FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, specifically to thick-walled steel pipes, which can be used for drilling or oil and natural gas transportation. High-strength thick-walled steel pipe, welded by electric resistance welding, contains, wt%: C 0.025–0.084, Si 0.10–0.30, Mn 0.70–1.80, P 0.001–0.018, S 0.0001–0.0029, Al 0.01–0.10, Nb 0.001–0.065, V 0.001–0.065, Ti 0.001–0.033, Ca 0.0001–0.0035, N 0.0050 or less, O 0.0030 or less, if necessary, at least, one element, selected from: B 0.0030 or less, Cu 0.001–0.350, Ni 0.001–0.350, Mo 0.001–0.350 and Cr 0.001–0.700, Fe and incidental impurities are rest. Pcm parameter, characterizing microstructure after pipe welded seam fast cooling and defined by expression Pcm=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5·B, is equal to 0.20 or less. Microstructure includes 90% or more of quasi polygonal ferrite by area, having grain size of 10 mqm or less in steel pipe main part and in part, welded by electric resistance welding.
EFFECT: pipe is characterized by high values of low-temperature impact strength and resistance to hydrogen cracking, as well as high reliability of pipe welded part.
10 cl, 3 dwg, 5 tbl, 2 ex
