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Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel

Heat-affected zones (HAZs) in real welds are usually quite narrow, and consequently most standard mechanical tests are difficult or even impossible. Therefore, simulated microstructures are often used for mechanical tests. However, the most often used weld thermal cycle simulator produces only a few...

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Autores principales: Vuherer, Tomaž, Smaili, Fidan, Bjelajac, Edvard, Manjgo, Mirza, Lojen, Gorazd
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9573272/
https://www.ncbi.nlm.nih.gov/pubmed/36234121
http://dx.doi.org/10.3390/ma15196782
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author Vuherer, Tomaž
Smaili, Fidan
Bjelajac, Edvard
Manjgo, Mirza
Lojen, Gorazd
author_facet Vuherer, Tomaž
Smaili, Fidan
Bjelajac, Edvard
Manjgo, Mirza
Lojen, Gorazd
author_sort Vuherer, Tomaž
collection PubMed
description Heat-affected zones (HAZs) in real welds are usually quite narrow, and consequently most standard mechanical tests are difficult or even impossible. Therefore, simulated microstructures are often used for mechanical tests. However, the most often used weld thermal cycle simulator produces only a few millimeters wide area of simulated microstructure in the middle of specimens. Consequently, these kind of simulated specimen are not suitable for standard tensile tests, and even for Charpy impact tests, the simulated area can be too narrow. Therefore, to investigate the mechanical properties of a fine-grain heat-affected zone in 18CrNiMo7-6 steel, two methods were used for simulation of as-welded microstructures: (a) a weld thermal cycle simulator, and (b) as an alternative, though not yet verified option, austenitizing in a laboratory furnace + water quenching. The microstructures were compared and mechanical properties investigated. The grain sizes of the simulated specimens were 10.9 μm (water-quenched) and 12.6 μm (simulator), whereby the deviations from the real weld were less than 10%. Both types of simulated specimen were used for hardness measurement, Charpy impact tests, and fatigue tests. Water-quenched specimens were large enough to enable standard tensile testing. A hardness of 425 HV, yield strength R(p02) = 1121 MPa, tensile strength R(m) = 1475 MPa, impact energy KV = 73.11 J, and crack propagation threshold ΔK(thR) = 4.33 MPa m(0.5) were obtained with the water quenched specimens, and 419 HV, KV = 101.49 J, and ΔK(thR) = 3.4 MPa m(0.5) with the specimens prepared with the simulator. Comparison of the results confirmed that the annealed and quenched specimens were suitable for mechanical tests of FG HAZs, even for standard tensile tests. Due to the use of simulated test specimens, the mechanical properties determined can be linked to the FG HAZ microstructure in 18CrNiMo7-6 steel.
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spelling pubmed-95732722022-10-17 Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel Vuherer, Tomaž Smaili, Fidan Bjelajac, Edvard Manjgo, Mirza Lojen, Gorazd Materials (Basel) Article Heat-affected zones (HAZs) in real welds are usually quite narrow, and consequently most standard mechanical tests are difficult or even impossible. Therefore, simulated microstructures are often used for mechanical tests. However, the most often used weld thermal cycle simulator produces only a few millimeters wide area of simulated microstructure in the middle of specimens. Consequently, these kind of simulated specimen are not suitable for standard tensile tests, and even for Charpy impact tests, the simulated area can be too narrow. Therefore, to investigate the mechanical properties of a fine-grain heat-affected zone in 18CrNiMo7-6 steel, two methods were used for simulation of as-welded microstructures: (a) a weld thermal cycle simulator, and (b) as an alternative, though not yet verified option, austenitizing in a laboratory furnace + water quenching. The microstructures were compared and mechanical properties investigated. The grain sizes of the simulated specimens were 10.9 μm (water-quenched) and 12.6 μm (simulator), whereby the deviations from the real weld were less than 10%. Both types of simulated specimen were used for hardness measurement, Charpy impact tests, and fatigue tests. Water-quenched specimens were large enough to enable standard tensile testing. A hardness of 425 HV, yield strength R(p02) = 1121 MPa, tensile strength R(m) = 1475 MPa, impact energy KV = 73.11 J, and crack propagation threshold ΔK(thR) = 4.33 MPa m(0.5) were obtained with the water quenched specimens, and 419 HV, KV = 101.49 J, and ΔK(thR) = 3.4 MPa m(0.5) with the specimens prepared with the simulator. Comparison of the results confirmed that the annealed and quenched specimens were suitable for mechanical tests of FG HAZs, even for standard tensile tests. Due to the use of simulated test specimens, the mechanical properties determined can be linked to the FG HAZ microstructure in 18CrNiMo7-6 steel. MDPI 2022-09-30 /pmc/articles/PMC9573272/ /pubmed/36234121 http://dx.doi.org/10.3390/ma15196782 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Vuherer, Tomaž
Smaili, Fidan
Bjelajac, Edvard
Manjgo, Mirza
Lojen, Gorazd
Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title_full Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title_fullStr Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title_full_unstemmed Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title_short Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel
title_sort simulation and mechanical properties of fine-grained heat-affected zone microstructure in 18crnimo7-6 steel
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9573272/
https://www.ncbi.nlm.nih.gov/pubmed/36234121
http://dx.doi.org/10.3390/ma15196782
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