Common problems of headlamps when welding

(1) The oxidation compatibility of metals used in headlamps is poor. The mutual solubility of titanium and aluminum is small. The solubility of titanium in aluminum is 0.26%-0.28% at 665°C. When the temperature drops to 20°C, the solubility of titanium in aluminum drops to 0.07%, making it difficult for the two metals to fuse. Aluminum has a lower solubility in titanium, making it difficult to fuse two metals to form a solid solution weld.


(2) The oxidation of the metal used in the production of headlamps. Both titanium and aluminum are easily oxidized and hinder the bonding of the interface. Titanium begins to oxidize to form TiO2 at 600°C, forming an intermediate brittle layer on the weld and the interface. The dense oxide film Al2O3 formed on the surface of aluminum and aluminum alloy hinders the combination of the two metals, and the weld is easily mixed, which increases the brittleness of the weld. .


(3) Stomatal problem. The solubility of hydrogen in titanium is very large, and it is easy to accumulate to form pores at low temperature, which reduces the plasticity and toughness of the weld and causes embrittlement. Liquid aluminum can dissolve a large amount of hydrogen, but it hardly dissolves in solid state, which reduces the quality of welded joints.


(4) The problem of oxidized brittle phase. Titanium and aluminum react at 1460°C to form TiAl-type intermetallic compounds; at 1340°C, they react to form Ti3Al-type intermetallic compounds. Titanium reacts with nitrogen to form brittle nitrides. Titanium and carbon react to form carbides. When the carbon content is greater than 0.28%, the weldability is significantly deteriorated. The presence of these compounds reduces the plasticity and strength of the weld.

(5) Welding distortion problem. The thermal conductivity and linear expansion coefficient of titanium and aluminum are very different, resulting in relatively large welding deformation. Under the joint action of welding stress and brittle structure, cracks are prone to occur.