CONTROL METHOD OF STRUCTURAL STATE OF HARDENED LOW-CARBON STEELS Russian patent published in 2013 - IPC G01N1/32 G01N33/20 

FIELD: metallurgy.

SUBSTANCE: first, a specimen of rectangular shape is made; a bevelled cut is made on the specimen at an angle of 15-25° from lower base to upper one, thus taking specimen length as the base. Then, surface of the bevelled cut of the specimen is ground and an austenisation mode is performed in oxidation atmosphere by etching gas. The specimen is cooled in water or in the air; then, a microslice or a series of microslices is prepared on surface of small base of the specimen, thus grinding the layers parallel to large base of the specimen. Depth of decoration zone is measured by etching gas on microslice by means of a microscope; then, the investigated surface of microslice is etched with alcohol solution of nitric acid till boundaries of austenitic grains are determined; determined boundaries of austenitic grains are studied; depth of selective determination zone of boundaries of austenitic grains is determined, and the defined etching picture is photographed. As per investigation results of microslice surface, structural state of the specimen is evaluated step by step: first, decoration zone of structure by oxidation with etching gas, then, selective etching zone of actual boundaries of austenite grains, and finally, zone of simultaneous detection of boundaries and intra-grain structure of the investigated steel; then, full depth of penetration of etching gas to the investigated material is determined by summing depths of decoration zone with etching gas and zone of selective detection of boundaries of austenite grains at etching of microslice and multiplication of the obtained value by cosine of inclination angle of bevelled cut to the large base.

EFFECT: simpler detection of boundaries of actual austenite grain; providing complex evaluation of structural state of hardened steel with possibility of multiple layer-by-layer investigation of slices by simultaneous fixation of oxidation zone of the investigated steel, zone of selective detection of boundaries of actual austenite grain and zone of intra-grain structure on slice surface.

7 dwg, 2 tbl