The Heat Treatment of Vanadium-Modified Alloy Steels

Abstract

SUMMARY INTRODUCTIONAt a recent symposium, Robinson l summarized the development of and the challenges faced by alloy steels in the automotive industry. Through the years since Henry Ford revolutionized car manufacture, constant changes in alloy steel compositions, to meet the demands of the times, were prevalent. At present, it appears that the technology of heat-treated alloy steels has reached its maturity, with work concentrated on both accurately predicting hardenability from chemical composition and balancing composition to minimize cost for the application desired . However, this is far from the reality, for specific effects of the various alloying elements, individually and in combination, on hardenability, materials properties, and service performance are far from being understood. l , 2 The current use of alloy steels depends to some extent on the mystique, developed with their development, that either individual or combinations of alloying elements were considered uniquely responsible for the steel properties.Despite this mystique, there persist changes in the selection of materials based on alloy costs and performance, i.e., response to varied and complex engineering and processing demands on the materials. The complexity of demands resulted in the establishment of an increased number of alloy grades to meet specific demands. In 1940, the SAE (Society of Automotive Engineers) listed 65 standard grades of lowalloy steels; today7 there are 86, not including the "H band" series, plus EX grades and numerous "modified" grades specified by individual manufacturers. In the course of the years, 96 former grades 7 were deleted, i.e, no longer of major commercial use. Such continuing activity suggests that the technology of alloy steels is still in a state of flux.Although wrought alloy steels face some competition in low-stress automotive components, they will continue to be the dominant materials for highly stressed components, such as power transmission gears and shafting, ball and roller bearings, and spring members. These components have high hardness (~50Rc ) and depend on the ability of the steel to be through hardened, case hardened by induction heating, or case carburized.In predicting hardenability from composition, one finds no readily available factor for vanadium,3 in spite of the fact that vanadium was used in the early alloy steel grades

Correlative analysis of interaction between recrystallization and precipitation during sub-critical annealing of cold-rolled low-carbon V and Ti–V bearing microalloyed steels

“…For the annealing condition of 800 o C 0 s, velocity of grain boundary is estimated using first order approximation [63] as explained below. Apart from Mn solute drag effect on recrystallization, there could be other direct (for example, Mn-C dipole formation [77]) or indirect factors (for example, precipitation [66,[78][79][80][81][82][83] or texture [84]) of Mn solute atoms on recovery/recrystallization mechanism. Ushioda et al [77] have studied the role of Mn in delaying the recovery during annealing, where dissolved C from cementite combines with Mn to form Mn-C complex.…”

“…It is proposed that higher amount of Mn solutes increases the solubility of TiC precipitate in austenite phase [82,83] and delays precipitation kinetics. The effect of Mn solute content on precipitation kinetics in the austenite phase is well known [66,[78][79][80][81][82][83], however there are not any conclusive data published on the Mn solute content effect on the precipitate solubility in the ferrite phase. The equilibrium precipitate volume fraction is plotted for the three grades for equilibrium state as shown in Fig.…”

Superhardenability behavior of vanadium in 40CrNiMoV steel

“…Previous studies reported contrasting results regarding the effect of vanadium on steel hardenability. Grossman, Lamont and Mangonon [6][7][8][9][10] found that vanadium can effectively improve the hardenability of steels; their results showed that the hardenability multiplying factors of steels containing 0.1% vanadium can reach 1.2-1. 6.…”