Determination of t8/5 cooling times for underwater local dry welding of steel |
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| Affiliation: | 1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China;2. Department of Naval Architecture and Ocean Engineering, Tianjin University, Tianjin, 300072, China;1. State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Dalian University of Technology, Dalian, 116024, China;2. Ningbo Research Institute of Dalian University of Technology, Ningbo, 315016, China;3. College of Mechanical and Electrical, Harbin Engineering University, Harbin, 150001, China;1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin, 300072, China;2. Maritime College, Tianjin University of Technology, Tianjin, 300384, China;3. Southern Offshore Wind Power Joint Development Co. Ltd, ZhuHai, 519080, China;1. Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, 4036, Stavanger, Norway;2. Department of Manufacturing and Civil Engineering, Norwegian University of Science and Technology, 2815, Gjøvik, Norway |
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| Abstract: | Knowledge of thermal history is the basic condition for studying the structure - properties of welded joints. The determinant of thermal history is the thermal cycle, whose in-situ measurements are still a big challenge. Water as the welding environment complicates this issue even more. The article presents a method to determine an equation for calculating t8/5 cooling times for underwater gas metal arc welding of unalloyed steels using the local dry cavity method. The work uses the contact method of temperature measurements with the use of thermocouples to obtain the temperature changes of the points of welded joints covered by the thermal field. On this basis, the values of the t8/5 cooling times were determined. A regression analysis of the Response Surface Method was used to determine the equation, which resulted in a second-order model with interactions. Statistically significant factors were determined (thickness of welded elements and heat input value) and the model veracity was confirmed as the assumptions of normality and homogeneity of variance (homoscedasticity) of the residuals were met. The t8/5 cooling time values depend on the thickness of the welded elements and heat input value in a nonlinear way. In terms of the test conditions, the cooling times ranged from 3.0 to 7.7 s. The equation allowed for the calculation of t8/5 cooling times during underwater welding of unalloyed steels using the local dry cavity method based on the variability of the experimental conditions with satisfactory accuracy. |
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| Keywords: | Underwater welding Local cavity method Welding thermal cycle Response surface method Statistical analysis |
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