Material Overview & Common Uses
A36 is a low-carbon structural steel (0.25–0.29% carbon) with a minimum yield strength of 36,000 psi (250 MPa) and tensile strength of 58,000–80,000 psi (400–550 MPa). It is the most common hot rolled steel grade in Canadian fabrication shops, valued for its excellent weldability, formability, and machinability. Typical applications include structural beams, brackets, machine bases, frames, guards, and general-purpose plate work. Hot rolled surface finish is characterized by a dark, mill scale (iron oxide) layer that must be removed before painting or welding in critical applications.
Machinability, Tooling & Feeds
A36 is rated as having good machinability (approximately 70% of 1212 free-machining steel). Use positive rake tooling and adequate coolant (water-soluble oil at 5–10% concentration) to prevent built-up edge.
Recommended Cutting Parameters
| Operation | Tool Type | Speed (SFM) | Speed (m/min) | Feed Rate |
|---|
| Turning | HSS | 80–120 | 24–37 | 0.005–0.015 in/rev |
| Turning | Carbide | 300–500 | 91–152 | 0.005–0.015 in/rev |
| Milling | HSS | 60–90 | 18–27 | 0.002–0.006 in/tooth |
| Milling | Carbide | 200–400 | 61–122 | 0.002–0.006 in/tooth |
| Drilling | HSS/Carbide (135° split-point) | 50–80 | 15–24 | Pecking cycle >3x depth |
| Threading | TiN coated taps / thread mills | 30–50 | 9–15 | — |
Sawing, Plasma & Oxy-fuel Parameters
| Process | Parameter | Value |
|---|
| Band Sawing | Blade Speed | 150–250 SFM (46–76 m/min) |
| Band Sawing | Blade Pitch (plate > 1/4") | 4–6 teeth per inch |
| Plasma Cutting | Amperage (1/4" plate) | 45–65 amps |
| Plasma Cutting | Amperage (1/2" plate) | 80–120 amps |
| Plasma Cutting | Shop Air Pressure | 60–80 psi |
| Oxy-fuel Cutting | Preheat Time | 5–10 seconds per 1/4" thickness |
| Oxy-fuel Cutting | Cutting Speed (1/2" plate) | 12–18 in/min (305–457 mm/min) |
Depth of cut: up to 0.150" (3.8 mm) for roughing, 0.010–0.030" (0.25–0.76 mm) for finishing.
Common Defects & Quality Control
| Defect | Description | Quality Control Action |
|---|
| Mill Scale | Dark oxide layer causing weld porosity and poor paint adhesion | Remove by grinding, sandblasting, or pickling |
| Surface Laminations | Thin separations parallel to surface from gas pockets | Visible as silver streaks after grinding; inspect thoroughly |
| Edge Cracks | Small fissures on sheared edges from improper blade clearance | Check blade clearance; can propagate during bending |
| Camber | Lateral bowing along the length | Acceptable up to 1/4" per 5'; must be corrected for precision assemblies |
| Twist | Helical distortion | Reject if > 1/8" per 4' of length |
| Dishing | Concave/convex curvature across the width | Measure with straightedge and feeler gauge |
| Hard Spots | Localized areas of higher hardness (up to 200 HB) from uneven cooling | Monitor for tool chatter and poor surface finish |
| Rust / Pitting | Surface corrosion from improper storage | Acceptable if depth < 10% of thickness; remove by light grinding |
QC Inspection: Verify thickness with micrometer at four corners and center. Check flatness on granite table with feeler gauge. Perform spark test or portable hardness test (Leeb) on incoming material. For critical welds, request MTR (Mill Test Report) with heat number and chemical analysis.
Storage, Handling & Racking Guidelines
| Parameter | Guideline |
|---|
| Storage Environment | Indoors, dry, covered area to minimize rust |
| Rack Preparation | Use steel racking with wooden or rubber pads between sheets |
| Rack Capacity | Each shelf should support at least 2,000 lbs (907 kg) for 1/4" plate stacks |
| Stacking Orientation | Stack sheets flat, not leaning, to avoid permanent bowing |
| Max Stack Height (≤ 1/2" thick) | 4 feet (1.2 m) |
| Max Stack Height (> 1/2" thick) | 3 feet (0.9 m) |
| Handling (> 1/4" thick) | Use spreader bars and lifting clamps (e.g., 2-ton capacity) |
| Handling (small sheets) | Manual handling with gloves and sheet carriers for sheets < 4' x 4' |
| Long-term Storage (> 3 months) | Apply light coat of rust-preventive oil (e.g., LPS 3) and cover with breathable plastic |
| Inventory Rotation | FIFO (first-in, first-out) to prevent old stock from rusting |
Safety: Always wear cut-resistant gloves and steel-toed boots when handling. Use two-person lift for sheets longer than 6'. Do not drag sheets across each other to avoid scratching and edge damage.