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How to Weld Titanium with Keyhole TIG
      Titanium and titanium alloys are known for their low density, high specific strength, wide operating temperature range, and excellent corrosion resistance. They are used in many different fields such as food, chemical, power, aerospace, nuclear energy, warships, and many other industry sector . Due to the physical and chemical characteristics of titanium alloys, welds are easily oxidized and nitrided during welding, causing contamination, and the joints are brittle and sensitive. Therefore, it is very challenging to weld them. The more common welding processes are manual argon arc welding(GTAW) and plasma arc welding(PAW or P+T). However, these two processes have relatively large deficiencies. The manual argon arc welding has low welding efficiency, high labor cost, and plasma welding is very strict with the requirements of the beveling and needs to be machined by expensive groove processing equipment, and the operator's requirements are also very high.
    Keyhole TIG (K TIG) technology combines the high quality and cleanliness of GTAW with a depth of penetration that is unmatched by conventional GTAW or plasma welding processes.  This patented technology is a result of extensive, scientific study of the gas-tungsten-arc process and many innovations in arc characteristics, weld pool stabilization, heat removal and process efficiency.
       Keyhole TIG has 8X the penetration of GTAW, allowing it to perform X-ray quality welds in materials up to16 mm  thick in a single pass, without the need for edge beveling and filling material. The resulting welds are performed at up to 10X the speed of conventional TIG/GTAW. Gas consumption is reduced by more than 60 percent and wire consumption is reduced by in excess of 90 percent or eliminated entirely. The physics of the Keyhole TIG process create high energy density in the welding arc, allowing it to open up a ‘keyhole’ and fully penetrate the material being welded and weld at high speed. The minimization of the surface energy associated with the keyhole geometry and the relatively unrestricted egress of the arc gases combine to produce an extremely stable and benign weld pool. The molten metal within the weld pool is prevented from falling from the root face by surface tension created by the process.
        The Keyhole TIG torch is engineered to convert a high current arc into a plasma jet that fully penetrates the material and creates a high surface tension weld pool on the underside of the material. By managing the surface tension, Keyhole TIG can hold and stabilize the weight of the molten material while welding. The penetration capabilities of this process varies from material to material. It can achieve full penetration and single-pass welding on titanium alloy of 16 mm thickness. A key advantage of this impressive penetration is that there is no need for edge beveling or a gap. All that is required is a simple square butt presentation and the operator is ready to complete single pass titanium alloy welding.

The material range of keyhole TIG welding for titanium alloy is between 3 mm and 16mm . Within this thickness range, a full penetration butt weld is achievable in a single pass in both 1G and 2G positions, as well as longitudinal and circumferential welding at speeds as high as 1,000 mm/min in titanium alloy,titanium alloy pressure vessels and tanks are ideally suited to this process. Keyhole TIG has been replacing plasma keyhole welding technology for several years and there are no issues with closing out or tying in on circumferential welding with Keyhole TIG. This is an enormous advantage for titanium welding. Penetration is the key to Keyhole TIG’s dramatic impact on welding productivity. The ability to achieve full penetration without the need for edge beveling saves considerable time and resources, reduces costs and increases profits. By contrast, conventional TIG and PAW welding processes require costly V- or J- groove preparations, with the metal removed during the groove preparation replaced with expensive filler metal, and to ensure consistency the preparations must be machine-prepared.Due to the limitation of the penetration depth of the traditional TIG welding, multiple layers of welding are required to weld the titanium alloy plate, which not only consumes a large amount of expensive welding wire and protective gas, but also has low welding efficiency.
Titanium is known for its high propensity to distort when welding. Keyhole TIG’s ability to fully penetrate material and weld in a single pass means shrinkage and distortion are dramatically reduced. This is particularly beneficial for pipe spooling, when multiple joints are needed for a spool and overall length dimensions are critical for site fit up. K-TIG is intended to be used with welding automation that delivers a consistent travel speed. The requirements for automation are very simple: stable and consistent travel speed and a rigid torch mount. K-TIG can integrate with existing equipment, such as seamers, rotators, manipulators, column and booms and robots. The sophistication of the Keyhole TIG system and controller, combined with the consistent quality of an automated process, means both productivity and quality will typically increase significantly when transitioning to this technology.
Other benefits of using this process in titanium welding include:
Edge Preparation and Set-Up. In a perfect world, every square butt joint would have zero gap and unfitness, but this is challenging to achieve in production fabrication environments. Keyhole TIG has the ability to maintain a stable weld pool with15% plate thickness gaps and unfitness tolerances unmatched by other keyhole welding processes such as plasma arc welding and laser welding. The cutting method can be thermal cutting, shear cutting or machining.Additions of filling material can also be added to the full penetration keyhole pass in order to reduce the undercut, to compensate for the interface gap, to adjust the over-height, or to change the micro-structure of the weld metal..
Shielding Gas:The preferred shielding gas for K-TIG welding  is 100% argon 
Consumables:Filler wire can be added to the keyhole penetration pass to help maintain a stable weld pool when welding with slight gaps or mismatch in alignment. Also can take keyhole deep penetration pass without filling material,the second pass to cap with wire 
No matter which kind of process , the wire consumption is greatly reduced, typically by more than 95 percent.
 Gas consumption is also reduced due to the speed at which Keyhole TIG can weld. Consumables for all exotic materials are costly, meaning this reduction in consumables can be enormously helpful in improving your bottom line.

Surprisingly, an operator doesn’t require years of welding training and practical skills to perform quality stainless welding with this process. Although background knowledge of welding is preferred, the simplicity of the system allows operators to be trained in just several hours, while shop supervisors can receive comprehensive training in one to two days. This simple, yet highly effective welding system can also help address the chronic skills shortage in the welding and fabrication industry, where fewer and fewer young people are deciding to take up the trade
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