Grade dossier
446 Stainless Steel
446 stainless steel is a high-chromium ferritic heat-resistant grade identified as UNS S44600. Its strongest procurement case is furnace, kiln, combustion, recuperator and other hot-corrosion hardware where oxidation and sulfidation resistance matter more than high elevated-temperature strength.
Identity before substitution
Specify 446 by UNS identity, product standard and high-temperature duty
Type 446 is not simply “a higher-chromium 430.” ASTM chemistry for UNS S44600 permits 23–27% chromium and up to 0.25% nitrogen, while its procurement value is tied to high-temperature oxidation and sulfidation resistance. Worldstainless maps S44600 to EN 1.4749 / X15CrN26; because the commercial market also labels EN 1.4762 as “446,” the purchase order should state the exact designation, product standard, chemistry, form and service temperature.
446 stainless composition
ASTM chemistry limits for UNS S44600 / Type 446
Do not confuse Type 446 with the newer S4462x / S4466x superferritic grades
The limits below follow ASTM A240/A276 chemistry for S44600. Product form still controls the applicable specification and testing. A heat certificate should explicitly identify S44600 and the ordered standard rather than relying on the commercial “446” name alone.
| C | 0.20 max |
|---|---|
| Mn | 1.50 max |
| P | 0.040 max |
| S | 0.030 max |
| Si | 1.00 max |
| Cr | 23.00–27.00 |
| Ni | 0.75 max |
| N | 0.25 max |
446 stainless properties
Separate ordered minimums from typical annealed-sheet behavior
Published flat-product minimums for S44600
| Tensile strength | 515 MPa min |
|---|---|
| 0.2% yield strength | 275 MPa min |
| Elongation | 20% min |
| Rockwell hardness | 96 HRB max |
Nickel Institute typical annealed sheet
| Tensile strength | about 552 MPa · 80 ksi |
|---|---|
| 0.2% yield strength | about 345 MPa · 50 ksi |
| Elongation in 2 in | about 20% |
| Rockwell hardness | about 83 HRB |
Mechanical values are product- and specification-dependent. Published references for S44600 do not all use the same acceptance table; wire/bar and flat products can differ. Use the exact ASTM/ASME standard, section size, annealed condition and heat-specific MTC for acceptance rather than treating one web table as universal.
Selection boundary
Choose 446 for hot-corrosion resistance, not for high creep strength or easy fabrication
The high chromium level gives 446 strong oxidation and sulfidation resistance, but the same ferritic high-chromium structure brings embrittlement and forming limits. Review temperature profile, mechanical load, thermal cycling, sulfur activity, section thickness and fabrication route together.
Good reasons to evaluate 446
Furnace and kiln linings, burner parts, combustion chambers and stack dampers exposed to high-temperature oxidizing service
Recuperators, boiler baffles, soot blowers and other thermal-processing components where sulfidation resistance is valuable
Spouts or hardware handling molten copper or brass where published 446 service experience is relevant
Components where oxidation resistance through roughly 2000°F / 1093°C is more important than high load-bearing strength
Stop and review before release
High sustained mechanical load or creep-critical design—the alloy’s elevated-temperature strength is comparatively low
Service dwelling around 700–1000°F / 371–538°C without accepting severe 475°C-type embrittlement and room-temperature ductility loss
Long exposure around 1000–1300°F / 538–704°C without reviewing sigma-phase embrittlement
Automatic substitution with EN 1.4762 or superferritic S44627/S44660 without reconciling chemistry, mechanical requirements and certification
Fabrication route
Control forming temperature, welding heat and embrittlement exposure
446 has a relatively high ductile-to-brittle transition temperature. Rolled Alloys recommends edge preparation, low forming speeds and preheating around 250–400°F / 121–204°C to improve bending and forming reliability.
When annealing is required, a published route is about 1550–1650°F / 843–899°C followed by rapid cooling. Avoid unnecessary soaking or slow cooling through embrittling temperature ranges.
Conventional welding methods can be used, but preheat/postheat around 300–600°F / 149–316°C may help. Austenitic fillers such as E310 or E312 are commonly suggested where weld-deposit ductility is the priority.
Do not specify quench hardening: 446 is ferritic and non-hardenable by conventional heat treatment. Joint design, section thickness and the service thermal cycle dominate fabrication risk.
446 stainless supplier evidence
Verify the real mill route, product form and live size before quotation
Current supply evidence is form-specific. Universal Stainless lists 446 made by AOD to ASTM A276 and sells round bar, flat bar and ingot, while Rolled Alloys lists 446 flat bar and round bar with location-based stock lookup. Use these as attributable supply references—not as a claim that every 446 stainless supplier carries the same sizes.
Universal Stainless: round bar, flat bar and ingot · AOD melt route
Rolled Alloys: flat bar and round bar · stock lookup by selected size/location
ASTM product routes commonly include A240 flat products, A268 tube and A276 bar/shapes
Size range is supplier- and specification-specific; verify live diameter/thickness/width/length before RFQ release
MTC and purchase-order checkpoint
Require the heat number, UNS S44600 identity, governing standard and edition, C/Mn/Si/Cr/Ni/N chemistry, ordered dimensions and tolerances, annealed condition, mechanical results applicable to the product form, finish and supplementary inspection. For high-temperature service, also state peak/continuous temperature, atmosphere, sulfur activity, thermal cycling and mechanical load.
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Interactive selection check
Test 446 against the controlling procurement question
Procurement FAQ
Questions to close before ordering 446 stainless steel
What is 446 stainless steel?
446 is a high-chromium ferritic heat-resistant stainless steel identified as UNS S44600. ASTM chemistry permits 23–27% chromium, and the grade is used where oxidation, sulfidation and other hot-corrosion mechanisms control material selection.
What is the EN equivalent of 446 stainless steel?
Worldstainless maps S44600 to EN 1.4749 / X15CrN26. The commercial market also frequently labels EN 1.4762 / X10CrAlSi25 as “446,” so treat the EN number as an ordered requirement and verify the heat chemistry rather than assuming automatic equivalence.
Can 446 stainless steel be hardened by heat treatment?
No conventional martensitic quench-hardening route is used. 446 remains ferritic. When annealing is needed, a published route is roughly 843–899°C followed by rapid cooling.
What are two important 446 application constraints?
First, elevated-temperature strength is relatively low, so creep- or load-critical hardware needs a separate strength review. Second, the alloy can embrittle severely around 371–538°C, with sigma-phase embrittlement also possible after long exposure around 538–704°C.
What should a 446 RFQ include?
State UNS S44600, governing ASTM/ASME standard and edition, product form, dimensions and tolerances, annealed condition, finish, quantity, heat-treatment/fabrication route, peak and continuous service temperature, atmosphere, mechanical load, MTC requirements and any supplementary inspection.
Sources, scope and RFQ
Trace the S44600 chemistry, thermal limits and actual supply route before release
S44600 chemistry basis: C 0.20 max, Mn 1.50 max, Si 1.00 max, Cr 23–27, Ni 0.75 max and N 0.25 max. Jindal also publishes flat-product minimum mechanical values for its S44600 grade listing.
UNS S44600 identity, nominal 25% chromium basis, common ASTM product routes and typical annealed-sheet indicators around 50 ksi yield, 80 ksi tensile, 20% elongation and 83 HRB.
Oxidation resistance through about 2000°F, sulfidation resistance, low elevated-temperature strength, 700–1000°F embrittlement, sigma-phase warning, forming/welding guidance, flat-bar and round-bar availability and location-based stock lookup.
Current mill-source evidence for AOD-melted 446, ASTM A276 production and sold forms including round bar, flat bar and ingot. Published size ranges are order/specification dependent and must be confirmed at RFQ stage.
Maps UNS S44600 to EN 1.4749 / X15CrN26. Because other commercial sources also label 1.4762 as 446, final substitution should be controlled by the purchase standard and heat-specific MTC.