — |
| Cr | 17 – 19 | 18 |
| Ni | 2.5 – 4.5 | 3.2 |
| Nsolid-solution strengthening + austenite stability | 0.2 – 0.4 | 0.3 |
| Fe | balance | — |
1.4378 +AT — frequently asked
What is 1.4378 +AT used for?
1.4378 +AT is typically used for structural components, fasteners, transportation equipment and industrial fixtures. In short: nickel-lean 304 replacement; nitrogen-strengthened, 430 MPa yield; best corrosion of the 2xx set.
What is the yield strength of 1.4378 +AT?
1.4378 +AT has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 67% of stainless steel grades. Strength varies by condition: see the 5 listed tempers.
Is 1.4378 +AT easy to machine?
Not especially — machinability is rated poor (33/100, worse than 57% of stainless steel grades). Machines like a tough 304 but work-hardens faster — use rigid setups, sharp positive-rake carbide, heavy constant feed, low-to-moderate speed and flood coolant; avoid dwelling or rubbing.
Can 1.4378 +AT be welded?
Yes — weldability is rated very good (75/100). Readily welded by GTAW/GMAW/SMAW without preheat; use 307/308L-type or over-alloyed Cr-Ni-Mn filler, keep heat input and interpass temperature low, and no post-weld stress relief in the 550–800 °C sensitisation range.
What surface finishes work on 1.4378 +AT?
Not anodizable — passivate per ASTM A967, electropolish or mechanically polish; takes bright architectural and PVD finishes well, but a slightly higher sulphur/manganese level can leave more fine inclusion pitting on mirror polish.
Can 1.4378 +AT be formed, bent or molded?
Excellent cold formability in +AT but very high work-hardening rate: expect 20–40 % higher press loads and more springback than 304, use interstage annealing for severe draws.
What is the maximum service temperature of 1.4378 +AT?
1.4378 +AT 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.
Sources
- EN 10088-1/-2/-3 Stainless steels — grades, sheet/strip and bar — CEN (2014)
- ASTM A240 / A276 (UNS S24000, 18Cr-13Mn-3Ni-N) — ASTM International (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- Nitrogen-strengthened Cr-Mn austenitic stainless (S24000/Nitronic 33-type) datasheet — Stainless producer (2020)
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.