Phase-change non-destructive pipe expanding method for inner finned tube

The invention discloses a phase-change non-destructive pipe expanding method for an inner finned tube. The method comprises the following steps of: bending a copper heat exchange tube into U shape, removing greasy dirty on a surface and forming an oxidized layer on the surface; sleeving an aluminum alloy fin group on the copper heat exchange tube in series, welding all segments of the U-shaped copper heat exchange tube to obtain a loop, sealing the two ends of the copper heat exchange tube loop, and vacuumizing the inside of the copper heat exchange tube loop and pouring a liquid working medium in the copper heat exchange tube loop; and heating the copper heat exchange tube loop to 250 to 350 DEG C and keeping the temperature for 10 and 30 minutes, wherein the phase of the working medium changes to generate an inner pressure which drives the outer diameter of the copper tube expand to generate plastic deformation and therefore be compactly bonded with a tube hole on an aluminum alloy fin during the time. The method does not damage a finned groove structure of the inner wall of the copper tube, can obtain the characteristics of thin wall and slim and tall gear, can effectively improve heat exchange efficiency, is particularly favorable for expansion of elongated pipes, ensures the whole process is pollution-free, green and environmental-friendly, and can be applied in the fields of building heating, ventilation and refrigeration, microelectronic radiation and the like.