Lost foam for casting cast iron pipe

The utility model relates to an evanescent mode for casting a cast iron pipe, which comprises extension sections, a middle section, a positioning identification block, a slot and a connecting sleeve, the extension sections aligned with the base section are arranged at the end parts of the base section, the middle section is arranged between the extension sections and the base section and is respectively aligned and contacted with the extension sections and the base section, and the positioning identification block is positioned in the slot. The outer side wall of the middle section is uniformly and fixedly connected with a plurality of groups of positioning identification blocks, the plurality of groups of positioning identification blocks are inserted into slots formed in the connecting sleeves and are fixedly clamped with the slots, and the connecting sleeves positioned on the two opposite sides of the middle section respectively sleeve the extension section and the basic section and are fixedly connected w