How to weld copper and titanium plates?

The lattice type, melting point, thermal conductivity, coefficient of linear expansion and chemical composition of Titanium Clad Copper Plates are very different, so it is very difficult to weld.

 1) The weld is easy to form pores

(1) Copper and titanium have strong hydrogen absorption capacity at high temperature, and hydrogen has a large solubility in liquid copper and titanium.

(2) Gas is generated in the molten pool of pyrometallurgical reaction.

(3) Oxygen and nitrogen gases around the welding zone are immersed in the molten pool.

2) Welded joints tend to have large cracks

When copper and titanium are welded, eutectic and hydride can be formed on the metal side of the two base metals, and cracks are easily generated under the action of welding stress.

(1) Copper and bismuth form a (Cu+Bi) eutectic with a eutectic point of 270°C.

(2) Copper and aluminum form a (Cu+Pb) eutectic with a eutectic point of 326 °C.

(3) Copper and ferrous sulfide form a eutectic (Cu+Cu2O) with a eutectic point of 1067°C.

(4) Sheet-like hydride TiH2 is formed on the metal side of the titanium base material, resulting in hydrogen embrittlement.

(5) The coefficient of linear expansion of copper and titanium is more than 1 times different, and greater stress will be generated during welding.

 3) Low mechanical properties of welded joints

(1) The oxide film can weaken the intergranular bond between copper and titanium. For example, when the oxygen content in the weld reaches 0.38%, the bending angle of the joint decreases from 180° to 120°.

(2) A large amount of eutectic and hydride significantly reduces the plasticity and toughness of welded joints.

(3) The mutual solubility of copper and titanium is very small, and it is easy to form intermetallic compounds at high temperatures. Such as Ti2Cu, TiCu, Ti3Cu4, Ti2Cu3, TiCu2, TiCu4, increase brittleness, reduce plasticity, and significantly reduce the corrosion resistance of weld metal.

Copper and titanium or titanium alloys can obtain excellent welded joints by vacuum diffusion welding, argon arc welding, plasma arc welding, brazing and electron beam welding.

After the titanium base metal (TA2) was cleaned with trichloroethylene, it was etched in an aqueous solution with a volume fraction of 2% HF and a volume fraction of 50% HNO3 by vibration for 4 minutes to remove the oxide film, and then cleaned with water and alcohol .

(4) Assemble the cleaned two base metals according to the process requirements, and then put them into a vacuum furnace for welding. The welding parameters are: the welding temperature is 810℃±10℃, the pressure is 5~10MPa, the time is 10min, and the vacuum degree is 1.3332×10-8~ 1.3332×10-9MPa. An intermediate diffusion layer can be added between the two base metals. Usually, the material of the diffusion layer is niobium metal, or no intermediate diffusion layer is required. After welding, carefully clean the joint surface.

If argon arc welding is used to weld copper and titanium, the selection of cerium tungsten electrodes can improve the welding quality and benefit human health. For example, when welding copper alloy (QCr0.5) and titanium alloy (TC2), niobium can be used as the transition layer material, and the purity of argon gas is 99.8% to obtain high-quality joints.