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Ferralium 255
What is F255 material?
Ferralium 255 – super duplex 4507 is a super duplex stainless steel supplied in the hot worked and annealed condition. It achieves higher strengths than most stainless steels and alternative corrosion resistant alloys, offering the potential to reduce section size and therefore weight and cost.
As a 25% Cr alloy, with significant additions of copper, Ferralium® 255 offers excellent corrosion resistance in a wide variety of corrosive chemicals including sulphuric, nitric and phosphoric acid. In seawater and other chloride containing environments it also provides outstanding resistance to pitting and crevice corrosion, with Critical Pitting Temperature exceeding 50°C. Excellent ductility and impact strength at both ambient and sub-zero temperatures combine with a high resistance to abrasion, erosion and cavitation erosion.
Listed in NACE MR 01 75 for sour service and having gained ASME Approval for Pressure Vessel applications, Ferralium® 255-SD50 is tested to the highest degree using tests designed to guarantee that the trade-marked product possesses high integrity, a correct phase balance and the absence of sigma and other deleterious phases.
FERRALIUM 255, UNS S32550 chemical composition
Cr 25.5, Ni 5.5, Mo 3.4 C 0.04, Mn 1.5, Si 1.0, Fe Bal, N 0.175, S 0.030, Cu 2.00, P 0.040
Applications s32550, F61
FERRALIUM 255 is a cost-effective alternative to materials such as the nickel alloys, 20 type alloys, brass and bronze. Marine environments have long been the domain of admiralty bronze. Alloy 255 is replacing admiralty bronze, and the nickel alloys, in offshore platforms, deck hardware, rudders and shafting.
Alloy 255 is also making inroads in “borderline” corrosion applications where the nickel alloys and high-performance alloys have been used but may not have been absolutely necessary. In some instances, it has even been used to replace high performance Ni-Cr-Mo-F-Cu alloys in the phosphoric acid industry.
Valves, pumps, shafts, marine environments, Applications in down-hole, waste water, polycarbonate production, and demineralized water production.
| UNS S32550 Properties | |||||
|---|---|---|---|---|---|
| Ultimate Tensile | Yield Strength (0.2% OS) | Elong. | R/A | Hardness Brinell | |
| Min | 110 KSi | 80 KSi | 15% | ||
| Max | 297 | ||||
| Min | 760 MPa | 550 MPa | |||
| Max | |||||
| Is Stronger Than Most Competitive Alloys | ||||
|---|---|---|---|---|
| Alloy | UNS | Typical Tensile (Ksi) | Typical Yeild (Ksi) | Typical Elongation (%) |
| Alloy 255 | S32550 | 126 | 98 | 30 |
| SUS316L | S31603 | 81 | 42 | 50 |
| NiCu400 | N04400 | 78 | 31 | 50 |
| 20Cb-3 | N08020 | 92 | 47 | 39 |
| 2205 Duplex | S31803 | 112 | 75 | 32 |
A182 F61, Technical Data
| Elongation Comparison | |||
| Elongation | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| 40 | 25 | 15 | |
| Hardness Comparison | |||
| Wear Resistance | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| Hardness | RB80 | RC21 | RC28 |
| Critical Pitting Temperature Comparison | |||
| Critical Pitting Temperature | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| Degree C ASTM G48-Method A | 0 | 20 | 40 |
| Pitting Potential – MV Comparison | |||
| Temperature | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| 50 oC | 60 | 370 | No Pitting |
| 60 oC | No Test | No Test | 110 |
| 60 oC | No Test | No Test | 170 |
| Critical Crevice Comparison | |||
| Temperature | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| Degree C ASTM G48-Method B (10% FE CL 6H 0) |
-2.5 | 17.5 | 22.5 |
| C Ring Stress Cracking Comparison | |||
| Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 | |
| 80 Degree C Stressed to 100% Yield Strength, H2S0.125 Bar, Sour Brine with 46,000 MG/L Chloride | Cracks | Fine Cracks | No Cracks |
| PREN No. Comparison | |||
| Resistance to Localized Corrosion | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| PREN No. CR + 3.3(MO) + 16(N) | 23.6 | 34.5 | 40 |
| Corrosion Rates Comparison | |||
| Corrosion Rates MPY | Alloy 316SS | Alloy 2205 | Ferralium Alloy 255 |
| 10% Sulfuric Boiling | 855 | 206 | 40 |
| 65% Nitric Boiling | 11 | 21 | 5 |
What is difference between duplex and super duplex?
Duplex stainless steels are based around a composition of 22% chromium, whereas super duplex stainless steels are based around a composition of 25% chromium. By increasing the chromium content, the level of pitting corrosion resistance is also increased.
