TUBE FROM HIGH-CARBON STEEL WITH EXCELLENT PROCESSABILITY IN COLD STATE, PROCESSABILITY AND HARDENABILITY AND ITS MANUFACTURING METHOD Russian patent published in 2016 - IPC C22C38/06 C22C38/38 C21D9/08 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to production of tubes from high-carbon steel. Method of making tubes from high-carbon steel includes production of high-carbon steel as initial tube from steel containing, wt%: from 0.25-0.60 of carbon, from 0.01 to 2.0 of silicon, from 0.2 to 3.0 of manganese, from 0.001 to 0.1 of aluminium, from 0.001 to 0.05 of phosphorus, from 0.0001 to 0.02 of sulphur, from 0.0010 to 0.0100 of nitrogen, from 0.0003 to 0.0050 of boron, from 0.0001 to 0.0050 of calcium, iron and casual impurities making rest. Initial pipe is heated and maintained at temperature conversion of Ac₃ or higher, is subjected to reduce-stretching rolling at temperature of finish rolling from 900 °C to temperature conversion of Ac₁ with total reduction in diameter of 30 to 70 % in temperature range from 900 °C or lower. This enables to generate microstructure contains phase of ferrite and cementite grain dispersed therein without annealing, which has average grain size d from 0.1 to less than 0.5 mcm and average distance L between surfaces of adjacent cementite grains from 0.5 to 10 mcm.

EFFECT: steel pipe is characterised by high machinability in cold state, processability.

8 cl, 3 tbl, 30 ex