CF8M is a casting stainless steel under the ASTM A351 standard, also known as ASTM A351 CF8M. It is commonly used for producing complex-shaped, large-sized castings such as valves, pump bodies, flanges, and more.
It has excellent casting properties, making it easy to shape and suitable for mass production. However, because of the casting process, its surface finish is generally not as smooth and often requires further processing to improve surface quality.
What Does CF8M Mean?
CF8M can be explained in the following parts:
- C: Represents “Casting,” which means this is a stainless steel alloy produced through casting, not forging or rolling.
- F: Indicates that this stainless steel belongs to the austenitic stainless steel series.
- 8: Refers to one of the main alloy elements—nickel. The number “8” means the nickel content is typically around 8%.
- M: Indicates the presence of molybdenum in the alloy, typically between 2% and 3%. Molybdenum improves the alloy’s corrosion resistance, especially to chloride-induced corrosion (like seawater corrosion).
So, CF8M is a cast austenitic stainless steel containing about 8% nickel and 2%–3% molybdenum.
Chemical Composition of CF8M Stainless Steel
The chemical composition of CF8M stainless steel gives it outstanding performance in harsh environments. Its typical chemical composition includes:
Element | Content Range (%) |
Chromium (Cr) | 18.0–20.0 |
Nickel (Ni) | 8.0–10.5 |
Iron (Fe) | Balance |
Carbon (C) | ≤0.08 |
Manganese (Mn) | ≤2.00 |
Silicon (Si) | ≤1.00 |
Sulfur (S) | ≤0.03 |
Phosphorus (P) | ≤0.04 |
The main elements in CF8M are chromium and nickel, which give it excellent corrosion resistance and toughness. Chromium enhances oxidation resistance, while nickel increases the material’s ductility.
Physical Properties of CF8M Stainless Steel
Property | Value (Unit) |
Density | 7.8 g/cm³ |
Elastic Modulus | 193 GPa |
Thermal Conductivity | 16 W/m·K |
Specific Heat Capacity | 500 J/kg·K |
Resistivity | 0.72 µΩ·m |
Melting Point | 1375°C – 1400°C |
Coefficient of Thermal Expansion | 16.2 x 10⁻⁶ /°C |
CF8M has a relatively high density and elastic modulus, meaning it has a certain hardness and rigidity. Its thermal conductivity and specific heat are moderate, indicating good stability during heat transfer and heat treatment.
Mechanical Properties of CF8M Stainless Steel
Property | Value (Unit) |
Tensile Strength | 520 – 700 MPa |
Yield Strength | 205 – 250 MPa |
Elongation | 40% – 50% |
Hardness | 150 – 200 HB |
Impact Toughness | 30 – 60 J (at room temperature) |
Bending Strength | 825 MPa |
CF8M has good tensile strength and yield strength, making it suitable for high-pressure and load-bearing applications. It also shows good elongation and impact toughness, especially in environments that require toughness and resistance to impact.
Advantages of CF8M Stainless Steel
Excellent Corrosion Resistance
CF8M contains 2.0%–3.0% molybdenum, giving it outstanding resistance to pitting, crevice corrosion, and chloride-induced corrosion, especially in marine, chemical, and petrochemical industries.
High Strength and Toughness
CF8M maintains good strength and toughness, even in low-temperature environments, making it suitable for applications with high loads and complex conditions.
Good Machinability
CF8M is easy to cast and machine, allowing the manufacture of complex-shaped parts with smooth surfaces after processing.
Excellent Weldability
Although it requires annealing to restore corrosion resistance after welding, CF8M has good weldability, making it suitable for parts requiring complex welded connections.
Low Carbon Content
The maximum carbon content is 0.08%, which helps improve corrosion resistance, especially by reducing carbide precipitation during welding and preventing stress corrosion cracking.
Wide Range of Applications
CF8M is used in pumps, valves, chemical reactors, marine platforms, and other equipment where corrosion resistance and strength are critical.
CF8M vs 316 Stainless Steel
CF8M is often considered the cast version of 316 stainless steel, commonly used for casting parts, especially valves, pump bodies, flanges, and chemical processing equipment. It has high chromium and molybdenum content, which provides strong corrosion resistance, particularly in chloride environments, and maintains strength at high temperatures.
316 stainless steel is used in a broader range of applications, including marine, medical, and food processing equipment, because of its excellent corrosion resistance and versatility.
- Casting vs. Forging: CF8M is commonly used for cast parts, while 316 is more suitable for forged forms, such as sheets, rods, and pipes.
- Chemical Composition: CF8M has slightly higher chromium content (18-21%), while 316 has lower chromium content (16-18%) but higher nickel (10-14%) for better ductility and toughness.
- Corrosion Resistance: Both have excellent corrosion resistance, especially in chloride-rich environments, but CF8M might perform slightly better in high chloride concentrations.
- Mechanical Properties: CF8M has higher yield strength and elongation, making it suitable for applications requiring strength and structural integrity, while 316 is better for flexible manufacturing needs.
Overall, the choice between CF8M and 316 stainless steel depends on the required processing method (casting or forging), the working environment (corrosive conditions, temperature), and performance needs (strength, toughness, corrosion resistance).
CF8M Stainless Steel Casting Process
Prepare the Mold:
CF8M casting typically uses sand casting or precision casting (lost wax casting). First, a mold is made according to the design requirements. In precision casting, a wax model is used, which is coated and reinforced to form the mold.
Alloy Composition:
CF8M is composed of elements like:
- Chromium (Cr): 16-18%.
- Nickel (Ni): 10-14%.
- Molybdenum (Mo): 2-3%, which is key to its corrosion resistance.
- Carbon (C): Less than 0.08% to prevent carbide precipitation and maintain corrosion resistance.
Melting and Pouring:
After melting the metal in a furnace, it is poured into the mold at high temperatures, ensuring even composition and good flowability.
Cooling and Mold Removal:
Once the casting cools, the mold is removed, and in precision casting, the wax model is eliminated.
Post-Processing:
The cast part may need cleaning, heat treatment (usually solution treatment between 1050-1150°C), and machining to correct surface defects or meet precise dimensions.
Inspection and Quality Control:
After casting and post-processing, CF8M parts undergo inspections like X-ray testing, magnetic particle inspection, and ultrasonic testing to ensure no defects like porosity or cracks. Chemical composition and mechanical performance are also tested to ensure conformity to CF8M standards.
Applications of CF8M Stainless Steel
CF8M’s casting features make it ideal for producing complex parts, including:
Valves and Fittings
CF8M is widely used in making various valves, flanges, and fittings. These parts often need to withstand high pressure, chemical corrosion, and high temperatures, and CF8M’s excellent mechanical and corrosion resistance properties make it ideal for the oil, gas, and chemical industries.
Pump and Compressor Parts
CF8M is suitable for manufacturing pump bodies, impellers, and compressor housings. These parts frequently come into contact with abrasive fluids and high-pressure conditions, and CF8M helps minimize wear and downtime.
Chemical and Pharmaceutical Processing
CF8M is used in parts that come into contact with corrosive materials, such as reactors, heat exchangers, and pipes. Its resistance to pitting and crevice corrosion makes it perfect for working in high-chloride environments like marine or chemical industries.
High-Temperature Applications
CF8M maintains good strength at high temperatures, making it suitable for applications in high-temperature furnaces, ovens, and other heat-resistant equipment.
Food and Beverage Processing
CF8M is used in equipment requiring high sanitation standards, such as tanks, pipelines, and food processing equipment, because it resists acidic and saline substances.
Marine and Coastal Infrastructure
CF8M is used in underwater equipment, pumps, valves, and fittings, particularly in chloride-rich seawater environments. Its excellent corrosion resistance makes it ideal for long-term exposure to harsh conditions.
Pressure Vessels and Containers
CF8M is used in manufacturing pressure vessels and chemical containers, especially in industries that deal with chemicals and corrosive materials, like marine engineering and petrochemical plants.
Aerospace and Transportation
CF8M stainless steel is used in aerospace and transportation components exposed to harsh weather and chemical corrosion, offering both strength and corrosion resistance.
How Can Manek Help
At Manek, we offer our clients a series of customized services specifically for stainless steel and other metals, including investment casting, sand casting, die casting, CNC machining, sheet metal fabrication as well as various surface treatments.
We also provide a variety of other manufacturing capabilities. You can get quotations for free, such as 3D printing, plastic injection molding and powder coating.
FAQ
CF8M and 316 are not the same. CF8M is a casting – grade stainless steel and 316 is a wrought – grade stainless steel.
On a valve, CF8M indicates that the valve is made of austenitic stainless steel with good corrosion resistance and suitable mechanical properties for valve applications.
CF8M is an austenitic stainless – steel grade, mainly used in casting applications such as valves, pump parts, and fittings due to its good corrosion resistance and mechanical properties.
