... E235, E255,E355, St37.4, St35 Phosphate coated hydraulic tube Phosphate coated hydraulic tube 1) Certificate: ISO9001:2008, ISO/TS16949:20092 Spec ... are from Xingcheng special steel and Baosteel Corp, the whole tube processing is conducted rigidly according to ISO9001 quality system, ... oxygen free annealing is adopted for heat treatment, which ensure tube surface is smooth, no any scales on inner and ...