METHOD OF DETERMINATION OF THE CRITICAL TEMPERATURE OF STEEL BRITTLENESS BY THE CROSS SECTION OF THE WALL OF THE OBJECT Russian patent published in 2018 - IPC G01N19/08 G21C17/00 

FIELD: chemistry.

SUBSTANCE: invention relates to the chemistry, petrochemistry and oil refining, vessels, apparatus and pipelines operated under pressure, as well as to pipeline transport, namely to overhaul and reconstruction of pipelines, in particular to determining the technical condition and service life of pipelines subjected to hydrogen during operation corrosion and deformation aging. After operation, by perforating the object wall using a core bit, the macro-sample of the object wall is divided along its axis of symmetry on sections of the same or different length, having minimum values in the axial zone of the macro-test and/or the zone adjacent to the surface of the clad wall of the object or to the outer surface of the object wall, and micro-samples corresponding to each site are obtained, hardness of the outer surface of the object wall in the initial state and the microprobe of each section of the wall of the object after operation are measured. At brittle fracture temperatures, tests are performed on the impact bending of specimens of the object and micro-samples obtained from each section of the macro-sample of the object wall, with the formation of zones of crystalline fracture. An electron-fractographic analysis of the steel samples of the object in the initial state and micro-samples obtained from each site of the macro-sample of the wall of the object after operation is carried out, and the reduced fractions of the intergranular destruction are determined. Micro-sample with the maximum intergranular destruction is successively subjected to grinding, polishing, etching in a 3 % solution of picric acid, determine the size of d_fo each facet of intergranular destruction and d_go each grain of ferrite by dependencies. Determine the critical temperature of the brittleness of the sample of the object in the initial state for each section of the macro sample and determine the critical temperature of brittleness in dependence. Establish the dependence of the increment of the critical temperature of brittleness of steel due to hydrogen embrittlement, increments in the critical temperature of brittleness of steel due to deformation aging and the critical temperature of brittleness of steel from the length of the macro-sample of the wall of the object after operation, and the critical temperature of brittleness of the steel of the object that has passed operation is assumed to be equal to the value of the maximum critical temperature (T_c)_max, selected on the set of all sections of the macro-sample of the object.

EFFECT: method is proposed for determination of the critical temperature of brittleness of steel along the cross-section of the object wall.

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