METHOD FOR PREPARING CENTRIFUGALLY CAST BILLETS OF HARD-TO-FORM STEELS AND ALLOYS TO TUBE ROLLING

摘要

FIELD: rolled tube production, namely preparation of centrifugally cast billets of hard-to-form steels and alloys to further hot rolling of seamless tubes in tube rolling plants having pilger and automatic mills.;SUBSTANCE: method comprises step of mechanically working, namely turning and boring of cast billets by value depending upon their wall thickness and diameters; increasing layer removed by turning as wall thickness increases and lowering such layer as diameter of cast billet increases; determining value of removed layer according to expression: Δ S = S x (K1 - K2 x D/S), where Δ S -value of removed metal layer at turning billets, mm; K1 - coefficient directly lowering from 0.0175 until 0.0165 as wall thickness increases from 30 up to 100 mm; K2 - coefficient directly increasing from 0.075 up to 0.0125 for billets with diameter 100 - 300 mm and from 0.009 until 0.013 for billets with diameter 350 - 600 mm.;EFFECT: enhanced efficiency of process due to eliminating operations for cutting off rings and for rejecting billets according to macrostructure of rings without sufficient proof, lowered metal consumption at conversion of centrifugally cast billet to hot rolled tube, lowered cost of hot rolled tubes of hard-to-form steels and alloys.;2 cl, 2 tbl