Grade dossier
441 Stainless Steel
441 stainless steel is a dual-stabilized ferritic grade identified by ATI as UNS S44100, typically with about 18% chromium plus titanium and niobium/columbium stabilization. Its strongest procurement case is formed and welded high-temperature hardware—especially automotive exhaust components—where improved creep strength, oxidation resistance and weld-zone stability are required without moving to an austenitic grade.
Identity before substitution
Specify 441 by UNS identity, stabilization route and product form
Type 441 should be purchased by a controlled designation rather than by a loose “18% Cr ferritic” description. ATI identifies the alloy as UNS S44100 in ASTM A240 and A554 and uses both titanium and columbium/niobium stabilization. Aperam markets 441 as EN 1.4509 / X2CrTiNb18, while other producer mappings for 1.4509 may use a different UNS number. Put the exact standard, UNS/EN requirement, stabilization chemistry, product form, dimensions, finish and service condition on the purchase order.
441 stainless composition
ASTM A240 chemistry limits for UNS S44100 / Type 441
Use the ordered standard, not a generic alloy label
ATI lists the following UNS S44100 chemistry limits for ASTM A240 sheet/strip. The grade is dual stabilized with titanium and columbium/niobium. EN 1.4509 / X2CrTiNb18 is widely used as a commercial cross-reference, but producer designation tables do not map it to one UNS number consistently; verify the ordered chemistry and the heat-specific MTC rather than approving substitution by name alone.
| C | 0.03 max |
|---|---|
| Mn | 1.00 max |
| P | 0.040 max |
| S | 0.030 max |
| Si | 1.00 max |
| Cr | 17.5–19.5 |
| Ni | 1.00 max |
| Ti | 0.10–0.50 |
| Nb / Cb | 0.3 + (9 × C) min · 0.90 max |
| N | 0.030 max |
441 stainless properties
Separate ASTM product minimums from manufacturer-typical annealed values
ATI 441 HP sheet/strip published minimums
| Tensile strength | 414 MPa min |
|---|---|
| 0.2% yield strength | 241 MPa min |
| Elongation | 20% min |
| Rockwell hardness | 90 HRB max |
ATI 441 HP typical annealed indicators
| Tensile strength | about 496 MPa |
|---|---|
| 0.2% yield strength | about 310 MPa |
| Elongation in 2 in | about 31% |
| Rockwell hardness | about 82 HRB |
The first panel reflects ATI’s current published minimums for 441 HP sheet/strip; the second is manufacturer-typical annealed data from the ATI technical sheet. ATI also reports that at about 704°C and above, 441 HP retains substantially more short-time strength than 409 HP. Those elevated-temperature values are comparative design inputs, not purchase guarantees. Acceptance should follow the ordered standard and heat-specific MTC.
Selection boundary
Use 441 when high-temperature strength, dual stabilization and ferritic thermal behavior solve the requirement
441 is strongest where exhaust-system forming, weld-zone stability, low thermal expansion and better high-temperature strength than 409 are controlling requirements. It is not a universal substitute for 304/316 in general corrosion service, and it should not be promoted as a fixed 950–1000°C service grade without checking atmosphere, thermal cycling, loading, thickness and oxidation criteria.
Good reasons to evaluate 441
Automotive exhaust manifolds and hot-side exhaust components requiring more elevated-temperature strength and oxidation margin than 409
Formed exhaust tubing and welded structures that benefit from low ferritic thermal expansion and dual stabilization
Heat exchangers, boiler components and fume-handling parts in reviewed oxidizing environments
Kitchen, appliance and architectural components where 17–19% Cr corrosion resistance, formability and surface finishing are suitable
Stop and review before release
Severe pitting, crevice or chemical service where a molybdenum-bearing ferritic or austenitic grade may be required
Using a laboratory oxidation projection as a guaranteed service-temperature limit; ATI projects roughly 899–1010°C in still-air tests, but real limits depend on cycling and atmosphere
Load-bearing high-temperature parts without checking creep/stress-rupture data, section thickness, life target and thermal cycling
Automatic substitution between UNS S44100 and EN 1.4509 products without reconciling chemistry, producer mapping, standard and certification
Fabrication route
Control exhaust forming, welding and thermal exposure together
ATI 441 HP was developed for severe tube bending and forming typical of automotive exhaust-manifold fabrication. Confirm bend radius, wall thinning, tooling, weld seam orientation and surface condition on the actual ordered gauge.
Dual stabilization with titanium and columbium/niobium is intended to support weld ductility and intergranular-corrosion resistance in the heat-affected zone. Qualify the actual welding process, heat input, filler selection and post-weld cleaning for the component.
441 remains ferritic and has lower thermal expansion than austenitic stainless steels, which can reduce thermal mismatch in cyclic hot service. Distortion, restraint, section changes and dissimilar-metal joints still need engineering review.
ATI’s high-temperature data show improved short-time and creep-rupture strength from columbium/niobium strengthening. Do not convert laboratory oxidation or stress-rupture data into a service limit without defining atmosphere, peak temperature, cycle count and design life.
441 stainless supplier evidence
Buy the actual 441 sheet, coil or tube route—not just the grade name
ATI currently lists 441 HP as UNS S44100 sheet and strip to ASTM A240. Aperam South America publishes dimensional evidence for its 441 / 1.4509 offer covering coils, sheets and tubes. Treat those values as attributable mill-source evidence, not as a claim that every 441 stainless supplier stocks the same sizes. Confirm the exact producer, standard, stabilization route, finish and lead time before quotation.
Aperam 441 coil/sheet thickness: 0.40–5.20 mm
Aperam 441 coil/sheet width: 1000–1250 mm
Aperam 441 tube evidence: 31.75–127 mm diameter · 1–3 mm wall
ATI current form evidence: sheet and strip · ASTM A240; ATI technical sheet also identifies ASTM A554 tubing
MTC and purchase-order checkpoint
Match the heat number to the explicitly ordered designation. For UNS S44100 verify C, Cr, Ni, N, Ti and Nb/Cb stabilization plus required mechanical results, dimensions, condition, finish, standard and edition. If the order references EN 1.4509, confirm the producer chemistry and cross-reference rather than assuming every 1.4509 certificate is automatically S44100.
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Interactive selection check
Test 441 against the controlling procurement question
Procurement FAQ
Questions to close before ordering 441 stainless steel
What is 441 stainless steel?
441 is a heat-resistant ferritic stainless steel. ATI identifies its 441 HP alloy as UNS S44100 with about 18% chromium and dual titanium plus niobium/columbium stabilization, developed for weld ductility, intergranular-corrosion resistance and improved elevated-temperature strength in applications such as automotive exhaust systems.
What is the EN equivalent of 441 stainless steel?
EN 1.4509 / X2CrTiNb18 is a common commercial cross-reference for 441. However, producer mappings are not fully uniform: ATI identifies 441 as UNS S44100, while some 1.4509 product families use other UNS designations. Verify chemistry and the governing product standard before substitution.
Can 441 stainless steel be hardened by heat treatment?
441 is ferritic and is not purchased as a conventional quench-hardened martensitic grade. Strength depends on composition, annealing, thickness, cold work and service temperature; ATI attributes its improved high-temperature strength to niobium/columbium-related strengthening.
What are two important 441 application constraints?
First, published oxidation-temperature projections are laboratory screening data rather than guaranteed service limits; atmosphere, cycling, stress and section thickness matter. Second, 441 is an 18% Cr ferritic corrosion-resistant grade, not a universal replacement for molybdenum-bearing stainless steels in severe pitting or crevice-corrosion service.
What should a 441 RFQ include?
State UNS S44100 or the explicitly required EN designation, product standard and edition, stabilization requirement, sheet/strip/tube form, dimensions, finish, forming and welding route, peak and cyclic service temperature, environment, MTC requirements and any supplementary inspection.
Sources, scope and RFQ
Trace the 441 chemistry, high-temperature basis and actual supply route before release
UNS S44100 identity, ASTM A240/A554 references, dual Ti + Nb/Cb stabilization, typical annealed properties, elevated-temperature tensile and stress-rupture behavior, corrosion data and still-air oxidation projections.
Current manufacturer listing for UNS S44100 sheet and strip with ASTM A240 basis, current chemistry limits, density and published minimum tensile, yield, elongation and hardness requirements.
Current mill-source evidence for titanium-niobium-stabilized ferritic 441 / EN 1.4509, including coil/sheet dimensions of 0.40–5.20 mm × 1000–1250 mm and tube evidence of 31.75–127 mm diameter with 1–3 mm wall.
Current producer evidence for the 1.4509 family as stabilized ferritic stainless steel for exhaust systems, indoor cladding, restaurant equipment, tubes and heat exchangers. Its different UNS mapping is a practical reason to verify chemistry before approving EN/UNS substitution.