초록 ▼

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 initi

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.

대표청구항 ▼

A method of manufacturing a plurality of ductile cast iron pipes which comprises the steps of: continuously centrifugally casting molten metal to form, within centrifugal casting molds, castings which ultimately form the ductile cast iron pipes; transporting the molds with the castings therein, one

A method of manufacturing a plurality of ductile cast iron pipes which comprises the steps of: continuously centrifugally casting molten metal to form, within centrifugal casting molds, castings which ultimately form the ductile cast iron pipes; transporting the molds with the castings therein, one at a time, while the castings are still in a red-hot state, to an annealing site; annealing the castings within the molds at a plurality of successively different heating zones including at least a first zone and a last zone by passing a hot gas of varying temperature through the castings within the mold such that the first zone has the highest temperature and the last zone the lowest temperature; successively transferring said molds from the first zone to the last zone in such a manner so as to slow down the dissipation of heat energies from the red-hot castings by the gradual reduction of the temperature in the heating zones, said variation in the temperature of the heating zones being effected by flowing the hot gas first through the hollow portion of the mold containing the casting in the red-hot state at the first zone and then successively into each of the hollow portions of said molds of lower temperature by means of telescopically extensible ducts connecting one mold with another so that the hot gas is gradually cooled as it passes from the mold in the first zone successively to the last zone, automatically clamping said telescopically extensible ducts onto the openings of the molds as the molds move into each heating zone so that all of the molds are connected in a row to form a closed system to permit the gas to pass therethrough; automatically removing said ducts from the molds when being transferred to the next successive zone; synchronizing said automatic clamping and removal of the telescopically extensible ducts with the movement of the molds from one heating zone to a heating zone of lower temperature so that clamping of the telescopically extensible ducts occurs When the molds are located at the heating zones and removed when the molds are transferred to the next heating zone, and; removing the castings so heat-treated from the mold in a continuous manner, thereby providing a plurality of ductile cast iron pipes.