FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, namely to steel pipe produced by submerged-arc submerged arc welding from inner and outer surfaces. Main metal of the pipe has a chemical composition containing the following, wt%: 0.01–0.1 C; less than 0.5 Si; 0.5–2.0 Mn; 0.015 or less P; 0.01 or less S; less than 0.01 Al; 0.005–0.03 Ti; 0.002–0.006 N; 0.005 or less O; 0–0.01 Mg; 0–0.005 Ca; 0–0.6 Ni; 0–0.5 Cr; 0–0.5 Cu; 0–0.4 Mo; 0–0.06 Nb; 0–0.002 B; 0–0.06 V; the rest is Fe and impurities, and its ultimate strength is 480–620 MPa. Weld metal has a chemical composition containing the following in wt%: 0.03–0.1 C; 0.03–0.5 Si; 0.5–2.0 Mn; 0.015 or less P; 0.01 or less S; 0.001–0.03 Al; 0.005–0.04 Ti; 0.002–0.006 N; 0–0.035 B; 0.015–0.055 O; 0–0.6 Ni; 0–0.5 Cr; 0–0.5 Cu; 0–0.4 Mo; 0–0.06 V; 0–0.005 Ca; 0–0.01 Mg; 0–0.06 Nb; balance is Fe and impurities. Contents of chemical elements in weld metal satisfy conditions: Pcm=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B is 0.2 % or less, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 is 0.35–0.45 %, parameter α', which characterizes conditions of formation of needle ferrite and equal to (1.5×(O-0.89Al)+3.4×N-Ti) ×1000, ranges from -20 to 40, and Al/O makes 0.3–0.8. Pipe has ultimate strength class X60–X70 and high impact viscosity at low temperature in the area of weld metal.
EFFECT: disclosed is a steel pipe obtained by arc welding.
7 cl, 2 dwg, 7 tbl
