Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: A method in accordance with the present application includes sending a raw tube from a drum to an unwinding side capstan while the raw tube is rotated around a central axis perpendicular to a winding shaft of the drum by rotating the drum and the unwinding side capstan about the central axis concurrently with unwinding of the raw tube from the drum holding the raw tube, on an inner surface of which multiple straight grooves along a longitudinal direction of the raw tube are formed with an interval in a circumferential direction, in a coil shape, to wind the raw tube around the unwinding side capstan, and drawing in which the unwound raw tube is drawn while the diameter of the raw tube is reduced, and then the raw tube is wound around the drawing side capstan to twist the raw tube and obtain an inner spiral grooved tube.

Abstract: The present invention provides a die casting magnesium alloy having excellent heat resistance and castability, and the alloy of the present invention is a die casting magnesium alloy having excellent heat resistance and castability, comprising 2 to 6% by weight of Al, 0.3 to 2% by weight of Ca, 0.01 to 1% by weight of Sr, 0.1 to 1% by weight of Mn, the balance magnesium and unavoidable impurities. According to the present invention, more excellent effects can be obtained in the composition wherein rare earth elements are added to the composition described above.

Abstract: The present invention provides a die casting magnesium alloy having excellent heat resistance and castability, and the alloy of the present invention is a die casting magnesium alloy having excellent heat resistance and castability, comprising 2 to 6% by weight of Al, 0.3 to 2% by weight of Ca, 0.01 to 1% by weight of Sr, 0.1 to 1% by weight of Mn, the balance magnesium and unavoidable impurities. According to the present invention, more excellent effects can be obtained in the composition wherein rare earth elements are added to the composition described above.