WEAR-RESISTANT PIPE AND METHOD FOR ITS THERMOCHEMICAL TREATMENT Russian patent published in 1995 - IPC

FIELD: metallurgy. SUBSTANCE: wear-resistant pipe has internal wear-resistant layer of ledebutite structure, while external corrosion-resistant layer is of ferrite, and layer of low-carbon steel which is located in core of pipe wall between layer with monotonically increasing in layer of ferrite up to value equalling that in low-carbon steel and layer with monotonically increasing hardness in direction from core and carbon content within interval from value of hardness and carbon content in layer of low-carbon steel up to their value in layer with ledeburite structure. In this case, thickness of external layer of ferrite and thickness of internal layer of ledeburite structure and hardness of, at least 50 HRC equalling 0.01-0.1 thickness of pipe wall. To produce such pipe, its internal surface is heated with high-frequency currents in carbon-containing medium with the aid of outer circular inductor by its rotating round longitudinal axis. In so doing, pipe is heated up to temperature of its external surface at least 100 C being below the melting point of pipe steel, and internal surface temperature heated within interval ranging from +50 to -70 C of ledeburite melting point. Internal surface is heated in liquid carbon-containing medium with average temperature of medium inside pipe maintained at the level at which continuous steam-carbon-containing layer is formed on pipe internal surface, and soaking is carried out for time needed to form layer of ledeburite structure thickness equalling 0.01-0.1 of wall thickness. Pipe rotation speed is taken within , where n is rotation speed, rpm; D is outer diameter of pipe, mm. EFFECT: higher efficiency. 4 cl, 2 dwg, 5 tbl