How NOT to TIG Weld Carbon Steel & Troubleshooting TIG Welds
TIG welding is known for producing clean, precise welds — but only if your technique, prep, and setup are solid.
If your welds on carbon steel are black, porous, lumpy, or inconsistent, it’s not just frustrating — it’s a sign something is wrong.
The good news? Most of these problems come from fixable mistakes, especially for beginners.
In this article, we’ll break down the most common causes of “crappy” welds and give you clear, practical solutions.
Go to Main Index page for TIG Welding Carbon steel Basics
🔍 Symptoms and What They Mean
Let’s decode what your weld is telling you:
|
Symptom |
Likely Cause |
|
Black or sooty welds |
Poor gas coverage, contaminated base metal |
|
Porosity (tiny holes) |
Dirty metal, dirty filler rod, oil residue, gas leaks, insufficient or excessive argon flow rates |
|
Lumpy or irregular beads |
Inconsistent arc length, filler metal addition, or travel speed |
|
Crusty or flaky weld surface |
Too much heat input, wrong cup setup, poor gas coverage |
|
Black or purple tungsten tip |
Arc too long, or post-flow too short, moving torch too quickly before post flow has time to cool and shield tungsten tip |
🧪 Fix #1: Check Your Shielding Gas Setup
✅ Use 100% argon for carbon steel ( don't even try using C25 MIG gas )
✅ Set flow rate to 2 to 3 CFH per cup size ..( example #8 cup requires 16-24 CFH)
✅ Use a gas lens to improve coverage and reduce turbulence
✅ Maintain a tight arc length (1/8" or less) best practice is equal or less than electrode diameter used
✅ Shield the weld from wind, fans, or shop drafts (remember that some machines have a strong fan so point machine face away from weld area)
🔧 Tip: If your tungsten turns black fast, your shielding gas coverage is likely the problem — not your technique.
🧼 Fix #2: Clean the Metal and Filler Rod
TIG doesn’t tolerate dirty surfaces. For clean welds:
- Grind or sand mill scale, rust, and paint off the base metal
- Wipe parts with acetone after prepping to clean bright metal
- Store filler rods in a sealed tube — wipe them down before use
- Don’t handle clean filler with greasy gloves or hands
📦 Even brand-new filler rod can be oily or dusty from shipping.
Make sure you have TIG Rod (either ER70S-2 OR ER70S-6) and NOT Gas welding rod (RG45, RG60 etc)
Gas welding rods look almost just like TIG rods but will bubble and spit and make you cuss if you use them on TIG
🎯 Fix #3: Control Arc Length and Heat Input
Many beginners hold the arc too long, which:
- Makes the arc unfocussed
- Increases the size of the arc plume causing the tip of the filler rod to melt and blob
- Causes arc wandering and overheating
💡 Keep the tungsten 1/8" or less from the puddle. A good rule of thumb is equal to or slightly less than the diameter of tungsten used.
Use a foot pedal or amperage control to back off during pauses or tight spots.
🕳️ Fix #4: Avoid excessive fit up Gaps and Poor Joint Prep
Big gaps between parts = more heat and longer arc time = more contamination risk.
- Use tight, consistent fit-ups wherever possible
- Tack weld at multiple points to keep alignment
- Try to make tack welds smaller than the final weld so that they blend in easily when welded over
🔥 Fix #5: Adjust Torch Technique
Watch for:
- Torch too far from the weld = arc instability
- Too steep of a torch angle = rod balls before reaching puddle, gas coverage suffers
🎥 Practice steady torch motion and aim the arc right at the center of the joint.
🧰 Troubleshooting Table
|
Problem |
Possible Causes |
Solutions |
|
Sooty welds |
Dirty metal, poor gas coverage |
Clean thoroughly, check cup & flow rate |
|
Porosity |
Contaminated filler, gas leaks, too long arc, wrong filler rod |
Clean rod, tighten fittings, shorten arc |
|
Black tungsten |
Long arc, poor article-flow |
Tighten arc, increase article-flow to 5–10s |
|
Lumpy beads |
Inconsistent speed, bad filler timing |
Slow down, practice feeding rhythm |
|
Cracking or crater holes |
Rapid cooling, high heat input, no crater fill, insufficient filler metal |
Use downslope or taper pedal to finish |
📌 Summary
Crappy TIG welds usually come down to a handful of fixable issues — poor gas coverage, dirty materials, or inconsistent technique. By tightening up your setup, keeping everything clean, and focusing on consistent hand movement, you can turn black, porous, or lumpy welds into clean, professional-looking beads. TIG is all about control — and with practice, you'll get it.
