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Vol.36, No.6, 853 ~ 864, 1998
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| Title |
| Cracking Phenomena during Cold Forging of Low-Carbon Steels |
| 김동국 Dong Kuk Kim , 강석영 Suk Young Kang , 이성학 Sung Hak Lee , 이경종 Kyung Jong Lee , 김정환 Jung Whan Kim |
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| Abstract |
| An investigation was conducted on the effects of microstructural parameters and dynamic deformation behavior on the cracking behavior occurring during cold forging of low-carbon steels. Detailed microstructural analyses of the cracked region showed that a number of adiabatic shear bands, along which cracks were propagated, were formed in the top interior part of the cold-forged pulley. Dynamic torsional tests were conducted using torsional Kolsky bar in order to investigate the dynamic deformation behavior during cold forging, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode, From the dynamic shear stress-strain curves, the steel containing considerable amount of nitrogen showed a smaller shear strain of 0.2 at maximum shear stress point, after which shear stress decreased rapidly just before fracture, whereas the other steel containing smaller amount of nitrogen showed relatively homogeneous shear deformation. This dynamic torsional behavior correlated well with the cracking and adiabatic shear banding behavior, together with yield point phenomenon occurring in the steel containing more nitrogen. Since the cracking occurring during cold forging was associated with the adiabatic shear banding and yield point phenomenon, the minimization of nitrogen and fast cooling rate during hot rolling would be suggested to prevent the cracking. |
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| Key Words |
| Low-carbon steel, Cold forging, Adiabatic shear band, Dynamaic torsional test, Yield point phenomenon |
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