1. مقدمه
CF3 stainless steel, a member of the austenitic cast stainless steel family, is the low-carbon cast equivalent of the popular wrought grade 304سعادت (ایالات متحده S30403).
It is defined under ASTM A351 and widely used in industries where corrosion resistance, قابلیت جوشکاری, and castability are paramount.
در “C” in CF3 stands for “Corrosion-resistant”, “F” denotes the steel grade (304L equivalent), and the number “3” identifies its low carbon content (رده 0.03%).
از نظر تاریخی, 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, عمل, and resistance to sensitization,
CF3 continues to be strategically important in cast stainless steel applications across chemical, پتروشیمی, تصفیه آب, and food-processing sectors.
2. ترکیب شیمیایی & متالورژی
ترکیب شیمیایی اسمی
The typical weight percentage (وزنی ٪) of the alloying elements in CF3 stainless steel, as defined by ASTM A351, است. است:
| عنصر | دامنه معمولی (وزنی ٪) | عمل |
|---|---|---|
| کروم (کلوچه) | 18.0 - 21.0% | Promotes corrosion resistance through passive film formation |
| نیکل (در) | 8.0 - 11.0% | آستنیت را تثبیت می کند, improves ductility and toughness |
| کربن (جف) | ≤ 0.03% | Reduces sensitization; improves weldability |
| منگنز (منگنه) | ≤ 1.5% | Enhances hot workability; deoxidizer |
| سیلیکون (وت) | ≤ 2.0% | باعث افزایش سیالیت در ریخته گری می شود; deoxidizer |
| فسفر (پ) | ≤ 0.04% | Residual; must be minimized to reduce brittleness |
| گوگرد (حرف) | ≤ 0.04% | Residual; excessive S can reduce toughness |
| اتو کردن (با) | تعادل | Matrix element |
در محتوای کربن کم (رده 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.
ساختار: ماتریس آستنیتی & 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 (به طور معمول < 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
| استاندارد | تعیین | منطقه | Equivalent Grade |
|---|---|---|---|
| ASTM A351 | Grade CF3 | ایالات متحده آمریکا | Low-carbon cast 304L |
| ASME SA-351 | Grade CF3 | ایالات متحده آمریکا (boiler code) | Pressure vessel compliant |
| در 10283 | GX2CRNI19-11 | European Union | نسخه بازیگران از 1.4306 (304سعادت) |
| ISO 11972 | G-X2CrNi19-11 | بین المللی | Global harmonized equivalent |
| او g5121 | SCS13A | ژاپن | 304L cast grade |
4. خصوصیات مکانیکی
| خاصیت مکانیکی | ارزش معمولی |
|---|---|
| استحکام کششی | 485 MPa |
| قدرت عملکرد (0.2% جبران کردن) | MPa 205 پوند |
| کشیدگی | 30 ≥ |
| سختی | 140-190 HB |
| سختی (دم) | > 100 J (Charpy V-Notch) |
| Fatigue Endurance Limit | 240-270 MPa (in air, صیقلی) |
| مقاومت در برابر خزش | Moderate up to 870°C |
در دمای بالا, 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. گرمی & خصوصیات فیزیکی
| دارایی | ارزش |
|---|---|
| تراکم | 7.9 گرم در سانتی متر مربع |
| هدایت حرارتی | ~ 16 w/m · k (at 100°C) |
| Coefficient of Expansion | 17.3 میکرومتر در متر · درجه سانتیگراد (20–400°C) |
| مقاومت الکتریکی | 0.72 μΩ · m |
| واکنش مغناطیسی | غیر عجیبی (ساکت شده) |
| مقاومت در برابر اکسیداسیون | 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.
سیالیت & ریختن دما
CF3 melts between 1450 ° C و 1550 درجه سانتیگراد, 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 میلی متر.
هر چند, excessive superheat can increase gas pickup و اکسیداسیون, so operators typically limit superheat to 50 درجه سانتیگراد above liquidus.
Solidification Range & انقباض
با دامنه انجماد از حدود 60–90 °C, CF3 solidifies over a broader temperature interval than simple austenitic alloys.
در نتیجه, it exhibits انقباض خطی از 1.9–2.3 %, necessitating careful shrink‑compensation in pattern design.
برای جلوگیری از تخلخل خط مرکزی, engineers employ جامد سازی جهت دار: placing insulated risers above hot spots and using لرز 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.
علاوه بر این, آستین های گرمازدایی on critical risers prolong feeding life without increasing overall mold volume.
قصور, Deoxidation & Inoculation
To minimize gas porosity, foundries typically argon‑purge the molten CF3 before pouring.
They also add سیلیکون (0.3–0.6 %) وت الومینیوم (0.02–0.05 %) deoxidizers, which form stable oxides and reduce dissolved oxygen.
بالاخره, a small rare‑earth inoculant (به عنوان مثال, 0.03–0.05 % Fe‑Ce) promotes fine, uniform δ‑ferrite and prevents microshrinkage, enhancing mechanical consistency.
Suitable Casting Methods for CF3 Stainless Steel
| روش ریخته گری | برنامه های معمولی | مزایا | ملاحظات |
|---|---|---|---|
| ریخته گری (Green or No-Bake) | بدنهای, محفظه پمپاژ, فلنج | – Cost-effective for large parts – Flexible for varied designs |
– Rougher surface finish (Ra 6–12 μm) – Tighter control needed for porosity |
| ریخته گری قالب | 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 |
| ریخته گری سرمایه گذاری (موم گمشده) | سرپرست, medical fittings, اجزای با دقت بالا | – Excellent surface finish (رگ < 3 μm) – High geometric complexity |
– Higher cost – Limited to small–medium parts |
| ریخته گری | بوش, حلقه, pipe sections | – High density – Low porosity – Good mechanical properties in radial direction |
– Suitable only for rotationally symmetric parts |
| ریخته گری خلاء | Critical components in aerospace, nuclear applications | – Reduced oxidation – Cleaner microstructure |
– Expensive – Requires specialized equipment |
| ریخته گری قالب سرامیکی | Complex heat-resistant parts | – Excellent surface detail – Good dimensional precision |
– Longer mold preparation time – Higher cost |
Heat Treatment Practices
بعد از ریخته گری, CF3 typically undergoes بازپخت راه حل در محدوده 1040-1120 درجه سانتیگراد (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 حساسیت وت chromium depletion در مرزهای دانه, compromising corrosion resistance.
7. مقاومت در برابر خوردگی
خوردگی عمومی
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:
- تعداد معادل مقاومت مقاومت (چوب): 18 پوند
- Critical Pitting Temperature (CPT): 20-25 درجه سانتیگراد (varies with chloride level)
ترک خوردگی (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. ساختگی & قابلیت تغییر
ماشینکاری CNC
CF3 machines comparably to wrought 304, with a machinability index of ~45 % (کجا 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.
جوش
Fabricators weld CF3 using 309 یا 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.
تشکیل دهنده & پیوستن
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
دریچه, پمپ, 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. برنامه های مشترک شامل:
- محفظه کمپرسور
- Manifolds and flowline components
- Metering valves and flanges
In up- and midstream systems, CF3 helps prevent stress-corrosion cracking (SCC) وت گودال, 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, پایان سطح صاف, and compatibility with cleaning agents (CIP/SIP). CF3 fits these requirements, مناسب کردن آن برای:
- Sanitary valves and pipe fittings
- Mixing and metering equipment
- Dosing pumps and housings
آن را austenitic microstructure, which remains stable even after repeated sterilization cycles, helps meet FDA وت 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, سوخت, وت 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. مقایسه با مواد جایگزین
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 ضد زنگ.
| دارایی | CF3 (304بازیگران) | cf3m (316بازیگران) | cf8 (304 بازی کردن) | cf8m (316 بازی کردن) | 304L Wrought |
|---|---|---|---|---|---|
| مولیبدن (مس) محتوا | هیچ | بله | هیچ | بله | هیچ |
| میزان کربن | رده 0.03% (کربن کم) | رده 0.03% (کربن کم) | رده 0.08% | رده 0.08% | رده 0.03% (کربن کم) |
| مقاومت کلرید | معتاد | عالی | معتاد | عالی | معتاد |
| مقاومت در برابر گودال (چوب) | 18 پوند | 25-27 پوند | ~20 | 25-27 پوند | 18 پوند |
| مقاومت در برابر خوردگی | خوب | عالی | معتاد | عالی | خوب |
| قابلیت جوشکاری | عالی | عالی | معتاد | معتاد | عالی |
| هزینه | $$ | $$$ | $$ | $$$ | $$ |
| قدرت (کشنده) | 485 پوند MPa | ~500 MPa | ~510 MPa | ~520 MPa | ~520 MPa |
| کشیدگی | 40 ٪ | ~45% | ~45% | ~45% | ~45% |
| قابلیت تشکیل | Excellent for cast parts | Excellent for cast parts | Good for cast parts | Good for cast parts | عالی (for rolled or formed parts) |
| برنامه | Water systems, food-grade parts | شیمیایی, دریایی, خارج از ساحل | General industrial parts | دریایی, شیمیایی, خارج از ساحل | High-ductility, قطعات دیواره نازک |
11. پایان
به طور خلاصه, 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.
علاوه بر این, with annual global production exceeding 50,000 tonnes and scrap rates under 6 %, CF3 delivers both economic and performance advantages.
منتظر, 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 در صورت نیاز به کیفیت بالا ، انتخاب مناسبی برای نیازهای تولیدی شما است ریخته گری های استیل ضد زنگ.
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 مقاومت در برابر اکسیداسیون at elevated temperatures is critical,
other grades like cf8m یا 316 فولاد ضد زنگ may be more appropriate due to their enhanced high-temperature properties.
Can CF3 be welded?
بله, CF3 stainless steel is highly جوش داده شده. Its low carbon content minimizes the risk of carbide formation during welding, reducing the chances of intergranular corrosion.
هر چند, it is always recommended to use appropriate welding techniques وت post-weld heat treatments when working with this material in critical applications.
Is CF3 Suitable for Cryogenic Applications?
بله, 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. هر چند, 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 مولیبدن.
در محیط های دریایی with high salinity, CF3 may experience some خوردگی با گذشت زمان, so CF3M or CF8M might be more suitable.
How should CF3 Stainless Steel be maintained?
Regular maintenance of CF3 stainless steel includes:
- نظافت: Removing contaminants such as chlorine, نمک, and chemicals that could cause localized corrosion.
- بازرسی: Checking for any signs of گودال یا خوردگی, مخصوصاً در دریایی یا chemical environments.
- جوش: Ensuring proper پس از خوب عملیات حرارتی to avoid cracking or sensitization.
Can CF3 Stainless Steel be used in food contact applications?
بله, CF3 is often used in تجهیزات پردازش مواد غذایی به دلیل آن مقاومت در برابر خوردگی وت ease of cleaning.
It complies with FDA وت 3-A Sanitary Standards, آن را به یک انتخاب مناسب برای بهداشتی دریچه, پمپ, و سیستم های لوله کشی.
