Super Short Interval Multi-pass Rolling Process for Ultrafine-grained Hot Strip

The yielding behavior of interstitial-free steels and low-carbon steels with varying amounts of C and N were investigated in connection with the HallPetch relation. The HallPetch coefficient is as small as 150 MPa·µm 1/2 in interstitial-free steels but it increases to 600 MPa·µm 1/2 by adding solute carbon up to 60 ppm. Nitrogen does not have a significant effect on the HallPetch coefficient. The results of three-dimensional (3D) atom probe analysis indicated that carbon has 34 times greater segregation potential in comparison with nitrogen. The small effect of nitrogen on the HallPetch coefficient in steel is probably due to the small segregation potential of nitrogen. It was also confirmed that discontinuous yielding occurs when the difference between the yield stress and friction stress is increased by grain-refinement strengthening and that yielding occurs by dislocation emission from grain boundaries where primary dislocations have piled up. Carbon atoms segregated at grain boundaries seem to play a role in stabilizing dislocation emission sites at the grain boundaries, which enhances the HallPetch coefficient of iron. These results support the dislocation pile-up model of explaining yielding in polycrystalline metals.

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“…14,15) As a result, it can be concluded that the HP coefficient is approximately 600 MPa·µm 1/2 in steels with more than 0.005% carbon. In Fig.…”

Section: Hallpetch Relation and Yielding Behavior In Steels Containinmentioning

confidence: 93%

Effect of Grain Boundary Segregation of Interstitial Elements on Hall–Petch Coefficient in Steels

et al. 2014

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“…In this project, a variety of manufacturing processes such as hot rolling with large accumulated strain, 14) hot forging 15) and multi-bending after hot rolling 16) were proposed. For manufacture of fine grained steel, the authors proposed a multi-bending process after hot rolling.…”

Section: Introductionmentioning

confidence: 99%

Thermal Analysis of Strip in Multi-bending Process After Hot Rolling

Nakata¹,

Matsubara²,

Hiruta³

2013

ISIJ Int.

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The thermal histories of steel strips in a multi-bending process after hot rolling were clarified by numerical analysis in order to investigate the appropriate conditions for grain refinement. The temperature oscillates cyclically at the strip surface, whereas the temperature amplitude is relatively small at the center of thickness. The temperature distribution in the strip thickness direction depends on the transfer speed and cooling conditions, that is, air or water cooling. In industrial production, water-cooling equipment would be necessary in order to cancel the accumulated heat generation caused by bending deformation and to maintain the strip temperature in the appropriate range for grain refinement.

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“…A marked number of investigations on the formation of a bulk nanostructured metal by using a severe plastic deformation (SPD) process have been performed, 15) and most of them use nonferrous alloys with diversified chemical compositions and various alloying elements. At the same time, steel still occupies the largest share as a structure metal, and this situation will continue for the time being.…”

Section: Introductionmentioning

confidence: 99%

Interrupt Shearing Test for Evaluating Effect of Large Shear Deformation on Evolution of Microstructure into Ultrafine Grains

Sugiyama

Kawando

et al. 2012

Mater. Trans.

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A new physical simulation method for evaluating the effect of shear deformation on the evolution of a microstructure is proposed. This method utilizes a high-speed compression testing machine and is capable of simulating the formation of fine grained steels in the transformation route. The outline of the proposed method, which is based on shearing and named the 'interrupt shearing test', is presented. The result of the preliminary application of the newly proposed test at an elevated temperature is shown. It becomes clear that the large shear deformation reproduced by the proposed method is capable of producing fine grained steels with a grain size of around 2 µm surrounded by high angle grain boundaries (HAGBs), although controlled cooling immediately after plastic deformation to accelerate transformation into finer grains is not applied in the present test.

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Super Short Interval Multi-pass Rolling Process for Ultrafine-grained Hot Strip

Cited by 63 publications

References 6 publications

Effect of Grain Boundary Segregation of Interstitial Elements on Hall–Petch Coefficient in Steels

Effect of Grain Boundary Segregation of Interstitial Elements on Hall–Petch Coefficient in Steels

Thermal Analysis of Strip in Multi-bending Process After Hot Rolling

Interrupt Shearing Test for Evaluating Effect of Large Shear Deformation on Evolution of Microstructure into Ultrafine Grains

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Super Short Interval Multi-pass Rolling Process for Ultrafine-grained Hot Strip

Cited by 63 publications

References 6 publications

Effect of Grain Boundary Segregation of Interstitial Elements on Hall&ndash;Petch Coefficient in Steels

Effect of Grain Boundary Segregation of Interstitial Elements on Hall&ndash;Petch Coefficient in Steels

Thermal Analysis of Strip in Multi-bending Process After Hot Rolling

Interrupt Shearing Test for Evaluating Effect of Large Shear Deformation on Evolution of Microstructure into Ultrafine Grains

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Product

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Effect of Grain Boundary Segregation of Interstitial Elements on Hall–Petch Coefficient in Steels

Effect of Grain Boundary Segregation of Interstitial Elements on Hall–Petch Coefficient in Steels