A.GB1499.1-2008 B.GB1499.2-2007 C.GB/T701-2008 D.GB/T701-1997
A.2D B.3D C.3A D.2A
A.550N/mm2;4.5% B.540N/mm2;10% C.550N/mm2;10% D.500N/mm2;10%