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ISO X30Cr13 Stainless Steel: Martensitic Grade for Hardness, Wear Resistance & Moderate Corrosion Applications
ISO X30Cr13 (AISI 420, UNS S42000) is a martensitic stainless steel grade characterized by its high carbon content (0.26-0.35%) and 12-14% chromium, delivering exceptional hardness (up to 50 HRC after heat treatment) and wear resistance. This grade is widely utilized in applications requiring a balance of mechanical strength, moderate corrosion resistance, and cost-effectiveness, such as cutlery, surgical instruments, and industrial valves. Below is a detailed breakdown of its metallurgical properties, processing methods, and industrial applications.
1. Chemical Composition (ISO 683-17 / EN 10088-3)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | 0.26 – 0.35% | Enhances hardness and strength via martensite formation; higher carbon improves wear resistance but reduces toughness |
| Chromium (Cr) | 12.00 – 14.00% | Provides corrosion resistance via passive Cr₂O₃ film; stabilizes ferrite phase at high temperatures |
| Manganese (Mn) | ≤ 1.00% | Deoxidizes molten steel; improves hot workability and sulfur tolerance |
| Silicon (Si) | ≤ 1.00% | Enhances oxidation resistance; acts as a deoxidizer during smelting |
| Phosphorus (P) | ≤ 0.040% | Impurity; minimized to prevent embrittlement and reduce corrosion susceptibility |
| Sulfur (S) | ≤ 0.030% | Impurity; controlled to avoid hot shortness and improve machinability in resulfurized variants |
| Nickel (Ni) | ≤ 0.75% | Residual element; limited to maintain martensitic structure (no austenite stabilization) |
2. Mechanical Properties (After Heat Treatment)
| Condition | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HRC) | Impact Toughness (J) |
|---|---|---|---|---|---|
| Annealed (+A) | ≤ 700 | ≤ 450 | ≥ 12 | ≤ 25 | ≥ 20 |
| Quenched & Tempered (+QT) | 700 – 900 | 500 – 700 | ≥ 8 | 45 – 50 | ≥ 15 |
Note: Properties vary with tempering temperature (200-400°C for optimal balance of hardness and toughness).
3. Heat Treatment Process
- Annealing: Heat to 750-850°C, slow furnace cooling to ≤ 600°C (20°C/h) to soften for machining (max 25 HRC).
- Hardening (Quenching): Austenitize at 980-1050°C, oil or air quench to achieve martensite transformation (50-55 HRC as-quenched).
- Tempering: Reheat to 200-400°C (low temp for cutting tools) or 500-700°C (high temp for structural parts) to relieve stresses and adjust hardness.
- Stress Relieving: Optional post-weld treatment at 600-700°C to minimize distortion in precision components.
4. Key Application Fields
Cutlery & Tableware
Knife blades, surgical scalpels, and scissors — hardened to 50-55 HRC for edge retention; polished to Ra ≤ 0.4 µm for hygiene.
Mechanical Components
Valves, pumps, and shafts in mild corrosive environments (e.g., water, steam); preferred for wear-resistant bushings and gears.
Medical & Dental Instruments
Surgical tools, dental probes, and orthopedic implants — biocompatible when passivated; sterilizable via autoclaving (121°C).
Industrial Equipment
Molds for plastic injection, textile machinery parts, and food-processing blades (non-acidic media); often PVD-coated for extended life.
5. Comparison with Related Grades
| Grade | Carbon (%) | Hardness (HRC) | Corrosion Resistance | Typical Use |
|---|---|---|---|---|
| X30Cr13 (420) | 0.26-0.35 | 45-50 | Moderate (atmospheric, water) | Cutlery, surgical tools, valves |
| X20Cr13 (420F) | 0.16-0.25 | 40-45 | Moderate (better machinability) | Automatic lathe components, fasteners |
| X46Cr13 (420C) | 0.43-0.50 | 52-56 | Lower (prioritizes wear resistance) | Bearings, knife blades (high-end) |
| X5CrNi18-10 (304) | ≤ 0.08 | ≤ 20 | High (austenitic) | Food processing, architectural |
6. Processing & Usage Guidelines
- Machining: Best in annealed condition (≤ 25 HRC); use carbide tools with coolant to avoid work hardening. Roughing at 50-80 m/min, finishing at 100-150 m/min.
- Welding: Preheat to 200-300°C and post-weld temper at 600-700°C to prevent cracking; use AWS E/ER410 filler metal for martensitic structure retention.
- Corrosion Limits: Avoid prolonged exposure to chlorides (e.g., seawater) or acids (pH < 4); passivate with nitric acid (20-30%) after machining to restore Cr₂O₃ film.
- Surface Finishes: Electropolishing (Ra ≤ 0.2 µm) for medical applications; bead blasting (Ra 0.8-1.6 µm) for decorative parts; PVD coating (TiN, CrN) for wear resistance.
7. Request a Quote for X30Cr13 Stainless Steel
Need ISO X30Cr13 (420) stainless steel in custom forms—sheets, bars, or precision-machined components? Contact Baoli Iron & Steel for competitive pricing, technical specifications, and lead times tailored to your project requirements.
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