The invention discloses a mold structure for improving the inner and outer walls of a
pipe, comprising a core rod, a die and a heating ring, the core rod and the die are concentrically distributed, the die is located on the periphery of the core rod, a
discharge channel is formed between the inner periphery of the die and the outer periphery of the core rod, the end face of the die is fitted with the heating ring, the core rod comprises an extension portion exceeding the end face of the die, the extension portion is concentrically distributed with the core rod, the outer
peripheral wall of the extension portion comprises a flaring portion 1, the
diameter of the flaring portion 1 gradually increases from close to the die end to away from the die, the slope ɑ of the flaring portion 1 is 1.5-2 degrees, the
axial length L1 of the flaring portion 1 is 6.5-7 mm, the inner
peripheral wall of the heating ring comprises an inclined portion 1, the
diameter of the inclined portion 1 gradually increases from close to the die end to away from the die, the
diameter of the inclined portion 1 close to the die end is equal to that of the die, the slope b of the inclined portion 1 is 1.6-2.1 degrees, and the slope b of the inclined portion 1 is greater than the slope ɑ of the flaring portion 1. The die of the present invention does not accumulate precipitates, and the flatness of the inner wall of the product is improved.