Titanium tubes have high strength, good plastic toughness and corrosion resistance, and are widely used in aerospace, shipbuilding and chemical industry. In order to make better use of titanium tubes, it is necessary to know its weldability. This paper mainly describes the welding process of the titanium tube, which provides a useful reference for the future welding of titanium tube.
Welding wire: ERTi-2; welding method: GTAW (gas tungsten argon arc welding)
Protective gas: Argon gas with a purity of 99.995% and a water content of less than 50 mg/m3 shall be used for argon gas protection in the weld pool and the area of the inner and outer surfaces of the welded joint above 400 °C.
Preparation before welding
(1) Groove processing
Cut the titanium tube, and then polish the groove by an alumina grinder. The processing groove does not allow the base material to undergo superheat discoloration.
(2) Groove and wire cleaning
a. Clean the inner and outer surfaces of the groove. The cleaning procedure is as follows:
Grinding machine polishing → sanding wheel polishing → acetone cleaning.
After the cleaning, the welding operation cannot be performed after the groove end surface is dried. If it is left for more than 2 hours, it must be cleaned again or the bevel should be protected with self-adhesive tape and plastic cloth.
b. The wire is also wiped clean with a sponge dampened with acetone and stored in a dedicated wire box.
c. The operator must wear clean gloves during welding.
Welding procedure specification
(1) Small-line energy welding should be selected within the qualified process parameters during welding. Generally, it is controlled at 6~35KJ/cm. It is recommended to use small current and slow welding.
(2) The interlayer temperature should not be higher than 200 °C to prevent the grain growth from being too long at high temperature.
(3) In order to protect the surface of the arc after the arc breaking, the temperature of the soldering point should be below 300 °C (the time is 15~60s, which can be gradually extended according to the diameter of the pipe), and then the gas supply protection is stopped.
(4) The filler wire should always be kept under the protection of argon during the welding process. After the arc is extinguished, the wire shall not be exposed to the atmosphere immediately and shall be removed when the weld is removed from the protection. If the welding wire is contaminated or oxidized and discolored, the contaminated part should be removed.
(5) No arcing or test arc shall be applied on the surface of the weldment; the arc pit shall be filled when the arc is closed, and the interlayer joints of the multi-layer weld shall be staggered from each other.
(6) Except for special requirements, each weld shall be continuously welded once. If it is forced to be interrupted for any reason, it must be inspected during re-welding to confirm that there is no crack before continuing welding.
(7) If the tungsten is accidentally caught during the welding operation, the welding operation should be stopped, the tungsten point should be removed by the sander, and the tungsten grade end should be reground, and the welding operation can be resumed after the requirements are met.
The above-mentioned process points ensure the normal welding of the titanium tube and the welding quality requirements of the titanium tube.
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