scholarly journals Interaction between Microalloying Additions and Phase Transformation during Intercritical Deformation in Low Carbon Steels

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1049 ◽  
Author(s):  
Unai Mayo ◽  
Nerea Isasti ◽  
Jose M. Rodriguez-Ibabe ◽  
Pello Uranga
Keyword(s):  
Rolling Process ◽  
Bearing Steel ◽  
Phase Region ◽  
Carbon Steels ◽  
Transformation Model ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Electron Backscattered Diffraction ◽  
Two Phase ◽  
Line Pipe

Heavy gauge line pipe and structural steel plate materials are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends, and the exact effect of each rolling process parameter remains unclear. Even though intercritical rolling has been widely studied, the specific mechanisms that act when different microalloying elements are added remain unclear. To investigate this further, laboratory thermomechanical simulations reproducing intercritical rolling conditions were performed in plain low carbon and NbV-microalloyed steels. Based on a previously developed procedure using electron backscattered diffraction (EBSD), the discretization between intercritically deformed ferrite and new ferrite grains formed after deformation was extended to microalloyed steels. The austenite conditioning before intercritical deformation in the Nb-bearing steel affects the balance of final precipitates by modifying the size distributions and origin of the Nb (C, N). This fact could modify the substructure in the intercritically deformed grains. A simple transformation model is proposed to predict average grain sizes under intercritical deformation conditions.

Strengthening Low Carbon Steels for Oil and Gas Spiral Welded Pipes

2006 ◽  
Author(s):  
I. Yu. Pyshmintsev ◽  
D. A. Pumpyanskyi ◽  
Yu. O. Kamenskih ◽  
I. N. Poznyakovsky ◽  
I. L. Permyakov
Keyword(s):  
Oil And Gas ◽  
Controlled Rolling ◽  
Carbon Steels ◽  
Low Carbon ◽  
Line Pipe ◽  
Low Carbon Steels ◽  
Factors Affecting ◽  
Steel Processing ◽  
Line Pipe Steel ◽  
Strain Hardening Behavior

Strengthening mechanisms applied for modern line pipe steel design were studied. Low carbon steels alloyed with Mn, Mo, V, Nb processed by the way of controlled rolling were developed for spiral welded X65-X80 line pipes up to 1420 mm diameter. Formation of the microstructure during steel processing was studied. The effects of typical microstructure for the steels on mechanical properties, strain hardening behavior and Bauschinger effect were studied. Main metallurgical factors affecting on strength measured in plates and pipes were revealed using physical and computer simulations.

Effect of the Time between Last Deformation Pass and Accelerated Cooling on the Mechanical Properties in Nb and Nb-Mo Microalloyed Steels

2016 ◽  
Vol 716 ◽  
pp. 281-290
Author(s):  
Gorka Larzabal ◽  
Nerea Isasti ◽  
J.M. Rodriguez-Ibabe ◽  
Isabel Gutiérrez ◽  
P. Uranga
Keyword(s):  
Mechanical Properties ◽  
Charpy Impact ◽  
Holding Time ◽  
Microalloyed Steels ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Microstructural Refinement ◽  
Deformation Pass

The microstructural refinement induced when the holding time between last deformation pass and accelerated cooling is reduced, affects the mechanical properties in low carbon Nb and Nb-Mo microalloyed steels. Plane strain compression tests were performed and mechanical property samples machined in order to quantify this effect using tensile and Charpy impact tests. A complete microstructural characterization was carried out using electron backscattered diffraction (EBSD) measuring unit size distributions and homogeneity of complex microstructures. The synergetic combination of Nb and Mo elements modifies the final microstructures and, therefore, affects the contribution of different strengthening mechanisms, such as substructure, precipitation hardening and dislocation density. Even though strength is not clearly affected by the reduction of the holding time after the last deformation pass, Charpy properties are considerably improved in the case of the Nb steel. The presence of MA islands in the Nb-Mo steel limits the beneficial effect of the microstructural refinement and toughness remains unmodified.

Issues in Welding of HSLA Steels

2011 ◽  
Vol 365 ◽  
pp. 44-49 ◽  
Author(s):  
Sandeep Jindal ◽  
Rahul Chhibber ◽  
N.P. Mehta
Keyword(s):  
Structural Integrity ◽  
Hsla Steel ◽  
Weight Ratio ◽  
Welding Process ◽  
Pressure Vessels ◽  
Carbon Steels ◽  
Low Carbon ◽  
Line Pipe ◽  
Hsla Steels ◽  
Selection Of

The application of High Strength Low Alloy (HSLA) steels has expanded to almost all fields viz. automobile industry, ship building, line pipe, pressure vessels, building construction, bridges, storage tanks. HSLA steels were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higher-strength materials. Due to higher-strength and added excellent toughness and formability, demand for HSLA steel is increasing globally. With the increase of demand; other issues like the selection of filler grade and selection of suitable welding process for the joining of these steels have become very significant. This paper discusses the various issues regarding selection of suitable grade and selection of suitable welding process for joining of HSLA steels and issues concerning the structural integrity of HSLA steel welds.

scholarly journals Effect of High Ti Contents on Austenite Microstructural Evolution During Hot Deformation in Low Carbon Nb Microalloyed Steels

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 165 ◽  
Author(s):  
Leire García-Sesma ◽  
Beatriz López ◽  
Beatriz Pereda
Keyword(s):  
Microstructural Evolution ◽  
Hot Deformation ◽  
Solute Drag ◽  
Carbon Steels ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Grain Sizes ◽  
Austenite Recrystallization ◽  
Pancaked Austenite

This work has focused on the study of hot working behavior of Ti-Nb microalloyed steels with high Ti contents (> 0.05%). The role of Nb during the hot deformation of low carbon steels is well known: it mainly retards austenite recrystallization, leading to pancaked austenite microstructures before phase transformation and to refined room temperature microstructures. However, to design rolling schedules that result in properly conditioned austenite microstructures, it is necessary to develop models that take into account the effect of high Ti concentrations on the microstructural evolution of austenite. To that end, in this work torsion tests were performed to investigate the microstructural evolution during hot deformation of steels microalloyed with 0.03% Nb and different high Ti concentrations (0.05%, 0.1%, 0.15%). It was observed that the 0.1% and 0.15% Ti additions resulted in retarded softening kinetics at all the temperatures. This retardation can be mainly attributed to the solute drag effect exerted by Ti in solid solution. The precipitation state of the steels after reheating and after deformation was characterized and the applicability of existing microstructural evolution models was also evaluated. Determined recrystallization kinetics and recrystallized grain sizes reasonably agree with those predicted by equations previously developed for Nb-Ti microalloyed steels with lower Ti concentrations (<0.05%).

Effect of the Coupling of Recovery and Precipitation on the Recrystallization Behavior of Ti-Stabilized Extra Low Carbon Steels

2004 ◽  
Vol 467-470 ◽  
pp. 299-304 ◽  
Author(s):  
Eun Hye Na ◽  
Jae Young Choi ◽  
Baek-Seok Sung ◽  
Hu Chul Lee
Keyword(s):  
Annealing Treatment ◽  
Rolling Process ◽  
Carbon Steels ◽  
Recrystallization Temperature ◽  
Chemical Extraction ◽  
Recrystallization Behavior ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Alloy Chemistry ◽  
Relaxation Curves

The effect of carbo-nitride precipitation on the recrystallization behavior of Ti-stabilized extra low carbon steels was investigated. The precipitation behavior of titanium carbo-nitride was analyzed using transmission electron microscopy (TEM), a chemical extraction method, and the small angle neutron scattering (SANS) method. The recrystallization temperature was varied from 590°C to 680°C depending on the alloy chemistry and hot rolling process. The total amount of precipitates in the hot bands did not significantly affect the recrystallization temperature of the alloys. Isothermal annealing treatment showed a plateau in the stress relaxation curves, i.e. a delay in the recovery, when precipitation occurred during the annealing treatment. A model developed to explain the dynamic interaction of the precipitation with the recovery in the microalloyed austenite was successfully adopted to simulate the delay of the recovery during the recrystallization treatment of the cold rolled Ti-stabilized extra low carbon steels.

Influence of Strain Path on Microstructure Evolution of Low Carbon Steels

2010 ◽  
Vol 638-642 ◽  
pp. 3418-3423 ◽  
Author(s):  
K. Muszka ◽  
Lin Sun ◽  
Bradley P. Wynne ◽  
Eric J. Palmiere ◽  
Mark W. Rainforth
Keyword(s):  
Strain Path ◽  
Processing Parameters ◽  
Carbon Steels ◽  
Microalloyed Steels ◽  
Precipitation Process ◽  
Nucleation Density ◽  
Low Carbon ◽  
Dynamic Recrystallisation ◽  
Important Processing ◽  
Strain Path Change

Changes in strain path represent one of the most important processing parameters that characterise hot metal forming processes. In the present study, the effect of strain path change on dynamic recrystallisation, strain-induced precipitation processes and phase transformation behaviour in plain carbon and Nb-microalloyed steels was investigated. To assess the effect of strain-path change, forward/forward and forward/reverse torsion tests were conducted. It has been shown that the strain reversal delays the dynamic recrystallisation kinetics whereas its effect on strain-induced precipitation process of Nb(C,N) is rather negligible. Also the onset of austenite-ferrite transformation is delayed; its products however doesn’t change significantly. This can be due to the fact that ferrite nucleation density plays the second order role compared to the geometry of deformation.

New Trends and Technologies in Thin-Slab Direct Rolling: Improved Microstructure & Mechanical Behavior

2012 ◽  
Vol 706-709 ◽  
pp. 2752-2757 ◽  
Author(s):  
Christian Klinkenberg ◽  
C. Bilgen ◽  
J.M. Rodriguez-Ibabe ◽  
Beatriz López ◽  
P. Uranga
Keyword(s):  
Rolling Process ◽  
Recrystallization Temperature ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Thin Slab ◽  
Present Contribution ◽  
Thin Slab Casting ◽  
Finishing Mill ◽  
Direct Rolling ◽  
Cast Microstructure

The use of CSP®thin slab casting followed by direct thermomechanical rolling is well placed for the production of low-carbon Nb microalloyed steels. In this process thin slabs of between 48 and 90 mm thickness are cast and directly hot rolled to hot strip typically between 1 and 12 mm thick. To obtain optimum strength and toughness property combinations in a direct rolling process, hot rolling has to compact the dendritic as-cast microstructure and to achieve a fine-grained microstructure. This affords a two-stage rolling strategy with start rolling above the recrystallization stop temperature and finish rolling in the non-recrystallization temperature range. Temperature and deformation in the first stand should be as high as possible in order to delete the initial as-cast microstructure by complete recrystallization. Based on these considerations, SMS Siemag further developed the CSP®concept including features allowing isothermal rolling in the first stands of the finishing mill. The present contribution gives the results of a laboratory study of this innovative approach. The report concludes with resulting new plant configurations for improved high strength and API linepipe grade production.

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