Effect of Vanadium-Nitrogen Concentration and Cooling Rate on Grain Refinement in V-N Steel

2012 ◽  
Vol 538-541 ◽  
pp. 1138-1144
Author(s):  
Xiao Fang Shi ◽  
Li Zhong Chang ◽  
Chun Feng Jiang ◽  
Lin Bao Liang
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Nitrogen Concentration ◽  
Bearing Steel ◽  
Good Strength ◽  
Pearlite Content ◽  
The Cost ◽  
Ferrite Grain Size ◽  
Strength And Toughness

Effect of vanadium and nitrogen concentration in V-N steel and cooling rate after deformation on grain refinement has studied in this paper. The results show that with the increase of vanadium and nitrogen concentration, ferrite grain size is smaller compared with carbon steel; with the increase of cooling rate after deformation, ferrite grain size is finer and pearlite content of microstructure significantly is reduced too. Compared with the Nb-bearing steel, as long as selecting reasonable the process parameters and adding the appropriate vanadium, nitrogen to the steel, V-N steel can also get a good strength and toughness, and the cost is lower than Nb-bearing steel. This method of producing the steel with good Strength and toughness is very suitable to China who possesses the abundant vanadium resource, but is lack of niobium.

Grain Refinement of Commercial Al-Mg Alloy Using Severe Torsion Straining Process

2006 ◽  
Vol 503-504 ◽  
pp. 955-960 ◽  
Author(s):  
Koji Neishi ◽  
Akihiko Higashino ◽  
Yuichi Miyahara ◽  
Katsuaki Nakamura ◽  
Kenji Kaneko ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Rotation Speed ◽  
Imaging System ◽  
Continuous Process ◽  
Critical Ratio ◽  
Heated Zone ◽  
Moving Speed

Severe plastic deformation (SPD) makes it possible to refine grain size in many metallic materials. Recently, we have developed a new SPD process designated the severe torsion straining process (STSP). This process requires no die but one side of a rod is rotated with respect to the other while producing a local heated zone in the rod and cooling both sides of the heated zone. Torsion strain is then introduced in the local heated zone. The STSP can be a continuous process because the rod is moved in the longitudinal direction while introducing torsion strain through the rotation. For grain refinement using the STSP, various factors may affect, which are the rotation speed, moving speed, straining temperature, cooling rate and diameter of the rod. In this study, the STSP is applied to grain refinement of an A5056 Al-Mg commercial alloy and the factors affecting the grain refinement are optimized. STSP was conducted at a temperature in the range from 573K to 723K. Microstructure was observed by optical microscopy, scanning electron microscopy with an orientation imaging system, and transmission electron microscopy. Microscopy observations revealed that the grain size was reduced to ~0.9 μm, when STSP was conducted at 573K with a rotation speed of 10 rpm and moving speed of 50 mm/min. There is a critical ratio of rotation speed to moving speed above which the rod breaks. The grain size tends to be finer as the straining temperature is lower, the cooling rate is faster and the ratio of rotation speed to moving speed is closer to the critical value.

Grain Refinement Mechanisms of Plain C-Mn Steel by Super Short Interval Multi-Pass Rolling in Stable Austenite Region

2010 ◽  
Vol 638-642 ◽  
pp. 3406-3411
Author(s):  
Kaori Miyata ◽  
Masayuki Wakita ◽  
S. Fukushima ◽  
Toshiro Tomida
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Short Interval ◽  
Model Alloy ◽  
Fe Model ◽  
Transformation Mechanisms ◽  
Hot Rolled ◽  
Mn Steel ◽  
Ferrite Grain Size ◽  
Dislocation Walls

One of noble grain refinement methods to attain ferrite grain size of around 1m in plain C-Mn steel has been so-called super short interval multi-pass rolling (SSMR) process, which is characterized by finish-rolling above Ae3, extreme short interpass time and then rapid cooling. The transformation mechanisms are demonstrated by the microstructural observation of an fcc Ni-Fe model alloy and C-Mn steels. In the Ni-Fe alloy hot-rolled by SSMR, equiaxed and cellar array of dislocation walls with low and high angle misorientations are observed in shear directions without recrystallization. The average spacing between the dislocation walls in the Ni-Fe alloy is in good agreement with the ferrite grain size of the C-Mn steel by SSMR process. On the other hand, in the C-Mn steel quenched to bypass ferrite transformation, the fine ferrite nuclei have been identified along intra-granular shear directions in the quenched martensite. It is concluded that the dislocation substructure in heavily deformed austenite by SSMR process have high potency as inherited ferrite nucleation

Controlling the Semisolid Grain Size during Solidification

2008 ◽  
Vol 141-143 ◽  
pp. 355-360 ◽  
Author(s):  
David H. StJohn ◽  
Mark Easton ◽  
Ma Qian
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Ultrasonic Treatment ◽  
Solidification Process ◽  
New Method ◽  
Grain Refining ◽  
Nucleation Event ◽  
Particle Characteristics ◽  
Semi Solid

This paper will use a new method for predicting grain size and then apply it to various solidification environments to reveal which factors are dominant in determining the final grain size. This study will only focus on methods where the grain size is set during a solidification process. These processes include grain refinement by inoculation of the melt with grain refining particles, increasing the cooling rate, low superheat casting, ultrasonic treatment and the use of chill moulds. Each of these methods can control the grain size to some extent but in order to predict the outcome it needs to be understood how the alloy constitution, inoculant particle characteristics and the casting conditions affect the prime nucleation event for the formation of new grains. These methodologies are currently being used, or have potential to be used, for the production of fine spherical grained semi-solid slurries.

Microstructure and Mechanical Properties of X80 Induction Heating Bends

2013 ◽  
Vol 762 ◽  
pp. 158-164
Author(s):  
Liu Qing Yang ◽  
Yu Liu ◽  
Bin Feng ◽  
Yu Ran Fan ◽  
Deng Zun Yao
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Induction Heating ◽  
Heating Temperature ◽  
Tensile Tests ◽  
Granular Bainite ◽  
Metallographic Analysis ◽  
Good Strength ◽  
Microstructure And Mechanical Properties ◽  
Strength And Toughness

By using physical thermal simulation technology, combined with metallographic analysis, tensile tests, impact and hardness tests, effects of heating temperature and cooling speed on microstructure and mechanical properties of X80 induction heating bends were investigated. The results show that as the heating temperature rises, TS of X80 induction heating bends increases gradually. However, when the heating temperature rises above 1100°C, plasticity and toughness of the bends begin to decrease, and grain growth tends to be obvious. When the heating temperature is 1050°C, X80 induction heating bends have a good strength and toughness. As the cooling rate increases, strength and toughness of X80 bends are improved considerably. In the cooling rate range between 20°C/s and 30°C/s, the microstructure of X80 bends is mainly composed of polygonal ferrite and granular bainite. Due to the very high dislocation density inside granular bainite and the fine and dispersed M-A constituents, X80 induction heating bends have a very good strength and toughness.

EFFECT OF DEFORMATION-INDUCED TRANSFORMATION PROCESS ON FERRITE GRAIN SIZE AND VOLUME FRACTION IN STEEL 12CR1MOV

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1197-1202
Author(s):  
QINGFEN LI ◽  
XIUFANG CUI ◽  
HONGBIN CHEN
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Cooling Rate ◽  
Deformation Temperature ◽  
Volume Fraction ◽  
Rolling Process ◽  
Controlled Rolling ◽  
Temperature Deformation ◽  
Controlled Cooling ◽  
Ferrite Grain Size

Effect of deformation induced transformation (DIT) process on ferrite grain size and ferrite transformation volume fraction in the refractory low alloy steel 12 Cr 1 MoV by controlled rolling and controlled cooling technology were experimentally studied. Simulation experiments of hot deformation were carried out with the Gleeble-1500 system. Single-pass and multi-pass hot rolling process with different deformation temperature, deformation reduction, strain rate and cooling rate were performed separately. The ferrite grain size decreased and the ferrite volume fraction increased with decreasing deformation temperature, and the extra-fine ferrite grain about 1.01µm was obtained when the deformation temperature reached 780°C. Higher deformation reduction resulted finer ferrite grain size and higher ferrite volume fraction. Both the ferrite grain size and ferrite volume fraction decreased with increasing strain rate. The ferrite grain size decreased but the ferrite volume fraction didn't change much when the cooling rate increased. The grain size and the ferrite volume fraction were improved more by three-passes than two-passes rolling. The mechanism of grain refinement by DIT was discussed.

scholarly journals Development of New Oxide Based Master Alloys and their Grain Refinement Potency in Aluminium Alloys

2015 ◽  
Vol 828-829 ◽  
pp. 23-28 ◽  
Author(s):  
Vadakke Madam Sreekumar ◽  
N. Hari Babu ◽  
Dmitry G. Eskin ◽  
Z. Fan
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Grain Refinement ◽  
Master Alloy ◽  
Aluminium Alloys ◽  
Al Alloys ◽  
Ultrasonic Cavitation ◽  
Size Reduction ◽  
Refinement Efficiency ◽  
Master Alloys

In this study, grain refinement efficiency of a new oxide master alloy based on MgAl2O4 was demonstrated in Al alloys. The grain size of the reference alloy was reduced by 50-60% with the addition of the master alloy and introduction of ultrasonic cavitation. While cooling rate has an influence on the grain size reduction, higher levels of addition of master alloy was found to be not effective in further reducing the grain size.

Continuous Cooling Transformation Temperatures and Microstructures of Niobium Bearing Microalloyed Steels

2005 ◽  
Vol 475-479 ◽  
pp. 65-68 ◽  
Author(s):  
Young Kook Lee ◽  
Jin-Myung Hong ◽  
Chong Sool Choi ◽  
Jae Kon Lee
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Bainitic Ferrite ◽  
Polygonal Ferrite ◽  
Microalloyed Steels ◽  
Niobium Content ◽  
Transformation Temperatures ◽  
Carbon Microalloyed ◽  
Ultralow Carbon ◽  
Ferrite Grain Size

Effects of niobium content and cooling rate on ferrite and bainite start temperatures (Ar3, Bs) and microstructural features have been studied in niobium bearing ultralow carbon microalloyed steels. The Ar3 and Bs temperatures decrease as niobium content or cooling rate is increased. The dependence of Ar3 on cooling rate is greater than that of Bs in all niobium contents. The bainitic ferrite laths become longer and narrower with increasing niobium content and cooling rate, and niobium also shows a tendency to decrease polygonal ferrite grain size.

Microstructure Evolution in Fine-Grained Microalloyed Steels

2005 ◽  
Vol 500-501 ◽  
pp. 347-354 ◽  
Author(s):  
K.R. Lottey ◽  
Matthias Militzer
Keyword(s):  
Grain Size ◽  
Cooling Rate ◽  
Work Hardening ◽  
Transformation Model ◽  
Austenite Grain Size ◽  
Transformation Behaviour ◽  
Grain Sizes ◽  
Austenite Grain ◽  
Cooling Conditions ◽  
Ferrite Grain Size

There is an increasing emphasis to develop novel hot-rolled high strength steels with fine and ultra fine grain sizes for structural and other applications. Traditionally the concept of microalloying has been employed to refine microstructures thereby obtaining increased strength levels. For example, employing an alloying strategy with Nb, Ti and Mo is promising to attain yield strength levels of 700MPa and beyond. In the present study, the transformation behaviour is investigated for a HSLA steel containing 0.05wt%C-1.65wt%Mn-0.20wt%Mo-0.07wt%Nb- 0.02wt%Ti. The ferrite formation from work-hardened austenite has been studied for simulated run-out table cooling conditions employing a Gleeble 3500 thermomechanical simulator equipped with a dilatometer. The effects of cooling rate and initial austenite microstructure, i.e. austenite grain size and degree of work hardening, on the austenite decomposition kinetics and resulting ferrite grain size have been quantified. Based on the experimental results, a phenomenological transformation and ferrite grain size model is proposed for run-out table cooling conditions. The transformation model includes submodels for transformation start and ferrite growth. The latter is described using a Johnson-Mehl-Avrami-Kolmogorov approach. The degree of work hardening is incorporated by introducing an effective austenite grain size as a function of the strain applied under no-recrystallization condition. The ferrite grain size can be predicted as a function of the transformation start temperature. Increasing both cooling rate and amount of work hardening can optimize ferrite grain refinement. In the present steel, ferrite grain sizes of as low as 2µm have been obtained in this way. The results observed for the present steel are compared to the transformation behaviour in previously studied Nb-Ti HSLA steels of similar strength levels.

Factors Limiting the Achievable Ferrite Grain Refinement in Hot Worked Microalloyed Steels

2005 ◽  
Vol 500-501 ◽  
pp. 355-362 ◽  
Author(s):  
E. Novillo ◽  
E. Cotrina ◽  
Amaia Iza-Mendia ◽  
Beatriz López ◽  
Isabel Gutiérrez
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Hot Rolling ◽  
Rolling Mill ◽  
Solute Drag ◽  
Microalloyed Steels ◽  
Rolling Mills ◽  
Hot Rolling Mill ◽  
Conventional Rolling ◽  
Ferrite Grain Size

Nb is added to C-Mn steels in order to use the solute drag and/or strain induced precipitation as a useful tool to condition the austenite in the hot rolling mill and produce during the subsequent cooling a refined ferrite grain size. The highest degree of refinement is obtained in conventional rolling mills by accumulating the deformation in austenite during the last passes, followed by early cooling in the run out table to produce a high density of nucleated ferrite grains. However, the maximum refinement is to a certain extent attenuated due to the ferrite grain coarsening taking place during the transformation. The present work analyses the different aspects limiting the final achievable ferrite grain refinement.

Texture Formation in High Strength Low Alloy Steel Reheated with Ultrafast Heating Rates

2011 ◽  
Vol 702-703 ◽  
pp. 798-801 ◽  
Author(s):  
Roumen H. Petrov ◽  
Jurij J. Sidor ◽  
Leo Kestens
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Electron Backscatter Diffraction ◽  
Hsla Steel ◽  
Rolling Texture ◽  
Deformation Texture ◽  
Austenite Formation ◽  
Texture Formation ◽  
Heating Rates ◽  
Ferrite Grain Size

Texture formation during annealing of a 95% cold rolled HSLA steel with 10°C/s and ~3000°C/s was studied with the purpose to investigate the interaction between the recrystallization and the austenite formation as well as the possibility of grain refinement. The recrystallization and austenite formation were monitored by means of optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). It was found that at extreme reheating rates of 1000°C/s and higher, the α-γ phase transformation starts before the completion of recrystallization and the deformation texture is partially retained in the samples after annealing. The crystallographic texture observed in the martensitic phase which is the product of intercritical austenite transformation in as-quenched samples, i.e. after the double α-γ-α’ transformation, is the same as the initial cold rolling texture, which is an indication for the texture memory effect. After ultra fast reheating with average reheating rates of 1000°C/s and higher a significant grain refinement was observed with an average ferrite grain size of ~1µm. The obtained final ferrite grain size depends significantly on both the reheating temperature and the reheating rate.

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