What Is 1.4460 Stainless Steel? Duplex Grade Properties and Uses

What Is 1.4460 Stainless Steel?

1.4460 is a ferritic-austenitic duplex stainless steel standardized in the European EN 10088 series under the steel name X3CrNiMoN27-5-2. It belongs to the early generation of duplex grades developed from the classic AISI 329 alloy, and it is the forerunner of modern duplex steels such as 2205. The duplex structure, a roughly balanced mixture of ferrite and austenite, combines the high strength of ferrite with the toughness and corrosion resistance of austenite.

Because of its high chromium and molybdenum content with a nitrogen addition, 1.4460 offers roughly double the yield strength of standard 304 or 316 austenitic grades, good resistance to chloride stress corrosion cracking, and moderate pitting resistance. It is magnetic because of its ferrite phase. While modern duplex grades have superseded it in many applications, 1.4460 remains in service in chemical processing, heat exchangers, pulp and paper equipment and general engineering.

Equivalent Grades

Standard System	Designation
EN (Europe)	1.4460 / X3CrNiMoN27-5-2
ASTM / AISI (USA)	329 / UNS S32900
JIS (Japan)	SUS329J1
GB (China)	022Cr25Ni6Mo2N

Chemical Composition (EN 10088-2)

Element	C	Si	Mn	P	S	N	Cr	Mo	Ni
Content, %	0.05 max	1.00 max	2.00 max	0.030 max	0.015 max	0.05-0.20	25.0-28.0	1.30-2.00	4.50-6.50

The nitrogen addition is essential: it promotes austenite formation, raises the pitting resistance equivalent number (PREN), and increases strength. The classic AISI 329 composition of the same family is specified with slightly wider chromium and nickel ranges and a higher carbon limit, reflecting older production practice.

Mechanical Properties

Property	Typical Minimum Value
0.2% proof stress Rp0.2	450 MPa
Tensile strength Rm	620-850 MPa
Elongation A	20%
Hardness	300 HB max

With a yield strength around 450 MPa, 1.4460 permits substantially thinner sections than austenitic grades in load-bearing design, which is one of the historical attractions of the duplex family.

Key Characteristics

High strength: about double the yield strength of 304/316 austenitic stainless steel.

Good stress corrosion cracking resistance in chloride environments, where austenitic 304/316 can fail.

Moderate pitting and crevice corrosion resistance, with a PREN typically in the range of 32-34, better than 304/316 but lower than modern duplex 2205.

Magnetic behavior due to the ferrite phase.

Weldable with care; controlled heat input and filler selection are required to preserve the balanced two-phase structure.

Welding Considerations

Welding of 1.4460 requires tighter control than modern duplex grades. Excessive heat input or slow cooling can produce a weld metal and heat-affected zone with too much ferrite, which reduces toughness and corrosion resistance. Matching or over-alloyed filler metals are recommended, heat input should be limited, and post-weld annealing may be necessary to restore the ferrite-austenite balance and corrosion resistance in critical service. The grade is noticeably less forgiving to weld than 2205.

Comparison with Modern Duplex 2205 (1.4462)

Grade 2205 (1.4462, UNS S32205) is the modern workhorse duplex grade. It carries higher nickel and molybdenum plus a controlled nitrogen addition, giving it a better ferrite-austenite balance, higher PREN (about 34-36), superior toughness and improved weldability compared with 1.4460. In most new designs, 2205 has replaced 1.4460 for chemical, marine and oil and gas service. 1.4460 remains relevant mainly for repair, replacement and lower-cost applications where its specific combination of strength and moderate corrosion resistance is adequate.

Typical Applications

Chemical processing tanks, heat exchangers and piping for moderately corrosive media.

Pulp and paper equipment exposed to chloride-containing liquors.

General engineering components requiring higher strength than austenitic steel.

Early-generation oil and gas components for sour service and offshore duty.

Pump shafts, valve components and agitator shafts in process plants.

Frequently Asked Questions

Q1. Is 1.4460 magnetic?

Yes. The ferritic phase in the duplex microstructure is magnetic, so 1.4460 responds to magnets. This is normal for all duplex stainless steels and does not indicate a defect.

Q2. What is the difference between 1.4460 and 2205 (1.4462)?

1.4460 is an early-generation duplex with lower nickel, molybdenum and nitrogen. It has lower toughness, lower pitting resistance (PREN about 32-34 versus 34-36 for 2205) and is less forgiving to weld. 2205 offers a better balanced microstructure and has largely replaced 1.4460 in new designs.

Q3. Can 1.4460 be welded?

Yes, but with care. Heat input must be controlled, matching or over-alloyed filler should be used, and post-weld annealing may be required to restore corrosion resistance. It is less tolerant of poor welding practice than modern duplex grades.

Q4. What does duplex mean in stainless steel?

Duplex describes a two-phase microstructure of approximately equal parts ferrite and austenite. This structure combines the high strength and stress corrosion cracking resistance of ferrite with the toughness of austenite.

Q5. Why was 1.4460 largely replaced by 2205?

Modern duplex 2205 has higher alloy content, better corrosion resistance, higher toughness and much better weldability. These advantages make 2205 more reliable and cost-effective for most chloride and chemical service, so 1.4460 is now a niche grade.

Q6. What is PREN and what is it for 1.4460?

PREN, the pitting resistance equivalent number, is calculated as Cr + 3.3 Mo + 16 N and ranks pitting resistance in chloride media. For 1.4460 the value is typically 32-34, well above 304/316 but below modern duplex grades such as 2205.