Duplex Stainless Steel 2304

Alloy 2304 (UNS S32304) is a duplex stainless steel with a composition that includes 23% chromium, 4% nickel, and is molybdenum-free. Here are some key points about Alloy 2304:

Corrosion Resistance:

Alloy 2304 exhibits corrosion resistance properties similar to those of 316L austenitic stainless steel.

It provides good resistance to a wide range of corrosive environments, including chloride-containing solutions.

Mechanical Properties:

Compared to austenitic grades such as 304L and 316L, Alloy 2304 offers higher mechanical strength, including yield strength.

The increased strength allows for weight savings in applications, particularly in properly designed pressure vessel applications.

Duplex Microstructure:

Alloy 2304 has a duplex microstructure consisting of a balanced mix of ferrite and austenite phases.

This microstructure contributes to the alloy's combination of corrosion resistance and mechanical properties.Alloy 2304 is commonly used in various industries, including chemical processing, oil and gas, and marine environments. It finds applications in equipment such as pressure vessels, heat exchangers, piping systems, and structural components.

General Properties

Alloy 2304 is a 23% chromium, 4% nickel, molybdenum-free duplex stainless steel. The Alloy 2304 has corrosion resistance properties similar to 316L. Furthermore, its mechanical properties, i.e., yield strength, are twice those of 304/316 austenitic grades. This allows the designer to save weight, particularly for properly designed pressure vessel applications.
The alloy is particularly suitable for applications covering the -50°C/+300°C (-58°F/572°F) temperature range. Lower temperatures may also be considered but need some restrictions, particularly for welded structures.
With its duplex microstructure and low nickel and high chromium contents, the alloy has improved stress corrosion resistance properties compared to 304 and 316 austenitic grades.

Corrosion Resistance

General Corrosion
Because of its high chromium content (23%) the corrosion resistance properties of 2304 are almost equivalent to those of 316L.

Corrosion resistance in different organic acids

Corrosion resistance to stagnant sulfuric acid (0,3 mm/year)

Localized Corrosion Resistance

The 23% chromium and 0.1% nitrogen additions explain why 2304 duplex stainless steel behaves much better than Alloy 316L when considering pitting and crevice corrosion resistance.

 

Stress Corrosion Resistance

Stress corrosion resistance test results in chloride containing aqueous solutions ((8ppm 02) PH =7, >1000 h, applied stresses higher than the yield strength) show that Alloy 2304 outperforms Alloys 304L and 316L, due to its high chromium additions and low nickel contents.

This is a typical feature of duplex stainless steels. Alloy 2205 performs still better than 2304 in similar conditions.

Other Corrosion Resistance Properties

Alloy 2304 duplex stainless steel successfully passes most of the standard IC test procedures such as ASTM, A262E, and C tests. Its corrosion rate in boiling nitric acid (65%) is higher than that of Alloy 316L. Due to its high yield strength, the alloy performs well in abrasion/corrosion applications.

 

Chemical Analysis

Typical Values (Weight %)

Carbon	Chromium	Nickel	Molybdenum	Nitrogen	Others
0.020	23	4	0.2	0.1	S=0.001
PREN = [Cr%] = 3.3 [Mo%] = 16 [N%] ≥ 24

Interval Temper °C	Thermal expansion ax10M-bK-1	°C	Resistivity (μ_ cm)	Thermal conductivity (W.m-1.K-1)	Specific heat (J.kg-1.K-1	Young modulus E (GPa)	Shear modulus G (GPa)
20-100	13	20	80	17	450	200	75
20-100	13	100	92	18	500	190	73
20-200	13.5	200	100	19	530	180	70
20-300	14	300	105	20	560	170	67

Mechanical Properties

Tensile Properties (Minimum Values)

°C	Rp 0.2 MPa	Rp 1.0 MPa	Rp 1.0 MPa	°F	YS 0.2% Offset KSI	YS 0.1% Offset KSI	UTS KSI	Elongation %
20	400	440	600	68	58	64	87	25
100	330	365	570	212	48	53	83	25
200	280	310	530	392	41	45	77	20
300	230	260	490	572	33	38	71	20