Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment
The microstructure and hardness along the thickness direction of a water-quenched, high-strength thick plate with a thickness of 40 mm were investigated with three specimens from the thick plate: surface, 1/4t, and 1/2t (center) thickness, and the phase transformation behavior of the thick plate acc...
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| author | Hyo-Haeng Jo Kyeong-Won Kim Hyungkwon Park Joonoh Moon Young-Woo Kim Hyun-Bo Shim Chang-Hoon Lee |
| author_facet | Hyo-Haeng Jo Kyeong-Won Kim Hyungkwon Park Joonoh Moon Young-Woo Kim Hyun-Bo Shim Chang-Hoon Lee |
| author_sort | Hyo-Haeng Jo |
| collection | DOAJ |
| description | The microstructure and hardness along the thickness direction of a water-quenched, high-strength thick plate with a thickness of 40 mm were investigated with three specimens from the thick plate: surface, 1/4t, and 1/2t (center) thickness, and the phase transformation behavior of the thick plate according to the cooling rate was analyzed through dilatometric experiments. Finally, the cooling rate for each thickness of the thick plate was estimated by comparing the microstructure and hardness of the thick plate along with the thickness with those of the dilatometric specimens. Martensite microstructure was observed on the surface of the water-quenched thick plate due to the fast cooling rate. On the other hand, an inhomogeneous microstructure was transformed inside the thick plate due to the relatively slow cooling rate and central segregation of Mn. A small fraction of bainite was shown at 1/4t thickness. A banded microstructure with martensite and bainite resulting from Mn segregation was developed at 1/2t; that is, the full martensite microstructure was transformed in the Mn-enriched area even at a slow cooling rate due to high hardenability, but a bainite microstructure was formed in the Mn-depleted area owing to relatively low hardenability. A portion of martensite with fine cementite at the surface and 1/4t was identified as auto-tempered martensite with a Bagaryatskii orientation relationship between the ferrite matrix and cementite. The microstructure and hardness as well as dilatation were investigated at various cooling rates through a dilatometric experiment, and a continuous cooling transformation (CCT) diagram was finally presented for the thick plate. Comparing the microstructure and hardness at the surface, 1/4t, and 1/2t of the thick plate with those of dilatometric specimens cooled at various cooling rates, it was estimated that the surface of the thick plate was cooled at more than 20 °C/s, whereas the 1/4t region was cooled at approximately 5~10 °C/s during water quenching. Despite the difficulty in estimation of the cooling rate of 1/2t due to the banded structure, the cooling rate of 1/2t was estimated between 3 and 5 °C/s based on the results of an Mn-depleted zone. |
| first_indexed | 2024-03-11T01:35:11Z |
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| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
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| spelling | doaj.art-61da54c1a6fc4a86af4a405a371d767d2023-11-18T16:59:54ZengMDPI AGMaterials1996-19442023-07-011613479210.3390/ma16134792Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric ExperimentHyo-Haeng Jo0Kyeong-Won Kim1Hyungkwon Park2Joonoh Moon3Young-Woo Kim4Hyun-Bo Shim5Chang-Hoon Lee6Korea Institute of Materials Science, Changwon 51508, Republic of KoreaKorea Institute of Materials Science, Changwon 51508, Republic of KoreaKorea Institute of Materials Science, Changwon 51508, Republic of KoreaDepartment of Materials Convergence and System Engineering, Changwon National University, Changwon 51140, Republic of KoreaHyundai Steel Company, Dangjin 31719, Republic of KoreaHyundai Steel Company, Dangjin 31719, Republic of KoreaKorea Institute of Materials Science, Changwon 51508, Republic of KoreaThe microstructure and hardness along the thickness direction of a water-quenched, high-strength thick plate with a thickness of 40 mm were investigated with three specimens from the thick plate: surface, 1/4t, and 1/2t (center) thickness, and the phase transformation behavior of the thick plate according to the cooling rate was analyzed through dilatometric experiments. Finally, the cooling rate for each thickness of the thick plate was estimated by comparing the microstructure and hardness of the thick plate along with the thickness with those of the dilatometric specimens. Martensite microstructure was observed on the surface of the water-quenched thick plate due to the fast cooling rate. On the other hand, an inhomogeneous microstructure was transformed inside the thick plate due to the relatively slow cooling rate and central segregation of Mn. A small fraction of bainite was shown at 1/4t thickness. A banded microstructure with martensite and bainite resulting from Mn segregation was developed at 1/2t; that is, the full martensite microstructure was transformed in the Mn-enriched area even at a slow cooling rate due to high hardenability, but a bainite microstructure was formed in the Mn-depleted area owing to relatively low hardenability. A portion of martensite with fine cementite at the surface and 1/4t was identified as auto-tempered martensite with a Bagaryatskii orientation relationship between the ferrite matrix and cementite. The microstructure and hardness as well as dilatation were investigated at various cooling rates through a dilatometric experiment, and a continuous cooling transformation (CCT) diagram was finally presented for the thick plate. Comparing the microstructure and hardness at the surface, 1/4t, and 1/2t of the thick plate with those of dilatometric specimens cooled at various cooling rates, it was estimated that the surface of the thick plate was cooled at more than 20 °C/s, whereas the 1/4t region was cooled at approximately 5~10 °C/s during water quenching. Despite the difficulty in estimation of the cooling rate of 1/2t due to the banded structure, the cooling rate of 1/2t was estimated between 3 and 5 °C/s based on the results of an Mn-depleted zone.https://www.mdpi.com/1996-1944/16/13/4792thick plate steelwater quenchingcooling ratemicrostructurehardnessdilatometry |
| spellingShingle | Hyo-Haeng Jo Kyeong-Won Kim Hyungkwon Park Joonoh Moon Young-Woo Kim Hyun-Bo Shim Chang-Hoon Lee Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment Materials thick plate steel water quenching cooling rate microstructure hardness dilatometry |
| title | Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment |
| title_full | Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment |
| title_fullStr | Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment |
| title_full_unstemmed | Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment |
| title_short | Estimation of Cooling Rate of High-Strength Thick Plate Steel during Water Quenching Based on a Dilatometric Experiment |
| title_sort | estimation of cooling rate of high strength thick plate steel during water quenching based on a dilatometric experiment |
| topic | thick plate steel water quenching cooling rate microstructure hardness dilatometry |
| url | https://www.mdpi.com/1996-1944/16/13/4792 |
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