Superior Properties of Ultra-fine-grained Steels

Abstract

A description of the improved mechanical properties obtained in ultra-fine-grained steels up to now will be presented in this paper, and some potential applications of these new generation steels will be described. In addition, the principle and implementation of a novel hot rolling process developed by the author will be introduced. This novel Thermomechanical Nonrecrystallisation Control Process (TNCP) has been shown to give an ultra-fine ferrite (uff) structure with grain sizes of 2 to 3mm in various test steels, thus resulting in super-toughness. Charpy V impact test results suggest that some of these steels could still be tough at temperatures lower than -100 °C. This novel process, TNCP, is one potential candidate for the commercial production of superior ultra-fine-grained steels in the future.

Multifunctional Bi-Layered Tribofilm Generated on Steel Contact Interfaces under High-Temperature Melt Lubrication

“…While the overlying film mainly involves lubricant chemistry, the induced nanograin layer with unique characteristics can dominate the microstructural properties of the rubbing surface. Ultrafine-grained materials have been prevalently known for their unusual mechanical features including high yield strength, excellent impact toughness and good fatigue strength. − Superior mechanical characteristics are predominantly associated with the substantial boundaries density within the microstructure beside grain size dependence. Herein, the surficial region of nanograined oxides (average diameter of 50–150 nm) can significantly enhance the mechanical strength of the rubbing interface and consequently increase its wear resistance. , As shown previously, the astonishing smoothness observed can be attributed to the improved wear resistance when asperities contacts are ultimately minimized under such surface quality.…”

Oxidative and Frictional Behavior of a Binary Sodium Borate–Silicate Composite in High-Temperature Lubricant Applications

“…The topmost layer on the ball is expected to act in a similar fashion by suppressing scale development. Furthermore, a layer comprising ultra-fine grained particles beneath the mixed reaction products layer was evidenced (Figure b), which possesses good mechanical properties including high yield strength, excellent impact toughness, and good fatigue strength. , The presence of such nanograined oxide layer (average diameter 50–100 nm) can significantly enhance the mechanical strength of the sliding interface and improve its wear resistance. , This layer is relatively superplastic and soft and can suppress the shearing at high loading conditions.…”

Weld Properties of Low Carbon Steel Using Shielded Metal Arc Welding

“…The observation of heat affected zone reveals the formation of coarse parlite grains with patchy free ferrite. The formation of patches has adverse effect on the structure due to uneven cooling rates during solidification [12]. Patches formed is the reason of uneven cooling rates during solidification [13].…”