EFFECT OF FERRITE-BAINITE STRUCTURE ON THE PROPERTIES OF HIGH-STRENGTH PIPE STEEL

摘要

Mechanical properties of pipe steel 07G2MFB are studied after cooling from the austenitic region at rates of 0.9–32℃/sec making it possible to obtain a ferrite-bainite structure with different ratios of structural components. It is shown that formation of a predominantly bainitic structure formed with high cooling rates provides less crack resistance with static loading than a structure in which polygonal ferrite predominates. A bainitic structure is preferable with dynamic loading. Treatment leading to formation of coarse islands of martensite-austenite (MA) component within a ferrite-bainite structure has an unfavorable effect on crack tip opening displacement CTOD, ductile-brittle transition temperature T_(50), and resistance to hydrogen embrittlement Δψ/ψ.