scholarly journals Relationship between the Effective Grain Size of Brittle Crack Propagation and Microstructural Size in Low-carbon Low-alloy Bainitic Steels

2016 ◽  
Vol 102 (6) ◽  
pp. 286-294 ◽  
Author(s):  
Shigekazu Morito ◽  
Taisuke Hayashi ◽  
Anh Hoang PHAM ◽  
Tomoya Kawabata
Keyword(s):  
Grain Size ◽  
Crack Propagation ◽  
Low Carbon ◽  
Brittle Crack ◽  
Bainitic Steels ◽  
Effective Grain Size

A Study on the Microstructure of Ultra Low Carbon Bainitic Steels by RPC Technique

2007 ◽  
Vol 561-565 ◽  
pp. 2107-2110 ◽  
Author(s):  
Zhi Fen Wang ◽  
Shao Kang Pu ◽  
Y. Guan ◽  
Ping He Li ◽  
Li Xin Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Bainitic Ferrite ◽  
Granular Bainite ◽  
Low Carbon ◽  
Electron Backscattered Diffraction ◽  
Bainitic Steels ◽  
Transmission Electron ◽  
Effective Grain Size ◽  
Ebsd Technique ◽  
Rolled Condition

The effect of tempering process on the microstructure of ultra low carbon bainitic (ULCB) steel produced by relaxation precipitation controlled phase transformation (RPC) has been investigated by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). The results showed that the final microstructure mainly contained lath-like bainitic ferrite, granular bainite and martensite-austenite (MA) constituent in ULCB steels. On tempering at 650°C a slight increase was detected in the effective grain size as the strain-induced precipitates pinned up the dislocation walls and subgrains. After tempering at 700°C, bainitic ferrite laths started to coarsen and polygonal ferrite occurred. The effective grain size of ULCB steels in as-rolled condition was 1.5 μm at the tolerance of 10o~15o measured by EBSD technique.

Fracture and Crack Propagation Behavior of 560 MPa Microalloyed Pipeline Steel under Different Cooling Schedules

2017 ◽  
Vol 898 ◽  
pp. 1094-1102 ◽  
Author(s):  
Jin Hua Zhao ◽  
Dong Fang Li ◽  
Guo Yuan ◽  
Xue Qiang Wang ◽  
Rui Hao Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Low Temperature ◽  
Crack Propagation ◽  
Pipeline Steel ◽  
Crack Arrest ◽  
Dominant Factor ◽  
Cooling Schedules ◽  
Effective Grain Size ◽  
Mixed Microstructure ◽  
Low Temperature Toughness

Three kinds of pipeline steel with different microstructures were fabricated by varying cooling schedules during thermo-mechanical controlled processing (TMCP). Charpy impact property of the pipeline steels were obtained, and the fracture and crack-arrest mechanisms were further studied. The results indicated that the steels were classified into two kinds according to their microstructures, the mixture of acicular ferrite (AF), quasi-polygonal ferrite (QF), granular bainite (GB) and small fraction of degenerate pearlite (DP), and the mixed microstructure of AF and GB, respectively. The processed steel with microstructure of AF and GB exhibited more excellent low-temperature toughness and crack-arrest properties with upper shelf energy of ~281 J and energy transition temperature of ~-76°C. The mixed microstructure (AF + GB) possessing smaller effective grain size hindered the propagating of crack and consumed large amount of energy during fracture. The effective grain size of microstructure was the dominant factor controlling low-temperature toughness and crack-arrest properties of pipeline steel, which increased the high-angle boundary length per unit area and further increased the crack propagation energy during fracture.

EBSD Study of the Effect of Hot Deformation on Low Carbon Bainitic Structure

2020 ◽  
Vol 993 ◽  
pp. 513-519
Author(s):  
Xin Li Wen
Keyword(s):  
Grain Size ◽  
Thickness Reduction ◽  
Granular Bainite ◽  
Low Carbon ◽  
Remarkable Effect ◽  
Lath Bainite ◽  
Effective Grain Size ◽  
Bainitic Structure ◽  
Ebsd Technique ◽  
The Given

The effect of deformation temperature (DT) and thickness reduction on the bainitic structure was investigated under various test conditions by using hot compression on a Gleeble-1500 thermo-mechanical simulation machine, and electron back scattering diffraction (EBSD) technique. In the case of the bainitic structure consisting of granular bainite (GB), lath bainite (LB) and a little ferrite (AF) under the given deformation conditions, DT and thickness reduction have remarkable effect on the transformation kinetics, starting temperature (B) of bainite fast transformation, and the type of bainitic structure. With the decreasing of DT from 810 °C to 730 °C, the starting temperature of transformation B increase from 585 °C to 595 °C. When the thickness reduction was 0 % and 20 %, the microstructure consists of GB, LB and a little AF, whereas as the thickness reduction increase to 40 %, large grain size of LB and GB disappear, and only AF and M/A remained. With the thickness reduction increases from 0 % to 40 %, the effective grain size decreases from 4 μm to 2 μm, and the fraction of HGB increases from 48 % to 57 %.

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.

Characterisation and Quantification of Complex Bainitic Microstructures in High and Ultra-High Strength Linepipe Steels

2005 ◽  
Vol 500-501 ◽  
pp. 387-394 ◽  
Author(s):  
Stanislaw Zajac ◽  
Volker Schwinn ◽  
K.H. Tacke
Keyword(s):  
Grain Size ◽  
Classification Scheme ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Low Carbon ◽  
New Classification ◽  
Effective Grain Size ◽  
Second Phases ◽  
Definition Of ◽  
Linepipe Steels

This paper provides a detailed description of complex bainitic microstructures obtained during the recent development of low carbon linepipe steels with strengths in the range of X100 to X120. New experimental techniques based on a high resolution FEG-SEM and EBSD have been used to characterise and quantify the mixture of ultrafine bainitic ferrite and nanosize second phases in these steels. It was found that the occurrence of incomplete transformation generates new, previously unexplored bainitic microstructures with a wealth of microstructural features that is beyond classification based on conventional concepts. Clear differences in distributions of boundary misorientations and effective grain size were noted between upper, lower and granular bainites. Based on these results a new classification scheme and definition of bainite is proposed.

Study on Mechanical Properties Anisotropy of X80 Pipeline Steel

2013 ◽  
Vol 803 ◽  
pp. 413-418
Author(s):  
Qiang Duan ◽  
Jun Yan ◽  
Guo Hui Zhu ◽  
Qing Wu Cai
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Impact Toughness ◽  
Crack Propagation ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Rolling Direction ◽  
High Angle ◽  
X80 Pipeline Steel ◽  
Effective Grain Size

The microstructure of X80 pipeline steel in different directions were observed by SEM technique and its effective grain size and misorientation were statistically analyzed by EBSD system. Based on these results, the mechanical properties at 0°, 45° and 90° to the rolling direction of X80 pipeline steel were studied. The results show that, owing to finer grain size and less low-angle grain boundaries, strengths and impact toughness of X80 pipeline steel at 90° direction are optimal. While the pipeline steel possesses finer grain size, more high-angle grain boundaries and less low-angle grain boundaries, the crack propagation is effectively suppressed, then its impact toughness is improved.

Sign in / Sign up

Export Citation Format

Share Document