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.

Effect of Chromium and Nickel Additions on the Transformation Characteristic and Ferrite Grain Size Refinement of Low Carbon Structural Steels Containing 0.13% C

2016 ◽  
Vol 860 ◽  
pp. 158-164
Author(s):  
Md Mohar Ali Bepari ◽  
Mohiuddin Ahmed
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Optical Microscopy ◽  
Chromium Carbide ◽  
Volume Fraction ◽  
Structural Steels ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Ferrite Grain Size

The effect of small addition of chromium and nickel alone or in combination on the transformation characteristic and ferrite grain size of low carbon (0.13%C) structural steels have been studied by cooling suitable steels at four different cooling rates ranging from 120°C/min to 3.6° C/min from temperatures giving a constant austenite grain size of 37 μm. Radio Frequency generator with control system was used for the heat treatment of the steel samples. Optical microscopy of the heat treated samples was carried out. Ferrite grain size was determined from the fictitious ferrite grain size measured by mean linear intercept method and the volume fraction of pearlite obtained by optical microscopy and point counting. It was found that although the heat treatment of the steels was started from a common austenite grain size, their subsequent ferrite grain size after cooling at the same cooling rate were not the same. Both chromium and nickel enhance the formation of Widmanstatten structure. But chromium is more effective than nickel in the formation of Widmanstatten structure. It was also found that the undissolved particles of chromium carbide (Cr2C) present during austenitizing have no role in determining the ferrite grain size. The precipitating particles of chromium carbide (Cr2C) are excellent ferrite grain size refiners. Nickel refines the ferrite grain size. In presence of nickel, Cr2C precipitates are less effective than Cr2C precipitates in absence of nickel in the refinement of ferrite grain size.

scholarly journals Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 988 ◽  
Author(s):  
Liangyun Lan ◽  
Zhiyuan Chang ◽  
Penghui Fan
Keyword(s):  
Grain Size ◽  
Prior Austenite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Bainite Transformation ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

The simulation welding thermal cycle technique was employed to generate different sizes of prior austenite grains. Dilatometry tests, in situ laser scanning confocal microscopy, and transmission electron microscopy were used to investigate the role of prior austenite grain size on bainite transformation in low carbon steel. The bainite start transformation (Bs) temperature was reduced by fine austenite grains (lowered by about 30 °C under the experimental conditions). Through careful microstructural observation, it can be found that, besides the Hall–Petch strengthening effect, the carbon segregation at the fine austenite grain boundaries is probably another factor that decreases the Bs temperature as a result of the increase in interfacial energy of nucleation. At the early stage of the transformation, the bainite laths nucleate near to the grain boundaries and grow in a “side-by-side” mode in fine austenite grains, whereas in coarse austenite grains, the sympathetic nucleation at the broad side of the pre-existing laths causes the distribution of bainitic ferrite packets to be interlocked.

Evaluation of Austenite Grains Growth in High Nb and Low Nb HSLA Steel

2020 ◽  
Vol 1000 ◽  
pp. 404-411
Author(s):  
Eddy S. Siradj
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Oil And Gas ◽  
Hsla Steel ◽  
Large Diameter ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Reheating Process ◽  
Austenite Grain Growth

This study was presented due to the increasing demand of High Strength Low Alloy (HSLA) steel, such as demand for thinner-walled and large diameter pipes in oil and gas industries. In order to meet the imposed economic restrictions, the high standard of all kinds of steel properties is required and can be achieved by controlling the steel microstructure. The austenite grain size influences the microstructure and properties of steel significantly, in which fine austenite grain size leads to higher strength, better ductility, and higher toughness. Studying the behavior of steel grain growth during the reheating process is still being a fascinating subject. P.R. Rios and D Zollner [1] mentioned that grain growth is the most important unresolved issue that has been a topic of research for many years. In this research, the behavior of austenite grain growth at a high niobium-low carbon (High Nb-low C) and low Nb-high C HSLA steel was evaluated, and the result was compared with other investigation. The results found that the austenite grain growth at high Nb-high C steel was slower than the growth at a low Nb-low C steel. The activation energy of austenite grain growth and both constant A and exponent n ware determined close agreement was obtained between the prediction of the model and the experimental grain size value.

Austenite Grain Structures in Ti and Nb-Containing HSLA Steel during Slab Reheating

2014 ◽  
Vol 783-786 ◽  
pp. 669-673
Author(s):  
Debalay Chakrabarti ◽  
S. Roy ◽  
Dinesh Srivastava ◽  
Gautam Kumar Dey
Keyword(s):  
Grain Size ◽  
Hsla Steel ◽  
Size Variation ◽  
Inhomogeneous Distribution ◽  
Low Carbon ◽  
Cast Slab ◽  
Austenite Grain Size ◽  
Intermediate Temperature Range ◽  
Austenite Grain ◽  
Grain Structures

Spatial distribution of microalloy precipitates have been characterized in a low carbon microalloyed steel containing Nb, Ti and V. Micro-segregation during casting resulted in an inhomogeneous distribution of Nb (and also Ti) precipitates in the as-cast slab. Austenite grain growth has been investigated in the above mentioned steel, using different reheating temperatures between 1000°C and 1250°C for 1 h. Inhomogeneous distribution of Nb-rich precipitates created austenite grain size bimodality after reheating to an intermediate temperature range (1150-1200°C). Uniformly fine and uniformly coarse grain structures were found after reheating at lower- (≤ 1075°C) and higher-reheating temperatures (≥ 1250°C). A model has been proposed for the prediction of austenite grain size variation in the reheated steel.

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