How To Weld A TA2 Titanium Tube

How to Weld a TA2 Titanium Tube

welded TA2 Titanium Tube.jpg


Titanium tubing is a high-strength and low-density metal, it’s very well suited to applications where both weight and strength are critical, such as in the aerospace, automotive, and military and defense industries.To make better use of titanium tubes, it is necessary to understand its welding performance.In this article,I will introduce some tips about how to weld TA2 Titanium Tubing.

 

1.Welding Material

Perhaps the most important factor in obtaining quality titanium welds is proper preparation and maintenance of the welding materials. We should choose the welding process of gas turbine arc welding(GTAW) and STA2R weld wire for TA2 Titanium Tubes.

●GTAW gives the welder more control over heat input and the puddle than any other welding process. A GTAW inverter with high-frequency arc starts, remote amperage control capabilities, a postflow timer, and an output of at least 250 amps, will weld titanium nicely.

●Typically, you should match the weld wire to the grade of titanium being welded—it should be an exact match.The chemical composition and mechanical properties of the wire should be equivalent to the titanium tube.Any variation,however,should be carefully tested and investigated to make sure it meets process demands and specifications.

 

2. Preparation before welding

●The cleanness of surface is extremely important.Joint surfaces must be smooth, clean, and completely free of contamination. Weld joints and wire must be free of mill scale, dirt, dust, grease, oil, moisture, and other contaminants.When preparing the surface only use a stainless steel brush that is exclusively used on titanium to minimize cross contamination from other metals.Any contaminants introduced to the titanium will degrade its performance and corrosion resistance.

●Shielding gas coverage is critical.Pure argon is recommended for welding titanium because of its high purity and low moisture content. A 75/25 mixture of argon/helium may be used to improve stability and increase penetration only when specified.

The American Welding Society (AWS) recommends measuring welding gas purity to make sure it meets the standards set for each application. Typical specifications suggest that shielding gas be at least 99.995 percent pure with no more than 20 parts per million (PPM) of oxygen and a dew point greater than -76 degrees F. Other applications require a 99.999 percent pure flow of argon.

 

3. Welding

Once welding begins, the air itself becomes a contaminant to the molten titanium. Oxygen contamination is an extremely common cause of substandard welds. Not only the weld itself but the HAZ and root side of the weld must be shielded from air when their temperature rises to over 800°F. Usually, pure argon is the preferred shield gas. Occasionally,argon mixed with helium is a choice.

 

4. After welding

● Clean welded titanium pipes with light oxide scaling by acid pickling. A common pickling solution is 48% hydro-fluoric acid and 70% nitric acid. Metals to be welded should be pickled for 1 to 20 minutes at a bath temperature from 80 to 160°F. After pickling, rinse the parts in hot water. With heavier scaling, you may need to precede the pickling by mechanical removal or more radical high-temperature pickling

●Make sure all the leads, fitting have been tested for leaks to ensure there is no oxygen contamination.All welding seam shall be inspected, such as appearance inspection, X ray examination, coloring and pressure test. Theoretically, all weld joints must be qualified. If there is any unqualified, it is necessary to repair them.



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