How to MIG weld square tube with flat plate

Square tubing by using a welding process always has been a matter of interest and importance to manufacturing and fabrication industries. Here is the demonstration on ‘How to join a sqaure tube with a flat plate, using the Metal Inert Gas (MIG) welding process?’ As MIG process is easy to operate as compared to other types of arc process and you can create many futuristic things by this square tube to plate weld joint for your school projects. So it is important to learn about the MIG square tubing basics.

In this case you are going to weld edges of square tube to a flat plate. On absorption of heat, thin edges may melt more quickly than sides of tube.  Keep the MIG gun at such an angle that will direct more heat to the flat plate rather than to edges of tube. Remember to weld tacks on all sides in order to prevent the assembly out of order. Listed below are the critical points that need to know about MIG welding in such kind of joints.

  • T-joint
  • Clamping
  • Tacking
  • Weld Run

1. T-joint Assembly

Assembly of square tube with flat plate gives T-joint. So you have to deal with the fillet weld. In other words edges of square tube are welded with the flat surface of plates. Align the square tube with plate according to the required dimensions.
2. Clamping
Before tacking, clamping is an essential part to prevent any disorder in assembly. So fair clamping is required with the acceptable force. Commonly it is done by some sort of tool or manually by a welder. Clamp the assembly for tacking.


Tacking is followed by clamping. Once you are successful to fix the assembly in shape, next step is to tack the joints at the middle. It is noticeable that tacking must be at opposite sides. Tacking on adjacent corners or sides may lead to warpage or any distortion.

4. Weld Run

It is usual practice to commence and pause welding at joint surface. Try to lay weld beads from the middle rather than corners. As corners offer weak linkage that turned into the possibility of cracking due to stress. Weld it around the corner to get a continuous weld run. If you don’t make it around the corner, it may result in a blow hole at the edge of square tube.

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