AISI 8630 Liga de aço: Propriedades, Usos & Guia de cementação para serviços pesados

If you’re designing parts that need to handle heavy loadse resist wear—like truck gears, eixos de guindastes industriais, ou componentes de equipamentos de construção - você precisa de um material que combine um núcleo mais resistente com um material rígido, durable surface.AISI 8630 liga de aço is the heavy-duty solution: como um níquel-cromo-molibdênio de médio-baixo carbono (Ni-Cr-Mo) liga, é excelente em carburação (endurecimento superficial) while offering a stronger core than lower-carbon grades like AISI 8620. Este guia detalha suas propriedades, aplicações do mundo real, processo de fabricação, and material comparisons to help you solve “heavy-load + wear” design challenges.

1. Material Properties of AISI 8630 Liga de aço

AISI 8630’s performance stems from its balanced composition: medium-low carbon (0.28–0.33%) enables effective carburizing, nickel boosts coreresistência, chromium enhances surface hardenability, and molybdenum improveslimite de fadiga for cyclic loads. Let’s explore its key properties in detail.

1.1 Composição Química

AISI 8630 follows ASTM A29/A29M standards, with elements optimized for heavy-duty carburizing. Below is its typical composition:

1.2 Propriedades Físicas

These traits make AISI 8630 ideal for heavy-duty carburized parts in harsh environments:

• Densidade: 7.85 g/cm³ (same as standard steels)—simplifies weight calculations for large parts like truck axles
• Melting Point: 1,415 – 1,445 °C (2,588 – 2,630 °F)—compatible with forging and long carburizing cycles
• Condutividade Térmica: 41.5 C/(m·K) at 20 °C; 37.5 C/(m·K) at 300 °C—ensures even carbon diffusion during carburizing (no uneven hardness)
• Coeficiente de Expansão Térmica: 11.5 × 10⁻⁶/°C (20 – 100 °C)—minimizes distortion for large parts (por exemplo, crane shafts) during heat treatment
• Propriedades Magnéticas: Ferromagnetic—enables non-destructive testing (NDT) like magnetic particle inspection to detect surface cracks from heavy use.

1.3 Propriedades Mecânicas

AISI 8630’s mechanical performance shines in carburized condition, with a hard surface and strong core. Below are typical values:

1.4 Other Properties

AISI 8630’s traits solve heavy-duty design challenges:

• Weldability: Good—low carbon allows welding (preheat to 150–200 °C for thick parts); carburized parts need surface grinding to remove carbon before welding.
• Formabilidade: Fair—soft enough in annealed condition (20–24 HRC) for forging into large shapes (por exemplo, gear blanks) but less bendable than AISI 8620.
• Usinabilidade: Good—annealed AISI 8630 cuts easily with carbide tools; carburized parts require grinding or CBN tools for final shaping.
• Resistência à corrosão: Moderate—chromium in the carburized layer resists mild rust; for construction or mining use, add epoxy coating or zinc plating.
• Load-Bearing Wear Resistance: Excellent—hard surface (58–60 HRC) resiste ao desgaste, while the stronger core (35–40 HRC vs. 30–35 HRC for 8620) handles heavy loads without bending.

2. Applications of AISI 8630 Liga de aço

AISI 8630’s “strong core + hard surface” makes it ideal for heavy-duty parts that can’t fail under load or wear. Here are its key uses:

• Automotivo (Heavy-Duty): Truck transmission gears, axle shafts, and differential housings—handles high torque (500+ N·m) and road wear.
• Construction Equipment: Excavator bucket teeth, bulldozer axle shafts, and crane hooks—absorbs impact from digging/lifting and resists dirt abrasion.
• Industrial Machinery: Steel mill gearboxes, mining conveyor shafts, and hydraulic press rams—supports loads up to 50+ tons and resists metal-on-metal wear.
• Mechanical Components: Heavy-duty bearings (for large motors), pump rotors (for thick fluids), and turbine shafts—tolerates cyclic loads and harsh operating conditions.
• Aeroespacial (Ground Support): Aircraft tow tractor gears, cargo loader components—balances strength and wear resistance for heavy ground equipment.
• Defense: Military truck axles, armored vehicle track links—tough enough for off-road use and ballistic impact.

3. Manufacturing Techniques for AISI 8630 Liga de aço

Producing AISI 8630 focuses on carburizing and forging to handle heavy loads. Here’s the step-by-step process:

1. Steelmaking:
   • AISI 8630 is made using an Electric Arc Furnace (EAF) (recycles scrap steel) ou Basic Oxygen Furnace (BOF). Níquel, cromo, and molybdenum are added to hit the 0.40–0.70%, 0.40–0.60%, and 0.15–0.25% ranges, respectively.
2. Forging & Rolling:
   • Most AISI 8630 parts start as Hot Forged blanks (1,150 – 1,250 °C)—forging aligns grain structure, boosting core strength for heavy loads. After forging, blanks are Hot Rolled to rough shapes (thick bars, plates) or left as-forged for large parts (por exemplo, crane shafts).
3. Annealing:
   • Heated to 815–845 °C, held 3–4 hours, slow-cooled to 650 °C. Softens the steel (20–24 HRC) for machining and removes forging stress.
4. Usinagem:
   • Annealed AISI 8630 is machined into near-final shapes (por exemplo, gear teeth, shaft ends) using turning, fresagem, ou perfuração. Carbide tools are recommended for thick sections to avoid tool wear.
5. Carburizing (Heavy-Duty Focus):
   • Gas Carburizing: Parts are heated to 880–920 °C in carbon-rich gas for 6–16 hours (longer than AISI 8620) to create a 1.0–1.5 mm thick hard layer (0.8–1.0% C).
   • Têmpera: Cooled to 830–850 °C, held 30 minutos, then quenched in oil. Hardens surface to 58–60 HRC and core to 35–40 HRC.
   • Temperamento: Reheated to 200–250 °C for 2–3 hours, air-cooled. Reduces surface brittleness while keeping core strength.
6. Tratamento de superfície:
   • Moagem: Carburized parts are precision-ground to smooth surfaces and meet tight tolerances (por exemplo, gear tooth accuracy).
   • Shot Peening: Blasts the surface with metal balls to reduce residual stress and boost limite de fadiga (critical for cyclic heavy loads).
   • Revestimento: Epoxy coating (for construction equipment) or zinc plating (for outdoor parts) to resist corrosion.
7. Controle de qualidade:
   • Chemical Analysis: Spectrometry verifies alloy content (per ASTM A29/A29M).
   • Mechanical Testing: Tensile tests confirm core strength; hardness tests check surface (58–60 HRC) and core (35–40 HRC).
   • Microstructural Analysis: Ensures a uniform carburized layer and fine-grain core (no large grains that cause weakness).
   • NDT: Ultrasonic testing checks for internal defects; radiographic testing inspects thick sections (por exemplo, axle shafts).

4. Case Studies: AISI 8630 in Action

Real heavy-duty projects highlight AISI 8630’s performance.

Estudo de caso 1: Heavy-Duty Truck Axle Shafts (U.S.)

A truck manufacturer had to replace AISI 8620 axle shafts every 300,000 km—they bent under heavy loads. They switched to AISI 8630 eixos, carburized to 59 HRC and shot-peened. The new shafts lasted 500,000 km—no bending or wear—because the stronger core (38 CDH) handled 10-ton loads, and the hard surface resisted road abrasion. This saved the manufacturer $2 million in warranty costs annually.

Estudo de caso 2: Mining Conveyor Gears (Australia)

A mining site’s conveyor gears (AISI 4140) failed every 18 months due to wear and load cracking. They installed AISI 8630 engrenagens, carburized to 60 CDH. The gears lasted 4 years—wear was reduced by 70%, and no cracks occurred—because the carburized surface resisted dirt abrasion, and the nickel-boosted core absorbed conveyor load shocks. This cut maintenance downtime by 60%.

5. AISI 8630 contra. Outros materiais

How does AISI 8630 compare to similar heavy-duty and carburizable steels?

Yigu Technology’s Perspective on AISI 8630 Liga de aço

Na tecnologia Yigu, AISI 8630 is our top choice for heavy-duty carburized parts. Its medium-low carbon Ni-Cr-Mo composition solves the biggest pain point for clients: getting a part that resists weare handles heavy loads—critical for trucks, construção, and mining. We supply AISI 8630 in forged blanks, thick bars, or machined components, with custom carburizing (1.0–1.5 mm layers) and shot peening. For clients upgrading from AISI 8620 ou 4140, AISI 8630 delivers 50% longer lifespan for heavy loads at a small premium, cutting long-term costs.

FAQ About AISI 8630 Liga de aço

1. Can AISI 8630 be used without carburizing?
   Yes—but it’s not optimal. Non-carburized AISI 8630 has good strength (700 MPa tensile) but poor wear resistance, so it’s only used for heavy-load parts with no friction (por exemplo, non-wearing brackets). Carburizing unlocks its full wear-load potential.
2. What’s the maximum part thickness for AISI 8630 cementação?
   AISI 8630 works well for parts up to 150 mm thick—its chromium content ensures uniform carburizing. For thicker parts (>150 mm), extend carburizing time (16+ horas) and use oil quenching to avoid core softening.
3. Is AISI 8630 more expensive than AISI 8620?
   Yes—about 10% more. But the extra cost is worth it for heavy loads: AISI 8630’s stronger core (35–40 HRC vs. 30–35 HRC for 8620) prevents bending, and its longer lifespan cuts maintenance costs by 30–50% over time.