1. 소개
CF3 stainless steel, a member of the austenitic cast stainless steel family, is the low-carbon cast equivalent of the popular wrought grade 304엘 (미국 S30403).
It is defined under ASTM A351 and widely used in industries where corrosion resistance, 용접 성, and castability are paramount.
그만큼 “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%).
역사적으로, 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, 성능, and resistance to sensitization,
CF3 continues to be strategically important in cast stainless steel applications across chemical, 석유 화학, 수처리, and food-processing sectors.
2. 화학 성분 & 야금
공칭 화학 성분
The typical weight percentage (wt.%) of the alloying elements in CF3 stainless steel, as defined by ASTM A351, ~이다:
| 요소 | 일반적인 범위 (wt.%) | 기능 |
|---|---|---|
| 크롬 (Cr) | 18.0 - 21.0% | Promotes corrosion resistance through passive film formation |
| 니켈 (~ 안에) | 8.0 - 11.0% | 오스테 나이트를 안정화시킵니다, improves ductility and toughness |
| 탄소 (기음) | ≤ 0.03% | Reduces sensitization; improves weldability |
| 망간 (MN) | ≤ 1.5% | Enhances hot workability; deoxidizer |
| 규소 (그리고) | ≤ 2.0% | 주조의 유동성을 촉진합니다; deoxidizer |
| 인 (피) | ≤ 0.04% | Residual; must be minimized to reduce brittleness |
| 황 (에스) | ≤ 0.04% | Residual; excessive S can reduce toughness |
| 철 (Fe) | 균형 | Matrix element |
그만큼 저탄소 함량 (≤ 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.
미세 구조: 오스테 나이트 매트릭스 & 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 (일반적으로 < 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
| 기준 | 지정 | 지역 | Equivalent Grade |
|---|---|---|---|
| ASTM A351 | Grade CF3 | 미국 | Low-carbon cast 304L |
| ASME SA-351 | Grade CF3 | 미국 (boiler code) | Pressure vessel compliant |
| 안에 10283 | GX2CRNI19-11 | European Union | 캐스트 버전 1.4306 (304엘) |
| ISO 11972 | G-X2CrNi19-11 | 국제적인 | Global harmonized equivalent |
| 그는 G5121 | SCS13A | 일본 | 304L cast grade |
4. 기계적 특성
| 기계적 특성 | 전형적인 가치 |
|---|---|
| 인장 강도 | ≥485 MPa |
| 항복 강도 (0.2% 오프셋) | ≥205 MPa |
| 연장 | ≥30% |
| 경도 | 140–190 HB |
| 충격 강인함 (방 온도) | > 100 J (Charpy V-Notch) |
| Fatigue Endurance Limit | 240–270 MPa (in air, 우아한) |
| 크리프 저항 | Moderate up to 870°C |
고온에서, 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. 열의 & 물리적 특성
| 재산 | 값 |
|---|---|
| 밀도 | ~ 7.9 g/cm³ |
| 열전도율 | ~ 16 w/m · k (at 100°C) |
| Coefficient of Expansion | 17.3 µm/m · ° C (20–400°C) |
| 전기 저항성 | 0.72 µΩ · m |
| 자기 반응 | 비기성 (어닐링) |
| 산화 저항 | 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.
유동성 & 쏟아지는 온도
CF3 melts between 1450 ° C 및 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.
하지만, excessive superheat can increase gas pickup 그리고 산화, so operators typically limit superheat to 50 ° C above liquidus.
Solidification Range & 수축
a 동결 범위 대략 60–90 °C, CF3 solidifies over a broader temperature interval than simple austenitic alloys.
따라서, it exhibits 선형 수축 ~의 1.9–2.3 %, necessitating careful shrink‑compensation in pattern design.
방지하기 위해 중심선 다공성, engineers employ 방향성 응고: placing insulated risers above hot spots and using 오한 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.
게다가, 발열 소매 on critical risers prolong feeding life without increasing overall mold volume.
degassing, Deoxidation & Inoculation
To minimize gas porosity, foundries typically argon‑purge the molten CF3 before pouring.
They also add 규소 (0.3–0.6 %) 그리고 알류미늄 (0.02–0.05 %) deoxidizers, which form stable oxides and reduce dissolved oxygen.
마지막으로, a small rare‑earth inoculant (예를 들어, 0.03–0.05 % Fe‑Ce) promotes fine, uniform δ‑ferrite and prevents microshrinkage, enhancing mechanical consistency.
Suitable Casting Methods for CF3 Stainless Steel
| 캐스팅 방법 | 일반적인 응용 프로그램 | 장점 | 고려 사항 |
|---|---|---|---|
| 모래 주조 (Green or No-Bake) | 밸브 바디, 펌프 하우징, 플랜지 | – Cost-effective for large parts – Flexible for varied designs |
– Rougher surface finish (Ra 6–12 μm) – Tighter control needed for porosity |
| 쉘 곰팡이 주조 | 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 |
| 투자 캐스팅 (잃어버린 왁스) | 사기꾼, medical fittings, 고정밀 구성 요소 | – Excellent surface finish (라 < 3 μm) – High geometric complexity |
– Higher cost – Limited to small–medium parts |
| 원심 캐스팅 | 부싱, 반지, pipe sections | – High density – Low porosity – Good mechanical properties in radial direction |
– Suitable only for rotationally symmetric parts |
| 진공 주조 | Critical components in aerospace, nuclear applications | – Reduced oxidation – Cleaner microstructure |
– Expensive – Requires specialized equipment |
| 세라믹 곰팡이 주조 | Complex heat-resistant parts | – Excellent surface detail – Good dimensional precision |
– Longer mold preparation time – Higher cost |
Heat Treatment Practices
캐스팅 후, CF3 typically undergoes 솔루션 어닐링 범위에서 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 감작 그리고 chromium depletion 입자 경계에서, compromising corrosion resistance.
7. 부식 저항
일반적인 부식
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:
- 구덩이 저항에 해당하는 숫자 (목재): ~ 18
- Critical Pitting Temperature (CPT): ~ 20–25 ° C (varies with chloride level)
스트레스-성분 균열 (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. 제작 & 가공 가능성
CNC 가공
CF3 machines comparably to wrought 304, with a machinability index of ~45 % (어디 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.
용접
Fabricators weld CF3 using 309 또는 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.
형성 & 합류
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
밸브, 슬리퍼, 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. 일반적인 응용 프로그램에는 포함됩니다:
- 압축기 하우징
- Manifolds and flowline components
- Metering valves and flanges
In up- and midstream systems, CF3 helps prevent stress-corrosion cracking (SCC) 그리고 구덩이, 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, 부드러운 표면 마감, and compatibility with cleaning agents (CIP/SIP). CF3 fits these requirements, 적합하게 만듭니다:
- Sanitary valves and pipe fittings
- Mixing and metering equipment
- Dosing pumps and housings
그것은 austenitic microstructure, which remains stable even after repeated sterilization cycles, helps meet FDA 그리고 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, 바이오로운, 그리고 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. 대체 자료와 비교
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 스테인리스.
| 재산 | CF3 (304L 캐스트) | CF3M (316L 캐스트) | CF8 (304 깁스) | CF8M (316 깁스) | 304L Wrought |
|---|---|---|---|---|---|
| 몰리브덴 (모) 콘텐츠 | 아니요 | 예 | 아니요 | 예 | 아니요 |
| 탄소 함량 | ≤ 0.03% (저탄소) | ≤ 0.03% (저탄소) | ≤ 0.08% | ≤ 0.08% | ≤ 0.03% (저탄소) |
| 염화물 내성 | 보통의 | 훌륭한 | 보통의 | 훌륭한 | 보통의 |
| 구덩이 저항 (목재) | ~ 18 | ~ 25–27 | ~20 | ~ 25–27 | ~ 18 |
| 부식 저항 | 좋은 | 훌륭한 | 보통의 | 훌륭한 | 좋은 |
| 용접 성 | 훌륭한 | 훌륭한 | 보통의 | 보통의 | 훌륭한 |
| 비용 | $$ | $$$ | $$ | $$$ | $$ |
| 힘 (인장) | ~ 485 MPa | ~500 MPa | ~510 MPa | ~520 MPa | ~520 MPa |
| 연장 | ~ 40% | ~45% | ~45% | ~45% | ~45% |
| 형성 가능성 | Excellent for cast parts | Excellent for cast parts | Good for cast parts | Good for cast parts | 훌륭한 (for rolled or formed parts) |
| 응용 | Water systems, food-grade parts | 화학적인, 선박, 난바다 쪽으로 부는 | General industrial parts | 선박, 화학적인, 난바다 쪽으로 부는 | High-ductility, 얇은 벽 부분 |
11. 결론
요약, 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.
게다가, with annual global production exceeding 50,000 tonnes and scrap rates under 6 %, CF3 delivers both economic and performance advantages.
기대합니다, 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.
랑헤 고품질이 필요한 경우 제조 요구에 완벽한 선택입니다. 스테인레스 스틸 주물.
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 산화 저항 at elevated temperatures is critical,
other grades like CF8M 또는 316 스테인레스 스틸 may be more appropriate due to their enhanced high-temperature properties.
Can CF3 be welded?
예, CF3 stainless steel is highly 용접 가능. Its low carbon content minimizes the risk of carbide formation during welding, reducing the chances of intergranular corrosion.
하지만, it is always recommended to use appropriate welding techniques 그리고 post-weld heat treatments when working with this material in critical applications.
Is CF3 Suitable for Cryogenic Applications?
예, 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. 하지만, 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 몰리브덴.
~ 안에 해양 환경 with high salinity, CF3 may experience some 구덩이 부식 시간이 지남에 따라, so CF3M or CF8M might be more suitable.
How should CF3 Stainless Steel be maintained?
Regular maintenance of CF3 stainless steel includes:
- 청소: Removing contaminants such as chlorine, 소금, and chemicals that could cause localized corrosion.
- 점검: Checking for any signs of 구덩이 또는 틈새 부식, 특히 선박 또는 chemical environments.
- 용접: Ensuring proper 포스트 웰드 열처리 to avoid cracking or sensitization.
Can CF3 Stainless Steel be used in food contact applications?
예, CF3 is often used in 식품 가공 장비 그것 때문에 부식 저항 그리고 ease of cleaning.
It complies with FDA 그리고 3-A Sanitary Standards, 적합한 선택으로 만듭니다 위생 밸브, 슬리퍼, 그리고 배관 시스템.
