Preferable Resistance against Hydrogen Embrittlement of Pearlitic Steel Deformed by Caliber Rolling

摘要

High strengthened steel bar with elongated pearlite was prepared by caliber rolling at room temperature and its hydrogen embrittlement was studied. A 0.6%C - 2%Si - 0.2%Mn - 1%Cr (in mass%) steel was caliber rolled to a reduction of area of 88%, resulting in the evolution of the elongated lamellar structure similar to those in cold drawn pearlitic steel. Mean lamellar spacing of the elongated pearlite was 70 nm and the texture of the rolled steel consisted of strong fiber texture with the rolling direction parallel to . The rolled steel exhibited high yield strength of 1.4 GPa with large reduction of area at fracture (51 %). It was demonstrated by both conventional and slow strain tensile tests (CSRT and SSRT) with circumferentially-notched bar specimens that the rolled steel with elongated pearlite performed higher resistance to hydrogen embrittlement than other thermo-mechanically treated steels in which fundamental microstructure is martensite. The possible mechanism for this desirable property is discussed with linking between the cracking path and the significant characters of the microstructure such as anisotropic morphology of lamellar structure and crystallographic texture.