METHOD OF THERMOCHEMICAL TREATMENT OF PIPE INTERNAL SURFACE OF LOW-CARBON STEEL Russian patent published in 1997 - IPC

FIELD: thermochemical treatment of steel products, mainly, thermochemical treatment of steel pipe internal surfaces operating under conditions of abrasive wear. SUBSTANCE: the offered method includes heating of products kept in vertical position, diffusion saturation of internal surface at temperature of 980-1150 C in the atmosphere of nondiluted natural gas with addition of 10-20% of ammonia, slow cooling of pipe together with furnace down to temperature of 780-850 C, hardening and low-temperature tempering. Besides, treated products are suspended in vertical position with stretching axial forces applied to them. EFFECT: higher efficiency. 3 cl, 1 tbl