METHOD OF PRODUCTION OF SEAMLESS PIPES OF LARGE DIAMETER OUT OF STEELS WITH INCREASED COEFFICIENT OF LINEAR EXPANSION Russian patent published in 2003 - IPC

FIELD: production of seamless hotrolled pipes of large diameter out of steels with increased coefficient of linear expansion; possibly, production of seamless hot-rolled pipes in pilger mills. SUBSTANCE: method of production of seamless hotrolled pipes of large diameter out of steels with increased coefficient of linear expansion incorporates heating of billet, piercing and rolling in pilger mill between rolls with round pass equal to D_p = D_N(1+αt)[1+4α(t-t1)] with reduction of distance between flanges of rolls after setting on mandrel by the following value:Δ = 4D_Nα(1+αt)(t-t1), where D_n is nominal diameter of rolled pipes, mm; α - is coefficient of linear expansion; t is shell temperature at the beginning of rolling, C; t1 is temperature of pipe end at the moment of withdrawal from mandrel, C . EFFECT: this method allows jamming of mandrels during rolling to be eliminated and metal consumption coefficient to be reduced owing to reduction of longitudinal variation in wall thickness during production of pipes in pilger mills.