Razdobreev Valery Guriyovych, PhD (Engin.), Senior Researcher, Institute named after Z.I. Nekrasov of the NAS of Ukraine, Academican Starodubova square, 1, Dnipro, Ukraine, 49107; e-mail: v_razdobreev@mail.ru

Research of the influence of boron microallegation on the corrosion
behavior of a low-carbon structural steel in various structural condition

Summary. The aim of the work is to study the effect of boron, structural
features of the rolled steel of low-carbon steel in hot rolled and thermally
hardened states on its corrosion resistance. Investigation of the corrosion
resistance of hot-rolled and thermally hardened (quenching and tempering at
temperatures of 200-600 jC) low-carbon steel St3sp containing 0.007% B and
having no boron additives was carried out on polished samples with constant
immersion in room temperature acidic medium, causing corrosion with
hydrogen depolarization (1 N solution of H2SO4), and with variable immersion
in aggressive media, causing corrosion with oxygen depolarization (in a 3 %
NaCl solution). It was found that the atmospheric corrosion rate of hot-rolled
low-carbon steel with and without boron is almost the same. It was
experimentally established that samples of boron-containing steel (0.007 % B),
when tested in a 1 N solution of H2SO4 and when immersed in a 3 % NaCl
solution in a thermally hardened state, have a lower corrosion resistance than
steel without boron: the maximum corrosion losses were samples hardened and
tempered at a temperature of 300 оC. As shown by studies of microstructures
using an electron microscope, when tempering 300 оC, hardened boroncontaining steel is released, many relatively small inclusions of boron are
released that contribute to the so-called structural corrosion. These finely
divided inclusions, most of which are identified as Fe2B, are released from the
supersaturated solid solution upon cooling and sharply reduce the resistance of
steel to atmospheric corrosion. Thus, improving the hardenability of lowcarbon steel, boron significantly reduces its corrosion resistance in aggressive
environments after quenching and tempering.
Keywords: low-carbon steel, low-carbon steel with boron, atmospheric
corrosion, corrosion losses, microstructure, boron inclusions, hardening,
tempering
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«Фундаментальные и прикладные проблемы черной металлургии. – 2019. – Вып.33
«Fundamental and applied problems of ferrous metallurgy». – 2019. – Collection 33
ISSN 2522-9117 «Fundamental’nye i prikladnye problemy černoj metallurgii». – 2019. – Vypusk 33
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