METHOD FOR MAKING CAST IRON TUBES Russian patent published in 1999 - IPC

FIELD: metallurgy, namely processes of deformation-heat treatment of iron-carbon alloys, possibly manufacture of extruded tubes of spheroidal graphite cast iron for transporting water, oil products and gases. SUBSTANCE: method comprises steps of using spheroidal graphite cast iron sleeve; heating it up to temperature equal to Ar3 + (30-370)C; extruding it through die with use of mandrel at elongation degree 2-50; subjecting it to heat treatment according to next schedule: at first heating until 650 C - 950 C for 0.2-30 hours and cooling. Tube is cooled until 100 C - 300 C at rate 7-90 C/h. EFFECT: enhanced corrosion resistance and mechanical properties of cast iron tubes. 3 cl, 2 tbl