Manual Welding Technology Of Titanium Alloy Conduit

1. Clean before welding.

The occurrence of welding defects is closely related to the surface cleanliness of weldments and welding wires. Before welding, the oil dirt, water, oxide film and other dirt within the range of 15~20mm from the pipe joint edge and the welding wire surface shall be cleaned. The cleaning method can be chemical method (pickling) or mechanical method (stainless steel brushing) to remove the surface oxide scale. Before welding, acetone or alcohol shall also be used to scrub. The cleaned weldment must be welded within 24h, otherwise it needs to be cleaned again. The welding wire should be subject to vacuum dehydrogenation after pickling, and degreased with acetone before welding.

2. Gas protection.

When welding titanium pipe joints, in order to prevent the welding joints from being polluted by harmful gases and elements at high temperature, the necessary argon protection must be carried out for the weld, with the purity not less than 99.99%.

3. Selection of welding process parameters.

(1) Selection of welding wire. The grade of filler welding wire shall be selected according to the base metal. Generally, the principle of homogeneity with the base metal is adopted. Sometimes, in order to improve the plasticity of the joint, the welding wire with a slightly lower alloying degree than the base metal can also be selected. The diameter of welding wire shall be selected according to the thickness of base metal.

(2) Power supply and polarity selection. Titanium and titanium alloy welding generally adopts DC manual tungsten argon arc power supply, and its polarity connection method adopts DC positive connection.

(3) Selection of tungsten electrode. The diameter of tungsten electrode is selected according to the wall thickness of titanium alloy pipe, which is generally between 1.0-3.0mm. The tungsten electrode should be ground into a cone of 25 °~45 °.

(4) Selection of welding current and other parameters