A36 vs 1018 Steel: Structural Plate vs Precision Bar

## How They Are Specified **A36 (ASTM A36)** is a structural steel specified by minimum mechanical properties: 250 MPa minimum yield strength and 400-550 MPa tensile strength. The composition is loosely defined (0.26% C max). **1018 (AISI 1018)** is specified by composition: 0.15-0.20% carbon, 0.60-0.90% manganese. Mechanical properties depend on the delivery condition (hot-rolled vs cold-drawn). | Property | A36 (Hot-Rolled) | 1018 (Cold-Drawn) | |----------|-----------------|-------------------| | Tensile Strength | 400-550 MPa | 440 MPa | | Yield Strength | 250 MPa (min) | 370 MPa | | Elongation | 20% | 15% | | Carbon | 0.26% max | 0.15-0.20% | ## Product Forms and Surface Finish A36 is supplied as hot-rolled structural shapes (W beams, channels, angles), plate, and bar. The surface has mill scale, and dimensional tolerances are relatively loose per ASTM A6. 1018 cold-drawn bar has a smooth, bright surface finish with tight dimensional tolerances. It is ready for precision machining directly from the supplier. ## Machinability 1018 cold-drawn machines well with consistent chip formation and good surface finish. A36 can be machined but the variable composition and hot-rolled condition make it less predictable. ## Heat Treatment 1018 can be case-hardened by carburizing to produce a hard surface (58-62 HRC) over a tough core. A36 is not normally heat treated due to its variable composition. ## Cost A36 hot-rolled plate costs approximately 0.70-1.00 USD/kg. 1018 cold-drawn bar costs approximately 1.00-1.50 USD/kg, reflecting the cold-drawing process and tighter tolerances. ## When to Choose Each **Choose A36 when**: The application is structural (buildings, bridges, frames), loads are defined by yield strength, the fabrication method is cutting and welding, and cost matters. It is the default choice per AISC specifications. **Choose 1018 when**: The part requires precision machining, tight tolerances, good surface finish, or case hardening. Common applications include shafts, pins, bushings, spacers, and custom-machined components.