Standard: ASTM B977-2011, AWSA5.16, AMS, MIL, ISO Material: Gr1, Gr2, Gr3, Gr5, Gr7, Gr9 and Gr12 Specification: Ø200 to 800mm, each weight is ≤6T Double and triple melting in vacuum-arc furnaces Quality inspection by ultrasonic detector Testing: accept the third party test, SGS