square erw steel tube Certification:ISO,CE Material:Q235,Q345 Standard:GB,JIS,ASTM Size:20*20-450*450 square erw steel tube 1. Standard: GB, ASTM, BS, DIN, API, JIS2. Grade: Q195, Q235, Q345, 20#,16Mn3. Size:20*20-450*450mm4.Wall thickness: 0.6mm-20.0mmQuality assurance1. Certification: ISO, CE, BV, MTC. 2. Inspection: third part inspection can be accepted.3. Test: Eddy current / hydrostatic/ ...