Polyurethane high-density polyethylene prefabricated directly buried insulation pipe is also called polyurethane insulation pipe, polyurethane rigid foam prefabricated pipe, rigid polyurethane foam plastic prefabricated directly buried insulation pipe. Mainly made of spiral seam submerged arc welded steel pipes or seamless steel pipes, covered with high-density polyethylene outer protective pipes, and filled with hard polyurethane foam in the middle.