PROCEDURE FOR MANUFACTURE OF COLD RESISTANT FLAT Russian patent published in 2011 - IPC C21D8/02 C22C38/08 

FIELD: metallurgy.

SUBSTANCE: for manufacture of flat of 10÷70 mm thickness with upgraded indices for resistance to brittle fracture at low temperature there is melted steel containing wt %: carbon - 0.06-0.12, manganese - 0.60-1.20, silicon -0.15-0.35, nickel - 0.05-0.40, aluminium - 0.02-0.05, molybdenum - 0.003-0.08, titanium 0.002-0.02, niobium - 0.02-0.06, vanadium - 0.02-0.05, nitrogen - 0.001-0.008, sulphur - 0.001-0.008, phosphorus - 0.003-0.012, calcium 0.005-0.03, copper 0.05-0.30, iron - the rest. Steel is cast in blanks which are subjected to austenisation at temperature 1180-1210°C. Further, they are preliminary deformed with regulated reductions not less, than 12% at temperature 1000-1050°C, cooled in air to temperature of beginning of finish deformation and finally deformed at temperature 880-770°C. Also, each successive reduction at 1-4% exceeds the previous one. Temperature of end of rolling of flats is calculated by formula: Tre=Ar₃+(100-130)-37.7ln(t), where t - thickness of flat. Accelerated cooling is carried out in interval of temperatures 620-510°C, further, flat is slowly cooled in pile to temperature of environment.

EFFECT: high strength and improved weldability of steel.

1 ex, 2 tbl