If you’re designing parts that need a tough coreE un duro, wear-resistant surface—like automotive gears, alberi industriali, or aerospace fasteners—you need a material that balances ductility and surface strength.Aisi 8620 acciaio in lega is the perfect solution: as a low-carbon nickel-chromium-molybdenum (Ni-Cr-Mo) lega, it’s ideal for carburizing (a heat treatment that hardens only the surface), delivering a hard outer layer (fino a 60 HRC) and a tough inner core. This guide breaks down its properties, Applicazioni del mondo reale, processo di produzione, and material comparisons to help you solve “tough core + hard surface” design challenges.
1. Proprietà materiali di AISI 8620 Acciaio in lega
AISI 8620’s performance comes from its low-carbon (0.18–0,23%) and Ni-Cr-Mo composition: low carbon keeps the core ductile, nickel booststenacità, chromium enhances surface hardenability, and molybdenum improvesfatigue limit. Esploriamo in dettaglio le sue proprietà chiave.
1.1 Composizione chimica
Aisi 8620 adheres to ASTM A29/A29M standards, with elements optimized for carburizing. Di seguito è la sua composizione tipica:
| Elemento | Simbolo | Gamma di contenuti (%) | Ruolo chiave |
|---|---|---|---|
| Carbonio (C) | C | 0.18 - 0.23 | Low enough to keep the core ductile; reacts with carbon during carburizing to harden the surface |
| Nichel (In) | In | 0.40 - 0.70 | Core toughness booster; maintainsLa tenacità dell'impatto at low temperatures (-30 ° C.) |
| Cromo (Cr) | Cr | 0.40 - 0.60 | Enhances surface hardenability; miglioraResistenza alla corrosione of the carburized layer |
| Molibdeno (Mo) | Mo | 0.15 - 0.25 | Raisesfatigue limit; prevents brittleness in the carburized surface |
| Manganese (Mn) | Mn | 0.70 - 0.90 | Raffina la struttura del grano; aumentaresistenza alla trazione without reducing ductility |
| Silicio (E) | E | 0.15 - 0.35 | Aids deoxidation; supports stability during carburizing |
| Fosforo (P) | P | ≤ 0.035 | Minimized to avoid brittle fracture in the carburized layer |
| Zolfo (S) | S | ≤ 0.040 | Controlled to balancemachinabilità e qualità della superficie (lower S = smoother carburized surfaces) |
| Vanadio (V) | V | ≤ 0.03 | Trace element; refines grains for uniform surface hardening |
| Rame (Cu) | Cu | ≤ 0.30 | Trace element; adds mild atmospheric corrosion resistance for outdoor parts |
1.2 Proprietà fisiche
Questi tratti rendono AISI 8620 ideal for carburized parts across industries:
- Densità: 7.85 g/cm³ (same as standard steels)—simplifies weight calculations for gears, alberi, or fasteners
- Punto di fusione: 1,420 - 1,450 ° C. (2,588 - 2,642 ° f)—compatible with carburizing and forging processes
- Conducibilità termica: 42.0 Con(M · k) A 20 ° C.; 38.0 Con(M · k) A 300 °C—ensures even carbon diffusion during carburizing (no uneven surface hardness)
- Coefficiente di espansione termica: 11.5 × 10⁻⁶/° C. (20 - 100 ° C.)—minimizes distortion during carburizing and quenching
- Proprietà magnetiche: Ferromagnetic—enables non-destructive testing (Ndt) like magnetic particle inspection to check surface cracks after carburizing.
1.3 Proprietà meccaniche
AISI 8620’s mechanical performance depends on carburizing: the surface is hard, while the core remains tough. Below are typical values for carburized and non-carburized conditions:
| Proprietà | Measurement Method | Non-Carburized (Ricotto) | Carbburato (0.8–1.0% Surface C) |
|---|---|---|---|
| Surface Hardness | HRC | 18 - 22 HRC | 58 - 60 HRC |
| Durezza principale | HRC | 18 - 22 HRC | 30 - 35 HRC |
| Resistenza alla trazione | MPA (ksi) | 600 MPA (87 ksi) | 1,100 MPA (159 ksi) |
| Forza di snervamento | MPA (ksi) | 350 MPA (51 ksi) | 800 MPA (116 ksi) |
| Allungamento | % (In 50 mm) | 28 - 32% | 12 - 15% |
| La tenacità dell'impatto | J (A -30 ° C.) | ≥ 90 J | ≥ 45 J (tenacia principale) |
| Fatigue Limit | MPA (rotating beam) | 300 MPA | 650 MPA |
1.4 Altre proprietà
AISI 8620’s traits solve “tough core + hard surface” challenges:
- Saldabilità: Excellent—low carbon allows welding without preheating (for non-carburized parts); carburized parts need grinding to remove surface carbon before welding.
- Formabilità: Great—soft in the annealed condition (18–22 HRC), so it can be bent, forged, or stamped into complex shapes (PER ESEMPIO., spazi vuoti di ingranaggi) before carburizing.
- Machinabilità: Excellent—annealed AISI 8620 cuts easily with HSS or carbide tools; carburized parts require grinding for final shaping.
- Resistenza alla corrosione: Moderate—chromium in the carburized layer resists mild rust; per ambienti difficili, add zinc plating or epoxy coating.
- Surface Wear Resistance: Outstanding—carburized surface (58–60 HRC) resists metal-to-metal wear, extending part life by 3–4x vs. non-carburized steels.
2. Applicazioni di AISI 8620 Acciaio in lega
AISI 8620’s carburizing advantage makes it ideal for parts that need to resist wear while absorbing impact. Here are its key uses:
- Marcia: Automotive transmission gears, industrial gearbox gears, and helicopter rotor gears—hard surface resists tooth wear; tough core absorbs shock from gear meshing.
- Alberi: Alberi di trasmissione, alberi a camme, and axle shafts—hard surface resists abrasion; tough core handles torque and bending.
- Cuscinetti: Bearing races and bushings—smooth, hard surface minimizes friction; tough core prevents cracking from heavy loads.
- Parti automobilistiche: Pignoni, sprockets, and clutch hubs—withstand engine heat and repeated contact; carburized surface resists wear from daily use.
- Macchinari industriali: Chain links, rulli di trasporto, and fasteners—hard surface resists dirt/abrasion; tough core handles impact from material handling.
- Componenti aerospaziali: Landing gear pins, engine accessory gears, and fasteners—carburized surface resists wear; tough core tolerates takeoff/landing stress.
3. Tecniche di produzione per AISI 8620 Acciaio in lega
Producing AISI 8620 focuses on carburizing to create a “hard surface + tough core” structure. Ecco il processo passo-passo:
- Making d'acciaio:
- Aisi 8620 is made using an Fornace ad arco elettrico (Eaf) (recycles scrap steel) O Fornace di ossigeno di base (Bof). Nichel (0.40–0,70%), cromo (0.40–0,60%), e molibdeno (0.15–0,25%) are added during melting to ensure uniform alloy distribution.
- Rotolando & Forgiatura:
- The steel is Laminato caldo (1,100 - 1,200 ° C.) into bars, piatti, or tubes—hot rolling makes it easy to form. Per parti complesse (PER ESEMPIO., spazi vuoti di ingranaggi), suo Hot Forged to shape, then annealed to soften (18–22 HRC) per la lavorazione.
- Lavorazione:
- Aisi ricotto 8620 is machined into near-final shapes (PER ESEMPIO., gear teeth blanks) using turning, fresatura, or drilling. HSS tools work well for most cuts; carbide tools are used for tight tolerances.
- Carburazione (Passo critico):
- Gas Carburizing: Parts are heated to 880–920 °C in a carbon-rich gas (PER ESEMPIO., methane) for 4–12 hours (longer = thicker hard layer). Il carbonio si diffonde nella superficie (0.8–1,0% c), while the core remains low-carbon (0.18–0.23% C).
- Spegnimento: Dopo il carburi, parts are cooled to 830–850 °C, held briefly, poi spento in olio. This hardens the surface to 58–60 HRC and the core to 30–35 HRC.
- Tempra: Parts are reheated to 180–220 °C for 1–2 hours, then air-cooled. This reduces surface brittleness without lowering hardness.
- Trattamento superficiale:
- Macinazione: Carburized parts are ground to smooth the surface (removes oxidation) and achieve final tolerances (PER ESEMPIO., gear tooth precision).
- Placcatura: Zinco (Resistenza alla ruggine) for outdoor parts; placcatura cromata (extra wear resistance) for high-friction parts.
- Scatto: Optional—blasts the surface with small metal balls to reduce residual stress and boost fatigue limit.
- Controllo di qualità:
- Analisi chimica: Spectrometry verifies nickel, cromo, e livelli di molibdeno (per ASTM A29/A29M).
- Hardness Testing: Rockwell testing checks surface (58–60 HRC) and core (30–35 HRC) durezza.
- Microstructural Analysis: Optical microscopy confirms a uniform carburized layer (no gaps or uneven carbon distribution).
- Ndt: Controlli di test ad ultrasuoni per difetti interni; magnetic particle inspection finds surface cracks from carburizing.
4. Casi studio: Aisi 8620 in azione
Real projects show how AISI 8620 solves “wear + impact” challenges.
Caso di studio 1: Automotive Transmission Gears (Germania)
A car manufacturer needed transmission gears that could resist tooth wear and absorb shift shock. They switched from AISI 1045 carbon steel to carburized AISI 8620 marcia. The AISI 8620 gears lasted 200,000 km—double the lifespan of 1045 gears—because the carburized surface (59 HRC) prevented tooth pitting, and the tough core (32 HRC) absorbed shift impact. This reduced warranty claims by 40%.
Caso di studio 2: Industrial Conveyor Shafts (NOI.)
A warehouse had to replace conveyor shafts every 2 years due to surface wear and bending cracks. They used AISI 8620 alberi, carburized to 58 HRC and shot-peened. The new shafts lasted 5 years—no wear or cracks—because the hard surface resisted abrasion from dirt, and the tough core handled conveyor loads. This saved the warehouse $35,000 in costi di sostituzione.
5. Aisi 8620 vs. Altri materiali
Come fa Aisi 8620 compare to other carburizable and wear-resistant steels?
| Materiale | Similarities to AISI 8620 | Differenze chiave | Meglio per |
|---|---|---|---|
| Aisi 4140 | Cr-Mo alloy steel | Carbonio più alto (0.38–0.43%); not ideal for carburizing (core too hard); 15% più economico | Non-carburized, medium-wear parts |
| Aisi 8630 | Ni-Cr-Mo alloy steel | Carbonio più alto (0.28–0,33%); harder core after carburizing; 10% pricier | Heavy-load carburized parts (PER ESEMPIO., truck gears) |
| Aisi 1018 | Acciaio a basso contenuto di carbonio | No alloying; poor carburized surface strength; 30% più economico | Low-wear, low-load carburized parts |
| 52100 Acciaio cuscinetto | Acciaio ad alto contenuto di carbonio | Better wear resistance; Nessun nichel (poor toughness); 20% pricier | Precision bearings (no impact) |
| Acciaio inossidabile 410 | Resistente alla corrosione | Carburizable; better rust resistance; 3× pricier | Wet-environment carburized parts |
La prospettiva della tecnologia Yigu su AISI 8620 Acciaio in lega
Alla tecnologia Yigu, Aisi 8620 is our top pick for carburized “tough core + hard surface” parts. Its low-carbon Ni-Cr-Mo composition solves the biggest pain point for clients: getting wear resistance without sacrificing impact toughness—critical for gears, alberi, and fasteners. We supply AISI 8620 in bar, forged blanks, or machined components, with custom carburizing (0.5–1.2 mm layer thickness) and shot peening. For clients moving from plain carbon steel, Aisi 8620 delivers 3–4x longer part life at a small cost premium—saving money on maintenance and downtime.
FAQ su AISI 8620 Acciaio in lega
- How thick is the carburized layer on AISI 8620?
Typical layers are 0.5–1.2 mm thick—adjusted by carburizing time (4 hours = ~0.5 mm; 12 hours = ~1.2 mm). For parts like gears, a 0.8–1.0 mm layer balances wear resistance and flexibility; for shafts, 0.5–0.7 mm avoids surface cracking. - Può Aisi 8620 be used without carburizing?
Yes—but it’s not ideal. Non-carburized AISI 8620 has low strength (600 MPa tensile) e resistenza all'usura, so it’s only used for low-load parts (PER ESEMPIO., parentesi). Carburizing unlocks its full potential for wear and impact. - È Aisi 8620 suitable for low-temperature applications?
Yes—its nickel content maintains La tenacità dell'impatto A -30 ° C. (even after carburizing). For temperatures below -30 ° C. (PER ESEMPIO., arctic machinery), choose AISI 8640 (higher nickel) for extra low-temperature toughness.
