Provided are an apparatus for manufacturing a compound powder, a method of manufacturing an iron-boron compound powder by using the apparatus, a boron alloy powder mixture, a method of manufacturing the boron alloy powder mixture, a combined powder structure, a method of manufacturing the combined powder structure, a steel pipe, and a method of manufacturing the steel pipe The method of manufacturing the boron alloy powder mixture includes: preparing a mixed powder including a boron iron alloy powder and a target powder; heat-treating the mixed powder to boronize at least a portion of the target powder and de-boronize at least a portion of the boron iron alloy powder, thereby de-boronizing the boron iron alloy powder to reduce the melting point of the boron iron alloy powder.