Influence of Boron on the Precipitation Kinetics in Advanced Ultra-High Strength Steels

2015 ◽  
Vol 1765 ◽  
pp. 91-96
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J.M. Cabrera
Keyword(s):  
Stress Relaxation ◽  
High Strength Steels ◽  
High Strength ◽  
Relaxation Method ◽  
Low Carbon ◽  
Precipitation Kinetics ◽  
Austenite Recrystallization ◽  
Ultra High Strength Steels ◽  
Relaxation Curves ◽  
Kinetics Of

ABSTRACTIn the present work, the stress relaxation method was employed to determine the influence of B addition on the kinetics of strain-induced precipitation and its interaction with the static austenite recrystallization. For this purpose, the behavior of two low carbon advanced ultra-high strength steels was analyzed during stress relaxation tests at different temperatures and constant pre-strain rate. The precipitation start (Ps) and finish (Pf) times were determined from the relaxation curves and then the corresponding precipitation-time-temperature diagrams were constructed for each steel. Transmission Electron Microscopy was used to determine the chemical nature and evolution of precipitation. In general, the results show that the addition of B retards the austenite recrystallization, tends to accelerate the precipitation kinetics of carbonitrides and leads to a finer and denser distribution of precipitates. These results are discussed in terms of the driving force for the nucleation of precipitation, which in turn is controlled by the degree of supersaturation of microalloying element and as a function of B segregation and B-vacancy complexes to dislocations and grain boundaries.

Studies on Softening Kinetics of Niobium Microalloyed Steel Using Stress Relaxation Technique

2012 ◽  
Vol 715-716 ◽  
pp. 794-799 ◽  
Author(s):  
Cheng Liang Miao ◽  
Cheng Jia Shang ◽  
Guo Dong Zhang ◽  
Guo Hui Zhu ◽  
Hatem S. Zurob ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Microalloyed Steels ◽  
Distinct Advantage ◽  
Low Carbon ◽  
Shape Processing ◽  
Physically Based ◽  
Near Net Shape ◽  
Niobium Microalloyed Steel ◽  
Relaxation Curves ◽  
Kinetics Of

Stress relaxation was studied in a series of low carbon, high Mn microalloyed steels containing 0.012, 0.06 and 0.1 wt% Nb. The stress-relaxation curves were modeled using a physically-based model that takes into account the time evolution of precipitation, recovery and recrystallization as well as their interactions. The results confirm that high Mn-high Nb design can offer distinct advantage over the low-Mn design for the application of near net shape processing.

Development of Low Carbon Microalloyed Ultra High Strength Steels

2005 ◽  
Vol 500-501 ◽  
pp. 551-558 ◽  
Author(s):  
A. Ghosh ◽  
Brajendra Mishra ◽  
Subrata Chatterjee
Keyword(s):  
Room Temperature ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Hsla Steels ◽  
Finish Rolling ◽  
Ultra High Strength Steels ◽  
Rolling Temperatures ◽  
Carbon Microalloyed ◽  
Carbon Concentrations

In the present study HSLA steels of varying carbon concentrations, alloyed with Mn, Ni, Cr, Mo, Cu and micro-alloyed with Nb and Ti were subjected to different finish rolling temperatures from 850oC to 750oC in steps of 50oC. The microstructure of the steel predominantly shows martensite. Fine twins, strain induced precipitates in the martensite lath along with e-Cu precipitates are observed in the microstructure. With an increase in carbon content the strength value increases from 1200MPa UTS to 1700MPa UTS with a negligible reduction in elongation. Impact toughness values of 20-26 joules at room temperature and −40oC were obtained in sub-size samples.

Effect of Coiling Temperature on Kinetics of Austenite Formation in Cold Rolled Advanced High Strength Steels

2012 ◽  
Vol 706-709 ◽  
pp. 2112-2117 ◽  
Author(s):  
R.R. Mohanty ◽  
O.A. Girina
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Continuous Heating ◽  
Austenite Formation ◽  
Continuous Annealing ◽  
Hard Material ◽  
Low Carbon ◽  
Coiling Temperature ◽  
Hot Rolled ◽  
Kinetics Of

A systematic experimental investigation was conducted using lab processed low carbon 0.08C-2.0Mn-Cr-Mo steel microalloyed with Ti/Nb to evaluate the influence of initial hot-rolled microstructures on the kinetics of austenite formation and decomposition after cold-rolling and subsequent annealing. Coiling temperature as a major hot rolling parameter was used to obtain different types of hot-rolled microstructures. Dilatometer and continuous annealing simulator were employed for austenite formation studies and annealing simulations, respectively. It was found that the coiling temperature affects the processes occurring during heat treatment in continuous annealing lines of full hard material: ferrite recrystallization, austenite formation during continuous heating and austenite decomposition during cooling. A decrease in coiling temperature accelerates the recrystallization of ferrite and nucleation of austenite, which results in formation of refined ferrite-martensite structure. The effect of initial hot rolled structure on final mechanical properties after continuous annealing was also investigated.

Mechanical properties and microstructure of low carbon ultra-high strength steels (UHSS) microalloyed with boron

2012 ◽  
Vol 1373 ◽  
Author(s):  
I. Mejía ◽  
A. García de la Rosa ◽  
A. Bedolla-Jacuinde ◽  
J.M. Cabrera
Keyword(s):  
Mechanical Properties ◽  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Low Carbon ◽  
Advanced High Strength Steels ◽  
New Family ◽  
Ultra High Strength Steels ◽  
Hot Rolled

ABSTRACTThe aim of this research work is to study the effect of boron addition on mechanical properties and microstructure of a new family of low carbon NiCrVCu advanced high strength steels (AHSS). Experimental steels are thermo-mechanically processed (TMP) (hot-rolled+quenched). Results show that the microstructure of these steels contains bainite and martensite, predominantly, which nucleate along prior austenite grain boundaries (GB). On the other hand, tensile tests reveal that the TMP steels have YS (0.2% offset) of 978 MPa, UTS of 1140 MPa and EL of 18%. On the basis of exhibited microstructure and mechanical properties, these experimental steels are classified as bainitic-martensitic complex phase (CP) advanced ultra-high strength steels (UHSS).

A Review of the Stress-Relaxation Method for Following the Kinetics of Precipitation, Recovery and Recrystallization

2012 ◽  
Vol 706-709 ◽  
pp. 2758-2763 ◽  
Author(s):  
W.J. Liu
Keyword(s):  
Stress Relaxation ◽  
Relaxation Rate ◽  
Relaxation Method ◽  
Dislocation Model ◽  
Precipitation Kinetics ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

Stress-relaxation method was first used by Liu and Jonas in 1980s for following the kinetics of strain induced precipitation of carbonitrides in austenite. Since then, the method has been widely employed for studying not only the precipitation kinetics but also the recovery and recrystallization processes in steels and other alloys. In the present paper, the principle and the worldwide usage of the method were reviewed. The dependence of stress relaxation rate on the occurrence of precipitation, recovery and recrystallization was interpreted based on a dislocation model. The capabilities and the limitations of the method were discussed and ways to overcome the existing limitations were also proposed.

Effect of the Root Gap on the Structure and Properties of High Strength Steel S700MC Welds

2021 ◽  
Vol 890 ◽  
pp. 201-208
Author(s):  
Nikolay Ferdinandov ◽  
Danail Gospodinov ◽  
Mariana Ilieva ◽  
Rossen Radev
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Pressure Vessels ◽  
Coarse Grained ◽  
Carbon Equivalent ◽  
Welding Parameters ◽  
Low Carbon ◽  
Negative Effect ◽  
Ultra High Strength Steels ◽  
Time Required

Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably in welded constructions. These steels are mainly exploited in heavy loaded welded constructions such as bridges, cranes and excavators, in pressure vessels, vehicles, ships, drilling rigs etc. working at room or lower temperatures. As the welded constructions have specific requirements, the development of high strength and ultra-high strength steels imposes the need for research on the factors influencing their weldability. Among the possible negative implications are: cold cracks formation, softening of the heat affected zone, brittleness in the coarse grained zone. When complying with the generally accepted rules for welding, HS and UHS are readily welded by all conventional welding methods. Recommendations for welding of steels after normalization, thermo-mechanical treatment and quenching and tempering are given in the standard EN 1011 -1, 2. The use of thermo-mechanically treated (hot-rolled) steels with low carbon equivalent, such as S700MC, allows reduction in time required for welding as the preheating temperature is lowered or even preheating is not necessary. A more pronounced negative effect on the weld quality has the presence of different defects. S700MC can be welded by all conventional methods, and a reduction in the softened zone can be achieved by using appropriate welding parameters. Joint preparation for welding of HS and UHS steels is described in the standards EN ISO 9692-1:2013 and EN ISO 9692-2:2001. Nevertheless, the root gap is often the closing part in constructions and does not comply with the standard recommendations. That is why the effect of the root gap on welds has to be researched. The present work introduces results of a research studying the effect of the root gap on the structure and some mechanical and technological properties of S700MS welds, welded by submerged arc welding.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

Texture analysis and joint performance of laser-welded similar and dissimilar dual-phase and complex-phase ultra-high-strength steels

2021 ◽  
Vol 174 ◽  
pp. 111035
Author(s):  
Ajit Kumar Pramanick ◽  
Hrishikesh Das ◽  
Ji-Woo Lee ◽  
Yeyoung Jung ◽  
Hoon-Hwe Cho ◽  
...  
Keyword(s):  
Texture Analysis ◽  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Complex Phase ◽  
Joint Performance ◽  
Ultra High Strength Steels
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