A method and a device are provided for the thermomechanical treatment of seamless steel rings produced on radial-axial ring rolling machines, particularly rings of fine grain steel, heat-treatable steel, case hardened steel, or austenitic steel, preferably of steel tower flanges for wind turbine generators. The ring blank is inserted into the ring rolling machine at a temperature in the range of 900° C. to 1150° C. and is rolled to an outer diameter preferably in the range of 0.2 m to 10 m by a hot forming process. The hot ring (1) is quickly cooled down by a controlled process directly following the rolling, without secondary heating, from a temperature over the conversion temperature in the austenite range to a temperature below 400° C. The device includes a dipping basin filled with cooling liquid (8) or an unfilled cooling container, and a carrier (5) that can be lowered with a hoisting device (4), the rolled ring (1) lying on the carrier. Pressure nozzles (13) are arranged in the dipping basin or the cooling container (2) on one or several ring lines (11), in an equal distribution, for the targeted application of the cooling liquid (8) onto at least one of the ring-shaped surfaces of the ring (1). Measurement of the ring temperature before and/or after the cooldown is carried out, preferably, with a radiation pyrometer.

Method and apparatus for the thermomechanical treatment of seamless rings produced on radial-axial ring rolling machines

The prodn. of ring-shaped workpieces of hypereutectoid steel, which after hardening, contains low C martensite with a dislocation substructure, comprises cooling the hollow ingot, or a section of the ingot, obtd. by centrifugal casting, from the casting temp. to is not >100 degrees below the eutectoid transformation, and re-heating the casting to is not >100 degrees C. above the temp. of the eutectoid transformation. After a spheroidal pearlite structure is obtained, the temp. is raised to is not >1150 degrees C, followed by forming a semi-finished product, e.g. by rolling, and finally applying a hardening and annealing treatment. Method utilizes fully the thermal energy supplied by the centrifugal casting of the ring, being sufficient for the subsequent forming and heat treatment, which gives a saving in time.

Sommer K

Papers

Steel rings for bearings prodn. - by centrifugal casting with controlled cooling, and heating, followed by rolling to shape