Influences of Thermomechanical Treatment and Nb Micro-alloying on the Hardenability of Ultra-High Strength Steels
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In: Metallurgical and materials transactions. A, Physical metallurgy and materials science , Vol. 50.2019, No. 7, 29.04.2019, p. 3238 - 3245.
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TY - JOUR
T1 - Influences of Thermomechanical Treatment and Nb Micro-alloying on the Hardenability of Ultra-High Strength Steels
AU - Esterl, Raphael
AU - Sonnleitner, Markus
AU - Schnitzer, Ronald
PY - 2019/4/29
Y1 - 2019/4/29
N2 - For the construction of mobile crane booms, ultra-high strength steels produced via thermomechanical processing (TMP) have widely substituted steels fabricated through the conventional quenching and tempering (Q+T) route. A strong deformation of the austenite grain during hot rolling followed by direct quenching (DQ) offers benefits in terms of strength and toughness. To guarantee an optimal through-hardening, alloying elements retarding the γ to α transformation are used. To explore the influence of the processing route on the critical cooling rate and the hardenability, hot deformation tests were performed on a deformation dilatometer. Different cooling rates were applied after deformation corresponding to two different rolling cycles with varying finish rolling temperatures (FRTs). The obtained hardness values were compared to those received through conventional quenching after austenitization. These investigations conducted on three steels with varying micro-alloying contents showed that Nb in combination with TMP raises strength significantly, and promotes a bainitic and ferritic transformation in solid solution. When applying low FRTs and in combination with other micro-alloying elements, NbC coarsens and reduces the effect of precipitation hardening.
AB - For the construction of mobile crane booms, ultra-high strength steels produced via thermomechanical processing (TMP) have widely substituted steels fabricated through the conventional quenching and tempering (Q+T) route. A strong deformation of the austenite grain during hot rolling followed by direct quenching (DQ) offers benefits in terms of strength and toughness. To guarantee an optimal through-hardening, alloying elements retarding the γ to α transformation are used. To explore the influence of the processing route on the critical cooling rate and the hardenability, hot deformation tests were performed on a deformation dilatometer. Different cooling rates were applied after deformation corresponding to two different rolling cycles with varying finish rolling temperatures (FRTs). The obtained hardness values were compared to those received through conventional quenching after austenitization. These investigations conducted on three steels with varying micro-alloying contents showed that Nb in combination with TMP raises strength significantly, and promotes a bainitic and ferritic transformation in solid solution. When applying low FRTs and in combination with other micro-alloying elements, NbC coarsens and reduces the effect of precipitation hardening.
UR - http://www.scopus.com/inward/record.url?scp=85065206421&partnerID=8YFLogxK
U2 - 10.1007/s11661-019-05235-8
DO - 10.1007/s11661-019-05235-8
M3 - Article
VL - 50.2019
SP - 3238
EP - 3245
JO - Metallurgical and materials transactions. A, Physical metallurgy and materials science
JF - Metallurgical and materials transactions. A, Physical metallurgy and materials science
SN - 1073-5623
IS - 7
ER -
