Heat treatment method for X60Q line pipe with steel pipe wall thickness larger than 25 mm

The invention discloses a heat treatment method for an X60Q line pipe with the steel pipe wall thickness larger than 25 mm. The heat treatment method comprises the following steps that (1) the carbon equivalent CEIIW in steel is smaller than or equal to 0.43; (2) the temperature of a heat preservation section of the seamless steel pipe is heated to 910 +/-10 DEG C, and heat preservation is conducted for 4-6 min; 3) taking the seamless steel pipe out of a quenching furnace for water quenching heat treatment; (4) the seamless steel pipe is heated to 650 +/-10 DEG C for soaking and heat preservation, the total time from heating to heat preservation is controlled to be 140 minutes, and the furnace temperature is controlled to be +/-10 DEG C; and (5) after tempering heat treatment is finished, the seamless steel pipe is discharged and air-cooled. According to the method disclosed by the invention, various mechanical properties of the steel pipe meet the following requirements: the yield strength is 450-600MPa; the