... fittings (HBT30 40 60 80 100),high-and-low-pressure pipes have materialsQ23520#16MnST5237Mn5, siphon, adjustable tube, precision steel tubes card 3 ... import super-audio heat treatment equipment,all selects 45Mn2 high Mn alloy tube, after heat treatment, Rockwell hardness is up to 58 ...