The Advantages of FSW

1. There is hardly any distortion or contraction resulting from welding heat.
2. There is hardly any discoloration of the welded section.
3. Welding rods and shielding gas are not required.
4. There is no spatter, no fumes, no ultraviolet rays.

(1)Temperature and Amount of Distortion of Welded Joints

The maximum temperature that FSW welds at is 480 degree Celsius, far lower than the 660detemperature of MIG (Metal Inert Gas) welding. The amount of distortion is only one twelfth of that in MIG welding. A comparison of the amount of distortion and contraction for the two welding methods is shown in Figure 2.

Figure 2 : The Amount of Distortion / Contraction in FSW and MIG Welding

Since FSW is based on the low-temperature-plastic-flow characteristics of aluminum, the required heat input is also low;consequently, the welding distortion and contraction are low.

(2)Strength and Reliability

FSW welds were shown to be equal to or better than MIG joints on tensile strength tests. All ruptures were in sections affected by the heat. FSW has better mechanical features than MIG welding because the welding temperature is lower, there is less distortion, and there are no flaws.

(3)Impact Strength

The results of Charpy Impact Test carried out at room temperature show that the impact strength of the joints welded by FSW is 1.7 times greater than that of the parent metal, and 2.4 times stronger than that of joints welded by MIG. The 'stirring' of the aluminum alloy during FSW gives it a finer micro-structure, which improves its resistance to impact. In contrast, structure, and in the post-extrusion parent material, a rougher micro-structure is formed as a result of re-crystallization and this columnar crystalline structure. The results of the Charpy Impact Tests are shown in Figure 3.

Figure 3 : Impact Strength of FSW and MIG Welds

Impact strength of joints welded by FSW is 1.7 times greater than that of the parent metal, and 2.4 times stronger than that of joints welded by MIG

• Features : FSW (Friction Stir Welding)