The Paton Welding Journal, 2016, №02



2016 №02 (03)

DOI of Article 10.15407/tpwj2016.02.04

2016 №02 (05)

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The Paton Welding Journal, 2016, #2, 22-27 pages

Evaluation of susceptibility to temper brittleness of heat-resistant steels using high-temperature testing

V.Yu. Skulsky¹, V.V. Zhukov¹, M.A. Nimko¹, S.I. Moravetsky¹ and L.D. Mishchenko²

¹E.O. Paton Electric Welding Institute, NASU 11 Kazimir Malevich Str., 03680, Kiev, Ukraine. E-mail: office@paton.kiev.ua
²Company «Turboatom» 199 Moskovsky Ave., 61037, Kharkov, Ukraine. E-mail: office@turboatom.com.ua
 
 
Abstract
Main point of problem of crack formation in tempering is defined. It is shown that low metal ductility during plastic deformation, promoted by stress relaxation is a condition for nucleation of such cracks. Important brittleness factor under these conditions is temporarily developing secondary hardening, related with nucleation and precipitation of secondary phases in matrix. Since alloys with different level of alloying demonstrate different behavior during tempering, then evaluation of their possible tendency to temper brittleness is of interest in each specific case. A procedure is described for high-temperature tensile testing, which allows evaluating ductile properties of metal under different tempering conditions. Susceptibility to temper brittleness was evaluated using a criterion of value of relative reduction in area φ ≤ 25 %. Studied was a nature of ductility change in complexly-alloyed heat-resistant steels under different tempering modes resulting in secondary hardening condition and after hardening stage. It is shown that steels in a period of steel hardening development have low ductility with typical for such a state intergranular fracture. Determined are critical tempering modes, under which a high ductility state is achieved, based on which absence of susceptibility to tempering cracks can be predetermined. 9 Ref., 1 Table, 8 Figures.
 
Keywords: hardening steels, tempering, cracks, secondary hardening, tempering ductility, high ductility condition
 
 
Received:                05.11.15
Published:               12.04.16
 
 
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