MIG Welding: Mild Steel Basics
MIG welding (Metal Inert Gas, also known as gas metal arc welding or GMAW) is the most commonly used metal welding technique in the world – it’s fast, inexpensive, and even amateur welders can quickly learn to produce quality work.
Simply put, MIG welding is an arc welding process in which a continuous solid wire electrode is fed through a welding gun and into the weld pool, joining the two base materials together (think of it as a more advanced version of a hot glue gun, but for metal).
The MIG process enables a DIY welder to make, maintain and repair welds on material ranging from 24-gauge up to 1/2-inch thick. With a little practice and some good advice, you can become a competent MIG welder, able to do everything from repairing furniture to building an outdoor fireplace.
Here are some MIG welding basics to get you started.
Safety first
- Always wear proper welding safety apparel and supplies, which includes leather shoes or boots, full-length pants, a flame-resistant long-sleeve jacket, leather gloves, a welding helmet, safety glasses and a bandana or skull cap to protect your head from sparks.
- Remove any potential fire hazards from the welding area.
Preparing the metal
- Use a metal brush or grinder to remove rust and surface contaminants from the metal prior to welding; get clean down to bare metal
- Make sure your work clamp connects to clean metal; any electrical impedance will affect wire feeding performance.
- On thicker metal – and especially on butt joints – bevel the joint to ensure the weld fully penetrates to the base metal.
Preparing your equipment
- Thorough check of your power source, gun and gas cylinders prior to starting any MIG welding project.
- Make sure all cable connections are secure and free of damage.
- MIG welding requires DC electrode positive, or reverse polarity. Set your equipment accordingly.
- Set the shielding gas flow rate to 20 to 25 cubic feet per hour. If you spot a leak in your hose, replace it immediately.
- Adjust tension in the drive rolls and wire spool hub; inadequate tension can lead to poor wire feeding performance.
- Remove excess spatter from contact tubes, replace worn contact tips and liners and discard the wire if they are rusty.
Choosing wire
- Use ER70S-3 for all-purpose welding; use ER70S-6 wire when welding on dirty or rusty steel.
- .030-inch diameter wire is good for a range of metal thicknesses and applications; for thinner material, use a .023-inch wire to reduce heat input. For thicker material, use .035 or .045 inch.
Choosing a shielding gas mix
- A 75 percent argon/25 percent carbon dioxide blend (75/25 or C25) works well as an all-purpose shielding gas for carbon steel. A 100 percent CO2 gas provides deeper penetration, but also increases spatter and makes for a rougher bead.
Select voltage and amperage
- The electrical settings a weld requires depend on a range of variables, including metal thicknesses and type, type of joint, welding position, shielding gas and wire diameter and speed (among others). Do your research and fine-tune the welding arc to your personal preferences.
Wire stick-out
- The proper wire stick-out for most solid wire MIG applications is about 3/8”; try to maintain this length while welding. Tip: listen for a sound like sizzling bacon – if the arc sounds irregular, your stick-out is probably too long.
Push vs. pull
- When MIG welding mild steel, you can use either the push or pull technique, but remember that pushing usually offers a better view and enables you to better direct wire into the joint.
Travel angle
- Normal welding conditions in all positions call for a travel angle of five to 15 degrees. Greater angles tend to lead to more spatter, less penetration and arc instability.
Work angle and position
- Work angle and gun position varies with each welding position and joint configuration. For a helpful primer on flat, horizontal, horizontal, vertical and overhead welding tips, check out this video.
Practice!
- Most people can create good looking, high-quality MIG welds with a little practice. When you’re learning how to weld, take note of what you did right and what looks wrong.
Need welding machines, welding machine repairs, or welding supplies in western North Carolina? We’ve got ‘em here at James Oxygen. From MIG, TIG, and plasma cutting equipment to welding safety gear for you and your team, James O2 has it all. Contact us today to learn more!