METHOD FOR MAKING STRUCTURAL STEEL OF REDUCED AND SPECIFIED HARDNESS PENETRATION Russian patent published in 2012 - IPC C21C5/00 C21C7/00 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, and namely to steel making with reduced hardness penetration (RHP) and specified hardness penetration (SHP) in electric arc-type and induction furnaces and basic-oxygen converters. Loading is performed to electric arc or induction furnace or converter of metal charge form iron-carbon alloy, metal junk with specified content of magnesium, silicon, chrome, nickel, copper in them, which provides final content of each of them of not more than 0.1 wt %, for RHP steels and not more than 0.3 wt % for SHP steels, graphite, slag-forming components, melting, heating of bath to the temperature of finishing beginning; finishing of molten metal as per carbon content with further carbonisation in ladle or furnace-ladle; after that, deoxidation of molten metal is performed in ladle or furnace-ladle by means of aluminium in quantity of 1.0-2.5 kg/t, titanium, vanadium and nitrogen; at that, 0.3-0.5 of total amount of aluminium is loaded to bottom of ladle or furnace-ladle, and the rest is loaded to the jet till not less than 0.3 of volume of ladle or furnace-ladle is filled, and titanium, vanadium and nitrogen is loaded after the whole aluminium is introduced so that content of carbon 0.3-1.5 wt %, aluminium 0.03-0.10 wt %, titanium 0-0.4 wt %, vanadium 0-0.4 wt % and nitrogen 0-0.15 wt % is provided in finished metal.

EFFECT: invention allows obtaining higher mechanical properties and stable hardness penetration characterised with ideal critical diameter, and higher mechanical properties of RHP and SHP steels.

5 cl, 3 ex