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Stainless Steel
Material Type
Metal
Process Compatibility
Metal Stamping, CNC Machining
Physical Properties
Property |
Value/Description |
|---|---|
| Density | 7.7-8.0 g/cm³ (Heavier than aluminum but offers superior pressure resistance) |
| Melting Point | 1400-1450°C (Excellent high-temperature stability) |
| Thermal Conductivity | 15-30 W/(m·K) (Lower than aluminum; requires optimized cooling design) |
| Thermal Expansion Coefficient | 16-18 ×10⁻⁶/°C (Similar to carbon steel; provides dimensional stability) |
| Magnetism | Austenitic (e.g., 304) non-magnetic; Martensitic (e.g., 440C) magnetic |
Mechanical Properties
Property |
Value/Description |
|---|---|
| Tensile Strength | Austenitic (304): 500-700 MPa; Martensitic (440C): Up to 1900 MPa |
| Yield Strength | 304: ≥200 MPa; 440C: ≥450 MPa (heat-treatable) |
| Hardness | 304: 70-90 HRB; 440C (quenched): 55-60 HRC |
| Ductility | Austenitic steels: ≥40% elongation (ideal for deep drawing) |
| Fatigue Strength | 304: ≈240 MPa (surface polishing improves performance) |
Chemical Properties
Property |
Description |
|---|---|
| Corrosion Resistance | Chromium ≥10.5% forms passive layer (resists acids/alkalis/salt spray) |
| Oxidation Resistance | Stable at high temps (limit: 870°C-1100°C) |
| Alloying Elements | Cr, Ni, Mo (e.g., 316 with Mo enhances corrosion resistance) |
Machinability (Key for Mold Making)
Property |
Description |
|---|---|
| Machinability | Austenitic steels work-harden (require low speed/high feed) |
| Weldability | Austenitic (304) easily weldable; Martensitic requires preheat |
| Polishing | Capable of mirror finish (common for mold cavities) |
| Heat Treatment | Martensitic steels (e.g., 440C) can be quenched to 60 HRC |
Mold Industry Applications
Advantages:
- Exceptional wear resistance and long service life
- Ideal for high-precision/high-gloss mold surfaces
- Corrosion-resistant with minimal maintenance
Limitations:
- High material cost (especially high-Ni alloys like 316)
- Challenging machining (requires specialized tooling)
Recommended Stainless Steel
Grade |
Characteristics |
Mold Applications |
|---|---|---|
| 304 | General-purpose, excellent corrosion resistance | Plastic molds, food-grade molds |
| 316 | Mo-added for acid/alkali resistance | Chemical/medical molds |
| 420 | Martensitic, heat-treatable | Cutting inserts, wear-resistant components |
| 17-4PH | Precipitation-hardening, high strength | Aerospace precision molds |
Other Metal Material Selection
Aluminum Materials
Copper Materials
Carbon Steel
Special Alloy
FAQ Of Stainless Steel
Visit our FAQ center for more questions.
Why does Stainless Steel rust?
Stainless steel is not entirely rust-proof. Its corrosion resistance relies on a chromium oxide layer (Cr₂O₃). Exposure to chlorides (e.g., seawater), mechanical damage, or high temperatures can compromise this layer, causing localized rust (e.g., pitting). Selecting appropriate grades (e.g., 316 with Mo) enhances resistance.
How to distinguish food-grade from industrial-grade Stainless Steel?
Food-grade stainless steel (e.g., 304, 316) must meet heavy metal migration limits (e.g., Pb, Cd) and undergo pickling/passivation for surface cleanliness. Industrial-grade (e.g., 430) may contain higher S/P, suitable only for non-contact uses. Certifications include GB 4806.9 (CN) and FDA (US).
Why do Stainless Steel Molds require surface treatment?
Despite inherent corrosion resistance, molds face wear (e.g., from plastic flow) and sticking issues. Surface treatments (e.g., nitriding, hard chrome plating, or PVD coating) can increase hardness from 30HRC to 70HRC+, extending service life by 5-10x.