what is butt joint in welding

3.Stitch welding
Talking about the stitch welding, as the name indicates the welding is done in a stitching manner.just see the pic, they are used for connecting long welds where continues welds are not needed, it's simply implemented to reduce the cost of welding
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And about fillet welding they are used for welding pipes and welding cross sections of infrastructure, and when fastening metal by bolts isn't strong enough and wear off easily