In my research work i welded dissimilar aluminum joint.. got tunnel like formation when tool angle increases. What is the reason? Is it improper heat generation or improper plunge force?
can you explain this type of defect in more details so I can help you?
Hello Ahmed.. My research work is dissimilar welding of aluminium 6063 & 7075 plates of 6 mm thickness by friction stir welding process.. In that I take tool angle as one of the parameter... During experimental run I found tunnel like formation(huge void like) in the welded zone.. Wat is the reason for this??? Improper heat generation or due to improper tool plunge force ah... Unless all these due to any distinguished properties of materials ah???
Non homogeneous mixing of dissimilar alloys may be the reason for that because their is difference in thermal conductivities.
Hello Ahmed,
reasons for worm holes could be less heat input from tool. You can increase your axial force or tilt, increase your tool diameter or change the tool configuration. The easiest way is to decrease the traveling speed / increase your rpm, I welded 7xxx series quite slower then 6xxx series.
Hello RENE,
in my research work 6xxx series plate is weld with the 7xxx series.. for my experimental run i kept tool speed is maximum and travelling speed minium...and also kept tool speed and tool travelling speed as a constant variable... got good weld strength when the tool angle decreases.. do you think tool pin dia an important factor for weld strength?? may be increase in tool pin dia a reason for tunnel like formation (huge void formation)....
Hello Yuva,
i think your right. But it depends on the relation between shoulder and probe diameter and the features regarding the sheet thickness. Its not easy to discuss about welding parameter, without any information about the tool. What geometry and parameter do you use?
(i) what is the status of flash formation? (ii) I believe the the void may be due to the lack of forging action.
if flash formation is not there you can go for increase in plunge depth. you can also try to increase shoulder diameter and tool tilt both.
hello Yuva
i think if you decrease welding speed ( to increase temperature) and increase plunge force, you can overcome this drawback.
and from my previous experiments on dissimilar fsw, if the temperature of process is OK, pay attention to pin geometry and pin profile. for example in some FSWed joints, quadrangular pin is much better than Cylindrical one(because of pulse creation in mixing procedure)
any way, the extrusion of material is imperfect.
Hello Mohammed,
my research work is dissimilar friction stir welding of aluminium 6XXX and 7XXX.. in this most of error due to increase in pin angle.. some errors observed during increase tool pin dia.. is this two factors play a vital role in tool parameters or some other parameters there to follow? for improving the tensile strength of the material? and also i done my research work in vertical milling machine.. and the machine is not a modernized one.. is the machine vibration affect weld strength? any research work carried out regarding effect of vibration in weld strength (FSW)?
The tunnel that you have mentioned in your question is a defect in friction stir welding process. Most of the available literature comment that tunnel defect can be due to mostly improper stirring of the material around the tool. Since your case is of dissimilar materials, improper material mixing is also possible. Few suggestions that might help you to overcome this defect (but not guaranteed!)
1. Select the proper range of welding parameters specially the tool tilt angle. This is very essential as all these will govern the rate of heat generation during welding.
2. Try to go for more plunging if possible and more plunging force.
3. Check the dimension of your tool pin. If the pin length is not sufficient, you might experience the same.
4. Try to go for some offset. Add few millimeter offset towards the material which is harder or have high melting point so heat generated would be more towards that side.
5. Try to go for more dwell period.
tunneling defect in FSW could mainly be due to inadequate heat generation or inadequate plunge force. If the surface of the tunnel is open forming a groove like opening, then, the most probable reason could be inadequate tool plunge. If sufficient flash is being generated, then, try increasing the tool rotation speed. I had a similar problem while welding AA 2024-7075 in lap configuration. the problem was solved by increasing both the rotation speed as well as tool travel speed and reducing the tool tilt
http://www.tandfonline.com/doi/full/10.1080/10426914.2015.1025971?scroll=top&needAccess=true
you can refer above link for answer
- Badges
- Science topic