Influence of the niobium content on the kinetics of the phase transformations of austenite and mechanical properties in the heating area of welded connections of low-carbon high-strength steels

2020 ◽  
pp. 39-44
Author(s):  
I.Yu. Utkin ◽  
◽  
L.A. Efimenko ◽  
I.I. Frantov ◽  
O.E. Kapustin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Transformations ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Niobium Content ◽  
Kinetics Of

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.

State-of-Art High Strength Steel Sheets for the Automotive Application

2007 ◽  
Vol 539-543 ◽  
pp. 4369-4374 ◽  
Author(s):  
Toshiaki Urabe ◽  
Fusato Kitano ◽  
Takeshi Fujita ◽  
Yuji Yamasaki ◽  
Yoshihiro Hosoya
Keyword(s):  
Mechanical Properties ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Grain Structure ◽  
Solid Solution Hardening ◽  
Automotive Application ◽  
Continuous Annealing ◽  
Low Carbon ◽  
Body In White

New type of IF cold-rolled high strength steels (HSSs) with the strength level of 390 and 440MPa have been developed under the chemistry of the extra-low carbon steel containing around 60ppm C with an intentional addition of niobium by hybridizing the precipitation hardening with niobium carbides and the supplemental solid-solution hardening. In this steel, Precipitation Free Zone (PFZ) nearby recrystallized grain boundaries forms during continuous annealing. This structure leads to unique mechanical properties such as lower yielding and superior anti-secondary-work embrittlement under fine grain structure strictly required for the exposed panels in Body-in-White. Principles of the unique mechanical properties of the steel are introduced related with the formation of PFZ during annealing, and the results of further approach to improve them as the state-of-the-art product, which is widely used for the exposed panels in Body in White, are introduced in the paper.

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.

scholarly journals Low-Carbon Ti-Mo Microalloyed Hot Rolled Steels: Special Features of the Formation of the Structural State and Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1584
Author(s):  
Alexander Zaitsev ◽  
Nataliya Arutyunyan
Keyword(s):  
Mechanical Properties ◽  
High Strength Steels ◽  
High Strength ◽  
Ferrite Matrix ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Bulk System ◽  
Hot Rolled ◽  
New Generation ◽  
Technological Strength

Low-carbon Ti-Mo microalloyed steels represent a new generation of high strength steels for automobile sheet. Excellent indicators of difficult-to-combine technological, strength, and other service properties are achieved due to the superposition of a dispersed ferrite matrix and a bulk system of nanoscale carbide precipitates. Recently, developments are underway to optimize thermo-deformation processing for the most efficient use of phase precipitates. The review summarizes and analyzes the results of studies of mechanical properties depending on the chemical composition and parameters of hot deformation of low-carbon Ti-Mo microalloyed steels. Particular attention is paid to the features of the formation and the influence of various types of phase precipitates and the dispersion of the microstructure on mechanical properties. The advantages of Ti-Mo microalloying system and the tasks requiring further solution are shown.

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).

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.

The Study of Aging Cold Rolled and Hot Dip Galvanized Automotive Steel

2016 ◽  
Vol 870 ◽  
pp. 352-359
Author(s):  
L.V. Radionova ◽  
Yu.M. Subbotina
Keyword(s):  
Mechanical Properties ◽  
High Strength Steels ◽  
Storage Period ◽  
High Strength ◽  
Low Carbon ◽  
Iron And Steel ◽  
Warranty Period ◽  
Delivery Date ◽  
Automotive Steel ◽  
Iron And Steel Works

This paper provides the study of aging hot dip galvanized rolled products of low-carbon high-resistance automotive steels featuring good formability, weldability and dent-resistance. The authors carried out the experiment to obtain data on the period of warranty of mechanical properties of rolled products manufactured at OJSC Magnitogorsk Iron and Steel Works at storage and processing at the customer's site. The following assortment of hot-dip galvanized rolled products was selected for the experiment: 08ps and DX52D steels rolled coated products, rolled products of high-strength HX220YD and 006/IFgr steels as well as those of high-strength steels hardening at coating afterbaking – HX180BD and A341-A5. Tensile test was carried out at the experimental stage to determine changes of mechanical properties of the assortment under study due to aging. Based on the experimental outcome, the graphs were plotted, which clearly demonstrated changes of mechanical properties of rolled products due to aging. It has been found that the warranty period for mechanical properties of hot-dip galvanized rolled products of DX52D, HX220YD and 006/IFgr steels is 3 to 6 months since the confirmation of the delivery date; the storage period for hot-dip galvanized rolled products of HX180BD and A341-A5 steels shall be no more than 3 months. Aging 08ps steel hot-dip galvanized rolled products begins in as little as 10 days.

scholarly journals Using Intercritical CCT Diagrams and Multiple Linear Regression for the Development of Low-Alloyed Advanced High-Strength Steels

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1768
Author(s):  
Bryan Y. Navarrete Pino ◽  
Antonio A. Torres Castillo ◽  
Emmanuel J. Gutiérrez Castañeda ◽  
Luis A. Espinosa Zúñiga ◽  
Lorena Hernández Hernández ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Linear Regression ◽  
Multiple Linear Regression ◽  
Phase Transformations ◽  
High Strength Steels ◽  
High Strength ◽  
Uniaxial Tensile ◽  
Third Generation ◽  
Thermal Cycles ◽  
Advanced High Strength Steels

The present work presents a theoretical and experimental study regarding the microstructure, phase transformations and mechanical properties of advanced high-strength steels (AHSS) of third generation produced by thermal cycles similar than those used in a continuous annealing and galvanizing (CAG) process. The evolution of microstructure and phase transformations were discussed from the behavior of intercritical continuous cooling transformation diagrams calculated with the software JMatPro, and further characterization of the steel by scanning electron microscopy, optical microscopy and dilatometry. Mechanical properties were estimated with a mathematical model obtained as a function of the alloying elements concentrations by multiple linear regression, and then compared to the experimental mechanical properties determined by uniaxial tensile tests. It was found that AHSS of third generation can be obtained by thermal cycles simulating CAG lines through modifications in chemistry of a commercial AISI-1015 steel, having an ultimate tensile strength of UTS = 1020–1080 MPa and an elongation to fracture of Ef = 21.5–25.3%, and microstructures consisting of a mixture of ferrite phase, bainite microconstituent and retained austenite/martensite islands. The determination coefficient obtained by multiple linear regression for UTS and Ef was R2 = 0.94 and R2 = 0.84, respectively. In addition, the percentage error for UTS and Ef was 2.45–7.87% and 1.18–16.27%, respectively. Therefore, the proposed model can be used with a good approximation for the prediction of mechanical properties of low-alloyed AHSS.

Precipitation Strengthening in a Low Carbon Nb-Microalloyed Steel

2005 ◽  
Vol 500-501 ◽  
pp. 481-488 ◽  
Author(s):  
D.Q. Bai ◽  
F. Hamad ◽  
J. Asante ◽  
S. Hansen
Keyword(s):  
Mechanical Properties ◽  
Microalloyed Steel ◽  
High Strength Steels ◽  
Aging Treatment ◽  
High Strength ◽  
Precipitation Strengthening ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Nb Microalloyed Steel ◽  
Carbon Microalloyed

Among modern weldable high strength steels, low carbon microalloyed steels have been widely used for linepipe, construction, and automobile industries. One of the major technical components to successfully produce these steels is to effectively use precipitation strengthening. In the present paper, the effect of an aging treatment on the microstructure and mechanical properties of a low carbon Nb-microalloyed steel is analyzed.

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