Carbon Steel Bolting Materials
Carbon steel fasteners offer an excellent balance of strength, durability, and cost-effectiveness for general engineering and structural applications.
Metric Property Classes (ISO 898-1)
Grade 4.6
Tensile: 400 MPa
Yield: 240 MPa
Low strength applications
Grade 4.8
Tensile: 400 MPa
Yield: 320 MPa
Light structural
Grade 8.8
Tensile: 800 MPa
Yield: 640 MPa
Most common high strength
Grade 10.9
Tensile: 1000 MPa
Yield: 900 MPa
High strength applications
Grade 12.9
Tensile: 1200 MPa
Yield: 1080 MPa
Very high strength
Imperial Grades (SAE J429)
Grade 2
Low carbon steel
Tensile: 60,000 psi
General purpose
Grade 5
Medium carbon steel
Tensile: 120,000 psi
Most common grade
Grade 8
Alloy steel, heat treated
Tensile: 150,000 psi
High strength
Structural Bolting
ASTM A325
Structural bolts, heat treated
Tensile: 120/105 ksi
Steel construction
ASTM A490
High-strength structural bolts
Tensile: 150/130 ksi
Heavy structural
ASTM F3125
Combines A325 & A490
Current structural standard
Grade A325 & A490
ASTM Carbon Steel Standards
| Standard | Grade | Description |
|---|---|---|
| ASTM A194 | 2, 2H, 2HM | Carbon steel nuts for high temperature |
| ASTM A307 | Grade A, B | Carbon steel bolts and studs, general purpose |
| ASTM A325 | Type 1, 2, 3 | Structural bolts, heat treated |
| ASTM A490 | Type 1, 2, 3 | High-strength structural bolts |
| ASTM F3125 | A325, A490 | Structural bolts, replaces A325 & A490 |
Surface Finishes
Plain Finish
No coating, black oxide
Indoor dry applications
Zinc Plated
Electro-galvanized
Mild corrosion protection
Hot-Dip Galvanized
Thick zinc coating
Outdoor applications
Dacromet®
Zinc flake coating
Superior corrosion protection
Phosphate
Black phosphate coating
Oil absorption
Cadmium Plated
Military/aerospace
Excellent corrosion resistance
Applications
Construction
Building structures, bridges, towers
Automotive
Vehicle assembly, chassis components
Machinery
General industrial equipment
Manufacturing
Production equipment, fixtures
Property Class Explanation
Understanding Grade Markings (e.g., 8.8):
• First number (8): Tensile strength in 100 MPa (8 × 100 = 800 MPa)
• Second number (.8): Yield to tensile ratio (0.8 × 800 = 640 MPa yield)
Imperial Grade Markings:
• Grade 2: No head marking
• Grade 5: Three radial lines on head
• Grade 8: Six radial lines on head