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Jumat, 09 Januari 2009

Examining Pulsed MIG (GMAW-P) Welding

A brief listing of advantages provided by pulsed MIG welding (GMAW-P) usually encourages welding technicians to see if this technology may be appropriate for their application:

* All position welding with spray-like transfer
* Travel speeds increase up to 35% over short circuit transfer
* Ability to fine tune arc wave form
* Significantly reduced spatter compared to short circuit transfer
* Minimizes distortion - compared to spray transfer
* Better bead appearance
* Lower fume emissions, when properly set up

While this process offers many advantages, it's important to evaluate your application carefully before making a move to pulsed MIG. Applications best suited for GMAW-P are those currently using short circuit transfer method for welding 14 gauge (1.8 mm) to 3/8 in. (9.5 mm) steel, either manual or automated. In these situations, GMAW-P notably increases production rates, significantly reduces spatter and improves bead appearance.
The ability to tailor the arc wave form with pulsed spray transfer lets users develop beads with improved width-to-depth ratios. For example, some people use pulsed spray transfer for the fill (and even root) passes on pipe welds because they can create a penetrating arc that produces an x-ray quality weld. Others use pulsed spray transfer for overlay work (such as a nickel or inconel jacket) because they can create a wide, flat bead that results in minimal metal dilution.

The pulsing action also reduces heat input by 20 to 80 amps compared to spray transfer. This produces less distortion and a smaller heat affected zone (HAZ). One application for pulsed spray transfer is for making critical welds on the high strength steel (HY80, HY100) used for submarine hulls, where mechanical properties cannot be degraded by excess heat.

Pulsed spray transfer permits out of position welding because there is no metal transfer during a portion of the cycle, thus giving the weld puddle a chance to freeze slightly. One company welding stainless steel switched from running flux cored wire to using solid wire with pulsed spray transfer. This allowed them to maintain high speeds in the flat position and weld in the vertical up position. The company was able to recoup its investment in the new pulsed welding equipment in four months by switching from flux cored to solid wire.

Pulsed spray GMAW is not a cure-all for every welding problem, nor can it provide all of the benefits mentioned above for every application. To determine if GMAW-P is right for you, work closely with your Miller distributor. Be sure to perform cost studies, develop welding procedures, and conduct trial runs to determine the feasibility of the process for your application.

GMAW-P is a modified spray transfer process that produces minimal spatter because the wire does not touch the weld puddle (with short circuit transfer, the wire touches the weld puddle approximately 180 - 220 times per second, creating spatter). In addition, pulsed spray transfer results in a more fluid weld puddle that wets out better. This produces better bead appearance, and it also permits higher travel speed.
source : http://www.welding.com/articles/bparticle7.htm

1 komentar:

  1. Looks amazing!!!! /I look forward to your feedback /thanks for this man it was very helpful.

    Welding Equipment