| 摘要 |
<p>The present invention relates to a dual coating of an external diameter, a method for manufacturing a steel pipe having an epoxy coating resin layer coating an internal diameter and the external diameter at once. The method for manufacturing a steel pipe includes: a ceramic mixture processing step (S10) of processing hornblende and sphalerite into sizes of 200-600 mm individually; a ceramic mixture mixing step (S20) of mixing the processed hornblende and sphalerite; a jade processing step (S30) of pulverizing jade; a surface treatment step (S40) of removing foreign substances scattered in a steel pipe (20) with short blasting; a preheating step (S50) of heating the steel pipe (20) treated in the surface treatment step (S40) with a gas torch of a heating device (40); and a step of coating an epoxy coating layer (22), an adhesive resin layer (23), and a polyethylene coating layer (24) on the external diameter of the pre-heated steel pipe (20) and an internal epoxy coating layer (25) on the internal diameter.</p> |
