This invention relates to a process for producing a hollow cast product by the use of a hollow flexible mandrel in the crucible of a mold.
There have been proposed and practically employed a number of processes for producing hollow cast products and one of the prior art processes for producing hollow cast products employs a core in the crucible of the mold. However, since the prior art core employed in the process is formed of casting sand, gas generates during the production of a hollow cast product and such gas is required to be discharged by bending the core. If the gas discharge is insufficient, difficulties such as core blowing and formation of air cell honeycomb and/or casting honeycomb occur. In addition, it is quite difficult to produce a small diameter cast tube having a bent or meandering bore by the use of the core in the crucible of the mold.
The so-called centrifugal casting process which produces a hollow cast product by the utilization of centrifugal force produced in a mold without a core has been known. However, although this casting process eliminates the step of gas discharge because the process does not use the core, it is impossible to produce a hollow cast product having a bent or meandering bore.
Furthermore, in order to produce a small and uniform diameter hollow cast product such as a pipe product, the so-called draw mold and sweeping mold type casting processes have been proposed, but the processes require complicated production steps in the production of hollow cast products.
Furthermore, there has been also known the casting process in which a hollow cast tube is produced by the use of a metal pipe in the crucible of a mold, but this process has the disadvantage that a small clearance is formed between the tube being cast and the metal pipe.