Friday, September 4, 2015

Mig Welding Basics that Your Welders Must Master (Part 1)

Below are important Mig welding basics that welders must grasp as tightly as possible.

Helpful information for those who are interested in:

Mig welding is the most popularly used of the arc welding processes, suited for everything from small fabrications, repairs to large structures, shipbuilding, and robotic welding. Mig can be applied in a wide range of materials and thicknesses. Importantly, your Mig welders grasp those Mig welding basics to serve well their work, and refine their skills in this widely used welding process to produce more qualified welds and further their career. 

What is Mig welding?

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Mig (Metal Inert Gas) is also referred to as GMAW (Gas Metal Arc Welding). This is the most widely welding process in the world for various reasons. It is fast, cost effective and welders can be easily trained to create quality work.

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Gas or flux

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The welding process creates extreme amounts of heat that breakdown chemicals in the air into smaller molecules. Those substances then can contaminate the weld. 

The process generates a small electromagnetic field, which can also contaminate the weld. Weld contamination may (not) be visible to naked eye after the weld is finished. That’s why the weld can fail or show failure signs at a later time. Welders have 2 options to control contamination – use a flux core wire or use gas.

Using gas requires welders first source a welding supply or gas supply house for proper mix of gas provided, which is commonly a mix of CO2 and Argon for Mig welding carbon steel (also, mild steel).

Flux core welding wire includes a shielding substance for weld protection. Better portability is the advantage here, because there is no heavy gas rank to drag around with the welder. The disadvantage is the mess, since flux core welding often leave more spatter.  

Mig welding on mild steel and on aluminum

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Mig welding can be applied for most types of metals – steel, stainless steel, and aluminum. Still, welding aluminum is far from similar to welding mild steel, as aluminum is different from steel. Then when welding aluminum, welders have to use other settings and other parameters. For instance, as aluminum has lower melting temperature than mild steel, welders should use a higher local heat input but faster welding speed than with steel for good fusion and penetration. The welding sets would automatically adjust welding parameters, then the welder can focus on the welding operation, movement of welding gun and weld pool.

The machined-controlled parameters are, for instance, wire feed speed, arc voltage, gas consumption, wire diameter. Still, even if they are machine controlled, welders have to feed them into machine before starting to weld. During the welding process, the welding set can adjust relationship between those parameters. If they are set correctly, welders just have to focus on length of stick-out, angle of welding gun and welding speed. Then in many ways, Mig welding process is easier than metal arc welding.

Mig welding can be used with numerous metals, but there are some differences that welders should beware. Mig welding on mild steel and aluminum is a good example. The biggest differences between those 2 welding methods are choosing shielding gas and levels of ampere and voltages. Also, of course, the method used for metal transfer. Types of transfer can be listed as spray arc transfer, pulsed transfer, and dip transfer (also, short arc).

The spray arc transfer has higher arc voltage and amperage that short arc transfer. It is typically used on materials of different properties and thicknesses.

Shielding gas is chosen depending on metals to be welded. When welding aluminum, welders often use a mixture of argon and helium, or argon. Meanwhile, welding steel needs CO2. 

One problem with welding aluminum is to be able to see whether the weld you are doing will be right. Often, this problem can be handled by watching the welding pool. You can see from the material penetration, and from the weld flow, whether the welded joint is Ok or not. You can see whether the amperage and voltage levels are set right, or if the amperage is too low. That is something you can learn from experience.

One of most significant factors when welding is the current level. Without the current right, welders can make mistakes when Mig welding aluminum than when welding with coated electrodes. It is also important to clean the prepared joints. They can be cleaned with stainless steel wire brush, cleaning fluid. The fluid is, indeed, alcohol. It smells terrible. Still, welders can use welding masks with fresh air supply and use them when cleaning and welding. 

For those who may concern about:

Safety first

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Mig welding has very specific safety issues as compared with other processes. Following is basic safety equipment needed:

Welding helmet with the shade 10 or 11 lens reliant on the voltage welded with for eye protection from UV radiation.
Safety glasses to protect welder’s eyes from sparks as well as flying spatter from cleaning the weld.
Leather gloves to insulate the welder from electric shock and burns from sparks and heat. In some cases, welding gloves come with a reflective coating to tackle the head of welding heavy plate.
Long pants and sleeves made of cotton, leather or fire retardant material to protect the welder’s skin from UV rays as well as hot metals. Good sun block also helps the skin areas without clothing.
Leather booths to protect the welder’s feet from sparks and molten metals that will fall.
Good ventilation to get rid of shielding gasses but not take them away from the weld area.

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