Refinement of Solidification Microstructure and Austenite Grain by Fine Inclusion Particles

Suito, Hideaki; Ohta, Hiroyuki; Morioka, Shuhei

doi:10.2355/isijinternational.46.840

Cited by 69 publications

(41 citation statements)

References 8 publications

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“…17 The occurrence of d-ferrite islands is less frequent in the PK942Zr sample, which may be explained by the fact that ZrO 2 is a heterogeneous nucleation site during the solidification of austenite, therefore inhibiting d-ferrite nucleation. 18 This can be beneficial as d-ferrite can be harmful to the final properties and the hot working is reduced by annealing. 19 Other than the difference in d-ferrite, there are no significant differences in the microstructure.…”

Section: Resultsmentioning

confidence: 99%

De-oxidation of PK942 steel with Ti and Zr

Koležnik¹,

Burja²,

Batič³

et al. 2017

Mater. Tehnol.

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The effects of titanium and zirconium additions on the non-metallic inclusions and microstructure of PK942 (X11CrNiMo12) steel were investigated. Laboratory steel charges with additions of Ti, Zr and a combination of both elements were melted. The inclusions' size, quantity, distribution and composition were analysed using optical and scanning electron microscopy (SEM). Other than the difference in d-ferrite quantity, there are no significant differences in the microstructure. The Ti and Zr additions had a significant effect on the non-metallic inclusions, and while the addition of Ti did have an effect on the composition of inclusions, the addition of Zr also had a great effect on the size distribution and the number of non-metallic inclusions. The result of the Zr addition was a large reduction in the total non-metallic inclusion surface area. The additions of both titanium and zirconium had similar effects to the addition of Zr. Thermodynamic reactions were considered to explain the modification of the non-metallic inclusions. Keywords: non-metallic inclusions, clean steel, de-oxidation with Ti, de-oxidation with Zr, creep resistant steel S pomo~jo opti~ne ter elektronske mikroskopije se je preiskal vpliv dezoksidacije jekla PK942 (X11CrNiMo12) s cirkonijem, titanom ter kombinacijo obeh. Poudarek raziskave je bil na spremembi velikosti, razporeditve ter sestave nekovinskih vklju~kov v jeklu PK942. Razen v majhni razliki dele`a d-ferita, ni bilo bistvenega vpliva na osnovno mikrostrukturo jekla. Ve~ji vpliv pa se je pokazal na velikost, {tevilo ter kemi~no sestavo nekovinskih vklju~kov. Analiza nekovinskih vklju~kov je pokazala, da Ti vpliva predvsem na kemi~no sestavo, med tem ko ima Zr zelo velik vpliv tudi na velikostno porazdelitev ter {tevilo nekovinskih vklju~kov, rezultat~esar je manj{i skupni povr{inski dele`nekovinskih vklju~kov. Dodatek kombinacije Zr in Ti ima podoben vpliv kot dodatek Zr, vendar v manj{em obsegu. Pri razlagi modifikacije vklju~kov so se upo{tevale osnovne termodinami~ne reakcije oksidacije.

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Section: Resultsmentioning

confidence: 99%

De-oxidation of PK942 steel with Ti and Zr

Koležnik¹,

Burja²,

Batič³

et al. 2017

Mater. Tehnol.

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“…When the volume fraction of second phase particles is large, the interparticle spacing may have the same value or smaller value than the grain size and Eq. [9] would no longer be applicable. Considering the effects of boundary-particle correlation, the following equation is used to estimate the maximum pinning pressure P ZC , when all the particles are located at the grain corners: [32][33][34][35] …”

Section: B Austenite Particle Pinning Effectsmentioning

confidence: 99%

“…Some authors proposed the use of oxide dispersions to pin grain growth at high temperatures. [8,9] While promising results have been obtained using this approach, the main challenges are how to produce fine dispersions of these particles in the caster. In the absence of particle pinning, austenite grains in excess of 2 mm may form prior to the onset of thermomechanical processing.…”

Section: Introductionmentioning

confidence: 99%

Model Fe-Al Steel with Exceptional Resistance to High Temperature Coarsening. Part I: Coarsening Mechanism and Particle Pinning Effects

Zhou

Zurob

O’Malley

et al. 2014

Metall Mater Trans A

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The mechanism by which austenite particles coarsen in a delta-ferrite matrix was investigated in a model Al-containing steel. Special emphasis was placed on the effect of volume fraction on the coarsening kinetics as well as the ability of the particles to pin the growth of delta-ferrite grains. The specimens were heated to temperatures in the range of 1123 K to 1583 K (850°C to 1305°C) in the austenite plus delta-ferrite two-phase region and held for times between 5 minutes and 288 hours, followed by water quenching. When the reheating temperature was higher than 1473 K (1200°C), the coarsening of austenite particles was found to evolve as t 1/3 , which is typical of volume diffusion-controlled behavior. For lower temperatures, the particle coarsening behavior followed t 1/4 kinetics which is consistent with a grain boundary diffusioncontrolled process. The observations were interpreted in terms of the modified LifshitzSlyozov-Wanger theory by considering multi-component diffusion, particle volume fraction, and the fact that this two-phase material is a non-ideal solid solution. Three types of interaction between particle coarsening and grain growth were observed. Grain growth was completely pinned when the particle pinning force was much larger than the driving force for grain growth. When the particle pinning force was comparable to the driving force for grain growth, the deltaferrite grains were observed to grow at a rate which is controlled by the kinetics of coarsening of the austenite particles. Finally, when the particle pinning force was smaller than the driving force for grain growth, significant grain growth occurred but its rate was lower than that expected in the absence of particle pinning. The results point to an effective approach for controlling grain growth at high temperatures.

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“…In the previous paper, 28) it has been reported that the density of ferrite precipitation didn't have a clear dependence with Zener's pining force 51) or austenite grain size, but a correlation seemed to exist with the particle size. Figure 12 shows the relationship between the inclusion density and ferrite density obtained the experiments as shown Fig.…”

Section: Ferrite Precipitationmentioning

confidence: 99%

Micro-structure Refinement in Low Carbon High Manganese Steels through Ti-Deoxidation, Characterization and Effect of Secondary Deoxidation Particles

Kikuchi¹,

Nabeshima²,

Yamashita³

et al. 2011

ISIJ Int.

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This paper investigates the effect of de-oxidation inclusions on micro-structure in low carbon (0.07 mass%), high Mn (0.9 mass%) steel. De-oxidation tests were carried out by adding either aluminum (0.05 mass%) or titanium (0.05, 0.03 or 0.015 mass%) to an iron melt in a 400 g-scale vacuum furnace. A Confocal Scanning Laser Microscope (CSLM) was used to evaluate the effect of cooling rate by re-melting and quenching during solidification. Fine secondary de-oxidation particles were obtained in the Ti-killed samples, and the particle density increased with increasing oxygen content, and their size decreased with increasing the cooling rate during solidification.The secondary Ti de-oxidation particles were found to have an effect on microstructure evolution, such as solidifying microstructure, austenite grain growth and austenite decomposition. The de-oxidation particles were examined through FE-TEM and were identified to be TiO, MnTiO3 and Mn2TiO4, in low oxygen ([O]=7 ppm) and high oxygen ([O]=56, 81 ppm) Ti-killed steels respectively, which were qualitatively same as those predicted by thermodynamic calculations. Stabilities of TiO, MnTiO3 and Mn2TiO4 are influenced by Mn presence. Composition change and decomposition of oxide were estimated through thermodynamic calculations. The effect of the particles on ferrite formation was evaluated through thermo-mechanical treatments. TiO was the most effective for promoting ferrite formation through heterogeneous nucleation. The particles contributed to ferrite formation in the following order, TiO>TiN>MnS> MnTiO3>Ti2O3.It was found that the secondary Ti de-oxidation particles work are engulfed by the advancing solid phase during solidification based on analysis with PET (Pushing Engulfment Transition) velocity, particle sizes and solidification rates. The particles at dendrite tips and inter-dendritic regions are likely restraining the molten steel flow resulting in a finer solidification microstructure.

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Refinement of Solidification Microstructure and Austenite Grain by Fine Inclusion Particles

Cited by 69 publications

References 8 publications

De-oxidation of PK942 steel with Ti and Zr

De-oxidation of PK942 steel with Ti and Zr

Model Fe-Al Steel with Exceptional Resistance to High Temperature Coarsening. Part I: Coarsening Mechanism and Particle Pinning Effects

Micro-structure Refinement in Low Carbon High Manganese Steels through Ti-Deoxidation, Characterization and Effect of Secondary Deoxidation Particles

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