STRENGTHENING METHOD OF ITEMS FROM LOW-CARBON STEEL Russian patent published in 2015 - IPC C23C8/66 C23C8/80 C21D1/78 

FIELD: metallurgy.

SUBSTANCE: invention relates to steel items carbonization, and can be used for surface hardening of machine an machinery parts out of low-carbon steel. Items are carbonized in solid carburizing compound, then they are cooled, subjected to double hardening and low-temperature tempering. The carbonization is performed at 900°C. The following compound is used as solid carburizing compound, containing in wt %: cast-iron shaving with average grains size 0.5 mm - 10, barium carbonate BaCO₃ - 10, and carbonic substance with fibrous structure - 80 comprising in wt % iron - 10, hydrogen - 0.8, and carbon - 89.2, that is produced by catalytic thermal pyrolysis of the associated petroleum gas of Bayadynskoe Field under contact with iron oxide catalysts at temperature 660°C, with feed space velocity 1000 hours^-1 for 3 hours with further screening of the fraction 100-250 micron by fractionation of the created mass in molecular sieves. After carbonization the items are cooled to 100°C, then subjected to double hardening including first hardening at 820°C, and second hardening at 770°C, then low tempering is performed at 150°C.

EFFECT: required diffusion saturation by carbon is ensured, uniform depth of the layer over the item is ensured, reduced power consumption, and reduced needed in cooling by water solution of the cooling liquid and emulsifier addition.

3 tbl