The effect of cold forming on structure and properties of 32 CDV 13 steel by radial forging process

Abstract

The present study focuses on the effect of various degrees of plastic deformation generated by cold radial forging on the mechanical properties and the fracture morphology of 32 CDV 13 steel. The cold forging percentage was evaluated for 17.45, 33.30, 42.0 and 46.47 %. The microstructural analysis of the steel shows tempered martensite. The tensile strength, yield strength and hardness were found to increase with the increase of cold forging percentage due to the energy stored in the material during cold forging. For higher cold forging percentage, the toughness of the material was decreased according to the reduction of absorbed energy obtained during deformation. Fractography of the Charpy impact specimens shows a surface roughness and dimple pattern for the steel as was acquired and for 17.45 and 33.3 % of cold forging; while for 42 and 46.47 % of cold forging a cleavage fracture pattern was observed.

Weldability of cold-formed high strength and ultra-high strength steels

“…Additionally, it increases the dislocation density throughout the deformed microstructure. Excessive dislocations hinder grain boundaries movement and grains deformation while encouraging the mobility of atoms [26,27]. These phenomena cause some changes in material behaviour, including an increase in its strength and hardness, a decrease in its ductility, and a drop in its fracture toughness.…”

Analytical modeling of fatigue crack growth in plastically pre‐strained steels

“…9 As a consequence, the mechanical properties of the metal are affected, resulting in an increase in strength and a decrease in ductility. [10][11][12] Furthermore, the rate at which fatigue cracks propagate is influenced by various factors, including the applied fatigue loads (load range and history, stress ratio), geometry, microstructural aspects, environmental conditions, and other phenomena at the crack tip, such as the crack closure mechanism (e.g., plasticity-induced crack closure). 13,14 The microstructural changes in the material at the atomic (dislocation slip, twinning, and interaction) and microscale (grain elongation) levels, induced by plastic pre-deformation, influence the conditions near the crack tip and plastic zone size/shape and hence the Stage II fatigue crack propagation rate.…”

“…The dislocation network created by multiple slips and sequence of dislocation stacks at the grain boundaries prevents dislocation movement, increasing the flow stress and hardness through work hardening processes 9 . As a consequence, the mechanical properties of the metal are affected, resulting in an increase in strength and a decrease in ductility 10–12 . Furthermore, the rate at which fatigue cracks propagate is influenced by various factors, including the applied fatigue loads (load range and history, stress ratio), geometry, microstructural aspects, environmental conditions, and other phenomena at the crack tip, such as the crack closure mechanism (e.g., plasticity‐induced crack closure) 13,14 .…”