TUBE WITH SPIRAL GROOVE ON INNER SURFACE, MANUFACTURING METHOD THEREFOR, AND HEAT EXCHANGER

摘要

PROBLEM TO BE SOLVED: To provide a tube with a spiral groove on an inner surface capable of preventing occurrence of orange peel and excellent in surface and inner surface properties, a manufacturing method therefor, and a heat exchanger.SOLUTION: The present invention provides a method of manufacturing a tube with a spiral grooved inner surface, including: manufacturing a tube with a spiral grooved inner surface or an extruded stock tube by forming a plurality of straight grooves along a length direction on an inner surface at a distance in a circumferential direction, processing an aluminum extruded stock tube having a fin formed among these straight grooves into a coil shape, extending the stock tube to twist the tube material, and drawing the stock tube; reducing a diameter of the tube with the spiral grooved inner surface or the extruded stock tube in a diameter reduction portion of a drawing dice and drawing the tube while twisting the tube before entering the drawing dice; and simultaneously performing drawing and twisting. A mean crystal grain size of the obtained tube with the spiral grooved inner surface after annealing is equal to or less than 120 μm, and a mean crystal grain size of the extruded stock tube used for manufacturing is equal to or less than 80 μm.