Accessible Unlicensed Requires Authentication Published by De Gruyter June 11, 2013

Tensile and fatigue properties of sub-microcrystalline ultra-low carbon steel produced by hpt-straining

Yoshikazu Todaka, Hironori Nagai, Yosuke Takubo, Miki Yoshii, Masaaki Kumagai and Minoru Umemoto

Abstract

The tensile and fatigue properties of ultra-low carbon steel after HPT-straining at a rotation-speed of 0.2 rpm under a compression pressure of 5 GPa were investigated. Elongated grains with 300 nm thickness and 600 nm length with high dislocation density were formed by the HPT-straining. The obtained Vickers microhardness was around 3.6 GPa. The engineering tensile strength of the HPT-processed ultra-low carbon steel for 5 and 10 turns was 1.9 GPa, which is similar to the value of maraging high-alloy steels. The elongation increased with strain (at 5 to 10 turns). The increase in elongation is caused by the reduction of the stress concentration due to the existence of continuously recrystallized grains. The fatigue strengths of HPT-processed specimens were twice as high as those of the 90 % cold-rolled specimen in the low-cycle fatigue region, whereas in the high-cycle fatigue region the fatigue strengths were not so different due to the high notch sensitivity of the HPT-processed specimens.


* Correspondence address, Yoshikazu Todaka (Associate Professor) Department of Production Systems Engineering Toyohashi University of Technology Hibarigaoka 1-1, Tempaku, Toyohashi, Aichi, 441-8580, Japan Tel.: +81 532 44 1214 Fax: +81 532 44 6690 E-mail:

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Received: 2008-8-28
Accepted: 2009-4-2
Published Online: 2013-06-11
Published in Print: 2009-06-01

© 2009, Carl Hanser Verlag, München