Combined steel pipe necking die easy to disassemble and assemble

The invention discloses a combined steel pipe necking die easy to disassemble and assemble, which is arranged on a top head of a necking machine and comprises an outer layer assembly arranged on the top head, a middle layer assembly arranged on the outer layer assembly and an inner layer assembly arranged on the middle layer assembly, the outer layer assembly comprises a plurality of first blocks which are arranged in the same way; the middle-layer assembly comprises a plurality of second blocks which are arranged in the same way; the inner layer assembly comprises a plurality of third blocks which are arranged in the same way; the first blocks, the second blocks and the third blocks are the same in number; the inner-layer assembly is provided with necking structures of multiple specifications, wherein the outer diameters of the steel pipes are gradually reduced. The die is designed based on a stamping type necking machine, is divided into multiple sets of parts and can be rapidly assembled and disassembled,