1. Увођење
CF3 stainless steel, a member of the austenitic cast stainless steel family, is the low-carbon cast equivalent of the popular wrought grade 304Л (УС С30403).
It is defined under ASTM A351 and widely used in industries where corrosion resistance, завабилност, and castability are paramount.
Тхе “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%).
Историјски, 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, перформансе, and resistance to sensitization,
CF3 continues to be strategically important in cast stainless steel applications across chemical, петрохемијски, пречишћавање воде, and food-processing sectors.
2. Хемијски састав & Металургија
Номинални хемијски састав
The typical weight percentage (вт.%) of the alloying elements in CF3 stainless steel, as defined by ASTM A351, јесте:
| Елемент | Типичан распон (вт.%) | Функција |
|---|---|---|
| Хром (ЦР) | 18.0 - 21.0% | Promotes corrosion resistance through passive film formation |
| Никл (У) | 8.0 - 11.0% | Стабилизира аустенит, improves ductility and toughness |
| Угљеник (Ц) | ≤ 0.03% | Reduces sensitization; improves weldability |
| Манган (Мн) | ≤ 1.5% | Enhances hot workability; deoxidizer |
| Силицијум (И) | ≤ 2.0% | Промовише флуидност у ливење; deoxidizer |
| Фосфор (П) | ≤ 0.04% | Residual; must be minimized to reduce brittleness |
| Сумпорни (С) | ≤ 0.04% | Residual; excessive S can reduce toughness |
| Iron (Фе) | Равнотежа | Matrix element |
Тхе Садржај ниског угљеника (≤ 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.
Микроструктура: Аустенитна матрица & Carbide Control
CF3 stainless steel has a fully austenitic microstructure with a face-centered cubic (ФЦЦ) lattice, which contributes to:
- Excellent toughness at both ambient and cryogenic temperatures.
- Non-magnetic behavior in the annealed state.
- Resistance to stress corrosion cracking (СЦЦ) 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 (обично < 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
| Стандардни | Означавање | Регион | Equivalent Grade |
|---|---|---|---|
| АСТМ А351 | Grade CF3 | САД | Low-carbon cast 304L |
| ASME SA-351 | Grade CF3 | САД (boiler code) | Pressure vessel compliant |
| У 10283 | ГКС2ЦРНИ19-11 | European Union | Ливена верзија 1.4306 (304Л) |
| ИСО 11972 | G-X2CrNi19-11 | Међународни | Global harmonized equivalent |
| Он Г5121 | SCS13A | Јапан | 304L cast grade |
4. Механичка својства
| Механичка имовина | Типична вредност |
|---|---|
| Затезна чврстоћа | ≥485 МПА |
| Снага приноса (0.2% зборник) | ≥205 МПА |
| Издужење | ≥30% |
| Тврдоћа | 140-190 ХБ |
| Жилавост (Темп.) | > 100 J (Charpy V-Notch) |
| Fatigue Endurance Limit | 240-270 МПА (in air, углађен) |
| Отпорност на пузање | Moderate up to 870°C |
На повишеним температурама, 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. Термички & Физичка својства
| Имовина | Вредност |
|---|---|
| Густина | ~ 7.9 г / цм³ |
| Топлотна проводљивост | ~ 16 в / м · к (at 100°C) |
| Coefficient of Expansion | 17.3 μм / м · ° Ц (20–400°C) |
| Електрична отпорност | 0.72 ω · м |
| Магнетни одговор | Неагнетнички (жарозан) |
| Отпорност на оксидацију | 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.
Флудност & Температура изливања
CF3 melts between 1450 ° Ц и 1550 ° Ц, 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 (ИСО 243), enabling fill of thin‑walled sections down to 4 мм.
Међутим, excessive superheat can increase gas pickup и оксидација, so operators typically limit superheat to 50 ° Ц above liquidus.
Solidification Range & Скупљање
Са а асортиман замрзавања приближно 60–90 °C, CF3 solidifies over a broader temperature interval than simple austenitic alloys.
Сходно томе, it exhibits линеарно скупљање од 1.9–2.3 %, necessitating careful shrink‑compensation in pattern design.
Да се спречи Порозност средишње линије, engineers employ усмерено учвршћивање: placing insulated risers above hot spots and using охладити 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.
Додатно, Егзотермне рукаве on critical risers prolong feeding life without increasing overall mold volume.
Дегастирање, Deoxidation & Inoculation
To minimize gas porosity, foundries typically argon‑purge the molten CF3 before pouring.
They also add силицијум (0.3-0.6 %) и алуминијум (0.02–0.05 %) deoxidizers, which form stable oxides and reduce dissolved oxygen.
Коначно, a small rare‑earth inoculant (Нпр., 0.03–0.05 % Fe‑Ce) promotes fine, uniform δ‑ferrite and prevents microshrinkage, enhancing mechanical consistency.
Suitable Casting Methods for CF3 Stainless Steel
| Метода ливења | Типичне апликације | Предности | Разматрања |
|---|---|---|---|
| Ливење песка (Green or No-Bake) | Тела вентила, кућишта пумпе, прирубница | – Cost-effective for large parts – Flexible for varied designs |
– Rougher surface finish (Ra 6–12 μm) – Tighter control needed for porosity |
| Ливење калупа за шкољке | 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 |
| Инвестиционо ливење (Изгубљени восак) | Подметач, medical fittings, Компоненте високо прецизних | – Excellent surface finish (По < 3 μm) – High geometric complexity |
– Higher cost – Limited to small–medium parts |
| Центрифугално ливење | Чашица, прстен, pipe sections | – High density – Low porosity – Good mechanical properties in radial direction |
– Suitable only for rotationally symmetric parts |
| Вакуумско ливење | Critical components in aerospace, nuclear applications | – Reduced oxidation – Cleaner microstructure |
– Expensive – Requires specialized equipment |
| Каливо за керамику | Complex heat-resistant parts | – Excellent surface detail – Good dimensional precision |
– Longer mold preparation time – Higher cost |
Heat Treatment Practices
Након ливења, CF3 typically undergoes Решење жарења у опсегу 1040-1120 ° Ц (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 сензибилизација и chromium depletion у границама зрна, compromising corrosion resistance.
7. Отпорност на корозију
Општа корозија
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:
- Еквивалентни број отпора за копирање (Дрва): ~ 18
- Critical Pitting Temperature (CPT): ~ 20-25 ° Ц (varies with chloride level)
Пуцање корозије на стрес-корозирање (СЦЦ)
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. Измишљотина & Обрада
ЦНЦ обрада
CF3 machines comparably to wrought 304, with a machinability index of ~45 % (где 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 μм.
Заваривање
Fabricators weld CF3 using 309 или 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.
Формирање & Придружити се
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
Вентили, Пумпе, 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. Уобичајене апликације укључују:
- Кућишта компресора
- Manifolds and flowline components
- Metering valves and flanges
In up- and midstream systems, CF3 helps prevent stress-corrosion cracking (СЦЦ) и прикудан, 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, Смоотх површинска завршна обрада, and compatibility with cleaning agents (CIP/SIP). CF3 fits these requirements, чинећи га погодном:
- Sanitary valves and pipe fittings
- Mixing and metering equipment
- Dosing pumps and housings
То је austenitic microstructure, which remains stable even after repeated sterilization cycles, helps meet ФДА и 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, биофоулинг, и 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. Поређење са алтернативним материјалима
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 ЦФ3М, ЦФ8, ЦФ8М, and wrought 304 нехрђајући.
| Имовина | ЦФ3 (304Ја сам бацао) | ЦФ3М (316Ја сам бацао) | ЦФ8 (304 Лишити) | ЦФ8М (316 Лишити) | 304L Wrought |
|---|---|---|---|---|---|
| Молибден (Мо) Садржај | Не | Да | Не | Да | Не |
| Садржај угљеника | ≤ 0.03% (Низак угљеник) | ≤ 0.03% (Низак угљеник) | ≤ 0.08% | ≤ 0.08% | ≤ 0.03% (Низак угљеник) |
| Отпорност на хлориде | Умерен | Одличан | Умерен | Одличан | Умерен |
| Отпорност на питтинг (Дрва) | ~ 18 | ~ 25-27 | ~20 | ~ 25-27 | ~ 18 |
| Отпорност на корозију | Добри | Одличан | Умерен | Одличан | Добри |
| Завабилност | Одличан | Одличан | Умерен | Умерен | Одличан |
| Трошак | $$ | $$$ | $$ | $$$ | $$ |
| Снага (Затезан) | ~ 485 МПА | ~500 MPa | ~510 MPa | ~520 MPa | ~520 MPa |
| Издужење | ~ 40% | ~45% | ~45% | ~45% | ~45% |
| Обликавост | Excellent for cast parts | Excellent for cast parts | Good for cast parts | Good for cast parts | Одличан (for rolled or formed parts) |
| Апликације | Water systems, food-grade parts | Хемијски, маринац, на одбору | General industrial parts | Маринац, хемијски, на одбору | High-ductility, Танки зидни делови |
11. Закључак
Укратко, 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.
Штавише, with annual global production exceeding 50,000 tonnes and scrap rates under 6 %, CF3 delivers both economic and performance advantages.
Радујући се, 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.
Лангхе је савршен избор за ваше производне потребе ако вам је потребан квалитетан квалитет одливљивање од нехрђајућег челика.
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 отпорност на оксидацију at elevated temperatures is critical,
other grades like ЦФ8М или 316 нерђајући челик may be more appropriate due to their enhanced high-temperature properties.
Can CF3 be welded?
Да, CF3 stainless steel is highly заварив. Its low carbon content minimizes the risk of carbide formation during welding, reducing the chances of intergranular corrosion.
Међутим, it is always recommended to use appropriate welding techniques и post-weld heat treatments when working with this material in critical applications.
Is CF3 Suitable for Cryogenic Applications?
Да, 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. Међутим, 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 молибден.
У Поморска окружења with high salinity, CF3 may experience some Питтинг Цорросион временски, so CF3M or CF8M might be more suitable.
How should CF3 Stainless Steel be maintained?
Regular maintenance of CF3 stainless steel includes:
- Чишћење: Removing contaminants such as chlorine, соли, and chemicals that could cause localized corrosion.
- Инспекција: Checking for any signs of прикудан или Цревице Цорросион, посебно у маринац или chemical environments.
- Заваривање: Ensuring proper пост-заваривање топлотни третман to avoid cracking or sensitization.
Can CF3 Stainless Steel be used in food contact applications?
Да, CF3 is often used in Опрема за прераду хране због ње отпорност на корозију и ease of cleaning.
It complies with ФДА и 3-A Sanitary Standards, чинећи га погодном избором за санитарни вентили, пумпе, и цевоводи.
