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Effect of cold wire addition in tandem submerged arc welding on weld geometry and micro-hardness of heavy gauge X70 steel
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- Author(s) / Creator(s)
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The pipeline industry has undertaken an essential upgrade of well established X70 pipeline steel in heavy gauge pipes to fill the demand of increased operating pressures. A developed welding process, cold wire tandem submerged arc welding (CWTSAW), with improved deposition rate and travel speed can meet this upgrade. Currently, the effect of CWTSAW process parameters and bevel design on the change in weld geometry and properties of the weld and heat-affected zone (HAZ) in heavy gauge X70 pipe is not well understood. In this article, a series of weld trials were conducted on heavy gauge (19.1 mm) X70 steel plates to investigate the effect of cold wire feed speed, heat input and bevel design on the reinforcement size, coarse grained heat-affected zone (CGHAZ) area, ratio of weld shapes and micro-hardness of the weld and HAZ. The results showed that the cold wire feed speed significantly influenced the micro-hardness profiles, and bevel design was the dominant factor influencing the reinforcement size and CGHAZ area. In addition, empirical equations of micro-hardness profiles of the CWTSAW samples were developed using a non-linear regression analysis. The phase fraction and morphology of martensite-austenite (MA) constituents were analyzed using optical microscopy and scanning electron microscopy. The microstructural results indicated lower MA fractions with fine and dispersed MA constituents obtained in the CGHAZ of the CWTSAW samples than for conventional tandem submerged arc welding samples. This can be interpreted as the reason for the lower hardness in the CGHAZ of the CWTSAW samples.
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- Date created
- 2022-01-01
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- Type of Item
- Article (Published)