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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MDPI AG
2022-09-01
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| Online Access: | https://www.mdpi.com/1996-1944/15/19/6782 |
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| author | Tomaž Vuherer Fidan Smaili Edvard Bjelajac Mirza Manjgo Gorazd Lojen |
| author_facet | Tomaž Vuherer Fidan Smaili Edvard Bjelajac Mirza Manjgo Gorazd Lojen |
| author_sort | Tomaž Vuherer |
| collection | DOAJ |
| 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 <i>R</i><sub>p02</sub> = 1121 MPa, tensile strength <i>R</i><sub>m</sub> = 1475 MPa, impact energy <i>KV</i> = 73.11 J, and crack propagation threshold Δ<i>K</i><sub>thR</sub> = 4.33 MPa m<sup>0.5</sup> were obtained with the water quenched specimens, and 419 HV, <i>KV</i> = 101.49 J, and Δ<i>K</i><sub>thR</sub> = 3.4 MPa m<sup>0.5</sup> 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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| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T21:30:57Z |
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| spelling | doaj.art-e2eef9c0e10541ea942b03464f85a87f2023-11-23T20:56:39ZengMDPI AGMaterials1996-19442022-09-011519678210.3390/ma15196782Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 SteelTomaž Vuherer0Fidan Smaili1Edvard Bjelajac2Mirza Manjgo3Gorazd Lojen4Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaFaculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaFaculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaFaculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaFaculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, SloveniaHeat-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 <i>R</i><sub>p02</sub> = 1121 MPa, tensile strength <i>R</i><sub>m</sub> = 1475 MPa, impact energy <i>KV</i> = 73.11 J, and crack propagation threshold Δ<i>K</i><sub>thR</sub> = 4.33 MPa m<sup>0.5</sup> were obtained with the water quenched specimens, and 419 HV, <i>KV</i> = 101.49 J, and Δ<i>K</i><sub>thR</sub> = 3.4 MPa m<sup>0.5</sup> 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.https://www.mdpi.com/1996-1944/15/19/6782weld jointfine-grained HAZsimulation of microstructurehardnessimpact toughnesstensile properties |
| spellingShingle | Tomaž Vuherer Fidan Smaili Edvard Bjelajac Mirza Manjgo Gorazd Lojen Simulation and Mechanical Properties of Fine-Grained Heat-Affected Zone Microstructure in 18CrNiMo7-6 Steel Materials weld joint fine-grained HAZ simulation of microstructure hardness impact toughness tensile properties |
| 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 | weld joint fine-grained HAZ simulation of microstructure hardness impact toughness tensile properties |
| url | https://www.mdpi.com/1996-1944/15/19/6782 |
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