Grade 8

Grade 8 fasteners are high-strength, high-performance fasteners made from medium-carbon alloy steel that has been quenched and tempered. They are designed for heavy-duty applications where high tensile and yield strengths are essential. Grade 8 fasteners are commonly used in demanding environments, such as automotive, heavy equipment, and structural applications, where strength and durability are critical.

Key Characteristics of Grade 8 Fasteners:

1. Material Composition: Made from medium-carbon alloy steel with elements like carbon, manganese, and chromium, which enhance the hardening capability and strength of the steel.

2. Mechanical Properties:

   • Tensile Strength: Approximately 150,000 psi (1,034 MPa), making them suitable for high-stress applications.
   • Yield Strength: Around 130,000 psi (896 MPa), which is about 87% of the tensile strength, ensuring they can handle significant loads before deforming.
   • Hardness: Typically in the range of Rockwell C33 to C39, indicating a hard and durable fastener.

3. Heat Treatment: Grade 8 fasteners are heat-treated through quenching and tempering processes to achieve their high strength and toughness, enhancing their performance under load.

4. Corrosion Resistance: Generally, Grade 8 fasteners have limited corrosion resistance. They are often coated with zinc, cadmium, or other protective finishes to improve rust resistance, especially when used in outdoor or corrosive environments.

5. Applications:

   • Used in heavy machinery, automotive assembly, and industrial equipment.
   • Ideal for applications requiring high clamping force and resistance to shearing and stretching under high stress.
   • Commonly used in critical structural connections where safety is paramount.

6. Identification: Grade 8 fasteners can be identified by six radial lines on the head of the bolt, which distinguish them from lower-grade fasteners.

7. Standards Compliance: Conforms to specifications such as SAE J429, ASTM A354, and other relevant standards that define the material, mechanical properties, and quality control measures.

8. Magnetic Properties: Magnetic due to their steel composition, which is typical for most high-strength alloy steels.

Grade 8 fasteners are known for their superior strength and durability, making them ideal for high-stress and high-load applications where reliability and safety are crucial. They are often preferred in critical connections where failure is not an option.