Abstract: A method for detecting a molten metal surface level in a casting mold, comprises inserting an electrode in a slag constituting a layer under a flux floating on the surface of the molten metal, detecting a change of electric resistance due to a temperature gradient of the place at which the electrode is inserted, displacing the electrode to bring the detected value to be always constant within a range of from 5 to 50 .OMEGA., and measuring the degree of the displacement of the electrode thereby detecting the surface level of the molten level. An apparatus for carrying out the method is also disclosed.

Abstract: Disclosed is a method and apparatus for cold-working annular workpieces by applying thereto an internal fluid pressure to cause an enlargement of the diameter thereof through plastic deformation, in which the openings at opposite ends of an annular workpiece are closed by a pair of presser plates through packings which are radially expansible along with the annular workpiece. The contacting surface pressure of the packings and presser plates are controlled to a predetermined value by an arithmetic unit operating on detected values of a main pressure acting internally on the annular workpiece, an auxiliary pressure pressingly holding the presser plates against the respective packings and varitions in the shape of the annular workpiece undergoing the plastic deformation.