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

2015 ◽  
Vol 817 ◽  
pp. 121-126 ◽  
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.

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

Metals ◽  
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.

Effect of Rare Earth (RE) La on Solid Solution of Second Phase Particle and Austenite Grain Growth in Steel Containing High Niobium

2011 ◽  
Vol 189-193 ◽  
pp. 2869-2874 ◽  
Author(s):  
Wen Zhong Song ◽  
Qi Fang ◽  
Hui Ping Ren ◽  
Zi Li Jin ◽  
Hui Chang
Keyword(s):  
Solid Solution ◽  
Growth Rate ◽  
Rare Earth ◽  
Grain Growth ◽  
Phase Particle ◽  
Solution Temperature ◽  
Second Phase ◽  
Austenite Grain ◽  
Austenite Grain Growth ◽  
Soaking Temperature

The solid solution of the second phase particle and austenite grain growth behavior of the high niobium-containing RE steel was studied by mathematical calculation and extraction replica technique. The purpose of the study was to investigate the effects of Rare Earth La on austenite grain growth and propose an empirical equation for predicting the austenite grain size of RE steel. Austenite grain grows in an exponential law with the increase of heating temperature, while approximately in a parabolic law with the increase of holding time. Results show that the RE steel has good anti-coarsening ability at elevated temperatures. When soaking temperature is lower than 1250°C , AGS and growth rate are small for high niobium steel, but soaking temperature is lower than 1220°C , AGS and growth rate are small for RE steel. RE La can promote solid solution of second-phase particles Nb(C, N), the solution temperature decrease 30°C than high niobium steel.

Development of Anti-Coarsening Steel for Carburizing

2007 ◽  
Vol 539-543 ◽  
pp. 4855-4860 ◽  
Author(s):  
M. Kubota ◽  
T. Ochi
Keyword(s):  
Grain Growth ◽  
Volume Fraction ◽  
Manufacturing Processes ◽  
Negative Effects ◽  
New Techniques ◽  
Grain Coarsening ◽  
Coarsening Behavior ◽  
Coarse Grains ◽  
Austenite Grains ◽  
Austenite Grain Growth

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.

Effects of Chromium and Nickel Additions on the Austenite Grain Coarsening of Low Carbon Structural Steels Containing 0.13% C

2016 ◽  
Vol 860 ◽  
pp. 152-157 ◽  
Author(s):  
Mohiuddin Ahmed ◽  
Md Mohar Ali Bepari ◽  
Roisul Hasan Galib
Keyword(s):  
Grain Size ◽  
Chromium Carbide ◽  
Structural Steels ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Grain Coarsening ◽  
Austenite Grain ◽  
Nickel Particles ◽  
Coarsening Behavior ◽  
Increasing Temperature

The austenite grain coarsening behavior of low carbon (0.13% C) structural steels containing chromium and nickel singly or in combination were studied by heating the steels at successive high temperature in the austenite zone in the temperature range of 900-1100°C with an interval of 50°C. The carburizing technique has been adopted to reveal the prior austenite grain boundaries and mean linear intercept method was used to measure the austenite grain size.It was found that on heating the undissolved particles of chromium carbide, Cr2C refine the austenite grain size at temperature below 1000°C, but the effect decreases with increasing temperature. Nickel does not produce any austenite grain refinement. In the presence of nickel particles of chromium carbide are less effective than chromium carbide particles in the absence of nickel in the refinement of austenite grain size.

Kinetics of austenite grain growth in medium-carbon niobium-bearing steel

2011 ◽  
Vol 12 (3) ◽  
pp. 171-176 ◽  
Author(s):  
Ying-li Zhao ◽  
Jie Shi ◽  
Wen-quan Cao ◽  
Mao-qiu Wang ◽  
Gang Xie
Keyword(s):  
Grain Growth ◽  
Bearing Steel ◽  
Medium Carbon ◽  
Austenite Grain ◽  
Austenite Grain Growth ◽  
Kinetics Of

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

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.

Austenite Grain Stability of Titanium-Modified Carburizing Steel

2006 ◽  
Vol 118 ◽  
pp. 3-8 ◽  
Author(s):  
Takashi Tanaka ◽  
Takeshi Fujimatsu ◽  
Kazuya Hashimoto ◽  
Kazuhiko Hiraoka
Keyword(s):  
Grain Growth ◽  
Hot Forging ◽  
High Strength ◽  
Cold Forging ◽  
Austenite Grain Size ◽  
Grain Coarsening ◽  
Growth Property ◽  
Austenite Grain ◽  
Automobile Components ◽  
The Cost

It is important to suppress grain coarsening during the carburizing treatment of automobile components such as gears and shafts so that high strength is maintained and heat treatment distortion is minimized. Two manufacturing methods are often used for the cost reduction. One is the increasing carburizing temperature. The other is the adoption of cold forging instead of hot forging. These methods are likely to result in grain coarsening in the case of conventional steels. It is well known that the key factors to control the grain growth are the initial austenite grain size and the volume and mean size of precipitates. In this study, the grain growth property of Ti-modified steel was investigated to confirm the influence of precipitates, and compared with those of Nb-modified and conventional steels. The influence of forging temperature on the grain growth property in a Ti-modified steel was also investigated.

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