Wire and arc additive manufacture of high-building multi-directional pipe joint

High-building multi-directional pipe joint is a complex structure. A novel technology, which is called wire and arc additive manufacture (WAAM), was used to manufacture a high-building 10-directional pipe joint in this paper. Because the intersecting areas of multi-directional pipe joint are space surfaces, the conventional planar slicing method of WAAM is hard to form space surface with high precision. According to the study of space surface slicing method and space path planning by WAAM, this paper used the outer cylinder surface of main pipe to slice other forming pipes of 10-directional pipe joint, and the intersecting surfaces could be divided into two kinds: smooth surface and curved surface with inflection point areas. Two different path filling schemes were proposed for different intersecting surfaces: The former was filled in rotating approaches, while the latter was filled in raster approaches. The dimensional errors of forming pipes were controlled about +/- 1 mm, and the angle errors of intersecting pipes were less than +/- 0.5A degrees. Compared with the properties of the casting pipe joint, the tensile strength of 10-directional pipe joint increased by 12.4% and the impact toughness (20 A degrees C) increased more than 100%. The microstructure mainly consisted of pearlite and ferrite, and average grain size was about 15 mu m. Rare defects such as pores and cracks were found.