Introduction
1008 is a quality low-carbon structural steel (carbon ≤ 0.10%) widely used for cold forming and cold heading of fasteners. It contains lower levels of sulfur, phosphorus, and non-metallic inclusions than standard carbon structural steels, resulting in superior mechanical consistency and formability.
1008 steel offers good workability, easy weldability, and can be continuously improved in strength through cold working. It is the standard material for Grade 4.8 and Grade 4 fasteners (rivets, screws, nuts, and bolts) where moderate strength and excellent cold formability are required.
Important note on machinability: 1008 is not suitable for cutting operations. Thread cutting, broaching, and smooth turning on a lathe should be avoided. For free-machining applications, see 1215 free-cutting steel or 12L14.
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Chemical Composition
1008 composition varies slightly across standards. The table below compares key references:
| Grade | Standard | C (%) | Mn (%) | Si (%) | P (%) | S (%) | Al (%) |
|---|---|---|---|---|---|---|---|
| 1008 | SAE J403-2001 | ≤ 0.10 | 0.30–0.50 | — | ≤ 0.03 | ≤ 0.05 | — |
| 1008 | ASTM A29/A29M | ≤ 0.10 | 0.30–0.50 | — | ≤ 0.04 | ≤ 0.05 | — |
| 1008D | ASTM A1040 | ≤ 0.10 | 0.30–0.50 | — | ≤ 0.04 | ≤ 0.05 | — |
| 1008E | ASTM A1040 | ≤ 0.10 | ≤ 0.50 | — | ≤ 0.03 | ≤ 0.035 | — |
| SWRCH8A | Q/BQB517-2023 (Baosteel) | ≤ 0.10 | ≤ 0.60 | ≤ 0.10 | ≤ 0.020 | ≤ 0.020 | ≥ 0.020 |
Notes on composition:
- Silicon (Si): When specified for carbon steels, Si is typically selected from six standard ranges: ≤ 0.10%, 0.10–0.20%, 0.15–0.35%, 0.15–0.40%, 0.20–0.40%, or 0.30–0.60%.
- Copper (Cu): When specified, Cu ≥ 0.20%.
- Boron (B): When boron is added to killed steel to improve hardenability, titanium is typically added to protect boron from oxidation. B content: 0.0005–0.003%. If titanium is not permitted, B may reach 0.005%.
- SWRCH8A (Q/BQB517) specifies tighter P (≤ 0.020%) and S (≤ 0.020%) limits and requires minimum Al (≥ 0.020%) for grain refinement — reflecting higher cleanliness standards for cold heading wire rod in China.
Mechanical Properties (Wire Rod)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 405 MPa |
| Yield Strength | ≥ 275 MPa |
| Reduction of Area (Z) | ≥ 50% |
| Elongation after fracture (A) | ≥ 24% |
| Hardness (as-rolled) | ≤ 197 HB |
| Normalizing temperature | 910 °C |
Fastener Grade Capability
| Fastener Type | Maximum Grade |
|---|---|
| Bolts / Screws | Grade 4.8 |
| Nuts / Rivets | Grade 4 |
For higher-grade fasteners (Grade 8.8–9.8), see 10B21 boron steel.
Applications
1008 is primarily used for cold-formed fasteners and hardware where moderate strength and excellent formability are required:
- Fasteners — rivets, screws, bolts, and nuts (Grade 4 / 4.8); the primary application
- Cold-formed structural parts — brackets, clips, and stampings
- Automotive body hardware — body fasteners, clips, and retainers
- Electrical hardware — terminals, connectors, and mounting hardware
- General hardware — hooks, pins, and light-duty structural components
Fabrication Characteristics
Cold Heading & Cold Forming
1008 is optimized for cold heading and cold extrusion. Its very low carbon content (≤ 0.10%) and low Mn (0.30–0.50%) result in low hardness, high plasticity, and excellent cold deformability. It is one of the most commonly used wire rod grades for cold-headed fastener production globally.
Machinability
Poor. 1008 is not suitable for cutting operations. Thread cutting, broaching, and smooth turning should be avoided due to its tendency to produce long, stringy chips and poor surface finish. For precision turning applications, 1215 or 12L14 are the appropriate choices.
Weldability
1008 has excellent weldability. All standard welding methods are applicable. The very low carbon content minimizes hardenability and heat-affected zone cracking risk, making it one of the most weldable carbon steels available.
Case Hardening
1008 can be case-carburized to achieve surface hardness above HV 400, while the core remains soft and tough. This is useful for wear-resistant surface applications. Through-hardening is not applicable due to the very low carbon content.
Corrosion Resistance
1008 has no inherent corrosion resistance as a plain carbon steel. Surface protection is required for corrosive environments, including zinc plating, nickel plating, black oxide, phosphating, or organic coatings.
Standards reference: SAE J403-2001 | ASTM A29/A29M | ASTM A1040 | Q/BQB517-2023 (Baosteel, SWRCH8A)
Content authorized for publication by FULLERKREG.