When selecting steel tubing for structural or mechanical applications, two common standards often come up: ASTM A500 and ASTM A513.
Both are widely used across industries — but they’re not interchangeable.
If you’re a fabricator, distributor, engineer, or someone working with steel, understanding the differences can help you make smarter, safer, and more cost-effective choices.
Let’s break it down.
🔩 What Is ASTM A500 Tubing?
ASTM A500 is a structural-grade specification for cold-formed, welded carbon steel tubing used in load-bearing applications.
✅ Key Features of ASTM A500:
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Purpose: Designed for structural applications like buildings, bridges, and heavy frameworks
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Shapes: Available in round, square, and rectangular tubing
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Manufacturing Process: Made via Electric Resistance Welding (ERW)
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Grades: A, B, C, and D — with increasing strength from A to D
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Strength: Higher tensile and yield strength compared to A513
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Weldability: Excellent for structural welds
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Corrosion Resistance: Good when properly coated or galvanized
🏗️ Common Uses of A500:
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Structural steel frames
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Infrastructure (e.g. bridges, piers, towers)
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Construction and heavy equipment
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Support columns and load-bearing assemblies
⚙️ What Is ASTM A513 Tubing?
ASTM A513 is a mechanical-grade tubing standard used for precision applications requiring tighter dimensional tolerances and smoother surfaces.
✅ Key Features of ASTM A513:
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Purpose: Best for mechanical or ornamental applications
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Manufacturing Process: Made with ERW or Drawn-Over-Mandrel (DOM) for smoother finishes
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Precision: Tight OD/ID tolerances, consistent wall thickness
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Strength: Lower strength than A500, but higher machinability
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Surface Finish: Smooth, clean, and often used where aesthetics matter
🔧 Common Uses of A513:
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Automotive components (steering columns, frames)
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Furniture and appliances
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Fitness and gym equipment
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Roll cages and custom mechanical assemblies
🔍 ASTM A500 vs. A513: Side-by-Side Comparison
| Feature | ASTM A500 (Structural Tubing) | ASTM A513 (Mechanical Tubing) |
|---|---|---|
| Primary Use | Structural support (buildings, bridges) | Precision parts (automotive, furniture) |
| Manufacturing | ERW only | ERW or DOM |
| Shapes | Round, square, rectangular | Mostly round, but varies |
| Strength | Higher tensile & yield strength | Lower strength |
| Surface Finish | Rougher, industrial-grade | Smooth, finished surface |
| Machinability | Lower (harder to machine) | Higher (easier to machine) |
| Applications | Load-bearing, structural | Precision, appearance-focused |
🧠 So, Which One Should You Use?
Here’s a quick rule of thumb:
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✅ Choose ASTM A500 if your project involves structural loads, heavy-duty support, or safety-critical frameworks.
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✅ Choose ASTM A513 if you need precise dimensions, smooth finishes, or higher machinability for mechanical components.
💡 Final Thoughts
Both ASTM A500 and ASTM A513 play critical roles in the steel and metals industry — but understanding their core differences is essential for project success.
The wrong choice can mean over-engineering (and overspending), or worse — underperformance or safety issues.
Not sure which to pick?
Always consult with a qualified steel supplier or engineer to match the spec to your application.
