RECONDITIONING OF PILGER MILL MANDREL USED FOR HOT ROLLED 273-550 mm-DIA PIPES MADE OF "25-2¦1L"-GRADE STEEL WITH INITIAL SURFACE SORBITE PLY DEPTH OF 40-50 mm Russian patent published in 2015 - IPC B21B21/00 

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. This process comprises reconditioning of operating mandrel composed of 5-6 mandrel units at mill to first reconditioning to smaller size, 4-6 units to second reconditioning to smaller size, 3-4 units to third reconditioning to smaller size and 4 units before withdrawing of mandrel from operation. Note here that reconditioning to smaller size is performed unless separate perlite section originate in sorbite ply structure Note also that first reconditioning is made after reaching the mandrel durability of 0.75-0.80 of their mean initial durability Second reconditioning is effected after reaching 0.5-0.55 of their initial mean durability Third reconditioning is made after reaching 0.30-0.35 of mean initial durability with increase in metal diametral removal at every next reconditioning, scale removal and grinding before fitting at said mill.

EFFECT: decreased specific consumption of mandrels per ton of rolled pipes, lower costs.

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