1. Įvadas
CF3 stainless steel, Austenitinių aktorių nerūdijančio plieno šeimos narys, is the low-carbon cast equivalent of the popular wrought grade 304L (JAV S30403).
It is defined under ASTM A351 and widely used in industries where corrosion resistance, suvirinamumas, and castability are paramount.
The “C” in CF3 stands for “Corrosion-resistant”, “F” denotes the steel grade (304L equivalent), and the number “3” identifies its low carbon content (≤ 0.03%).
Istoriškai, CF3 emerged as part of the response to corrosion issues in chloride-rich and welding-intensive applications.
The introduction of low-carbon grades in the mid-20th century was a milestone that enabled the development of high-integrity welded structures without the need for post-weld heat treatment.
Due to its balanced combination of cost-effectiveness, Spektaklis, and resistance to sensitization,
CF3 continues to be strategically important in cast stainless steel applications across chemical, naftos chemija, Vandens valymas, and food-processing sectors.
2. Cheminė sudėtis & Metalurgija
Nominali cheminė sudėtis
The typical weight percentage (Wt.%) of the alloying elements in CF3 stainless steel, as defined by ASTM A351, yra:
| Elementas | Tipiškas diapazonas (Wt.%) | Funkcija |
|---|---|---|
| Chromas (Kr) | 18.0 - 21.0% | Promotes corrosion resistance through passive film formation |
| Nikelis (Į) | 8.0 - 11.0% | Stabilizuoja austenite, improves ductility and toughness |
| Anglies (C) | ≤ 0.03% | Reduces sensitization; improves weldability |
| Manganas (Mn) | ≤ 1.5% | Enhances hot workability; deoxidizer |
| Silicis (Ir) | ≤ 2.0% | Skatina liejimo sklandumą; deoxidizer |
| Fosforas (P) | ≤ 0.04% | Residual; must be minimized to reduce brittleness |
| Sieros (S) | ≤ 0.04% | Residual; excessive S can reduce toughness |
| Lygintuvas (Fe) | Pusiausvyra | Matrix element |
The Mažas anglies kiekis (≤ 0.03%) significantly mitigates the risk of chromium carbide precipitation at grain boundaries during welding,
making CF3 especially resistant to intergranular corrosion without requiring post-weld heat treatment.
Mikrostruktūra: Austenitinė matrica & Carbide Control
CF3 stainless steel has a fully austenitic microstructure with a face-centered cubic (FCC) lattice, which contributes to:
- Excellent toughness at both ambient and cryogenic temperatures.
- Non-magnetic behavior in the annealed state.
- Resistance to stress corrosion cracking (SCC) in many chloride-containing environments.
Due to its low carbon content, CF3 contains minimal chromium carbides, particularly at grain boundaries.
This improves resistance to sensitization, a condition in which chromium-depleted zones form and become vulnerable to corrosive attack.
Some residual delta ferrite (paprastai < 10%) may be present after solidification, particularly in sand-cast components.
which helps prevent hot cracking during solidification, but has minimal impact on corrosion resistance or toughness when kept at controlled levels.
3. ASTM A351 CF3 and Global Equivalents
| Standartas | Paskyrimas | Regionas | Equivalent Grade |
|---|---|---|---|
| ASTM A351 | Grade CF3 | JAV | Low-carbon cast 304L |
| ASME SA-351 | Grade CF3 | JAV (boiler code) | Pressure vessel compliant |
| Į 10283 | GX2CRNI19-11 | European Union | Vaidina 1.4306 (304L) |
| ISO 11972 | G-X2CrNi19-11 | Tarptautinis | Global harmonized equivalent |
| JIS G5121 | SCS13A | Japonija | 304L cast grade |
4. Mechaninės savybės
| Mechaninė nuosavybė | Tipinė vertė |
|---|---|
| Tempimo stiprumas | ≥485 MPa |
| Derliaus stiprumas (0.2% poslinkis) | ≥205 MPa |
| Pailgėjimas | ≥30% |
| Kietumas | 140–190 HB |
| Poveikis kietumas (Kambario temp) | > 100 J (Charpy V-Notch) |
| Fatigue Endurance Limit | 240–270 MPA (in air, poliruotas) |
| Šliaužimo pasipriešinimas | Moderate up to 870°C |
Esant pakilusi temperatūrai, tensile and yield strengths decrease gradually, but the alloy retains sufficient structural integrity up to 400–500 °C, making it viable for moderate thermal service.
5. Šiluminis & Fizinės savybės
| Nuosavybė | Vertė |
|---|---|
| Tankis | ~ 7,9 g/cm³ |
| Šilumos laidumas | ~ 16 w/m · k (at 100°C) |
| Coefficient of Expansion | 17.3 µm/m · ° C. (20–400°C) |
| Elektros varža | 0.72 µΩ · m |
| Magnetinis atsakas | Nemagnetinis (atkaitintas) |
| Atsparumas oksidacijai | Good up to ~800°C |
6. Casting Characteristics of CF3 Stainless Steel
CF3 stainless steel—cast equivalent of 316—brings molybdenum‑enhanced corrosion resistance into complex geometries.
To harness its full potential, foundries must account for its unique casting behavior, from melt handling to solidification control.
Sklandumas & Pilimo temperatūra
CF3 melts between 1450 ° C ir 1550 ° C., slightly higher than CF8 due to its Mo content.
At a pouring superheat of 1500–1560 °C, CF3 achieves a fluidity of 220–280 mm (ISO 243), enabling fill of thin‑walled sections down to 4 mm.
Tačiau, excessive superheat can increase gas pickup ir oksidacija, so operators typically limit superheat to 50 ° C. above liquidus.
Solidification Range & Susitraukimas
Su a užšalimo diapazonas maždaug 60–90 °C, CF3 solidifies over a broader temperature interval than simple austenitic alloys.
Todėl, it exhibits linijinis susitraukimas iš 1.9–2.3 %, necessitating careful shrink‑compensation in pattern design.
Užkirsti kelią Centrinės linijos poringumas, engineers employ kryptinis kietėjimas: placing insulated risers above hot spots and using šaltkrėtis to accelerate freezing in thick sections.
Feeding & Riser Design
Given its moderate shrinkage, CF3 castings benefit from risers sized to feed 30–40 % of the casting mass they support.
Finite‑element thermal simulation often guides riser placement, ensuring uninterrupted metal flow into contracting zones.
Be to, Egzoterminės rankovės on critical risers prolong feeding life without increasing overall mold volume.
Degazavimas, Deoxidation & Inoculation
To minimize gas porosity, foundries typically argon‑purge the molten CF3 before pouring.
They also add Silicis (0.3–0.6 %) ir aliuminis (0.02–0.05 %) deoxidizers, which form stable oxides and reduce dissolved oxygen.
Pagaliau, a small rare‑earth inoculant (Pvz., 0.03–0.05 % Fe‑Ce) promotes fine, uniform δ‑ferrite and prevents microshrinkage, enhancing mechanical consistency.
Suitable Casting Methods for CF3 Stainless Steel
| Liejimo metodas | Tipiškos programos | Privalumai | Svarstymai |
|---|---|---|---|
| Smėlio liejimas (Green or No-Bake) | Vožtuvo kūnai, siurblių korpusai, flanšai | – Cost-effective for large parts – Flexible for varied designs |
– Rougher surface finish (Ra 6–12 μm) – Tighter control needed for porosity |
| Korpuso pelėsio liejimas | Instrumentation covers, small valves | – Good dimensional accuracy (±0.3%) – Fine surface finish (Ra 3–6 μm) |
– More expensive molds – Best for small to medium-sized parts |
| Investicijų liejimas (Pamestas vaškas) | Sparnuotojai, medical fittings, Didelio tikslumo komponentai | – Excellent surface finish (Ra < 3 μm) – High geometric complexity |
– Higher cost – Limited to small–medium parts |
| Išcentrinis liejimas | Įvorės, Žiedai, pipe sections | – High density – Low porosity – Good mechanical properties in radial direction |
– Suitable only for rotationally symmetric parts |
| Vakuuminis liejimas | Critical components in aerospace, nuclear applications | – Reduced oxidation – Cleaner microstructure |
– Expensive – Requires specialized equipment |
| Keraminių pelėsių liejimas | Complex heat-resistant parts | – Excellent surface detail – Good dimensional precision |
– Longer mold preparation time – Higher cost |
Heat Treatment Practices
Po liejimo, CF3 typically undergoes Sprendimo atkaitinimas į diapazoną 1040–1120 ° C. (1900–2050°F) followed by rapid water quenching. This process serves several purposes:
- Dissolves residual carbides, restoring corrosion resistance
- Homogenizes the microstructure, eliminating segregation from solidification
- Improves ductility and toughness by removing delta ferrite or brittle phases
Strict temperature control during annealing is critical. Insufficient quenching rates can result in jautrumas ir chromium depletion prie grūdų ribų, compromising corrosion resistance.
7. Atsparumas korozijai
Bendroji korozija
In neutral and mildly acidic environments, CF3 maintains excellent resistance due to its chromium-rich passive film. Corrosion rates are typically < 0.05 mm/year in potable water and wastewater systems.
Localized Corrosion Resistance
The alloy shows good performance in environments containing chlorides up to ~200 ppm:
- Atsparumo atsparumo ekvivalentinis skaičius (Mediena): ~ 18
- Critical Pitting Temperature (CPT): ~ 20–25 ° C. (varies with chloride level)
Streso korozijos įtrūkimas (SCC)
CF3’s low carbon content improves SCC resistance in chloride-bearing environments, particularly in the 50–100°C range, a known danger zone for austenitic grades.
8. Gaminimas & Aparatas
CNC apdirbimas
CF3 machines comparably to wrought 304, with a machinability index of ~45 % (Kur 304 equals 50 %).
Shops typically use carbide tools, cutting speeds of 100–150 m/min, and feeds of 0.12–0.18 mm/rev, delivering surface finishes around Ra 1.6 µm.
Suvirinimas
Fabricators weld CF3 using 309 arba 312 filler alloys without preheat.
Post‑weld annealing at 1,050 °C for one hour restores corrosion resistance, reducing delta‑ferrite and dissolving weld‑zone carbides.
Formavimas & Prisijungimas
Although CF3’s work‑hardening rate lags that of carbon steel, it tolerates cold forming reductions up to 40 %.
To prevent springback, designers recommend bend radii of at least 3× material thickness.
9. Applications of CF3 Stainless Steel
Vožtuvai, Siurbliai, and Fittings in Water Treatment
In municipal and industrial water treatment facilities, CF3 stainless steel is a material of choice for:
- Valve bodies and bonnets
- Pump casings and impellers
- Pipe fittings and couplings
Its resistance to chloride-induced corrosion, even in brackish or mildly saline environments, ensures long service life with minimal maintenance.
The low carbon content reduces the risk of sensitization during welding, which is critical for pressure-retaining systems.
Petrochemical and Oil & Gas Components
The oil and gas industry frequently uses CF3 for castings that encounter corrosive fluids, including hydrocarbons, hydrogen sulfide, and CO₂-rich environments. Įprastos programos apima:
- Kompresoriaus korpusai
- Manifolds and flowline components
- Metering valves and flanges
In up- and midstream systems, CF3 helps prevent stress-corrosion cracking (SCC) ir duobė, which are accelerated by high chloride content or wet sour gas.
Food Processing and Pharmaceutical Equipment
Hygienic process systems require materials with excellent corrosion resistance, Lygus paviršiaus apdaila, and compatibility with cleaning agents (CIP/SIP). CF3 fits these requirements, todėl tai tinka:
- Sanitary valves and pipe fittings
- Mixing and metering equipment
- Dosing pumps and housings
Jo austenitic microstructure, which remains stable even after repeated sterilization cycles, helps meet FDA ir 3-A Sanitary Standards in critical production environments.
Power Generation and Marine Hardware
- Steam and condensate system components
- Seawater pumps and valve parts
- Heat exchanger end covers
Its resistance to aqueous corrosion, biologinis, ir oxidation at elevated temperatures enhances component longevity in these aggressive settings.
In marine environments, CF3 performs reliably in both surface and submerged service.
Other Emerging Applications
- Hydrogen handling systems: Due to its non-magnetic and crack-resistant nature
- Semiconductor wet-processing tools: Where ultra-clean, non-reactive materials are needed
- Additive-manufactured cast components: For reduced weight and complex design integration
10. Palyginimas su alternatyviomis medžiagomis
Selecting the appropriate stainless steel grade for a given application requires a deep understanding of the performance trade-offs between available options.
CF3 stainless steel, as the low-carbon cast equivalent of 304L, is often compared to related alloys such as CF3M, CF8, CF8M, and wrought 304 nerūdijantis.
| Nuosavybė | CF3 (304L CAST) | CF3M (316L CAST) | CF8 (304 Aktoriai) | CF8M (316 Aktoriai) | 304L Wrought |
|---|---|---|---|---|---|
| Molibdenas (MO) Turinys | Nr | Taip | Nr | Taip | Nr |
| Anglies kiekis | ≤ 0.03% (Žemas anglis) | ≤ 0.03% (Žemas anglis) | ≤ 0.08% | ≤ 0.08% | ≤ 0.03% (Žemas anglis) |
| Chlorido atsparumas | Vidutinis | Puiku | Vidutinis | Puiku | Vidutinis |
| Pasipriešinimas (Mediena) | ~ 18 | ~ 25–27 | ~20 | ~ 25–27 | ~ 18 |
| Atsparumas korozijai | Gerai | Puiku | Vidutinis | Puiku | Gerai |
| Suvirinamumas | Puiku | Puiku | Vidutinis | Vidutinis | Puiku |
| Kaina | $$ | $$$ | $$ | $$$ | $$ |
| Stiprybė (Tempimas) | ~ 485 MPA | ~500 MPa | ~510 MPa | ~520 MPa | ~520 MPa |
| Pailgėjimas | ~ 40% | ~45% | ~45% | ~45% | ~45% |
| Formavimas | Excellent for cast parts | Excellent for cast parts | Good for cast parts | Good for cast parts | Puiku (for rolled or formed parts) |
| Paraiškos | Water systems, food-grade parts | Cheminė, jūrų, jūroje | General industrial parts | Jūrų, Cheminė, jūroje | High-ductility, Plonos sienos dalys |
11. Išvada
Apibendrinant, CF3 stainless steel merges the proven corrosion resistance of 304 with the versatility of casting.
Its balanced chemistry, robust mechanical profile, and proven long‑term durability make CF3 an authoritative choice for medium‑duty corrosive environments.
Be to, with annual global production exceeding 50,000 tonnes and scrap rates under 6 %, CF3 delivers both economic and performance advantages.
Laukiau, integrating CF3 into hybrid casting–additive workflows and exploring surface treatments promises to extend its service envelope—ensuring CF3 remains a cornerstone alloy in industrial applications.
Langhe yra puikus pasirinkimas jūsų gamybos poreikiams, jei jums reikia aukštos kokybės Nerūdijančio plieno liejiniai.
Susisiekite su mumis šiandien!
FAQs on CF3 Stainless Steel
Is CF3 Stainless Steel suitable for high-temperature applications?
CF3 is generally suitable for moderate-temperature applications (up to about 800°F or 427°C).
For higher temperatures, or when Atsparumas oksidacijai at elevated temperatures is critical,
other grades like CF8M arba 316 Nerūdijantis plienas may be more appropriate due to their enhanced high-temperature properties.
Can CF3 be welded?
Taip, CF3 stainless steel is highly suvirinamas. Its low carbon content minimizes the risk of carbide formation during welding, reducing the chances of intergranular corrosion.
Tačiau, it is always recommended to use appropriate welding techniques ir post-weld heat treatments when working with this material in critical applications.
Is CF3 Suitable for Cryogenic Applications?
Taip, CF3 exhibits good toughness at low temperatures, making it suitable for use in cryogenic applications such as liquefied natural gas (LNG) storage and transportation.
Can CF3 Be Heat Treated?
CF3 is generally not heat treatable for strengthening purposes. Tačiau, it can be annealed to relieve stresses and improve machinability.
How does CF3 Stainless Steel perform in seawater?
CF3 offers moderate resistance to seawater corrosion, but it is not as resistant as CF3M or CF8M, which have enhanced chloride resistance due to the presence of molibdenas.
Į Jūrų aplinka with high salinity, CF3 may experience some Korozija Laikui bėgant, so CF3M or CF8M might be more suitable.
How should CF3 Stainless Steel be maintained?
Regular maintenance of CF3 stainless steel includes:
- Valymas: Removing contaminants such as chlorine, druska, and chemicals that could cause localized corrosion.
- Tikrinimas: Checking for any signs of duobė arba įtrūkimų korozija, ypač jūrų arba chemical environments.
- Suvirinimas: Ensuring proper po suvirinimo terminis apdorojimas to avoid cracking or sensitization.
Can CF3 Stainless Steel be used in food contact applications?
Taip, CF3 is often used in Maisto perdirbimo įranga Dėl jos atsparumas korozijai ir ease of cleaning.
It complies with FDA ir 3-A Sanitary Standards, todėl tai yra tinkamas pasirinkimas sanitarinė vožtuvai, Siurbliai, ir vamzdynų sistemos.
