REFINING OF THE CrNiMo STEEL

Abstract

A quality of forgings of large dimensions with diameter 350 mm and length 8500 mm of a bar profile are described. The forgings are made of ingots of mass approximately 6 tons. Steel is melted in the electric furnace of volume 15 tons of molten steels. About 18 tons of steel can be reduced in the furnace using enforce and from this amount four ingots are molten by casting process. The forgings are used for special technology in weapon systems, thus a product is combined stressed mainly by high pressure, impact and temperatures. Medium alloyed steel is suitable for these conditions and for mechanical properties higher requirements are imposed. The lowest magnitude of lower yield point, contraction and impact strength are appointed. Molten ingot is forged by a hydraulic press. After flattening giving a shape of bar forging and its heat treatment follows take of samples for determination of mechanical properties. Their results often didn't achieve standard parameters. Technical conditions allow to make a forgings on the heat treatment maximum twice. Forging was disabled such a defective work because of deficient mechanical properties after heat treatment adaptation. More than twelve per cent forgings from a whole year production was disabled y this way and coefficient of heat treatment adaptation was K = 1.7. A substantial turnover in the quality of investigated steels was enabled due to technology of refinement which is designated as the elecroslag remelting (thereinafter ESR).