The default "mild steel" bar stock in the US — 1018 cold-drawn is specified more often than all other carbon steels combined for general machined parts. Not as strong as 4140, not as machinable as 12L14, but widely available in every size from 1/8″ to 8″ round, square, and hex. Weldable, heat-treatable (case-hardening), and inexpensive.
Cheapest metal stock in most US/Asia distribution — typically 40–60% the cost of 4140 for the same section.
Low carbon content means standard MIG/TIG produces sound joints. No pre-heat or stress relief needed for sections under 25 mm.
Carburize to 0.8% surface carbon for 58–62 HRC wear surface on a tough core — used for gears, shafts, and wear plates.
| Element | Content |
|---|---|
| Iron | Balance |
| Carbon | 0.15–0.20% |
| Manganese | 0.60–0.90% |
| Phosphorus (max) | 0.04% |
| Sulfur (max) | 0.05% |
Composition per ASTM A108. Specific mill test reports (MTR) available on request for production orders.
1018 is cold-drawn bar with tighter tolerances and slightly higher strength. A36 is hot-rolled structural grade with looser chemistry bounds. For CNC parts, always specify 1018.
No inherent corrosion resistance. Black oxide, zinc plating, nickel plating, or paint required for most service environments.
Base hardness ~126 HB. To reach 30+ HRC, use 4140 or 4340 instead; 1018 cannot through-harden uniformly.
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