Abstract: An apparatus for heat-treating pipes comprising a furnace chamber for accommodating a plurality of pipes as arranged in parallel, a chain conveyor disposed in the furnace chamber for transporting the pipes in a direction at right angles to the axes of the pipes, and a plurality of stopper means for stopping the pipes intermittently at suitably spaced-apart positions in the path of transport by the chain conveyor and causing each of the pipes to rotate about its own axis in cooperation with the chain conveyor. Since the pipe is intermittently stopped and rotated about its own axis during heat treatment, the pipe is free of thermal deformation to an elliptical shape. Pipes can be heat-treated in succession in a small space, therefore with a very high efficiency. The motion of the chain conveyor is utilized for rotating the pipe without necessitating any additional device for the rotation.

Abstract: A heat-treating apparatus for practicing a method in which when red-hot iron pipes produced by a centrifugal casting machine are cooled, the pipes are slowly cooled over the temperature range of 800.degree. to 700.degree. C. to ferritize the pipes without separately annealing the pipes. A heat-treating furnace disposed close to one end of the rotary mold of the casting machine has furnace chambers each provided with pairs of rotatable rollers for supporting the pipe in rotation to prevent the deformation of the pipe. Each of the chambers has heating burners or a cooling heat exchanger for adjusting the temperature and cooling speed of the pipe placed in the chamber. According to a preferred embodiment, the furnace chambers are separated by openable partition members of circular-arc section, and each of the chambers has turnable levers for transferring the pipe to another chamber adjacent thereto.

Abstract: A method of heat-treating and, particularly, annealing, a ductile cast iron pipe in the form as centrifugally held against the wall of a centrifugal casting mold. The casting within the mold is heat-treated by introducing a hot gas of elevated temperature into the hollow of the casting. At the initial stage, the casting within the mold is in red-hot condition and, therefore, introduction of the hot gas into the hollow of the casting results in control of the dissipitation of heat energies from the red-hot casting to delay or slow down a cooling rate of the casting.