RU2006131203A - PIPES OF MEDIUM-CARBON LOW-ALLOY STEEL - Google Patents

Claims (4)

1. A pipe billet of medium carbon low alloy steel having predetermined parameters of the structure, mechanical properties, characterized in that the billet is made of steel containing the following ratio of components, wt.%: carbon [C] 0.41-0.48 Manganese [Mn] 0.30-0.60 silicon [Si] 0.17-0.37 chrome [Cr] 0.05-0.30 sulfur [S] 0.005-0.045 nitrogen [N] 0.005-0.010 arsenic [As] 0.0001-0.03 tin [Sn] 0.0001-0.02 lead [Pb] 0.0001-0.01 zinc [Zn] 0.0001-0.005 calcium [Ca] 0.001-0.005 iron and inevitable impurities rest, when the ratio is fulfilled, the sum (arsenic + tin + lead + 5 · zinc) ≤0.07; 0.50≤ [carbon black + manganese / 6 + (chrome / 5)] ≤0.69, hot rolled, heat-treated, the tube billet has a ferrite-pearlite structure, the actual grain size is 5-10 points, the central porosity of the macrostructure, point heterogeneity , liquation square no more than 2.0 points average for each species, shrink liquation no more than 1 point, liquation strips no more than 1 point, for non-metallic inclusions - point sulfides, point oxides, stitch oxides, brittle silicates, plastic silicates, undeformed silicates more than 2.5 points n about each type of inclusions, mechanical properties after hardening and low tempering: temporary tensile strength not less than 639 N / mm, yield strength, not less than 373 N / mm ² , elongation not less than 16%, relative narrowing not less than 40%, impact strength KCU (+ 20 ° С) not less than 39 J / cm ² . 2. The pipe billet according to claim 1, characterized in that the steel further comprises, as impurities, wt.%: Phosphorus not more than 0.045, nickel not more than 0.30; copper no more than 0.25. 3. The pipe billet according to claim 1 or 2, characterized in that when the sulfur content is ≤0.025%, it has mechanical properties - temporary tensile strength of at least 639 N / mm ² , yield strength of at least 373 N / mm ² , relative elongation not less than 18%, relative narrowing not less than 45%, impact strength KCU (+ 20 ° С) not less than 49 J / cm ² . 4. The pipe billet according to claim 1 or 2, characterized in that at a content of 0.025% ≤ sulfur ≤0.045%, it has mechanical properties — temporary tensile strength of at least 650 N / mm ² , yield strength of at least 390 N / mm ² , relative elongation not less than 16%, relative narrowing not less than 40%, impact strength KCU (+ 20 ° С) not less than 39 J / cm ² .