Mechanism of ferrite grain refinement during warm deformation of a low carbon Nb-microalloyed steel

2007 ◽  
Vol 457 (1-2) ◽  
pp. 219-225 ◽  
Author(s):  
A. Abdollah-Zadeh ◽  
B. Eghbali
Keyword(s):  
Grain Refinement ◽  
Microalloyed Steel ◽  
Low Carbon ◽  
Warm Deformation ◽  
Nb Microalloyed Steel

Effect of Warm Deformation on Ferrite Microstructure Evolution in a Ti-Microalloyed Steel

2007 ◽  
Vol 558-559 ◽  
pp. 497-504
Author(s):  
Beitallah Eghbali
Keyword(s):  
Microstructure Evolution ◽  
Microalloyed Steel ◽  
Early Stage ◽  
Microstructural Analysis ◽  
Optical Microscope ◽  
Low Carbon ◽  
High Angle ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic

Warm deformation is one of the promising hot rolling strategies for producing thin hot rolled steel strips. A better understanding of the microstructure evolution during warm deformation is important for a successful introduction of such processing into the industrial production. In the present research, the effect of deformation strain on the ferrite microstructure development in a low carbon Ti-microalloyed steel was investigated through warm torsion testing. Microstructural analysis with optical microscope and electron back-scattering diffraction was carried out on the warm deformed ferrite microstructures. The results show that at the early stage of deformation an unstable subboundaries network forms and low angle boundaries are introduced in the original grains. Then, with further straining, low angle boundaries transform into high angle boundaries and stable fine equiaxed ferrite grains form. It was considered that dynamic softening and dynamically formation of new fine ferrite grains, with high angle boundaries, were caused by continuous dynamic recrystallization of ferrite.

scholarly journals Determination of Non-Recrystallization Temperature for Niobium Microalloyed Steel

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2639
Author(s):  
Mohammad Nishat Akhtar ◽  
Muneer Khan ◽  
Sher Afghan Khan ◽  
Asif Afzal ◽  
Ram Subbiah ◽  
...  
Keyword(s):  
Microalloyed Steel ◽  
Casting Process ◽  
Rolling Process ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Nb Microalloyed Steel ◽  
Niobium Microalloyed Steel ◽  
Multiple Hit ◽  
Deformation Tests

In the present investigation, the non-recrystallization temperature (TNR) of niobium-microalloyed steel is determined to plan rolling schedules for obtaining the desired properties of steel. The value of TNR is based on both alloying elements and deformation parameters. In the literature, TNR equations have been developed and utilized. However, each equation has certain limitations which constrain its applicability. This study was completed using laboratory-grade low-carbon Nb-microalloyed steels designed to meet the API X-70 specification. Nb- microalloyed steel is processed by the melting and casting process, and the composition is found by optical emission spectroscopy (OES). Multiple-hit deformation tests were carried out on a Gleeble® 3500 system in the standard pocket-jaw configuration to determine TNR. Cuboidal specimens (10 (L) × 20 (W) × 20 (T) mm3) were taken for compression test (multiple-hit deformation tests) in gleeble. Microstructure evolutions were carried out by using OM (optical microscopy) and SEM (scanning electron microscopy). The value of TNR determined for 0.1 wt.% niobium bearing microalloyed steel is ~ 951 °C. Nb- microalloyed steel rolled at TNR produce partially recrystallized grain with ferrite nucleation. Hence, to verify the TNR value, a rolling process is applied with the finishing rolling temperature near TNR (~951 °C). The microstructure is also revealed in the pancake shape, which confirms TNR.

Dynamic Recrystallization of Ferrite in a Low Carbon Nb-Microalloyed Steel

2005 ◽  
Vol 475-479 ◽  
pp. 149-152 ◽  
Author(s):  
Long Fei Li ◽  
Wang Yue Yang ◽  
Zu Qing Sun
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Microalloyed Steel ◽  
Phase Region ◽  
Ferrite Phase ◽  
Recrystallization Process ◽  
Low Carbon ◽  
Promoting Effect ◽  
Nb Microalloyed Steel ◽  
Average Size

The hot deformation behavior of a low carbon Nb-microalloyed steel is investigated by hot compression test in the ferrite phase region compared with a low carbon steel with similar compositions, and the effect of Nb on dynamic recrystallization of ferrite is analyzed. Results indicate that during hot deformation in the ferrite phase region, the effect of Nb solely depends on the size of NbC precipitates. Tiny particles which average size is about 7.5nm have a retarding effect on dynamic recrystallization process of ferrite, on the contrary, coarser particles which average size is about 30.6nm have a promoting effect and are of benefit to the refinement of recrystallized grains.

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