... for ASTM A333, GR.A, GR.1, GR. 6 grade: A, GR.7, GR.3, specifications:1/ 4 ... 7the German standard DIN2448 /1629 seamless steel tubes, steel grade: St37, St44, St52, specifications: 1/ 4" -28 ... -1979: carbon structural steel, steel grade St35.8-St45.8/ I, St35.8-St45.8/ III 9 Structural use of seamless ... 1-70mm 11 Low and medium pressure boiler pipe steel grade GB3087-1999, 10, 20: # #, specifications: 6- ...