Abstract
The effectiveness of the welding process depends on some attributes, such as costs, the production time, and the quality of welding joints. This matter is more vital when dealing with the thick plates of steel for special structures in industry. To provide the quality when joining thick plates, especially with narrow gap and small chamfer angle, it is necessary to design the progressive process focusing on the main parameters, including the arc power, the translational velocity, and the rotational velocity of the tip. To evaluate the stability and the reliability of this technique, it must also perform the microstructure analysis in different zones of welding joint. In this chapter, previous publications related to this topic were gathered and analyzed. Particularly, several findings in recent studies for improving this progressive technology in the manufacturing area were discussed in detail.
TopDefinitions
The formulation of this phenomenon is defined by the American Welding Society (AWS) as follows: a variation of a multiple pass welding process with filler metal, using a small root opening and V-groove with a small groove angle”. Another significant feature yields a weld joint with a high ratio of depth to width.
Narrow Gap Welding (NGW) refers to narrow groove weld between two thick plates, applying to butt welding Type I or X groove. Normally, butt weld is considered NGW when the chamfer angle is typically in ranges 2-20º. Accordingly, the thickness of plates can reach 50 – 100 mm (see Figure 1, 2, 3). This requires less weld metal and less heat input in comparison with traditional welding technologies.
Concerning the groove width in welding joint, various interpretations have been given depending on the progression of welding equipment, but the nominal value is in range: 9-18 mm (Jia et al., 2018).
Figure 3. U-shaped groove for narrow-groove butt- joint welding
TopAdvantage And Disadvantage
Advantage
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The process provides better saving of consumable and welding time. Excellent weldproperties.
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Low distortion and residual stress due to the joint preparation is almost parallel- side and less heat input.
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Reduced labor costs.
Disadvantage
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The risk of sidewall infusion.
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The poor joint accessibility limits the removal of any failure when detected.
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J-groove preparation is more expensive in comparison with other common types of groove design.
Progressive Processes
Since of many advantages, the NGW techniques are well- established for: gas metal arc welding (GMAW), submerged arc welding (SAW), gas tungsten arc welding (GTAW), Hybrid Laser Welding (HLW).