MIG welding can be used for various metal types and thicknesses. However, welding different metal thicknesses requires some adjustments and techniques to ensure a strong and consistent weld. In this blog post, we will cover some tips and best practices for MIG welding different metal thicknesses, from thin sheet metal to thick structural steel.

I. What is MIG Welding?

MIG stands for Metal Inert Gas welding, also known as Gas Metal Arc Welding (GMAW). It is a welding process that uses a continuously fed wire electrode and a shielding gas to create an electric arc between the wire and the base metal. The arc melts the wire and the base metal, forming a weld pool that cools and solidifies into a weld bead.

MIG welding is fast, strong, versatile, and fairly easy to learn. It can be used for various metal types, such as carbon steel, stainless steel, aluminum, copper, etc. It can also be used for different metal thicknesses, from thin sheet metal to thick structural steel. However, each metal type and thickness requires different settings and techniques to achieve optimal results.

II. How to MIG Weld Thin Metal?

Thin metal is generally considered to be anything less than 3/16 inch (4.8 mm) thick. Welding thin metal can be challenging, as it is prone to warping, distortion, burn-through, and lack of penetration. To avoid these problems, here are some tips for MIG welding thin metal:

1. Use a smaller wire diameter. A smaller wire diameter will reduce the heat input and the amount of filler metal, which will help prevent burn-through and warping. A common wire diameter for thin metal is 0.023 inches (0.6 mm), but you can also use 0.030 inches (0.8 mm) or 0.035 inches (0.9 mm) depending on the metal thickness and type.
   

2. Use a lower voltage and wire feed speed. A lower voltage and wire feed speed will also reduce the heat input and the size of the weld pool, which will help prevent burn-through and distortion. A good starting point is to use the suggested settings on your welder’s chart, and then fine-tune them according to your results. You can also use a tool like a Power and wire speed calculator to estimate the initial settings for your welder.
   

3. Use a higher shielding gas flow rate. A higher shielding gas flow rate will provide better protection for the weld pool and prevent porosity and oxidation. A common shielding gas for thin metal is C25, which is a mix of 75% argon and 25% CO2. A good flow rate for thin metal is around 25-30 cubic feet per hour (CFH).
   

4. Use a shorter stick-out. Stick-out is the distance between the contact tip and the end of the wire. A shorter stick-out will provide better arc stability and control, which will help prevent spatter and lack of penetration. A good stick-out for thin metal is around 1/4 inch (6.4 mm) or less.
   

5. Use a push or forehand technique. A push or forehand technique means moving the torch in the same direction as the wire feed, or away from the weld pool. This technique will provide better visibility and penetration, as well as a flatter and narrower weld bead. A push technique is especially recommended for welding aluminum, as it will help prevent the formation of oxides on the weld pool.
   

6. Use a backstep or stitch technique. A backstep or stitch technique means moving the torch back and forth along the joint or making short welds with pauses in between. This technique will help reduce the heat input and the distortion, as well as allow the weld pool to cool and solidify before proceeding. A backstep or stitch technique is especially recommended for welding sheet metal, as it will help prevent burn-through and warping.
   
   

FAQs Address Welding of Thin Materials.

III. How to MIG Weld Thick Metal

Thick metal is generally considered to be anything more than 1/4 inch (6.4 mm) thick. Welding thick metal can also be challenging, as it requires more heat input and filler metal, as well as proper joint preparation and technique. To avoid problems such as lack of fusion, undercut, porosity, and cracking, here are some tips for MIG welding thick metal:

1. Use a larger wire diameter. A larger wire diameter will increase the heat input and the amount of filler metal, which will help achieve better fusion and penetration. A common wire diameter for thick metal is 0.045 inches (1.1 mm), but you can also use 0.052 inches (1.3 mm) or 0.062 inches (1.6 mm) depending on the metal thickness and type.

2. Use a higher voltage and wire feed speed. A higher voltage and wire feed speed will also increase the heat input and the size of the weld pool, which will help achieve better fusion and penetration. A good starting point is to use the suggested settings on your welder’s chart, and then fine-tune them according to your results. You can also use a tool like a Power and wire speed calculator to estimate the initial settings for your welder.

3. Use a lower shielding gas flow rate. A lower shielding gas flow rate will reduce the turbulence and the cooling effect on the weld pool, which will help prevent porosity and cracking. A common shielding gas for thick metal is 100% CO2, which provides deeper penetration and a higher deposition rate. A good flow rate for thick metal is around 15-20 CFH.

4. Use a longer stick-out. A longer stick-out will reduce the arc force and the spatter, which will help prevent undercut and overfill. A good stick-out for thick metal is around 1/2 inch (12.7 mm) or more.

5. Use a drag or backhand technique. A drag or backhand technique means moving the torch in the opposite direction of the wire feed, or towards the weld pool. This technique will provide better penetration and a higher deposition rate, as well as a convex and wider weld bead. A drag technique is especially recommended for welding carbon steel, as it will help prevent the formation of slag on the weld pool.

6. Use a weave or oscillation technique. A weave or oscillation technique means moving the torch side to side along the joint or making a zigzag pattern with the weld pool. This technique will help fill the gap and cover the entire joint, as well as allow the weld pool to cool and solidify before proceeding. A weave or oscillation technique is especially recommended for welding thick metal, as it will help prevent a lack of fusion and cracking.

Conclusion

MIG welding is a great welding process for different metal thicknesses, but it requires some adjustments and techniques to ensure a strong and consistent weld. By following the tips and best practices in this blog post, you can improve your MIG welding skills and achieve better results. Remember to always wear proper safety equipment and follow the manufacturer’s instructions when using your welder. If you want TIG weld metals, read How To TIG Weld Different Metal Thickness?

Related articles:

1. How to Weld Thin Metal: Types, Welders, and Techniques (2023)

2. How to MIG weld different metal thicknesses?

3. CO2 Gas Shielded Welding Thick Plates Techniques and methods

4. Arc Welding Guide (Definition, Process, Types, Applications, Materials, and Advantages)

5. Welding Materials Unveiled: Understanding the Characteristics of Metals and Alloys