Grade dossier
434 Stainless Steel
434 stainless steel is a molybdenum-bearing ferritic grade identified as UNS S43400. With 16–18% chromium and 0.75–1.25% molybdenum, it improves corrosion resistance over 430 in deicing-salt and similar mild chloride exposure, making it especially relevant to bright automotive trim, decorative molding and formed flat-product applications.
Identity before substitution
Specify 434 by product standard, flat-product condition and finish
Type 434 is a molybdenum-bearing modification of Type 430 rather than a stabilized welding grade. Cleveland-Cliffs specifically ties its molybdenum addition to better resistance against deicing chemicals, while Swiss Steel cross-references AISI 434 to EN 1.4113 / X6CrMo17-1. The RFQ should state the governing standard, thickness, width, finish, forming route, welding requirement and service exposure rather than relying on the grade number alone.
434 stainless composition
UNS S43400 chemistry used for Type 434 automotive trim
Use the purchase specification as the acceptance basis
The values at right reproduce Cleveland-Cliffs’ Type 434 / UNS S43400 automotive-trim chemistry. Swiss Steel cross-references 434 to EN 1.4113 / X6CrMo17-1, but its listed carbon and molybdenum limits differ from this UNS trim chemistry. Put the exact standard and edition on the purchase order and verify the delivered heat against its MTC.
| C | 0.12 max |
|---|---|
| Mn | 1.00 max |
| P | 0.040 max |
| S | 0.030 max |
| Si | 1.00 max |
| Cr | 16.00–18.00 |
| Mo | 0.75–1.25 |
434 stainless properties
Use source-specific trim values and keep acceptance tied to the order standard
Cleveland-Cliffs bright automotive-trim typical values
| Tensile strength | 552 MPa typical |
|---|---|
| 0.2% yield strength | 345 MPa typical |
| Elongation in 50.8 mm | 28% typical |
| Rockwell hardness | 75 HRB typical |
Physical and condition indicators
| Density | about 7.72 g/cm³ |
|---|---|
| Elastic modulus | about 200 GPa |
| Mean CTE · 0–100°C | about 10.1 µm/m·K |
| Heat-treatment response | Ferritic; not selected for quench hardening |
These mechanical values are Cleveland-Cliffs manufacturer-typical data for Type 434 automotive-trim product, not universal minima for every 434 order. Thickness, cold work, anneal route, orientation and product specification affect delivered properties; use the ordered standard and heat-specific MTC for acceptance.
Selection boundary
Use 434 where molybdenum and bright-trim corrosion resistance solve the real problem
434 is strongest when the requirement combines ferritic economics, improved resistance to deicing salts versus 430, and bright decorative flat-product performance. It should not be treated as a universal substitute for 304/316, a fully stabilized welding grade, or a higher-molybdenum ferritic grade in aggressive chloride exposure.
Good reasons to evaluate 434
Above-belt-line automotive trim such as window bezels and roof trim exposed to deicing salts
Bright-annealed decorative trim needing more corrosion resistance than basic 430
Roll-formed or stamped ferritic trim where a molybdenum-bearing 17% Cr grade is preferred over basic 430
Decorative moldings, wheel covers and similar trim where bright finish and road-salt corrosion resistance are both important
Stop and review before release
Severe chloride, continuously wet salt deposits or crevice conditions without corrosion testing
Service that really needs the higher molybdenum level and pitting margin of a grade such as 444
Automatic substitution between UNS S43400 and EN 1.4113 without reconciling carbon and molybdenum limits
Welded service where post-weld annealing is impractical and a fully stabilized ferritic grade such as 436 is the better route
Fabrication route
Control forming, welding and bright-finish handling together
Cleveland-Cliffs describes the ferritic trim grades as readily drawn and formed, with drawing behavior similar to low-carbon steel but requiring stronger tooling and more power in the annealed condition.
Type 434 has a slightly greater tendency to rope during forming than Type 430. For appearance-critical trim, qualify the formed part rather than accepting incoming strip luster alone.
434 is weldable by common fusion and resistance techniques but Cleveland-Cliffs notes poorer weldability than Type 409 because of higher carbon and the lack of stabilizing elements. Post-weld annealing is required to restore optimum corrosion and forming characteristics.
Bright Anneal #2 is a typical automotive-trim finish. Interleaving is recommended to prevent marring, and forming can reduce luster, so appearance acceptance should be defined after the manufacturing route is known.
434 stainless supplier evidence
Buy the actual flat-product range, finish and specification—not just the grade name
Cleveland-Cliffs publishes a concrete automotive-trim production range covering Type 434 and currently lists 434 among its ferritic stainless products. Use those dimensions as attributable mill-source evidence, not as a claim that every 434 stainless supplier stocks the same sizes. Their trim bulletin also marks Type 434 “inquire for availability,” so confirm current production, finish and lead time before quotation.
Published trim thickness: 0.010–0.040 in · 0.25–1.02 mm
Published trim width: up to 36 in · 914 mm
Heavier gauges: available for non-critical finishes only
Typical finish: Bright Anneal #2 · paper or PVC interleaving available
MTC and purchase-order checkpoint
Match the heat number to UNS S43400 or the ordered EN 1.4113 chemistry; verify C, Cr and Mo, tensile/yield/elongation/hardness results where required, thickness, width, finish, edge condition, governing standard and edition. Do not accept a generic “434” certificate if the chemistry, condition or product specification is unclear.
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Interactive selection check
Test 434 against the controlling procurement question
Procurement FAQ
Questions to close before ordering 434 stainless steel
What is 434 stainless steel?
434 is a molybdenum-bearing ferritic stainless steel identified as UNS S43400. Cleveland-Cliffs describes it as a modification of Type 430 whose molybdenum addition improves corrosion resistance and resistance to many deicing chemicals, with a strong procurement case in bright automotive trim.
What is the EN equivalent of 434 stainless steel?
Swiss Steel cross-references AISI 434 to EN 1.4113 / X6CrMo17-1. Because published carbon and molybdenum limits can differ between specifications, state the exact product standard and edition rather than treating the designations as automatically interchangeable.
Can 434 stainless steel be hardened by heat treatment?
434 is normally purchased as a non-hardenable ferritic stainless steel, not as a quench-hardening martensitic grade. Processing history and heating above the critical transformation range can affect microstructure, so condition and fabrication route still matter.
What are two important 434 application constraints?
First, improved resistance to deicing salts does not make 434 a seawater or severe-crevice-corrosion grade. Second, 434 has a slightly greater roping tendency than 430 and its lack of stabilizing additions makes welded fabrication less forgiving unless the required post-weld treatment is practical.
What should a 434 RFQ include?
State UNS S43400 or EN 1.4113 as applicable, governing standard and edition, thickness, width, finish, edge/interleaving requirement, forming and welding operations, corrosion environment, mechanical acceptance requirements, MTC requirement and any finished-part appearance criteria.
Sources, scope and RFQ
Trace the 434 chemistry, trim range and welding limits before release
UNS S43400 identity, 16–18% Cr and 0.75–1.25% Mo chemistry, 552 MPa typical tensile strength, 345 MPa typical yield strength, 28% elongation, 75 HRB, 0.25–1.02 mm trim thickness, widths to 914 mm, Bright Anneal #2 finish, deicing-salt positioning, roping and weldability guidance.
Lists Type 434 as UNS S43400 / EN 1.4113 / SUS 434, with typical 16.5% Cr, about 1.0% Mo, improved corrosion resistance over Type 430 and automotive trim as the representative application.
Maps AISI 434 to EN 1.4113 / X6CrMo17-1 and shows a chemistry family centered on 16–18% Cr with molybdenum. Because the listed limits differ from the UNS trim table, substitution requires the exact order specification and MTC.
Use the current ASTM/ASME, EN or customer specification for the ordered form. Release should be based on the heat-specific MTC, C/Cr/Mo chemistry, dimensions, surface finish, mechanical results where required and agreed inspection—not a generic web table.