In the previous article in this blog, I’ve been mentioned and explain ebout underwater welding by divers. In offshore construction, espescially in installation underwater pipeline, the welding not only can be done underwater, but also above water, although in offshore environment. In this article, I will explain about other type of offshore welding technology other than underwater technology.

There are diversity of welding processes such as solid state welding (resistance, cold, friction, ultrasonic, etc.), soldering/brazing, and fusion welding. Soldering/brazing melts only filler materials not base materials. However, the fusion welding involves partial melting of base material (called heat affected zone). Electrical energy (electrode) is commonly used for the fusion welding.

Shielded Metal Arc Welding (SMAW) is frequently referred to as stick welding. The flux covering the electrode melts during welding and this forms the gas and slag to shield the arc and molten weld pool. The slag must be chipped off the weld bead after welding.

Gas metal arc welding (GMAW) uses an arc between a consumable constant filler metal electrode and the weld pool. Shielding is provided by an externally supplied shielding gas. This method is also known as metal inert gas (MIG) welding or metal active gas (MAG, i.e. carbon dioxide or oxygen) welding.

GMAW consists of a DC arc burning between a thin bare metal wire electrode and the work piece. The arc and weld area are encased in a protective gas shield. The wire electrode is fed from a spool, through a welding torch which is connected to the positive terminal. The technique is easy to use and fast (high productivity) and there is no need for slag-cleaning since no flux is used. The MAG process is suitable for steel, low-alloy, and high-alloy based materials. The MIG process, on the other hand, is used for aluminum and copper materials.

Gas tungsten arc welding (GTAW) is more commonly known as tungsten inert gas (TIG) welding. It is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The electrode used in GTAW is made of tungsten, because tungsten has the highest melting temperature among metals. As a result, the electrode is not consumed during welding, though some erosion (called burn-off) may occur.

GTAW is most commonly used to weld thin sections of stainless steel and light metals such as aluminum, magnesium, and copper alloys. The process is known for creating stronger and higher quality welds than SMAW and GMAW. However, GTAW is comparatively more complex and difficult to master. It is also significantly slower than most other welding techniques.

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Source:

Lee, Jaeyoung. Introduction to Offshore Pipelines and Risers. 2007.