Novel joining techniques
In recent years the Japanese automotive industry has introduced substantial amounts of stainless steel into their production however the European automotive industry have not.
For this reason this project will investigate novel processes for joining high strength stainless steel grades to zinc coated mild steel which can be easily transferred and integrated cost effectively into current automotive manufacture.
Recent developments have been made to introduce new welding processes into the automotive industry. Two of the most recent methods are Laser hybrid welding and Cold Metal Transfer welding (CMT). Both of these welding processes will be involved in this project and compared to traditional methods of welding such as resistance spot welding, laser and MIG welding.
Laser Hybrid Welding
Laser Hybrid Welding is defined as the coupling of laser beam welding with a conventional welding process eg Gas Metal Arc Welding (GMAW). Laser hybrid welding was first introduced in the seventies, however it was not until recently that the process of LHW was suggested and investigated for use within the automotive industry.
The advantages of Laser Hybrid welding are
- deep penetration
- high processing speeds
- good tolerance to joint fit up
- low heat input
- good quality welds
- no undercut
Cold Metal Transfer (CMT)
Cold Metal Transfer (CMT) is essentially a gas metal arc welding process with a significantly lower heat input when compared with conventional dip arc processes.
'Cold' is a relative term in this process and its based on controlling the dip transfer of the arc. In the CMT process the wire is not only fed towards, but also withdrawn from the work piece giving an oscillating wire, giving lower current with an average frequency of 70Hz.
Advantages of the CMT process include
- spatter free welding
- minimal post weld work
- reduced heat input
- good gap bridge ability