... 40"6. Type:Slip-on flanges, Blind flanges, Lap joint flanges, Welding neck flanges,Plate flange,7. Socket welding ... process : raw material--cutting--heating--forging--heat treatment--maching--inspection.11. Mill ceitificate :3.1B12. Certificate:TUV13. ISO certificate ... the third party.18. Used for : petroleum,chemical,power,gas,water,linepipe, heat exchanger,shipbuilding,construction,etc.19. Tolerance ...