Hot Rolled Coil (HRC) is the benchmark for raw steel prices.
About SA234|ASME SA-234, the boiler and pressure vessel code version of ASTM A234. Same material and requirements. See A234 for details.
About Round Tube|Hollow cylindrical stock for sleeves, bushings, spacers, and hydraulic cylinders. DOM (drawn over mandrel) tubing machines well and holds tight tolerances. Welded-seam structural tube is for cutting and welding, not precision work.