CMT (Cold Metal Transfer) Welding

CMT (Cold Metal Transfer) Welding

Cold Metal Transfer welding is a modified MIG welding process based on short-circuiting transfer process.

This process differs from MIG/MAG welding process only by the type of mechanical droplet cutting method not previously encountered.

During welding, temperature variations in welds and parent metals have important effects on material characteristics, residual stresses as well as on dimensional and shape accuracy of welded products.

Cold Metal Transfer provides controlled method of material deposition and low thermal input by incorporating an innovative wire feed system coupled with high-speed digital control.

The wire feed rate and the cycle arcing phase are controlled to realise sufficient energy to melt both the base material and a globule of filler wire.

There are two main features of the CMT process: one is at the point of short circuit with low current corresponding to a low heat input, another is the short circuit occurrence in a stable controlled manner.

The big difference is in the wire feed. Rather than continuously moving forward into the weld pool, with CMT the wire is retracted the instant current flows. That breaks the arc. The metal droplet detaches from the filler and fuses with the – still molten – base metal. Then the wire moves forward to create another arc, and all this happens many times each second.

The difference from conventional MIG welding is fairly subtle, although it needs a lot of sophisticated control technology. The benefit is that it reduces heat input significantly. The developer of CMT welding, describes it as, “Hot, cold, hot, cold, hot cold.”

CMT-Cold-Metal-Transfer-Welding

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