How to MIG Weld Different Metal Thicknesses: A Guide

MIG welding can become tricky when working with different metal thicknesses. If you want strong and clean welds, it is essential to know how to MIG weld metals of the right thickness. 

In this guide, you will find easy-to-follow tips for setting up your machine and using the best technique for working with thin, medium, and thick metals. 

Whether you are fixing something at home or building a project, learning how to MIG weld metals of different thicknesses will help you get better results.

Grab your welder and follow along as we break down the basics for every type of metal thickness.

How to MIG Weld Different Metal Thicknesses

Welding metals of different thicknesses with a MIG welder requires the right settings, technique, and a little patience. 

Here’s what you need to know to get strong, clean welds every time:

1. Measure and Identify Metal Thickness

• Use a caliper or gauge to measure the thickness of your metal pieces.
• Thin metal is usually anything under 1/8 inch, while thick metal is anything above 1/4 inch.

2. Set the Voltage and Wire Speed

Thin Metals:

• Use la ower voltage to prevent burning holes.
• Lower the wire feed speed for better control.

Thick Metals:

• Increase the voltage to ensure deep penetration.
• Speed up the wire feed to maintain a hot and strong weld pool.

3. Choose the Right Wire and Shielding Gas

Thin Metals:

• Use a thinner wire, such as .023” or .030”.
• An argon/CO₂ mix is best for reducing spatter and achieving a smoother weld.

Thick Metals:

• Use a thicker wire, such as .035” or .045”.
• 100% CO₂ can work for extra penetration but may cause more spatter.

4. Adjust Your Welding Technique

Thin Metals:

• Move your torch quickly and avoid staying in one spot too long.
• Use a series of tack welds to limit heat and prevent warping.

Thick Metals:

• Slow down and let the weld pool form deeply.
• Make steady, even passes for maximum strength.
  

5. Test Settings on Scrap Metal First

• Always run a test bead on a scrap piece of similar thickness.
• Adjust your voltage and wire speed until the weld looks right and there’s no burn-through.

6. Prevent Warping and Distortion

• Thin metals are prone to warping with too much heat.
• Let the metal cool between welds and use clamps or fixtures to hold everything in place.
• Use shorter welds or stitch welding to manage heat.

7. Clean and Inspect Your Welds

• After welding, remove any slag or spatter with a wire brush.
• Check your welds for gaps, cracks, or holes.
• Strong, shiny welds with good penetration are what you’re aiming for.

8. Safety Tips

• Always wear a welding helmet, gloves, and protective clothing.
• Make sure your work area is well-ventilated.

MIG Welding Sheet Metal Guide

MIG welding sheet metal requires precision and the right tools. Here’s a streamlined approach, complete with examples, to help you achieve perfect welds on thin metals.

1. Choosing the Right MIG Welder for Thin Metal:

• Ideal Specs: A 140 amp, 110V welder works well for metals up to 1/8".
• Advanced Feature: Consider a welder with a 3-in-1 MIG feature, such as the ARCCAPTAIN MIG130 110V Portable No-Gas Flux Core Welder. It is a good entry-level machine, making it an excellent choice for DIY projects. You can take it anywhere, anytime for metal welding work.

2. Selecting the Welding Wire:

• Wire Diameter for Thin Metal: Use a diameter smaller than the base metal, such as .023 for metals up to 18 gauge.
• Wire Type Examples:

3. Shielding Gas Choices:

• Mild Steel: C25 mix (75% argon/25% CO2). For metal thinner than 14 gauge, reduce CO2 to avoid burn-through.
• Sheet Aluminum: Use 100% argon.
• Sheet Stainless Steel: A mix of 90% helium, 8% argon, and 2% CO2.

4. Weld Preparation Techniques:

• Cleaning: Ensure pieces are clean and well-aligned.
• Clamping: Use clamps to secure the pieces.
• Gap or Overlap: Leave a small gap or overlap sheets based on preference.
• Backing Bar: Use a copper or aluminum bar as a heatsink to prevent warping.

5. Setting Welding Parameters:

• Guidance: Adjust voltage, amperage, and wire speed to match metal thickness, wire size, and type.
• Synergic MIG Feature: Use for estimated parameters.

6. Effective Welding Techniques:

• Travel: Maintain a straight line for solid bead formation.
• Push Technique: Offers control and less penetration on sheet metal.
• Skip-welding: Reduces distortion by spreading out heat.

Examples in Action:

Also Read:  How to Stick Weld Different Thickness Metals - A Guide

MIG Welding for Hobbyists - Medium-Thickness Steel

If you are a hobbyist welder and want to weld medium-thickness mild steel, you should know that it is significantly more accessible and forgiving than sheet metal. However, you will still need to get things straight to finish your welding project. You will also need welding equipment, wire, preparation, and technique to do so. Here are the essential things you need to know about MIG welding hobbyist steel.

Welder For Medium-thickness Steel

To weld medium-thickness metal up to 1/2" or 1/4", you will need a 200-250 amp rated welder with 220V input. These machines have enough power to join thicker metal with ease.

Choosing the Right Welder - Budget-Friendly Option

The ARCCAPTAIN MIG200 Multi Process MIG Welder,  is perfect for up to 1/4" steel in a single pass. No need for fancy features, just a reliable 220V input.

Suitable MIG Wire for Medium-thickness Steel

Selecting the MIG Wire:

• For 18-Gauge and Beyond: Switch to a .030 size wire.
• Thicker Steel Consideration: For over 3/16", upgrade to a .035 wire.
• Pro Tip: Match wire thickness to base metal to avoid welding issues like lack of fusion or excessive penetration.

Additionally, ensure the thickness of the base metal and wire diameter match to prevent lack of fusion and undercutting, as well as excessive penetration and reinforcement.

Shielding Gas Guide

• Standard Option: C25 mix (75% argon/25% CO2) for a good balance of arc stability and aesthetics.
• Economical Alternative: 100% CO2 gives higher penetration but more spatter and rougher beads.

Welding with CO2 provides higher penetration, and shielding gas isn't so expensive. Nonetheless, if you want to get the job done cheaper and you don’t care about aesthetics, 100% CO2 is the way.

Read More: What is the Best Shielding Gas Used for MIG Welding?

Weld Preparation

Weld preparation for medium-thickness steel is significantly more manageable compared to thin metal but is often overlooked. You will also have to clean the weld joint, but you have more room for weld design.

For example, you can use a butt weld, T-joint design, or fillet weld in a flat, horizontal, or overhead position. Of course, the joint design will depend on specific welding projects and metal thickness, but there are certainly more options to work around than with sheet metal.

Welding Parameters and Technique

• Power Setting Guide: Aim for 1 amp per .001" of metal thickness.
• Technique Matters: Maintain a travel angle of 5-15 degrees and adjust the work angle as needed. Push for control or pull for penetration and narrow beads.

Welding Examples:

GMAW Welding Thick Plates

Welding thick plates using GMAW (Gas Metal Arc Welding) is challenging, and there are more suitable welding processes, such as Stick or Flux core welding. Nonetheless, with the right approach and suitable equipment, you can do fine. Here are some tips on what to do if you encounter a thicker piece in your workshop.

Welding Equipment For Thick Metal

When it comes to welding metals thicker than 1/2", the game changes significantly. Here's a breakdown to make things clearer:

1. Power Requirements for Thick Metals:

• Thicker than 1/2": You're entering the heavy-duty zone here.
• Power Source: A three-phase power input is a must for sufficient heat.
• Industrial-Grade Welders: For anything over 3/8", gear up with a welder rated up to 500 amps. These beasts can handle high heat and tough conditions.

2. Wire and Preparation for Thick Plates:

• Bigger Wire for Bigger Jobs: Jump to a .039 or even .045 wire diameter for these thick plates.
• Spool Size Matters: Industrial-grade wires come in heftier spools (like 45lbs) compared to the 2 or 10 lbs ones for hobbyists.
• Welding Technique: Use spray transfer for filling larger gaps, offering deep penetration and efficient deposition.

3. Choosing Shielding Gas:

• Base Metal Consideration: Your choice should match the application and metal type.
• Go-To Option for Steel: C25 (75% argon/25% CO2) remains a solid choice for steel.

Tackling thick metal welding is a whole different ball game, requiring more power, bigger tools, and the right techniques. But with the right setup, you can weld even the thickest plates with confidence and precision.

Also Read: Importance of Shielding Gas In MIG welding

Final Thoughts

In conclusion, MIG welding works great for thin to medium-thick metals but struggles with thicker plates. For heavy-duty jobs, stick or flux core welding is often a better choice. 

Understanding the basics and limitations of MIG welding helps prevent issues such as spatter, weak welds, and safety risks. 

Always use the correct settings, safety gear, and clean your metal with a wire brush or grinder. With practice and patience, you can master MIG welding and make strong, neat welds for any project.

FAQs About How to MIG Weld Different Metal Thicknesses

How to weld two different thicknesses?

To weld two pieces of different thicknesses, place the weld bead closer to the thicker metal. Use the settings for the thicker piece to ensure strong penetration. Move the torch slightly toward the thinner metal as you weld, but avoid too much heat on the thin side to prevent burn-through. Tack weld both pieces first to hold them in place.

Which is better, 0.8 mm or 0.9 mm MIG wire?

The choice between 0.8 mm and 0.9 mm MIG wire depends on your project. 0.8 mm wire is better for thin to medium metals because it gives more control and less spatter. 0.9 mm wire works well for thicker materials and gives deeper penetration. Choose the wire size that matches your metal thickness for the best results.

Can you MIG weld 2mm steel?

Yes, you can MIG weld 2mm steel. Set your machine to a lower voltage and wire speed to avoid burning through the metal. Use a smaller wire size like 0.8 mm for better control and a clean weld. Always test your settings on scrap metal first.

When welding pieces that are of unequal thickness?

When welding metal of unequal thickness, direct most of the heat toward the thicker piece. This helps prevent melting or burning through the thinner side. Adjust your angle and technique so the weld fully penetrates both pieces. Tack weld first to secure the pieces before finishing the joint.