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Stainless Steel Materials for Valves
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Stainless Steel Materials for Valves – Casting (CF Series) and Forging (F Series)
This technical summary covers the most commonly used stainless steel grades for valve components, classified by manufacturing process (casting vs. forging) and by chemical composition. All casting grades are referenced to ASTM A351, and all forging grades to ASTM A182 – the two primary standards for pressure-containing parts in the valve industry.
1. Cast Stainless Steels (CF Series) – for Valve Bodies, Pumps, and Fittings
Cast stainless steels per ASTM A351 are used for complex-shaped castings such as valve bodies, pump casings, and pipe fittings. The grade designation letters have the following meanings:
- C
= Corrosion-resistant
- F
= Chromium-nickel austenitic stainless steel
- Number
(3 or 8) = Carbon content level (3 = low carbon, 8 = standard carbon)
- M
= Contains molybdenum
1.1 CF3 – Low-Carbon Version of 304 Cast Stainless Steel
- Equivalent Chinese GB grade:
022Cr19Ni10 (casting version of 304L)
- Carbon content:
≤ 0.03 %
- Low-carbon austenitic stainless steel with excellent resistance to intergranular corrosion; no post-weld heat treatment required.
- Typical applications:
- Food & beverage: brewing equipment, dairy pipelines (corrosion-resistant and hygienic)
- Chemical & light industry: reactors and valves handling dilute nitric acid and organic acids (low carbon reduces intergranular corrosion risk)
1.2 CF8 – Standard Version of 304 Cast Stainless Steel
- Equivalent Chinese GB grade:
06Cr19Ni10 (casting version of 304)
- Carbon content:
≤ 0.08 %
- Classic austenitic stainless steel with good general corrosion resistance and resistance to high temperatures (up to 800 °C)
- Typical applications:
- High-temperature service: heat exchangers, boiler fittings (up to 800 °C)
- General corrosion resistance: water treatment equipment, piping for non-strongly corrosive media in fertiliser production
1.3 CF3M – Low-Carbon Version of 316 Cast Stainless Steel (with Molybdenum)
- Equivalent Chinese GB grade:
022Cr19Ni11Mo2 (casting version of 316L)
- Carbon content:
≤ 0.03 %
- Molybdenum content:
2.0 – 3.0 %
- Low carbon + molybdenum provides outstanding resistance to chloride-induced pitting and crevice corrosion (e.g. seawater, salt solutions)
- Typical applications:
- Marine engineering: ship fittings, seawater desalination equipment (resistance to chloride attack)
- Chemical corrosion protection: acidic media containing sulphates and chlorides (e.g. sulphuric acid, hydrochloric acid environments)
1.4 CF8M – Standard Version of 316 Cast Stainless Steel (with Molybdenum)
- Equivalent Chinese GB grade:
06Cr19Ni11Mo2 (casting version of 316)
- Carbon content:
≤ 0.08 %
- Molybdenum content:
2.0 – 3.0 %
- Molybdenum-bearing grade with corrosion resistance superior to CF8, suitable for moderately corrosive media (e.g. acetic acid, phosphoric acid)
- Typical applications:
- Pharmaceutical equipment: reactors in contact with antibiotics and organic acids (molybdenum enhances corrosion resistance)
- Petrochemical: piping and valves for medium-concentration acetic acid and phosphoric acid
Chemical Composition Comparison – Cast Stainless Steels (CF Series, commonly used for valves)
Grade | C (%) | Mn (%) | Si (%) | P (%) | S (%) | Ni (%) | Cr (%) | Mo (%) |
CF3 | ≤ 0.03 | ≤ 1.50 | ≤ 2.00 | ≤ 0.04 | ≤ 0.04 | 8.0 – 12.0 | 17.0 – 21.0 | — |
CF8 | ≤ 0.08 | ≤ 1.50 | ≤ 2.00 | ≤ 0.04 | ≤ 0.04 | 8.0 – 11.0 | 18.0 – 21.0 | — |
CF3M | ≤ 0.03 | ≤ 1.50 | ≤ 1.50 | ≤ 0.04 | ≤ 0.04 | 9.0 – 13.0 | 17.0 – 21.0 | 2.00 – 3.00 |
CF8M | ≤ 0.08 | ≤ 1.50 | ≤ 1.50 | ≤ 0.04 | ≤ 0.04 | 9.0 – 12.0 | 18.0 – 21.0 | 2.00 – 3.00 |
Note: CF3 and CF3M are low-carbon cast grades offering better corrosion resistance than their standard-carbon counterparts. "—" indicates no intentional molybdenum addition.
2. Forged Stainless Steels (F Series) – for Flanges, Fittings, and Stems
Forged stainless steel grades per ASTM A182 are used for components that must withstand higher pressures or mechanical stresses, such as flanges, pipe fittings, and valve stems. Forging produces a denser, more uniform structure with mechanical properties superior to castings.
2.1 F304 – Standard Version of 304 Forged Stainless Steel
- Equivalent Chinese GB grade:
06Cr19Ni10 (forged version of 304)
- Carbon content:
≤ 0.08 %
- Austenitic stainless steel with balanced overall performance, good corrosion resistance and workability
- Typical applications:
- Daily life: tableware, kitchen utensils (common in thermos cups, cookware)
- Architectural decoration: railings, curtain walls (atmospheric corrosion resistance, easy to form)
- Food machinery: biscuit moulds, beverage filling equipment (meets food-grade standards)
2.2 F316 – Standard Version of 316 Forged Stainless Steel (with Molybdenum)
- Equivalent Chinese GB grade:
06Cr17Ni12Mo2 (forged version of 316)
- Carbon content:
≤ 0.08 %
- Molybdenum content:
2.0 – 3.0 %
- Molybdenum-bearing grade with corrosion resistance superior to F304, especially against pitting and crevice corrosion
- Typical applications:
- Medical field: surgical instruments, implants (resistant to body fluids – 316L more common)
- Industrial environments: dyeing and papermaking equipment (resistant to sulphides and halides)
2.3 F304L – Low-Carbon Version of 304 Forged Stainless Steel
- Equivalent Chinese GB grade:
022Cr19Ni10 (forged version of 304L)
- Carbon content:
≤ 0.03 %
- Low-carbon version of 304 with improved resistance to intergranular corrosion after welding
- Typical applications:
- Welded structures: large storage tanks, pressure piping (low carbon reduces risk of weld cracking)
- Chemical vessels: reactors and heat exchangers requiring frequent welding
2.4 F316L – Low-Carbon Version of 316 Forged Stainless Steel (with Molybdenum)
- Equivalent Chinese GB grade:
022Cr17Ni12Mo2 (forged version of 316L)
- Carbon content:
≤ 0.03 %
- Molybdenum content:
2.0 – 3.0 %
- Low carbon + molybdenum offers superior corrosion resistance and weldability
- Typical applications:
- Severe corrosive environments: offshore platforms, salt-spray exposure (resistant to seawater and chloride attack)
- Pharmaceutical / food: high-purity piping (e.g. injection production lines – low carbon facilitates cleaning and sanitisation)
Chemical Composition Comparison – Forged / Bar Stock (F Series)
Element | F304 | F304L | F316 | F316L |
C | ≤ 0.08 % | ≤ 0.03 % | ≤ 0.08 % | ≤ 0.03 % |
Si | ≤ 1.0 % | ≤ 1.0 % | ≤ 1.0 % | ≤ 1.0 % |
Mn | ≤ 2.0 % | ≤ 2.0 % | ≤ 2.0 % | ≤ 2.0 % |
P | ≤ 0.045 % | ≤ 0.035 % | ≤ 0.045 % | ≤ 0.035 % |
S | ≤ 0.03 % | ≤ 0.01 % | ≤ 0.03 % | ≤ 0.01 % |
Cr | 18.0 – 20.0 % | 18.0 – 20.0 % | 16.0 – 18.0 % | 16.0 – 18.0 % |
Ni | 8.0 – 11.0 % | 8.0 – 11.0 % | 12.0 – 15.0 % | 12.0 – 15.0 % |
Note: F304 and F316 are standard-grade austenitic stainless steels; F304L and F316L are low-carbon grades with better intergranular corrosion resistance.
3. Quick Selection Reference Table
Grade | Process | Carbon Content | Mo-containing | Intergranular Corrosion Resistance | Chloride Pitting Resistance | Typical Applications |
CF3 | Casting | ≤ 0.03 % | No | Good | Weak | Food equipment, dilute acid valves |
CF8 | Casting | ≤ 0.08 % | No | Medium | Weak | Heat exchangers, water treatment |
CF3M | Casting | ≤ 0.03 % | Yes | Strong | Strong | Seawater desalination, offshore platforms |
CF8M | Casting | ≤ 0.08 % | Yes | Medium | Strong | Pharmaceutical, acetic acid piping |
F304 | Forging | ≤ 0.08 % | No | Medium | Weak | Kitchenware, architectural trim |
F316 | Forging | ≤ 0.08 % | Yes | Medium | Strong | Papermaking equipment, dye industry |
F304L | Forging | ≤ 0.03 % | No | Strong | Weak | Large welded storage tanks, pressure piping |
F316L | Forging | ≤ 0.03 % | Yes | Strong | Strong | Offshore platforms, pharmaceutical piping |
4. Key Summary – Core Differences
Casting (CF Series) vs. Forging (F Series)
- Casting:
Suitable for complex-shaped parts (valve bodies, pump casings). Generally more cost-effective.
- Forging:
Denser, more uniform grain structure, superior mechanical properties. Preferred for high-pressure and high-strength applications (flanges, fittings, stems).
Effect of Carbon Content (with "L" vs. without "L")
- "L" grades
(e.g. CF3, F304L) have low carbon (≤ 0.03 %). They are less susceptible to intergranular corrosion after welding, making them ideal for structures that require extensive welding.
- 2.0 – 3.0 %
(e.g. CF8, F304) have carbon ≤ 0.08 %, offering slightly higher strength. However, after welding they generally require solution annealing to prevent sensitisation.
Role of Molybdenum (with "M" vs. without "M")
- Molybdenum-bearing grades
(CF3M, CF8M, F316, F316L) provide significantly improved resistance to chloride-induced pitting and crevice corrosion. These are preferred for marine, saline, and acidic media environments.
- Non-molybdenum grades
are suitable for neutral or mildly corrosive environments such as fresh water, dilute acids, and caustic solutions.
Quick Selection Guideline (Memory Aid)
- General water, air, oil
→ Choose CF8 or F304
- Heavy welding and intergranular corrosion concern
→ Choose CF3 or F304L
- Seawater, brine, chlorides
→ Choose CF3M or F316L
- Strong acids, moderate corrosives
→ Choose CF8M or F316
- High pressure / high strength
→ Prefer forging series (F-grades)
This summary is intended as a practical reference for valve engineers, procurement specialists, and quality control personnel dealing with stainless steel castings and forgings under ASTM standards.
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