Choosing the Right Carbon Steel Grade for Your Project

Choosing the right carbon steel grade isn’t just a box to check—it’s a strategic decision that directly affects your project's performance, manufacturability, and bottom line. Whether you're fabricating equipment, framing a structure, or stamping parts for automotive, selecting the appropriate grade requires understanding both the material’s properties and how they align with your end-use requirements. 

At Mill Steel Company, we serve a broad range of industries with precision-processed steel products. Here's what you need to know to make a confident, informed carbon steel selection. 

What Is Carbon Steel? 

Carbon steel is an iron-carbon alloy with up to 2.1% carbon content by weight. It's known for its versatility, affordability, and excellent mechanical properties. The amount of carbon, combined with the steel’s other elements and how it's processed, determines everything from formability to strength to weldability. 

Carbon steel is typically categorized by carbon content: 

• Low Carbon Steel: < 0.30% carbon – great formability and weldability
• Medium Carbon Steel: 0.30%–0.60% carbon – increased strength, lower ductility
• High Carbon Steel: > 0.60% carbon – high hardness, wear resistance, limited formability 

Common Grade Systems: Understanding Designations 

There are several systems used to designate steel grades, and understanding the basics will help you navigate product specs: 

• AISI/SAE (American Iron and Steel Institute / Society of Automotive Engineers): Uses a four-digit number system (e.g., 1018, 1045) to describe carbon and alloy steels.
• ASTM (American Society for Testing and Materials): Specifies standards for steel by intended use (e.g., A36 for structural steel).
• CSA, JIS, EN: Other systems used internationally, depending on region and industry. 

Many carbon steel products meet multiple standards. At Mill Steel, our material is certified to meet the specs you need, whether that's ASTM, SAE, or OEM requirements. 

Popular Carbon Steel Grades and Where They’re Used 

Here’s a closer look at common grades available:  

A36 – Structural Standard 

• Spec: ASTM A36
• Type: Low carbon
• Highlights: One of the most widely used carbon steel grades due to its high weldability, machineability, and formability. Great for projects were strength and flexibility are needed.
• Applications: Construction (beams and columns), channels, equipment frames, angles, bridges, and general fabrication  

A1011 – Hot Rolled Sheet & Coil 

• Spec: ASTM A1011
• Type: Low carbon
• Highlights: General-purpose hot-rolled steel; good formability
• Applications: Agricultural equipment, automotive components, stampings 

A1018 – Flat Bar and Sheet 

• Spec: ASTM A1018
• Type: Low carbon
• Highlights: Similar to A1011 but includes higher strength options
• Applications: Bar grating, heavy equipment parts 

1010 / 1018 – Precision Machining 

• Spec: SAE 1010 / SAE 1018
• Type: Low carbon
• Highlights: 1010 offers excellent formability; 1018 is ideal for machining
• Applications: Shafts, fasteners, pins, and precision parts 

1020 / 1045 – Medium Carbon Workhorses 

• Spec: SAE 1020 / 1045
• Type: Medium carbon
• Highlights: 1020 balances strength and ductility; 1045 is stronger and harder. It’s often heat treated for enhanced performance in wear-heavy applications.
• Applications: Gears, axles, hydraulic components 

A572 Grade 50 – High Strength, Low Alloy 

• Spec: ASTM A572
• Type: Low-alloy, high-strength
• Highlights: With a higher strength-to-weight ratio than A36, A572 Grade 50 allows for lighter structures without sacrificing performance. It’s an industry standard for heavy-duty structural needs. High yield strength and good weldability.
• Applications: Bridges, buildings, heavy equipment, transmission towers  

A516 Grade 70 – Pressure Vessel Steel 

• Spec: ASTM A516
• Type: Medium carbon, fine-grain
• Highlights: Excellent notch toughness and is commonly used in environments with high pressure and temperature. It’s known for its excellent strength and toughness.
• Applications: Boilers, tanks, pressure vessels 

A606 Type 4 – Corrosion-Resistant Weathering Steel 

• Spec: ASTM A606
• Type: Low carbon with copper, chromium, nickel
• Highlights: Atmospheric corrosion resistance
• Applications: Architectural panels, shipping containers, railcars 

How Specs Influence Grade Selection 

Specifications (or "specs") define minimum performance standards, dimensional tolerances, chemical composition, and mechanical properties. 

Here’s how specs play into your decision: 

• Strength Requirements: Need a minimum yield or tensile strength? Specs like A572 or A514 (for high-strength applications) lay out exact expectations.
• Formability or Weldability: Products like A1011 CS Type B or SAE 1008/1010 are better for forming and deep drawing.
• Corrosion Resistance: Weathering steels (A606, A588) or galvanized options may be best.
• End-Use Compliance: Automotive, construction, and pressure vessel applications often require compliance with OEM or federal standards. 

Always consult the mill test report (MTR) and verify that the material meets the correct spec for your application. 

Match the Grade to the Job 

Remember, there’s no universal “best” carbon steel grade, just the best grade for your application. Understanding how carbon content, processing method, and specification impact performance will help you minimize risk and improve results. 

Source From a Partner You Can Trust  

At Mill Steel Company, we offer: 

• Vast inventory of hot rolled, cold rolled, and coated carbon steel
• Full traceability and certification for every order
• Technical support to align your material with end-use demands 

Need help choosing the right grade? Our experienced team is here to help. Contact us today or shop our product offerings online.