Manufacturers seek the highest level of quality and integrity for their final products. Achieving this, however, is a major challenge that technicians face. It requires thorough preparation and focused attention on material selection, machining, and cleanliness. Cleanliness must extend to the operating environment and the chosen equipment and materials. When welding, simple preparation processes like beveling the edges and surface cleaning can influence the quality of the final joint.
When employing orbital GTAW for applications like pipe welding, joint preparation and cleanliness are the keys to eliminating defects and improving the mechanical strength of the weld joints. In this article, we will discuss these important aspects of welding preparation.
Weld Preparation With Surface Cleaning
When welding any two workpieces, check for contaminants that could potentially harm the quality of the weld. These may include paints, wax, rusts, grease, slag, or metallic particles retained in the surface from machining and grinding. In the case of stainless steel, oxides may reside as a film that can affect arc control and return false feedback.
Removing each of these contaminants may require different methods of surface cleaning. Primarily methods include:
- Mechanical surface cleaning: Rusts, paints, coats, and contaminants can be removed from the upper surface of the metal with manual grinding. Only the pure metal remains for welding. When paired with GTAW (i.e., with proper shielding gas coverage), the process can be performed without any external influence. Metallic dust and particles that remain from grinding the metal can be removed by blasting the metal surface with compressed air or a wire brush.
- Chemical cleaning: Chemicals such as acetone or alcohol help to remove grease, oil, or oxidation from the surface.
- Electrochemical cleaning: Electropolishing is an effective cleaning method, especially for metals like stainless steel. The electrolyte solution can help dissolve the outer surface layer and any contaminants. This process removes burrs to even out the metallic surface and eliminate the breeding ground for bacteria.
These cleaning methods for regular or sanitary welding help ensure pure, strong welds. However, there is another preparation technique for enhanced quality.
Unique Joint Preparation for Orbital GTAW
Welders should be mindful of joint preparation techniques unique to orbital GTAW for creating a solid weld. J-groove machining of the edges and no gap butt welding are two examples of these techniques.
Applications like thick wall pipe welding require beveling to ensure complete penetration and consistent fusion through the larger pipe section. J-bevel is commonly desired when orbital welding. It produces a narrower gap when compared to other bevel types. Additionally, J-bevel welding can ensure the proper mechanical strength. The two J-prep pipe ends connect to form a U-shaped bevel without any gaps. In cases where narrow gaps are present, it should be no more than 5% of the pipe or tube thickness. For such connection, the butt-to-butt weld can be performed with or without filler metal. An orbital closed weld head is ideal for this task because it can easily access the root of the joint to provide a high-quality root pass and adequate penetration during welding.
Maintaining Overall Cleanliness To Improve Weld Quality
Cleanliness is a prerequisite in an orbital welding facility. Apart from the obvious weld surface cleaning, it is also essential to keep the worksite clean to reduce the environmental influence on the weld surface and improve operator safety. Clean weld heads and weld machines will provide a longer service lifespan. Additionally, proper cleanliness and joint preparation can help form joints with enough penetration and complete root fusion. Welding preparation that ensures contamination-free welds is more likely to produce defect-free welds and improve the overall weld precision and quality.
Arc Machines, Inc. leverages decades of experience and expertise to help manufacturers improve their weld quality by utilizing various welding preparation techniques and orbital welding solutions. For inquiries regarding products, contact sales@arcmachines.com. Arc Machines looks forward to providing the equipment and services your project needs. Contact us to learn more.
