Dear Virkam,

Attached papers may be helpful.

Best Regards

Dear Vikram,

The choice of a friction stir welding tool (i.e. pin & shoulder) design depends firstly on the material of choice (along with the specific alloy), the thickness of material to be joined, its geometry (i.e. whether it is a linear weld, 2D path or complex 3D curve) and the type of joint (i.e. butt or overlap). 

The more commonly used pin shape for joining most Aluminium alloys in a butt joint configuration is a Tri-flute design where which has interspersed threaded & flat sections and is in the shape of a frustum of a cone. However while joining Aluminium to steel, it is preferred to use a non-changing diameter (i,e, a cylindrical or square shape) for the pin. 

Furthermore, when joining in an overlap configuration, one can also adopt patented scroll designs on the shoulder which would ensure less amount of a hooking effect. 

Regarding tool material (i.e. of the pin & shoulder), it is preferred to use a coated Tool steel (having reasonable hardness & strength of approx. 1000MPa UTS) for joining Aluminium alloys together. While joining steel to steel, you will need a ceramic such as PCBN, but you risk a fracture failure and short tool life. 

I hope this helps.

Regards,

Samir

Dear Vikram,

There are usually three kinds of materials for FSP: H13 hot-work steel, H13 with chromium coating, and Tungsten-Carbide. The choice is mainly depending on the material to be friction stir processed. For example, in the case of FSP of aluminum, H13 tool steel is feasible, but for FSP of steel or Titanium alloys, it is better to use harder tool, namely Tungsten-Carbide.

The geometry of FSP tool is mainly related to the dimension of base material as well as its material flow characteristics. The reviewing literature is the best way to select the ideal geometry.

Dear Vikram,

Selection of tool is mainly carried out considering the workpiece material you are intending to work on as for copper for my study double tempered H13 steel was effectively used. To the case of geometry of tool, the dimension and material flow characteristics of base metal has to be considered.

Refer

http://www.tandfonline.com/doi/full/10.1080/10426914.2017.1291952

http://www.sciencedirect.com/science/article/pii/S0921509317301582