METHOD OF HEAT TREATMENT OF ROLLED PRODUCTS MADE OF LOW-CARBON, LOW-ALLOYED STEEL Russian patent published in 2000 - IPC

FIELD: metallurgy. SUBSTANCE: method may be used in production (heat treatment) of plates including billets (skelp) for electrically welded oil and gas pipes of large diameter, and also pipes from low-alloyed steels to meet stringent requirements on their strength, ductility, cold resistance, resistance to corrosion cracking in hydrogen-charged media. The method includes normalization from rolling heating at regulated temperature of rolling end (Ar₃ - 100) - (Ar₃ - 150) C; hardening (1) with heating in austenite region of temperatures above Ac₃ with holding and subsequent cooling with water; hardening (2) with heating in ferrite-austenite region of temperatures within range of (Ac₁ - 80) - (Ac₃ - 30) C with holding and subsequent cooling with water; high-temperature tempering at temperature of (500 - Ac₁) C with holding and subsequent cooling in air. The method results in production in the course of heat treatment of rolled products from low-alloyed steel with extra-fine grain structure and low dislocation density to ensure complex of high properties of strength, ductility, impact strength and per cent of ductility component in fracture of DWTT specimens at subzero temperatures and also resistance to corrosion cracking in hydrogen-charged media. EFFECT: higher efficiency. 2 cl, 1 tbl