MIG Welding
Introduction
Gas metal arc welding, ), usually referred to by its subtypes metal inert gas (MIG), is a welding process in which an electric arc forms between a consumable MIG wire electrode which is usually a similar material that is fed from the MIG gun via a motor and pushed into the weld puddle and the workpiece metal(s), which heats the workpiece metal(s), causing them to fuse (melt and join).
Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination.
The typical GMAW welding gun has a number of key parts—a control switch, a contact tip, a power cable, a gas nozzle, an electrode conduit and liner, and a gas hose. The control switch, or trigger, when pressed by the operator, initiates the wire feed, electric power, and the shielding gas flow, causing an electric arc to be struck.
GMAW torch nozzle cutaway image:
- Torch handle
- Molded phenolic dielectric (shown in white) and threaded metal nut insert (yellow)
- Shielding gas diffuser
- Contact tip
- Nozzle output face
Welding is a hazardous profession that includes several risks from burns, radiation, shock, fire, and more, and MIG welding is not an exception. Even though the heat of an arc is not as high as with Stick welding, or there isn't too much spatter like with Flux core wire, you will want to keep yourself protected.
Welding helmet
When selecting a welding helmet, the viewing area is an essential component. Also called the field of vision, the viewing area is how much visibility you have from behind the lens.Welding hoods offer various viewing area sizes. What to look for depends on a few factors including your welding environment, the type of welding you do and your personal preference. Unlike TIG welding which a small viewing area can offer a better concentration for welding work. For beginners, welding helmet with a large viewing area is a good choice, for a larger viewing area provides a wider view of the arc, puddle, and workpiece. This makes it easier to see what you're welding and helps you to make as few moves as possible during a weld. At the same time, whether the helmet has an automatic darkening function should also be considered. Auto-darkening helmets provide dual defense function, protecting welding workers' eyes from ultraviolet and infrared radiation all the time. They’re also a good match for beginner welders because they don’t require the wearer to make many manual adjustments during the welding process.TECWELD Auto Darkening Welding Helmet Large Viewing Screen 3.94"X3.66" True Color Solar Power Auto Darkening Welding Helmet with 4 Premium Sensors is a popular option for MIG welding.
Welding gloves
Welding gloves with heat-resistant linings protect the welder’s hands from the high heat. 4.Welding jacket: Welding jackets made from fire-resistant material protect welders from high heat and metal splatter emitted during welding
Shielding gas
Shielding gas is an essential component of MIG welding processes. The primary purpose of shielding gas is to protect the weld pool from the influence of the atmosphere, i.e. from oxidation and nitrogen absorption, and to stabilize the electric arc. Shielding gases also influence the characteristics of the weld penetration profile. MIG welding typically uses a mix of 75% argon and 25% carbon dioxide, or 100% carbon dioxide. the choice between 75% argon and 25% carbon dioxide or 100% carbon dioxide depends on the welding project and personal preference. 75% argon and 25% carbon dioxide is a well-balanced gas for MIG welding that produces a nicer looking weld with less spatter, but it is more expensive. 100% carbon dioxide is cheaper but can produce a hotter arc with deeper penetration and can be more difficult to work with. There are other gases now used for different processes and materials, but these are less common in the average garage or workshop manufacturing process.
Welding wire
MIG welding wire is a consumable material used in MIG welding to join two pieces of metal together. The wire is made of metal, typically steel or aluminum, or they can have a copper coating and are spooled on a drum or coil. The wire is fed through a welding gun and then heated and melted by an electrical arc to join two pieces of metal together. MIG welding wire comes in different types, including solid wire and flux-cored wire. Solid wire is used for welding thinner materials and is generally less expensive than flux-cored wire. Flux-cored wire is used for welding thicker materials and is more expensive than solid wire. MIG welding wire is available in different materials, including mild steel, aluminum, and stainless steel. The type of material you are welding will determine the type of wire you need. MIG welding wire comes in different diameters, ranging from 0.023 inches to 0.045 inches. The diameter of the wire you need depends on the thickness of the material you are welding.
How to set a MIG welder
We have introduced the basic equipment required for MIG welding. Now we need to adjust the welding machine settings. Usually we will see these two settings on the welding machine: voltage and wire feed speed. They are important factors that affect the quality of welding.
Welding voltage
What is welding voltage? If amperage measures the volume of electrons flowing through an electrical current, voltage measures the pressure that allows them to flow. In other words, it's the carrying force of the electrical current. So, what effect does this electrical "pressure" (voltage) have on the weld? Welding voltage controls the arc length: the distance between the weld pool and the wire filler metal at the point of melting within the arc. As the voltage increases, the weld bead will flatten out, and its width-to-depth ratio will increase.
The influence of different voltage settings (14, 16, 18, 20, 22) on the weld bead while keeping the wire feed speed (310ipm) unchanged
Wire feed speed
Wire feed speed is an important variable in MIG welding that affects the quality and efficiency of the welding process.Wire feed speed (WFS) controls amperage and the amount of weld penetration. WFS and current are directly related: as one increases, so does the other and vice versa. If the WFS is set too high, it can lead to burn-through. That's because as the welding current increases, the weld penetrates deeper into the base material.
MIG welding technique is an important aspect of MIG welding that affects the quality and efficiency of the welding process.
Setting up your MIG welder as a beginner might be a difficult task since you'll need to adjust wire feed speed and voltage according to material thickness. Welding current or amperage in MIG welding is represented by wire feed speed, and the higher the setting, the more heat (penetration) you get inside the joint. The voltage affects the arc length, so you don't want it too high to let the wire stub into the workpiece or too low to let the wire fuse into the contact tip.
The issue with MIG welder settings is that each machine responds differently to input settings. That's why many MIG welders for beginners today, including the Tecweld SMIG-160EI Multi-Process MIG Welder, have synergic settings or auto-set features. When turned on, the welder automatically adjusts the WFS and voltage according to material thickness, so you let your welder do all the hard job for you.
Forehand Welding
Backhand Welding
Backhand Welding The gas or arc welding process in which the flame or arc moves in the direction opposite to the direction of the weld progression is called the backhand welding. It is also called pull welding or backward welding. In the backhand welding, the welding torch does not situate above the weld bead. In this welding process, the filler rod is also applied behind the welding torch as shown in Figure-2.
Source from: tutorialspoint
If you want to know more about flat welding, vertical welding and other welding positions, please jump to Different Welding Positions You Need To Know-MIG
