Can 1018 steel be hardened?

Can 1018 Steel Be Hardened?

SAE-AISI 1018 steel is a low-carbon steel widely used for its excellent machinability, weldability, and affordability, making it a popular choice for precision components like shafts, pins, and fasteners. A common question is whether 1018 steel can be hardened to improve its strength and wear resistance. As a leading ASTM A 36 steel plate supplier, Gangsteel provides insights into material properties, including alternatives to ASTM A36/A36M like 1018. This article explores whether 1018 steel can be hardened, the methods available, their effectiveness, and how it compares to other steels.

Understanding 1018 Steel

Before discussing hardening, let’s review 1018’s key properties:

• Chemical Composition: 0.15-0.20% carbon, 0.60-0.90% manganese, trace amounts of phosphorus and sulfur.
• Mechanical Properties:
  • Yield Strength: ~370 MPa (53,700 psi, cold-rolled).
  • Tensile Strength: ~440 MPa (63,800 psi).
  • Hardness: Typically 126-197 HB (Brinell hardness) in cold-rolled condition; ~126-150 HB when annealed.
• Processing: Usually cold-rolled or cold-drawn, providing a smooth surface and moderate strength.
• Applications: Machined parts, fasteners, and components where ease of machining and cost are priorities.

1018’s low carbon content makes it ductile and easy to machine but limits its ability to achieve significant hardness through conventional heat treatments compared to higher-carbon or alloy steels.

Can 1018 Steel Be Hardened?

Yes, 1018 steel can be hardened, but its low carbon content (0.15-0.20%) restricts the degree of hardening achievable through standard methods like quenching and tempering. Unlike medium- or high-carbon steels (e.g., 1045, 4140), 1018 has limited hardenability, meaning it cannot achieve high hardness levels without specialized processes. Below are the primary methods to harden 1018 steel and their effectiveness:

1. Case Hardening (Carburizing)

• Process: Carburizing involves heating 1018 steel in a carbon-rich environment (e.g., carbon gas or a carbon-containing material) at high temperatures (around 850-950°C or 1560-1740°F), allowing carbon to diffuse into the surface. The steel is then quenched to harden the carbon-enriched surface.
• Result:
  • Surface Hardness: Can reach ~55-60 HRC (Rockwell C) or ~500-600 HB, creating a hard outer layer.
  • Core Hardness: The core remains soft (~126-150 HB), providing toughness and ductility.
• Effectiveness: Highly effective for improving surface hardness and wear resistance while maintaining a tough core. This is the most common hardening method for 1018.
• Applications: Carburized 1018 is used for parts like gears, cams, and pins that need a hard, wear-resistant surface but a ductile core to resist cracking.
• Limitations: Only the surface is hardened (typically 0.5-2 mm deep), and the process is more complex and costly than standard heat treatments.

2. Cold Working

• Process: Cold rolling or cold drawing work-hardens 1018 by deforming the steel at room temperature, increasing its strength and hardness through strain hardening.
• Result:
  • Hardness: Increases to ~150-197 HB (vs. ~126 HB in annealed state).
  • Strength: Yield strength can rise to ~370 MPa or higher, depending on the degree of cold work.
• Effectiveness: Moderately effective for slight hardness and strength increases, but nowhere near the levels of carburizing or higher-carbon steels.
• Applications: Cold-rolled 1018 is used for shafts, fasteners, and components needing moderate strength and a smooth finish.
• Limitations: Hardness gains are limited, and excessive cold working can reduce ductility, making the steel brittle.

3. Quenching and Tempering

• Process: Heating 1018 to a high temperature (around 815-870°C or 1500-1600°F) and quenching in water or oil, followed by tempering to reduce brittleness.
• Result:
  • Hardness: Minimal increase, typically not exceeding ~150-180 HB, due to low carbon content.
  • Strength: Slight improvement in strength, but far less than for higher-carbon steels.
• Effectiveness: Ineffective for significant hardening. 1018’s low carbon content prevents the formation of hard martensite during quenching, unlike steels like 4140 or 1045.
• Applications: Rarely used for 1018, as it offers little benefit compared to carburizing.
• Limitations: Low hardenability makes this method impractical for most applications.

Comparison with Other Steels

To understand 1018’s hardening potential, let’s compare it to other steels and ASTM A36:

• SAE-AISI 4140 (Low-Alloy Steel):
  • Carbon Content: 0.38-0.43%.
  • Hardness: Can reach 229-600 HB (20-50 HRC) when quenched and tempered, far exceeding 1018’s capabilities.
  • Why Harder?: Higher carbon and alloying elements (chromium, molybdenum) enhance hardenability, allowing deep hardening through quenching.
  • Applications: Gears, crankshafts, and dies needing high strength and wear resistance.
• SAE-AISI 1045 (Medium-Carbon Steel):
  • Carbon Content: 0.43-0.50%.
  • Hardness: ~200-300 HB (20-30 HRC) when quenched and tempered, significantly harder than 1018.
  • Why Harder?: Higher carbon content enables better martensite formation during quenching.
  • Applications: Shafts, bolts, and machinery parts.
• ASTM A36 (Low-Carbon Structural Steel):
  • Carbon Content: ≤0.26%.
  • Hardness: ~119-159 HB (hot-rolled), similar to annealed 1018 but lower than cold-rolled 1018.
  • Hardening: Like 1018, A36 has limited hardenability and is typically carburized for surface hardening. It’s used for structural applications (e.g., beams, plates) supplied by Gangsteel as an ASME SA 36 steel plate supplier.
  • Applications: Bridges, buildings, and general construction.

Practical Considerations for Hardening 1018

• When to Harden 1018: Use carburizing for parts needing a hard, wear-resistant surface (e.g., gears, pins). Cold working is sufficient for slight strength increases in non-critical components.
• Limitations: 1018’s low carbon content makes it unsuitable for through-hardening via quenching, unlike 4140 or 1045. If high hardness is critical, consider a higher-carbon or alloy steel.
• Cost vs. Performance: Carburizing 1018 is more expensive than using it as-is but cheaper than switching to inherently harder steels like 4140. Cold working is a low-cost hardening option but offers limited gains.
• Project Needs: For structural applications, ASTM A36/A36M may suffice without hardening, while 1018 is better for precision parts. If hardness is a priority, evaluate 4140 or 1045.

Why Choose Gangsteel?

While Gangsteel specializes in structural steels like ASTM A36/A36M, we can guide you in selecting or sourcing 1018 or harder alternatives like 4140 for your project. Our services include:

• Quality Assurance: Compliance with ASTM, AISI, and international standards.
• Custom Solutions: Steel tailored to your specifications.
• Expert Support: Advice on material selection and hardening processes.

Conclusion: 1018 steel can be hardened, primarily through carburizing for surface hardness (up to 55-60 HRC) or cold working for moderate gains (up to ~197 HB). However, its low carbon content limits through-hardening compared to steels like 4140 or 1045. For projects requiring minimal hardening, 1018 is cost-effective; for high hardness, consider alloy steels. Contact Gangsteel, a reliable ASTM A 36 steel plate supplier, for quality steel solutions and expert guidance.