Cast iron flanges are cast in grey iron СЧ20 to GOST 1412 or ductile iron ВЧ50 to GOST 7293; the grade is stated in the lot certificate together with HB hardness and mechanical test results. Geometry is checked against the GOST 33259-2015 tables: outside diameter, bolt circle, number and diameter of holes, thickness and raised face height. Castings are inspected for blowholes and sand burn-in before machining, and the sealing face is machined to Ra 3.2.
Cast iron is brittle, so packing differs from steel: each flange sits on a cushion, edges are protected, and the lot ships in wooden cases or strapped pallets rather than bags. Marking goes on the tag and on the face — DN, PN, iron grade, lot number — so the item on site can be traced back to its certificate. The container loading plan is agreed before shipment to avoid chipping in transit.