TY - JOUR
T1 - Effects of Start and Finish Cooling Temperatures on the Yield Strength and Uniform Elongation of Strain-Based API X100 Pipeline Steels
AU - Lee, Dong Ho
AU - Sohn, Seok Su
AU - Song, Hyejin
AU - Ro, Yunjo
AU - Lee, Chang Sun
AU - Lee, Sunghak
AU - Hwang, Byoungchul
N1 - Funding Information:
This work was supported by the Technology Innovation Program (Grant Nos. 100400-25 and 10044574) funded by the Ministry of Trade, Industry, and Energy (MOTIE), Korea.
Publisher Copyright:
© 2018, The Minerals, Metals & Materials Society and ASM International.
PY - 2018/10/1
Y1 - 2018/10/1
N2 - Three types of strain-based API X100 pipeline steels composed of polygonal ferrite (PF), acicular ferrite (AF), granular bainite (GB), bainitic ferrite (BF), and martensite–austenite (MA) were fabricated by varying the start cooling temperature (SCT) and finish cooling temperature (FCT). The effect of the microstructure on the yield strength and uniform elongation before and after strain aging was investigated. In the H-H steel fabricated at a high SCT and low FCT, the reduction in uniform elongation after prestraining was small, but the uniform elongation after heat treatment increased because of the presence of many mobile dislocations around AF and GB, which are present in a relatively high fraction. Because the H-L steel fabricated at high SCT and low FCT has a considerable amount of BF as a result of the significant degree of supercooling, carbon atoms were readily trapped at dislocations inside the BF during heat treatment, which reduced the resistance to strain aging. On the other hand, the L-L steel had a large amount of soft PF transformed in the two-phase (austenite + ferrite) region and high fractions of AF and MA because it was fabricated at low SCT and low FCT. As a result, the uniform elongation of the L-L steel was slightly increased after heat treatment because mobile dislocations were readily generated around the PF and MA boundaries under deformation.
AB - Three types of strain-based API X100 pipeline steels composed of polygonal ferrite (PF), acicular ferrite (AF), granular bainite (GB), bainitic ferrite (BF), and martensite–austenite (MA) were fabricated by varying the start cooling temperature (SCT) and finish cooling temperature (FCT). The effect of the microstructure on the yield strength and uniform elongation before and after strain aging was investigated. In the H-H steel fabricated at a high SCT and low FCT, the reduction in uniform elongation after prestraining was small, but the uniform elongation after heat treatment increased because of the presence of many mobile dislocations around AF and GB, which are present in a relatively high fraction. Because the H-L steel fabricated at high SCT and low FCT has a considerable amount of BF as a result of the significant degree of supercooling, carbon atoms were readily trapped at dislocations inside the BF during heat treatment, which reduced the resistance to strain aging. On the other hand, the L-L steel had a large amount of soft PF transformed in the two-phase (austenite + ferrite) region and high fractions of AF and MA because it was fabricated at low SCT and low FCT. As a result, the uniform elongation of the L-L steel was slightly increased after heat treatment because mobile dislocations were readily generated around the PF and MA boundaries under deformation.
UR - http://www.scopus.com/inward/record.url?scp=85049114377&partnerID=8YFLogxK
U2 - 10.1007/s11661-018-4738-5
DO - 10.1007/s11661-018-4738-5
M3 - Article
AN - SCOPUS:85049114377
SN - 1073-5623
VL - 49
SP - 4536
EP - 4543
JO - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
JF - Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
IS - 10
ER -