Niobium in Engineering Steels for Automotive Applications

Abstract

In the last decade, the European niobium consumption in automotive strip and sheet has more than tripled. The development of high strength and advanced high strength steel grades for strip and plate products focused upon constantly increasing strength levels combined with excellent fatigue properties as well as formability and weldability. Until now, the high potential of microalloyed steel has not been used to the same extent in forgings and springs. This paper reviews automotive components as transmissions, suspensions and springs highlighting new material solutions for special steels having optimized processing and in-use properties. Special consideration is given to the metallurgical background as well as to examples for the processing and application of niobium microalloyed steel in forgings and springs from low carbon and higher carbon containing steels. Niobium metallurgy permits the reduction of carbon to meet more stringent end-user requirements demanding high strength combined with improved toughness, fatigue strength and weldability at a competitive manufacturing cost.

The Effect of Niobium Addition and Pre-Annealing on the Tensile Properties of 52CrMoV4 Spring Steel

“…This is the way in which the dislocation locking mechanism works in conjunction with the development of tiny phases to produce materials with improved strength characteristics [6,21]. Similar to previous research, it was discovered that the production of Nb and C particles following heat treatment results in a higher Nb ratio material with a finer grain size [5,[7][8][9][10][11]. The mechanical properties of the steel are greatly affected by the size of the prior austenite grain [22].…”

“…It is understood that when the Nb ratio increases, pre-annealing is effective in reducing the grain size. When the relevant literature was examined, it was seen that the grain size decreased with the effect of Nb [5][6][7][8][9][10][11].…”

“…The grain refinement effect of niobium is mainly due to the delay or prevention of recrystallization in the final hot-forming steps. It is mentioned in the study that in order to make the most of its metallurgical potential, annealing should be performed before hot working to dissolve the Nb(C,N) [7].…”

Effect of Nb on Microstructural Evolution and Mechanical Properties of Hot‐Rolled Quenching and Partitioning Steels Containing Bainite

“…To further improve the strength, ductility, work hardening, and other mechanical properties of Q&P steels, a conventional microalloying element such as Nb can be added. [19] Nb has the ability to improve the strength of construction steels without affecting its elongation because it controls the recrystallization process such that finer prior austenite grain size is obtained. [20,21] In addition, the formation of niobium carbo-nitride Nb (C, N) particles at lower process temperatures will lead to precipitation strengthening.…”

Synchrotron Investigation on the Precipitation Behaviour of Niobium Microalloyed Steel

“…in a CSP ® line, need special attention to adjust the corresponding process parameters [2,3]. Other examples for typical applications of niobium metallurgy find in engineering grades as forging and spring steels [4]. Precipitation and dissolution behavior of niobium carbo-nitrides thus is of particular interest for many technical applications.…”