Page 33 - MetalForming-May-2018-issue

Welding Well
By Doug Smith
When It Comes to GMAW, Why Ask Why?
What started out as an interview with a trio of Esab engineers for a technical article, recently turned into a thought-provoking dis- cussion. The topic: pulsed gas-metal- arc welding (GMAW ). The group agreed that pulsed GMAW provides fabricators using aluminum, stainless steel and heat-sensitive alloys with more control options than short-circuit and spray- transfer processes. However, when asked, “What about using pulsed GMAW for welding thinner sections of mild- carbon steel?” the conversation changed.
“Why would you want to use pulsed GMAW in the first place? Why was pulsed GMAW even developed?” asked Jay Ginder, senior application engineer, who was reminded that it reduces filler- metal costs by enabling use of the next- larger wire and use of one wire diam- eter for different workpiece thicknesses.
“I can see a high-volume manufac- turer doing that,” volunteered Jeff Lipko, development engineer, “but why else should a shop invest in the type of equipment necessary to switch from short-circuit to pulsed GMAW?” He then answered his own question: “Well, it does allow fabricators to weld out- of-position.”
“Good point, but for thinner mate- rials, short circuit probably makes more sense. Besides, we started out talking about control,” offered Nathan Lott, Esab applications engineer. “What about the additional pulsing controls
Doug Smith, product business manager--arc equipment, ESAB Weld- ing & Cutting Products, shares his arc-welding insights in MetalForming magazine’s new Welding Well column every-other month.
Doug Smith
Product Business Manager- Arc Equipment, ESAB Welding & Cutting Products
dsmith@esab.com
Ever wonder
why whelpers are 1⁄2 in.
thick? It’s to help cut the wire to a length that promotes good arc starts.
that can help operators achieve desired results, such as reducing spatter?”
Crisis in Progress?
Here’s where the discussion went sideways.
“If operators these days understood basics, spatter would be less of an issue,” countered Ginder. “Just because someone can pull a GMAW gun trigger doesn’t make him a welder.”
The group agreed that the techni- cal-education crisis goes beyond the need for more skilled tradespeople, with many students overlooking the need to equip themselves with funda- mental skills, knowledge and inquiring minds.
“If you can find a problem solver, a thinker and a researcher, you’ve got the making of a good welder,” said Lipko. “The problem is, I see kids who have trouble finding 15⁄16 in. on a tape measure or figuring out the diameter of a pipe.”
The issue extends to industry as well, especially for companies that rely on institutional knowledge that creates we’ve-always-done-it-this-way men- talities. Examples cited by the group include a structural-steel shop where 90 percent of the operators pushed a gas-shielded flux-cored wire when welding in the flat position. Employees there never wondered if dragging the
Operators need to ask fundamental questions such as, “Why are gun angle and travel direction so critical?”
gun would reduce slag inclusions. Another example includes choosing a smaller wire diameter because it’s eas- ier to weld with (because of its slower deposition rates), yet requires excessive manipulation to achieve good sidewall fusion. Using a larger wire that catches both sides of the joint with no manip- ulation could produce more consistent results. Welding faster with a larger wire also reduces heat input.
“Good welds result when operators understand gun mechanics and weld- ing principles,” added Grinder. “But since you asked my opinion, basic short-circuit GMAW can be a good choice for thin steel-fabrication. That is, when operators understand the fundamentals.”
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