scholarly journals Effect of Ni addition on Bainite Microstructure of Low-Carbon Special Bar Quality Steels and its influence on CCT diagrams

2021 ◽  
Author(s):  
José Britti Bacalhau ◽  
Conrado Ramos Moreira Afonso
Keyword(s):  
Low Carbon ◽  
Ni Addition ◽  
Bainite Microstructure ◽  
Cct Diagrams

Effect of boron on the continuous cooling transformation kinetics in a low carbon advanced ultra-high strength steel (A-UHSS)

2012 ◽  
Vol 1485 ◽  
pp. 83-88 ◽  
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J. M. Cabrera
Keyword(s):  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Characterization ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Cct Diagrams

ABSTRACTThe aim of the present research work is to investigate the influence of B addition on the phase transformation kinetics under continuous cooling conditions. In order to perform this study, the behavior of two low carbon advanced ultra-high strength steels (A-UHSS) is analyzed during dilatometry tests over the cooling rate range of 0.1-200°C/s. The start and finish points of the austenite transformation are identified from the dilatation curves and then the continuous cooling transformation (CCT) diagrams are constructed. These diagrams are verified by microstructural characterization and Vickers micro-hardness. In general, results revealed that for slower cooling rates (0.1-0.5 °C/s) the present phases are mainly ferritic-pearlitic (F+P) structures. By contrast, a mixture of bainitic-martensitic structures predominates at higher cooling rates (50-200°C/s). On the other hand, CCT diagrams show that B addition delays the decomposition kinetics of austenite to ferrite, thereby promoting the formation of bainitic-martensitic structures. In the case of B microalloyed steel, the CCT curve is displaced to the right, increasing the hardenability. These results are associated with the ability of B atoms to segregate towards austenitic grain boundaries, which reduce the preferential sites for nucleation and development of F+P structures.

Effects of Boron Addition on Undercooled Austenite Transformation of Low Carbon Mn-Nb Steels

2012 ◽  
Vol 476-478 ◽  
pp. 316-320
Author(s):  
Yan Mei Li ◽  
Zheng Tao Duan ◽  
Fu Xian Zhu
Keyword(s):  
Transformation Temperature ◽  
Boron Addition ◽  
Low Carbon ◽  
Continuous Cooling Transformation ◽  
Austenite Transformation ◽  
Continuous Cooling ◽  
Bainite Microstructure ◽  
Undercooled Austenite

The effects of boron on the undercooled austenite transformation of low carbon Mn-Nb steels during continuous cooling were investigated in this study. Five kinds of steel specimens were fabricated by varying boron contents. Continuous cooling transformation (CCT) curves of the investigated steels under deformed conditions were constructed by a combination of deformation dilatometry and metallographic methods. The results indicated that a small amount of boron efficiently increased the hardenability of steels and lowered transformation temperature, which leading to a finer bainite microstructure and an increase in hardness.

Austenite transformation products in quenched low-carbon HSLA steel

1990 ◽  
Vol 48 (4) ◽  
pp. 902-903
Author(s):  
R. Varughese ◽  
P. R. Howell
Keyword(s):  
Hsla Steel ◽  
Transformation Products ◽  
Age Hardening ◽  
Plate Steel ◽  
Low Carbon ◽  
Weight Percentage ◽  
Copper Precipitation ◽  
Hsla Steels ◽  
Martensitic Microstructure ◽  
Cct Diagrams

The alloy design for the HSLA-100 plate steel aims at optimizing the strength and toughness through developing a refined ferritic microstructure while enhancing the weldability by lowering the carbon levels to 0.04 wt% or less. The austenite grain refining potential of microalloying additions of niobium is coupled with the hardenability effects of Mn, Ni, Cr and Mo to achieve a fine acicular microstructure through water quenching prior to age-hardening through copper precipitation. Wilson et. al, in developing CCT diagrams for these HSLA steels noted that the as-quenched microstructure in the 0.04 wt% carbon steel consisted of a mixture of martensite and bainite and their results indicated that a fully martensitic microstructure at slightly higher carbon levels contributed to enhanced toughness. In this paper, we present our results on the microstructural features found in an oil-quenched sample of the HSLA-100 steel.The chemical composition (in weight percentage) of the 1 1/4" thick plate steel is given below.

Steels with Ferrite-Bainite Microstructure with Improved Weldability and Cold Resistance for Main Pipelines

2007 ◽  
Vol 539-543 ◽  
pp. 4744-4749
Author(s):  
S.Y. Nastich ◽  
Y.D. Morozov ◽  
L.I. Efron ◽  
M.Y. Matrosov
Keyword(s):  
Phase Transformations ◽  
Cold Resistance ◽  
Pipe Steels ◽  
Fine Grained ◽  
Main Pipelines ◽  
Bainite Microstructure ◽  
Cct Diagrams

The required complex of properties of modern pipe steels, including improved weldability and cold resistance, can be achieved due to formation of fine-grained ferrite-bainite microstructure of steel. Effect of various designs of additional alloying of steel on phase transformations with use of deformation CCT diagrams is investigated. Key parameters of TMCPtechnology, necessary for obtaining the best complex of properties of plate and strip products are determined. Results of industrial trials in production of steel with ferrite-bainite microstructure of Russian steel manufacturers are presented.

scholarly journals Experimental Determination of Continuous Cooling Transformation (CCT) Diagrams for Dual-Phase Steels from the Intercritical Temperature Range

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 674 ◽  
Author(s):  
Krishna Bräutigam–Matus ◽  
Gerardo Altamirano ◽  
Armando Salinas ◽  
Alfredo Flores ◽  
Frank Goodwin
Keyword(s):  
Low Carbon Steel ◽  
Dual Phase ◽  
Low Carbon ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Hardness Tests ◽  
Wide Range ◽  
Two Phases ◽  
C Partitioning ◽  
Cct Diagrams

The phase transformation kinetics under continuous cooling conditions for intercritical austenite in a cold rolled low carbon steel were investigated over a wide range of cooling rates (0.1–200 ∘ C/s). The start and finish temperatures of the intercritical austenite transformation were determined by quenching dilatometry and a continuous cooling transformation (CCT) diagram was constructed. The resulting experimental CCT diagram was compared with that calculated via JMatPro software, and verified using electron microscopy and hardness tests. In general, the results reveal that the experimental CCT diagram can be helpful in the design of thermal cycles for the production of different grades of dual-phase–advanced high-strengh steels (DP-AHSS) in continuous processing lines. The results suggest that C enrichment of intercritical austenite as a result of heating in the two phases (ferrite–austenite) region and C partitioning during the formation of pro-eutectoid ferrite on cooling significantly alters the character of subsequent austenite phase transformations.

scholarly journals Effect of Mo, Nb and V on Hot Deformation Behaviour, Microstructure and Hardness of Microalloyed Steels

2018 ◽  
Vol 941 ◽  
pp. 3-8
Author(s):  
Navjeet Singh ◽  
Andrii G. Kostryzhev ◽  
Chris R. Killmore ◽  
Elena V. Pereloma
Keyword(s):  
Thermomechanical Processing ◽  
Deformation Behaviour ◽  
Solute Drag ◽  
Granular Bainite ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Iron Carbides ◽  
Bainite Microstructure ◽  
Carbon Microalloyed

Three novel low carbon microalloyed steels with various additions of Mo, Nb and V were investigated after thermomechanical processing simulations designed to obtain ferrite-bainite microstructure. With the increase in microalloying element additions from the High V- to NbV- to MoNbV-microalloyed steel, the high temperature flow stresses increased. The MoNbV and NbV steels have shown a slightly higher non-recrystallization temperature (1000 °C) than the High V steel (975 °C) due to the solute drag from Nb and Mo atoms and austenite precipitation of Nb-rich particles. The ambient temperature microstructures of all steels consisted predominantly of polygonal ferrite with a small amount of granular bainite. Precipitation of Nb-and Mo-containing carbonitrides (>20 nm size) was observed in the MoNbV and NbV steels, whereas only coarser (~40 nm) iron carbides were present in the High V steel. Finer grain size and larger granular bainite fraction resulted in a higher hardness of MoNbV steel (293 HV) compared to the NbV (265 HV) and High V (285 HV) steels.

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