CF8, CF8M, CF3, and CF3M are the core austenitic stainless steel materials for industrial valves, which directly determine the corrosion resistance life and safety level. This article will analyze their chemical composition (chromium/molybdenum/carbon content), global certification (ASTM/EN/ISO), and selection guide for harsh working conditions to help you avoid the risk of million-level leakage.
Analysis of cast stainless steel codes: What do CF8, CF8M, CF3, and CF3M stand for?
Brand naming logic: Unraveling the alphanumeric code
- The first letter “C”: Casting process identification (different from forging “AISI 304”)
- The second letter “F”: Austenitic iron-based alloy (Fe-Cr-Ni system)
- The number “8” or “3”:
- “8” → Standard carbon content (≤0.08%) → Basic corrosion resistant type
- “3” → Ultra-low carbon (≤0.03%) → Anti-intergranular corrosion type
- Suffix “M”: Added Molybdenum element → Upgraded version of chloride ion corrosion resistance
Summary in one sentence:
CF8 = Cast 304, CF8M = Cast 316, CF3 = Cast 304L, CF3M = Cast 316L
CF8 vs CF8M: Mo-free material for seawater → lifespan shortened to 1/3
CF8 vs CF3: High carbon for welding → Heat affected zone crack risk ↑80%
Equivalence relationship with forging grades (must know for purchasers)
| Casting grade | Forgings equivalent grade | International Standards | Key Differences |
| CF8 | ASTM 304 | ASTM A351 | The casting structure is coarser and the pressure resistance is ↓10% |
| CF8M | ASTM 316 | EN 1.4408 | Mo content = 2-3%, seawater resistance↑↑ |
| CF3 | ASTM 304L | JIS SCS13A | Ultra-low carbon, no need for heat treatment after welding |
| CF3M | ASTM 316L | ISO 4991 | Low carbon + Mo, excellent corrosion resistance and welding |
Comparison of core element contents (ASTM A351 standard)
Table: Chemical composition boundary values of four types of materials
| Element | CF8 | CF8M | CF3 | CF3M | Function and impact |
| Carbon (C) | ≤0.08% | ≤0.08% | ≤0.03% | ≤0.03% | ↑Carbon: Strength↑ Resistance to intergranular corrosion↓ |
| Chromium (Cr) | 18.0-21.0% | 18.0-21.0% | 17.0-21.0% | 17.0-21.0% | Core elements for resistant oxidation media |
| Nickel (Ni) | 8.0-11.0% | 9.0-12.0% | 8.0-11.0% | 9.0-13.0% | Stable austenite structure, acid resistant↑ |
| Molybdenum (Mo) | Not added | 2.0-3.0% | Not added | 2.0-3.0% | Key to pitting resistance (especially chloride ion) |
| Manganese (Mn) | ≤1.50% | ≤1.50% | ≤1.50% | ≤1.50% | Improve deoxidation efficiency and strength |
Industrial Alert:
A chemical plant mistakenly used CF8 for chlorine-containing wastewater (CF8M was not selected) → the valve body was perforated and leaked for 6 months → loss of ¥3.7 million
Authoritative comparison of chemical composition: full disclosure of the content of 4 major material elements
A quick overview of element functions (must know for decision makers)
- Carbon (C): Strength booster, but > 0.03% will cause intergranular corrosion (welding/450℃ danger zone)
- Chromium (Cr): Anti-rust armor, acid resistance collapses when <17%
- Nickel (Ni): Austenite stabilizer, <8% may cause magnetic phase transformation
- Molybdenum (Mo): Chloride ion nemesis, 2-3% is the life-saving charm in seawater conditions
- Manganese (Mn)/Silicon (Si): Casting process bodyguard (deoxidation + fluidity)
[Core] CF8/CF8M/CF3/CF3M element boundary table
| Element | CF8 | CF8M | CF3 | CF3M | Critical red line and performance impact |
| Carbon (C) | ≤0.08% | ≤0.08% | ≤0.03% | ≤0.03% | ＞0.03% → Risk of intergranular corrosion in welding area↑↑ |
| Chromium (Cr) | 18.0-21.0% | 18.0-21.0% | 17.0-21.0% | 17.0-21.0% | ＜17% → Nitric acid/acetic acid corrosion rate ×3 |
| Nickel (Ni) | 8.0-11.0% | 9.0-12.0% | 8.0-11.0% | 9.0-13.0% | ＜8% → Cold bending cracking probability↑ |
| Molybdenum (Mo) | — | 2.0-3.0% | — | 2.0-3.0% | Molybdenum-free → Seawater pitting life < 1 year |
| Manganese (Mn) | ≤1.50% | ≤1.50% | ≤1.50% | ≤1.50% | ＞2% → Impact toughness↓30% |
| Silicon (Si) | ≤2.00% | ≤1.50% | ≤2.00% | ≤1.50% | ＞1.5% → Casting porosity↑ |
Note:
- The ultra-low carbon (C≤0.03%) of CF3/CF3M is the core of its anti-welding corrosion
- The molybdenum content of CF8M/CF3M (Mo=2-3%) determines the chloride ion resistance
Golden Rules of Purchasing
| Media Type | Mandatory elements | Recommended grades | Prohibited grades |
| Dilute sulfuric acid/acetic acid | Cr≥18% | CF8/CF3 | — |
| Chloride ion solution | Mo≥2.0% | CF8M/CF3M | CF8/CF3 |
| High temperature welding pipeline | C≤0.03% | CF3/CF3M | CF8/CF8M |
| Concentrated nitric acid (＞65%) | Cr≥20% | Special high chrome steel | All CF series |
Deviations in elements will lead to accidents. Choosing appropriate stainless steel materials according to technical requirements and the environment can ensure the safe operation of pipeline lines.
In-depth analysis of performance differences: corrosion resistance/strength/weldability/temperature limits
Corrosion resistance: Chloride ions vs Acidic media
The decisive role of molybdenum (Mo) (taking seawater working conditions as an example):
| Material | Pitting Corrosion Index (PRE) | Allowable chloride ion concentration | Typical lifespan |
| CF8 | 18.5 | ≤200 ppm | 1-2 years (risk of perforation) |
| CF8M | 25.5 | ≤5000 ppm | 15+ years |
| CF3 | 18.5 | ≤200 ppm | Same as CF8 |
| CF3M | 25.5 | ≤5000 ppm | 15+ years |
Mechanical strength: High temperature vs Room temperature
The subversive effect of temperature on strength:
| Material | Room temperature tensile strength (MPa) | 538℃ strength retention rate | Critical warning temperature |
| CF8 | 485 | 58% | ≥425℃ need to be derated |
| CF8M | 485 | 55% | Same as CF8 |
| CF3 | 450 | 62% | Low carbon improves high temperature plasticity |
| CF3M | 450 | 60% | Same as CF3 |
Temperature limit: material safety boundary
| Performance Dimension | CF8/CF8M | CF3/CF3M | Breakthrough Solution |
| Low temperature limit | -196℃ | -254℃ | CF3M for Liquid Oxygen Rocket Valve |
| High temperature oxidation | 870℃ (continuous) | 870℃ (continuous) | >870℃ requires HK40 |
| Creep rupture | 425℃ | 425℃ | Inconel 625 for over-limit |
Performance summary table (five-star system)
| Material | Seawater corrosion resistance | Weldability | High temperature strength | Cost-effectiveness | Recommended scenarios |
| CF8 | ★☆☆☆☆ | ★★☆☆☆ | ★★★☆☆ | ★★★★★ | Normal temperature chlorine-free ordinary medium |
| CF8M | ★★★★★ | ★★☆☆☆ | ★★★☆☆ | ★★★☆☆ | Seawater/chlorinated process fluid |
| CF3 | ★☆☆☆☆ | ★★★★★ | ★★★★☆ | ★★★★☆ | Welding pipes (chlorine-free) |
| CF3M | ★★★★★ | ★★★★★ | ★★★★☆ | ★★★☆☆ | The all-rounder for harsh working conditions |
Global Certification and Alternative Solutions: ASTM/EN/ISO Standard Comparison
Global mainstream standard equivalent comparison table (essential for procurement verification)
| American Standard (ASTM) | European Standard (EN) | International (ISO) | Japanese Standard (JIS) | China (GB) |
| CF8 | GX5CrNi19-10 | – | SCS13 | 022Cr19Ni10 |
| CF8M | GX5CrNiMo19-11-2 | CF-8M | SCS14A | 022Cr17Ni12Mo2 |
| CF3 | GX2CrNi19-11 | – | SCS16 | 022Cr19Ni10 |
| CF3M | GX2CrNiMo19-11-2 | CF-3M | SCS16A | 022Cr17Ni12Mo2 |
An alternative to the CF series (a lifesaver for harsh working conditions)
| Failure scenarios | CF series short board | Alternative Materials | Performance Gains | Cost factor |
| Concentrated hydrochloric acid (＞20%) | All CFs failed due to corrosion | Hastelloy C276 | Corrosion resistance↑300% | ×8-10 |
| Ultra-high temperature (>800℃) | CF8 oxidation peeling | HK30 high nickel cast steel | Anti-oxidation temperature ↑ to 1150℃ | ×5 |
| Highly abrasive slurry (containing silica sand) | CF3M erosion rate＞5mm/year | Duplex Steel CD4MCu | Wear resistance ↑250% | ×3 |
| Nuclear radiation conditions | CF8M lattice distortion | Titanium stabilized 316Ti | Neutron irradiation resistance ↑10 times | ×6 |
From precise benchmarking of multiple standards from ASTM to EN/ISO, to millimeter control of ultra-low carbon and molybdenum content (CF3M: C≤0.03%/Mo≥2.0%), JH Valve defends the global compliance of each valve with 60 years of fully certified casting technology – whether it is deep-sea chloride ion corrosion, liquid hydrogen ultra-low temperature or vaccine-grade aseptic conditions, we deliver on our promise with traceable material reports (including melting furnace number/spectral analysis) and zero leakage tests under all working conditions. Choosing JH means choosing borderless security trust. Click to obtain the exclusive material certification package and make compliant valves your global pass!
