METHOD OF PRODUCING A PIPE WITH LOW YIELD POINT TO ULTIMATE STRENGTH RATIO Russian patent published in 2019 - IPC C21D8/10 C22C38/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy and can be used, in particular, for production of high-strength casing pipe of critical purpose. To produce steel pipe with low yield point to ultimate strength ratio, high impact viscosity and ductility, steel billet is hot-rolled with separation into rough and finishing stages, coiling of rolled stock into roll, roll forming of tubular billet with subsequent welding of its edges with high-frequency currents. Finishing rolling is performed with initial temperature of 960–1,080 °C, accelerated cooling of rolled products is carried out with water at rate of 10 °C/s or more, wherein water cutoff for head and tail sections of rolled stock is 4 m or more, coiling of rolled metal is carried out at temperature 500–640 °C. Billet is made of steel containing, wt%: carbon 0.25÷0.37, manganese 0.80÷1.45, silicon 0.20÷0.35, chromium ≤0.30, nickel ≤0.30, copper ≤0.30, titanium ≤0.030, aluminum 0.015÷0.050, nitrogen ≤0.012, sulfur ≤0.010, phosphorus ≤0.020, calcium 0.001÷0.020, arsenic ≤0.010, lead ≤0.002, tin ≤0.020, antimony ≤0.005, zinc ≤0.020, iron and unavoidable impurities – balance, total content of chromium, nickel and copper corresponds to 0.25÷0.55 wt%, manganese to silicon ratio is within 4.0÷4.5.

EFFECT: disclosed is a method of producing a pipe with low yield point to ultimate strength ratio.

6 cl, 3 tbl