Joining of thick material by using a welding process, always has been a major concern in fabrication industries. Here are some important points that are needed to know about the structural welding of thicker pates using Metal Inert Gas (MIG) process. Below listed are the primary concerns in thick plate MIG welding.
- MIG Welder Chart
- Bevel Edge Joint
- Trained Welding associates
- Multi-pass Structural Welding
You know there are four common transfer modes in MIG welding viz; Spray transfer, globular transfer, Short circuiting, and Pulse transfer. But here we will discuss only Short Circuiting transfer mode.
- He must know how to configure the welding equipment and tackle the problems accordingly.
- He should have good experience on MIG welding.
- He must be aware of all welding imperfections which may happen during process.
First assemble the plates according to required shape by tacking. Commence welding from the initial point for root pass. Run it in ‘side to side manner’ as you have to deal with the sides of plates. All you have to do, is to make sure the complete penetration and fusion of each weld pass. On the other hand too little stick out can cause the MIG gun to hit with the plate. Extend the electrode to some suitable length. Pre-heating and cleaning are major keys for sound welding. Try to make beads in such a way that they have a continuous weld look (proper blending). In other words beads must melt and fuse with each other. But if beads looks separately from each other, there will be lack of fusion. So in this case, you need to overlap these beads such that they have complete fusion with one another. See How to prevent Lack of Fusion in weldment?
- Short circuit transfer mode is the recommended method for structural MIG welding of thick plates.
- Bevel edge joint gives successful results for multi-pass MIG welding of thicker plates.
- Pre-heating and Pre-cleaning is an essential part, in achieving quality weld results. For structural multi pass MIG welding, suitable composition of shielding gases is required.
- Welding personnel must have good experience and skills to tackle the problems. He must keep an eye on the common weld defect which is the “lack of fusion” in this case.