Stainless steel is the backbone of modern industry – but not all grades are created equal. As Huaxiao-Alloy, a global supplier of precision stainless steel and specialty metals, we decode the 4 fundamental types of stainless steel, their properties, and why choosing the right type matters for your project.
The 4 Types of Stainless Steel: Metallurgy & Applications
Stainless steels are classified by their microstructure, determined by alloying elements like chromium (Cr), nickel (Ni), and molybdenum (Mo). Here’s how they compare:
| Type | Key Alloys | Structure | Corrosion Resistance | Strength | Huaxiao Stock Grades |
|---|---|---|---|---|---|
| Austenitic (Type 1) | 16–26% Cr, 6–22% Ni, +Mo/Mn | FCC (non-magnetic) | ⭐⭐⭐⭐⭐ (Best) | Moderate (200–600 MPa) | 304, 316L, 321, 310S |
| Ferritic (Type 2) | 10–30% Cr, <0.1% C, low Ni | BCC (magnetic) | ⭐⭐ (Good, except chlorides) | Low–Moderate (300–500 MPa) | 430, 409, 439, 444 |
| Martensitic (Type 3) | 12–18% Cr, 0.1–1.2% C, low Ni | Body-Centered Tetragonal | ⭐ (Moderate) | High (up to 1900 MPa) | 410, 420, 440C, 17-4PH |
| Duplex (Type 4) | 19–28% Cr, 4–7% Ni, 2–3% Mo | Mixed Austenite/Ferrite | ⭐⭐⭐⭐ (Excellent) | Very High (600–1000 MPa) | 2205, 2507, Zeron 100 |
Core Metallurgy Explained:
- Chromium (Cr): Forms passive oxide layer (>10.5% required for “stainless” property).
- Nickel (Ni): Stabilizes austenite (Type 1), improves ductility.
- Molybdenum (Mo): Boosts chloride resistance (critical for 316L/duplex).
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Huaxiao-Alloy Stainless Steel Specifications
We supply all 4 types in custom sizes per ASTM/EN/JIS standards:
Standard Dimensions & Forms
| Product Form | Austenitic (304/316) | Ferritic (430) | Martensitic (410) | Duplex (2205) |
|---|---|---|---|---|
| Sheets/Plates | 0.3mm–100mm (Thick) | 0.5mm–50mm | 1mm–50mm | 2mm–80mm |
| Coils | 0.3–6mm (Thick), ≤2000mm (W) | 0.5–6mm, ≤1800mm (W) | 1–6mm, ≤1500mm (W) | 2–10mm, ≤1800mm (W) |
| Bars/Rods | Ø6–500mm | Ø10–300mm | Ø10–250mm | Ø20–300mm |
| Tubes/Pipes | OD: 10–1000mm, WT: 1–50mm | OD: 15–600mm, WT: 1–20mm | OD: 10–300mm, WT: 1–25mm | OD: 20–500mm, WT: 2–40mm |
(Surface finishes: 2B, BA, No.4, HL, Mirror | Tolerance: EN 10029/ISO 9445)
Stainless Steel vs. Carbon Steel & Aluminum: When to Choose What
| Property | Stainless Steel | Carbon Steel | Aluminum |
|---|---|---|---|
| Corrosion Res. | ⭐⭐⭐⭐⭐ (Passive layer) | ⭐ (Rusts easily) | ⭐⭐⭐ (Anodized improves) |
| Strength | Moderate–High (200–1900 MPa) | High (400–1500 MPa) | Low–Moderate (70–550 MPa) |
| Weight | Heavy (7.9 g/cm³) | Heavy (7.8 g/cm³) | Light (2.7 g/cm³) |
| Cost | $$$ | $ | $$ |
| Max Temp | 870°C (316) | 540°C (loses strength) | 400°C (softens) |
| Best For | Chemical tanks, surgical tools | Structural beams, machinery | Aircraft, heat sinks |
Key Takeaway:
- Stainless wins for corrosion/heat resistance.
- Carbon steel dominates structural budgets.
- Aluminum excels where weight savings trump strength.
Real-World Applications by Stainless Type
1. Austenitic (Type 1) – 70% of Global Use
- Huaxiao Grades: 304 (18/8), 316L (Mo-added), 310S (high-temp)
- Why: Formability, weldability, hygiene.
- Uses:
- Food Processing: 316L tanks (largest stainless steel pan manufacturers use this)
- Architecture: 304 cladding (Burj Khalifa)
- Medical: Implants (ISO 5832-1 certified)
2. Ferritic (Type 2) – Cost-Effective Alternative
- Huaxiao Grades: 430 (appliances), 444 (Mo-enhanced)
- Why: Magnetic, affordable, decent corrosion resistance.
- Uses:
- Automotive: Exhaust systems (409)
- Household: Refrigerator panels (430)
3. Martensitic (Type 3) – Extreme Strength
- Huaxiao Grades: 420 (cutlery), 440C (bearings), 17-4PH (aerospace)
- Why: Heat-treatable to high hardness.
- Uses:
- Tools: Surgical scalpels (420)
- Aerospace: Landing gear components (17-4PH)
4. Duplex (Type 4) – The Future of Corrosion Resistance
- Huaxiao Grades: 2205 (standard), 2507 (super duplex)
- Why: 2x strength of 316L, chloride resistance.
- Uses:
- Offshore: Subsea pipelines (corrosion resistant steel for seawater)
- Desalination: RO membranes (2507)
Why Choose Huaxiao Alloy?
We solve corrosion and strength challenges with:
- Precision Alloy Control: Low S/P (<0.015%) for weld integrity.
- Thermo-Mechanical Processing: Enhanced duplex strength via cold rolling.
- Certified Traceability: EN 10204 3.2 certificates with PMI testing.
- Value-Added Services: Laser/waterjet cutting, annealing, pickling.
Primarily chromium (>10.5%) forming a self-healing Cr₂O₃ layer. Nickel/molybdenum boost corrosion resistance (stainless steel made of what metal).
Harry Brearley (1913) discovered martensitic SS while seeking erosion-resistant gun barrels (stainless steel invention).
An alloy – a solid solution of iron, chromium, carbon, etc. (stainless steel is a compound? No).
Duplex (e.g., 2205) offers 2X yield strength and superior chloride resistance at similar cost.
Yes, if passive layer is damaged (e.g., chloride pitting on 304 in seawater) or contaminated (carbon steel contact).
The Petronas Towers (KL) used 65,000 tons of Type 316 stainless steel cladding (largest stainless steel projects).
Ferritic and martensitic types are magnetic. Austenitic (304/316) is non-magnetic unless cold-worked.
We enforce:
- Melt practice: AOD/VOD refining for low inclusions.
- Testing: PMI, tensile, intergranular corrosion (ASTM A262).
Partner with Huaxiao-Alloy for Precision Stainless Solutions
From austenitic food-grade tubing to super duplex pressure vessels, Huaxiao-Alloy delivers certified stainless steel tailored to your specs. We stock:
- All 4 Types: 304, 430, 17-4PH, 2205 ready for cutting/fabrication.
- Global Standards: ASTM, EN, JIS, GB, ISO.
- Sustainable Focus: 80%+ recycled content.
Request a Quote for mill-direct stainless steel sheets, bars, or tubes – engineered for your critical environment.
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