Intro To Basic Gas Metal Arc Welding

GMAW: Gas Metal Arc Welding Also known as MIG and wire feed welding Best suited for high volume production welding Has a higher current density at the welding electrode than SMAW Unique because it has a continuously fed electrode Most productive welding process Also known as MIG and wire feed welding (Metal Inert Gas) Aluminum and magnesium are typical when only an inert gas is used. When only Carbon Dioxide is used, manipulation of the welding gun is necessary. Also known as MAG (Metal Active Gas) Carbon steel and stainless-steel welding when carbon dioxide ands or/oxygen is added to the inert gas.

Manipulation methods: Can be welding by pushing or pulling the welding gun 3/16” or thinner Push Thicker than 3/16” Pull (Deeper penetration) Manipulation methods: Zig zag Step back Semi circle Drag Circle (typically on thin materials like 16 gauge and pushing the gun is recommended) Do not Circle on thick materials because it creates “cold lap” (When circling, always push your puddle up)

Gun Angle Variables Always start with a short “stick out” 10 – 20 degrees for pushing or pulling is typical. (We will use 15-20) Variables Always start with a short “stick out” ¼” – 3/8” to avoid cold start When you start with a long wire sticking out, you decrease you are decreasing your amps…leaving a cold start. Dictated by electrode type and diameter. Amperage and Voltage Work together Never change one drastically without the other. (Miller Weld Calculator) Increase or decrease in voltage effects amperage GMAW machine can make up some, but when you are outside the range, it can not. GMAW is constant voltage Voltage should stay consistent SMAW and GTAW are constant current Maintains amperage setting Large changes in voltage setting controls mode of metal transfer (type of arc)

Wire feed speed Electrode Selection Shielding Gas Voltage Setting Hold trigger for 6 seconds, measure the length of wire and multiply by 10. Also the Amperage setting Electrode Selection .035 is what we will be using Shielding Gas 75/25 (Argon/CO2) is what we will be using Voltage Setting Short circuit (what we will use) Wire makes contact with the metal Wire melts of thousands of times per second Globular Wire melts off in globules larger than diameter of wire and wire never makes contact with the material. (Not commonly used because the molten puddle is hard to control.) Spray Arc Wire melts of in tiny globs and the wire never comes in contact with the material Can be run with wire speeds at 500 IPM Arc burns hot enough welders often need heat deflectors on knuckles.

Other Cold Lap Consumable Shielding Gas Bead width 10x the diameter of the electrode (.035 x 10 = .350) Cold Lap Lack of fusion Consumable Wire is consumable and becomes the weld bead Shielding Gas Protects the molten puddle like the flux on a electrode for SMAW Pipe line is starting to use GMAW process more (tents over welding area) Electrode extension during the welding process Must maintain arc length 1/4 “ – ½” Ideal 3/8 “ Electrode angle Must be able to push and pull Advantages of GMAW High Productivity Fewer stops and starts (tie ins) Readily adaptable to automation

Weld #1 Disadvantages to GMAW “Cold lapping” or lack of fusion. Settings 18 volts, 220 amps Push pull