METHOD AND APPARATUS FOR CONTINUOUS THERMAL TREATMENT OF ELONGATED STEEL PRODUCTS Russian patent published in 2003 - IPC

FIELD: metallurgy. SUBSTANCE: method involves directing product through chamber comprising graphite of 0.5-1.8 g/cu.cm density, with following heating of product in non-oxidizing atmosphere under vacuum of 1-40 Pa to austenitic transition state; providing intensified cooling to bainite transition temperature range by withdrawing heat through graphite of 0.5-1.8 g/cu. cm density; providing plastic deformation at said temperature with following isothermal holding at temperature exceeding martensite transformation temperature; applying stretching force to product; cooling product to room temperature and withdrawing heat through graphite of 0.5-1.8 g/cu.cm density. Heating of product within phase transition temperature range is conducted at rate of at least 40 C/s and simultaneously elastoplastic deformation of product is performed with residual deformation less than 1%. Intensified cooling is performed at cooling rate of at least 200 C/s. Cooling and isothermal holding are provided in electromagnetic field created by means of electric potential supplied to product during heating, cooling and isothermal holding of product. Apparatus for continuous thermal treatment of elongated steel products has product stretching mechanism, sluice chambers, vacuumized heating, cooling and isothermal holding chambers filled with graphite material, product deformation devices and vacuumizer. Apparatus is further provided with detachable water cooled electric contact units, which may be vacuumized and filled with elastic variable density graphite. EFFECT: stabilized process parameters, improved quality of thermal treatment of steel product, reduced heating and holding time and improved mechanical properties. 3 cl, 1 dwg