The influence of thermomechanical parameters in ferrite grain refinement in a low carbon Nb-microalloyed steel

2005 ◽  
Vol 53 (1) ◽  
pp. 41-45 ◽  
Author(s):  
B. Eghbali ◽  
A. Abdollah-zadeh
Keyword(s):  
Grain Refinement ◽  
Microalloyed Steel ◽  
Low Carbon ◽  
Nb Microalloyed Steel

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.

Austenite Grain Size of Thin Slab and Its Influence on Direct Hot Strip Rolling of Nb Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 295-302 ◽  
Author(s):  
Hong Tao Zhang ◽  
Ganyun Pang ◽  
Rui Zhen Wang ◽  
Chengbin Liu
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Microalloyed Steel ◽  
Thin Slab ◽  
Hot Strip Rolling ◽  
Austenite Grain Size ◽  
Thick Slab ◽  
Rolling Pass ◽  
Austenite Grain ◽  
Nb Microalloyed Steel

In the production with thin slab casting a serious problem of insufficient grain refinement and microstructural inhomogeneity has been found. In this paper attention has been paid to the austenite grain size changes in thin slab of a high strength Nb microalloyed steel under as-cast conditions and after first rolling pass. For comparison, the conventional thick slab was also investigated. It was found that although as-cast thin slab shows a smaller average austenite grain size than that of as cast thick slab; the latter after reheating shows a much finer average austenite grain size. The first rolling pass at high temperature and with heavy reduction causes rapid recrystallization that contributes to austenite grain refinement.

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