1.4507 / X2CrNiMoCuN25-6-3 steel is a high-alloy, super duplex stainless steel with a dual-phase austenitic-ferritic structure, containing chromium-nickel-molybdenum with the addition of copper and nitrogen. This grade is characterized by high mechanical strength and very good resistance to pitting , crevice , and stress corrosion cracking in chloride-containing environments (UNS S32550 / ASTM A182 F61 / Type 255 and UNS S32520 / ASTM A182 F59).
Materials available at Alfa-Tech 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61
1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61 bars – hot rolled, peeled and drawn
Flat bars 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61
Forged bars 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61
Forgings 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61 – open-die forged, forged cubes and shafts
Pipes 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61
Sheets 1.4507 / X2CrNiMoCuN25-6-3 / UNS S32550 / F61 – hot-rolled and cold-rolled
Phone: +48 63 2610519
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Chemical composition of steel 1.4507 / X2CrNiMoCuN25-6-3 and similar grades UNS S32550 / ASTM A182 F61 / Type 255, UNS S32520 / ASTM A182 F59 / SUS329J4L
| Standard / designation | Type | C | Mn | Si | P | S | Cr | Mo | Ni | Cu | N |
| EN | 1.4507 / X2CrNiMoCuN25-6-3 | <0.03 | <2.0 | <0.7 | <0.035 | <0.015 | 24.0–26.0 | 3.0–4.0 | 6.0–8.0 | 1.0–2.5 | 0.20–0.30 |
| ASTM: | UNS S32550 / ASTM A182 F61 / Type 255 | <0.04 | <1.5 | <1.0 | <0.040 | <0.030 | 24.0–27.0 | 2.9–3.9 | 4.5–6.5 | 1.5–2.5 | 0.10–0.25 |
| ASTM: | UNS S32520 / ASTM A182 F59 | <0.03 | <1.5 | <0.8 | <0.035 | <0.020 | 24.0–26.0 | 3.0–5.0 | 5.5–8.0 | 0.5–3.0 | 0.20–0.35 |
| JIS | SUS329J4L | <0.03 | <1.5 | <1.0 | <0.040 | <0.030 | 24.0–26.0 | 2.5–3.5 | 5.5–7.5 | 0.08–0.30 |
Chemical composition is given in % by mass. Individual grades differ in their required chemical composition, and therefore should not be considered unconditionally interchangeable without verifying the requirements of the standard and the specific application.
Steel 1.4507 / X2CrNiMoCuN25-6-3 – Super Duplex
Steel 1.4507 / X2CrNiMoCuN25-6-3 is a high-alloy stainless steel type Super Duplex with a two-phase austenitic-ferritic microstructure. The high chromium, molybdenum, and nitrogen content, combined with the addition of copper, provides the material with a combination of high mechanical strength and very good resistance to general and localized corrosion.
Grade 1.4507 contains approximately 24–26% chromium, 6–8% nickel, 3–4% molybdenum, 1–2,5% copper and 0,20–0,30% nitrogen. It is therefore a much more highly alloyed steel than classic austenitic steels and standard duplex steels. The combination of chrome, molybdenum i nitrogen, which is responsible for high resistance to local corrosion in chloride environments.
A characteristic feature of 1.4507 is its relatively high content copperThe addition of Cu improves the material's behavior in selected acidic environments, therefore 1.4507 is used in the chemical and petrochemical industries as well as in installations in contact with, among others, sulfuric and phosphoric acid.
Structure of 1.4507 steel – a combination of austenite and ferrite
The properties of 1.4507 steel are largely due to its two-phase microstructure consisting of ferrite and austeniteA properly balanced structure combines the characteristics of both groups of stainless steels: the high mechanical strength of ferrite with the good ductility and corrosion resistance of austenite.
Compared to typical austenitic stainless steels, Super Duplex grades achieve significantly higher yield strengths. This allows for a reduced cross-section in many designs while maintaining the required load-bearing capacity, which is particularly important in pressure equipment, process installations, heat exchangers, and offshore structures.
Corrosion resistance of 1.4507 steel
1.4507 steel is intended primarily for applications in which the material is simultaneously exposed to high mechanical and aggressive loads. corrosive environment. High content of Cr, Mo and N provides very good resistance to pitting corrosion and other forms of local corrosion.
The species is highly resistant to:
- pitting corrosion in environments containing chlorides,
- crevice corrosion,
- SCC stress corrosion cracking in many chloride environments,
- intergranular corrosion,
- general corrosion in many acidic environments,
- the action of sea water, brines and industrial solutions containing chlorides,
- selected environments containing sulfuric, phosphoric and nitric acid.
A material's resistance to intergranular corrosion is particularly important for welded components and equipment operating in aggressive process media. Ultimate corrosion resistance, however, depends not only on the grade designation but also on the microstructure, surface condition, weld quality, temperature, pH, chloride concentration, and the presence of structural crevices.
PREN steel 1.4507
The PREN index is used to roughly compare the resistance of stainless steels to pitting corrosion . For steels without added tungsten, the following relationship is most often used:
PREN = %Cr + 3,3 × %Mo + 16 × %N
For the chemical composition limits of 1.4507, the calculated PREN value can vary significantly. With a typical composition, the material reaches levels characteristic of high-alloy Duplex and Super Duplex steels. However, the PREN value should be considered a comparative parameter – the number alone does not indicate the material's full resistance in a specific installation.
The importance of alloying elements in 1.4507 steel
- Chromium (Cr) – is responsible for the formation of a passive layer that protects the steel surface against corrosion.
- Nickel (Ni) – stabilizes austenite and helps to obtain the appropriate balance of austenitic and ferritic phases.
- Molybdenum (Mo) – significantly improves resistance to pitting and crevice corrosion in chloride environments.
- Nitrogen (N) – increases strength, stabilizes austenite and has a very strong effect on resistance to pitting corrosion.
- Copper (Cu) – improves resistance to some acidic environments, which is one of the characteristic features of the 1.4507 grade.
Mechanical properties of 1.4507 steel
1.4507 steel is characterized by high yield strength and tensile strength. Specific values depend on the product form, dimensions, delivery condition, and material standard. The following values are typical for the supersaturated material:
| Property | Value |
| Tensile strength Rm | 700–900MPa |
| Yield strength Rp0,2 | ≥500MPa |
| Elongation A | ≥ 25% |
| Hardness | ≤ 270 HB |
| Elastic modulus E | approx. 190–200 GPa |
It's worth noting that, depending on the standard and product form, the requirements may be higher. For some 1.4507 products, a minimum yield strength Rp0,2 of approximately 550 MPa and a minimum tensile strength Rm of approximately 760 MPa are encountered.
Physical properties of steel 1.4507
| Property | Indicative value |
| Density | approx. 7,85 g/cm³ |
| Specific heat | approx. 500 J/(kg K) |
| Thermal conductivity | approx. 18 W/(m·K) |
| Modulus of elasticity | approx. 190–200 GPa |
| Electrical resistivity | approx. 0,95 Ω mm²/m |
Properties of 1.4507 steel at elevated temperatures
As temperature increases, the yield strength and modulus of elasticity of steel decrease. This phenomenon must be taken into account when designing process equipment, heat exchangers, and pressure equipment.
| Temperature | 100°C | 150°C | 200°C | 250°C | 300°C |
| Linear expansion coefficient α × 10−6 K−1 | 13,0 | 13,5 | 14,0 | ||
| Elastic modulus E | 194 GPa | 186 GPa | 180 GPa | ||
| Yield strength Rp0,2 | ≥450MPa | ≥420MPa | ≥400MPa | ≥380MPa |
Heat treatment of 1.4507 steel
Proper heat treatment of Super Duplex steel is essential to maintaining a favorable phase balance and high corrosion resistance. The grade is generally supplied in a solution-hardened condition.
The solution heat treatment temperature depends on the product form and the requirements of the relevant standard. For products from the 1.4507 / F255 group, temperatures of approximately 1040°C and higher, after which rapid cooling is necessary. Processing parameters should always be selected according to the specific product standard.
The time the material remains in the temperature range favoring the formation of intermetallic phases, especially sigma phases, should be limited. Their separation can lead to reduced impact strength, ductility, and corrosion resistance.
Plastic processing of 1.4507 steel
Steel can be forged and hot-rolled, but due to its high alloying content, it requires strict temperature control. Hot working is performed at high temperatures, avoiding excessive holding of the material in a range that promotes the precipitation of unfavorable phases.
After extensive hot working, solution heat treatment and rapid cooling may be required to restore optimal microstructure and corrosion resistance.
Weldability of 1.4507 steel
1.4507 steel is weldable, but like other Super Duplex steels, it requires a controlled welding process. The primary goal of welding technology is to maintain the proper balance between ferrite and austenite in the weld and the heat-affected zone.
Heat input, interpass temperature, filler metal composition, and cooling rate must be controlled. Both excessive and insufficient heat input can degrade the joint's structure and properties. In critical applications, qualified welding procedures appropriate for duplex and super duplex steels should be used.
Application of steel 1.4507 / X2CrNiMoCuN25-6-3
The combination of high strength, chloride resistance and good resistance to a number of aggressive chemicals means that 1.4507 is used primarily in the chemical, petrochemical, energy, marine and process equipment industries.
Typical applications include:
- pipelines and process installations,
- chemical tanks,
- heat exchangers and coolers,
- pump and compressor components,
- shafts, bushings and mechanically loaded elements,
- valves and industrial fittings parts,
- screws and fasteners,
- elements of pressure equipment,
- chemical and petrochemical industry installations,
- pulp and paper industry equipment,
- installations in contact with sea water and brines,
- offshore and oil & gas installation elements.
1.4507 and other Super Duplex steels
1.4507 steel belongs to the same broad family of high-alloy ferritic-austenitic steels as 1.4410 / X2CrNiMoN25-7-4 and other Super Duplex grades. However, this does not mean they are completely interchangeable. Differences in nickel, molybdenum, nitrogen, and, above all, copper content affect corrosion resistance, mechanical properties, and material behavior in specific chemical environments.
The selection between the different Super Duplex grades should take into account not only the PREN value, but also the type of medium, operating temperature, chloride content, pH, strength requirements, welding method and the requirements of the standards for the specific product form.
Duplex steel
1.4362 – chromium-nickel duplex steel with the addition of molybdenum, copper and nitrogen X2CrNiN23-4, UNS S32304, Duplex 2304
1.4162 – chromium-manganese-nickel duplex steel with the addition of Mo and Cu X2CrMnNiN21-5-1, UNS S32101, LDX 2101®, A182 F69.
1.4460 – chromium-nickel-molybdenum duplex steel with the addition of nitrogen X3CrNiMoN27-5-2, AISI 329, UNS S32900, SS 2324.
1.4462 – chromium-nickel-molybdenum duplex steel with the addition of nitrogen X2CrNiMoN22-5-3, UNS S31803, S32205, Duplex 2205
Super Duplex
1.4410 – Super Duplex Chromium-Nickel-Molybdenum Steel with Nitrogen Addition X2CrNiMoN25-7-4 – UNS S32750 – Super Duplex 2507
1.4501 – super duplex chromium-nickel-molybdenum steel with the addition of Cu, W and N X2CrNiMoCuWN25-7-4 – UNS S32760
1.4507 – super duplex chromium-nickel-molybdenum steel with the addition of Cu and N X2CrNiMoCuN25-6-3 – UNS S32550 – F61 / Alloy 255
See also other corrosion-resistant steels
Stainless steels
Martensitic stainless steels
Ferritic stainless steels
Austenitic and acid-resistant stainless steels
- H18N10MT – X6CrNiMoTi17-12-2 / 1.4571 / AISI 316Ti
- H18N12Nb – X6CrNiNb18-10 / 1.4550 / AISI 347
- H17N13M2T – X6CrNiMoTi17-12-2 / 1.4571 / AISI 316Ti
- 00H17N14M2 – 1.4404 / AISI 316L
- 1H18N9 – X10CrNi18-8 / 1.4310 / AISI 302
- 1H18N9T – X6CrNiTi18-10 / 1.4541 / AISI 321
- 0H18N9 – X5CrNi18-10 / 1.4301 / AISI 304
- 0H23N28M3TCu – X1NiCrMoCu25-20-5 / 1.4539 / AISI 904L
- 1.4567 – X3CrNiCu18-9-4 / AISI 304Cu
- 1.4529 – X1NiCrMoCuN25-20-7 / AISI 926 / UNS N08926
Precipitation hardening (PH) stainless steels
Austenitic-ferritic stainless steels (Duplex)
Lean Duplex
Duplex
Heat-resistant and creep-resistant steels
- H5M – 12CrMo19-5 / 1.7362
- H6S2 – X10CrAl7 / 1.4713
- H13JS – X10CrAl13 / 1.4724
- H18JS – X10CrAl18 / 1.4742
- H24JS – X10CrAl24 / 1.4762
- H25T – X8CrTi25 / 1.4746
- H20N12S2 – X15CrNiSi20-12 / 1.4828
- H23N13 – X12CrNi23-13 / 1.4833
- H23N18 – X12CrNi25-21 / 1.4845
- H25N20S2 – X15CrNiSi25-20 / 1.4841
- H16N36S2 – X12NiCrSi35-15 / 1.4864
- 1.4835 – 253 MA / X9CrNiSiNCe21-11-2
- 1.4876 – X10NiCrAlTi32-21 / Alloy 800