METHOD FOR MAKING TUBES OF HARD-TO-FORM KINDS OF STEELS AND ALLOYS WITH INCREASED LINEAR EXPANSION FACTOR Russian patent published in 2004 - IPC

FIELD: rolled tube production, namely processes for making tubes of hard-to-form kinds of steels and alloys with increased linear expansion factor, possibly in tube rolling plants with pilger mills. SUBSTANCE: method comprises steps of rolling sleeves and hollow billets heated until ductility temperature to tubes in pilger mill on mandrels at periodic batch feed of tube to deformation zone; rolling away sleeve-tube by means of rolls at using friction forces; extracting mandrel out of tube at rolling process termination by means of feeding apparatus; performing afterrolling of sleeve or hollow billet and rolling out of pilger head during rolling away sleeve-tube by means of rolls and simultaneously extracting mandrel by means of feeding apparatus. Effort for extracting mandrel by means of feeding apparatus is applied at time period of afterrolling sleeve and rolling out pilger head by value consisting 0.5 -1.2 of sleeve diameter. At one feed and rolling away procedure, mandrel is extracted from sleeve-tube by means of feeding apparatus by value consisting 0.5 - 1.0 of feed value of sleeve to deformation zone. Invention provides increased strength of mandrels due to elimination of their curving at heating until temperature almost equal to 700 C. EFFECT: elimination of jamming mandrels at rolling, lowered metal consumption due to reduced lengthwise wall-difference of tubes, increased strength of mandrels due to lowered lengthwise thickness- difference of tubes, lowered loads of roll and drive unit of pilger mill, prevention of possibility of breaking rolls and spindles, enlarged assortment of tubes. 3 cl, 1 tbl, 1 ex