Clean technology of titanium alloy

Before welding titanium, it is important that the welding joints and welding wires do not have oxide scale, dust, grease, oil, moisture and other potential contaminants. Including these foreign substances in the titanium, weld metal will reduce performance and corrosion resistance. The welding wire packaged by the manufacturer is clean. If the wire looks dirty, it is best to wipe it with a non-chlorinated solvent before use. In severe cases, pickling may be required. All bonding surfaces and surfaces of the substrate must be cleaned at least one inch away from the joint.

The surface of ordinary pickling machines usually only needs to be scrubbed with household thinner or detergent, and then rinsed thoroughly with hot water and air drying. In addition, if there is no residue, use a clean lint-free cloth or cellulose sponge to wipe the weld and adjacent areas with a chlorine-free solvent such as toluene, toluene or methyl ethyl ketone (MEK). These solvents are particularly effective in removing trace amounts of grease and oil. A new stainless steel brush should be used for solvent cleaning. In any case, steel brushes or steel wool should not be used on titanium due to the risk of corrosion resistance caused by embedded iron particles.

The light oxide film, formed by heating in the range of 600°-800°F (316-427°), can be removed by brushing with a new stainless steel wire brush. Light grinding, filing and pickling are also effective. An acceptable acid bath for titanium is to use 35 vol% nitric acid (70% concentration) and 5% hydrofluoric acid (48% concentration) at room temperature. Soaking the welding area for 1 to 15 minutes (depending on the activity of the bathtub) should be sufficient.

Rinse with cold water to remove acid, then rinse with hot water to facilitate drying and complete the cleaning. Heavy scale and oxygen-contaminated surfaces that may exist after high-temperature heat treatment are best removed by mechanical methods. Grinding and sanding or sandblasting are usually used. Although useful, molten caustic baths require care to minimize the possibility of hydrogen absorption. After descaling, pickling should be used to remove all residues and improve surface appearance.

Once cleaned, joints should be carefully stored. Handling should be reduced as much as possible, and welding should be started as soon as possible after cleaning. When not working, the welds should be covered with paper or plastic to avoid the accumulation of contaminants.
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