Property Optimization in As-Quenched Martensitic Steel by Molybdenum and Niobium Alloying

Abstract

Niobium microalloying is the backbone of modern low-carbon high strength low alloy (HSLA) steel metallurgy, providing a favorable combination of strength and toughness by pronounced microstructural refinement. Molybdenum alloying is established in medium-carbon quenching and tempering of steel by delivering high hardenability and good tempering resistance. Recent developments of ultra-high strength steel grades, such as fully martensitic steel, can be optimized by using beneficial metallurgical effects of niobium and molybdenum. The paper details the metallurgical principles of both elements in such steel and the achievable improvement of properties. Particularly, the underlying mechanisms of improving toughness and reducing the sensitivity towards hydrogen embrittlement by a suitable combination of molybdenum and niobium alloying will be discussed.

Advances in Microalloyed Steels

“…The present Special Issue on Advances in Microalloyed Steels includes two review papers [1,2] and nine research papers [3][4][5][6][7][8][9][10][11]. In all of them, different combinations of microalloying elements are analyzed in terms of process, microstructure, and mechanical property modification.…”

“…The alternatives in microalloying are clearly reflected in terms of the grades studied in the different papers. Nb is present in many of them [1,2,5,7,8,10,11], alone or in combination with Mo [2,5,10], Ti [8], and V [10]. Two papers deal with Ti-Mo combinations [6,9], and the last two articles analyze the addition of V [4] and Al [3] as microalloying elements.…”

“…Even if some papers cover specific performance problems and optimization alternatives for industrial processing conditions [1,2,7,11], most of the papers deal with more fundamental analyses of the relationship between microstructure and mechanical properties [4][5][6]8,10]. Some papers also analyze the effect of microalloying on hot and cold working behaviors [3,9].…”

The Impact of Isothermal Treatment on the Microstructural Evolution and the Precipitation Behavior in High Strength Linepipe Steel

“…Reasonable addition of alloying elements provides excellent heat affected zone (HAZ) toughness and guarantees sufficiently low ductile-to-brittle transition temperature [16]. Nb microalloying is the backbone of HSLA steel metallurgy, providing a favorable combination of strength and toughness by pronounced microstructural refinement [17]. Nb microalloying raises the no-recrystallization temperature, leading to a more pancaked austenite and higher Sv (grain boundary surface area per unit volume) values.…”

The Impact of Strain Heterogeneity and Transformation of Metastable Austenite on Springback Behavior in Quenching and Partitioning Steel

“…Compared to conventional steel, the higher strength of UHSSs ensures there is greater potential for weight reduction [1][2][3]. Particularly, in order to accomplish a better balance of strength and ductility, Speer et al [4] proposed the quenching and partitioning (QP) process to obtain stabilized austenite in a martensitic microstructure.…”