Strain gradient induced grain refinement far below the size limit in a low carbon hypoeutectoid steel (0.19 wt% C) via pipe inner surface grinding treatment

2021 ◽  
Vol 78 ◽  
pp. 155-169
Author(s):  
Wenqiang Li ◽  
Yiming Zhao ◽  
Ning Liu ◽  
Changji Li ◽  
Ruiming Ren ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Strain Gradient ◽  
Surface Grinding ◽  
Low Carbon ◽  
Size Limit ◽  
Inner Surface ◽  
Hypoeutectoid Steel

Role of Strain Gradient and Dynamic Transformation on the Formation of Nanocrystalline Structure Produced by Severe Plastic Deformation

2007 ◽  
Vol 539-543 ◽  
pp. 2787-2792 ◽  
Author(s):  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Jin Guo Li ◽  
Koichi Tsuchiya
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Strain Gradient ◽  
High Pressure Torsion ◽  
Large Strain ◽  
Nanocrystalline Structure ◽  
Angular Pressing ◽  
Dynamic Transformation ◽  
Fine Grained Structure

Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain size larger than 100 nm) had been obtained in many processes such as heavy cold rolling, equal channel angular pressing (ECAP) or accumulative roll bonding (ARB), the formation of nano grained structure (< 100 nm) is limited to processes such as ball milling, shot peening or drilling. In the present study, high pressure torsion (HPT) deformation and drilling were carried out to understand the conditions necessary to obtain nano grained structure in steels. The results of HPT experiments in pure Fe showed that HPT has superior ability of strengthening and grain refinement probably due to a strain gradient but the saturation of grain refinement occurs before reaching nano grained structure. Drilling experiments in high carbon martensitic steel revelaed that nano grained ferrite forms at the drilled hole surface only when the transformation from ferrite to austenite takes place during drilling. Considering various other processes by which nano grained ferrite was produced, it is proposed that heavy strains with large strain gradients together with dynamic transformation are necessary to reach nano grained ferrite structure.

The Influence of Residual Stress on Fatigue Cracking

1990 ◽  
Vol 112 (3) ◽  
pp. 199-203 ◽  
Author(s):  
A. Okamoto ◽  
H. Nakamura
Keyword(s):  
Residual Stress ◽  
Crack Growth ◽  
Surface Crack ◽  
Low Carbon Steel ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Power Relationship ◽  
Low Carbon ◽  
Nonlinear Stress ◽  
Inner Surface

The influence of residual stress on fatigue crack growth was experimentally and analytically investigated for surface cracks. Fatigue tests were performed on straight pipes of low-carbon steel with a circumferential inner surface crack in laboratory air environment. Some of the test pipes had been subjected to special heat treatments so as to have compressive or tensile residual stresses along inner surface. The results show that the compressive residual stress remarkably suppresses the surface crack growth, while the tensile residual stress does not accelerate the crack growth very much. The crack growth analyses were conducted by the application of power relationship between ΔK and da/dN. The stress intensity factors due to the nonlinear stress field were calculated by the weight function method. The analyses resulted in a confirmation of the behavior of the crack growth observed in the experiments.

Experimental Research on the Drag Reduction Technology of Nature Gas Pipeline Transportation

2011 ◽  
Vol 361-363 ◽  
pp. 982-989 ◽  
Author(s):  
Zhi Qiang Huang ◽  
Rong Gai Zhu ◽  
Zhen Chen ◽  
Xue Yuan Li ◽  
Shuang Jing ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Natural Gas ◽  
Drag Reduction ◽  
Flow Pattern ◽  
Flow Resistance ◽  
Gas Pipeline ◽  
Wall Region ◽  
Low Carbon ◽  
Pipeline Transportation ◽  
Inner Surface

As an efficient and environment-friendly energy, natural gas has become an inevitable choice for improving environment, achieving the low carbon economy and the sustainable development all around world. However, flow resistance produced in the course of the gas pipeline transportation caused large loss of transportation energy and brought down the transportation capacity. Therefore, this paper have developed a deep researches on the interaction mechanism between a drag reduction agent (DRA) and the inner surface of natural gas pipeline, the flow pattern improvement regularity about DRA membrane acting on the near-wall region of the pipeline, the relation between the flow pattern improvement and friction resistance, the effect regularity of DRA on the friction coefficient of the pipeline inner surface, and the relation between the alternation of the friction coefficient and the drag reduction. According to all above studies, the fundamental reason for flow resistance of the gas transportation has been found, and the drag reduction mechanism of the gas pipeline transportation has also been hold of. Field test shows that the application of the DRA in the course of the gas pipeline transportation reduced the friction loss by 12%-16.5%, and raised the transfer efficiency by 8%-12%.

Grain Refinement by Rapid Transformation Annealing of Cold Rolled Low Carbon Steels

2005 ◽  
Vol 500-501 ◽  
pp. 771-778 ◽  
Author(s):  
P. Álvarez ◽  
C. Lesch ◽  
Wolfgang Bleck ◽  
Hélène Petitgand ◽  
Joachim Schöttler ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Rapid Heating ◽  
Carbon Steels ◽  
Low Carbon ◽  
Steel Sheets ◽  
Hsla Steels ◽  
Mn Content ◽  
Cold Rolled ◽  
Equiaxed Grains ◽  
Rapid Transformation

A novel thermal treatment, rapid transformation annealing (RTA), has been applied to six different cold rolled low-carbon (LC) steel sheets with the aim of refining their microstructure. The process involves rapid heating to just above the austenite (g) to ferrite (a) transformation temperature and subsequent rapid cooling to room temperature. Grain sizes around 2 µm in two different Nb-Ti HSLA steels, 5 µm in a Ti-LC steel and 6 µm in a plain LC (0.037%C) steel have been produced using fast cooling rates (200°C/s). Non-equiaxed structures are obtained in a Nb-Ti HSIF steel and in a plain LC (0.135%C) (CM) steel due to their higher Mn content. However, very fine equiaxed grains (2 µm) are obtained by rapid intercritical annealing (RIA) in the CM steel. Irrespective of the microalloying concept, the grain growth of recrystallized a grains before their transformation was inhibited in CM and in both HSLA steels. This inhibition is connected with the overlapping of a recrystallization and a-g transformation processes which is essential in order to achieve extreme grain refinement either by RTA or RIA.

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