Mild steel is one of the many metals that can be precisely and adaptably welded with TIG welding. When setting up a TIG welder for mild steel, the key is ensuring the right balance of equipment, settings, and techniques to achieve a strong, clean weld.

Gather Your Equipment and Materials

Before you begin TIG welding on mild steel, it’s essential to ensure that all necessary equipment and materials are prepared. Having everything ready will streamline the process and ensure high-quality results. Below is an expanded list of the items you’ll need:

• TIG Welder: Choose a TIG welder with both AC/DC capabilities to accommodate different materials and welding conditions. For mild steel, a DC Negative (DCEN) setting is ideal, as it provides better penetration and cleaner welds. Ensure your machine is set up correctly for TIG welding to maintain consistency.
• Tungsten Electrode: Typically, a 2% thoriated tungsten (red) is used for welding mild steel due to its good balance of durability and heat conductivity. However, you can also use 2% ceriated tungsten (gray) for applications where a cleaner arc is needed. Tungsten size is chosen based on material thickness, with 1/16-inch or 3/32-inch being common sizes for mild steel welding.
• Filler Rod: The ER70S-2 or ER70S-6 filler rods are typically used for mild steel because they offer excellent strength and weldability. ER70S-2 is more suitable for clean, new steel, while ER70S-6 is ideal for slightly dirtier or rusty steel as it has better deoxidizing properties.
• Gas: Pure argon (100%) is the recommended shielding gas for mild steel TIG welding. Argon protects the weld area from contamination and ensures a smooth and stable arc. Argon flow rates should be between 15-20 CFH (cubic feet per hour), depending on the size of the weld and the work environment.
• Welding Helmet: TIG welding requires a welding helmet with an auto-darkening lens. The recommended lens shade for TIG welding on mild steel is usually shade 9-13 to protect your eyes from the intense UV radiation. Make sure the helmet fits comfortably and provides clear visibility of the weld pool.
• Protective Gloves and Clothing: Always protect yourself from heat, UV rays, and sparks by using gloves and protective gear. Leather gloves designed for welding provide protection while maintaining dexterity for precise weld control. To further prevent burns, dress in flame-resistant apparel, such as sleeves or a welding jacket.
• Clean Metal: Mild steel must be free of any rust, oil, dirt, grease, or other contaminants before welding. These contaminants can cause defects in the weld and compromise the final quality. Ensure you have properly cleaned the workpieces to maintain a strong bond and a neat weld. Wire brushes, grinders, and chemical degreasers are commonly used to prepare the surface before welding.

Prepare the Mild Steel

Proper preparation of your mild steel is crucial to achieving high-quality, durable welds. By taking the time to properly clean and fit your steel, you can reduce the chances of contamination and ensure that your weld pool flows smoothly. Here’s how to prepare your mild steel before welding:

• Clean the Surface: Surface preparation is key to preventing contamination during welding. To begin, clean the steel of any possible rust, scale, or dirt with a wire brush or grinder. These contaminants can lead to poor arc stability and weaken the weld. After grinding, use a degreaser or solvent to remove oils, grease, and any other residue that might affect the weld quality. Ensure the area around the weld is spotless, as even small contaminants can cause defects like porosity.
• Fit-up: When welding two pieces of mild steel, it’s important that they fit together well. Proper fit-up will ensure that the weld is strong and has the proper penetration. For butt joints, leave a small gap (around 1/16 inch) between the edges of the pieces to allow the filler rod to flow into the joint without excessive spatter. For corner or T-joints, ensure the pieces align correctly, and the joint configuration is optimal. Misalignment can lead to inconsistent welds, excess heat input, or difficulty controlling the weld pool. Ensure that the edges of the workpieces are smooth and aligned before starting your weld.

Set the Gas Flow

The shielding gas is essential for preventing atmospheric contamination of the weld pool. Proper gas flow is necessary to ensure the weld’s integrity and quality. Follow these guidelines when setting the gas flow for TIG welding mild steel:

• Gas flow rate: Set the gas flow rate to 15-20 cubic feet per hour (CFH). If the gas flow is too high, it may create turbulence, which can disrupt the stability of the arc and lead to poor weld quality. Conversely, insufficient gas flow can result in inadequate shielding, leaving the weld vulnerable to contamination, which can cause defects like porosity and weak joints.
• Gas regulator setup: Attach the gas regulator securely to the gas cylinder. This will control the gas flow to the TIG welder. Make sure that the hose connecting the regulator to the TIG torch is tightly secured to prevent gas leaks. A loose or damaged hose could lead to unstable shielding and an inconsistent weld.
• Check gas quality: Always use pure argon (100%) for welding mild steel. Argon provides excellent shielding properties, ensuring that the weld pool is protected from oxygen, nitrogen, and other gases in the atmosphere that could compromise the weld.

Select the Correct Tungsten Electrode

Choosing the correct tungsten electrode is crucial to achieving a stable arc and precise welds. The right tungsten ensures a clean, consistent arc and efficient heat transfer. Here are the important considerations for selecting tungsten for welding mild steel:

• Tungsten size: For welding mild steel, use a 1/16-inch or 3/32-inch tungsten electrode. These sizes are appropriate for most thin to medium-thickness mild steel materials. For thicker materials, you may need a larger tungsten electrode (e.g., 1/8-inch). Choosing the correct size ensures better arc control and heat distribution, which leads to more precise welds.
• Electrode preparation: Prepare the tungsten electrode properly by grinding it to a fine point. Typically, the point should be 2-3 times the diameter of the electrode. For thin materials, use a sharp, pointed tip (approximately 60-degree angle) to achieve a stable arc and precise control. For thicker materials or DC welding, a balled tip (formed by heating the tungsten and allowing the tip to round out) is more effective, as it provides more heat and stability to the weld pool.
• Electrode type: For mild steel, 2% thoriated tungsten (red) is commonly used, as it offers a good balance of longevity and arc stability. Alternatively, 2% ceriated tungsten (gray) is suitable for cleaner arcs but has a shorter life span.

Adjust the Welding Machine Settings

Proper machine settings are essential for achieving optimal weld quality. Adjusting your TIG welder based on the thickness and type of mild steel you’re welding ensures proper heat control and a strong, clean weld.

• Polarity: Set the welder to DC negative polarity (DCEN) for welding mild steel. This is the most common and effective polarity for mild steel TIG welding. DCEN ensures better heat penetration into the workpiece and cleaner beads compared to other polarities.
• Amperage: Adjust the amperage based on the material’s thickness. A general rule of thumb is to use 1 amp for every 0.001 inch of material thickness. For instance, when welding 1/8-inch mild steel, you should set the amperage to around 120 amps. Always start with a lower amperage and adjust as necessary to ensure optimal control over the weld pool, preventing overheating or under-welding.
• Pre-flow and Post-flow gas time: Set the pre-flow gas time to about 0.5 to 1 second. This ensures that shielding gas starts flowing before the arc is initiated, protecting the tungsten and workpiece from contamination. Set the post-flow gas time to 5-10 seconds to continue shielding the weld area after the arc is extinguished, preventing oxidation as the weld cools down.

Choose the Right Filler Rod

Selecting the right filler rod is essential to achieving a strong and durable weld. The filler rod should match the base material and complement the welding process. Here’s what you need to consider when choosing the filler rod for mild steel:

• Filler rod material: Use an ER70S-2 or ER70S-6 filler rod for welding mild steel. These rods are commonly used because they provide strong welds with minimal spatter and excellent arc stability. ER70S-2 is suitable for clean, new steel, while ER70S-6 works better for slightly rusted or dirty steel due to its superior deoxidizing properties.
• Rod size: The filler rod size should be selected based on the thickness of the material and the required bead size. A 1/16-inch or 3/32-inch rod is typical for most mild steel welding projects. Make sure to select a rod that is compatible with the size of the joint and the amount of filler required.
• Cleanliness: Before use, ensure that the filler rod is clean and free from contaminants such as rust, oil, and dirt. Contaminants can weaken the weld, leading to defects and poor structural integrity. Store filler rods in a clean, dry place to maintain their quality before use.

Set Up the Torch and Start the Arc

Correct torch setup and arc initiation are essential for stable welding and high-quality results. Here are the key steps for setting up the torch and starting the arc for mild steel:

• Torch angle: Keep the torch held at a 15–20 degree angle from the vertical. This angle directs the heat precisely into the weld joint, allowing for better penetration and control. For fillet welds, tilt the torch slightly so that the heat is focused on the joint to ensure a smooth, even weld bead.
• Torch distance: Maintain a distance of about 1/8 to 3/16 inch between the tungsten electrode and the workpiece. This distance is ideal for creating a stable arc while preventing the tungsten from touching the material, which could cause contamination or loss of arc stability.
• Starting the arc: Use either the high-frequency start or lift start method, depending on your welder’s capabilities. The high-frequency start method is ideal as it allows the arc to start without touching the workpiece, ensuring a clean arc initiation and avoiding contamination of the tungsten. If your welder doesn’t have high-frequency start, the lift start method can be used, where you gently touch the tungsten to the workpiece and lift it to start the arc.

Begin Welding

Once your torch is properly set up and the arc is initiated, it’s time to start welding. Maintaining control over the torch, heat, and filler rod is critical for creating a strong and consistent weld:

• Move slowly: TIG welding requires precision and patience, so move the torch at a consistent, slow pace. This allows you to maintain steady heat input, which is crucial for achieving a uniform bead and preventing the material from overheating. Moving too quickly could result in weak or incomplete fusion, while moving too slowly may lead to excess heat and material distortion.
• Control the heat: The key to successful TIG welding is controlling the heat input. Adjust your torch travel speed to maintain an even heat distribution. If the weld pool becomes too large or molten, increase the travel speed to reduce the heat. If the weld appears too narrow or shallow, slow down your pace to give the material more time to melt and form a deeper, stronger bond.
• Add filler material: As you move the torch along the joint, feed the filler rod into the leading edge of the weld pool. The filler rod should melt smoothly into the pool, creating a uniform bead. Be mindful of the filler rod’s consistency to avoid any clumping or poor fusion. Keep the rod at a consistent angle to maintain even feed and prevent any contamination from entering the weld pool.

Finish the Weld

Once the welding pass is complete, it’s important to finish the process carefully to ensure the integrity of the weld:

• Allow cooling: Let the weld cool down naturally in the open air. Rapid cooling can cause thermal shock, which may result in cracks or weaknesses in the weld. Be patient and allow the material to cool slowly to preserve the strength and durability of the joint.
• Inspect the weld: Examine the bead for uniformity, penetration, and general look once the weld has cooled. The weld bead should be smooth, with even width and depth, without any signs of undercut, porosity, or incomplete fusion. If any defects are noticed, consider reworking the weld to correct them.

Post-Weld Cleaning

Proper post-weld cleaning is essential to remove any residues and ensure a clean and durable final product. This step also helps improve the appearance and prevent contamination:

• Remove slag and spatter: If any slag or spatter is present, carefully remove it from the weld area using appropriate tools. This is especially important if you’re using a process that generates slag. For TIG welding, spatter is minimal, but you may still need to clean the surface.
• Clean the welded area: Use a wire brush or stainless steel brush to clean the weld and surrounding area. This will help remove any discoloration or oxidation that occurred due to the heat from welding. Be sure to use a brush that is specifically designated for mild steel to avoid contamination. Do not use the same brush on aluminum or stainless steel, as cross-contamination could result in poor welds in future projects.

TIG Welder Settings for Mild Steel: Quick Reference Guide

The table below provides a quick reference for the essential settings and parameters when setting up your TIG welder for mild steel. This guide can help you make adjustments depending on the material thickness and specific welding needs.

Conclusion

It takes accuracy and focus to set up a TIG welder for mild steel. You can make sure your machine is set up correctly for strong, clean welds by following the instructions in this tutorial. The key to successful TIG welding lies in choosing the right settings for your welder, using clean materials, and mastering techniques.

With proper preparation and the right equipment, TIG welding can provide high-quality, aesthetically pleasing welds on mild steel. Consistency, practice, and attention to detail will help you achieve optimal results every time.

Key Takeaways:

• Polarity: Use DC negative (DCEN) for mild steel welding to ensure strong penetration and clean beads.
• Amperage: Set the amperage at 1 amp per 0.001 inch of material thickness to maintain proper heat control.
• Gas Flow: Maintain a gas flow rate of 15-20 CFH to protect the weld pool from contamination.
• Tungsten Electrode: Use a 1/16-inch or 3/32-inch tungsten electrode, depending on material thickness, and grind it to a fine point.
• Filler Rod: Choose ER70S-2 or ER70S-6 filler rods for mild steel, ensuring a strong and clean weld.
• Torch Angle and Distance: Hold the torch at a 15-20 degree angle and maintain a distance of 1/8 to 3/16 inch from the workpiece for stable arcs.
• Weld Prep: Clean the steel thoroughly before welding to avoid contamination and ensure strong welds.

Frequently Asked Questions (FAQs)

What is the best polarity setting for TIG welding mild steel?

For welding mild steel, you should use DC Negative (DCEN) polarity. This polarity provides good penetration and clean welds, making it the most suitable for welding mild steel.

How do I choose the right tungsten electrode for mild steel?

For mild steel, use a 1/16-inch or 3/32-inch tungsten electrode. The size depends on the thickness of the material you’re welding. A pointed tip is ideal for thinner materials, while a balled tip is used for thicker ones when using DC polarity.

How do I determine the correct amperage for my TIG welder?

The general rule of thumb is to set the amperage at 1 amp per 0.001 inch of material thickness. For example, if you are welding 1/8-inch mild steel, set the amperage to 120 amps. Always start with lower amperage and adjust if needed.

What type of gas is used for TIG welding mild steel?

The ideal shielding gas for welding mild steel with a TIG welder is pure argon (100%). Argon provides excellent shielding and helps produce clean, strong welds without contamination.

Why is surface preparation important for TIG welding mild steel?

Before welding, carefully clean the surface to get rid of any dirt, oil, grease, or rust. Contaminants can cause poor weld quality and defects. Proper cleaning ensures that the weld pool remains uncontaminated, resulting in a stronger and more aesthetically pleasing weld.