Austenite Grain Size Refinement of Multi-Microalloyed Low Carbon Steel Using Severe Plastic Deformation at High Temperature

2016 ◽  
Vol 838-839 ◽  
pp. 440-444
Author(s):  
Xiang Wei Kong ◽  
Tian Zhong Sui ◽  
Zhi Yong Hu
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Hot Deformation ◽  
Low Carbon Steel ◽  
Optical Microscope ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Size Refinement ◽  
Austenite Grain

The effect of hot deformation behavior on austenite grain size refinement of low carbon multi-microalloyed steel was investigated. The morphology of austenite grains was revealed by thermal etching and observed using optical microscope. The results showed that single pass compression can only marginally refine austenite grain size by dynamic recrystallization, even under severe plastic deformation. However, when the specimens were held for a while after hot deformation, the fine austenite grain size can be obtained due to static recrystallization behavior.

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.

The Effects of Hot Deformation Parameters on the Size of Dynamically Recrystallised Austenite Grains of HSLA Steel

2019 ◽  
Author(s):  
Sebastian Gnapowski ◽  
Elżbieta Kalinowska- Ozgowicz ◽  
Mariusz Sniadkowski ◽  
Aleksandra Pietraszek
Keyword(s):  
Grain Size ◽  
Hot Deformation ◽  
Hsla Steel ◽  
Optical Microscope ◽  
Austenite Grain Size ◽  
Deformation Parameters ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Ebsd Technique ◽  
Scanning Electron

This paper presents the results of investigations of the effects of hot deformation parameters in compression investigation on the austenite grain size in HSLA steel (0.16% C, 0.037% Nb, 0.004% Ti, 0.0098% N). The axisymmetric compression investigations were performed on cylindrical investigation specimens of d=1.2 using the Gleeble 3800 simulator. The strain rate=1s-1÷15.9s-1 and strain degree ε=1.2. Before deformation, the research specimens were austenitized at TA = 1100 ÷ 1250 °C. Metallographic observations of the primary austenite grains were conducted with an optical microscope, while the structure of dynamically recrystallized austenite, inherited by martensite, was examined by EBSD technique using a scanning electron microscope. Based on the analysis of investigation results, it was found that the size of dynamically recrystallized austenite grains in HSLA steel were clearly affected by hot compression parameters. In contrast, no significant impact of austenitising temperature on their size was found.

Surface Nanocrystallization of Low Carbon Steel Induced by Circulation Rolling Plastic Deformation

2005 ◽  
Vol 475-479 ◽  
pp. 133-136 ◽  
Author(s):  
Xin Min Fan ◽  
Bosen Zhou ◽  
Lin Zhu ◽  
Heng Zhi Wang ◽  
Jie Wen Huang
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Surface Layer ◽  
Carbon Steel ◽  
Severe Plastic Deformation ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Surface Nanocrystallization ◽  
Average Grain Size ◽  
The Matrix

In this paper, the circulation rolling plastic deformation(CRPD) surface nanocrystallization technology is proposed based on the idea that the severe plastic deformation can induce grain refinement. The equipment of CRPD is designed and manufactured. A nanocrystallization surface layer was successfully obtained in a column sample of low carbon steel. The average grain size in the top surface layer is about 18 nm, and gradually increases with the distance from the surface. The hardness increases gradually from about 200HV0.1 in the matrix to about 600HV0.1 in the surface layer.

Tempering of Direct Quenched Low-Alloy Ultra-High-Strength Steel, Part I – Microstructure

2014 ◽  
Vol 922 ◽  
pp. 316-321 ◽  
Author(s):  
Antti J. Kaijalainen ◽  
Sakari Pallaspuro ◽  
David A. Porter
Keyword(s):  
Grain Size ◽  
Low Carbon Steel ◽  
High Strength ◽  
Steel Part ◽  
Grain Structure ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Direct Quenching ◽  
Austenite Grain ◽  
Effective Grain Size

The direct quenching of low-carbon steel has been shown to be an effective way of producing ultra-high-strength, tough structural steels in the as-quenched state without tempering. However, in the present study, the influence of tempering at 500 °C has been studied in order to evaluate the possibilities of widening the range of strengths that can be produced from a single base composition. The chosen composition was 0.1C-0.2Si-1.1Mn-0.15Mo-0.03Ti-0.002B. In order to compare direct quenching with conventional quenching, two pre-quench austenite states were studied: a thermomechanically rolled, non-recrystallized, pancaked austenite grain structure and a recrystallized, equiaxed grain structure. Quenched and quenched-and-tempered microstructures were studied using FESEM and FESEM-EBSD. The as-quenched microstructures of the reheated and quenched and direct quenched specimens were fully martensitic and martensitic-bainitic, respectively. In both cases, tempering made the needle-shaped auto-tempered carbides of the as-quenched materials more spherical. In the case of the direct quenched (DQ) material, tempering led to a notable increase in the size of the grain boundary carbides. Prior austenite grain size and effective grain size after quenching were larger in the case of reheated and quenched material (RQ). Tempering had no effect on effective grain size. The crystallographic texture of the DQ material showed strong {112}<131> and {554}<225> components. The RQ material also contained the same components, but it also contained an intense {110}<110> and {011}<100> components. The effects of these microstructural changes on tensile, impact toughness and fracture toughness are described in part II.

Influence of Austenite Grain Size on the Crystallography of Allotriomorphic Ferrite in a Low Carbon Steel

2012 ◽  
Vol 535-537 ◽  
pp. 605-610 ◽  
Author(s):  
Yin Bai ◽  
Hui Guo ◽  
Shan Wu Yang ◽  
Xin Lai He
Keyword(s):  
Grain Size ◽  
Prior Austenite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Allotriomorphic Ferrite ◽  
Austenite Grains ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

The influence of prior austenite grain size on the crystallography of allotriomorphic ferrite is investigated in a low carbon steel. The results show that as the prior austenite grain size decreasing, the fraction of allotriomorphic ferrites that do not keep K-S orientation relationship with any surrounding prior austenite grains is increased. It is observed that such ferrites usually form at the grain edges or grain corners. It is known that with the grain size decreasing, the fraction of grain edges and corners increases. It is suggested that the free energy of the defects at such nucleation sites is higher than that at grain faces, and the nucleation barrier of ferrite is lower. As a result, the possibility for the ferrite to form that does not have orientation relationship with all surrounding austenite grains is increased at such sites.

Transverse Surface Cracks in Continuously Cast Steel Slabs, Oscillation Marks and Austenite Grain Size

2010 ◽  
Vol 638-642 ◽  
pp. 3603-3609 ◽  
Author(s):  
Rian Dippenaar
Keyword(s):  
Grain Size ◽  
Low Carbon Steel ◽  
Surface Cracks ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Continuously Cast ◽  
Steel Slabs ◽  
Ferrite Films ◽  
Oscillation Marks

Transverse surface cracks in low carbon steel slabs are invariably inter-granular and follow the soft ferrite films outlining the grain boundaries of exceptionally large prior-austenite grains often found at the roots of oscillation marks in continuously cast low-carbon steel slabs. Plastic deformation is concentrated in the ferrite films and cracks initiate in the ferrite films, leading to crack propagation along the austenite grain boundaries. Hot-ductility is significantly reduced by an increase in austenite grain size and in situ observations revealed that depending on the cooling rate, austenite can nucleate and grow by diffusional mechanisms or forms by a massive type of reaction. The delta-ferrite transformation has also been studied by using neutron diffraction techniques and high-energy X-rays in a synchrotron.

scholarly journals Anisotropic Pinning-Effect of Inclusions in Mg-Based Low-Carbon Steel

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2241
Author(s):  
Chi-Kang Lin ◽  
Hsuan-Hao Lai ◽  
Yen-Hao Su ◽  
Guan-Ru Lin ◽  
Weng-Sing Hwang ◽  
...  
Keyword(s):  
Grain Size ◽  
Carbon Steel ◽  
Grain Boundary ◽  
Low Carbon Steel ◽  
In Situ Observation ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grain Boundary

In this study, the effect of austenite grain size on acicular ferrite (AF) nucleation in low-carbon steel containing 13 ppm Mg is determined. The average austenite grain size was calculated using OM Leica software. Results show that the predicted and experimental values of austenite grain size are extremely close, with a deviation of less than 20 µm. AF formation is difficult to induce by either excessively small and large austenite grain sizes; that is, an optimal austenite grain size is required to promote AF nucleation probability. The austenite grain size of 164 µm revealed the highest capacity to induce AF formation. The effects of the maximum distance of carbon diffusion and austenite grain size on the microstructure of Mg-containing low carbon steel are also discussed. Next, the pinning ability of different inclusion types in low-carbon steel containing 22 Mg is determined. The in situ observation shows that not every inclusion could inhibit austenite grain migration; the inclusion type influences pinning ability. The grain mobility of each inclusion was calculated using in situ micrographs of confocal scanning laser microscopy (CSLM) for micro-analysis. Results show that the austenite grain boundary can strongly be pinned by Mg-based inclusions. MnS inclusions are the least effective in pinning austenite grain boundary migration.

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