One of the first challenges I ran into with flux core welding was figuring out why some welds had great penetration while others looked weak or burned straight through the plate. It didn’t take long to realize the issue came down to amperage. Running too cold left me with poor fusion, while cranking it too hot ruined the bead and wasted filler wire. That’s where a flux core welding amperage chart really makes the difference.
By matching your wire size, base metal thickness, and joint prep to the right settings, you can keep arc control steady and avoid costly mistakes—whether you’re laying beads on mild steel, tackling stainless, or comparing the results against MIG and TIG processes. Getting this right matters for weld strength, safety, and overall efficiency. Stick around—I’ll walk you through the exact amperage ranges I use in the shop so you can dial in your own setup with confidence.
Why Amperage Matters in Flux Core Welding
Amperage controls the heat in your weld. Too high, and you’ll burn through thinner metals or create a wide, sloppy bead. Too low, and your weld won’t penetrate enough, leaving you with a weak joint that could fail under stress. I learned this the hard way early on when I tried welding a 1/8-inch steel plate with settings meant for 1/4-inch material. The result? A bead that looked like it was barely holding on and a quick lesson in double-checking my settings.
In flux core welding, amperage affects:
- Penetration: Higher amperage drives the weld deeper, perfect for thicker metals.
- Bead Profile: Low amperage gives you thin, weak beads; high amperage creates wider, stronger ones.
- Spatter Control: Wrong settings mean more spatter, which is a pain to clean up.
- Arc Stability: Proper amperage keeps the arc steady, reducing interruptions.
For DIYers and students, getting this right means fewer mistakes and less wasted material. For pros, it’s about efficiency and meeting code requirements, like those from the American Welding Society (AWS).
Understanding Flux Core Welding Basics
Flux core welding uses a tubular wire filled with flux that melts to create a protective gas shield around the weld pool. This makes it ideal for outdoor work where wind might blow away shielding gas used in MIG welding. There are two types: self-shielded FCAW, which relies solely on the flux in the wire, and gas-shielded FCAW, which uses an external gas like CO2 or an argon-CO2 mix for extra protection.
Self-shielded is my go-to for fieldwork, like when I’m repairing heavy equipment on a windy construction site. It’s forgiving on rusty or dirty surfaces, but it can produce more spatter. Gas-shielded FCAW, on the other hand, gives cleaner welds with less cleanup, making it great for shop work or precision jobs like automotive repairs.
The wire size, material thickness, and welding position all influence your amperage settings. Common wire sizes are 0.030”, 0.035”, and 0.045”. Thinner wires work for lighter materials, while thicker wires handle heavy-duty jobs. Always check your wire’s manufacturer specs—some are designed for low amperage, others need more juice.
Flux Core Welding Amperage Chart
Here’s a practical flux core welding amperage chart to get you started. These are general starting settings based on common constant-voltage (CV) machines. For self-shielded E71T-GS on mild steel, use the rows up to 3/16”. For 1/4” and thicker, use E71T-11 (self-shielded, multipass) or E71T-1 (gas-shielded) as noted. Always test on scrap metal first, as machines, wire brands, and conditions vary. IPM stands for inches per minute (wire feed speed).
| Wire Diameter | Material Thickness | Voltage | Amperage | Wire Feed Speed (IPM) |
|---|---|---|---|---|
| 0.030” | 20 gauge (0.035”) | 16–18 | 70–100 | 200–250 |
| 0.030” | 1/8” (0.125”) | 18–20 | 100–130 | 250–300 |
| 0.035” | 1/8” (0.125”) | 18–20 | 110–140 | 170–220 |
| 0.035” | 3/16” (0.1875”) | 19–21 | 130–170 | 190–240 |
| 0.045” | 1/4” (0.25”) — E71T-11 or E71T-1 | 21–24 | 150–200 | 150–220 |
| 0.045” | 3/8” (0.375”) — E71T-11 or E71T-1 | 23–26 | 170–220 | 170–240 |
Notes:
- For vertical or overhead welding, reduce amperage by 10–15% to help control the weld pool.
- Gas-shielded FCAW may need slightly higher voltage (≈1–2 V) for the same thickness.
- On CV machines, amperage follows wire feed speed (WFS). Set voltage for arc length/bead shape, then tweak WFS to land in the amperage range.
- Keep contact tip to work distance (CTWD) around 1/2–3/4” for self-shielded wires. Longer stickout drops current and penetration; shorter raises them.
- Always check your welder’s manual or the chart inside the wire feed door and your wire manufacturer’s datasheet for specific recommendations.
How to Use the Amperage Chart
Using the chart is simple, but it’s not set-and-forget. Start by identifying your wire size and the thickness of the metal you’re welding. For example, if I’m welding 1/8-inch steel with 0.035” wire, I’ll set my machine to around 18–20 volts and 110–140 amps, with a wire feed speed of 170–220 IPM. Then, I run a test bead on scrap metal to check the arc, penetration, and spatter.
Here’s a step-by-step guide:
Check Wire and Material: Match your wire diameter to the material thickness using the chart.
Set Polarity: Self-shielded wires like E71T-GS and E71T-11 usually run DCEN. Gas-shielded FCAW such as E71T-1 typically runs DCEP. Double-check your wire’s spec sheet and machine polarity.
Adjust Voltage and Amperage: Use the chart as a starting point. Set voltage for a stable arc length and bead shape, then adjust wire feed speed to bring amperage into range.
Test Weld: Run a bead on scrap metal. Look for a smooth arc, consistent bead, and minimal spatter.
Fine-Tune: If the weld is too cold (weak penetration), increase WFS slightly (amperage will rise) or shorten CTWD. If it’s too hot (burn-through), drop WFS a touch or lengthen CTWD slightly.
A common mistake I see with beginners is sticking rigidly to the chart without testing. Machines vary—my old Lincoln welder runs hotter than my newer Miller, so I always adjust after a test weld.
Choosing the Right Flux Core Wire
Not all flux core wires are created equal. The most common for general use is E71T-GS, a self-shielded wire great for mild steel and thinner material. It’s versatile and widely available at places like Home Depot. For heavier structural work or thicker sections, E71T-11 (self-shielded, multipass) is a solid choice. If you’re using gas-shielded FCAW, E71T-1 with CO2 or an argon-CO2 mix gives cleaner welds.
Wire size matters too:
- 0.030”: Best for thin metals (20–14 gauge), like auto body panels. Needs less amperage, so it’s great for 120V welders.
- 0.035”: A middle ground for 18 gauge to 3/16” steel. I use this for most general repairs.
- 0.045”: For thicker materials (1/4” and up), like structural steel or heavy machinery; typically paired with E71T-11 or E71T-1.
One time, I grabbed a spool of 0.045” wire for a thin sheet metal job, thinking I could just turn down the heat. Big mistake—burn-through city. Always match the wire to the job, and check the manufacturer’s recommended settings.
Setting Up Your Welder for Flux Core
Setting up your welder properly is half the battle. Here’s what I do every time I fire up my machine for flux core welding:
Clean the Metal: Even though FCAW is forgiving, grind off rust, mill scale, or paint. A clean surface reduces porosity and improves weld strength.
Check Drive Rollers: Use knurled rollers for flux core wire—they grip the hollow wire without crushing it. Smooth MIG rollers can cause feeding issues.
Set Wire Tension: Too much tension flattens the wire; too little causes slipping. Feed the wire against a non-conductive surface (like wood) and adjust until it feeds smoothly without birdnesting.
Stickout Length: Keep the contact tip to work distance (CTWD) around 1/2” to 5/8” (up to ~3/4” for some self-shielded wires). Too long, and you’ll get a weak arc and more spatter.
Ground Clamp: Ensure a solid ground connection. A rusty or painted surface can cause an unstable arc.
I once spent an hour troubleshooting a choppy arc, only to realize my ground clamp was loose. Don’t skip the basics—they bite you when you do.
Common Mistakes and How to Fix Them
I’ve made my fair share of mistakes with flux core welding, and I’ve seen plenty of others do the same. Here are the big ones and how to fix them:
Burn-Through: Happens when amperage is too high for thin metal. Lower the amperage (WFS) and increase travel speed slightly to cool the arc.
Porosity: Looks like tiny holes in the weld. Usually caused by dirty metal or improper shielding. Clean the surface thoroughly and check your stickout length.
Excessive Spatter: Often due to high voltage or wrong polarity for your wire. Dial down the voltage and confirm DCEN for self-shielded vs DCEP for gas-shielded FCAW.
Weak Welds: If the weld isn’t penetrating, increase amperage (raise WFS) or slow your travel speed. Practice a steady hand to maintain consistent heat input.
One time, I was rushing a job and didn’t clean the metal properly. The result was a porous weld that failed a pressure test. Lesson learned: take the extra five minutes to prep.
Pros and Cons of Flux Core Welding
Pros
- Portability: No external gas means you can weld anywhere, even in windy conditions.
- Versatility: Works on thicker materials and dirty or rusty surfaces.
- High Deposition Rate: Faster than stick welding, great for big projects.
- Ease of Use: Beginners can pick it up quickly with practice.
Cons
- Spatter: Self-shielded FCAW produces more spatter than MIG or gas-shielded FCAW.
- Cleanup: Slag removal takes time, especially on multi-pass welds.
- Fumes: FCAW generates more fumes than other processes, so use proper ventilation.
- Equipment Cost: A good FCAW-capable welder can be pricier than basic stick welders.
Practical Tips for Better Flux Core Welds
Here are some tricks I’ve picked up over the years:
Practice on Scrap: Always test your settings on a piece of scrap metal that matches your project’s thickness and material.
Use a Drag Technique: Pull the gun toward you (drag) rather than pushing. This gives better penetration and a smoother bead.
Control Travel Speed: Too fast, and you’ll get a thin bead; too slow, and you’ll pile up too much filler. Aim for a steady, even pace.
Ventilation: FCAW fumes are heavy. Use a fan or weld outdoors to avoid breathing them in.
Check Your Consumables: Worn contact tips or liners can cause feeding issues. Replace them regularly.
When I was learning, I’d spend hours practicing on scrap steel, tweaking settings until the welds looked right. It’s tedious, but it builds muscle memory and confidence.
Applications for Flux Core Welding
Flux core welding shines in specific scenarios:
- Construction: Perfect for structural steel, bridges, or heavy equipment repair due to its deep penetration and portability.
- Automotive: Great for patching exhaust systems or frames, especially with thinner wires.
- DIY Projects: From building trailers to custom gates, FCAW is forgiving for hobbyists working with less-than-perfect materials.
- Shipbuilding: Its ability to handle thick plates and outdoor conditions makes it a staple in shipyards.
I once helped a buddy weld a trailer frame in his backyard using a 120V flux core welder. The settings chart got us close, but a few test welds dialed it in perfectly. The trailer’s still hauling years later.
Safety Considerations
Welding is rewarding but dangerous if you’re careless. Here’s what I always keep in mind:
- Protective Gear: Wear a welding helmet with the right shade (10–13 for FCAW), flame-resistant gloves, and a jacket. I’ve got a scar from a stray spark that taught me to cover up.
- Ventilation: FCAW fumes are toxic. Weld in a well-ventilated area or use a respirator.
- Fire Safety: Keep a fire extinguisher nearby. Sparks can ignite grease, rags, or sawdust.
- Electrical Safety: Check cables for damage and ensure your machine is grounded properly.
Conclusion
Mastering flux core welding starts with understanding your amperage settings, and a good flux core welding amperage chart is your roadmap to success. Whether you’re a DIYer patching up a fence, a student practicing for certification, or a pro welding structural steel, the right settings mean stronger welds, less cleanup, and safer work.
By matching your wire size, material thickness, and welding position to the chart, then fine-tuning with test welds, you’ll avoid common pitfalls like burn-through or porosity. With practice, you’ll develop a feel for the arc and produce welds that look good and hold up under stress.
FAQ
What’s the best flux core wire for beginners?
For beginners, I recommend E71T-GS in 0.030” or 0.035” diameter for thin to medium-thickness steel up to about 3/16”. It’s versatile, widely available, and easy to dial in. Start with the settings in the amperage chart and practice on scrap to get the hang of it.
Can I use flux core welding on thin metal?
Yes, but use a smaller wire (0.030”) and lower amperage to avoid burn-through. For example, on 20-gauge steel, set your welder to 16–18 volts and 70–100 amps. Test on scrap and use a drag technique for control.
Why am I getting so much spatter with flux core welding?
Excessive spatter usually comes from high voltage, incorrect stickout, or the wrong polarity for your wire. Check whether your FCAW process is self-shielded (typically DCEN) or gas-shielded (typically DCEP), reduce voltage slightly, and keep your stickout around 1/2”. Cleaning the metal beforehand also helps.
Do I need a special welder for flux core?
Not necessarily, but your welder must allow polarity selection (DCEN/DCEP) and have knurled drive rollers for flux core wire. Most modern MIG welders are dual-purpose and can switch between MIG and FCAW with a quick setup change.
How do I know if my weld is strong enough?
A strong weld is uniform, with no porosity, undercut, or cracks. Test it by clamping the piece and stressing it (e.g., hitting it with a hammer for non-critical projects). For structural work, follow AWS codes and consider professional inspection.
