Method for manufacturing a tube fitting

A method for manufacturing a tube fitting (1A;

• 1B) that is capable of coupling a tube (BT) made from metal and provided with an annular portion (16;
• 26) upon an end portion thereof, to a mating member (MC1;
• MC2) by being installed upon an external periphery of the tube (BT) and by being fastened to the mating member (MC1;
• MC2) in a state of contacting the annular portion (16;
• 26), the annular portion (16;
• 26) projecting in a radially outward direction from the tube (BT),
• the method comprising:
• a preparation step of preparing the tube fitting (1A;
• 1B);
• and
• a coating step of forming a resin coating layer (18;
• 28) upon a coated region (R) provided upon the surface of the tube fitting (1A;
• 1B);
• wherein:
• the coating step comprises a dipping step of dipping the tube fitting (1A;
• 1B) into a coating material (C1 to C4) that includes as components a polyethylene based substance, a lubricant, and solid particles and having viscosity within a range of 4.24 to 5.27 mPa·s at 25° C. measured using a rotational viscosimeter conforming to the ISO 2555:1990 standard with a rotational speed of a spindle of the rotational viscosimeter set to 60 rpm, and adhering the coating material (C1 to C4) to the coated region (R), and a drying step of, after the dipping step, drying the coating material (C1 to C4) which is adhered to the coated region (R) of the tube fitting (1A;
• 1B);
• and
• in the dipping step, with mass per unit area w (g/m2) being defined as being a value obtained by dividing a mass difference between a state with the resin coating layer (18;
• 28) and a state without the resin coating layer (18;
• 28), the mass per unit area w is controlled within a range 0.79<w<10.07 by dipping the tube fitting (1A;
• 1B) while regulating a temperature of the coating material (C1 to C4) within a range of 30° C. to 40° C.