Acier à roulement inoxydable GB 9Cr18Mo: Propriétés, Utilisations & Guide de comparaison

Si vous travaillez dans des secteurs comme le traitement chimique, équipement médical, ou génie maritime, vous avez besoin d'un acier pour roulements capable de résister aux produits chimiques agressifs, humidité, and wear—all at once.GB 9Cr18Mo stainless bearing steel—a Chinese national standard martensitic stainless steel—delivers exactly this. Il combine une forte résistance à la corrosion avec la dureté nécessaire aux roulements, solving the common problem of rusted or worn-out parts in tough environments. Ce guide détaille ses principales propriétés, applications du monde réel, processus de fabrication, et comment il se compare à d'autres matériaux, helping you make the right choice for your project.

1. Material Properties of GB 9Cr18Mo Stainless Bearing Steel

GB 9Cr18Mo’s unique composition—high chromium and molybdenum—sets it apart from standard bearing steels. Let’s explore its properties in detail.

1.1 Chemical Composition

GB 9Cr18Mo follows strict Chinese National Standards (GB/T 1220), ensuring consistent performance for corrosion and wear resistance. Below is its typical chemical makeup:

1.2 Physical Properties

These properties describe how GB 9Cr18Mo behaves under physical conditions like temperature and magnetism:

• Densité: 7.75 g/cm³ (slightly lower than standard carbon bearing steels like GCr15)
• Point de fusion: 1,450 – 1,480 °C (2,642 – 2,696 °F)
• Conductivité thermique: 24.5 W/(m·K) à 20 °C (room temperature)—lower than carbon steels, typical of stainless grades
• Coefficient de dilatation thermique: 10.6 × 10⁻⁶/°C (depuis 20 – 100 °C)
• Magnetic Properties: Ferromagnetic (attracts magnets)—unlike non-magnetic austenitic stainless steels (par ex., AISI 304), making it easy to sort and inspect.

1.3 Propriétés mécaniques

GB 9Cr18Mo’s mechanical performance is achieved through heat treatment (trempe et revenu). Below are typical values:

1.4 Other Properties

GB 9Cr18Mo’s standout properties make it ideal for harsh environments:

• Résistance à la corrosion: Excellent—resists saltwater, acides doux, et produits chimiques. Outperforms standard carbon bearing steels (par ex., GCr15) and even matches some high-end stainless grades like AISI 440C.
• Résistance à l'usure: High carbon and chromium form hard carbides, ensuring it can handle rolling/sliding contact in bearings.
• Hardenability: Good—can be heat-treated to uniform hardness across thick sections, perfect for large bearings.
• Stabilité dimensionnelle: Minimizes distortion during heat treatment, ensuring precision in critical parts like bearing races and rolling elements.
• Martensitic Structure: Yes—this structure (formed during quenching) gives it both hardness and magnetism, which is key for bearing performance.

2. Applications of GB 9Cr18Mo Stainless Bearing Steel

GB 9Cr18Mo’s corrosion + wear resistance makes it perfect for wet, chimique, or sanitary environments. Here are its most common uses:

• Roulements: Corrosion-resistant bearings in chemical pumps, marine engines, and medical equipment—where water or chemicals would rust standard steel.
• Rolling Elements: Balls, rouleaux, or needles in wet bearings (par ex., washing machine bearings or boat propeller shafts).
• Races: Inner/outer rings of bearings in food processing machines or pharmaceutical mixers—needing frequent cleaning and rust resistance.
• Composants automobiles: Bearings in car washes, undercarriage parts (exposed to salt and rain), or fuel systems (resisting fuel chemicals).
• Machines industrielles: Bearings in chemical processing mixers, wastewater treatment equipment, and humid factory gearboxes.
• Composants aérospatiaux: Small bearings in aircraft hydraulic systems (resisting hydraulic fluids and moisture).
• Dispositifs médicaux: Bearings in surgical drills, sterilizable tools, et matériel de diagnostic (able to withstand autoclaving).
• Food Processing Equipment: Bearings in conveyors, dough mixers, and filling machines—meeting food safety standards (par ex., GB 4806 for China).
• Marine Applications: Bearings in boat engines, deck winches, and underwater pumps (fighting saltwater corrosion).
• Chemical Processing Equipment: Bearings in acid tanks, solvent transfer pumps, and chemical reactors.

3. Manufacturing Techniques for GB 9Cr18Mo

Producing GB 9Cr18Mo requires techniques that preserve both its corrosion and wear resistance. Here’s the typical process:

1. Steelmaking:
   • GB 9Cr18Mo is made using an Electric Arc Furnace (EAF) with argon oxygen decarburization (AOD). This process controls carbon content (for hardness) and ensures high chromium/molybdenum levels (pour la résistance à la corrosion), meeting GB/T 1220 normes.
2. Roulement:
   • After steelmaking, the metal is Hot Rolled (à 1,100 – 1,200 °C) into billets or bars. For precision parts (like small bearing rings), c'est Cold Rolled (room temperature) to improve surface finish and dimensional accuracy.
3. Precision Forging:
   • Pièces complexes (par ex., custom bearing races) are forged into near-final shapes at high temperatures. Forging refines the grain structure, enhancing both strength and corrosion resistance.
4. Traitement thermique:
   • The most critical step to unlock GB 9Cr18Mo’s performance:
     • Trempe: Heat the steel to 950 – 1,000 °C, then rapidly cool it in oil to harden (forms a martensitic structure).
     • Tempering: Reheat to 150 – 200 °C (twice for consistency) to reduce brittleness while maintaining hardness and corrosion resistance.
5. Usinage:
   • Post-heat treatment, parts are machined using Affûtage (for ultra-smooth surfaces, reducing friction in bearings) et Tournant (for cylindrical shapes like bearing races). CNC machines ensure tight tolerances (±0,001 mm) for precision fits.
6. Traitement de surface:
   • Optional steps to enhance performance:
     • Passivation: Treat with nitric acid to strengthen the chromium oxide layer, boosting corrosion resistance.
     • Polissage: Achieve a mirror finish for sanitary applications (par ex., transformation des aliments), making cleaning easier and preventing bacterial buildup.
     • Revêtement: Thin PTFE coatings for extra resistance to strong chemicals (par ex., in industrial acid tanks).
7. Contrôle de qualité:
   • Rigorous testing ensures compliance with GB standards:
     • Chemical analysis: Use spectrometry to verify chromium, molybdène, and carbon content.
     • Corrosion testing: Salt spray tests (pour GB/T 10125) to check resistance to saltwater.
     • Hardness testing: Measure Rockwell hardness to ensure HRC 58–62.
     • Dimensional inspection: Use coordinate measuring machines (MMT) to check part tolerances.

4. Études de cas: GB 9Cr18Mo in Action

Real-world examples show how GB 9Cr18Mo solves industry challenges.

Étude de cas 1: Chemical Processing Bearing Reliability

A Chinese chemical plant faced monthly bearing failures in their acid transfer pumps. The original bearings used GCr15 steel, which corroded quickly in the acidic environment. Switching to GB 9Cr18Mo bearings (with passivation) extended bearing life to 12 mois. This reduced maintenance downtime by 90% et sauvé $150,000 annually in replacement parts.

Étude de cas 2: Marine Equipment Bearing Durability

A shipyard struggled with propeller shaft bearing failures (chaque 6 mois) due to saltwater corrosion. They replaced standard stainless steel bearings with GB 9Cr18Mo bearings. Post-switch, the bearings lasted 3 années, cutting replacement costs by 75% and reducing ship downtime for repairs.

5. GB 9Cr18Mo vs. Other Materials

How does GB 9Cr18Mo compare to other common bearing steels and materials? The table below breaks it down:

Yigu Technology’s Perspective on GB 9Cr18Mo

Chez Yigu Technologie, GB 9Cr18Mo is our top choice for clients in Chinese chemical, marin, et industries médicales. Its high molybdenum content gives it better chemical resistance than AISI 440C or JIS SUS440C—critical for harsh acids or saltwater. We pair it with precision grinding and passivation to meet GB safety standards, making parts that last 5–8x longer than GCr15 in wet environments. For clients needing global compatibility, we also offer GB 9Cr18Mo as a direct alternative to AISI 440C, ensuring consistent performance across markets.

FAQ About GB 9Cr18Mo Stainless Bearing Steel

1. Why is molybdenum important in GB 9Cr18Mo?
   Molybdène (0.90–1.30%) boosts GB 9Cr18Mo’s resistance to chemicals (like acids) and high temperatures—making it better than stainless bearing steels with less molybdenum (par ex., AISI 440C) for harsh industrial environments.
2. Can GB 9Cr18Mo be used in food processing?
   Yes—when polished and passivated, it meets food safety standards (par ex., China’s GB 4806 and global FDA standards). Its corrosion resistance prevents rust from contaminating food, and its smooth surface is easy to clean.
3. Is GB 9Cr18Mo interchangeable with AISI 440C?
   Mostly yes—both are martensitic stainless bearing steels with similar wear and corrosion resistance. GB 9Cr18Mo has more molybdenum (better for chemicals), but it can replace AISI 440C in most applications like marine bearings or medical tools.