What are the process requirements for Gr2 titanium welded pipe welding?

Titanium welded pipe has high strength, excellent plastic toughness and corrosion resistance, and is widely used in aerospace, shipbuilding and chemical plants. In order to better utilize the titanium welded pipe, you need to master its welding performance.

Welding wire:ERTi-2; Welding method:GTAW(manual tungsten argon arc welding)

Protective gas: the use of 99.995% purity, water content of not more than 50Mg%m3 of argon, argon protection welding pool and welding joints inside and outside the surface temperature of the region above 400 ℃.

Titanium welded pipe welding before the preparation work.

First, bevel processing.

After the titanium welded pipe is cut, the bevel is polished with an aluminum oxide sander, and the parent material is not allowed to be overheated and discolored.

2) Clean the bevel and welding wire.

A. Clean the bevel and its internal and external surfaces within 50 mm on both sides. The cleaning procedure is as follows.

Grinding machine grinding → sandpaper wheel grinding → acetone cleaning.

Cleaning can not be directly after the welding operation, the bevel end face dry before the operation. If it is left for more than 2 hours, it needs to be cleaned again or the bevel is protected with self-adhesive tape and plastic sheet.

B. Welding wire is also wiped with acetone-impregnated sponge and stored in a special welding wire box.

Operators must wear clean gloves during the welding process.

Titanium welded pipe welding process specifications.

1. Welding specifications.

2. Welding, should be in the qualified process parameters within the scope of the choice of small wire energy welding, generally controlled at 6~35KJ/cm, using small current, slow welding.

3. The interlayer temperature shall not exceed 200 ℃, so as to avoid grain growth at high temperatures too long.

4. In order to protect the surface of the arc after the arc break, the welding point temperature should be below 300 ℃ (time 15 ~ 60s, according to the diameter of the pipe from small to large and gradually extended), and then stop feeding protection.

5. Argon protection: specific measures are as follows:

Welding DN greater than or equal to 450 of the pipeline, the pipeline staff should wear gas masks and protective cover to protect the back of the welded molten pool.

DN less than 450 of the pipeline or fixed port for welding, the overall argon protection, the inner surface of the pipeline from the bevel 150-300mm sealed with soluble paper, and then stuffed with a ball of soluble paper to prevent excessive air pressure in the pipeline, destroying the sealing of the soluble paper, and then filled with argon to discharge the air in the pipeline. Welding must be fully pre-filled with argon, welding should be delayed after argon, so that the high temperature region fully cooled to prevent surface oxidation.

6. Welding process filler wire should be kept under the protection of argon. After the arc is extinguished, the wire should not be exposed to air immediately, and should be removed when the weld leaves the protection. If the wire is contaminated and oxidized and discolored, the contaminated part should be removed.
7. The surface of the weldment shall not lead the arc or test arc; the arc pit shall be filled when closing the arc, and the ends between the layers of multi-layer welding shall be staggered.

8. In addition to special requirements, each weld should be continuously welded once. If for some reason forced to interrupt, and then need to check the welding, to confirm that no cracks before continuing to weld.

9. When tungsten is accidentally caught in the welding operation, pause the welding operation, clean the tungsten point with a grinder, regrind the tungsten grade end, and then carry out the welding operation after meeting the requirements.

The above process points to ensure the normal welding of titanium welded pipe, but also to meet the requirements of titanium welded pipe welding quality.