WEAR RESISTANT TUBE AND METHOD OF THERMOCHEMICAL TREATMENT OF SUCH TUBE Russian patent published in 1995 - IPC

FIELD: tube production. SUBSTANCE: a wear resistant tube has inner and outer layers with ledeburite structure, a layer of low-carbon steel, placed in a center of the tube between the layers of steel with smoothly increasing hardness value and carbon content from the center of the tube in a range from hardness value and carbon content in the above mentioned layer of low carbon steel up to the values of these parameters in the ledeburite layer. A thickness of the inner and the outer wear resistant layers, having hardness no less, than 50 HRC, consists 0.1 of the tube wall thickness. The tube is being made from a steel blank by thermochemical treatment of the blank, comprising heating of that blank in a liquid hydrocarbon containing medium with constant temperature. Temperature of the blank heating is restricted by next limits T_l-70^°C<T_b<T_s-100^°C, where T_l - ledeburite melting temperature; T_b temperature of the blank; T_s temperature of melting of steel of the blank. A rotation number of the tube around its lengthwise axis is selected in range , where D an outer diameter of the tube, mm. EFFECT: enlarged using range of such tubes. 2 cl, 2 dwg