Welding Articles

How to MIG Weld Different Metal Thicknesses - Guide

Dec 20, 2023

How to MIG Weld Different Metal Thicknesses

MIG welding is ideal for various metals and projects, whether you're a hobbyist or a DIY enthusiast. But when it comes to welding metals of different thicknesses, things can get tricky for beginners.

This article is here to guide you. We'll break down the essentials of MIG welding, focusing on techniques for sheet metal, medium-thickness steel, and thick plates. You'll also learn about the tools and skills needed for these tasks. By the end of this guide, you'll have a clear understanding of MIG welding's strengths and limitations, helping you tackle your projects with confidence.

How Does MIG Welding Deal With Different Thicknesses?

MIG welding is a favorite in the welding world for its versatility, especially when dealing with different metal thicknesses. Here's a breakdown with expert insights and practical examples:

1. Understanding the Basics:

  • Key Point: MIG welding excels with thin to medium-thick metals.
  • Expert Insight: For thicker metals, MIG can struggle due to its lower penetration compared to other processes like Stick or TIG welding.

2. Wire Diameter and Metal Thickness:

  • General Rule: Smaller wire diameter means less heat and filler metal - crucial for welding thinner materials without burn-through.
  • Pro Tip: Adjust your wire speed and voltage accordingly. Higher wire speed can compensate for a smaller diameter, especially on thicker materials.

3. Wire Diameter Choices:

  • Thin Metal (Sheet metal, Automotive parts)
    • Common Wire Diameter: 0.023 inches (0.6 mm)
    • Usage: Best for materials up to 1/8” thickness.
  • Medium Thickness (General fabrication, Home projects)
    • Wire Diameters: 0.030 inches (0.8 mm) or 0.035 inches (0.9 mm)
    • Usage: Ideal for materials between 1/8” to 1/4” thickness.

4. Practical Examples:

  • Automotive Repair: Using 0.023-inch wire for patching a thin car body panel.
  • Home DIY Projects: Opting for 0.030-inch wire for welding a steel frame for a garden gate.
  • Fabrication Work: Selecting 0.035-inch wire for constructing a steel workbench.

By understanding these nuances and making informed choices about wire diameter based on metal thickness, you can elevate your MIG welding results, whether you’re a hobbyist or a pro.

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 No Gas Mig Welder MIG feature, like the ARCCAPTAIN MIG130 110V Portable No Gas Flux Core Welder. It is good entry-level machine making it a great 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:

Metal Type Wire Size Shielding Gas Technique
Mild Steel .023 C25 mix Straight, Push
Stainless Steel .030 Tri-gas mix Skip-Welding
Aluminum .035 100% Argon Straight, Push


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

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.

In addition, you should match the thickness of the base metal and wire diameter to avoid a 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.

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:

Metal Thickness Welder Setting Wire Size Shielding Gas Weld Design
1/4" 205 amps .030 C25 mix Butt Weld
3/16" 190 amps .035 100% CO2 T-joint
1/2" 250 amps .035 C25 mix Fillet Weld

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.

Final Thoughts

In conclusion, MIG welding is an excellent option for welding thin to medium-thick metals. However, when it comes to welding thicker plates, it falls short. In such cases, Flux core or Stick welding is a better choice. It is important to understand the fundamentals and limitations of MIG welding to avoid issues such as spatter, safety hazards, undercut, porosity, holes, impact, distortion, poor penetration, and cracking. Proper training, equipment, and safety gear are necessary to ensure a successful weld. Additionally, using a wire brush and grinder can help clean the metal surface and prevent porosity and cracking. With practice and patience, you can become proficient in MIG welding and achieve high-quality welds.

Frequently Asked Questions

What are the recommended settings for MIG welding metal of varying thicknesses?

The recommended settings for MIG welding metal of varying thicknesses depend on the thickness of the metal being welded. For thin metals, a lower voltage and wire feed speed setting is recommended. For thicker metals, a higher voltage and wire feed speed setting is needed. A higher shielding gas flow rate is also recommended for thicker metals to provide better protection for the weld pool and prevent porosity and oxidation.

How can you prevent burn-through when MIG welding thin metal sheets?

To prevent burn-through when MIG welding thin metal sheets, you can use a lower amperage setting, reduce the wire feed speed, and increase the travel speed. You can also use a lower voltage setting and a shorter stick-out to minimize heat input. Additionally, using a copper backing plate or heat sink can help dissipate heat and prevent burn-through.

What is the maximum thickness a MIG welder can effectively join?

The maximum thickness a MIG welder can effectively join depends on the amperage capabilities of the welder. In general, a MIG welder can weld up to 1/4 inch thickness for every 250 amps. However, this can vary depending on the type of metal being welded and the specific MIG welder being used.

How do you adjust the amperage on a MIG welder for welding different metal thicknesses?

To adjust the amperage on a MIG welder for welding different metal thicknesses, you can refer to the manufacturer's recommendations or use a welding chart as a guide. In general, a higher amperage is needed for thicker metals and a lower amperage is needed for thinner metals. Adjusting the wire feed speed and voltage settings can also help fine-tune the amperage output.

Can you MIG weld thick steel to thin metal, and what are the best practices?

Yes, it is possible to MIG weld thick steel to thin metal, but it requires careful consideration of the welding parameters and techniques. To prevent burn-through and distortion, a lower amperage setting, slower wire feed speed, and shorter stick-out can be used for the thin metal. 

What techniques should be used for MIG welding pipes with differing wall thicknesses?

When MIG welding pipes with differing wall thicknesses, it is recommended to use a welding technique called "step welding." This involves starting at the thinner section of the pipe and gradually moving towards the thicker section, making multiple passes if necessary. 

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