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Titanium tube welding requirements
Titanium tube has higher strength bai degree, good plastic toughness du and corrosion resistance, dao is more and more widely used in aerospace, shipbuilding, chemical industry. If you want to make better use of titanium tube, you must master its weldability. This article mainly describes the welding process of titanium tubes, which provides a useful reference for the welding of titanium tubes in the future.
1. Welding materials
Welding wire: ERTi-2; welding method: GTAW (manual tungsten arc welding)
Protection gas: Use argon gas with a purity of 99.995% and a water content of not more than 50Mg%m3. Argon gas is used for the areas of the welding molten pool and the temperature of the inner and outer surfaces of the welding joints above 400℃.
2. Preparation before welding
(1) Bevel processing
After cutting the titanium tube, use aluminum oxide grinder to grind the groove, as shown in the figure below, the processing of the groove is not allowed to cause the base material to overheat and discolor.
(2) Cleaning of groove and welding wire
A. Clean the inner and outer surfaces of the bevel and both sides within 50mm, the cleaning procedure is as follows:
Grinding machine polishing → sanding wheel polishing → acetone cleaning.
After cleaning, the welding operation cannot be directly performed, and the end surface of the bevel can be dried before operation. If it is left for more than 2 hours, you must clean it again or use self-adhesive tape and plastic cloth to protect the bevel.
B. The welding wire is also wiped clean with a sponge dipped in acetone and stored in a special welding wire box.
C. The operator must wear clean gloves during the welding process.
3. Welding process specification
(1) Welding specifications: as follows
(2) When welding, small line energy welding should be selected within the range of qualified process parameters, generally controlled at 6~35KJ/cm, and low current and slow welding should be used.
(3) The interlayer temperature should not be higher than 200℃, to prevent the high temperature time from growing for too long.
(4) In order to protect the surface at the end of the arc after the arc is broken, the temperature of the welding point should be below 300 ℃ (the time is 15~60s, which can be gradually extended according to the pipe diameter from small to large) and then stop the gas supply protection.
(5) Argon protection: specific measures are as follows:
A. For the welding of pipes with a DN greater than or equal to 450, the workers in the pipes put on gas masks and hold the protective cover to protect the back of the welding pool.
B. For the welding of pipes or fixed ports with a DN less than 450, the whole is filled with argon for protection. The inner surface of the pipe is 150-300mm away from the groove with a soluble paper seal, and then a ball of soluble paper is inserted to prevent the pressure in the pipe from being too high. The paper is destroyed, and then filled with argon to exhaust the air in the tube. Argon gas must be fully pre-filled before welding, and argon refill should be delayed after welding to fully cool the high temperature area and prevent surface oxidation.
(6) During the welding process, the filler wire should always be kept under the protection of argon gas. After the arc is extinguished, the welding wire shall not be immediately exposed to the atmosphere, and shall be taken out when the weld is removed from protection. If the welding wire is contaminated or oxidized, the contaminated part should be removed.
(7) It is not allowed to initiate arc or test arc on the surface of the weldment; the arc pit should be filled when the arc is closed, and the interlayer joints of the multi-layer welding are staggered from each other.
(8) Except for special requirements, each weld should be continuously welded once. If it is forced to be interrupted for some reason, it must be inspected when re-welding, and the welding can be continued after confirming that there is no crack.
(9) If tungsten is caught accidentally during the welding operation, the welding operation should be stopped, the tungsten point should be cleared with a polisher, and the tungsten grade end should be re-polished, and the welding operation can be resumed after meeting the requirements.