PSI - Issue 33

ScienceDirect Available online at www.sciencedirect.com Science ir t Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 33 (2021) 1162–1172 Structural Integrity Procedia 00 (2019) 000 – 000

www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the IGF ExCo Sn is considered as a tramp element that cannot be removed in steel refining process, and it has been reported that the toughness of the base metal and the welded heat affected zone can be significantly degraded. In the case of electric furnace steels with degraded toughness, segregation of Sn is observed at grain boundaries and the resulting fracture mode shifts to intergranular fracture mode. In this study, in order to quantify the allowable amount of Sn added to thick steel plates that is used for large-heat input welding, experiments were conducted on specimens with different amounts of Sn and heat-treated for different holding times at 400 ℃ , which is a typical embrittlement temperature and investigated the effect of the amount of Sn on the change in low temperature fracture toughness. As a result of fracture toughness tests, clear evidence of temper embrittlement was observed. Apart from previous famous study by McMahon, there was no intergranular fracture in fracture surface but transgranular and cleavage fracture was observed. Therefore, the mechanism by which Sn tends to cause cleavage fracture in the weld heat affected zone was proposed. Based on our newly proposed mechanism, a model was developed to estimate the transition temperature change for various conditions of tempering time, tempering temperature and Sn content. Finally, the authors propose allowable maximum content of Sn based on the model for the establishment of the rational ore sorting system from scraps in near future society. Keywords: embrittlement; tramp element; electric furnace steel S is c ns dered as a tramp element that cannot be rem ved in steel refining proce s, and it has been report d that the tough ess of the base metal an the weld d he t affect d zone can be significantly degraded. In th cas of electric furnace st els with d graded toughness, egreg tion of Sn is observed at grain boundaries and the resulting fracture mode shifts to intergran lar fracture mode. In this study, in or er to quantify th allowable amount of Sn added to thick steel plates that is used for large-heat input welding, exp iments were conducted on specimens with different amou ts of Sn and heat-treated fo different holding times at 400 ℃ , which is a typical embrittlement t mperature d investigated the ffect of the amount of Sn on the chang in low temperature fracture toughness. As a re ult of fracture toughness test , clear vidence o temp r embrittlement was observed. Apart fr m previous famous stu y by McMahon, there as no intergranular fracture in fracture surface but transgranul r and cleavage fracture was observed. Th refore, th mechanis by hich Sn t ds to cause cleavage fracture in the weld heat affected zone w s proposed. Based on our newly propos d mechanism, a model was d veloped to estimate the transitio temperature cha ge for various conditions of tempering time, tempering temperature and Sn content. Finally, the authors propose allowable maximum content of Sn based on the model for th establishment of the ration l ore sorting system from scraps in near futu society. Keywords: embrittlement; tramp element; electric furnace steel IGF26 - 26th International Conference on Fracture and Structural Integrity Deterioration of HAZ toughness by residual Sn and Determination of its Allowable Content for Electric Furnace Steels Saki Hayashi a , Tomoya Kawabata a , Masayuki Yoshimoto b , Masayuki Yamamoto b, * a The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8654, Japan b Chubu Steel Plate Co., Ltd., 5-1 Kosudori, Nagoya Nakagawa-ku, Aichi 454-8506, Japan Abstract One promising direction in steelmaking to respond to global climate change issue is to increase the use of electric furnace manufacturing methods using zero-carbon electricity, which have received more and more attention recently. Considering the replacement from blast furnace steel, the temper embrittlement problem induced by some tramp elements, which is unique behavior for electric furnace methods, must be resolved. IGF26 - 26th International Conference on Fracture and Structural Integrity Deterioration of HAZ toughness by residual Sn and Determination of its Allowable Content for Electric Furnace Steels Saki Hayashi a , Tomoya Kawabata a , Masayuki Yoshimoto b , Masayuki Ya amoto b, * a The University of Tokyo, 7-3-1 Hong Bunkyo-ku, Tokyo 113-8654, Japan b Chubu Steel Plate Co., Ltd., 5-1 Kosudori, Nagoya Nakagawa-ku, Aichi 454-8506, Japan Abstract One promising direction in steelmaking to respond to global climate change issue is to increase the use of electric furnace manufacturing methods using zero-carbon electricity, which have received more and more attention recently. Considering the replacement from blast furnace steel, the temper embrittlement problem induced by some tramp elements, which is unique behavior for electric furnace methods, must be resolved.

* Corresponding author. Tel.: +81-03-5841-6517; fax: +81-03-5841-6517. E-mail address: hayashi@fract.t.u-tokyo.ac.jp

2452-3216 © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the IGF ExCo 10.1016/j.prostr.2021.10.130 2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review Statement: Peer-review under responsibility of the scientific committee of the IGF ExCo 2452-3216 © 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review Statement: Peer-review under responsibility of the scientific committee of the IGF ExCo * Corresponding author. Tel.: +81-03-5841-6517; fax: +81-03-5841-6517. E-mail address: hayashi@fract.t.u-tokyo.ac.jp