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20171223-FORQ-Thesis_.pdf (5.88 MB)

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Simplified Computational Modeling Approach for Analysis and Optimization of Temperbead Welding Procedures

Forquer, Matthew T
http://orcid.org/0000-0001-8699-4584
http://rave.ohiolink.edu/etdc/view?acc_num=osu151403940876477

Abstract Details

2018, Master of Science, Ohio State University, Materials Science and Engineering.
Dissimilar Weld Overlays (DWOLs) are common in the oil and gas, power generation, and petrochemical industries. The most common overlays consist of low alloy steel components overlayed with Ni-base filler metals. These DWOLs typically require a post-weld heat-treatment to temper martensite that forms in the heat-affected zone (HAZ) of the steel substrate. There are multiple phenomena-based issues associated with post weld heat treatment (PWHT) of DWOLs; it is expensive and impractical for field implementation. A temper bead welding (TBW) procedure that eliminates the need for PWHT is often preferred. Trial-and-error is the current practice for developing TBW procedures. Qualification for TBW procedures require a lot of material and time, it is expensive and therefore, it is often not practical. The objective this research project was the development of an efficient methodology for analysis and optimization of TBW parameters, resulting in reduced cost for development and qualification of TBW procedures used for production of DWOLs. It involves developing a robust computational model that accurately predicts the tempering effect in multi-pass multi-layer overlays. This approach is based on computational modeling of HAZ thermal histories in DWOLs overlays. Tools utilized were ESI’s Visual-Environment / SYSWELD for finite element modeling (FEA) and JMatPro for prediction of thermo-physical properties of the utilized base metals and welding filler metals. A heat source was modified and tuned to match the heat profile experienced in DWOLs during cold wire gas tungsten arc welding. FEA models of three-layer DWOLs were created for three levels of heat input, low (L), medium (M), and high (H), in six different layer combinations, LLL, MMM, HHH, LMM, LMH, and LHH. Bead geometries corresponding to each level of heat input were implemented in the FEA models. The developed FEA models were solved to predict the multiple reheat thermal histories experienced in the base metal HAZ of modeled DWOLs. An approach for quantification of thermal histories was developed and applied to evaluate the efficiency of welding procedures in tempering the martensite that forms in the HAZ. The sequence of weld thermal cycles experienced in HAZ, their maximum temperatures, and the number of reheats within a predefined tempering temperature range were used as criteria for tempering efficiency evaluation. The developed FEA models were verified by comparing predicted thermal histories to thermocouple measurements in the HAZ of DWOLs produced with the same welding parameters. Good correlation was found between predicted and measured thermal cycles in single bead welds. The deviations between the maximum temperatures of predicted and measured thermal cycles for multilayer DWOLs varied mostly between 1oC and 100oC. The reasons for these deviations need further investigation. In a parallel project, a tempering response parameter was developed to predict HAZ hardness in DWOLs by considering multiple reheats. That tempering response parameter was applied with thermal histories generated by an FEA model to predict HAZ hardness in a single layer DWOL. Good correlation was found between the predicted HAZ hardness and the measured one in actual DWOL produced with the same welding procedure. The proposed methodology provides tolls for layer-by-layer analysis of the tempering effect of each layer in DWOLs. Using a model based design of experiment approach, this methodology can be applied for quantification of the effect of welding parameters on the HAZ thermal histories in DWOLs and for more-efficient development and optimization of TBW procedures. It is also applicable for microstructural optimization in multipass welds and additively manufactured components of materials that undergo solid-state phase transformations.
Boian Alexandrov, PhD (Advisor)
Avraham Benatar, PhD (Committee Member)
140 p.
Materials Science

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Citations

  • Forquer, M. T. (2018). Simplified Computational Modeling Approach for Analysis and Optimization of Temperbead Welding Procedures [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu151403940876477

    APA Style (7th edition)

  • Forquer, Matthew. Simplified Computational Modeling Approach for Analysis and Optimization of Temperbead Welding Procedures. 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu151403940876477.

    MLA Style (8th edition)

  • Forquer, Matthew. "Simplified Computational Modeling Approach for Analysis and Optimization of Temperbead Welding Procedures." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu151403940876477

    Chicago Manual of Style (17th edition)

osu151403940876477
887
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