METHOD FOR CAST IRON HEAT TREATMENT WITH SPHERICAL GRAPHITE Russian patent published in 2012 - IPC C22C37/10 C21D5/00 

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, and namely to methods for cast iron heat treatment with spherical graphite. It can be used for obtaining items with improved performance. Cast iron containing the following components, wt %, is subject to heat treatment: carbon 3.0-3.4; silicone 1.8-2.3; manganese 0.3-0.5; nickel 0.6-1.2; molybdenum 0.3-0.7; copper 0.3-0.7; magnesium 0.04-0.09; sulphur 0.01-0.02; phosphorus 0.06-0.08; iron is the rest, at total ratio of alloying elements (Mn, Ni, Mo, Cu) in the range of 1.7-2.4%. The first cast iron normalisation is performed in the air at temperature of 940-960°C and exposure during 1.5-2.5 hours. The second normalisation is performed by heating to temperatures of 790-810°C at the rate of 100-200°C/hour, with exposure during 1.5-2.0 hours and cooling with pressurised air jet. After that, drawing is performed at 250-300°C with exposure during 2-4 hours.

EFFECT: obtained cast iron has fine-grain homogeneous microstructure, high plastic properties, impact strength and wear resistance.

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