Development of Anti-Coarsening Steel for Carburizing

There is a glaring need for omitting intermediate heat treatments in the manufacturing processes of carburized parts and increasing the carburizing temperature aimed at cost reduction. It is necessary to develop techniques to inhibit grain-coarsening since some austenite grains tend to grow abnormally during carburizing and coarse grains have negative effects on the properties of parts. Therefore, we developed new techniques to inhibit grain-coarsening by refining precipitates’ size and increasing their volume fraction based on the abnormal grain growth theory by Gladman. In this study, AlN and Nb(CN) were chosen as the precipitate particles for the pinning of austenite grain growth. And we investigated grain-coarsening behavior in several manufacturing processes of parts. As a result, we developed anti-coarsening steels for various manufacturing processes of carburized parts.

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Investigation of the Austenite Grain Growth in HY-TUF Steel

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.299.482 ◽

2020 ◽

Vol 299 ◽

pp. 482-486

Author(s):

Mikhail V. Maisuradze ◽

Maksim A. Ryzhkov

Keyword(s):

Grain Size ◽

Grain Growth ◽

Heating Temperature ◽

High Strength ◽

Silicon Steel ◽

Austenite Grain Size ◽

Austenite Grain ◽

Austenite Grains ◽

Austenite Grain Growth ◽

Intensive Growth

The high strength silicon steel HY-TUF, applied for manufacturing of the heavy loaded aerospace and engineering parts, was investigated. The effect of the heating temperature in the range 900...1000 °C on the austenite grain size was studied. The steel under consideration had a significant scatter of the austenite grain size. The most intensive growth of the austenite grains was observed in the temperature range 975...1000 °C.

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Effect of Niobium Additions on Austenite Grain Coarsening Behavior of GCr15 Bearing Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.817.121 ◽

2015 ◽

Vol 817 ◽

pp. 121-126 ◽

Cited By ~ 1

Author(s):

Xiang Liu ◽

Fan Zhao ◽

Zheng Qiang Dong ◽

Chao Lei Zhang ◽

Yu Shan Kou ◽

...

Keyword(s):

Grain Growth ◽

Bearing Steel ◽

Grain Coarsening ◽

Soaking Time ◽

Experimental Steel ◽

Austenite Grain ◽

Gcr15 Bearing Steel ◽

Coarsening Behavior ◽

Growth Equations ◽

Soaking Temperature

The effect of 0.018% niobium additions on austenite grain coarsening behavior of GCr15 bearing steel was studied. Results indicate that the coarsening temperatures of No.1 and the No.2 experimental steel were 950°C and 1100°C. The austenite grain coarsening temperature was increased by 150°C by the addition of 0.018% Nb in bearing steel. The grain growth equations of two experimental steels at different soaking temperatures from 850°C to 1250°C with the soaking time of 30 min are as follows: the equation of No.1 steel is D1=1.85×105·exp (-6.57×104/RT); the equations of No.2 steel below and above 1100°C is D2=5.08×102·exp (-2.49×104/RT) and D2=1.06×108·exp (-1.31×105/RT), respectively. The grain growth equations of two experimental steels at different soaking time from 15 to 120 min with the soaking temperature of 840°C are as follows: the equation of No.1 steel is D1=4.83×10-2·t0.72 while that of No.2 steel is D2=1.25·t0.18.

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A Study of Abnormal Behavior of Grain Growth in High-Strength Boron-Added Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.767 ◽

2007 ◽

Vol 558-559 ◽

pp. 767-770

Author(s):

You Hwan Lee ◽

Sang Yoon Lee ◽

Duk Lak Lee

Keyword(s):

Grain Growth ◽

High Strength ◽

Production Costs ◽

Abnormal Behavior ◽

Manufacturing Processes ◽

Optimum Amount ◽

Grain Coarsening ◽

Production Processes ◽

Austenite Grain ◽

Tensile Fatigue

In order to save natural resources and to reduce production costs, many industries have conducted studies on new developed steels and manufacturing processes. For instance, the use of high-strength bolts can decrease the number, size and weight of bolts used in a car, thereby decreasing fuel consumption. For this reason, steel makers are developing boron-added steel for high-strength bolts, which eliminates production processes. However, it has been pointed out that this boron-added steel is sensitive to austenite grain coarsening. The austenite grain coarsening does not occur uniformly, hence it can affect mechanical properties such as tensile, fatigue and so on. Therefore, the aim of this study is to investigate the abnormal behavior of grain growth and to determine the optimum amount of alloying elements in boron-added steel for use in making high-strength bolts.

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The Effect of B and Microalloying Elements (V, Ti, Nb) Additions on the Austenite Grain Growth of Low Alloy Steel

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.197.25 ◽

2013 ◽

Vol 197 ◽

pp. 25-32

Author(s):

Henryk Adrian ◽

Marta Pelczar ◽

Anna Adrian ◽

Joanna Augustyn-Pieniążek

Keyword(s):

Grain Size ◽

Grain Growth ◽

Alloy Steel ◽

Growth Inhibitor ◽

Vanadium Content ◽

Low Alloy Steel ◽

Austenite Grain Size ◽

Austenite Grain ◽

Austenite Grains ◽

Austenite Grain Growth

The effect of B and microalloying additions of V, V+Ti, V+Nb on austenite grain growth of low alloy steel containing 0.3% C, 1 % Cr and 0.2 % Mo was investigated. As a measure of austenite grain size the mean chord length of austenite grains was assumed. The boron content in investigated steel was in the range of 0 to 0.008 %. The investigations were carried out in austenitising temperature range of 850 to 1100oC. Using the thermodynamic model the contents of undissolved compounds of carbonitride V(C,N) and boron nitride BN were calculated and the effect of undissolved compounds content on austenite grain size was investigated. Obtained results showed, that vanadium content below 0.1 % was ineffective as austenite grain growth inhibitor of boron containing steel and austenite grain size of steel was higher compare to non-alloyed steel. The most effective for decreasing of austenite grains size of boron containing steel was addition of 0.18 % V + 0.03 % Nb

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Grain Refinement in Titanium-Erbium Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052626 ◽

1974 ◽

Vol 32 ◽

pp. 522-523

Author(s):

B. B. Rath ◽

J. E. O'Neal ◽

R. J. Lederich

Keyword(s):

Electron Microscopy ◽

Size Distribution ◽

Grain Refinement ◽

Grain Growth ◽

Volume Fraction ◽

Pure Titanium ◽

Systematic Investigation ◽

Second Phase ◽

Titanium Matrix ◽

Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104819 ◽

1988 ◽

Vol 46 ◽

pp. 550-551

Author(s):

R. E. Franck ◽

J. A. Hawk ◽

G. J. Shiflet

Keyword(s):

High Temperature ◽

Elevated Temperature ◽

Grain Growth ◽

Volume Fraction ◽

Microstructural Characterization ◽

Second Phase ◽

Microstructural Stability ◽

Elevated Temperature Strength ◽

Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

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Precipitation Criterion for Inhibiting Austenite Grain Coarsening during Carburization of Al-Containing 20Cr Gear Steels

Metals ◽

10.3390/met11030504 ◽

2021 ◽

Vol 11 (3) ◽

pp. 504

Author(s):

Huasong Liu ◽

Yannan Dong ◽

Hongguang Zheng ◽

Xiangchun Liu ◽

Peng Lan ◽

...

Keyword(s):

Grain Growth ◽

Abnormal Grain Growth ◽

Grain Structure ◽

Pinning Force ◽

Grain Coarsening ◽

Zener Pinning ◽

Austenite Grain ◽

Composition Optimization ◽

Gear Steels ◽

Grain Growth Behavior

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this work, the quantitative influence of the Al and N content on the grain size after carburization is studied through pseudocarburizing experiments based on 20Cr steel. According to the grain structure feature and the kinetic theory, the abnormal grain growth is demonstrated as the mode of austenite grain coarsening in carburization. The AlN precipitate, which provides the dominant pinning force, is ripened in this process and the particle size can be estimated by the Lifshitz−Slyosov−Wagner theory. Both the mass fraction and the pinning strength of AlN precipitate show significant influence on the grain growth behavior with the critical values indicating the grain coarsening. These criteria correspond to the conditions of abnormal grain growth when bearing the Zener pinning, which has been analyzed by the multiple phase-field simulation. Accordingly, the models to predict the austenite grain coarsening in carburization were constructed. The prediction is validated by the additional experiments, resulting in accuracies of 92% and 75% for the two models, respectively. Finally, one of the models is applied to optimize the Al and N contents of commercial steel.

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