I think left hand threaded tool pin geometry give best results for this. You can also used plain conical or square tool pin profile. Your tool pin diameter will be depends on your plate thickness and tool shoulder to plate thickness ratio should be within 3 to 6.

thank you

i used a threaded pin geoletry and i kept the shoulder diameter to plate thikness ration at 3 , but i obtained a joints with tunnel default.

Hi

when you observe wormhole or tunnel defect in the weld nugget zone, it's related to welding parameters such as rotational and traverse speeds. it should noticed that the weld pitch ( ratio of traverse/rotational speed) always be < 0.1. this defect occurs because of low stirring due to low heat produced by tool. so you can increase rotational speed and decrease traverse speed. it might help you.

good luck!

The cylindrical threaded pin geometry with probably 3-4 mm pin dia..........shoulder dia. shuld be selected considering speed of rotation, travel speed and thickness of your material.......i would suggest sliw speed and feed for soft alloys.....all the best

Increase in rotational speed and decrease in traverse speed eliminates the worm hole defect as pointed out earlier. However, an increase in plunge depth along with these also helps in removing defect

As is known on the coefficient of friction have many parameters. One of the significant parameters is the type of materials in mutual contact, roughness, grain size, the type of heat treatment, methods of surface treatments, etc. In order to select a suitable mode of welding is required to know what is the type of the weld? What structural, mechanical and thermal changes would occur after the regime of welding.

For more information, see the following articles:

https://www.jim.or.jp/journal/e/pdf3/47/07/1743.pdf

http://link.springer.com/article/10.1023%2FB%3AJMSC.0000013922.16079.d3?LI=true#page-1

 http://ac.els-cdn.com/S2214914713000147/1-s2.0-S2214914713000147-main.pdf?_tid=05f7096e-aa1d-11e5-a9d8-00000aacb361&acdnat=1450947913_bdb2cb6402dce0267c066ec74dfa4325

 http://www.sciencedirect.com/science/article/pii/S0921509306018934

 http://link.springer.com/article/10.1007/s11661-006-1085-8#page-1

 https://www.jstage.jst.go.jp/article/matertrans/43/10/43_10_2554/_article

 http://www.sciencedirect.com/science/article/pii/S1359646202000945

 http://www.sciencedirect.com/science/article/pii/S1359646206006932

 http://www.sciencedirect.com/science/article/pii/S0924013606007400

thank you

Dear Khawla,

In the case of joining AZ31 Mg alloy components, since it is a relatively soft material (in comparison to most Aluminium alloys), you need to be very careful with your selection of welding parameters (specifically the downward process force normal to the surface). As far as pin geometries, a standard tri-flute that doesn't have a very aggressive pitch should do the job. 

Regards,

Samir