This standard specifies the type and size of integral steel pipe flanges with concave and convex surfaces with nominal pressure PN of 1.6, 2.5, 4.0, 6.3, 10.0, 16.0MPa and nominal pressure PN of 5.0, 11.0, 15.0 and 26.0MPa. This standard is applicable to integral steel pipe flanges with concave and convex surfaces with nominal pressure PN1.6~PN26.0MPa.