Lasers are now established as industrial tool that cut, weld, drill and modify the surface properties of materials. In the applications, laser welding has the advantage of high welding speed and provides low heat distortion.
Thus, laser welding is a very attractive process for joining thin steel sheets and surface treated steel sheet. Recently Nd:YAG laser is applied to welding of the car body as light weight construction. And lap joint is generally used for joining two thin plates due to groove accuracy.
The major item in market for surface treated steel sheet is zinc coated steel. However, the laser welding of zinc coated steel is very difficult because of its low boiling point. Compared with zinc, on the other hand,aluminum has a high boiling point. Thus, laser weldability of aluminized steel is superior to that of zinc coated steel. Moreover aluminized steel has a excellent heat resistance, thermal reflection and corrosion resistance.
The results of laser weldability of the aluminized steel for the full penetration welding will be described in this paper. We focused on the investigation of the phenomenons caused by aluminum and behavior of aluminum in weld.
Therefore, we have been carrying out experiments with these objectives by Nd:YAG laser. The effects of parameters such as welding/Al coating condition and types of the shield gases were investigated in the bead shape and cross-section in lap welding. At the same time, we were going to evaluate the Al contents that were mixed in weld after laser welding and investigate a correlation between the mixed Al and mechanical properties.
On the other hand, intermetallic compounds on Fe-Al system have been reported that it's mechanical property is very brittle and broken easily. So we observed Al-rich zone which has very high hardness and investigated exist of intermetallic compounds.
At the same time, we were going to compare the weldability of the aluminized steel sheet with aluminized stainless steel sheet for fuel cell.
Although there is a difference between the basemetal of the low carbon steel and stainless steel, it is interpreted that a behavior of Al element in the weld is similar to them.