METHOD FOR MAKING CONVERSION CAST IRON AND TECHNICAL-GRADE TUBES FROM CENTER-DIE CAST HOLLOW BILLETS OF HARD-TO-FORM STEELS AND ALLOYS

摘要

FIELD: rolled tube production, namely manufacture of conversion cast iron and technical-grade tubes with mean- and large-size diameters of center-die cast hollow billets of hard-to-form steels and alloys, possibly in tube rolling plants provided with pilger mills.;SUBSTANCE: method comprises steps of heating in furnaces at different rate hollow billets with diameter 300 - 650 mm until plasticity temperature; tilting them along furnace and rolling in pilger mills; holding billets with relation D/S in range 4.0≤D/S≤7.5 without tilting in tail part of furnace on grates at temperature 400 -480 C for 50 - 60 min depending upon relation D/S; heating billets up to temperature 800 -850 C at rate 1.6 - 1.8 C/min and then up to temperature 1150 -1200C at rate 2.5 - 2.7 C/min at tilting them in 15 - 20 min by angle 90 degrees ≤α≤ 180 degrees. Rolling process in pilger mill is realized with elongation factor μ≤5.0. Total period of heating center-die cast billets in heating furnaces is determined with use of relation 6.0≤t_h≤9.0 where t_h-heating time period in range 6 - 9 hours depending upon value D/S.;EFFECT: enhanced quality of tubes, lowered metal consumption, enlarged assortment of tubes of hard-to-form steels and alloys.;2 cl, 1 tbl