Carbon steel is strong, weldable and inexpensive, which makes it the default for structural and general fabrication. Its weakness is corrosion — bare steel rusts — so a protective finish is part of the spec, not an afterthought.
Common grades
| Grade | Type | Yield (MPa) | Heat-treatable | Typical use |
|---|---|---|---|---|
| Q235 / A36 | Structural mild | ≈ 235–250 | No | Frames, brackets, weldments |
| SPCC | Cold-rolled sheet | ≈ 195–280 | No | Formed sheet-metal parts |
| 1045 | Medium carbon | ≈ 310–450 | Yes | Shafts, gears, pins |
| 4140 | Alloy steel | ≈ 415–655 (Q&T) | Yes | High-strength machined parts |
Always specify a finish
- Powder coat or paint for general indoor/outdoor parts.
- Zinc plating or galvanizing where coating thickness must stay thin.
- Black oxide for tooling and a low-glare finish.
For corrosion resistance without coating, compare stainless or aluminum.