FIELD: metallurgy, namely casting electroslag refining ingots for making large-size mandrels used for producing seamless hot rolled large- and mean-diameter tubes in tube rolling plants with pilger mills.
SUBSTANCE: method for making mandrel including lock, working and guiding portions comprises steps of casting electroslag refining ingot of heat- and wear-resistant steel; forging ingot to cylindrical forged billet with linear increase of forging reduction ratio from guiding portion to lock one; rough working of forged billet to mandrel blank; heat treatment of mandrel blank and finish working of it to mandrel. Bottom part of ingot is cast of steel with high resistance against friction and against increased percussion pressure. Mean part of ingot is cast of heat- and wear-resistant steel. Shrinkage head part of ingot is cast of steel with less heat resistance. Bottom part is cast in zone of 0.1 - 0.15 of total height of ingot; mean part is cast in zone of 0.5 - 0.6 of total height of ingot and shrinkage part is cast in zone of 0.30 -0.40 of total height of ingot. Lock portion of mandrel is made of bottom part of ingot; working portion - from mean part of ingot and guiding portion of mandrel is made of shrinkage part of ingot. In order to cast electroslag refining ingot, electrodes of steels having almost the same linear expansion factors are used; in order to make bottom and mean parts of ingot electrodes of steels subjected to the same heat treatment are used. Invention prevents crumpling of side faces, surfacing them with use of austenite electrodes and additional milling and therefore provides lowered cost of conversion of hot rolled tubes in tube rolling aggregates with pilger mills.
EFFECT: reduced cost of mandrels due to making guiding portion of them of steel having less heat resistance and less cost, improved strength of lock portion of mandrel due to casting bottom portion of ingot of steel having high resistance against friction and increased percussion pressure.
6 cl, 1 dwg
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