Spatter-free welding - even manually!

The familiar acronym CMT (Cold Metal Transfer) can now also be used in manual welding, achieving improved manual welding productivity and quality

This has been demonstrated on a pilot application at Alstom LHB in Salzgitter.

Innovative technology from Fronius allowed the renowned manufacturer of rail vehicles to impress its own employees as well as its customers.

Passing on the comments of his colleagues, Thomas Richardt, steel construction foreman at Alstom, says "our welders are really keen on this, as they no longer need to clean up afterwards".

The rail vehicle specialist built a prototype wagon to demonstrate the new welding technology to its customers.

The result was a pleasant surprise for all concerned.

The absence of spatter is a feature that becomes apparent particularly after painting the delicate, rustproof steel sheets.

The low level of heat input also means less deformation, especially of thin sheets.

CMT Manual is a variant of the automated CMT welding process, which has now been impressing welders and customers alike for a good two years.

The main features are identical: reversal of the wire movement, which is integrated into the digital process control, greatly reduced heat input, and spatter-free material transfer.

Reversal of the wire movement means that the welding filler wire moves backwards and forwards inside the torch more than 70 times a second.

The clever digital process control "detects" a short circuit and facilitates droplet detachment by withdrawing the wire.

The resulting material transfer takes place with virtually no accompanying current; this, coupled with the broken arc, produces the typical "hot-cold-hot-cold" pattern in a 70 Hz cycle.

Heat is applied to the metal during the short burn phase (hot).

In the retract phase (cold), precisely one drop enters the resulting weld seam or weld pool.

Result: no spatter, less rework, no weld pool, less deformation and improved gap bridgeability.

The welders in Salzgitter are particularly pleased that the tedious job of "removing welding spatter and smoothing down surfaces" is no longer required.

Their work primarily involves the butt welding of Bekinox E13 "stainless steel" (material no.

1.4316), with the torch in a forwardinclined/backward-inclined or neutral position.

The TransPuls Synergic 3200 CMT welding system feeds the filler wire at 5.5 m/min, delivering 11 V and 100 A for this application.

The basic characteristics for both normal and pulse welding in synergic mode likewise originated from Fronius.

Externally, the CMT Manual system differs only in its Pull-Mig torch with integral motors for wirefeeding and the wire buffer integrated into the hosepack.

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