Steel A36-Hot Rolled Square Tube 4" x 4" x 0" wall Retail Price

About A36|The cheapest structural steel. A36 is specified by its mechanical properties (36,000 PSI minimum yield strength), not its chemistry, which means the carbon content can vary batch to batch. This inconsistency is fine for building bridges and I-beams but annoying if you're trying to machine it. Hot rolled A36 has mill scale, rough dimensions, and lower precision than cold drawn bar. It's harder to machine than 1018. It's not terrible, but it requires more power and you'll burn through inserts faster. Buy A36 when you need structural shapes (angles, channels, beams, plate) or when cost matters more than machinability. Buy 1018 when you need to actually machine the part. A common mistake is specifying A36 on a drawing that needs machining. Compare to 1018 (better for machining, tighter chemistry, costs more) and A36/GR50 (higher yield strength for structural applications).

About Square Tube|A hollow structural section (HSS) used for frames, supports, roll cages, and fabricated assemblies. It's mostly a cut-and-weld product, not typically used as machining stock.