Lincoln Electric 355M Manuel d'utilisateur télécharger pdf (Page 30)

OPERATION

B-8 B-8

POWER WAVE 355M/405M

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SPECIAL WELDING PROCESSES

AVAILABLE ON THIS MACHINE

PULSE WELDING (GMAW-P)

The pulsed-arc process is, by definition, a spray trans-

fer process wherein spray transfer occurs in pulses at

regularly spaced intervals. In the time between pulses,

the welding current is reduced and no metal transfer

occurs.

Pulsed-arc transfer is obtained by operating a power

source between low and high current levels. The high

current level or “pulse” forces an electrode drop to the

workpiece. The low current level or “background” main-

tains the arc between pulses. (See Figure B.3).

FIGURE B.3

PEAK AMPS

FREQUENCY

SPRAY TRANSITION

CURRENT

EACH PULSE DELIVERS ONE DROPLET OF WELD MATERIAL

Pulsed MIG is an advanced form of welding that takes

the best of all the other forms of transfer while mini-

mizing or eliminating their disadvantages. Unlike short

circuit, pulsed MIG does not create spatter or run the

risk of cold lapping. The welding positions in pulsed

MIG are not limited as they are with globular or spray

and its wire use is definitely more efficient. Unlike the

spray arc process, pulsing offers controlled heat input

that allows better welding on thin materials. Pulsing

allows for lower wire feed speeds which leads to less

distortion and improved overall quality and appear-

ance. This is especially important with stainless, nick-

el and other alloys that are sensitive to heat input.

In GMAW-P mode, arc control adjusts the background

current and frequency of the wave. When arc control

goes up, the frequency increases thus increasing the

droplet transfer.

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Lincoln Electric 355M Manuel d'utilisateur Page 30