The evolution of metallic alloys over the past century has been pivotal in advancing various critical industries, including nuclear energy, aerospace, medicine, and petrochemicals. Developing materials such as low alloy creep-resistant steels, nickel-based alloys with high-temperature properties, and lightweight titanium alloys with exceptional strength-to-weight ratios has driven remarkable progress. However, the integrity of these materials during manufacturing, particularly during fusion welding, is crucial to maintaining their superior properties.
A prime example is stainless steel, where maintaining the right balance of elements, such as chromium, is vital for corrosion resistance and mechanical strength. During welding, even minimal exposure to oxygen, with levels as low as 50 ppm, can significantly reduce chromium content, leading to compromised corrosion resistance and mechanical properties. The same concern applies to other advanced materials like chromium/molybdenum/vanadium alloys and titanium alloys, which are sensitive to contamination during welding, making the control of the welding environment essential.
To address these challenges, purging the weld area with inert gases like argon is a common practice to eliminate oxygen and other contaminants. While traditional methods, such as pipe welding systems and trailing shields, are effective, the increasing complexity of three-dimensional components in industries like aerospace and nuclear energy demands more comprehensive solutions. These components are best fabricated within sealed enclosures, where the entire welding process occurs in an inert atmosphere, effectively reducing oxygen levels to well below 10 ppm and preventing contamination.
Weld enclosures, particularly metal chambers and glove boxes, have been in use for decades. These enclosures provide an inert atmosphere during fusion welding. While these traditional metal enclosures are effective, they have limitations that have been successfully addressed by the latest generation of flexible welding enclosures.
Flexible Welding Enclosures offer significant advantages over their metal counterparts. They are far more cost-effective, typically costing only a fraction of the price of metal enclosures. This cost advantage increases with size, making flexible enclosures an economical choice for large-scale applications. In addition to being lighter and easier to ship and manoeuvre, flexible enclosures can be deflated and stored when not in use, occupying minimal space and weighing as little as 8 kg for a 1.25-meter diameter model. Manufacturing times for flexible enclosures are also considerably shorter, with some models available off the shelf and custom versions ready in under eight weeks.
Flexible enclosures are designed with smooth surfaces and rounded corners, eliminating the risk of trapping air pockets, a common issue with traditional metal glove boxes. They also provide excellent access and visibility, which is essential for precise welding operations, and are available in a wide range of sizes. This flexibility makes them particularly well-suited for applications such as 3D production and additive manufacturing, where CNC or robotic welding systems are often used.
For example, a commercial spin-off from Cranfield University in the UK uses flexible enclosures in the Wire Arc Additive Manufacturing (WAAM) process to produce aerospace parts. These enclosures, made from translucent PVC materials and optically transparent sheets, offer large viewing areas and multiple access points, allowing several operators to work simultaneously ideal for production and training purposes.
Monitoring the Purge Gas Oxygen Content ensures weld quality in these environments. Even small amounts of oxygen can cause discolouration and reduce corrosion resistance. To address this, the PurgEye® family of instruments from Huntingdon Fusion Techniques offers precise oxygen monitoring, which is essential for maintaining the desired low oxygen levels within flexible enclosures. The PurgEye® 500 Weld Purge Monitor® is an advanced tool that meets the stringent requirements of high-quality welding, measuring oxygen levels as low as 10 ppm. This instrument is equipped with an integral pump to ensure consistent gas flow to the oxygen sensor, advanced software for data acquisition, and communication tools like PurgeNet™ and PurgeAlarm™ for real-time monitoring and alerts.
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