Tungsten Types, Selection, and Preparation for Stable Arc Control

Why Tungsten Choice and Prep Matter

The tungsten electrode is the non-consumable conductor that shapes the arc. Its alloy type and tip geometry influence three things you feel immediately at the torch: how easily the arc starts, how tightly the arc stays focused, and how well the electrode resists contamination (especially during momentary contact or unstable puddle conditions). Stable arc control comes from matching tungsten type, diameter, and tip prep to your machine output (AC or DC), your amperage range, and the base metal’s heat behavior.

What Changes When You Change Tungsten

• Starts: Some alloys emit electrons more readily, giving smoother, lower-effort starts and less “spitting” at ignition.
• Arc focus: Diameter and tip shape control arc cone width. A sharper point concentrates heat; a blunter point spreads it slightly and can reduce tip erosion at higher current.
• Contamination tolerance: All tungstens can be contaminated by touching the puddle or filler, but some hold their shape better and are less prone to forming large, unstable balls or shedding inclusions into the weld.

Tungsten Types (What They Are Used For)

Modern inverter machines can run many tungsten types successfully. The goal is consistent performance, not chasing a “magic” electrode. Below are common options and what they typically do in real use.

Practical Takeaway for Most Students

• If you want one tungsten that works well on most AC/DC inverters: 2% lanthanated (blue) is a reliable default.
• If you do a lot of very low-amperage, thin material work: consider 2% ceriated (gray).
• If you run older AC aluminum procedures that prefer a balled tip: zirconiated (brown) or pure (green) may be used, but many inverters still perform well with lanthanated and a controlled tip.

Selecting Diameter and Amperage Range

Diameter is as important as alloy. Too small overheats and deforms; too large can make starts less crisp at low amperage and can feel “lazy” on thin work. Use this as a practical starting point and adjust based on your machine and joint heat sink.

Rule of thumb: If your tip is rounding over quickly, forming a large ball, or the arc is wandering at your target amperage, move up a diameter or reduce amperage/duty cycle. If starts feel inconsistent at very low amperage, consider a smaller diameter or a low-amp-friendly alloy (often ceriated or lanthanated).

Selection Guidelines by Machine and Base Metal

DC Machines (or DC mode on AC/DC)

For most steels and stainless on DCEN, you want a pointed tungsten for a tight, controllable arc. Lanthanated and thoriated are known for holding a point, but lanthanated is widely used because it performs well without the thorium dust concern.

Continue in our app.

• Listen to the audio with the screen off.
• Earn a certificate upon completion.
• Over 5000 courses for you to explore!

Or continue reading below...

Download the app

• Steel / stainless (DCEN): 2% lanthanated (blue) in 1/16 in for thin to medium, 3/32 in for medium to heavier. Use a sharp point with a small flat.
• Low-amperage precision (DCEN): 2% ceriated (gray) in 1/16 in can feel very “crisp” on starts and micro control.

AC/DC Inverters on AC (common for aluminum)

Many modern inverters allow a pointed or truncated-point tungsten on AC, which can improve arc focus compared to a large balled tip. If your procedure or machine settings tend to overheat the tip, you may still prefer a more rounded/truncated geometry or a tungsten type that tolerates AC heating well.

• Aluminum on AC (inverter): 2% lanthanated (blue) is commonly successful with a pointed-to-truncated tip. If you prefer a balled tip approach, zirconiated (brown) is a traditional option.
• Higher AC amperage: move up to 3/32 in sooner; keep a controlled flat on the tip to reduce rapid erosion.

Quick Selection Examples

• Example 1 (DC stainless, 60–90 A): 1/16 in 2% lanthanated, sharp point with a small flat.
• Example 2 (AC aluminum, 120–160 A): 3/32 in 2% lanthanated, truncated point (not needle-sharp), consistent taper.
• Example 3 (DC mild steel, 180–220 A): 3/32 in 2% lanthanated, longer taper for focus, slightly larger flat to prevent tip breakdown.

Tip Geometry: Sharp, Truncated, and When to Use Each

Sharp Point (with a small flat)

A sharp point concentrates the arc for precise puddle placement. However, a needle point is fragile and can break down quickly. The practical approach is a sharp taper with a tiny flat at the very end.

• Use for: DCEN on steel/stainless, low-to-medium amperage, tight joints.
• Benefits: Narrow arc, easier directional control.
• Watch for: Tip “mushrooming” if overheated or if the flat is too small for the amperage.

Slightly Blunted / Truncated Point

A truncated point is a tapered tip with a deliberate flat. This improves durability and reduces the chance of the tip shedding particles at higher amperage or on AC.

• Use for: Higher amperage DC, many AC aluminum setups on inverters.
• Benefits: More stable tip shape, less rapid erosion.
• Tradeoff: Slightly wider arc than a very sharp point.

Ball Tip (controlled ball)

A balled tip is traditionally used on AC aluminum, especially on older transformer machines. The ball should be small and centered, not oversized. An oversized ball can wander and can increase the chance of inclusions if the tip sheds material.

• Use for: Traditional AC aluminum procedures, especially with pure or zirconiated tungsten.
• Watch for: Large, off-center ball formation (often a sign of overheating, wrong diameter, or unstable settings).

Safe, Detailed Tungsten Grinding Procedure (Step-by-Step)

Grinding is where arc stability is made or ruined. The goals are: keep tungsten clean, keep the grind marks aligned with the electrode length, and produce a repeatable taper and tip.

Equipment and Setup

• Dedicated abrasive: Use a wheel or belt reserved for tungsten only. Cross-contamination from steel/aluminum grinding can embed foreign material into the tungsten and then into your weld.
• Abrasive choice: Fine grit (commonly ~120–240) helps produce a smooth finish and stable arc. Coarse grit leaves deep grooves that can encourage arc wandering.
• Dust control: Use local extraction or a grinder designed for tungsten. Avoid breathing grinding dust; keep the area clean.
• Handling: Keep tungstens in clean tubes; avoid touching the ground tip with bare, dirty gloves.

Step-by-Step: Grinding a Pointed or Truncated Tip

1. Inspect and cut if needed: If the tip is heavily contaminated (dark, crusty, or has visible embedded metal), cut back to clean material before grinding. Cutting is often faster than trying to grind through deep contamination.

2. Set a consistent taper length: A practical target is a taper length about 2.5–3× the tungsten diameter for general work. Longer tapers can tighten arc focus at lower amperage; shorter tapers can be more durable at higher amperage.

3. Grind lengthwise (not around the circumference): Hold the tungsten so the grind lines run parallel to the electrode length. This helps the arc track straight. Circumferential grind marks can encourage arc wander.

4. Rotate evenly: Rotate the tungsten smoothly while maintaining the same angle. Uneven rotation creates a lopsided point, which can push the arc off-center.

5. Create the point: Grind until the taper is straight and symmetrical. Avoid overheating the tungsten while grinding; excessive heat can cause microcracking and brittleness.

6. Add a small flat (recommended): Lightly touch the very tip to the abrasive to create a tiny flat. This improves durability and reduces the chance of the tip breaking down. The higher the amperage, the slightly larger the flat you typically want.

7. Clean the electrode: Wipe with a clean, lint-free cloth. Keep it away from grinding dust and metal chips.

How to Avoid Inclusions from Tungsten Prep

• Never use a shared grinder: Embedded steel/aluminum particles can transfer into the weld puddle as inclusions.
• Don’t grind a contaminated tip “a little” and go back to welding: If contamination remains, it can shed into the puddle.
• Keep the taper consistent: A lopsided point can cause arc wander, increasing accidental contact with the puddle and creating more contamination events.
• Avoid touching the ground tip: Oils and debris can burn and destabilize the arc.

Recognizing and Fixing a Contaminated Tungsten (Structured Troubleshooting)

Common Symptoms of Contamination

• Arc wandering or unstable arc cone: The arc won’t stay centered where you aim it.
• Hard starts or “spitting” at ignition: Starts feel erratic compared to your normal setup.
• Tip appearance changes: Dark/sooty deposits, a rough or cratered tip, or a shiny blob of base metal fused to the tungsten.
• Unexpected porosity or inclusions in the weld: Especially if it appears right after a visible dip or contact event.
• Audible change: The arc sounds harsher or inconsistent compared to a clean, stable arc.

Immediate Actions When You Suspect Contamination

1. Stop and inspect: Continuing to weld with a contaminated tungsten often makes the problem worse and can seed inclusions.

2. Check how severe it is: Light discoloration with no embedded metal may be removable by regrinding; visible fused metal usually requires cutting back.

3. Decide: regrind vs cut back: If you can still see foreign metal after a few seconds of grinding, cut back further. Don’t “chase” contamination endlessly on the grinder.

Regrind Steps (After a Minor Dip)

1. Remove the tungsten from the torch: This prevents grinding dust from entering the collet/body area and avoids dragging contamination into the torch parts.

2. Grind off the affected area: Use the dedicated tungsten abrasive and grind lengthwise until the surface is uniform and clean.

3. Re-establish taper and tip: Match your normal taper length and add the appropriate flat.

4. Wipe and store cleanly: Keep the tip away from metal dust before reinstalling.

When You Should Cut Back Instead of Just Regrinding

• Visible base metal fused to the tungsten: A shiny lump or smeared metal indicates deeper contamination.
• Cracked or split tip: If the tip shows cracking, it can shed particles.
• Repeated contamination in the same session: If you regrind and the arc is still unstable, cut back farther to ensure you reached clean tungsten.
• Overheated, deformed end: If the end has a large, off-center ball or severe rounding, cutting back can restore symmetry faster.

Quick Diagnostic: What the Tip Shape Is Telling You